Overview:
---------
IPE is a Linux Security Module which takes a complimentary approach to
access control. Whereas existing mandatory access control mechanisms
base their decisions on labels and paths, IPE instead determines
whether or not an operation should be allowed based on immutable
security properties of the system component the operation is being
performed on.
IPE itself does not mandate how the security property should be
evaluated, but relies on an extensible set of external property providers
to evaluate the component. IPE makes its decision based on reference
values for the selected properties, specified in the IPE policy.
The reference values represent the value that the policy writer and the
local system administrator (based on the policy signature) trust for the
system to accomplish the desired tasks.
One such provider is for example dm-verity, which is able to represent
the integrity property of a partition (its immutable state) with a digest.
IPE is compiled under CONFIG_SECURITY_IPE.
Use Cases
---------
IPE works best in fixed-function devices: Devices in which their purpose
is clearly defined and not supposed to be changed (e.g. network firewall
device in a data center, an IoT device, etcetera), where all software and
configuration is built and provisioned by the system owner.
IPE is a long-way off for use in general-purpose computing: the Linux
community as a whole tends to follow a decentralized trust model,
known as the web of trust, which IPE has no support for as of yet.
There are exceptions, such as the case where a Linux distribution
vendor trusts only their own keys, where IPE can successfully be used
to enforce the trust requirement.
Additionally, while most packages are signed today, the files inside
the packages (for instance, the executables), tend to be unsigned. This
makes it difficult to utilize IPE in systems where a package manager is
expected to be functional, without major changes to the package manager
and ecosystem behind it.
DIGLIM[1] is a system that when combined with IPE, could be used to
enable general purpose computing scenarios.
Policy:
-------
IPE policy is a plain-text policy composed of multiple statements
over several lines. There is one required line, at the top of the
policy, indicating the policy name, and the policy version, for
instance:
policy_name=Ex_Policy policy_version=0.0.0
The policy version indicates the current version of the policy. This is
used to prevent roll-back of policy to potentially insecure previous
versions of the policy.
The next portion of IPE policy, are rules. Rules are formed by key=value
pairs, known as properties. IPE rules require two keys: "action", which
determines what IPE does when it encounters a match against the policy
and "op", which determines when that rule should be evaluated.
Thus, a minimal rule is:
op=EXECUTE action=ALLOW
This example rule will allow any execution. A rule is required to have the
"op" property as the first token of a rule, and the "action" as the last
token of the rule.
Additional properties are used to restrict attributes about the files being
evaluated. These properties are intended to be deterministic attributes
that are resident in the kernel.
For example:
op=EXECUTE dmverity_signature=FALSE action=DENY
This rule with property dmverity_signature will deny any file not from
a signed dmverity volume to be executed.
All available properties for IPE described in the documentation patch of
this series.
Rules are evaluated top-to-bottom. As a result, any revocation rules,
or denies should be placed early in the file to ensure that these rules
are evaluated before a rule with "action=ALLOW" is hit.
Any unknown syntax in IPE policy will result in a fatal error to parse
the policy.
Additionally, a DEFAULT operation must be set for all understood
operations within IPE. For policies to remain completely forwards
compatible, it is recommended that users add a "DEFAULT action=ALLOW"
and override the defaults on a per-operation basis.
For more information about the policy syntax, see the kernel
documentation page.
Early Usermode Protection:
--------------------------
IPE can be provided with a policy at startup to load and enforce.
This is intended to be a minimal policy to get the system to a state
where userspace is setup and ready to receive commands, at which
point a policy can be deployed via securityfs. This "boot policy" can be
specified via the config, SECURITY_IPE_BOOT_POLICY, which accepts a path
to a plain-text version of the IPE policy to apply. This policy will be
compiled into the kernel. If not specified, IPE will be disabled until a
policy is deployed and activated through the method above.
Policy Examples:
----------------
Allow all:
policy_name=Allow_All policy_version=0.0.0
DEFAULT action=ALLOW
Allow only initial superblock:
policy_name=Allow_All_Initial_SB policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
Allow any signed dm-verity volume and the initial superblock:
policy_name=AllowSignedAndInitial policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
op=EXECUTE dmverity_signature=TRUE action=ALLOW
Prohibit execution from a specific dm-verity volume, while allowing
all signed volumes and the initial superblock:
policy_name=ProhibitSingleVolume policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
op=EXECUTE dmverity_signature=TRUE action=ALLOW
Allow only a specific dm-verity volume:
policy_name=AllowSpecific policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=ALLOW
Allow any signed fs-verity file
policy_name=AllowSignedFSVerity policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE fsverity_signature=TRUE action=ALLOW
Deny a specific fs-verity file:
policy_name=ProhibitSpecificFSVF policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE fsverity_digest=sha256:fd88f2b8824e197f850bf4c5109bea5cf0ee38104f710843bb72da796ba5af9e action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
op=EXECUTE dmverity_signature=TRUE action=ALLOW
Deploying Policies:
-------------------
First sign a plain text policy, with a certificate that is present in
the SYSTEM_TRUSTED_KEYRING of your test machine. Through openssl, the
signing can be done via:
openssl smime -sign -in "$MY_POLICY" -signer "$MY_CERTIFICATE" \
-inkey "$MY_PRIVATE_KEY" -outform der -noattr -nodetach \
-out "$MY_POLICY.p7s"
Then, simply cat the file into the IPE's "new_policy" securityfs node:
cat "$MY_POLICY.p7s" > /sys/kernel/security/ipe/new_policy
The policy should now be present under the policies/ subdirectory, under
its "policy_name" attribute.
The policy is now present in the kernel and can be marked as active,
via the securityfs node:
echo 1 > "/sys/kernel/security/ipe/$MY_POLICY_NAME/active"
This will now mark the policy as active and the system will be enforcing
$MY_POLICY_NAME.
There is one requirement when marking a policy as active, the policy_version
attribute must either increase, or remain the same as the currently running
policy.
Policies can be updated via:
cat "$MY_UPDATED_POLICY.p7s" > \
"/sys/kernel/security/ipe/policies/$MY_POLICY_NAME/update"
Additionally, policies can be deleted via the "delete" securityfs
node. Simply write "1" to the corresponding node in the policy folder:
echo 1 > "/sys/kernel/security/ipe/policies/$MY_POLICY_NAME/delete"
There is only one requirement to delete policies, the policy being
deleted must not be the active policy.
NOTE: Any securityfs write to IPE's nodes will require CAP_MAC_ADMIN.
Integrations:
-------------
This patch series adds support for fsverity via digest and signature
(fsverity_signature and fsverity_digest), dm-verity by digest and
signature (dmverity_signature and dmverity_roothash), and trust for
the initramfs (boot_verified).
Please see the documentation patch for more information about the
integrations available.
Testing:
--------
KUnit Tests are available. Recommended kunitconfig:
CONFIG_KUNIT=y
CONFIG_SECURITY=y
CONFIG_SECURITYFS=y
CONFIG_PKCS7_MESSAGE_PARSER=y
CONFIG_SYSTEM_DATA_VERIFICATION=y
CONFIG_FS_VERITY=y
CONFIG_FS_VERITY_BUILTIN_SIGNATURES=y
CONFIG_BLOCK=y
CONFIG_MD=y
CONFIG_BLK_DEV_DM=y
CONFIG_DM_VERITY=y
CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG=y
CONFIG_NET=y
CONFIG_AUDIT=y
CONFIG_AUDITSYSCALL=y
CONFIG_SECURITY_IPE=y
CONFIG_IPE_PROP_DM_VERITY=y
CONFIG_IPE_PROP_FS_VERITY=y
CONFIG_SECURITY_IPE_KUNIT_TEST=y
Simply run:
make ARCH=um mrproper
./tools/testing/kunit/kunit.py run --kunitconfig <path/to/config>
And the tests will execute and report the result. For more indepth testing,
it will require you to create and mount a dm-verity volume or fs-verity
enabled file.
Documentation:
--------------
There is both documentation available on github at
https://microsoft.github.io/ipe, and Documentation in this patch series,
to be added in-tree.
Known Gaps:
-----------
IPE has two known gaps:
1. IPE cannot verify the integrity of anonymous executable memory, such as
the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code.
Unfortunately, as this is dynamically generated code, there is no way
for IPE to ensure the integrity of this code to form a trust basis. In all
cases, the return result for these operations will be whatever the admin
configures the DEFAULT action for "EXECUTE".
2. IPE cannot verify the integrity of interpreted languages' programs when
these scripts invoked via ``<interpreter> <file>``. This is because the
way interpreters execute these files, the scripts themselves are not
evaluated as executable code through one of IPE's hooks. Interpreters
can be enlightened to the usage of IPE by trying to mmap a file into
executable memory (+X), after opening the file and responding to the
error code appropriately. This also applies to included files, or high
value files, such as configuration files of critical system components.
Appendix:
---------
A. IPE Github Repository: https://github.com/microsoft/ipe
B. IPE Users' Guide: Documentation/admin-guide/LSM/ipe.rst
References:
-----------
1: https://lore.kernel.org/bpf/[email protected]/
FAQ:
----
Q: What is the difference between IMA and IPE?
A: See the documentation patch for more on this topic.
Previous Postings
-----------------
v1: https://lore.kernel.org/all/[email protected]/
v2: https://lore.kernel.org/all/[email protected]/
v3: https://lore.kernel.org/all/[email protected]/
v4: https://lore.kernel.org/all/[email protected]/
v5: https://lore.kernel.org/all/[email protected]/
v6: https://lore.kernel.org/all/[email protected]/
v7: https://lore.kernel.org/all/1634151995-16266-1-git-send-email-deven.desai@linux.microsoft.com/
v8: https://lore.kernel.org/all/1654714889-26728-1-git-send-email-deven.desai@linux.microsoft.com/
v9: https://lore.kernel.org/lkml/[email protected]/
v10: https://lore.kernel.org/lkml/[email protected]/
Changelog:
----------
v2:
Split the second patch of the previous series into two.
Minor corrections in the cover-letter and documentation
comments regarding CAP_MAC_ADMIN checks in IPE.
v3:
Address various comments by Jann Horn. Highlights:
Switch various audit allocators to GFP_KERNEL.
Utilize rcu_access_pointer() in various locations.
Strip out the caching system for properties
Strip comments from headers
Move functions around in patches
Remove kernel command line parameters
Reconcile the race condition on the delete node for policy by
expanding the policy critical section.
Address a few comments by Jonathan Corbet around the documentation
pages for IPE.
Fix an issue with the initialization of IPE policy with a "-0"
version, caused by not initializing the hlist entries before
freeing.
v4:
Address a concern around IPE's behavior with unknown syntax.
Specifically, make any unknown syntax a fatal error instead of a
warning, as suggested by Mickaël Salaün.
Introduce a new securityfs node, $securityfs/ipe/property_config,
which provides a listing of what properties are enabled by the
kernel and their versions. This allows usermode to predict what
policies should be allowed.
Strip some comments from c files that I missed.
Clarify some documentation comments around 'boot_verified'.
While this currently does not functionally change the property
itself, the distinction is important when IPE can enforce verified
reads. Additionally, 'KERNEL_READ' was omitted from the documentation.
This has been corrected.
Change SecurityFS and SHA1 to a reverse dependency.
Update the cover-letter with the updated behavior of unknown syntax.
Remove all sysctls, making an equivalent function in securityfs.
Rework the active/delete mechanism to be a node under the policy in
$securityfs/ipe/policies.
The kernel command line parameters ipe.enforce and ipe.success_audit
have returned as this functionality is no longer exposed through
sysfs.
v5:
Correct some grammatical errors reported by Randy Dunlap.
Fix some warnings reported by kernel test bot.
Change convention around security_bdev_setsecurity. -ENOSYS
is now expected if an LSM does not implement a particular @name,
as suggested by Casey Schaufler.
Minor string corrections related to the move from sysfs to securityfs
Correct a spelling of an #ifdef for the permissive argument.
Add the kernel parameters re-added to the documentation.
Fix a minor bug where the mode being audited on permissive switch
was the original mode, not the mode being swapped to.
Cleanup doc comments, fix some whitespace alignment issues.
v6:
Change if statement condition in security_bdev_setsecurity to be
more concise, as suggested by Casey Schaufler and Al Viro
Drop the 6th patch in the series, "dm-verity move signature check..."
due to numerous issues, and it ultimately providing no real value.
Fix the patch tree - the previous iteration appears to have been in a
torn state (patches 8+9 were merged). This has since been corrected.
v7:
* Reword cover letter to more accurate convey IPE's purpose
and latest updates.
* Refactor series to:
1. Support a context structure, enabling:
1. Easier Testing via KUNIT
2. A better architecture for future designs
2. Make parser code cleaner
* Move patch 01/12 to [14/16] of the series
* Split up patch 02/12 into four parts:
1. context creation [01/16]
2. audit [07/16]
3. evaluation loop [03/16]
4. access control hooks [05/16]
5. permissive mode [08/16]
* Split up patch 03/12 into two parts:
1. parser [02/16]
2. userspace interface [04/16]
* Reword and refactor patch 04/12 to [09/16]
* Squash patch 05/12, 07/12, 09/12 to [10/16]
* Squash patch 08/12, 10/12 to [11/16]
* Change audit records to MAC region (14XX) from Integrity region (18XX)
* Add FSVerity Support
* Interface changes:
1. "raw" was renamed to "pkcs7" and made read only
2. "raw"'s write functionality (update a policy) moved to "update"
3. introduced "version", "policy_name" nodes.
4. "content" renamed to "policy"
5. The boot policy can now be updated like any other policy.
* Add additional developer-level documentation
* Update admin-guide docs to reflect changes.
* Kunit tests
* Dropped CONFIG_SECURITY_IPE_PERMISSIVE_SWITCH - functionality can
easily come later with a small patch.
* Use partition0 for block_device for dm-verity patch
v8:
* Add changelog information to individual commits
* A large number of changes to the audit patch.
* split fs/ & security/ changes to two separate patches.
* split block/, security/ & drivers/md/ changes to separate patches.
* Add some historical context to what lead to the creation of IPE
in the documentation patch.
* Cover-letter changes suggested by Roberto Sassu.
v9:
* Rewrite IPE parser to use kernel match_table parser.
* Adapt existing IPE properties to the new parser.
* Remove ipe_context, quote policy syntax, kernel_read for simplicity.
* Add new function in the security file system to delete IPE policy.
* Make IPE audit builtin and change several audit formats.
* Make boot_verified property builtin
v10:
* Address various code style/format issues
* Correct the rcu locking for active policy
* Fix memleak bugs in the parser, optimize the parser per upstream feedback
* Adding new audit events for IPE and update audit formats
* Make the dmverity property auto selected
* Adding more context in the commit messages
v11:
* Address various code style/format issues
* Add finalize hook to device mapper
* move the security hook for dm-verity to the new device mapper finalize hook
Deven Bowers (14):
security: add ipe lsm
ipe: add policy parser
ipe: add evaluation loop
ipe: add LSM hooks on execution and kernel read
ipe: introduce 'boot_verified' as a trust provider
ipe: add userspace interface
uapi|audit|ipe: add ipe auditing support
ipe: add permissive toggle
block|security: add LSM blob to block_device
dm verity: consume root hash digest and signature data via LSM hook
ipe: add support for dm-verity as a trust provider
scripts: add boot policy generation program
ipe: kunit test for parser
documentation: add ipe documentation
Fan Wu (5):
security: add new securityfs delete function
dm verity: set DM_TARGET_SINGLETON feature flag
dm: add finalize hook to target_type
fsverity: consume builtin signature via LSM hook
ipe: enable support for fs-verity as a trust provider
Documentation/admin-guide/LSM/index.rst | 1 +
Documentation/admin-guide/LSM/ipe.rst | 752 ++++++++++++++++++
.../admin-guide/kernel-parameters.txt | 12 +
Documentation/security/index.rst | 1 +
Documentation/security/ipe.rst | 420 ++++++++++
MAINTAINERS | 10 +
block/bdev.c | 7 +
drivers/md/dm-verity-target.c | 73 +-
drivers/md/dm-verity.h | 6 +
drivers/md/dm.c | 12 +
fs/verity/fsverity_private.h | 2 +-
fs/verity/open.c | 26 +-
include/linux/blk_types.h | 3 +
include/linux/device-mapper.h | 7 +
include/linux/dm-verity.h | 19 +
include/linux/fsverity.h | 2 +
include/linux/lsm_hook_defs.h | 5 +
include/linux/lsm_hooks.h | 1 +
include/linux/security.h | 23 +
include/uapi/linux/audit.h | 3 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 1 +
scripts/ipe/polgen/Makefile | 6 +
scripts/ipe/polgen/polgen.c | 145 ++++
security/Kconfig | 11 +-
security/Makefile | 1 +
security/inode.c | 25 +
security/ipe/.gitignore | 1 +
security/ipe/Kconfig | 75 ++
security/ipe/Makefile | 31 +
security/ipe/audit.c | 267 +++++++
security/ipe/audit.h | 19 +
security/ipe/digest.c | 142 ++++
security/ipe/digest.h | 26 +
security/ipe/eval.c | 419 ++++++++++
security/ipe/eval.h | 61 ++
security/ipe/fs.c | 247 ++++++
security/ipe/fs.h | 16 +
security/ipe/hooks.c | 276 +++++++
security/ipe/hooks.h | 42 +
security/ipe/ipe.c | 85 ++
security/ipe/ipe.h | 25 +
security/ipe/policy.c | 218 +++++
security/ipe/policy.h | 100 +++
security/ipe/policy_fs.c | 481 +++++++++++
security/ipe/policy_parser.c | 550 +++++++++++++
security/ipe/policy_parser.h | 11 +
security/ipe/policy_tests.c | 294 +++++++
security/security.c | 99 +++
50 files changed, 5054 insertions(+), 8 deletions(-)
create mode 100644 Documentation/admin-guide/LSM/ipe.rst
create mode 100644 Documentation/security/ipe.rst
create mode 100644 include/linux/dm-verity.h
create mode 100644 scripts/ipe/Makefile
create mode 100644 scripts/ipe/polgen/.gitignore
create mode 100644 scripts/ipe/polgen/Makefile
create mode 100644 scripts/ipe/polgen/polgen.c
create mode 100644 security/ipe/.gitignore
create mode 100644 security/ipe/Kconfig
create mode 100644 security/ipe/Makefile
create mode 100644 security/ipe/audit.c
create mode 100644 security/ipe/audit.h
create mode 100644 security/ipe/digest.c
create mode 100644 security/ipe/digest.h
create mode 100644 security/ipe/eval.c
create mode 100644 security/ipe/eval.h
create mode 100644 security/ipe/fs.c
create mode 100644 security/ipe/fs.h
create mode 100644 security/ipe/hooks.c
create mode 100644 security/ipe/hooks.h
create mode 100644 security/ipe/ipe.c
create mode 100644 security/ipe/ipe.h
create mode 100644 security/ipe/policy.c
create mode 100644 security/ipe/policy.h
create mode 100644 security/ipe/policy_fs.c
create mode 100644 security/ipe/policy_parser.c
create mode 100644 security/ipe/policy_parser.h
create mode 100644 security/ipe/policy_tests.c
--
2.25.1
The device-mapper has a flag to mark targets as singleton, which is a
required flag for immutable targets. Without this flag, multiple
dm-verity targets can be added to a mapped device, which has no
practical use cases and will let dm_table_get_immutable_target return
NULL. This patch adds the missing flag, restricting only one
dm-verity target per mapped device.
Signed-off-by: Fan Wu <[email protected]>
---
v1-v10:
+ Not present
---
drivers/md/dm-verity-target.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 26adcfea0302..80673b66c194 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1503,7 +1503,7 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
static struct target_type verity_target = {
.name = "verity",
- .features = DM_TARGET_IMMUTABLE,
+ .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
.version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = verity_ctr,
--
2.25.1
From: Deven Bowers <[email protected]>
Enables an IPE policy to be enforced from kernel start, enabling access
control based on trust from kernel startup. This is accomplished by
transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a
c-string literal that is parsed at kernel startup as an unsigned policy.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ No Changes
v3:
+ No Changes
v4:
+ No Changes
v5:
+ No Changes
v6:
+ No Changes
v7:
+ Move from 01/11 to 14/16
+ Don't return errno directly.
+ Make output of script more user-friendly
+ Add escaping for tab and '?'
+ Mark argv pointer const
+ Invert return code check in the boot policy parsing code path.
v8:
+ No significant changes.
v9:
+ No changes
v10:
+ Update the init part code for rcu changes in the eval loop patch
v11:
+ Fix code style issues
---
MAINTAINERS | 1 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 1 +
scripts/ipe/polgen/Makefile | 6 ++
scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
security/ipe/.gitignore | 1 +
security/ipe/Kconfig | 10 +++
security/ipe/Makefile | 11 +++
security/ipe/fs.c | 8 ++
security/ipe/ipe.c | 12 +++
11 files changed, 198 insertions(+)
create mode 100644 scripts/ipe/Makefile
create mode 100644 scripts/ipe/polgen/.gitignore
create mode 100644 scripts/ipe/polgen/Makefile
create mode 100644 scripts/ipe/polgen/polgen.c
create mode 100644 security/ipe/.gitignore
diff --git a/MAINTAINERS b/MAINTAINERS
index b898f2f8f9c4..18b1aeea6306 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10394,6 +10394,7 @@ M: Fan Wu <[email protected]>
L: [email protected]
S: Supported
T: git https://github.com/microsoft/ipe.git
+F: scripts/ipe/
F: security/ipe/
INTEL 810/815 FRAMEBUFFER DRIVER
diff --git a/scripts/Makefile b/scripts/Makefile
index 576cf64be667..1dbaf3a49aef 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -50,6 +50,7 @@ targets += module.lds
subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
subdir-$(CONFIG_MODVERSIONS) += genksyms
subdir-$(CONFIG_SECURITY_SELINUX) += selinux
+subdir-$(CONFIG_SECURITY_IPE) += ipe
# Let clean descend into subdirs
subdir- += basic dtc gdb kconfig mod
diff --git a/scripts/ipe/Makefile b/scripts/ipe/Makefile
new file mode 100644
index 000000000000..e87553fbb8d6
--- /dev/null
+++ b/scripts/ipe/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+subdir-y := polgen
diff --git a/scripts/ipe/polgen/.gitignore b/scripts/ipe/polgen/.gitignore
new file mode 100644
index 000000000000..80f32f25d200
--- /dev/null
+++ b/scripts/ipe/polgen/.gitignore
@@ -0,0 +1 @@
+polgen
diff --git a/scripts/ipe/polgen/Makefile b/scripts/ipe/polgen/Makefile
new file mode 100644
index 000000000000..066060c22b4a
--- /dev/null
+++ b/scripts/ipe/polgen/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+hostprogs-always-y := polgen
+HOST_EXTRACFLAGS += \
+ -I$(srctree)/include \
+ -I$(srctree)/include/uapi \
+
diff --git a/scripts/ipe/polgen/polgen.c b/scripts/ipe/polgen/polgen.c
new file mode 100644
index 000000000000..40b6fe07f47b
--- /dev/null
+++ b/scripts/ipe/polgen/polgen.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+
+static void usage(const char *const name)
+{
+ printf("Usage: %s OutputFile (PolicyFile)\n", name);
+ exit(EINVAL);
+}
+
+static int policy_to_buffer(const char *pathname, char **buffer, size_t *size)
+{
+ int rc = 0;
+ FILE *fd;
+ char *lbuf;
+ size_t fsize;
+ size_t read;
+
+ fd = fopen(pathname, "r");
+ if (!fd) {
+ rc = errno;
+ goto out;
+ }
+
+ fseek(fd, 0, SEEK_END);
+ fsize = ftell(fd);
+ rewind(fd);
+
+ lbuf = malloc(fsize);
+ if (!lbuf) {
+ rc = ENOMEM;
+ goto out_close;
+ }
+
+ read = fread((void *)lbuf, sizeof(*lbuf), fsize, fd);
+ if (read != fsize) {
+ rc = -1;
+ goto out_free;
+ }
+
+ *buffer = lbuf;
+ *size = fsize;
+ fclose(fd);
+
+ return rc;
+
+out_free:
+ free(lbuf);
+out_close:
+ fclose(fd);
+out:
+ return rc;
+}
+
+static int write_boot_policy(const char *pathname, const char *buf, size_t size)
+{
+ int rc = 0;
+ FILE *fd;
+ size_t i;
+
+ fd = fopen(pathname, "w");
+ if (!fd) {
+ rc = errno;
+ goto err;
+ }
+
+ fprintf(fd, "/* This file is automatically generated.");
+ fprintf(fd, " Do not edit. */\n");
+ fprintf(fd, "#include <linux/stddef.h>\n");
+ fprintf(fd, "\nextern const char *const ipe_boot_policy;\n\n");
+ fprintf(fd, "const char *const ipe_boot_policy =\n");
+
+ if (!buf || size == 0) {
+ fprintf(fd, "\tNULL;\n");
+ fclose(fd);
+ return 0;
+ }
+
+ fprintf(fd, "\t\"");
+
+ for (i = 0; i < size; ++i) {
+ switch (buf[i]) {
+ case '"':
+ fprintf(fd, "\\\"");
+ break;
+ case '\'':
+ fprintf(fd, "'");
+ break;
+ case '\n':
+ fprintf(fd, "\\n\"\n\t\"");
+ break;
+ case '\\':
+ fprintf(fd, "\\\\");
+ break;
+ case '\t':
+ fprintf(fd, "\\t");
+ break;
+ case '\?':
+ fprintf(fd, "\\?");
+ break;
+ default:
+ fprintf(fd, "%c", buf[i]);
+ }
+ }
+ fprintf(fd, "\";\n");
+ fclose(fd);
+
+ return 0;
+
+err:
+ if (fd)
+ fclose(fd);
+ return rc;
+}
+
+int main(int argc, const char *const argv[])
+{
+ int rc = 0;
+ size_t len = 0;
+ char *policy = NULL;
+
+ if (argc < 2)
+ usage(argv[0]);
+
+ if (argc > 2) {
+ rc = policy_to_buffer(argv[2], &policy, &len);
+ if (rc != 0)
+ goto cleanup;
+ }
+
+ rc = write_boot_policy(argv[1], policy, len);
+cleanup:
+ if (policy)
+ free(policy);
+ if (rc != 0)
+ perror("An error occurred during policy conversion: ");
+ return rc;
+}
diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore
new file mode 100644
index 000000000000..eca22ad5ed22
--- /dev/null
+++ b/security/ipe/.gitignore
@@ -0,0 +1 @@
+boot-policy.c
\ No newline at end of file
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 9dd5c4769d79..a6c5d48dd0a3 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -18,6 +18,16 @@ menuconfig SECURITY_IPE
If unsure, answer N.
if SECURITY_IPE
+config IPE_BOOT_POLICY
+ string "Integrity policy to apply on system startup"
+ help
+ This option specifies a filepath to a IPE policy that is compiled
+ into the kernel. This policy will be enforced until a policy update
+ is deployed via the $securityfs/ipe/policies/$policy_name/active
+ interface.
+
+ If unsure, leave blank.
+
menu "IPE Trust Providers"
config IPE_PROP_DM_VERITY
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 66de53687d11..ce23101b66ba 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -5,7 +5,16 @@
# Makefile for building the IPE module as part of the kernel tree.
#
+quiet_cmd_polgen = IPE_POL $(2)
+ cmd_polgen = scripts/ipe/polgen/polgen security/ipe/boot-policy.c $(2)
+
+targets += boot-policy.c
+
+$(obj)/boot-policy.c: scripts/ipe/polgen/polgen $(CONFIG_IPE_BOOT_POLICY) FORCE
+ $(call if_changed,polgen,$(CONFIG_IPE_BOOT_POLICY))
+
obj-$(CONFIG_SECURITY_IPE) += \
+ boot-policy.o \
digest.o \
eval.o \
hooks.o \
@@ -15,3 +24,5 @@ obj-$(CONFIG_SECURITY_IPE) += \
policy_fs.o \
policy_parser.o \
audit.o \
+
+clean-files := boot-policy.c \
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index 0a1838432bd0..58584c5f3ee4 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -190,6 +190,7 @@ static const struct file_operations enforce_fops = {
static int __init ipe_init_securityfs(void)
{
int rc = 0;
+ struct ipe_policy *ap;
if (!ipe_enabled)
return -EOPNOTSUPP;
@@ -220,6 +221,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}
+ ap = rcu_access_pointer(ipe_active_policy);
+ if (ap) {
+ rc = ipe_new_policyfs_node(ap);
+ if (rc)
+ goto err;
+ }
+
np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops);
if (IS_ERR(np)) {
rc = PTR_ERR(np);
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index e789f1db6f66..3d672dd57b32 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -7,6 +7,7 @@
#include "hooks.h"
#include "eval.h"
+extern const char *const ipe_boot_policy;
bool ipe_enabled;
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
@@ -60,9 +61,20 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
*/
static int __init ipe_init(void)
{
+ struct ipe_policy *p = NULL;
+
security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), "ipe");
ipe_enabled = true;
+ if (ipe_boot_policy) {
+ p = ipe_new_policy(ipe_boot_policy, strlen(ipe_boot_policy),
+ NULL, 0);
+ if (IS_ERR(p))
+ return PTR_ERR(p);
+
+ rcu_assign_pointer(ipe_active_policy, p);
+ }
+
return 0;
}
--
2.25.1
From: Deven Bowers <[email protected]>
Allows author of IPE policy to indicate trust for a singular dm-verity
volume, identified by roothash, through "dmverity_roothash" and all
signed dm-verity volumes, through "dmverity_signature".
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ No Changes
v3:
+ No changes
v4:
+ No changes
v5:
+ No changes
v6:
+ Fix an improper cleanup that can result in
a leak
v7:
+ Squash patch 08/12, 10/12 to [11/16]
v8:
+ Undo squash of 08/12, 10/12 - separating drivers/md/ from security/
& block/
+ Use common-audit function for dmverity_signature.
+ Change implementation for storing the dm-verity digest to use the
newly introduced dm_verity_digest structure introduced in patch
14/20.
v9:
+ Adapt to the new parser
v10:
+ Select the Kconfig when all dependencies are enabled
v11:
+ No changes
---
security/ipe/Kconfig | 18 +++++
security/ipe/Makefile | 1 +
security/ipe/audit.c | 31 +++++++-
security/ipe/digest.c | 142 +++++++++++++++++++++++++++++++++++
security/ipe/digest.h | 26 +++++++
security/ipe/eval.c | 101 ++++++++++++++++++++++++-
security/ipe/eval.h | 13 ++++
security/ipe/hooks.c | 51 +++++++++++++
security/ipe/hooks.h | 8 ++
security/ipe/ipe.c | 15 ++++
security/ipe/ipe.h | 4 +
security/ipe/policy.h | 3 +
security/ipe/policy_parser.c | 24 +++++-
13 files changed, 433 insertions(+), 4 deletions(-)
create mode 100644 security/ipe/digest.c
create mode 100644 security/ipe/digest.h
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index ac4d558e69d5..7afb1ce0cb99 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -8,6 +8,7 @@ menuconfig SECURITY_IPE
depends on SECURITY && SECURITYFS && AUDIT && AUDITSYSCALL
select PKCS7_MESSAGE_PARSER
select SYSTEM_DATA_VERIFICATION
+ select IPE_PROP_DM_VERITY if DM_VERITY && DM_VERITY_VERIFY_ROOTHASH_SIG
help
This option enables the Integrity Policy Enforcement LSM
allowing users to define a policy to enforce a trust-based access
@@ -15,3 +16,20 @@ menuconfig SECURITY_IPE
admins to reconfigure trust requirements on the fly.
If unsure, answer N.
+
+if SECURITY_IPE
+menu "IPE Trust Providers"
+
+config IPE_PROP_DM_VERITY
+ bool "Enable support for dm-verity volumes"
+ depends on DM_VERITY && DM_VERITY_VERIFY_ROOTHASH_SIG
+ help
+ This option enables the properties 'dmverity_signature' and
+ 'dmverity_roothash' in IPE policy. These properties evaluates
+ to TRUE when a file is evaluated against a dm-verity volume
+ that was mounted with a signed root-hash or the volume's
+ root hash matches the supplied value in the policy.
+
+endmenu
+
+endif
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 2279eaa3cea3..66de53687d11 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -6,6 +6,7 @@
#
obj-$(CONFIG_SECURITY_IPE) += \
+ digest.o \
eval.o \
hooks.o \
fs.o \
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index 0dd5f10c318f..b5c58655ac74 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -13,6 +13,7 @@
#include "hooks.h"
#include "policy.h"
#include "audit.h"
+#include "digest.h"
#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
@@ -40,8 +41,29 @@ static const char *const audit_op_names[__IPE_OP_MAX] = {
static const char *const audit_prop_names[__IPE_PROP_MAX] = {
"boot_verified=FALSE",
"boot_verified=TRUE",
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ "dmverity_roothash=",
+ "dmverity_signature=FALSE",
+ "dmverity_signature=TRUE",
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+/**
+ * audit_dmv_roothash - audit a roothash of a dmverity volume.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @r: Supplies a pointer to the digest structure.
+ */
+static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
+{
+ ipe_digest_audit(ab, rh);
+}
+#else
+static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
+{
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
/**
* audit_rule - audit an IPE policy rule approximation.
* @ab: Supplies a pointer to the audit_buffer to append to.
@@ -53,8 +75,13 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
- list_for_each_entry(ptr, &r->props, next)
- audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
+ list_for_each_entry(ptr, &r->props, next) {
+ audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
+ if (ptr->type == IPE_PROP_DMV_ROOTHASH)
+ audit_dmv_roothash(ab, ptr->value);
+
+ audit_log_format(ab, " ");
+ }
audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
}
diff --git a/security/ipe/digest.c b/security/ipe/digest.c
new file mode 100644
index 000000000000..7a42ca71880c
--- /dev/null
+++ b/security/ipe/digest.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "digest.h"
+
+/**
+ * ipe_digest_parse - parse a digest in IPE's policy.
+ * @valstr: Supplies the string parsed from the policy.
+ * @value: Supplies a pointer to be populated with the result.
+ *
+ * Digests in IPE are defined in a standard way:
+ * <alg_name>:<hex>
+ *
+ * Use this function to create a property to parse the digest
+ * consistently. The parsed digest will be saved in @value in IPE's
+ * policy.
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Error
+ */
+int ipe_digest_parse(const char *valstr, void **value)
+{
+ char *sep, *raw_digest;
+ size_t raw_digest_len;
+ int rc = 0;
+ u8 *digest = NULL;
+ struct digest_info *info = NULL;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ sep = strchr(valstr, ':');
+ if (!sep) {
+ rc = -EBADMSG;
+ goto err;
+ }
+
+ info->alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
+ if (!info->alg) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ raw_digest = sep + 1;
+ raw_digest_len = strlen(raw_digest);
+ info->raw_digest = kstrndup(raw_digest, raw_digest_len, GFP_KERNEL);
+ if (!info->raw_digest) {
+ rc = -ENOMEM;
+ goto err_free_alg;
+ }
+
+ info->digest_len = (raw_digest_len + 1) / 2;
+ digest = kzalloc(info->digest_len, GFP_KERNEL);
+ if (!digest) {
+ rc = -ENOMEM;
+ goto err_free_raw;
+ }
+
+ rc = hex2bin(digest, raw_digest, info->digest_len);
+ if (rc < 0) {
+ rc = -EINVAL;
+ goto err_free_raw;
+ }
+
+ info->digest = digest;
+ *value = info;
+ return 0;
+
+err_free_raw:
+ kfree(info->raw_digest);
+err_free_alg:
+ kfree(info->alg);
+err:
+ kfree(digest);
+ kfree(info);
+ return rc;
+}
+
+/**
+ * ipe_digest_eval - evaluate an IPE digest against another digest.
+ * @expect: Supplies the policy-provided digest value.
+ * @digest: Supplies the digest to compare against the policy digest value.
+ * @digest_len: The length of @digest.
+ * @alg: Supplies the name of the algorithm used to calculated @digest.
+ *
+ * Return:
+ * * true - digests match
+ * * false - digests do not match
+ */
+bool ipe_digest_eval(const void *expect, const u8 *digest, size_t digest_len,
+ const char *alg)
+{
+ const struct digest_info *info = (struct digest_info *)expect;
+
+ return (digest_len == info->digest_len) && !strcmp(alg, info->alg) &&
+ (!memcmp(info->digest, digest, info->digest_len));
+}
+
+/**
+ * ipe_digest_free - free an IPE digest.
+ * @value: Supplies a pointer the policy-provided digest value to free.
+ */
+void ipe_digest_free(void **value)
+{
+ struct digest_info *info = (struct digest_info *)(*value);
+
+ if (IS_ERR_OR_NULL(info))
+ return;
+
+ kfree(info->alg);
+ kfree(info->raw_digest);
+ kfree(info->digest);
+ kfree(info);
+}
+
+/**
+ * ipe_digest_audit - audit a digest that was sourced from IPE's policy.
+ * @ab: Supplies the audit_buffer to append the formatted result.
+ * @val: Supplies a pointer to source the audit record from.
+ *
+ * Digests in IPE are defined in a standard way:
+ * <alg_name>:<hex>
+ *
+ * Use this function to create a property to audit the digest
+ * consistently.
+ *
+ * Return:
+ * 0 - OK
+ * !0 - Error
+ */
+void ipe_digest_audit(struct audit_buffer *ab, const void *val)
+{
+ const struct digest_info *info = (struct digest_info *)val;
+
+ audit_log_untrustedstring(ab, info->alg);
+ audit_log_format(ab, ":");
+ audit_log_untrustedstring(ab, info->raw_digest);
+}
diff --git a/security/ipe/digest.h b/security/ipe/digest.h
new file mode 100644
index 000000000000..e40ba4b2799e
--- /dev/null
+++ b/security/ipe/digest.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_DIGEST_H
+#define _IPE_DIGEST_H
+
+#include "policy.h"
+#include <linux/types.h>
+#include <linux/audit.h>
+
+struct digest_info {
+ const char *alg;
+ const char *raw_digest;
+ const u8 *digest;
+ size_t digest_len;
+};
+
+int ipe_digest_parse(const char *valstr, void **value);
+void ipe_digest_free(void **value);
+void ipe_digest_audit(struct audit_buffer *ab, const void *val);
+bool ipe_digest_eval(const void *expect, const u8 *digest, size_t digest_len,
+ const char *alg);
+
+#endif /* _IPE_DIGEST_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 78c54ff1fdd3..82ad48d7aa3d 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -16,10 +16,12 @@
#include "eval.h"
#include "policy.h"
#include "audit.h"
+#include "digest.h"
struct ipe_policy __rcu *ipe_active_policy;
bool success_audit;
bool enforce = true;
+#define INO_BLOCK_DEV(ino) ((ino)->i_sb->s_bdev)
static const struct super_block *pinned_sb;
static DEFINE_SPINLOCK(pin_lock);
@@ -59,6 +61,23 @@ static bool from_pinned(const struct super_block *sb)
return rv;
}
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+/**
+ * build_ipe_bdev_ctx - Build ipe_bdev field of an evaluation context.
+ * @ctx: Supplies a pointer to the context to be populdated.
+ * @ino: Supplies the inode struct of the file triggered IPE event.
+ */
+static void build_ipe_bdev_ctx(struct ipe_eval_ctx *ctx, const struct inode *const ino)
+{
+ if (INO_BLOCK_DEV(ino))
+ ctx->ipe_bdev = ipe_bdev(INO_BLOCK_DEV(ino));
+}
+#else
+static void build_ipe_bdev_ctx(struct ipe_eval_ctx *ctx, const struct inode *const ino)
+{
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
/**
* build_eval_ctx - Build an evaluation context.
* @ctx: Supplies a pointer to the context to be populdated.
@@ -69,15 +88,89 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
const struct file *file,
enum ipe_op_type op)
{
+ struct inode *ino = NULL;
+
if (op == IPE_OP_EXEC && file)
pin_sb(FILE_SUPERBLOCK(file));
ctx->file = file;
ctx->op = op;
- if (file)
+ if (file) {
ctx->from_init_sb = from_pinned(FILE_SUPERBLOCK(file));
+ ino = d_real_inode(file->f_path.dentry);
+ build_ipe_bdev_ctx(ctx, ino);
+ }
+}
+
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+/**
+ * evaluate_dmv_roothash - Evaluate @ctx against a dmv roothash property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_dmv_roothash(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return !!ctx->ipe_bdev &&
+ ipe_digest_eval(p->value,
+ ctx->ipe_bdev->digest,
+ ctx->ipe_bdev->digest_len,
+ ctx->ipe_bdev->digest_algo);
+}
+
+/**
+ * evaluate_dmv_sig_false: Analyze @ctx against a dmv sig false property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_dmv_sig_false(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return !ctx->ipe_bdev || (!ctx->ipe_bdev->dm_verity_signed);
+}
+
+/**
+ * evaluate_dmv_sig_true: Analyze @ctx against a dmv sig true property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return ctx->ipe_bdev && (!!ctx->ipe_bdev->dm_verity_signed);
+}
+#else
+static bool evaluate_dmv_roothash(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+
+static bool evaluate_dmv_sig_false(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+
+static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
/**
* evaluate_property - Analyze @ctx against a property.
@@ -96,6 +189,12 @@ static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
return !ctx->from_init_sb;
case IPE_PROP_BOOT_VERIFIED_TRUE:
return ctx->from_init_sb;
+ case IPE_PROP_DMV_ROOTHASH:
+ return evaluate_dmv_roothash(ctx, p);
+ case IPE_PROP_DMV_SIG_FALSE:
+ return evaluate_dmv_sig_false(ctx, p);
+ case IPE_PROP_DMV_SIG_TRUE:
+ return evaluate_dmv_sig_true(ctx, p);
default:
return false;
}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 3f7f71452618..e575e94804a4 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -17,11 +17,24 @@ extern struct ipe_policy __rcu *ipe_active_policy;
extern bool success_audit;
extern bool enforce;
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+struct ipe_bdev {
+ bool dm_verity_signed;
+
+ const u8 *digest;
+ size_t digest_len;
+ const char *digest_algo;
+};
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
struct ipe_eval_ctx {
enum ipe_op_type op;
const struct file *file;
bool from_init_sb;
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ const struct ipe_bdev *ipe_bdev;
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
enum ipe_match {
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index e9386762a597..8b8031e66f36 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -7,6 +7,9 @@
#include <linux/types.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
+#include <linux/blk_types.h>
+#include <linux/dm-verity.h>
+#include <crypto/hash_info.h>
#include "ipe.h"
#include "hooks.h"
@@ -193,3 +196,51 @@ void ipe_sb_free_security(struct super_block *mnt_sb)
{
ipe_invalidate_pinned_sb(mnt_sb);
}
+
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+/**
+ * ipe_bdev_free_security - free IPE's LSM blob of block_devices.
+ * @bdev: Supplies a pointer to a block_device that contains the structure
+ * to free.
+ */
+void ipe_bdev_free_security(struct block_device *bdev)
+{
+ struct ipe_bdev *blob = ipe_bdev(bdev);
+
+ kfree(blob->digest);
+ kfree(blob->digest_algo);
+}
+
+/**
+ * ipe_bdev_setsecurity - save data from a bdev to IPE's LSM blob.
+ * @bdev: Supplies a pointer to a block_device that contains the LSM blob.
+ * @key: Supplies the string key that uniquely identifies the value.
+ * @value: Supplies the value to store.
+ * @len: The length of @value.
+ */
+int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
+ const void *value, size_t len)
+{
+ struct ipe_bdev *blob = ipe_bdev(bdev);
+
+ if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) {
+ const struct dm_verity_digest *digest = value;
+
+ blob->digest = kmemdup(digest->digest, digest->digest_len, GFP_KERNEL);
+ if (!blob->digest)
+ return -ENOMEM;
+
+ blob->digest_algo = kstrdup_const(digest->algo, GFP_KERNEL);
+ if (!blob->digest_algo)
+ return -ENOMEM;
+
+ blob->digest_len = digest->digest_len;
+ return 0;
+ } else if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) {
+ blob->dm_verity_signed = true;
+ return 0;
+ }
+
+ return -EOPNOTSUPP;
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index ac0cdfd9877f..d8ccb3728813 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -8,6 +8,7 @@
#include <linux/fs.h>
#include <linux/binfmts.h>
#include <linux/security.h>
+#include <linux/blk_types.h>
int ipe_bprm_check_security(struct linux_binprm *bprm);
@@ -24,4 +25,11 @@ int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents);
void ipe_sb_free_security(struct super_block *mnt_sb);
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+void ipe_bdev_free_security(struct block_device *bdev);
+
+int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
+ const void *value, size_t len);
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
#endif /* _IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 783058c06cd6..c7e8af554d35 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -5,12 +5,23 @@
#include "ipe.h"
#include "hooks.h"
+#include "eval.h"
bool ipe_enabled;
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ .lbs_bdev = sizeof(struct ipe_bdev),
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+struct ipe_bdev *ipe_bdev(struct block_device *b)
+{
+ return b->security + ipe_blobs.lbs_bdev;
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(bprm_check_security, ipe_bprm_check_security),
LSM_HOOK_INIT(mmap_file, ipe_mmap_file),
@@ -18,6 +29,10 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(kernel_read_file, ipe_kernel_read_file),
LSM_HOOK_INIT(kernel_load_data, ipe_kernel_load_data),
LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security),
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
+ LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity),
+#endif
};
/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index 6dec06403eee..4e8d1a440c4b 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -15,4 +15,8 @@
extern bool ipe_enabled;
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+struct ipe_bdev *ipe_bdev(struct block_device *b);
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
#endif /* _IPE_H */
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index 32e5e0b941eb..13e5c40e9204 100644
--- a/security/ipe/policy.h
+++ b/security/ipe/policy.h
@@ -33,6 +33,9 @@ enum ipe_action_type {
enum ipe_prop_type {
IPE_PROP_BOOT_VERIFIED_FALSE,
IPE_PROP_BOOT_VERIFIED_TRUE,
+ IPE_PROP_DMV_ROOTHASH,
+ IPE_PROP_DMV_SIG_FALSE,
+ IPE_PROP_DMV_SIG_TRUE,
__IPE_PROP_MAX
};
diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
index ee7646de72ed..3acb1d681f65 100644
--- a/security/ipe/policy_parser.c
+++ b/security/ipe/policy_parser.c
@@ -10,6 +10,7 @@
#include "policy.h"
#include "policy_parser.h"
+#include "digest.h"
#define START_COMMENT '#'
#define IPE_POLICY_DELIM " \t"
@@ -216,6 +217,7 @@ static void free_rule(struct ipe_rule *r)
list_for_each_entry_safe(p, t, &r->props, next) {
list_del(&p->next);
+ ipe_digest_free(&p->value);
kfree(p);
}
@@ -268,6 +270,11 @@ static enum ipe_action_type parse_action(char *t)
static const match_table_t property_tokens = {
{IPE_PROP_BOOT_VERIFIED_FALSE, "boot_verified=FALSE"},
{IPE_PROP_BOOT_VERIFIED_TRUE, "boot_verified=TRUE"},
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ {IPE_PROP_DMV_ROOTHASH, "dmverity_roothash=%s"},
+ {IPE_PROP_DMV_SIG_FALSE, "dmverity_signature=FALSE"},
+ {IPE_PROP_DMV_SIG_TRUE, "dmverity_signature=TRUE"},
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
{IPE_PROP_INVALID, NULL}
};
@@ -287,6 +294,7 @@ static int parse_property(char *t, struct ipe_rule *r)
struct ipe_prop *p = NULL;
int rc = 0;
int token;
+ char *dup = NULL;
p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p)
@@ -295,8 +303,20 @@ static int parse_property(char *t, struct ipe_rule *r)
token = match_token(t, property_tokens, args);
switch (token) {
+ case IPE_PROP_DMV_ROOTHASH:
+ dup = match_strdup(&args[0]);
+ if (!dup) {
+ rc = -ENOMEM;
+ goto err;
+ }
+ rc = ipe_digest_parse(dup, &p->value);
+ if (rc)
+ goto err;
+ fallthrough;
case IPE_PROP_BOOT_VERIFIED_FALSE:
case IPE_PROP_BOOT_VERIFIED_TRUE:
+ case IPE_PROP_DMV_SIG_FALSE:
+ case IPE_PROP_DMV_SIG_TRUE:
p->type = token;
break;
default:
@@ -307,10 +327,12 @@ static int parse_property(char *t, struct ipe_rule *r)
goto err;
list_add_tail(&p->next, &r->props);
+out:
+ kfree(dup);
return rc;
err:
kfree(p);
- return rc;
+ goto out;
}
/**
--
2.25.1
From: Deven Bowers <[email protected]>
IPE, like SELinux, supports a permissive mode. This mode allows policy
authors to test and evaluate IPE policy without it effecting their
programs. When the mode is changed, a 1404 AUDIT_MAC_STATUS
be reported.
This patch adds the following audit records:
audit: MAC_STATUS enforcing=0 old_enforcing=1 auid=4294967295
ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
audit: MAC_STATUS enforcing=1 old_enforcing=0 auid=4294967295
ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
The audit record only emit when the value from the user input is
different from the current enforce value.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks,
and evaluation loop from policy parser and userspace
interface to pass mailing list character limit
v3:
+ Move ipe_load_properties to patch 04.
+ Remove useless 0-initializations
+ Prefix extern variables with ipe_
+ Remove kernel module parameters, as these are
exposed through sysctls.
+ Add more prose to the IPE base config option
help text.
+ Use GFP_KERNEL for audit_log_start.
+ Remove unnecessary caching system.
+ Remove comments from headers
+ Use rcu_access_pointer for rcu-pointer null check
+ Remove usage of reqprot; use prot only.
+ Move policy load and activation audit event to 03/12
v4:
+ Remove sysctls in favor of securityfs nodes
+ Re-add kernel module parameters, as these are now
exposed through securityfs.
+ Refactor property audit loop to a separate function.
v5:
+ fix minor grammatical errors
+ do not group rule by curly-brace in audit record,
reconstruct the exact rule.
v6:
+ No changes
v7:
+ Further split lsm creation into a separate commit from the
evaluation loop and audit system, for easier review.
+ Propagating changes to support the new ipe_context structure in the
evaluation loop.
+ Split out permissive functionality into a separate patch for easier
review.
+ Remove permissive switch compile-time configuration option - this
is trivial to add later.
v8:
+ Remove "IPE" prefix from permissive audit record
+ align fields to the linux-audit field dictionary. This causes the
following fields to change:
enforce -> permissive
+ Remove duplicated information correlated with syscall record, that
will always be present in the audit event.
+ Change audit types:
+ AUDIT_TRUST_STATUS -> AUDIT_MAC_STATUS
+ There is no significant difference in meaning between
these types.
v9:
+ Clean up ipe_context related code
v10:
+ Change audit format to comform with the existing format selinux is
using
+ Remove the audit record emission during init to align with selinux,
which does not perform this action.
v11:
+ Remove redundant code
---
security/ipe/audit.c | 22 ++++++++++++++
security/ipe/audit.h | 1 +
security/ipe/eval.c | 14 +++++++--
security/ipe/eval.h | 1 +
security/ipe/fs.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 104 insertions(+), 2 deletions(-)
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index e123701d5e3b..0dd5f10c318f 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -193,3 +193,25 @@ void ipe_audit_policy_load(const struct ipe_policy *const p)
audit_log_end(ab);
}
+
+/**
+ * ipe_audit_enforce - Audit a change in IPE's enforcement state.
+ * @new_enforce: The new value enforce to be set.
+ * @old_enforce: The old value currently in enforce.
+ */
+void ipe_audit_enforce(bool new_enforce, bool old_enforce)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_MAC_STATUS);
+ if (!ab)
+ return;
+
+ audit_log_format(ab, "enforcing=%d old_enforcing=%d auid=%u ses=%u"
+ " enabled=1 old-enabled=1 lsm=ipe res=1",
+ new_enforce, old_enforce,
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ audit_get_sessionid(current));
+
+ audit_log_end(ab);
+}
diff --git a/security/ipe/audit.h b/security/ipe/audit.h
index 0ff5a06808de..914f001e5286 100644
--- a/security/ipe/audit.h
+++ b/security/ipe/audit.h
@@ -14,5 +14,6 @@ void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
void ipe_audit_policy_load(const struct ipe_policy *const p);
void ipe_audit_policy_activation(const struct ipe_policy *const op,
const struct ipe_policy *const np);
+void ipe_audit_enforce(bool new_enforce, bool old_enforce);
#endif /* _IPE_AUDIT_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 499b6b3338f2..78c54ff1fdd3 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -19,6 +19,7 @@
struct ipe_policy __rcu *ipe_active_policy;
bool success_audit;
+bool enforce = true;
static const struct super_block *pinned_sb;
static DEFINE_SPINLOCK(pin_lock);
@@ -114,12 +115,14 @@ static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
{
bool match = false;
+ bool enforcing = true;
enum ipe_action_type action;
enum ipe_match match_type;
struct ipe_policy *pol = NULL;
const struct ipe_rule *rule = NULL;
const struct ipe_op_table *rules = NULL;
struct ipe_prop *prop = NULL;
+ int rc = 0;
rcu_read_lock();
@@ -129,6 +132,8 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
return 0;
}
+ enforcing = READ_ONCE(enforce);
+
if (ctx->op == IPE_OP_INVALID) {
rcu_read_unlock();
action = pol->parsed->global_default_action;
@@ -167,9 +172,12 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
ipe_audit_match(ctx, match_type, action, rule);
if (action == IPE_ACTION_DENY)
- return -EACCES;
+ rc = -EACCES;
+
+ if (!enforcing)
+ rc = 0;
- return 0;
+ return rc;
}
/**
@@ -198,3 +206,5 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
module_param(success_audit, bool, 0400);
MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
+module_param(enforce, bool, 0400);
+MODULE_PARM_DESC(enforce, "Start IPE in enforce or permissive mode");
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 5473f712566c..3f7f71452618 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -15,6 +15,7 @@
extern struct ipe_policy __rcu *ipe_active_policy;
extern bool success_audit;
+extern bool enforce;
struct ipe_eval_ctx {
enum ipe_op_type op;
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index dda7a5afc60c..0a1838432bd0 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -16,6 +16,7 @@ static struct dentry *np __ro_after_init;
static struct dentry *root __ro_after_init;
struct dentry *policy_root __ro_after_init;
static struct dentry *audit_node __ro_after_init;
+static struct dentry *enforce_node __ro_after_init;
/**
* setaudit - Write handler for the securityfs node, "ipe/success_audit"
@@ -67,6 +68,60 @@ static ssize_t getaudit(struct file *f, char __user *data,
return simple_read_from_buffer(data, len, offset, result, 1);
}
+/**
+ * setenforce - Write handler for the securityfs node, "ipe/enforce"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t setenforce(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ bool new_value, old_value;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ old_value = READ_ONCE(enforce);
+ rc = kstrtobool_from_user(data, len, &new_value);
+ if (rc)
+ return rc;
+
+ if (new_value != old_value) {
+ ipe_audit_enforce(new_value, old_value);
+ WRITE_ONCE(enforce, new_value);
+ }
+
+ return len;
+}
+
+/**
+ * getenforce - Read handler for the securityfs node, "ipe/enforce"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the read syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getenforce(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ const char *result;
+
+ result = ((READ_ONCE(enforce)) ? "1" : "0");
+
+ return simple_read_from_buffer(data, len, offset, result, 1);
+}
+
/**
* new_policy - Write handler for the securityfs node, "ipe/new_policy".
* @f: Supplies a file structure representing the securityfs node.
@@ -120,6 +175,11 @@ static const struct file_operations audit_fops = {
.read = getaudit,
};
+static const struct file_operations enforce_fops = {
+ .write = setenforce,
+ .read = getenforce,
+};
+
/**
* ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
*
@@ -147,6 +207,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}
+ enforce_node = securityfs_create_file("enforce", 0600, root, NULL,
+ &enforce_fops);
+ if (IS_ERR(enforce_node)) {
+ rc = PTR_ERR(enforce_node);
+ goto err;
+ }
+
policy_root = securityfs_create_dir("policies", root);
if (IS_ERR(policy_root)) {
rc = PTR_ERR(policy_root);
@@ -163,6 +230,7 @@ static int __init ipe_init_securityfs(void)
err:
securityfs_remove(np);
securityfs_remove(policy_root);
+ securityfs_remove(enforce_node);
securityfs_remove(audit_node);
securityfs_remove(root);
return rc;
--
2.25.1
From: Deven Bowers <[email protected]>
Some block devices have valuable security properties that is only
accessible during the creation time.
For example, when creating a dm-verity block device, the dm-verity's
roothash and roothash signature, which are extreme important security
metadata, are passed to the kernel. However, the roothash will be saved
privately in dm-verity, which prevents the seucrity subsystem to easily
access that information. Worse, the roothash signature will be discarded
after the verification, making it impossible to utilize the roothash
signature by the security subsystem.
With this patch, an LSM blob is added to the block_device structure.
This enables the security subsystem to store security-sensitive data
related to block devices within the security blob. For example, LSM can
use the new LSM blob to save the roothash signature of a dm-verity,
and LSM can make access decision based on the data inside the signature,
like the signer ceritificate.
The implementation follows the same approach used for security blobs in
other structures like struct file, struct inode, and struct superblock.
The initialization of the security blob occurs after the creation of the
struct block_device, performed by the security subsystem. Similarly, the
security blob is freed by the security subsystem before the struct
block_device is deallocated or freed.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
Reviewed-by: Casey Schaufler <[email protected]>
---
v2:
+ No Changes
v3:
+ Minor style changes from checkpatch --strict
v4:
+ No Changes
v5:
+ Allow multiple callers to call security_bdev_setsecurity
v6:
+ Simplify security_bdev_setsecurity break condition
v7:
+ Squash all dm-verity related patches to two patches,
the additions to dm-verity/fs, and the consumption of
the additions.
v8:
+ Split dm-verity related patches squashed in v7 to 3 commits based on
topic:
+ New LSM hook
+ Consumption of hook outside LSM
+ Consumption of hook inside LSM.
+ change return of security_bdev_alloc / security_bdev_setsecurity
to LSM_RET_DEFAULT instead of 0.
+ Change return code to -EOPNOTSUPP, bring inline with other
setsecurity hooks.
v9:
+ Add Reviewed-by: Casey Schaufler <[email protected]>
+ Remove unlikely when calling LSM hook
+ Make the security field dependent on CONFIG_SECURITY
v10:
+ No changes
v11:
+ No changes
---
block/bdev.c | 7 +++
include/linux/blk_types.h | 3 ++
include/linux/lsm_hook_defs.h | 5 ++
include/linux/lsm_hooks.h | 1 +
include/linux/security.h | 22 ++++++++
security/security.c | 99 +++++++++++++++++++++++++++++++++++
6 files changed, 137 insertions(+)
diff --git a/block/bdev.c b/block/bdev.c
index f3b13aa1b7d4..b4b34275bba7 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -24,6 +24,7 @@
#include <linux/pseudo_fs.h>
#include <linux/uio.h>
#include <linux/namei.h>
+#include <linux/security.h>
#include <linux/part_stat.h>
#include <linux/uaccess.h>
#include <linux/stat.h>
@@ -301,6 +302,11 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
if (!ei)
return NULL;
memset(&ei->bdev, 0, sizeof(ei->bdev));
+
+ if (security_bdev_alloc(&ei->bdev)) {
+ kmem_cache_free(bdev_cachep, ei);
+ return NULL;
+ }
return &ei->vfs_inode;
}
@@ -310,6 +316,7 @@ static void bdev_free_inode(struct inode *inode)
free_percpu(bdev->bd_stats);
kfree(bdev->bd_meta_info);
+ security_bdev_free(bdev);
if (!bdev_is_partition(bdev)) {
if (bdev->bd_disk && bdev->bd_disk->bdi)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d5c5e59ddbd2..71034e45f3d9 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -68,6 +68,9 @@ struct block_device {
struct partition_meta_info *bd_meta_info;
#ifdef CONFIG_FAIL_MAKE_REQUEST
bool bd_make_it_fail;
+#endif
+#ifdef CONFIG_SECURITY
+ void *security;
#endif
/*
* keep this out-of-line as it's both big and not needed in the fast
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index ac962c4cb44b..00c283180b55 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -419,3 +419,8 @@ LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
LSM_HOOK(int, 0, uring_sqpoll, void)
LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
#endif /* CONFIG_IO_URING */
+
+LSM_HOOK(int, 0, bdev_alloc_security, struct block_device *bdev)
+LSM_HOOK(void, LSM_RET_VOID, bdev_free_security, struct block_device *bdev)
+LSM_HOOK(int, 0, bdev_setsecurity, struct block_device *bdev, const char *name,
+ const void *value, size_t size)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index dcb5e5b5eb13..5e8c859f5c6c 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -65,6 +65,7 @@ struct lsm_blob_sizes {
int lbs_msg_msg;
int lbs_task;
int lbs_xattr_count; /* number of xattr slots in new_xattrs array */
+ int lbs_bdev;
};
/**
diff --git a/include/linux/security.h b/include/linux/security.h
index 8fa3bab9fa10..8b85eeb80425 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -484,6 +484,11 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
int security_locked_down(enum lockdown_reason what);
+int security_bdev_alloc(struct block_device *bdev);
+void security_bdev_free(struct block_device *bdev);
+int security_bdev_setsecurity(struct block_device *bdev,
+ const char *name, const void *value,
+ size_t size);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1395,6 +1400,23 @@ static inline int security_locked_down(enum lockdown_reason what)
{
return 0;
}
+
+static inline int security_bdev_alloc(struct block_device *bdev)
+{
+ return 0;
+}
+
+static inline void security_bdev_free(struct block_device *bdev)
+{
+}
+
+static inline int security_bdev_setsecurity(struct block_device *bdev,
+ const char *name,
+ const void *value, size_t size)
+{
+ return 0;
+}
+
#endif /* CONFIG_SECURITY */
#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/security.c b/security/security.c
index 23b129d482a7..9275126660c0 100644
--- a/security/security.c
+++ b/security/security.c
@@ -30,6 +30,7 @@
#include <linux/string.h>
#include <linux/msg.h>
#include <net/flow.h>
+#include <linux/fs.h>
/* How many LSMs were built into the kernel? */
#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
@@ -212,6 +213,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
lsm_set_blob_size(&needed->lbs_xattr_count,
&blob_sizes.lbs_xattr_count);
+ lsm_set_blob_size(&needed->lbs_bdev, &blob_sizes.lbs_bdev);
}
/* Prepare LSM for initialization. */
@@ -379,6 +381,7 @@ static void __init ordered_lsm_init(void)
init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
init_debug("task blob size = %d\n", blob_sizes.lbs_task);
init_debug("xattr slots = %d\n", blob_sizes.lbs_xattr_count);
+ init_debug("bdev blob size = %d\n", blob_sizes.lbs_bdev);
/*
* Create any kmem_caches needed for blobs
@@ -699,6 +702,28 @@ static int lsm_msg_msg_alloc(struct msg_msg *mp)
return 0;
}
+/**
+ * lsm_bdev_alloc - allocate a composite block_device blob
+ * @bdev: the block_device that needs a blob
+ *
+ * Allocate the block_device blob for all the modules
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+static int lsm_bdev_alloc(struct block_device *bdev)
+{
+ if (blob_sizes.lbs_bdev == 0) {
+ bdev->security = NULL;
+ return 0;
+ }
+
+ bdev->security = kzalloc(blob_sizes.lbs_bdev, GFP_KERNEL);
+ if (!bdev->security)
+ return -ENOMEM;
+
+ return 0;
+}
+
/**
* lsm_early_task - during initialization allocate a composite task blob
* @task: the task that needs a blob
@@ -5230,6 +5255,80 @@ int security_locked_down(enum lockdown_reason what)
}
EXPORT_SYMBOL(security_locked_down);
+/**
+ * security_bdev_alloc() - Allocate a block device LSM blob
+ * @bdev: block device
+ *
+ * Allocate and attach a security structure to @bdev->security. The
+ * security field is initialized to NULL when the bdev structure is
+ * allocated.
+ *
+ * Return: Return 0 if operation was successful.
+ */
+int security_bdev_alloc(struct block_device *bdev)
+{
+ int rc = 0;
+
+ rc = lsm_bdev_alloc(bdev);
+ if (unlikely(rc))
+ return rc;
+
+ rc = call_int_hook(bdev_alloc_security, 0, bdev);
+ if (unlikely(rc))
+ security_bdev_free(bdev);
+
+ return LSM_RET_DEFAULT(bdev_alloc_security);
+}
+EXPORT_SYMBOL(security_bdev_alloc);
+
+/**
+ * security_bdev_free() - Free a block device's LSM blob
+ * @bdev: block device
+ *
+ * Deallocate the bdev security structure and set @bdev->security to NULL.
+ */
+void security_bdev_free(struct block_device *bdev)
+{
+ if (!bdev->security)
+ return;
+
+ call_void_hook(bdev_free_security, bdev);
+
+ kfree(bdev->security);
+ bdev->security = NULL;
+}
+EXPORT_SYMBOL(security_bdev_free);
+
+/**
+ * security_bdev_setsecurity() - Set a security property of a block device
+ * @bdev: block device
+ * @name: security property name
+ * @value: security property value
+ * @size: length of the property value
+ *
+ * Set the security property associated with @name for @bdev from the security
+ * property value @value. @size indicates the size of the @value in bytes.
+ * If a @name is not implemented for a hook, it should return -EOPNOTSUPP.
+ *
+ * Return: Returns 0 on success.
+ */
+int security_bdev_setsecurity(struct block_device *bdev,
+ const char *name, const void *value,
+ size_t size)
+{
+ int rc = 0;
+ struct security_hook_list *p;
+
+ hlist_for_each_entry(p, &security_hook_heads.bdev_setsecurity, list) {
+ rc = p->hook.bdev_setsecurity(bdev, name, value, size);
+ if (rc && rc != -EOPNOTSUPP)
+ return rc;
+ }
+
+ return LSM_RET_DEFAULT(bdev_setsecurity);
+}
+EXPORT_SYMBOL(security_bdev_setsecurity);
+
#ifdef CONFIG_PERF_EVENTS
/**
* security_perf_event_open() - Check if a perf event open is allowed
--
2.25.1
fsverity represents a mechanism to support both integrity and
authenticity protection of a file, supporting both signed and unsigned
digests.
An LSM which controls access to a resource based on authenticity and
integrity of said resource, can then use this data to make an informed
decision on the authorization (provided by the LSM's policy) of said
claim.
This effectively allows the extension of a policy enforcement layer in
LSM for fsverity, allowing for more granular control of how a
particular authenticity claim can be used. For example, "all (built-in)
signed fsverity files should be allowed to execute, but only these
hashes are allowed to be loaded as kernel modules".
This enforcement must be done in kernel space, as a userspace only
solution would fail a simple litmus test: Download a self-contained
malicious binary that never touches the userspace stack. This
binary would still be able to execute.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v1-v6:
+ Not present
v7:
Introduced
v8:
+ Split fs/verity/ changes and security/ changes into separate patches
+ Change signature of fsverity_create_info to accept non-const inode
+ Change signature of fsverity_verify_signature to accept non-const inode
+ Don't cast-away const from inode.
+ Digest functionality dropped in favor of:
("fs-verity: define a function to return the integrity protected
file digest")
+ Reworded commit description and title to match changes.
+ Fix a bug wherein no LSM implements the particular fsverity @name
(or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
v9:
+ No changes
v10:
+ Rename the signature blob key
+ Cleanup redundant code
+ Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
v11:
+ No changes
---
fs/verity/fsverity_private.h | 2 +-
fs/verity/open.c | 26 +++++++++++++++++++++++++-
include/linux/fsverity.h | 2 ++
3 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index d071a6e32581..4a82716e852f 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -108,7 +108,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
unsigned int log_blocksize,
const u8 *salt, size_t salt_size);
-struct fsverity_info *fsverity_create_info(const struct inode *inode,
+struct fsverity_info *fsverity_create_info(struct inode *inode,
struct fsverity_descriptor *desc);
void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
diff --git a/fs/verity/open.c b/fs/verity/open.c
index 6c31a871b84b..5b48e2c39086 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -8,6 +8,7 @@
#include "fsverity_private.h"
#include <linux/mm.h>
+#include <linux/security.h>
#include <linux/slab.h>
static struct kmem_cache *fsverity_info_cachep;
@@ -172,12 +173,28 @@ static int compute_file_digest(const struct fsverity_hash_alg *hash_alg,
return err;
}
+#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
+static int fsverity_inode_setsecurity(struct inode *inode,
+ struct fsverity_descriptor *desc)
+{
+ return security_inode_setsecurity(inode, FS_VERITY_INODE_SEC_NAME,
+ desc->signature,
+ le32_to_cpu(desc->sig_size), 0);
+}
+#else
+static inline int fsverity_inode_setsecurity(struct inode *inode,
+ struct fsverity_descriptor *desc)
+{
+ return 0;
+}
+#endif /* CONFIG_IPE_PROP_FS_VERITY*/
+
/*
* Create a new fsverity_info from the given fsverity_descriptor (with optional
* appended builtin signature), and check the signature if present. The
* fsverity_descriptor must have already undergone basic validation.
*/
-struct fsverity_info *fsverity_create_info(const struct inode *inode,
+struct fsverity_info *fsverity_create_info(struct inode *inode,
struct fsverity_descriptor *desc)
{
struct fsverity_info *vi;
@@ -242,6 +259,13 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
spin_lock_init(&vi->hash_page_init_lock);
}
+ err = fsverity_inode_setsecurity(inode, desc);
+ if (err == -EOPNOTSUPP)
+ err = 0;
+
+ if (err)
+ goto fail;
+
return vi;
fail:
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 1eb7eae580be..9666721baf15 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -319,4 +319,6 @@ static inline int fsverity_prepare_setattr(struct dentry *dentry,
return 0;
}
+#define FS_VERITY_INODE_SEC_NAME "fsverity.builtin-sig"
+
#endif /* _LINUX_FSVERITY_H */
--
2.25.1
From: Deven Bowers <[email protected]>
IPE is designed to provide system level trust guarantees, this usually
implies that trust starts from bootup with a hardware root of trust,
which validates the bootloader. After this, the bootloader verifies the
kernel and the initramfs.
As there's no currently supported integrity method for initramfs, and
it's typically already verified by the bootloader, introduce a property
that causes the first superblock to have an execution to be "pinned",
which is typically initramfs.
When the "pinned" device is unmounted, it will be "unpinned" and
`boot_verified` property will always evaluate to false afterward.
We use a pointer with a spin_lock to "pin" the device instead of rcu
because rcu synchronization may sleep, which is not allowed when
unmounting a device.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+No Changes
v3:
+ Remove useless caching system
+ Move ipe_load_properties to this match
+ Minor changes from checkpatch --strict warnings
v4:
+ Remove comments from headers that was missed previously.
+ Grammatical corrections.
v5:
+ No significant changes
v6:
+ No changes
v7:
+ Reword and refactor patch 04/12 to [09/16], based on changes in the underlying system.
+ Add common audit function for boolean values
+ Use common audit function as implementation.
v8:
+ No changes
v9:
+ No changes
v10:
+ Replace struct file with struct super_block
v11:
+ Fix code style issues
---
security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
security/ipe/eval.h | 2 +
security/ipe/hooks.c | 12 ++++++
security/ipe/hooks.h | 2 +
security/ipe/ipe.c | 1 +
security/ipe/policy.h | 2 +
security/ipe/policy_parser.c | 35 +++++++++++++++++-
7 files changed, 124 insertions(+), 2 deletions(-)
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 8a8bcc5c7d7f..bdac4abc0ddb 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -9,6 +9,7 @@
#include <linux/file.h>
#include <linux/sched.h>
#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
#include "ipe.h"
#include "eval.h"
@@ -16,6 +17,44 @@
struct ipe_policy __rcu *ipe_active_policy;
+static const struct super_block *pinned_sb;
+static DEFINE_SPINLOCK(pin_lock);
+#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
+
+/**
+ * pin_sb - Pin the underlying superblock of @f, marking it as trusted.
+ * @sb: Supplies a super_block structure to be pinned.
+ */
+static void pin_sb(const struct super_block *sb)
+{
+ if (!sb)
+ return;
+ spin_lock(&pin_lock);
+ if (!pinned_sb)
+ pinned_sb = sb;
+ spin_unlock(&pin_lock);
+}
+
+/**
+ * from_pinned - Determine whether @sb is the pinned super_block.
+ * @sb: Supplies a super_block to check against the pinned super_block.
+ *
+ * Return:
+ * * true - @sb is the pinned super_block
+ * * false - @sb is not the pinned super_block
+ */
+static bool from_pinned(const struct super_block *sb)
+{
+ bool rv;
+
+ if (!sb)
+ return false;
+ spin_lock(&pin_lock);
+ rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
+ spin_unlock(&pin_lock);
+ return rv;
+}
+
/**
* build_eval_ctx - Build an evaluation context.
* @ctx: Supplies a pointer to the context to be populdated.
@@ -26,8 +65,14 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
const struct file *file,
enum ipe_op_type op)
{
+ if (op == IPE_OP_EXEC && file)
+ pin_sb(FILE_SUPERBLOCK(file));
+
ctx->file = file;
ctx->op = op;
+
+ if (file)
+ ctx->from_init_sb = from_pinned(FILE_SUPERBLOCK(file));
}
/**
@@ -42,7 +87,14 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
struct ipe_prop *p)
{
- return false;
+ switch (p->type) {
+ case IPE_PROP_BOOT_VERIFIED_FALSE:
+ return !ctx->from_init_sb;
+ case IPE_PROP_BOOT_VERIFIED_TRUE:
+ return ctx->from_init_sb;
+ default:
+ return false;
+ }
}
/**
@@ -108,3 +160,21 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
return 0;
}
+
+/**
+ * ipe_invalidate_pinned_sb - invalidate the ipe pinned super_block.
+ * @mnt_sb: super_block to check against the pinned super_block.
+ *
+ * This function is called a super_block like the initramfs's is freed,
+ * if the super_block is currently pinned by ipe it will be invalided,
+ * so ipe won't consider the block device is boot verified afterward.
+ */
+void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
+{
+ spin_lock(&pin_lock);
+
+ if (mnt_sb == pinned_sb)
+ pinned_sb = ERR_PTR(-EIO);
+
+ spin_unlock(&pin_lock);
+}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index cfdf3c8dfe8a..9769da42c65f 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -19,9 +19,11 @@ struct ipe_eval_ctx {
enum ipe_op_type op;
const struct file *file;
+ bool from_init_sb;
};
void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
+void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb);
#endif /* _IPE_EVAL_H */
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index 6164a9b53361..e9386762a597 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -181,3 +181,15 @@ int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents)
build_eval_ctx(&ctx, NULL, op);
return ipe_evaluate_event(&ctx);
}
+
+/**
+ * ipe_sb_free_security - ipe security hook function for super_block.
+ * @mnt_sb: Supplies a pointer to a super_block is about to be freed.
+ *
+ * IPE does not have any structures with mnt_sb, but uses this hook to
+ * invalidate a pinned super_block.
+ */
+void ipe_sb_free_security(struct super_block *mnt_sb)
+{
+ ipe_invalidate_pinned_sb(mnt_sb);
+}
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 23205452f758..ac0cdfd9877f 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -22,4 +22,6 @@ int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents);
+void ipe_sb_free_security(struct super_block *mnt_sb);
+
#endif /* _IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 77c950459810..06da94a58aba 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -15,6 +15,7 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_mprotect, ipe_file_mprotect),
LSM_HOOK_INIT(kernel_read_file, ipe_kernel_read_file),
LSM_HOOK_INIT(kernel_load_data, ipe_kernel_load_data),
+ LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security),
};
/**
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index 77aa91f2b953..45704465dc01 100644
--- a/security/ipe/policy.h
+++ b/security/ipe/policy.h
@@ -30,6 +30,8 @@ enum ipe_action_type {
#define IPE_ACTION_INVALID __IPE_ACTION_MAX
enum ipe_prop_type {
+ IPE_PROP_BOOT_VERIFIED_FALSE,
+ IPE_PROP_BOOT_VERIFIED_TRUE,
__IPE_PROP_MAX
};
diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
index c09458bd348d..ee7646de72ed 100644
--- a/security/ipe/policy_parser.c
+++ b/security/ipe/policy_parser.c
@@ -265,6 +265,12 @@ static enum ipe_action_type parse_action(char *t)
return match_token(t, action_tokens, args);
}
+static const match_table_t property_tokens = {
+ {IPE_PROP_BOOT_VERIFIED_FALSE, "boot_verified=FALSE"},
+ {IPE_PROP_BOOT_VERIFIED_TRUE, "boot_verified=TRUE"},
+ {IPE_PROP_INVALID, NULL}
+};
+
/**
* parse_property - Parse the property type given a token string.
* @t: Supplies the token string to be parsed.
@@ -277,7 +283,34 @@ static enum ipe_action_type parse_action(char *t)
*/
static int parse_property(char *t, struct ipe_rule *r)
{
- return -EBADMSG;
+ substring_t args[MAX_OPT_ARGS];
+ struct ipe_prop *p = NULL;
+ int rc = 0;
+ int token;
+
+ p = kzalloc(sizeof(*p), GFP_KERNEL);
+ if (!p)
+ return -ENOMEM;
+
+ token = match_token(t, property_tokens, args);
+
+ switch (token) {
+ case IPE_PROP_BOOT_VERIFIED_FALSE:
+ case IPE_PROP_BOOT_VERIFIED_TRUE:
+ p->type = token;
+ break;
+ default:
+ rc = -EBADMSG;
+ break;
+ }
+ if (rc)
+ goto err;
+ list_add_tail(&p->next, &r->props);
+
+ return rc;
+err:
+ kfree(p);
+ return rc;
}
/**
--
2.25.1
From: Deven Bowers <[email protected]>
Add IPE's admin and developer documentation to the kernel tree.
Co-developed-by: Fan Wu <[email protected]>
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ No Changes
v3:
+ Add Acked-by
+ Fixup code block syntax
+ Fix a minor grammatical issue.
v4:
+ Update documentation with the results of other
code changes.
v5:
+ No changes
v6:
+ No changes
v7:
+ Add additional developer-level documentation
+ Update admin-guide docs to reflect changes.
+ Drop Acked-by due to significant changes
+ Added section about audit events in admin-guide
v8:
+ Correct terminology from "audit event" to "audit record"
+ Add associated documentation with the correct "audit event"
terminology.
+ Add some context to the historical motivation for IPE and design
philosophy.
+ Add some content about the securityfs layout in the policies
directory.
+ Various spelling and grammatical corrections.
v9:
+ Correct spelling of "pitfalls"
+ Update the docs w.r.t the new parser and new audit formats
v10:
+ Refine user docs per upstream suggetions
+ Update audit events part
v11:
+ No changes
---
Documentation/admin-guide/LSM/index.rst | 1 +
Documentation/admin-guide/LSM/ipe.rst | 752 ++++++++++++++++++
.../admin-guide/kernel-parameters.txt | 12 +
Documentation/security/index.rst | 1 +
Documentation/security/ipe.rst | 420 ++++++++++
MAINTAINERS | 2 +
6 files changed, 1188 insertions(+)
create mode 100644 Documentation/admin-guide/LSM/ipe.rst
create mode 100644 Documentation/security/ipe.rst
diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst
index a6ba95fbaa9f..ce63be6d64ad 100644
--- a/Documentation/admin-guide/LSM/index.rst
+++ b/Documentation/admin-guide/LSM/index.rst
@@ -47,3 +47,4 @@ subdirectories.
tomoyo
Yama
SafeSetID
+ ipe
diff --git a/Documentation/admin-guide/LSM/ipe.rst b/Documentation/admin-guide/LSM/ipe.rst
new file mode 100644
index 000000000000..da59f78427fa
--- /dev/null
+++ b/Documentation/admin-guide/LSM/ipe.rst
@@ -0,0 +1,752 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Integrity Policy Enforcement (IPE)
+==================================
+
+.. NOTE::
+
+ This is the documentation for admins, system builders, or individuals
+ attempting to use IPE. If you're looking for more developer-focused
+ documentation about IPE please see `Documentation/security/ipe.rst`
+
+Overview
+--------
+
+IPE is a Linux Security Module which takes a complimentary approach to
+access control. Whereas existing mandatory access control mechanisms
+base their decisions on labels and paths, IPE instead determines
+whether or not an operation should be allowed based on immutable
+security properties of the system component the operation is being
+performed on.
+
+IPE itself does not mandate how the security property should be
+evaluated, but relies on an extensible set of external property providers
+to evaluate the component. IPE makes its decision based on reference
+values for the selected properties, specified in the IPE policy.
+
+The reference values represent the value that the policy writer and the
+local system administrator (based on the policy signature) trust for the
+system to accomplish the desired tasks.
+
+One such provider is for example dm-verity, which is able to represent
+the integrity property of a partition (its immutable state) with a digest.
+
+To enable IPE, ensure that ``CONFIG_SECURITY_IPE`` (under
+:menuselection:`Security -> Integrity Policy Enforcement (IPE)`) config
+option is enabled.
+
+Use Cases
+---------
+
+IPE works best in fixed-function devices: devices in which their purpose
+is clearly defined and not supposed to be changed (e.g. network firewall
+device in a data center, an IoT device, etcetera), where all software and
+configuration is built and provisioned by the system owner.
+
+IPE is a long-way off for use in general-purpose computing: the Linux
+community as a whole tends to follow a decentralized trust model (known as
+the web of trust), which IPE has no support for it yet. Instead, IPE
+supports PKI (public key infrastructure), which generally designates a
+set of trusted entities that provide a measure of absolute trust.
+
+Additionally, while most packages are signed today, the files inside
+the packages (for instance, the executables), tend to be unsigned. This
+makes it difficult to utilize IPE in systems where a package manager is
+expected to be functional, without major changes to the package manager
+and ecosystem behind it.
+
+DIGLIM [#diglim]_ is a system that when combined with IPE, could be used to
+enable and support general-purpose computing use cases.
+
+Known Limitations
+-----------------
+
+IPE cannot verify the integrity of anonymous executable memory, such as
+the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code.
+Unfortunately, as this is dynamically generated code, there is no way
+for IPE to ensure the integrity of this code to form a trust basis. In all
+cases, the return result for these operations will be whatever the admin
+configures as the ``DEFAULT`` action for ``EXECUTE``.
+
+IPE cannot verify the integrity of programs written in interpreted
+languages when these scripts are invoked by passing these program files
+to the interpreter. This is because the way interpreters execute these
+files; the scripts themselves are not evaluated as executable code
+through one of IPE's hooks, but they are merely text files that are read
+(as opposed to compiled executables) [#interpreters]_.
+
+Threat Model
+------------
+
+The threat type addressed by IPE is tampering of executable userspace
+code beyond the initially booted kernel, and the initial verification of
+kernel modules that are loaded in userspace through ``modprobe`` or
+``insmod``.
+
+A bare-minimum example of a threat that should be mitigated by IPE, is
+an untrusted (potentially malicious) binary that is downloaded and
+bundled with all required dependencies (including a loader, libc, etc).
+With IPE, this binary should not be allowed to be executed, not even any
+of its dependencies.
+
+Tampering violates integrity, yet lack of trust is caused by being
+unable to detect tampering (and by extent verifying the integrity).
+IPE's role in mitigating this threat is to verify the integrity (and
+authenticity) of all executable code and to deny their use if they
+cannot be trusted (as integrity verification fails, or the authorization
+check fails against the reference value in the policy). IPE generates
+audit logs which may be utilized to detect and analyze failures
+resulting from policy violation.
+
+Tampering threat scenarios include modification or replacement of
+executable code by a range of actors including:
+
+- Actors with physical access to the hardware
+- Actors with local network access to the system
+- Actors with access to the deployment system
+- Compromised internal systems under external control
+- Malicious end users of the system
+- Compromised end users of the system
+- Remote (external) compromise of the system
+
+IPE does not mitigate threats arising from malicious but authorized
+developers (with access to a signing certificate), or compromised
+developer tools used by them (i.e. return-oriented programming attacks).
+Additionally, IPE draws hard security boundary between userspace and
+kernelspace. As a result, IPE does not provide any protections against a
+kernel level exploit, and a kernel-level exploit can disable or tamper
+with IPE's protections.
+
+Policy
+------
+
+IPE policy is a plain-text [#devdoc]_ policy composed of multiple statements
+over several lines. There is one required line, at the top of the
+policy, indicating the policy name, and the policy version, for
+instance::
+
+ policy_name=Ex_Policy policy_version=0.0.0
+
+The policy name is a unique key identifying this policy in a human
+readable name. This is used to create nodes under securityfs as well as
+uniquely identify policies to deploy new policies vs update existing
+policies.
+
+The policy version indicates the current version of the policy (NOT the
+policy syntax version). This is used to prevent rollback of policy to
+potentially insecure previous versions of the policy.
+
+The next portion of IPE policy are rules. Rules are formed by key=value
+pairs, known as properties. IPE rules require two properties: ``action``,
+which determines what IPE does when it encounters a match against the
+rule, and ``op``, which determines when the rule should be evaluated.
+The ordering is significant, a rule must start with ``op``, and end with
+``action``. Thus, a minimal rule is::
+
+ op=EXECUTE action=ALLOW
+
+This example will allow any execution. Additional properties are used to
+restrict attributes about the files being evaluated. These properties
+are intended to be descriptions of systems within the kernel that can
+provide a measure of integrity verification, such that IPE can determine
+the trust of the resource based on the value of the property.
+
+Rules are evaluated top-to-bottom. As a result, any revocation rules,
+or denies should be placed early in the file to ensure that these rules
+are evaluated before a rule with ``action=ALLOW``.
+
+IPE policy supports comments. The character '#' will function as a
+comment, ignoring all characters to the right of '#' until the newline.
+
+The default behavior of IPE evaluations can also be expressed in policy,
+through the ``DEFAULT`` statement. This can be done at a global level,
+or a per-operation level::
+
+ # Global
+ DEFAULT action=ALLOW
+
+ # Operation Specific
+ DEFAULT op=EXECUTE action=ALLOW
+
+A default must be set for all known operations in IPE. If you want to
+preserve older policies being compatible with newer kernels that can introduce
+new operations, set a global default of ``ALLOW``, then override the
+defaults on a per-operation basis (as above).
+
+With configurable policy-based LSMs, there's several issues with
+enforcing the configurable policies at startup, around reading and
+parsing the policy:
+
+1. The kernel *should* not read files from userspace, so directly reading
+ the policy file is prohibited.
+2. The kernel command line has a character limit, and one kernel module
+ should not reserve the entire character limit for its own
+ configuration.
+3. There are various boot loaders in the kernel ecosystem, so handing
+ off a memory block would be costly to maintain.
+
+As a result, IPE has addressed this problem through a concept of a "boot
+policy". A boot policy is a minimal policy which is compiled into the
+kernel. This policy is intended to get the system to a state where
+userspace is set up and ready to receive commands, at which point a more
+complex policy can be deployed via securityfs. The boot policy can be
+specified via ``SECURITY_IPE_BOOT_POLICY`` config option, which accepts
+a path to a plain-text version of the IPE policy to apply. This policy
+will be compiled into the kernel. If not specified, IPE will be disabled
+until a policy is deployed and activated through securityfs.
+
+Deploying Policies
+~~~~~~~~~~~~~~~~~~
+
+Policies can be deployed from userspace through securityfs. These policies
+are signed through the PKCS#7 message format to enforce some level of
+authorization of the policies (prohibiting an attacker from gaining
+unconstrained root, and deploying an "allow all" policy). These
+policies must be signed by a certificate that chains to the
+``SYSTEM_TRUSTED_KEYRING``. With openssl, the policy can be signed by::
+
+ openssl smime -sign \
+ -in "$MY_POLICY" \
+ -signer "$MY_CERTIFICATE" \
+ -inkey "$MY_PRIVATE_KEY" \
+ -noattr \
+ -nodetach \
+ -nosmimecap \
+ -outform der \
+ -out "$MY_POLICY.p7b"
+
+Deploying the policies is done through securityfs, through the
+``new_policy`` node. To deploy a policy, simply cat the file into the
+securityfs node::
+
+ cat "$MY_POLICY.p7b" > /sys/kernel/security/ipe/new_policy
+
+Upon success, this will create one subdirectory under
+``/sys/kernel/security/ipe/policies/``. The subdirectory will be the
+``policy_name`` field of the policy deployed, so for the example above,
+the directory will be ``/sys/kernel/security/ipe/policies/Ex_Policy``.
+Within this directory, there will be five files: ``pkcs7``, ``policy``,
+``active``, ``update``, and ``delete``.
+
+The ``pkcs7`` file is read-only. Reading it returns the raw PKCS#7 data
+that was provided to the kernel, representing the policy. If the policy being
+read is the boot policy, this will return ``ENOENT``, as it is not signed.
+
+The ``policy`` file is read only. Reading it returns the PKCS#7 inner
+content of the policy, which will be the plain text policy.
+
+The ``active`` file is used to set a policy as the currently active policy.
+This file is rw, and accepts a value of ``"1"`` to set the policy as active.
+Since only a single policy can be active at one time, all other policies
+will be marked inactive. The policy being marked active must have a policy
+version greater or equal to the currently-running version.
+
+The ``update`` file is used to update a policy that is already present
+in the kernel. This file is write-only and accepts a PKCS#7 signed
+policy. Two checks will always be performed on this policy: First, the
+``policy_names`` must match with the updated version and the existing
+version. Second the updated policy must have a policy version greater than
+or equal to the currently-running version. This is to prevent rollback attacks.
+
+The ``delete`` file is used to remove a policy that is no longer needed.
+This file is write-only and accepts a value of ``1`` to delete the policy.
+On deletion, the securityfs node representing the policy will be removed.
+However, delete the current active policy is not allowed and will return
+an operation not permitted error.
+
+Similarly, writing to both ``update`` and ``new_policy`` could result in
+bad message(policy syntax error) or file exists error. The latter error happens
+when trying to deploy a policy with a ``policy_name`` while the kernel already
+has a deployed policy with the same ``policy_name``.
+
+Deploying a policy will *not* cause IPE to start enforcing the policy. IPE will
+only enforce the policy marked active. Note that only one policy can be active
+at a time.
+
+Once deployment is successful, the policy can be activated, by writing file
+``/sys/kernel/security/ipe/$policy_name/active``.
+For example, the ``Ex_Policy`` can be activated by::
+
+ echo 1 > "/sys/kernel/security/ipe/Ex_Policy/active"
+
+From above point on, ``Ex_Policy`` is now the enforced policy on the
+system.
+
+IPE also provides a way to delete policies. This can be done via the
+``delete`` securityfs node, ``/sys/kernel/security/ipe/$policy_name/delete``.
+Writing ``1`` to that file deletes the policy::
+
+ echo 1 > "/sys/kernel/security/ipe/$policy_name/delete"
+
+There is only one requirement to delete a policy: the policy being deleted
+must be inactive.
+
+.. NOTE::
+
+ If a traditional MAC system is enabled (SELinux, apparmor, smack), all
+ writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``.
+
+Modes
+~~~~~
+
+IPE supports two modes of operation: permissive (similar to SELinux's
+permissive mode) and enforced. In permissive mode, all events are
+checked and policy violations are logged, but the policy is not really
+enforced. This allows users to test policies before enforcing them.
+
+The default mode is enforce, and can be changed via the kernel command
+line parameter ``ipe.enforce=(0|1)``, or the securityfs node
+``/sys/kernel/security/ipe/enforce``.
+
+.. NOTE::
+
+ If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera),
+ all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``.
+
+Audit Events
+~~~~~~~~~~~~
+
+1420 AUDIT_IPE_ACCESS
+^^^^^^^^^^^^^^^^^^^^^
+Event Examples::
+
+ type=1420 audit(1653364370.067:61): path="/root/fs/rw/plain/execve" dev="vdc1" ino=16 rule="DEFAULT op=EXECUTE action=DENY"
+ type=1300 audit(1653364370.067:61): arch=c000003e syscall=10 success=no exit=-13 a0=7f0bf0644000 a1=4f80 a2=5 a3=7f0bf043d300 items=0 ppid=455 pid=737 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=3 comm="mprotect" exe="/root/host/mprotect" subj=kernel key=(null)
+ type=1327 audit(1653364370.067:61): proctitle=686F73742F6D70726F7465637400534800527C5700527C5800706C61696E2F657865637665
+
+ type=1420 audit(1653364735.161:64): rule="DEFAULT op=EXECUTE action=DENY"
+ type=1300 audit(1653364735.161:64): arch=c000003e syscall=9 success=no exit=-13 a0=0 a1=1000 a2=4 a3=20 items=0 ppid=455 pid=774 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=3 comm="mmap" exe="/root/host/mmap" subj=kernel key=(null)
+ type=1327 audit(1653364735.161:64): proctitle=686F73742F6D6D617000410058⏎
+
+This event indicates that IPE made an access control decision; the IPE
+specific record (1420) is always emitted in conjunction with a
+``AUDITSYSCALL`` record.
+
+Determining whether IPE is in permissive or enforced mode can be derived
+from ``success`` property and exit code of the ``AUDITSYSCALL`` record.
+
+
+Field descriptions:
+
++-------+------------+-----------+-------------------------------------------------+
+| Field | Value Type | Optional? | Description of Value |
++=======+============+===========+=================================================+
+| path | string | Yes | The absolute path to the evaluated file |
++-------+------------+-----------+-------------------------------------------------+
+| ino | integer | Yes | The inode number of the evaluated file |
++-------+------------+-----------+-------------------------------------------------+
+| dev | string | Yes | The device name of the evaluated file, e.g. vda |
++-------+------------+-----------+-------------------------------------------------+
+| rule | string | No | The matched policy rule |
++-------+------------+-----------+-------------------------------------------------+
+
+1421 AUDIT_IPE_CONFIG_CHANGE
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Event Example::
+
+ type=1421 audit(1653425583.136:54): old_active_pol_name="Allow_All" old_active_pol_version=0.0.0 old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855 new_active_pol_name="boot_verified" new_active_pol_version=0.0.0 new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB auid=4294967295 ses=4294967295 lsm=ipe res=1
+ type=1300 audit(1653425583.136:54): SYSCALL arch=c000003e syscall=1 success=yes exit=2 a0=3 a1=5596fcae1fb0 a2=2 a3=2 items=0 ppid=184 pid=229 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=4294967295 comm="python3" exe="/usr/bin/python3.10" key=(null)
+ type=1327 audit(1653425583.136:54): PROCTITLE proctitle=707974686F6E3300746573742F6D61696E2E7079002D66002E2
+
+This event indicates that IPE switched the active poliy from one to another
+along with the version and the hash digest of the two policies.
+Note IPE can only have one policy active at a time, all access decision
+evaluation is based on the current active policy.
+The normal procedure to deploy a new policy is loading the policy to deploy
+into the kernel first, then switch the active policy to it.
+
+This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall.
+
++------------------------+------------+-----------+---------------------------------------------------+
+| Field | Value Type | Optional? | Description of Value |
++========================+============+===========+===================================================+
+| old_active_pol_name | string | No | The name of previous active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| old_active_pol_version | string | No | The version of previous active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| old_policy_digest | string | No | The hash of previous active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| new_active_pol_name | string | No | The name of current active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| new_active_pol_version | string | No | The version of current active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| new_policy_digest | string | No | The hash of current active policy |
++------------------------+------------+-----------+---------------------------------------------------+
+| auid | integer | No | The login user ID |
++------------------------+------------+-----------+---------------------------------------------------+
+| ses | integer | No | The login session ID |
++------------------------+------------+-----------+---------------------------------------------------+
+| lsm | string | No | The lsm name associated with the event |
++------------------------+------------+-----------+---------------------------------------------------+
+| res | integer | No | The result of the audited operation(success/fail) |
++------------------------+------------+-----------+---------------------------------------------------+
+
+1422 AUDIT_IPE_POLICY_LOAD
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Event Example::
+
+ type=1422 audit(1653425529.927:53): policy_name="boot_verified" policy_version=0.0.0 policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB auid=4294967295 ses=4294967295 lsm=ipe res=1
+ type=1300 audit(1653425529.927:53): arch=c000003e syscall=1 success=yes exit=2567 a0=3 a1=5596fcae1fb0 a2=a07 a3=2 items=0 ppid=184 pid=229 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=4294967295 comm="python3" exe="/usr/bin/python3.10" key=(null)
+ type=1327 audit(1653425529.927:53): PROCTITLE proctitle=707974686F6E3300746573742F6D61696E2E7079002D66002E2E
+
+This record indicates a new policy has been loaded into the kernel with the policy name, policy version and policy hash.
+
+This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall.
+
++----------------+------------+-----------+---------------------------------------------------+
+| Field | Value Type | Optional? | Description of Value |
++================+============+===========+===================================================+
+| policy_name | string | No | The policy_name |
++----------------+------------+-----------+---------------------------------------------------+
+| policy_version | string | No | The policy_version |
++----------------+------------+-----------+---------------------------------------------------+
+| policy_digest | string | No | The policy hash |
++----------------+------------+-----------+---------------------------------------------------+
+| auid | integer | No | The login user ID |
++----------------+------------+-----------+---------------------------------------------------+
+| ses | integer | No | The login session ID |
++----------------+------------+-----------+---------------------------------------------------+
+| lsm | string | No | The lsm name associated with the event |
++----------------+------------+-----------+---------------------------------------------------+
+| res | integer | No | The result of the audited operation(success/fail) |
++----------------+------------+-----------+---------------------------------------------------+
+
+
+1404 AUDIT_MAC_STATUS
+^^^^^^^^^^^^^^^^^^^^^
+
+Event Examples::
+
+ type=1404 audit(1653425689.008:55): enforcing=0 old_enforcing=1 auid=4294967295 ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
+ type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=)
+ type=1327 audit(1653425689.008:55): proctitle="-bash"
+
+ type=1404 audit(1653425689.008:55): enforcing=1 old_enforcing=0 auid=4294967295 ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
+ type=1300 audit(1653425689.008:55): arch=c000003e syscall=1 success=yes exit=2 a0=1 a1=55c1065e5c60 a2=2 a3=0 items=0 ppid=405 pid=441 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=)
+ type=1327 audit(1653425689.008:55): proctitle="-bash"
+
+This record will always be emitted in conjunction with a ``AUDITSYSCALL`` record for the ``write`` syscall.
+
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| Field | Value Type | Optional? | Description of Value | |
++===============+============+===========+=================================================================================================+=====+
+| enforcing | integer | No | The enforcing state IPE is being switched to, 1 is in enforcing mode, 0 is in permissive mode | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| old_enforcing | integer | No | The enforcing state IPE is being switched from, 1 is in enforcing mode, 0 is in permissive mode | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| auid | integer | No | The login user ID | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| ses | integer | No | The login session ID | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| enabled | integer | No | The new TTY audit enabled setting | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| old-enabled | integer | No | The old TTY audit enabled setting | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| lsm | string | No | The lsm name associated with the event | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+| res | integer | No | The result of the audited operation(success/fail) | |
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+-----+
+
+Success Auditing
+^^^^^^^^^^^^^^^^
+
+IPE supports success auditing. When enabled, all events that pass IPE
+policy and are not blocked will emit an audit event. This is disabled by
+default, and can be enabled via the kernel command line
+``ipe.success_audit=(0|1)`` or
+``/sys/kernel/security/ipe/success_audit`` securityfs file.
+
+This is *very* noisy, as IPE will check every userspace binary on the
+system, but is useful for debugging policies.
+
+.. NOTE::
+
+ If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera),
+ all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``.
+
+Properties
+----------
+
+As explained above, IPE properties are ``key=value`` pairs expressed in
+IPE policy. Two properties are built-into the policy parser: 'op' and
+'action'. The other properties are deterministic attributes to express
+across files. Currently those properties are: '``boot_verified``',
+'``dmverity_signature``', '``dmverity_roothash``', '``fsverity_signature``',
+'``fsverity_digest``'. A description of all properties supported by IPE
+are listed below:
+
+op
+~~
+
+Indicates the operation for a rule to apply to. Must be in every rule,
+as the first token. IPE supports the following operations:
+
+ ``EXECUTE``
+
+ Pertains to any file attempting to be executed, or loaded as an
+ executable.
+
+ ``FIRMWARE``:
+
+ Pertains to firmware being loaded via the firmware_class interface.
+ This covers both the preallocated buffer and the firmware file
+ itself.
+
+ ``KMODULE``:
+
+ Pertains to loading kernel modules via ``modprobe`` or ``insmod``.
+
+ ``KEXEC_IMAGE``:
+
+ Pertains to kernel images loading via ``kexec``.
+
+ ``KEXEC_INITRAMFS``
+
+ Pertains to initrd images loading via ``kexec --initrd``.
+
+ ``POLICY``:
+
+ Controls loading policies via reading a kernel-space initiated read.
+
+ An example of such is loading IMA policies by writing the path
+ to the policy file to ``$securityfs/ima/policy``
+
+ ``X509_CERT``:
+
+ Controls loading IMA certificates through the Kconfigs,
+ ``CONFIG_IMA_X509_PATH`` and ``CONFIG_EVM_X509_PATH``.
+
+action
+~~~~~~
+
+ Determines what IPE should do when a rule matches. Must be in every
+ rule, as the final clause. Can be one of:
+
+ ``ALLOW``:
+
+ If the rule matches, explicitly allow access to the resource to proceed
+ without executing any more rules.
+
+ ``DENY``:
+
+ If the rule matches, explicitly prohibit access to the resource to
+ proceed without executing any more rules.
+
+boot_verified
+~~~~~~~~~~~~~
+
+ This property can be utilized for authorization of the first super-block
+ that executes a file. This is almost always init. Typically this is used
+ for systems with an initramfs or other initial disk, where this is unmounted
+ before the system becomes available, and is not covered by any other property.
+ The format of this property is::
+
+ boot_verified=(TRUE|FALSE)
+
+
+ .. WARNING::
+
+ This property will trust any disk where the first execution evaluation
+ occurs. If you do *NOT* have a startup disk that is unpacked and unmounted
+ (like initramfs), then it will automatically trust the root filesystem and
+ potentially overauthorize the entire disk.
+
+dmverity_roothash
+~~~~~~~~~~~~~~~~~
+
+ This property can be utilized for authorization or revocation of
+ specific dm-verity volumes, identified via sroot hash. It has a
+ dependency on the DM_VERITY module. This property is controlled by
+ the ``IPE_PROP_DM_VERITY`` config option, it will be automatically
+ selected when ``IPE_SECURITY``, ``DM_VERITY `` and
+ ``DM_VERITY_VERIFY_ROOTHASH_SIG`` are all enabled.
+ The format of this property is::
+
+ dmverity_roothash=DigestName:HexadecimalString
+
+ The supported DigestNames for dmverity_roothash are [#dmveritydigests]_ [#securedigest]_ :
+
+ + blake2b-512
+ + blake2s-256
+ + sha1
+ + sha256
+ + sha384
+ + sha512
+ + sha3-224
+ + sha3-256
+ + sha3-384
+ + sha3-512
+ + md4
+ + md5
+ + sm3
+ + rmd160
+
+dmverity_signature
+~~~~~~~~~~~~~~~~~~
+
+ This property can be utilized for authorization of all dm-verity
+ volumes that have a signed roothash that chains to a keyring
+ specified by dm-verity's configuration, either the system trusted
+ keyring, or the secondary keyring. It depends on
+ ``DM_VERITY_VERIFY_ROOTHASH_SIG`` config option and is controlled by
+ the ``IPE_PROP_DM_VERITY`` config option, it will be automatically
+ selected when ``IPE_SECURITY``, ``DM_VERITY `` and
+ ``DM_VERITY_VERIFY_ROOTHASH_SIG`` are all enabled.
+ The format of this property is::
+
+ dmverity_signature=(TRUE|FALSE)
+
+fsverity_digest
+~~~~~~~~~~~~~~~
+
+ This property can be utilized for authorization or revocation of
+ specific fsverity enabled file, identified via its fsverity digest.
+ It depends on ``FS_VERITY`` config option and is controlled by
+ ``CONFIG_IPE_PROP_FS_VERITY``. The format of this property is::
+
+ fsverity_digest=DigestName:HexadecimalString
+
+ The supported DigestNames for dmverity_roothash are [#fsveritydigest] [#securedigest]_ :
+
+ + sha256
+ + sha512
+
+fsverity_signature
+~~~~~~~~~~~~~~~~~~
+
+ This property can be utilized for authorization of all fsverity
+ enabled files that is verified by fsverity. The keyring that the
+ signature is verified against is subject to fsverity's configuration,
+ typically the fsverity keyring. It depends on
+ ``CONFIG_FS_VERITY_BUILTIN_SIGNATURES`` and it is controlled by
+ the Kconfig ``CONFIG_IPE_PROP_FS_VERITY``. The format of this
+ property is::
+
+ fsverity_signature=(TRUE|FALSE)
+
+Policy Examples
+---------------
+
+Allow all
+~~~~~~~~~
+
+::
+
+ policy_name=Allow_All policy_version=0.0.0
+ DEFAULT action=ALLOW
+
+Allow only initial superblock
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=Allow_All_Initial_SB policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE boot_verified=TRUE action=ALLOW
+
+Allow any signed dm-verity volume and the initial superblock
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=AllowSignedAndInitial policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE boot_verified=TRUE action=ALLOW
+ op=EXECUTE dmverity_signature=TRUE action=ALLOW
+
+Prohibit execution from a specific dm-verity volume
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=AllowSignedAndInitial policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE dmverity_roothash=sha256:cd2c5bae7c6c579edaae4353049d58eb5f2e8be0244bf05345bc8e5ed257baff action=DENY
+
+ op=EXECUTE boot_verified=TRUE action=ALLOW
+ op=EXECUTE dmverity_signature=TRUE action=ALLOW
+
+Allow only a specific dm-verity volume
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=AllowSignedAndInitial policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=ALLOW
+
+Allow any signed fs-verity file
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=AllowSignedFSVerity policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE fsverity_signature=TRUE action=ALLOW
+
+Prohibit execution of a specific fs-verity file
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=ProhibitSpecificFSVF policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE fsverity_digest=sha256:fd88f2b8824e197f850bf4c5109bea5cf0ee38104f710843bb72da796ba5af9e action=DENY
+ op=EXECUTE boot_verified=TRUE action=ALLOW
+ op=EXECUTE dmverity_signature=TRUE action=ALLOW
+
+Additional Information
+----------------------
+
+- `Github Repository <https://github.com/microsoft/ipe>`_
+- `Design Documentation </security/ipe>`_
+
+FAQ
+---
+
+Q:
+ What's the difference between other LSMs which provide a measure of
+ trust-based access control?
+
+A:
+
+ In general, there's two other LSMs that can provide similar functionality:
+ IMA, and Loadpin.
+
+ IMA and IPE are functionally very similar. The significant difference between
+ the two is the policy. [#devdoc]_
+
+ Loadpin and IPE differ fairly dramatically, as Loadpin controls only the IPE
+ equivalent of ``KERNEL_READ``, whereas IPE is capable of controlling execution,
+ on top of ``KERNEL_READ``. The trust model is also different; Loadpin roots its
+ trust in the initial super-block, whereas trust in IPE is stemmed from kernel
+ itself (via ``SYSTEM_TRUSTED_KEYS``).
+
+-----------
+
+.. [#diglim] 1: https://lore.kernel.org/bpf/[email protected]/T/
+
+.. [#interpreters] There is `some interest in solving this issue <https://lore.kernel.org/lkml/[email protected]/>`_.
+
+.. [#devdoc] Please see `Documentation/security/ipe.rst` for more on this topic.
+
+.. [#fsveritydigest] These hash algorithms are based on values accepted by fsverity-utils;
+ IPE does not impose any restrictions on the digest algorithm itself;
+ thus, this list may be out of date.
+
+.. [#dmveritydigests] These hash algorithms are based on values accepted by dm-verity,
+ specifically ``crypto_alloc_ahash`` in ``verity_ctr``; ``veritysetup``
+ does support more algorithms than the list above. IPE does not impose
+ any restrictions on the digest algorithm itself; thus, this list
+ may be out of date.
+
+.. [#securedigest] Please ensure you are using cryptographically secure hash functions;
+ just because something is *supported* does not mean it is *secure*.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0a1731a0f0ef..6a71d9d9be36 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2262,6 +2262,18 @@
ipcmni_extend [KNL] Extend the maximum number of unique System V
IPC identifiers from 32,768 to 16,777,216.
+ ipe.enforce= [IPE]
+ Format: <bool>
+ Determine whether IPE starts in permissive (0) or
+ enforce (1) mode. The default is enforce.
+
+ ipe.success_audit=
+ [IPE]
+ Format: <bool>
+ Start IPE with success auditing enabled, emitting
+ an audit event when a binary is allowed. The default
+ is 0.
+
irqaffinity= [SMP] Set the default irq affinity mask
The argument is a cpu list, as described above.
diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst
index 6ed8d2fa6f9e..a5248d4fd510 100644
--- a/Documentation/security/index.rst
+++ b/Documentation/security/index.rst
@@ -18,3 +18,4 @@ Security Documentation
digsig
landlock
secrets/index
+ ipe
diff --git a/Documentation/security/ipe.rst b/Documentation/security/ipe.rst
new file mode 100644
index 000000000000..6a47a2ab5e39
--- /dev/null
+++ b/Documentation/security/ipe.rst
@@ -0,0 +1,420 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Integrity Policy Enforcement (IPE) - Kernel Documentation
+=========================================================
+
+.. NOTE::
+
+ This is documentation targeted at developers, instead of administrators.
+ If you're looking for documentation on the usage of IPE, please see
+ `Documentation/admin-guide/LSM/ipe.rst`
+
+Historical Motivation
+---------------------
+
+The original issue that prompted IPE's implementation was the creation
+of a locked-down system. This system would be born-secure, and have
+strong integrity guarantees over both the executable code, and specific
+*data files* on the system, that were critical to its function. These
+specific data files would not be readable unless they passed integrity
+policy. A mandatory access control system would be present, and
+as a result, xattrs would have to be protected. This lead to a selection
+of what would provide the integrity claims. At the time, there were two
+main mechanisms considered that could guarantee integrity for the system
+with these requirements:
+
+ 1. IMA + EVM Signatures
+ 2. DM-Verity
+
+Both options were carefully considered, however the choice to use DM-Verity
+over IMA+EVM as the *integrity mechanism* in the original use case of IPE
+was due to three main reasons:
+
+ 1. Protection of additional attack vectors:
+
+ * With IMA+EVM, without an encryption solution, the system is vulnerable
+ to offline attack against the aforemetioned specific data files.
+
+ Unlike executables, read operations (like those on the protected data
+ files), cannot be enforced to be globally integrtiy verified. This means
+ there must be some form of selector to determine whether a read should
+ enforce the integrity policy, or it should not.
+
+ At the time, this was done with mandatory access control labels. An IMA
+ policy would indicate what labels required integrity verification, which
+ presented an issue: EVM would protect the label, but if an attacker could
+ modify filesystem offline, the attacker could wipe all the xattrs -
+ including the SELinux labels that would be used to determine whether the
+ file should be subject to integrity policy.
+
+ With DM-Verity, as the xattrs are saved as part of the merkel tree, if
+ offline mount occurs against the filesystem protected by dm-verity, the
+ checksum no longer matches and the file fails to be read.
+
+ * As userspace binaries are paged in Linux, dm-verity also offers the
+ additional protection against a hostile block device. In such an attack,
+ the block device reports the appropriate content for the IMA hash
+ initially, passing the required integrity check. Then, on the page fault
+ that accesses the real data, will report the attacker's payload. Since
+ dm-verity will check the data when the page fault occurs (and the disk
+ access), this attack is mitigated.
+
+ 2. Performance:
+
+ * dm-verity provides integrity verification on demand as blocks are
+ read versus requiring the entire file being read into memory for
+ validation.
+
+ 3. Simplicity of signing:
+
+ * No need for two signatures (IMA, then EVM): one signature covers
+ an entire block device.
+ * Signatures can be stored externally to the filesystem metadata.
+ * The signature supports an x.509-based signing infrastructure.
+
+The next step was to choose a *policy* to enforce the integrity mechanism.
+The minimum requirements for the policy were:
+
+ 1. The policy itself must be integrity verified (preventing trivial
+ attack against it).
+ 2. The policy itself must be resistant to rollback attacks.
+ 3. The policy enforcement must have a permissive-like mode.
+ 4. The policy must be able to be updated, in its entirety, without
+ a reboot.
+ 5. Policy updates must be atomic.
+ 6. The policy must support *revocations* of previously authored
+ components.
+ 7. The policy must be auditable, at any point-of-time.
+
+IMA, as the only integrity policy mechanism at the time, was
+considered against these list of requirements, and did not fulfill
+all of the minimum requirements. Extending IMA to cover these
+requirements was considered, but ultimately discarded for a
+two reasons:
+
+ 1. Regression risk; many of these changes would result in
+ dramatic code changes to IMA, which is already present in the
+ kernel, and therefore might impact users.
+
+ 2. IMA was used in the system for measurement and attestation;
+ separation of measurement policy from local integrity policy
+ enforcement was considered favorable.
+
+Due to these reasons, it was decided that a new LSM should be created,
+whose responsibility would be only the local integrity policy enforcement.
+
+Role and Scope
+--------------
+
+IPE, as its name implies, is fundamentally an integrity policy enforcement
+solution; IPE does not mandate how integrity is provided, but instead
+leaves that decision to the system administrator to set the security bar,
+via the mechanisms that they select that suit their individual needs.
+There are several different integrity solutions that provide a different
+level of security guarantees; and IPE allows sysadmins to express policy for
+theoretically all of them.
+
+IPE does not have an inherent mechanism to ensure integrity on its own.
+Instead, there are more effective layers available for building systems that
+can guarantee integrity. It's important to note that the mechanism for proving
+integrity is independent of the policy for enforcing that integrity claim.
+
+Therefore, IPE was designed around:
+
+ 1. Easy integrations with integrity providers.
+ 2. Ease of use for platform administrators/sysadmins.
+
+Design Rationale:
+-----------------
+
+IPE was designed after evaluating existing integrity policy solutions
+in other operating systems and environments. In this survey of other
+implementations, there were a few pitfalls identified:
+
+ 1. Policies were not readable by humans, usually requiring a binary
+ intermediary format.
+ 2. A single, non-customizable action was implicitly taken as a default.
+ 3. Debugging the policy required manual steps to determine what rule was violated.
+ 4. Authoring a policy required an in-depth knowledge of the larger system,
+ or operating system.
+
+IPE attempts to avoid all of these pitfalls.
+
+Policy
+~~~~~~
+
+Plain Text
+^^^^^^^^^^
+
+IPE's policy is plain-text. This introduces slightly larger policy files than
+other LSMs, but solves two major problems that occurs with some integrity policy
+solutions on other platforms.
+
+The first issue is one of code maintenance and duplication. To author policies,
+the policy has to be some form of string representation (be it structured,
+through XML, JSON, YAML, etcetera), to allow the policy author to understand
+what is being written. In a hypothetical binary policy design, a serializer
+is necessary to write the policy from the human readable form, to the binary
+form, and a deserializer is needed to interpret the binary form into a data
+structure in the kernel.
+
+Eventually, another deserializer will be needed to transform the binary from
+back into the human-readable form with as much information preserved. This is because a
+user of this access control system will have to keep a lookup table of a checksum
+and the original file itself to try to understand what policies have been deployed
+on this system and what policies have not. For a single user, this may be alright,
+as old policies can be discarded almost immediately after the update takes hold.
+For users that manage computer fleets in the thousands, if not hundreds of thousands,
+with multiple different operating systems, and multiple different operational needs,
+this quickly becomes an issue, as stale policies from years ago may be present,
+quickly resulting in the need to recover the policy or fund extensive infrastructure
+to track what each policy contains.
+
+With now three separate serializer/deserializers, maintenance becomes costly. If the
+policy avoids the binary format, there is only one required serializer: from the
+human-readable form to the data structure in kernel, saving on code maintenance,
+and retaining operability.
+
+The second issue with a binary format is one of transparency. As IPE controls
+access based on the trust of the system's resources, it's policy must also be
+trusted to be changed. This is done through signatures, resulting in needing
+signing as a process. Signing, as a process, is typically done with a
+high security bar, as anything signed can be used to attack integrity
+enforcement systems. It is also important that, when signing something, that
+the signer is aware of what they are signing. A binary policy can cause
+obfuscation of that fact; what signers see is an opaque binary blob. A
+plain-text policy, on the other hand, the signers see the actual policy
+submitted for signing.
+
+Boot Policy
+~~~~~~~~~~~
+
+IPE, if configured appropriately, is able to enforce a policy as soon as a
+kernel is booted and usermode starts. That implies some level of storage
+of the policy to apply the minute usermode starts. Generally, that storage
+can be handled in one of three ways:
+
+ 1. The policy file(s) live on disk and the kernel loads the policy prior
+ to an code path that would result in an enforcement decision.
+ 2. The policy file(s) are passed by the bootloader to the kernel, who
+ parses the policy.
+ 3. There is a policy file that is compiled into the kernel that is
+ parsed and enforced on initialization.
+
+The first option has problems: the kernel reading files from userspace
+is typically discouraged and very uncommon in the kernel.
+
+The second option also has problems: Linux supports a variety of bootloaders
+across its entire ecosystem - every bootloader would have to support this
+new methodology or there must be an independent source. It would likely
+result in more drastic changes to the kernel startup than necessary.
+
+The third option is the best but it's important to be aware that the policy
+will take disk space against the kernel it's compiled in. It's important to
+keep this policy generalized enough that userspace can load a new, more
+complicated policy, but restrictive enough that it will not overauthorize
+and cause security issues.
+
+The initramfs provides a way that this bootup path can be established. The
+kernel starts with a minimal policy, that trusts the initramfs only. Inside
+the initramfs, when the real rootfs is mounted, but not yet transferred to,
+it deploys and activates a policy that trusts the new root filesystem.
+This prevents overauthorization at any step, and keeps the kernel policy
+to a minimal size.
+
+Startup
+^^^^^^^
+
+Not every system, however starts with an initramfs, so the startup policy
+compiled into the kernel will need some flexibility to express how trust
+is established for the next phase of the bootup. To this end, if we just
+make the compiled-in policy a full IPE policy, it allows system builders
+to express the first stage bootup requirements appropriately.
+
+Updatable, Rebootless Policy
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+As requirements change over time (vulnerabilities are found in previously
+trusted applications, keys roll, etcetera). Updating a kernel to change the
+meet those security goals is not always a suitable option, as updates are not
+always risk-free, and blocking a security update leaves systems vulnerable.
+This means IPE requires a policy that can be completely updated (allowing
+revocations of existing policy) from a source external to the kernel (allowing
+policies to be updated without updating the kernel).
+
+Additionally, since the kernel is stateless between invocations, and reading
+policy files off the disk from kernel space is a bad idea(tm), then the
+policy updates have to be done rebootlessly.
+
+To allow an update from an external source, it could be potentially malicious,
+so this policy needs to have a way to be identified as trusted. This is
+done via a signature chained to a trust source in the kernel. Arbitrarily,
+this is the ``SYSTEM_TRUSTED_KEYRING``, a keyring that is initially
+populated at kernel compile-time, as this matches the expectation that the
+author of the compiled-in policy described above is the same entity that can
+deploy policy updates.
+
+Anti-Rollback / Anti-Replay
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Over time, vulnerabilities are found and trusted resources may not be
+trusted anymore. IPE's policy has no exception to this. There can be
+instances where a mistaken policy author deploys an insecure policy,
+before correcting it with a secure policy.
+
+Assuming that as soon as the insecure policy is signed, and an attacker
+acquires the insecure policy, IPE needs a way to prevent rollback
+from the secure policy update to the insecure policy update.
+
+Initially, IPE's policy can have a policy_version that states the
+minimum required version across all policies that can be active on
+the system. This will prevent rollback while the system is live.
+
+.. WARNING::
+
+ However, since the kernel is stateless across boots, this policy
+ version will be reset to 0.0.0 on the next boot. System builders
+ need to be aware of this, and ensure the new secure policies are
+ deployed ASAP after a boot to ensure that the window of
+ opportunity is minimal for an attacker to deploy the insecure policy.
+
+Implicit Actions:
+~~~~~~~~~~~~~~~~~
+
+The issue of impicit actions only becomes visible when you consider
+a mixed level of security bars across multiple operations in a system.
+For example, consider a system that has strong integrity guarantees
+over both the executable code, and specific *data files* on the system,
+that were critical to its function. In this system, three types of policies
+are possible:
+
+ 1. A policy in which failure to match any rules in the policy results
+ in the action being denied.
+ 2. A policy in which failure to match any rules in the policy results
+ in the action being allowed.
+ 3. A policy in which the action taken when no rules are matched is
+ specified by the policy author.
+
+The first option could make a policy like this::
+
+ op=EXECUTE integrity_verified=YES action=ALLOW
+
+In the example system, this works well for the executables, as all
+executables should have integrity guarantees, without exception. The
+issue becomes with the second requirement about specific data files.
+This would result in a policy like this (assuming each line is
+evaluated in order)::
+
+ op=EXECUTE integrity_verified=YES action=ALLOW
+
+ op=READ integrity_verified=NO label=critical_t action=DENY
+ op=READ action=ALLOW
+
+This is somewhat clear if you read the docs, understand the policy
+is executed in order and that the default is a denial; however, the
+last line effectively changes that default to an ALLOW. This is
+required, because in a realistic system, there are some unverified
+reads (imagine appending to a log file).
+
+The second option, matching no rules results in an allow, is clearer
+for the specific data files::
+
+ op=READ integrity_verified=NO label=critical_t action=DENY
+
+And, like the first option, falls short with the opposite scenario,
+effectively needing to override the default::
+
+ op=EXECUTE integrity_verified=YES action=ALLOW
+ op=EXECUTE action=DENY
+
+ op=READ integrity_verified=NO label=critical_t action=DENY
+
+This leaves the third option. Instead of making users be clever
+and override the default with an empty rule, force the end-user
+to consider what the appropriate default should be for their
+scenario and explicitly state it::
+
+ DEFAULT op=EXECUTE action=DENY
+ op=EXECUTE integrity_verified=YES action=ALLOW
+
+ DEFAULT op=READ action=ALLOW
+ op=READ integrity_verified=NO label=critical_t action=DENY
+
+Policy Debugging:
+~~~~~~~~~~~~~~~~~
+
+When developing a policy, it is useful to know what line of the policy
+is being violated to reduce debugging costs; narrowing the scope of the
+investigation to the exact line that resulted in the action. Some integrity
+policy systems do not provide this information, instead providing the
+information that was used in the evaluation. This then requires a correlation
+with the policy to evaluate what went wrong.
+
+Instead, IPE just emits the rule that was matched. This limits the scope
+of the investigation to the exact policy line (in the case of a specific
+rule), or the section (in the case of a DEFAULT). This decreases iteration
+and investigation times when policy failures are observed while evaluating
+policies.
+
+IPE's policy engine is also designed in a way that it makes it obvious to
+a human of how to investigate a policy failure. Each line is evaluated in
+the sequence that is written, so the algorithm is very simple to follow
+for humans to recreate the steps and could have caused the failure. In other
+surveyed systems, optimizations occur (sorting rules, for instance) when loading
+the policy. In those systems, it requires multiple steps to debug, and the
+algorithm may not always be clear to the end-user without reading the code first.
+
+Simplified Policy:
+~~~~~~~~~~~~~~~~~~
+
+Finally, IPE's policy is designed for sysadmins, not kernel developers. Instead
+of covering individual LSM hooks (or syscalls), IPE covers operations. This means
+instead of sysadmins needing to know that the syscalls ``mmap``, ``mprotect``,
+``execve``, and ``uselib`` must have rules protecting them, they must simple know
+that they want to restrict code execution. This limits the amount of bypasses that
+could occur due to a lack of knowledge of the underlying system; whereas the
+maintainers of IPE, being kernel developers can make the correct choice to determine
+whether something maps to these operations, and under what conditions.
+
+Implementation Notes
+--------------------
+
+Anonymous Memory
+~~~~~~~~~~~~~~~~
+
+Anonymous memory isn't treated any differently from any other access in IPE.
+When anonymous memory is mapped with ``+X``, it still comes into the ``file_mmap``
+or ``file_mprotect`` hook, but with a ``NULL`` file object. This is submitted to
+the evaluation, like any other file, however, all current trust mechanisms will
+return false as there is nothing to evaluate. This means anonymous memory
+execution is subject to whatever the ``DEFAULT`` is for ``EXECUTE``.
+
+.. WARNING::
+
+ This also occurs with the ``kernel_load_data`` hook, which is used by signed
+ and compressed kernel modules. Using signed and compressed kernel modules with
+ IPE will always result in the ``DEFAULT`` action for ``KMODULE``.
+
+Securityfs Interface
+~~~~~~~~~~~~~~~~~~~~
+
+The per-policy securityfs tree is somewhat unique. For example, for
+a standard securityfs policy tree::
+
+ MyPolicy
+ |- active
+ |- delete
+ |- name
+ |- pkcs7
+ |- policy
+ |- update
+ |- version
+
+The policy is stored in the ``->i_private`` data of the MyPolicy inode.
+
+Tests
+-----
+
+IPE has KUnit Tests, testing primarily the parser. In addition, IPE has a
+python based integration test suits that can test both user interfaces and
+enforcement functionalities.
diff --git a/MAINTAINERS b/MAINTAINERS
index 18b1aeea6306..c62d546baf00 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10394,6 +10394,8 @@ M: Fan Wu <[email protected]>
L: [email protected]
S: Supported
T: git https://github.com/microsoft/ipe.git
+F: Documentation/admin-guide/LSM/ipe.rst
+F: Documentation/security/ipe.rst
F: scripts/ipe/
F: security/ipe/
--
2.25.1
From: Deven Bowers <[email protected]>
dm-verity provides a strong guarantee of a block device's integrity. As
a generic way to check the integrity of a block device, it provides
those integrity guarantees to its higher layers, including the filesystem
level.
An LSM that control access to a resource on the system based on the
available integrity claims can use this transitive property of
dm-verity, by querying the underlying block_device of a particular
file.
The digest and signature information need to be stored in the block
device to fulfill the next requirement of authorization via LSM policy.
This will enable the LSM to perform revocation of devices that are still
mounted, prohibiting execution of files that are no longer authorized
by the LSM in question.
This patch added two security hook calls in dm-verity to save the
dm-verity roothash and the roothash signature to the block device's
LSM blobs.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ No Changes
v3:
+ No changes
v4:
+ No changes
v5:
+ No changes
v6:
+ Fix an improper cleanup that can result in
a leak
v7:
+ Squash patch 08/12, 10/12 to [11/16]
+ Use part0 for block_device, to retrieve the block_device, when
calling security_bdev_setsecurity
v8:
+ Undo squash of 08/12, 10/12 - separating drivers/md/ from
security/ & block/
+ Use common-audit function for dmverity_signature.
+ Change implementation for storing the dm-verity digest to use the
newly introduced dm_verity_digest structure introduced in patch
14/20.
+ Create new structure, dm_verity_digest, containing digest algorithm,
size, and digest itself to pass to the LSM layer. V7 was missing the
algorithm.
+ Create an associated public header containing this new structure and
the key values for the LSM hook, specific to dm-verity.
+ Additional information added to commit, discussing the layering of
the changes and how the information passed will be used.
v9:
+ No changes
v10:
+ No changes
v11:
+ Add an optional field to save signature
+ Move the security hook call to the new finalize hook
---
drivers/md/dm-verity-target.c | 71 +++++++++++++++++++++++++++++++++++
drivers/md/dm-verity.h | 6 +++
include/linux/dm-verity.h | 19 ++++++++++
3 files changed, 96 insertions(+)
create mode 100644 include/linux/dm-verity.h
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 80673b66c194..db58b53649e3 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -13,6 +13,7 @@
* access behavior.
*/
+#include "dm-core.h"
#include "dm-verity.h"
#include "dm-verity-fec.h"
#include "dm-verity-verify-sig.h"
@@ -22,6 +23,9 @@
#include <linux/scatterlist.h>
#include <linux/string.h>
#include <linux/jump_label.h>
+#include <linux/security.h>
+#include <linux/dm-verity.h>
+#include <crypto/hash_info.h>
#define DM_MSG_PREFIX "verity"
@@ -952,6 +956,17 @@ static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
blk_limits_io_min(limits, limits->logical_block_size);
}
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+static void verity_free_sig(struct dm_verity *v)
+{
+ kfree(v->root_digest_sig);
+}
+#else
+static inline void verity_free_sig(struct dm_verity *v)
+{
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
static void verity_dtr(struct dm_target *ti)
{
struct dm_verity *v = ti->private;
@@ -966,6 +981,7 @@ static void verity_dtr(struct dm_target *ti)
kfree(v->salt);
kfree(v->root_digest);
kfree(v->zero_digest);
+ verity_free_sig(v);
if (v->tfm)
crypto_free_ahash(v->tfm);
@@ -1157,6 +1173,25 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
return r;
}
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+static int verity_init_sig(struct dm_verity *v, const void *sig,
+ size_t sig_size)
+{
+ v->sig_size = sig_size;
+ v->root_digest_sig = kmalloc(v->sig_size, GFP_KERNEL);
+ if (!v->root_digest)
+ return -ENOMEM;
+
+ return 0;
+}
+#else
+static inline int verity_init_sig(struct dm_verity *v, const void *sig,
+ size_t sig_size)
+{
+ return 0;
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
/*
* Target parameters:
* <version> The current format is version 1.
@@ -1365,6 +1400,13 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->error = "Root hash verification failed";
goto bad;
}
+
+ r = verity_init_sig(v, verify_args.sig, verify_args.sig_size);
+ if (r < 0) {
+ ti->error = "Cannot allocate root digest signature";
+ goto bad;
+ }
+
v->hash_per_block_bits =
__fls((1 << v->hash_dev_block_bits) / v->digest_size);
@@ -1501,6 +1543,32 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
return 0;
}
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+static int verity_finalize(struct dm_target *ti)
+{
+ struct block_device *bdev;
+ struct dm_verity_digest root_digest;
+ struct dm_verity *v;
+ int r;
+
+ v = ti->private;
+ bdev = dm_table_get_md(ti->table)->disk->part0;
+ root_digest.digest = v->root_digest;
+ root_digest.digest_len = v->digest_size;
+ root_digest.algo = v->alg_name;
+
+ r = security_bdev_setsecurity(bdev, DM_VERITY_ROOTHASH_SEC_NAME, &root_digest,
+ sizeof(root_digest));
+ if (r)
+ return r;
+
+ return security_bdev_setsecurity(bdev,
+ DM_VERITY_SIGNATURE_SEC_NAME,
+ v->root_digest_sig,
+ v->sig_size);
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
static struct target_type verity_target = {
.name = "verity",
.features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
@@ -1513,6 +1581,9 @@ static struct target_type verity_target = {
.prepare_ioctl = verity_prepare_ioctl,
.iterate_devices = verity_iterate_devices,
.io_hints = verity_io_hints,
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ .finalize = verity_finalize,
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
module_dm(verity);
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
index 2f555b420367..a093d4a54615 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -42,6 +42,9 @@ struct dm_verity {
u8 *root_digest; /* digest of the root block */
u8 *salt; /* salt: its size is salt_size */
u8 *zero_digest; /* digest for a zero block */
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ u8 *root_digest_sig; /* digest signature of the root block */
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
unsigned int salt_size;
sector_t data_start; /* data offset in 512-byte sectors */
sector_t hash_start; /* hash start in blocks */
@@ -55,6 +58,9 @@ struct dm_verity {
bool hash_failed:1; /* set if hash of any block failed */
bool use_tasklet:1; /* try to verify in tasklet before work-queue */
unsigned int digest_size; /* digest size for the current hash algorithm */
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ unsigned int sig_size; /* digest signature size */
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
unsigned int ahash_reqsize;/* the size of temporary space for crypto */
enum verity_mode mode; /* mode for handling verification errors */
unsigned int corrupted_errs;/* Number of errors for corrupted blocks */
diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
new file mode 100644
index 000000000000..bb0413d55d72
--- /dev/null
+++ b/include/linux/dm-verity.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_DM_VERITY_H
+#define _LINUX_DM_VERITY_H
+
+#include <linux/types.h>
+#include <crypto/hash_info.h>
+#include <linux/device-mapper.h>
+
+struct dm_verity_digest {
+ const char *algo;
+ const u8 *digest;
+ size_t digest_len;
+};
+
+#define DM_VERITY_SIGNATURE_SEC_NAME DM_NAME ".verity-signature"
+#define DM_VERITY_ROOTHASH_SEC_NAME DM_NAME ".verity-roothash"
+
+#endif /* _LINUX_DM_VERITY_H */
--
2.25.1
From: Deven Bowers <[email protected]>
Integrity Policy Enforcement (IPE) is an LSM that provides an
complimentary approach to Mandatory Access Control than existing LSMs
today.
Existing LSMs have centered around the concept of access to a resource
should be controlled by the current user's credentials. IPE's approach,
is that access to a resource should be controlled by the system's trust
of a current resource.
The basis of this approach is defining a global policy to specify which
resource can be trusted.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks,
and evaluation loop from policy parser and userspace
interface to pass mailing list character limit
v3:
+ Move ipe_load_properties to patch 04.
+ Remove useless 0-initializations
+ Prefix extern variables with ipe_
+ Remove kernel module parameters, as these are
exposed through sysctls.
+ Add more prose to the IPE base config option
help text.
+ Use GFP_KERNEL for audit_log_start.
+ Remove unnecessary caching system.
+ Remove comments from headers
+ Use rcu_access_pointer for rcu-pointer null check
+ Remove usage of reqprot; use prot only.
+ Move policy load and activation audit event to 03/12
v4:
+ Remove sysctls in favor of securityfs nodes
+ Re-add kernel module parameters, as these are now
exposed through securityfs.
+ Refactor property audit loop to a separate function.
v5:
+ fix minor grammatical errors
+ do not group rule by curly-brace in audit record,
reconstruct the exact rule.
v6:
+ No changes
v7:
+ Further split lsm creation into a separate commit from the
evaluation loop and audit system, for easier review.
+ Introduce the concept of an ipe_context, a scoped way to
introduce execution policies, used initially for allowing for
kunit tests in isolation.
v8:
+ Follow lsmname_hook_name convention for lsm hooks.
+ Move LSM blob accessors to ipe.c and mark LSM blobs as static.
v9:
+ Remove ipe_context for simplification
v10:
+ Add github url
v11:
+ Correct github url
+ Move ipe before bpf
---
MAINTAINERS | 7 +++++++
security/Kconfig | 11 ++++++-----
security/Makefile | 1 +
security/ipe/Kconfig | 17 +++++++++++++++++
security/ipe/Makefile | 9 +++++++++
security/ipe/ipe.c | 35 +++++++++++++++++++++++++++++++++++
security/ipe/ipe.h | 16 ++++++++++++++++
7 files changed, 91 insertions(+), 5 deletions(-)
create mode 100644 security/ipe/Kconfig
create mode 100644 security/ipe/Makefile
create mode 100644 security/ipe/ipe.c
create mode 100644 security/ipe/ipe.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 35977b269d5e..b898f2f8f9c4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10389,6 +10389,13 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git
F: security/integrity/
F: security/integrity/ima/
+INTEGRITY POLICY ENFORCEMENT (IPE)
+M: Fan Wu <[email protected]>
+L: [email protected]
+S: Supported
+T: git https://github.com/microsoft/ipe.git
+F: security/ipe/
+
INTEL 810/815 FRAMEBUFFER DRIVER
M: Antonino Daplas <[email protected]>
L: [email protected]
diff --git a/security/Kconfig b/security/Kconfig
index 52c9af08ad35..cc7adfbb6b96 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -194,6 +194,7 @@ source "security/yama/Kconfig"
source "security/safesetid/Kconfig"
source "security/lockdown/Kconfig"
source "security/landlock/Kconfig"
+source "security/ipe/Kconfig"
source "security/integrity/Kconfig"
@@ -233,11 +234,11 @@ endchoice
config LSM
string "Ordered list of enabled LSMs"
- default "landlock,lockdown,yama,loadpin,safesetid,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
- default "landlock,lockdown,yama,loadpin,safesetid,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
- default "landlock,lockdown,yama,loadpin,safesetid,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
- default "landlock,lockdown,yama,loadpin,safesetid,bpf" if DEFAULT_SECURITY_DAC
- default "landlock,lockdown,yama,loadpin,safesetid,selinux,smack,tomoyo,apparmor,bpf"
+ default "landlock,lockdown,yama,loadpin,safesetid,smack,selinux,tomoyo,apparmor,ipe,bpf" if DEFAULT_SECURITY_SMACK
+ default "landlock,lockdown,yama,loadpin,safesetid,apparmor,selinux,smack,tomoyo,ipe,bpf" if DEFAULT_SECURITY_APPARMOR
+ default "landlock,lockdown,yama,loadpin,safesetid,tomoyo,ipe,bpf" if DEFAULT_SECURITY_TOMOYO
+ default "landlock,lockdown,yama,loadpin,safesetid,ipe,bpf" if DEFAULT_SECURITY_DAC
+ default "landlock,lockdown,yama,loadpin,safesetid,selinux,smack,tomoyo,apparmor,ipe,bpf"
help
A comma-separated list of LSMs, in initialization order.
Any LSMs left off this list, except for those with order
diff --git a/security/Makefile b/security/Makefile
index 18121f8f85cd..527b1864d96c 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/
obj-$(CONFIG_CGROUPS) += device_cgroup.o
obj-$(CONFIG_BPF_LSM) += bpf/
obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/
+obj-$(CONFIG_SECURITY_IPE) += ipe/
# Object integrity file lists
obj-$(CONFIG_INTEGRITY) += integrity/
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
new file mode 100644
index 000000000000..e4875fb04883
--- /dev/null
+++ b/security/ipe/Kconfig
@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Integrity Policy Enforcement (IPE) configuration
+#
+
+menuconfig SECURITY_IPE
+ bool "Integrity Policy Enforcement (IPE)"
+ depends on SECURITY && SECURITYFS
+ select PKCS7_MESSAGE_PARSER
+ select SYSTEM_DATA_VERIFICATION
+ help
+ This option enables the Integrity Policy Enforcement LSM
+ allowing users to define a policy to enforce a trust-based access
+ control. A key feature of IPE is a customizable policy to allow
+ admins to reconfigure trust requirements on the fly.
+
+ If unsure, answer N.
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
new file mode 100644
index 000000000000..f7a80d0f18f8
--- /dev/null
+++ b/security/ipe/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) Microsoft Corporation. All rights reserved.
+#
+# Makefile for building the IPE module as part of the kernel tree.
+#
+
+obj-$(CONFIG_SECURITY_IPE) += \
+ ipe.o \
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
new file mode 100644
index 000000000000..ba5526f9d527
--- /dev/null
+++ b/security/ipe/ipe.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "ipe.h"
+
+static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
+};
+
+static struct security_hook_list ipe_hooks[] __ro_after_init = {
+};
+
+/**
+ * ipe_init - Entry point of IPE.
+ *
+ * This is called at LSM init, which happens occurs early during kernel
+ * start up. During this phase, IPE registers its hooks and loads the
+ * builtin boot policy.
+ * Return:
+ * * 0 - OK
+ * * -ENOMEM - Out of memory
+ */
+static int __init ipe_init(void)
+{
+ security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), "ipe");
+
+ return 0;
+}
+
+DEFINE_LSM(ipe) = {
+ .name = "ipe",
+ .init = ipe_init,
+ .blobs = &ipe_blobs,
+};
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
new file mode 100644
index 000000000000..a1c68d0fc2e0
--- /dev/null
+++ b/security/ipe/ipe.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_H
+#define _IPE_H
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+#define pr_fmt(fmt) "IPE: " fmt
+
+#include <linux/lsm_hooks.h>
+
+#endif /* _IPE_H */
--
2.25.1
When deleting a directory in the security file system, the existing
securityfs_remove requires the directory to be empty, otherwise
it will do nothing. This leads to a potential risk that the security
file system might be in an unclean state when the intentded deletion
did not happen.
This commit introduces a new function securityfs_recursive_remove
to recursively delete a directory without leaving an unclean state.
Co-developed-by: Christian Brauner (Microsoft) <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v1-v8:
+ Not present
v9:
+ Introduced
v10:
+ No changes
v11:
+ Fix code style issues
---
include/linux/security.h | 1 +
security/inode.c | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+)
diff --git a/include/linux/security.h b/include/linux/security.h
index 5f16eecde00b..8fa3bab9fa10 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1985,6 +1985,7 @@ struct dentry *securityfs_create_symlink(const char *name,
const char *target,
const struct inode_operations *iops);
extern void securityfs_remove(struct dentry *dentry);
+extern void securityfs_recursive_remove(struct dentry *dentry);
#else /* CONFIG_SECURITYFS */
diff --git a/security/inode.c b/security/inode.c
index 3aa75fffa8c9..e0585c2946c5 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -313,6 +313,31 @@ void securityfs_remove(struct dentry *dentry)
}
EXPORT_SYMBOL_GPL(securityfs_remove);
+static void remove_one(struct dentry *victim)
+{
+ simple_release_fs(&mount, &mount_count);
+}
+
+/**
+ * securityfs_recursive_remove - recursively removes a file or directory
+ *
+ * @dentry: a pointer to a the dentry of the file or directory to be removed.
+ *
+ * This function recursively removes a file or directory in securityfs that was
+ * previously created with a call to another securityfs function (like
+ * securityfs_create_file() or variants thereof.)
+ */
+void securityfs_recursive_remove(struct dentry *dentry)
+{
+ if (IS_ERR_OR_NULL(dentry))
+ return;
+
+ simple_pin_fs(&fs_type, &mount, &mount_count);
+ simple_recursive_removal(dentry, remove_one);
+ simple_release_fs(&mount, &mount_count);
+}
+EXPORT_SYMBOL_GPL(securityfs_recursive_remove);
+
#ifdef CONFIG_SECURITY
static struct dentry *lsm_dentry;
static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
--
2.25.1
Enable IPE policy authors to indicate trust for a singular fsverity
file, identified by the digest information, through "fsverity_digest"
and all files using fsverity's builtin signatures via
"fsverity_signature".
This enables file-level integrity claims to be expressed in IPE,
allowing individual files to be authorized, giving some flexibility
for policy authors. Such file-level claims are important to be expressed
for enforcing the integrity of packages, as well as address some of the
scalability issues in a sole dm-verity based solution (# of loop back
devices, etc).
This solution cannot be done in userspace as the minimum threat that
IPE should mitigate is an attacker downloads malicious payload with
all required dependencies. These dependencies can lack the userspace
check, bypassing the protection entirely. A similar attack succeeds if
the userspace component is replaced with a version that does not
perform the check. As a result, this can only be done in the common
entry point - the kernel.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v1-v6:
+ Not present
v7:
Introduced
v8:
* Undo squash of 08/12, 10/12 - separating drivers/md/ from security/
* Use common-audit function for fsverity_signature.
+ Change fsverity implementation to use fsverity_get_digest
+ prevent unnecessary copy of fs-verity signature data, instead
just check for presence of signature data.
+ Remove free_inode_security hook, as the digest is now acquired
at runtime instead of via LSM blob.
v9:
+ Adapt to the new parser
v10:
+ Update the fsverity get digest call
v11:
+ No changes
---
security/ipe/Kconfig | 13 +++++
security/ipe/audit.c | 23 ++++++++
security/ipe/eval.c | 110 +++++++++++++++++++++++++++++++++++
security/ipe/eval.h | 10 ++++
security/ipe/hooks.c | 30 ++++++++++
security/ipe/hooks.h | 7 +++
security/ipe/ipe.c | 13 +++++
security/ipe/ipe.h | 3 +
security/ipe/policy.h | 3 +
security/ipe/policy_parser.c | 8 +++
10 files changed, 220 insertions(+)
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 7afb1ce0cb99..9dd5c4769d79 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -30,6 +30,19 @@ config IPE_PROP_DM_VERITY
that was mounted with a signed root-hash or the volume's
root hash matches the supplied value in the policy.
+ If unsure, answer Y.
+
+config IPE_PROP_FS_VERITY
+ bool "Enable property for fs-verity files"
+ depends on FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
+ help
+ This option enables the usage of properties "fsverity_signature"
+ and "fsverity_digest". These properties evaluates to TRUE when
+ a file is fsverity enabled and with a signed digest or its
+ diegst matches the supplied value in the policy.
+
+ if unsure, answer Y.
+
endmenu
endif
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index b5c58655ac74..e3a8552a76a4 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -46,6 +46,11 @@ static const char *const audit_prop_names[__IPE_PROP_MAX] = {
"dmverity_signature=FALSE",
"dmverity_signature=TRUE",
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ "fsverity_digest=",
+ "fsverity_signature=FALSE",
+ "fsverity_signature=TRUE"
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
};
#ifdef CONFIG_IPE_PROP_DM_VERITY
@@ -64,6 +69,22 @@ static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+/**
+ * audit_fsv_digest - audit a digest of a fsverity file.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @d: Supplies a pointer to the digest structure.
+ */
+static void audit_fsv_digest(struct audit_buffer *ab, const void *d)
+{
+ ipe_digest_audit(ab, d);
+}
+#else
+static void audit_fsv_digest(struct audit_buffer *ab, const void *d)
+{
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
/**
* audit_rule - audit an IPE policy rule approximation.
* @ab: Supplies a pointer to the audit_buffer to append to.
@@ -79,6 +100,8 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
if (ptr->type == IPE_PROP_DMV_ROOTHASH)
audit_dmv_roothash(ab, ptr->value);
+ if (ptr->type == IPE_PROP_FSV_DIGEST)
+ audit_fsv_digest(ab, ptr->value);
audit_log_format(ab, " ");
}
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 82ad48d7aa3d..f0194b0ca2ff 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -11,6 +11,7 @@
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
+#include <linux/fsverity.h>
#include "ipe.h"
#include "eval.h"
@@ -78,6 +79,23 @@ static void build_ipe_bdev_ctx(struct ipe_eval_ctx *ctx, const struct inode *con
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+/**
+ * build_ipe_inode_ctx - Build inode fields of an evaluation context.
+ * @ctx: Supplies a pointer to the context to be populdated.
+ * @ino: Supplies the inode struct of the file triggered IPE event.
+ */
+static void build_ipe_inode_ctx(struct ipe_eval_ctx *ctx, const struct inode *const ino)
+{
+ ctx->ino = ino;
+ ctx->ipe_inode = ipe_inode(ctx->ino);
+}
+#else
+static void build_ipe_inode_ctx(struct ipe_eval_ctx *ctx, const struct inode *const ino)
+{
+}
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
/**
* build_eval_ctx - Build an evaluation context.
* @ctx: Supplies a pointer to the context to be populdated.
@@ -100,6 +118,7 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
ctx->from_init_sb = from_pinned(FILE_SUPERBLOCK(file));
ino = d_real_inode(file->f_path.dentry);
build_ipe_bdev_ctx(ctx, ino);
+ build_ipe_inode_ctx(ctx, ino);
}
}
@@ -172,6 +191,91 @@ static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+/**
+ * evaluate_fsv_digest - Analyze @ctx against a fsv digest property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_fsv_digest(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ enum hash_algo alg;
+ u8 digest[FS_VERITY_MAX_DIGEST_SIZE];
+
+ if (!ctx->ino)
+ return false;
+ if (!fsverity_get_digest((struct inode *)ctx->ino,
+ digest,
+ NULL,
+ &alg))
+ return false;
+
+ return ipe_digest_eval(p->value,
+ digest,
+ hash_digest_size[alg],
+ hash_algo_name[alg]);
+}
+
+/**
+ * evaluate_fsv_sig_false - Analyze @ctx against a fsv sig false property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_fsv_sig_false(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return !ctx->ino ||
+ !IS_VERITY(ctx->ino) ||
+ !ctx->ipe_inode ||
+ !ctx->ipe_inode->fs_verity_signed;
+}
+
+/**
+ * evaluate_fsv_sig_true - Analyze @ctx against a fsv sig true property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ * @p: Supplies a pointer to the property being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_fsv_sig_true(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return ctx->ino &&
+ IS_VERITY(ctx->ino) &&
+ ctx->ipe_inode &&
+ ctx->ipe_inode->fs_verity_signed;
+}
+#else
+static bool evaluate_fsv_digest(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+
+static bool evaluate_fsv_sig_false(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+
+static bool evaluate_fsv_sig_true(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
/**
* evaluate_property - Analyze @ctx against a property.
* @ctx: Supplies a pointer to the context to be evaluated.
@@ -195,6 +299,12 @@ static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
return evaluate_dmv_sig_false(ctx, p);
case IPE_PROP_DMV_SIG_TRUE:
return evaluate_dmv_sig_true(ctx, p);
+ case IPE_PROP_FSV_DIGEST:
+ return evaluate_fsv_digest(ctx, p);
+ case IPE_PROP_FSV_SIG_FALSE:
+ return evaluate_fsv_sig_false(ctx, p);
+ case IPE_PROP_FSV_SIG_TRUE:
+ return evaluate_fsv_sig_true(ctx, p);
default:
return false;
}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index e575e94804a4..7f5b64c30ffe 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -27,6 +27,12 @@ struct ipe_bdev {
};
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+struct ipe_inode {
+ bool fs_verity_signed;
+};
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
struct ipe_eval_ctx {
enum ipe_op_type op;
@@ -35,6 +41,10 @@ struct ipe_eval_ctx {
#ifdef CONFIG_IPE_PROP_DM_VERITY
const struct ipe_bdev *ipe_bdev;
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ const struct inode *ino;
+ const struct ipe_inode *ipe_inode;
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
};
enum ipe_match {
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index 8b8031e66f36..1897d76354d7 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -244,3 +244,33 @@ int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
return -EOPNOTSUPP;
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+/**
+ * ipe_inode_setsecurity - Sets fields of a inode security blob from @key.
+ * @inode: The inode to source the security blob from.
+ * @name: The name representing the information to be stored.
+ * @value: The value to be stored.
+ * @size: The size of @value.
+ * @flags: unused
+ *
+ * Saves fsverity signature & digest into inode security blob
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Error
+ */
+int ipe_inode_setsecurity(struct inode *inode, const char *name,
+ const void *value, size_t size,
+ int flags)
+{
+ struct ipe_inode *inode_sec = ipe_inode(inode);
+
+ if (!strcmp(name, FS_VERITY_INODE_SEC_NAME)) {
+ inode_sec->fs_verity_signed = size > 0 && value;
+ return 0;
+ }
+
+ return -EOPNOTSUPP;
+}
+#endif /* CONFIG_CONFIG_IPE_PROP_FS_VERITY */
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index d8ccb3728813..687d6b9fa869 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -9,6 +9,7 @@
#include <linux/binfmts.h>
#include <linux/security.h>
#include <linux/blk_types.h>
+#include <linux/fsverity.h>
int ipe_bprm_check_security(struct linux_binprm *bprm);
@@ -32,4 +33,10 @@ int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
const void *value, size_t len);
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+int ipe_inode_setsecurity(struct inode *inode, const char *name,
+ const void *value, size_t size,
+ int flags);
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
#endif /* _IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index c7e8af554d35..e789f1db6f66 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -13,6 +13,9 @@ static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
#ifdef CONFIG_IPE_PROP_DM_VERITY
.lbs_bdev = sizeof(struct ipe_bdev),
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ .lbs_inode = sizeof(struct ipe_inode),
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
};
#ifdef CONFIG_IPE_PROP_DM_VERITY
@@ -22,6 +25,13 @@ struct ipe_bdev *ipe_bdev(struct block_device *b)
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+struct ipe_inode *ipe_inode(const struct inode *inode)
+{
+ return inode->i_security + ipe_blobs.lbs_inode;
+}
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(bprm_check_security, ipe_bprm_check_security),
LSM_HOOK_INIT(mmap_file, ipe_mmap_file),
@@ -33,6 +43,9 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity),
#endif
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ LSM_HOOK_INIT(inode_setsecurity, ipe_inode_setsecurity),
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
};
/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index 4e8d1a440c4b..d32f99350503 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -18,5 +18,8 @@ extern bool ipe_enabled;
#ifdef CONFIG_IPE_PROP_DM_VERITY
struct ipe_bdev *ipe_bdev(struct block_device *b);
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+struct ipe_inode *ipe_inode(const struct inode *inode);
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
#endif /* _IPE_H */
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index 13e5c40e9204..51a7c21bb8ad 100644
--- a/security/ipe/policy.h
+++ b/security/ipe/policy.h
@@ -36,6 +36,9 @@ enum ipe_prop_type {
IPE_PROP_DMV_ROOTHASH,
IPE_PROP_DMV_SIG_FALSE,
IPE_PROP_DMV_SIG_TRUE,
+ IPE_PROP_FSV_DIGEST,
+ IPE_PROP_FSV_SIG_FALSE,
+ IPE_PROP_FSV_SIG_TRUE,
__IPE_PROP_MAX
};
diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
index 3acb1d681f65..aacc0c4cf9df 100644
--- a/security/ipe/policy_parser.c
+++ b/security/ipe/policy_parser.c
@@ -275,6 +275,11 @@ static const match_table_t property_tokens = {
{IPE_PROP_DMV_SIG_FALSE, "dmverity_signature=FALSE"},
{IPE_PROP_DMV_SIG_TRUE, "dmverity_signature=TRUE"},
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ {IPE_PROP_FSV_DIGEST, "fsverity_digest=%s"},
+ {IPE_PROP_FSV_SIG_FALSE, "fsverity_signature=FALSE"},
+ {IPE_PROP_FSV_SIG_TRUE, "fsverity_signature=TRUE"},
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
{IPE_PROP_INVALID, NULL}
};
@@ -304,6 +309,7 @@ static int parse_property(char *t, struct ipe_rule *r)
switch (token) {
case IPE_PROP_DMV_ROOTHASH:
+ case IPE_PROP_FSV_DIGEST:
dup = match_strdup(&args[0]);
if (!dup) {
rc = -ENOMEM;
@@ -317,6 +323,8 @@ static int parse_property(char *t, struct ipe_rule *r)
case IPE_PROP_BOOT_VERIFIED_TRUE:
case IPE_PROP_DMV_SIG_FALSE:
case IPE_PROP_DMV_SIG_TRUE:
+ case IPE_PROP_FSV_SIG_FALSE:
+ case IPE_PROP_FSV_SIG_TRUE:
p->type = token;
break;
default:
--
2.25.1
From: Deven Bowers <[email protected]>
Users of IPE require a way to identify when and why an operation fails,
allowing them to both respond to violations of policy and be notified
of potentially malicious actions on their systems with respect to IPE
itself.
This patch introduces 3 new audit events.
AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation
of a resource.
AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy
has been changed to another loaded policy.
AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded
into the kernel.
This patch also adds support for success auditing, allowing users to
identify why an allow decision was made for a resource. However, it is
recommended to use this option with caution, as it is quite noisy.
Here are some examples of the new audit record types:
AUDIT_IPE_ACCESS(1420):
audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda"
ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
ino=2 rule="DEFAULT action=DENY"
audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs"
ino=131 rule="DEFAULT action=DENY"
The above three records were generated when the active IPE policy only
allows binaries from the initial booted drive(sda) to run. The three
identical `hello` binary were placed at different locations, only the
first hello from sda was allowed.
Field path followed by the file's path name.
Field dev followed by the device name as found in /dev where the file is
from.
Note that for device mappers it will use the name `dm-X` instead of
the name in /dev/mapper.
For a file in a temp file system, which is not from a device, it will use
`tmpfs` for the field.
The implementation of this part is following another existing use case
LSM_AUDIT_DATA_INODE in security/lsm_audit.c
Field ino followed by the file's inode number.
Field rule followed by the IPE rule made the access decision. The whole
rule must be audited because the decision is based on the combination of
all property conditions in the rule.
Along with the syscall audit event, user can know why a blocked
happened. For example:
audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
ino=2 rule="DEFAULT action=DENY"
audit[1956]: SYSCALL arch=c000003e syscall=59
success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0
a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 auid=4294967295 uid=0
gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0
ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null)
The above two records showed bash used execve to run "hello" and got
blocked by IPE. Note that the IPE records are always prior to a SYSCALL
record.
AUDIT_IPE_CONFIG_CHANGE(1421):
audit: AUDIT1421
old_active_pol_name="Allow_All" old_active_pol_version=0.0.0
old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649
new_active_pol_name="boot_verified" new_active_pol_version=0.0.0
new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F
auid=4294967295 ses=4294967295 lsm=ipe res=1
The above record showed the current IPE active policy switch from
`Allow_All` to `boot_verified` along with the version and the hash
digest of the two policies. Note IPE can only have one policy active
at a time, all access decision evaluation is based on the current active
policy.
The normal procedure to deploy a policy is loading the policy to deploy
into the kernel first, then switch the active policy to it.
AUDIT_IPE_POLICY_LOAD(1422):
audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0
policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD
auid=4294967295 ses=4294967295 lsm=ipe res=1
The above record showed a new policy has been loaded into the kernel
with the policy name, policy version and policy hash.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks,
and evaluation loop from policy parser and userspace
interface to pass mailing list character limit
v3:
+ Move ipe_load_properties to patch 04.
+ Remove useless 0-initializations
+ Prefix extern variables with ipe_
+ Remove kernel module parameters, as these are
exposed through sysctls.
+ Add more prose to the IPE base config option
help text.
+ Use GFP_KERNEL for audit_log_start.
+ Remove unnecessary caching system.
+ Remove comments from headers
+ Use rcu_access_pointer for rcu-pointer null check
+ Remove usage of reqprot; use prot only.
+ Move policy load and activation audit event to 03/12
v4:
+ Remove sysctls in favor of securityfs nodes
+ Re-add kernel module parameters, as these are now
exposed through securityfs.
+ Refactor property audit loop to a separate function.
v5:
+ fix minor grammatical errors
+ do not group rule by curly-brace in audit record,
reconstruct the exact rule.
v6:
+ No changes
v7:
+ Further split lsm creation, the audit system, the evaluation loop,
and access control hooks into separate patches.
+ Further split audit system patch into two separate patches; one
for include/uapi, and the usage of the new defines.
+ Split out the permissive functionality into another separate patch,
for easier review.
+ Correct misuse of audit_log_n_untrusted string to audit_log_format
+ Use get_task_comm instead of comm directly.
+ Quote certain audit values
+ Remove unnecessary help text on choice options - these were
previously
idented at the wrong level
+ Correct a stale string constant (ctx_ns_enforce to ctx_enforce)
v8:
+ Change dependency for CONFIG_AUDIT to CONFIG_AUDITSYSCALL
+ Drop ctx_* prefix
+ Reuse, where appropriate, the audit fields from the field
dictionary. This transforms:
ctx_pathname -> path
ctx_ino -> ino
ctx_dev -> dev
+ Add audit records and event examples to commit description.
+ Remove new_audit_ctx, replace with audit_log_start. All data that
would provided by new_audit_ctx is already present in the syscall
audit record, that is always emitted on these actions. The audit
records should be correlated as such.
+ Change audit types:
+ AUDIT_TRUST_RESULT -> AUDIT_IPE_ACCESS
+ This prevents overloading of the AVC type.
+ AUDIT_TRUST_POLICY_ACTIVATE -> AUDIT_MAC_CONFIG_CHANGE
+ AUDIT_TRUST_POLICY_LOAD -> AUDIT_MAC_POLICY_LOAD
+ There were no significant difference in meaning between
these types.
+ Remove enforcing parameter passed from the context structure
for AUDIT_IPE_ACCESS.
+ This field can be inferred from the SYSCALL audit event,
based on the success field.
+ Remove all fields already captured in the syscall record. "hook",
an IPE specific field, can be determined via the syscall field in
the syscall record itself, so it has been removed.
+ ino, path, and dev in IPE's record refer to the subject of the
syscall, while the syscall record refers to the calling process.
+ remove IPE prefix from policy load/policy activation events
+ fix a bug wherein a policy change audit record was not fired when
updating a policy
v9:
+ Merge the AUDIT_IPE_ACCESS definition with the audit support commit
+ Change the audit format of policy load and switch
+ Remove the ipe audit kernel switch
v10:
+ Create AUDIT_IPE_CONFIG_CHANGE and AUDIT_IPE_POLICY_LOAD
+ Change field names per upstream feedback
v11:
+ Fix style issues
---
include/uapi/linux/audit.h | 3 +
security/ipe/Kconfig | 2 +-
security/ipe/Makefile | 1 +
security/ipe/audit.c | 195 +++++++++++++++++++++++++++++++++++++
security/ipe/audit.h | 18 ++++
security/ipe/eval.c | 32 ++++--
security/ipe/eval.h | 8 ++
security/ipe/fs.c | 70 +++++++++++++
security/ipe/policy.c | 5 +
9 files changed, 327 insertions(+), 7 deletions(-)
create mode 100644 security/ipe/audit.c
create mode 100644 security/ipe/audit.h
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index d676ed2b246e..75e21a135483 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -143,6 +143,9 @@
#define AUDIT_MAC_UNLBL_STCDEL 1417 /* NetLabel: del a static label */
#define AUDIT_MAC_CALIPSO_ADD 1418 /* NetLabel: add CALIPSO DOI entry */
#define AUDIT_MAC_CALIPSO_DEL 1419 /* NetLabel: del CALIPSO DOI entry */
+#define AUDIT_IPE_ACCESS 1420 /* IPE denial or grant */
+#define AUDIT_IPE_CONFIG_CHANGE 1421 /* IPE config change */
+#define AUDIT_IPE_POLICY_LOAD 1422 /* IPE policy load */
#define AUDIT_FIRST_KERN_ANOM_MSG 1700
#define AUDIT_LAST_KERN_ANOM_MSG 1799
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index e4875fb04883..ac4d558e69d5 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -5,7 +5,7 @@
menuconfig SECURITY_IPE
bool "Integrity Policy Enforcement (IPE)"
- depends on SECURITY && SECURITYFS
+ depends on SECURITY && SECURITYFS && AUDIT && AUDITSYSCALL
select PKCS7_MESSAGE_PARSER
select SYSTEM_DATA_VERIFICATION
help
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index cfbed03a8885..2279eaa3cea3 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_SECURITY_IPE) += \
policy.o \
policy_fs.o \
policy_parser.o \
+ audit.o \
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
new file mode 100644
index 000000000000..e123701d5e3b
--- /dev/null
+++ b/security/ipe/audit.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/slab.h>
+#include <linux/audit.h>
+#include <linux/types.h>
+#include <crypto/hash.h>
+
+#include "ipe.h"
+#include "eval.h"
+#include "hooks.h"
+#include "policy.h"
+#include "audit.h"
+
+#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
+
+#define IPE_AUDIT_HASH_ALG "sha256"
+
+#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\
+ "policy_digest=" IPE_AUDIT_HASH_ALG ":"
+#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\
+ "old_active_pol_version=%hu.%hu.%hu "\
+ "old_policy_digest=" IPE_AUDIT_HASH_ALG ":"
+#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\
+ "new_active_pol_version=%hu.%hu.%hu "\
+ "new_policy_digest=" IPE_AUDIT_HASH_ALG ":"
+
+static const char *const audit_op_names[__IPE_OP_MAX] = {
+ "EXECUTE",
+ "FIRMWARE",
+ "KMODULE",
+ "KEXEC_IMAGE",
+ "KEXEC_INITRAMFS",
+ "IMA_POLICY",
+ "IMA_X509_CERT",
+};
+
+static const char *const audit_prop_names[__IPE_PROP_MAX] = {
+ "boot_verified=FALSE",
+ "boot_verified=TRUE",
+};
+
+/**
+ * audit_rule - audit an IPE policy rule approximation.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
+ */
+static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
+{
+ const struct ipe_prop *ptr;
+
+ audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
+
+ list_for_each_entry(ptr, &r->props, next)
+ audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
+
+ audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
+}
+
+/**
+ * ipe_audit_match - audit a match for IPE policy.
+ * @ctx: Supplies a pointer to the evaluation context that was used in the
+ * evaluation.
+ * @match_type: Supplies the scope of the match: rule, operation default,
+ * global default.
+ * @act: Supplies the IPE's evaluation decision, deny or allow.
+ * @r: Supplies a pointer to the rule that was matched, if possible.
+ * @enforce: Supplies the enforcement/permissive state at the point
+ * the enforcement decision was made.
+ */
+void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
+ enum ipe_match match_type,
+ enum ipe_action_type act, const struct ipe_rule *const r)
+{
+ struct inode *inode;
+ struct audit_buffer *ab;
+ const char *op = audit_op_names[ctx->op];
+
+ if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit))
+ return;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
+ if (!ab)
+ return;
+
+ if (ctx->file) {
+ audit_log_d_path(ab, "path=", &ctx->file->f_path);
+ inode = file_inode(ctx->file);
+ if (inode) {
+ audit_log_format(ab, " dev=");
+ audit_log_untrustedstring(ab, inode->i_sb->s_id);
+ audit_log_format(ab, " ino=%lu ", inode->i_ino);
+ }
+ }
+
+ if (match_type == IPE_MATCH_RULE)
+ audit_rule(ab, r);
+ else if (match_type == IPE_MATCH_TABLE)
+ audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op,
+ ACTSTR(act));
+ else
+ audit_log_format(ab, "rule=\"DEFAULT action=%s\"",
+ ACTSTR(act));
+
+ audit_log_end(ab);
+}
+
+/**
+ * audit_policy - Audit a policy's name, version and thumbprint to @ab.
+ * @ab: Supplies a pointer to the audit buffer to append to.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+static void audit_policy(struct audit_buffer *ab,
+ const char *audit_format,
+ const struct ipe_policy *const p)
+{
+ u8 *digest = NULL;
+ struct crypto_shash *tfm;
+ SHASH_DESC_ON_STACK(desc, tfm);
+
+ tfm = crypto_alloc_shash(IPE_AUDIT_HASH_ALG, 0, 0);
+ if (IS_ERR(tfm))
+ return;
+
+ desc->tfm = tfm;
+
+ digest = kzalloc(crypto_shash_digestsize(tfm), GFP_KERNEL);
+ if (!digest)
+ goto out;
+
+ if (crypto_shash_init(desc))
+ goto out;
+
+ if (crypto_shash_update(desc, p->pkcs7, p->pkcs7len))
+ goto out;
+
+ if (crypto_shash_final(desc, digest))
+ goto out;
+
+ audit_log_format(ab, audit_format, p->parsed->name,
+ p->parsed->version.major, p->parsed->version.minor,
+ p->parsed->version.rev);
+ audit_log_n_hex(ab, digest, crypto_shash_digestsize(tfm));
+
+out:
+ kfree(digest);
+ crypto_free_shash(tfm);
+}
+
+/**
+ * ipe_audit_policy_activation - Audit a policy being made the active policy.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+void ipe_audit_policy_activation(const struct ipe_policy *const op,
+ const struct ipe_policy *const np)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL,
+ AUDIT_IPE_CONFIG_CHANGE);
+ if (!ab)
+ return;
+
+ audit_policy(ab, AUDIT_OLD_ACTIVE_POLICY_FMT, op);
+ audit_log_format(ab, " ");
+ audit_policy(ab, AUDIT_NEW_ACTIVE_POLICY_FMT, np);
+ audit_log_format(ab, " auid=%u ses=%u lsm=ipe res=1",
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ audit_get_sessionid(current));
+
+ audit_log_end(ab);
+}
+
+/**
+ * ipe_audit_policy_load - Audit a policy being loaded into the kernel.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+void ipe_audit_policy_load(const struct ipe_policy *const p)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL,
+ AUDIT_IPE_POLICY_LOAD);
+ if (!ab)
+ return;
+
+ audit_policy(ab, AUDIT_POLICY_LOAD_FMT, p);
+ audit_log_format(ab, " auid=%u ses=%u lsm=ipe res=1",
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ audit_get_sessionid(current));
+
+ audit_log_end(ab);
+}
diff --git a/security/ipe/audit.h b/security/ipe/audit.h
new file mode 100644
index 000000000000..0ff5a06808de
--- /dev/null
+++ b/security/ipe/audit.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_AUDIT_H
+#define _IPE_AUDIT_H
+
+#include "policy.h"
+
+void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
+ enum ipe_match match_type,
+ enum ipe_action_type act, const struct ipe_rule *const r);
+void ipe_audit_policy_load(const struct ipe_policy *const p);
+void ipe_audit_policy_activation(const struct ipe_policy *const op,
+ const struct ipe_policy *const np);
+
+#endif /* _IPE_AUDIT_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index bdac4abc0ddb..499b6b3338f2 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -10,12 +10,15 @@
#include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
+#include <linux/moduleparam.h>
#include "ipe.h"
#include "eval.h"
#include "policy.h"
+#include "audit.h"
struct ipe_policy __rcu *ipe_active_policy;
+bool success_audit;
static const struct super_block *pinned_sb;
static DEFINE_SPINLOCK(pin_lock);
@@ -112,6 +115,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
{
bool match = false;
enum ipe_action_type action;
+ enum ipe_match match_type;
struct ipe_policy *pol = NULL;
const struct ipe_rule *rule = NULL;
const struct ipe_op_table *rules = NULL;
@@ -127,9 +131,9 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
if (ctx->op == IPE_OP_INVALID) {
rcu_read_unlock();
- if (pol->parsed->global_default_action == IPE_ACTION_DENY)
- return -EACCES;
- return 0;
+ action = pol->parsed->global_default_action;
+ match_type = IPE_MATCH_GLOBAL;
+ goto eval;
}
rules = &pol->parsed->rules[ctx->op];
@@ -147,14 +151,21 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
break;
}
- if (match)
+ if (match) {
action = rule->action;
- else if (rules->default_action != IPE_ACTION_INVALID)
+ match_type = IPE_MATCH_RULE;
+ } else if (rules->default_action != IPE_ACTION_INVALID) {
action = rules->default_action;
- else
+ match_type = IPE_MATCH_TABLE;
+ } else {
action = pol->parsed->global_default_action;
+ match_type = IPE_MATCH_GLOBAL;
+ }
rcu_read_unlock();
+eval:
+ ipe_audit_match(ctx, match_type, action, rule);
+
if (action == IPE_ACTION_DENY)
return -EACCES;
@@ -178,3 +189,12 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
spin_unlock(&pin_lock);
}
+
+/* Set the right module name */
+#ifdef KBUILD_MODNAME
+#undef KBUILD_MODNAME
+#define KBUILD_MODNAME "ipe"
+#endif
+
+module_param(success_audit, bool, 0400);
+MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 9769da42c65f..5473f712566c 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -14,6 +14,7 @@
#define IPE_EVAL_CTX_INIT ((struct ipe_eval_ctx){ 0 })
extern struct ipe_policy __rcu *ipe_active_policy;
+extern bool success_audit;
struct ipe_eval_ctx {
enum ipe_op_type op;
@@ -22,6 +23,13 @@ struct ipe_eval_ctx {
bool from_init_sb;
};
+enum ipe_match {
+ IPE_MATCH_RULE = 0,
+ IPE_MATCH_TABLE,
+ IPE_MATCH_GLOBAL,
+ __IPE_MATCH_MAX
+};
+
void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb);
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index 522162af741a..dda7a5afc60c 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -8,11 +8,64 @@
#include "ipe.h"
#include "fs.h"
+#include "eval.h"
#include "policy.h"
+#include "audit.h"
static struct dentry *np __ro_after_init;
static struct dentry *root __ro_after_init;
struct dentry *policy_root __ro_after_init;
+static struct dentry *audit_node __ro_after_init;
+
+/**
+ * setaudit - Write handler for the securityfs node, "ipe/success_audit"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t setaudit(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ bool value;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ rc = kstrtobool_from_user(data, len, &value);
+ if (rc)
+ return rc;
+
+ WRITE_ONCE(success_audit, value);
+
+ return len;
+}
+
+/**
+ * getaudit - Read handler for the securityfs node, "ipe/success_audit"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the read syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getaudit(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ const char *result;
+
+ result = ((READ_ONCE(success_audit)) ? "1" : "0");
+
+ return simple_read_from_buffer(data, len, offset, result, 1);
+}
/**
* new_policy - Write handler for the securityfs node, "ipe/new_policy".
@@ -46,6 +99,10 @@ static ssize_t new_policy(struct file *f, const char __user *data,
}
rc = ipe_new_policyfs_node(p);
+ if (rc)
+ goto out;
+
+ ipe_audit_policy_load(p);
out:
if (rc < 0 && !IS_ERR(p))
@@ -58,6 +115,11 @@ static const struct file_operations np_fops = {
.write = new_policy,
};
+static const struct file_operations audit_fops = {
+ .write = setaudit,
+ .read = getaudit,
+};
+
/**
* ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
*
@@ -78,6 +140,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}
+ audit_node = securityfs_create_file("success_audit", 0600, root,
+ NULL, &audit_fops);
+ if (IS_ERR(audit_node)) {
+ rc = PTR_ERR(audit_node);
+ goto err;
+ }
+
policy_root = securityfs_create_dir("policies", root);
if (IS_ERR(policy_root)) {
rc = PTR_ERR(policy_root);
@@ -94,6 +163,7 @@ static int __init ipe_init_securityfs(void)
err:
securityfs_remove(np);
securityfs_remove(policy_root);
+ securityfs_remove(audit_node);
securityfs_remove(root);
return rc;
}
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index 33bbc43f0d6f..7a0729246bbd 100644
--- a/security/ipe/policy.c
+++ b/security/ipe/policy.c
@@ -11,6 +11,7 @@
#include "fs.h"
#include "policy.h"
#include "policy_parser.h"
+#include "audit.h"
/* lock for synchronizing writers across ipe policy */
DEFINE_MUTEX(ipe_policy_lock);
@@ -124,6 +125,8 @@ struct ipe_policy *ipe_update_policy(struct inode *root,
swap(new->policyfs, old->policyfs);
+ ipe_audit_policy_load(new);
+
return old;
err:
ipe_free_policy(new);
@@ -209,5 +212,7 @@ int ipe_set_active_pol(const struct ipe_policy *p)
rcu_assign_pointer(ipe_active_policy, p);
+ ipe_audit_policy_activation(ap, p);
+
return 0;
}
--
2.25.1
From: Deven Bowers <[email protected]>
Add various happy/unhappy unit tests for both IPE's parser.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v1-v6:
+ Not present
v7:
Introduced
v8:
+ Remove the kunit tests with respect to the fsverity digest, as these
require significant changes to work with the new method of acquiring
the digest at runtime.
v9:
+ Remove the kunit tests related to ipe_context
v10:
+ No changes
v11:
+ No changes
---
security/ipe/Kconfig | 17 +++
security/ipe/Makefile | 3 +
security/ipe/policy_tests.c | 294 ++++++++++++++++++++++++++++++++++++
3 files changed, 314 insertions(+)
create mode 100644 security/ipe/policy_tests.c
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index a6c5d48dd0a3..ac04a9974297 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -55,4 +55,21 @@ config IPE_PROP_FS_VERITY
endmenu
+config SECURITY_IPE_KUNIT_TEST
+ bool "Build KUnit tests for IPE" if !KUNIT_ALL_TESTS
+ depends on KUNIT=y
+ default KUNIT_ALL_TESTS
+ help
+ This builds the IPE KUnit tests.
+
+ KUnit tests run during boot and output the results to the debug log
+ in TAP format (https://testanything.org/). Only useful for kernel devs
+ running KUnit test harness and are not for inclusion into a
+ production build.
+
+ For more information on KUnit and unit tests in general please refer
+ to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+ If unsure, say N.
+
endif
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index ce23101b66ba..def674e09e84 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -26,3 +26,6 @@ obj-$(CONFIG_SECURITY_IPE) += \
audit.o \
clean-files := boot-policy.c \
+
+obj-$(CONFIG_SECURITY_IPE_KUNIT_TEST) += \
+ policy_tests.o \
diff --git a/security/ipe/policy_tests.c b/security/ipe/policy_tests.c
new file mode 100644
index 000000000000..d67c42c9ca59
--- /dev/null
+++ b/security/ipe/policy_tests.c
@@ -0,0 +1,294 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <kunit/test.h>
+#include "policy.h"
+struct policy_case {
+ const char *const policy;
+ int errno;
+ const char *const desc;
+};
+
+static const struct policy_case policy_cases[] = {
+ {
+ "policy_name=allowall policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW",
+ 0,
+ "basic",
+ },
+ {
+ "policy_name=trailing_comment policy_version=152.0.0 #This is comment\n"
+ "DEFAULT action=ALLOW",
+ 0,
+ "trailing comment",
+ },
+ {
+ "policy_name=allowallnewline policy_version=0.2.0\n"
+ "DEFAULT action=ALLOW\n"
+ "\n",
+ 0,
+ "trailing newline",
+ },
+ {
+ "policy_name=carriagereturnlinefeed policy_version=0.0.1\n"
+ "DEFAULT action=ALLOW\n"
+ "\r\n",
+ 0,
+ "clrf newline",
+ },
+ {
+ "policy_name=whitespace policy_version=0.0.0\n"
+ "DEFAULT\taction=ALLOW\n"
+ " \t DEFAULT \t op=EXECUTE action=DENY\n"
+ "op=EXECUTE boot_verified=TRUE action=ALLOW\n"
+ "# this is a\tcomment\t\t\t\t\n"
+ "DEFAULT \t op=KMODULE\t\t\t action=DENY\r\n"
+ "op=KMODULE boot_verified=TRUE action=ALLOW\n",
+ 0,
+ "various whitespaces and nested default",
+ },
+ {
+ "policy_name=boot_verified policy_version=-1236.0.0\n"
+ "DEFAULT\taction=ALLOW\n",
+ -EINVAL,
+ "negative version",
+ },
+ {
+ "policy_name=$@!*&^%%\\:;{}() policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW",
+ 0,
+ "special characters",
+ },
+ {
+ "policy_name=test policy_version=999999.0.0\n"
+ "DEFAULT action=ALLOW",
+ -ERANGE,
+ "overflow version",
+ },
+ {
+ "policy_name=test policy_version=255.0\n"
+ "DEFAULT action=ALLOW",
+ -EBADMSG,
+ "incomplete version",
+ },
+ {
+ "policy_name=test policy_version=111.0.0.0\n"
+ "DEFAULT action=ALLOW",
+ -EBADMSG,
+ "extra version",
+ },
+ {
+ "",
+ -EBADMSG,
+ "0-length policy",
+ },
+ {
+ "policy_name=test\0policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW",
+ -EBADMSG,
+ "random null in header",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "\0DEFAULT action=ALLOW",
+ -EBADMSG,
+ "incomplete policy from NULL",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=DENY\n\0"
+ "op=EXECUTE dmverity_signature=TRUE action=ALLOW\n",
+ 0,
+ "NULL truncates policy",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE dmverity_signature=abc action=ALLOW",
+ -EBADMSG,
+ "invalid property type",
+ },
+ {
+ "DEFAULT action=ALLOW",
+ -EBADMSG,
+ "missing policy header",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n",
+ -EBADMSG,
+ "missing default definition",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "dmverity_signature=TRUE op=EXECUTE action=ALLOW",
+ -EBADMSG,
+ "invalid rule ordering"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "action=ALLOW op=EXECUTE dmverity_signature=TRUE",
+ -EBADMSG,
+ "invalid rule ordering (2)",
+ },
+ {
+ "policy_name=test policy_version=0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE dmverity_signature=TRUE action=ALLOW",
+ -EBADMSG,
+ "invalid version",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=UNKNOWN dmverity_signature=TRUE action=ALLOW",
+ -EBADMSG,
+ "unknown operation",
+ },
+ {
+ "policy_name=asdvpolicy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n",
+ -EBADMSG,
+ "missing space after policy name",
+ },
+ {
+ "policy_name=test\xFF\xEF policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE dmverity_signature=TRUE action=ALLOW",
+ 0,
+ "expanded ascii",
+ },
+ {
+ "policy_name=test\xFF\xEF policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE dmverity_roothash=GOOD_DOG action=ALLOW",
+ -EBADMSG,
+ "invalid property value (2)",
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "policy_name=test policy_version=0.1.0\n"
+ "DEFAULT action=ALLOW",
+ -EBADMSG,
+ "double header"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "DEFAULT action=ALLOW\n",
+ -EBADMSG,
+ "double default"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "DEFAULT op=EXECUTE action=DENY\n"
+ "DEFAULT op=EXECUTE action=ALLOW\n",
+ -EBADMSG,
+ "double operation default"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "DEFAULT op=EXECUTE action=DEN\n",
+ -EBADMSG,
+ "invalid action value"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "DEFAULT op=EXECUTE action\n",
+ -EBADMSG,
+ "invalid action value (2)"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "UNKNOWN value=true\n",
+ -EBADMSG,
+ "unrecognized statement"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE dmverity_roothash=1c0d7ee1f8343b7fbe418378e8eb22c061d7dec7 action=DENY\n",
+ -EBADMSG,
+ "old-style digest"
+ },
+ {
+ "policy_name=test policy_version=0.0.0\n"
+ "DEFAULT action=ALLOW\n"
+ "op=EXECUTE fsverity_digest=1c0d7ee1f8343b7fbe418378e8eb22c061d7dec7 action=DENY\n",
+ -EBADMSG,
+ "old-style digest"
+ }
+};
+
+static void pol_to_desc(const struct policy_case *c, char *desc)
+{
+ strscpy(desc, c->desc, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(ipe_policies, policy_cases, pol_to_desc);
+
+/**
+ * ipe_parser_unsigned_test - Test the parser by passing unsigned policies.
+ * @test: Supplies a pointer to a kunit structure.
+ *
+ * This is called by the kunit harness. This test does not check the correctness
+ * of the policy, but ensures that errors are handled correctly.
+ */
+static void ipe_parser_unsigned_test(struct kunit *test)
+{
+ const struct policy_case *p = test->param_value;
+ struct ipe_policy *pol = ipe_new_policy(p->policy, strlen(p->policy), NULL, 0);
+
+ if (p->errno) {
+ KUNIT_EXPECT_EQ(test, PTR_ERR(pol), p->errno);
+ return;
+ }
+
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pol);
+ KUNIT_EXPECT_NOT_ERR_OR_NULL(test, pol->parsed);
+ KUNIT_EXPECT_STREQ(test, pol->text, p->policy);
+ KUNIT_EXPECT_PTR_EQ(test, NULL, pol->pkcs7);
+ KUNIT_EXPECT_EQ(test, 0, pol->pkcs7len);
+
+ ipe_free_policy(pol);
+}
+
+/**
+ * ipe_parser_widestring_test - Ensure parser fail on a wide string policy.
+ * @test: Supplies a pointer to a kunit structure.
+ *
+ * This is called by the kunit harness.
+ */
+static void ipe_parser_widestring_test(struct kunit *test)
+{
+ struct ipe_policy *pol = NULL;
+ const unsigned short policy[] = L"policy_name=Test policy_version=0.0.0\n"
+ L"DEFAULT action=ALLOW";
+
+ pol = ipe_new_policy((const char *)policy, (ARRAY_SIZE(policy) - 1) * 2, NULL, 0);
+ KUNIT_EXPECT_TRUE(test, IS_ERR_OR_NULL(pol));
+
+ ipe_free_policy(pol);
+}
+
+static struct kunit_case ipe_parser_test_cases[] = {
+ KUNIT_CASE_PARAM(ipe_parser_unsigned_test, ipe_policies_gen_params),
+ KUNIT_CASE(ipe_parser_widestring_test),
+};
+
+static struct kunit_suite ipe_parser_test_suite = {
+ .name = "ipe-parser",
+ .test_cases = ipe_parser_test_cases,
+};
+
+kunit_test_suite(ipe_parser_test_suite);
--
2.25.1
This patch adds a target finalize hook.
The hook is triggered just before activating an inactive table of a
mapped device. If it returns an error the __bind get cancelled.
The dm-verity target will use this hook to attach the dm-verity's
roothash metadata to the block_device struct of the mapped device.
Signed-off-by: Fan Wu <[email protected]>
---
v1-v10:
+ Not present
---
drivers/md/dm.c | 12 ++++++++++++
include/linux/device-mapper.h | 7 +++++++
2 files changed, 19 insertions(+)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 64a1f306c96c..3be9cc35306d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2239,6 +2239,18 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
goto out;
}
+ for (unsigned int i = 0; i < t->num_targets; i++) {
+ struct dm_target *ti = dm_table_get_target(t, i);
+
+ if (ti->type->finalize) {
+ ret = ti->type->finalize(ti);
+ if (ret) {
+ old_map = ERR_PTR(ret);
+ goto out;
+ }
+ }
+ }
+
old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
rcu_assign_pointer(md->map, (void *)t);
md->immutable_target_type = dm_table_get_immutable_target_type(t);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 69d0435c7ebb..4040e84a8ec7 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -160,6 +160,12 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff,
*/
typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff,
void *addr, size_t bytes, struct iov_iter *i);
+/*
+ * Returns:
+ * < 0 : error
+ * = 0 : success
+ */
+typedef int (*dm_finalize_fn) (struct dm_target *target);
void dm_error(const char *message);
@@ -209,6 +215,7 @@ struct target_type {
dm_dax_direct_access_fn direct_access;
dm_dax_zero_page_range_fn dax_zero_page_range;
dm_dax_recovery_write_fn dax_recovery_write;
+ dm_finalize_fn finalize;
/* For internal device-mapper use. */
struct list_head list;
--
2.25.1
From: Deven Bowers <[email protected]>
As is typical with LSMs, IPE uses securityfs as its interface with
userspace. for a complete list of the interfaces and the respective
inputs/outputs, please see the documentation under
admin-guide/LSM/ipe.rst
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks,
and evaluation loop from policy parser and userspace
interface to pass mailing list character limit
v3:
+ Move policy load and activation audit event to 03/12
+ Fix a potential panic when a policy failed to load.
+ use pr_warn for a failure to parse instead of an
audit record
+ Remove comments from headers
+ Add lockdep assertions to ipe_update_active_policy and
ipe_activate_policy
+ Fix up warnings with checkpatch --strict
+ Use file_ns_capable for CAP_MAC_ADMIN for securityfs
nodes.
+ Use memdup_user instead of kzalloc+simple_write_to_buffer.
+ Remove strict_parse command line parameter, as it is added
by the sysctl command line.
+ Prefix extern variables with ipe_
v4:
+ Remove securityfs to reverse-dependency
+ Add SHA1 reverse dependency.
+ Add versioning scheme for IPE properties, and associated
interface to query the versioning scheme.
+ Cause a parser to always return an error on unknown syntax.
+ Remove strict_parse option
+ Change active_policy interface from sysctl, to securityfs,
and change scheme.
v5:
+ Cause an error if a default action is not defined for each
operation.
+ Minor function renames
v6:
+ No changes
v7:
+ Propagating changes to support the new ipe_context structure in the
evaluation loop.
+ Further split the parser and userspace interface changes into
separate commits.
+ "raw" was renamed to "pkcs7" and made read only
+ "raw"'s write functionality (update a policy) moved to "update"
+ introduced "version", "policy_name" nodes.
+ "content" renamed to "policy"
+ changes to allow the compiled-in policy to be treated
identical to deployed-after-the-fact policies.
v8:
+ Prevent securityfs initialization if the LSM is disabled
v9:
+ Switch to securityfs_recursive_remove for policy folder deletion
v10:
+ Simplify and correct concurrency
+ Fix typos
v11:
+ Correct code comments
---
security/ipe/Makefile | 2 +
security/ipe/fs.c | 101 ++++++++
security/ipe/fs.h | 16 ++
security/ipe/ipe.c | 3 +
security/ipe/ipe.h | 2 +
security/ipe/policy.c | 112 +++++++++
security/ipe/policy.h | 9 +
security/ipe/policy_fs.c | 481 +++++++++++++++++++++++++++++++++++++++
8 files changed, 726 insertions(+)
create mode 100644 security/ipe/fs.c
create mode 100644 security/ipe/fs.h
create mode 100644 security/ipe/policy_fs.c
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index d7f2870d7c09..cfbed03a8885 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -8,6 +8,8 @@
obj-$(CONFIG_SECURITY_IPE) += \
eval.o \
hooks.o \
+ fs.o \
ipe.o \
policy.o \
+ policy_fs.o \
policy_parser.o \
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
new file mode 100644
index 000000000000..522162af741a
--- /dev/null
+++ b/security/ipe/fs.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/dcache.h>
+#include <linux/security.h>
+
+#include "ipe.h"
+#include "fs.h"
+#include "policy.h"
+
+static struct dentry *np __ro_after_init;
+static struct dentry *root __ro_after_init;
+struct dentry *policy_root __ro_after_init;
+
+/**
+ * new_policy - Write handler for the securityfs node, "ipe/new_policy".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t new_policy(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ char *copy = NULL;
+ struct ipe_policy *p = NULL;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ copy = memdup_user_nul(data, len);
+ if (IS_ERR(copy))
+ return PTR_ERR(copy);
+
+ p = ipe_new_policy(NULL, 0, copy, len);
+ if (IS_ERR(p)) {
+ rc = PTR_ERR(p);
+ goto out;
+ }
+
+ rc = ipe_new_policyfs_node(p);
+
+out:
+ if (rc < 0 && !IS_ERR(p))
+ ipe_free_policy(p);
+ kfree(copy);
+ return (rc < 0) ? rc : len;
+}
+
+static const struct file_operations np_fops = {
+ .write = new_policy,
+};
+
+/**
+ * ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
+ *
+ * Return:
+ * * !0 - Error
+ * * 0 - OK
+ */
+static int __init ipe_init_securityfs(void)
+{
+ int rc = 0;
+
+ if (!ipe_enabled)
+ return -EOPNOTSUPP;
+
+ root = securityfs_create_dir("ipe", NULL);
+ if (IS_ERR(root)) {
+ rc = PTR_ERR(root);
+ goto err;
+ }
+
+ policy_root = securityfs_create_dir("policies", root);
+ if (IS_ERR(policy_root)) {
+ rc = PTR_ERR(policy_root);
+ goto err;
+ }
+
+ np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops);
+ if (IS_ERR(np)) {
+ rc = PTR_ERR(np);
+ goto err;
+ }
+
+ return 0;
+err:
+ securityfs_remove(np);
+ securityfs_remove(policy_root);
+ securityfs_remove(root);
+ return rc;
+}
+
+fs_initcall(ipe_init_securityfs);
diff --git a/security/ipe/fs.h b/security/ipe/fs.h
new file mode 100644
index 000000000000..c1fc0ca4ae93
--- /dev/null
+++ b/security/ipe/fs.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_FS_H
+#define _IPE_FS_H
+
+#include "policy.h"
+
+extern struct dentry *policy_root __ro_after_init;
+
+int ipe_new_policyfs_node(struct ipe_policy *p);
+void ipe_del_policyfs_node(struct ipe_policy *p);
+
+#endif /* _IPE_FS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 06da94a58aba..783058c06cd6 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -6,6 +6,8 @@
#include "ipe.h"
#include "hooks.h"
+bool ipe_enabled;
+
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
};
@@ -31,6 +33,7 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
static int __init ipe_init(void)
{
security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), "ipe");
+ ipe_enabled = true;
return 0;
}
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index a1c68d0fc2e0..6dec06403eee 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -13,4 +13,6 @@
#include <linux/lsm_hooks.h>
+extern bool ipe_enabled;
+
#endif /* _IPE_H */
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index 3a529c7950a1..33bbc43f0d6f 100644
--- a/security/ipe/policy.c
+++ b/security/ipe/policy.c
@@ -7,9 +7,36 @@
#include <linux/verification.h>
#include "ipe.h"
+#include "eval.h"
+#include "fs.h"
#include "policy.h"
#include "policy_parser.h"
+/* lock for synchronizing writers across ipe policy */
+DEFINE_MUTEX(ipe_policy_lock);
+
+/**
+ * ver_to_u64 - Convert an internal ipe_policy_version to a u64.
+ * @p: Policy to extract the version from.
+ *
+ * Bits (LSB is index 0):
+ * [48,32] -> Major
+ * [32,16] -> Minor
+ * [16, 0] -> Revision
+ *
+ * Return: u64 version of the embedded version structure.
+ */
+static inline u64 ver_to_u64(const struct ipe_policy *const p)
+{
+ u64 r;
+
+ r = (((u64)p->parsed->version.major) << 32)
+ | (((u64)p->parsed->version.minor) << 16)
+ | ((u64)(p->parsed->version.rev));
+
+ return r;
+}
+
/**
* ipe_free_policy - Deallocate a given IPE policy.
* @p: Supplies the policy to free.
@@ -21,6 +48,7 @@ void ipe_free_policy(struct ipe_policy *p)
if (IS_ERR_OR_NULL(p))
return;
+ ipe_del_policyfs_node(p);
free_parsed_policy(p->parsed);
/*
* p->text is allocated only when p->pkcs7 is not NULL
@@ -43,6 +71,65 @@ static int set_pkcs7_data(void *ctx, const void *data, size_t len,
return 0;
}
+/**
+ * ipe_update_policy - parse a new policy and replace old with it.
+ * @root: Supplies a pointer to the securityfs inode saved the policy.
+ * @text: Supplies a pointer to the plain text policy.
+ * @textlen: Supplies the length of @text.
+ * @pkcs7: Supplies a pointer to a buffer containing a pkcs7 message.
+ * @pkcs7len: Supplies the length of @pkcs7len.
+ *
+ * @text/@textlen is mutually exclusive with @pkcs7/@pkcs7len - see
+ * ipe_new_policy.
+ *
+ * Context: Requires root->i_rwsem and ipe_policy_lock to be held.
+ * Return:
+ * * !IS_ERR - The existing policy saved in the inode before update
+ * * -ENOENT - Policy doesn't exist
+ * * -EINVAL - New policy is invalid
+ */
+struct ipe_policy *ipe_update_policy(struct inode *root,
+ const char *text, size_t textlen,
+ const char *pkcs7, size_t pkcs7len)
+{
+ int rc = 0;
+ struct ipe_policy *old, *ap, *new = NULL;
+
+ lockdep_assert_held(&ipe_policy_lock);
+
+ old = (struct ipe_policy *)root->i_private;
+ if (!old)
+ return ERR_PTR(-ENOENT);
+
+ new = ipe_new_policy(text, textlen, pkcs7, pkcs7len);
+ if (IS_ERR(new))
+ return new;
+
+ if (strcmp(new->parsed->name, old->parsed->name)) {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ if (ver_to_u64(old) > ver_to_u64(new)) {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ root->i_private = new;
+
+ ap = rcu_dereference_protected(ipe_active_policy,
+ lockdep_is_held(&ipe_policy_lock));
+ if (old == ap)
+ rcu_assign_pointer(ipe_active_policy, new);
+
+ swap(new->policyfs, old->policyfs);
+
+ return old;
+err:
+ ipe_free_policy(new);
+ return ERR_PTR(rc);
+}
+
/**
* ipe_new_policy - Allocate and parse an ipe_policy structure.
*
@@ -99,3 +186,28 @@ struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
ipe_free_policy(new);
return ERR_PTR(rc);
}
+
+/**
+ * ipe_set_active_pol - Make @p the active policy.
+ * @p: Supplies a pointer to the policy to make active.
+ *
+ * Context: Requires root->i_rwsem and ipe_policy_lock to be held.
+ * Return:
+ * * !IS_ERR - Success
+ * * -EINVAL - New active policy version is invalid
+ */
+int ipe_set_active_pol(const struct ipe_policy *p)
+{
+ struct ipe_policy *ap = NULL;
+
+ lockdep_assert_held(&ipe_policy_lock);
+
+ ap = rcu_dereference_protected(ipe_active_policy,
+ lockdep_is_held(&ipe_policy_lock));
+ if (ap && ver_to_u64(ap) > ver_to_u64(p))
+ return -EINVAL;
+
+ rcu_assign_pointer(ipe_active_policy, p);
+
+ return 0;
+}
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index 45704465dc01..32e5e0b941eb 100644
--- a/security/ipe/policy.h
+++ b/security/ipe/policy.h
@@ -7,6 +7,7 @@
#include <linux/list.h>
#include <linux/types.h>
+#include <linux/fs.h>
enum ipe_op_type {
IPE_OP_EXEC = 0,
@@ -76,10 +77,18 @@ struct ipe_policy {
size_t textlen;
struct ipe_parsed_policy *parsed;
+
+ struct dentry *policyfs;
};
struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
const char *pkcs7, size_t pkcs7len);
void ipe_free_policy(struct ipe_policy *pol);
+struct ipe_policy *ipe_update_policy(struct inode *root,
+ const char *text,
+ size_t textlen, const char *pkcs7,
+ size_t pkcs7len);
+int ipe_set_active_pol(const struct ipe_policy *p);
+extern struct mutex ipe_policy_lock;
#endif /* _IPE_POLICY_H */
diff --git a/security/ipe/policy_fs.c b/security/ipe/policy_fs.c
new file mode 100644
index 000000000000..52a120118cda
--- /dev/null
+++ b/security/ipe/policy_fs.c
@@ -0,0 +1,481 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/types.h>
+#include <linux/dcache.h>
+#include <linux/security.h>
+
+#include "ipe.h"
+#include "policy.h"
+#include "eval.h"
+#include "fs.h"
+
+#define MAX_VERSION_SIZE ARRAY_SIZE("65535.65535.65535")
+
+/**
+ * ipefs_file - defines a file in securityfs.
+ */
+struct ipefs_file {
+ const char *name;
+ umode_t access;
+ const struct file_operations *fops;
+};
+
+/**
+ * read_pkcs7 - Read handler for "ipe/policies/$name/pkcs7".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the pkcs7 blob representing the policy
+ * on success. If the policy is unsigned (like the boot policy), this
+ * will return -ENOENT.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_pkcs7(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ if (!p->pkcs7) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = simple_read_from_buffer(data, len, offset, p->pkcs7, p->pkcs7len);
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * read_policy - Read handler for "ipe/policies/$name/policy".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the plain-text version of the policy
+ * on success.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_policy(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = simple_read_from_buffer(data, len, offset, p->text, p->textlen);
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * read_name: Read handler for "ipe/policies/$name/name".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the policy_name attribute on success.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_name(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = simple_read_from_buffer(data, len, offset, p->parsed->name,
+ strlen(p->parsed->name));
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * read_version - Read handler for "ipe/policies/$name/version".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the version string on success.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_version(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ ssize_t rc = 0;
+ size_t bufsize = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+ char buffer[MAX_VERSION_SIZE] = { 0 };
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ bufsize = scnprintf(buffer, ARRAY_SIZE(buffer), "%hu.%hu.%hu",
+ p->parsed->version.major, p->parsed->version.minor,
+ p->parsed->version.rev);
+
+ rc = simple_read_from_buffer(data, len, offset, buffer, bufsize);
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * setactive - Write handler for "ipe/policies/$name/active".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t setactive(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ bool value = false;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ rc = kstrtobool_from_user(data, len, &value);
+ if (rc)
+ return rc;
+
+ if (!value)
+ return -EINVAL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+ inode_lock(root);
+ mutex_lock(&ipe_policy_lock);
+
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = ipe_set_active_pol(p);
+
+out:
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+ synchronize_rcu();
+ return (rc < 0) ? rc : len;
+}
+
+/**
+ * getactive - Read handler for "ipe/policies/$name/active".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Suppleis a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the 1 or 0 depending on if the
+ * corresponding policy is active.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getactive(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ const char *str;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ inode_unlock_shared(root);
+ return -ENOENT;
+ }
+ inode_unlock_shared(root);
+
+ str = (p == rcu_access_pointer(ipe_active_policy)) ? "1" : "0";
+ rc = simple_read_from_buffer(data, len, offset, str, 1);
+
+ return rc;
+}
+
+/**
+ * update_policy - Write handler for "ipe/policies/$name/update".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * On success this updates the policy represented by $name,
+ * in-place.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t update_policy(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ char *copy = NULL;
+ struct inode *root = NULL;
+ struct ipe_policy *old = NULL;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ copy = memdup_user(data, len);
+ if (IS_ERR(copy))
+ return PTR_ERR(copy);
+
+ root = d_inode(f->f_path.dentry->d_parent);
+ inode_lock(root);
+ mutex_lock(&ipe_policy_lock);
+ old = ipe_update_policy(root, NULL, 0, copy, len);
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+ synchronize_rcu();
+
+ kfree(copy);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+ ipe_free_policy(old);
+
+ return len;
+}
+
+/**
+ * delete_policy - write handler for "ipe/policies/$name/delete".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * On success this deletes the policy represented by $name.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t delete_policy(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ bool value = false;
+ struct inode *root = NULL;
+ struct ipe_policy *p = NULL;
+ struct ipe_policy *ap = NULL;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ rc = kstrtobool_from_user(data, len, &value);
+ if (rc)
+ return rc;
+
+ if (!value)
+ return -EINVAL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+ inode_lock(root);
+ mutex_lock(&ipe_policy_lock);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+ return -ENOENT;
+ }
+
+ ap = rcu_dereference_protected(ipe_active_policy,
+ lockdep_is_held(&ipe_policy_lock));
+ if (p == ap) {
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+ return -EPERM;
+ }
+ root->i_private = NULL;
+
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+ synchronize_rcu();
+
+ ipe_free_policy(p);
+ return len;
+}
+
+static const struct file_operations content_fops = {
+ .read = read_policy,
+};
+
+static const struct file_operations pkcs7_fops = {
+ .read = read_pkcs7,
+};
+
+static const struct file_operations name_fops = {
+ .read = read_name,
+};
+
+static const struct file_operations ver_fops = {
+ .read = read_version,
+};
+
+static const struct file_operations active_fops = {
+ .write = setactive,
+ .read = getactive,
+};
+
+static const struct file_operations update_fops = {
+ .write = update_policy,
+};
+
+static const struct file_operations delete_fops = {
+ .write = delete_policy,
+};
+
+/**
+ * policy_subdir - files under a policy subdirectory
+ */
+static const struct ipefs_file policy_subdir[] = {
+ { "pkcs7", 0444, &pkcs7_fops },
+ { "policy", 0444, &content_fops },
+ { "name", 0444, &name_fops },
+ { "version", 0444, &ver_fops },
+ { "active", 0600, &active_fops },
+ { "update", 0200, &update_fops },
+ { "delete", 0200, &delete_fops },
+};
+
+/**
+ * ipe_del_policyfs_node - Delete a securityfs entry for @p.
+ * @p: Supplies a pointer to the policy to delete a securityfs entry for.
+ */
+void ipe_del_policyfs_node(struct ipe_policy *p)
+{
+ securityfs_recursive_remove(p->policyfs);
+ p->policyfs = NULL;
+}
+
+/**
+ * ipe_new_policyfs_node - Create a securityfs entry for @p.
+ * @p: Supplies a pointer to the policy to create a securityfs entry for.
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Error
+ */
+int ipe_new_policyfs_node(struct ipe_policy *p)
+{
+ int rc = 0;
+ size_t i = 0;
+ struct dentry *d = NULL;
+ struct dentry *policyfs = NULL;
+ struct inode *root = NULL;
+ const struct ipefs_file *f = NULL;
+
+ if (p->policyfs)
+ return 0;
+
+ policyfs = securityfs_create_dir(p->parsed->name, policy_root);
+ if (IS_ERR(policyfs)) {
+ rc = PTR_ERR(policyfs);
+ goto err;
+ }
+
+ root = d_inode(policyfs);
+
+ for (i = 0; i < ARRAY_SIZE(policy_subdir); ++i) {
+ f = &policy_subdir[i];
+
+ d = securityfs_create_file(f->name, f->access, policyfs,
+ NULL, f->fops);
+ if (IS_ERR(d)) {
+ rc = PTR_ERR(d);
+ goto err;
+ }
+ }
+
+ inode_lock(root);
+ mutex_lock(&ipe_policy_lock);
+ p->policyfs = policyfs;
+ root->i_private = p;
+ mutex_unlock(&ipe_policy_lock);
+ inode_unlock(root);
+
+ return 0;
+err:
+ securityfs_recursive_remove(policyfs);
+ return rc;
+}
--
2.25.1
From: Deven Bowers <[email protected]>
IPE's interpretation of the what the user trusts is accomplished through
its policy. IPE's design is to not provide support for a single trust
provider, but to support multiple providers to enable the end-user to
choose the best one to seek their needs.
This requires the policy to be rather flexible and modular so that
integrity providers, like fs-verity, dm-verity, dm-integrity, or
some other system, can plug into the policy with minimal code changes.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks,
and evaluation loop from policy parser and userspace
interface to pass mailing list character limit
v3:
+ Move policy load and activation audit event to 03/12
+ Fix a potential panic when a policy failed to load.
+ use pr_warn for a failure to parse instead of an
audit record
+ Remove comments from headers
+ Add lockdep assertions to ipe_update_active_policy and
ipe_activate_policy
+ Fix up warnings with checkpatch --strict
+ Use file_ns_capable for CAP_MAC_ADMIN for securityfs
nodes.
+ Use memdup_user instead of kzalloc+simple_write_to_buffer.
+ Remove strict_parse command line parameter, as it is added
by the sysctl command line.
+ Prefix extern variables with ipe_
v4:
+ Remove securityfs to reverse-dependency
+ Add SHA1 reverse dependency.
+ Add versioning scheme for IPE properties, and associated
interface to query the versioning scheme.
+ Cause a parser to always return an error on unknown syntax.
+ Remove strict_parse option
+ Change active_policy interface from sysctl, to securityfs,
and change scheme.
v5:
+ Cause an error if a default action is not defined for each
operation.
+ Minor function renames
v6:
+ No changes
v7:
+ Further split parser and userspace interface into two
separate commits, for easier review.
+ Refactor policy parser to make code cleaner via introducing a
more modular design, for easier extension of policy, and
easier review.
v8:
+ remove unnecessary pr_info emission on parser loading
+ add explicit newline to the pr_err emitted when a parser
fails to load.
v9:
+ switch to match table to parse policy
+ remove quote syntax and KERNEL_READ operation
v10:
+ Fix memory leaks in parser
+ Fix typos and change code styles
v11:
+ Fix code style issues
---
security/ipe/Makefile | 2 +
security/ipe/policy.c | 101 ++++++++
security/ipe/policy.h | 83 ++++++
security/ipe/policy_parser.c | 487 +++++++++++++++++++++++++++++++++++
security/ipe/policy_parser.h | 11 +
5 files changed, 684 insertions(+)
create mode 100644 security/ipe/policy.c
create mode 100644 security/ipe/policy.h
create mode 100644 security/ipe/policy_parser.c
create mode 100644 security/ipe/policy_parser.h
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index f7a80d0f18f8..c09aec4904f2 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -7,3 +7,5 @@
obj-$(CONFIG_SECURITY_IPE) += \
ipe.o \
+ policy.o \
+ policy_parser.o \
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
new file mode 100644
index 000000000000..3a529c7950a1
--- /dev/null
+++ b/security/ipe/policy.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/errno.h>
+#include <linux/verification.h>
+
+#include "ipe.h"
+#include "policy.h"
+#include "policy_parser.h"
+
+/**
+ * ipe_free_policy - Deallocate a given IPE policy.
+ * @p: Supplies the policy to free.
+ *
+ * Safe to call on IS_ERR/NULL.
+ */
+void ipe_free_policy(struct ipe_policy *p)
+{
+ if (IS_ERR_OR_NULL(p))
+ return;
+
+ free_parsed_policy(p->parsed);
+ /*
+ * p->text is allocated only when p->pkcs7 is not NULL
+ * otherwise it points to the plaintext data inside the pkcs7
+ */
+ if (!p->pkcs7)
+ kfree(p->text);
+ kfree(p->pkcs7);
+ kfree(p);
+}
+
+static int set_pkcs7_data(void *ctx, const void *data, size_t len,
+ size_t asn1hdrlen)
+{
+ struct ipe_policy *p = ctx;
+
+ p->text = (const char *)data;
+ p->textlen = len;
+
+ return 0;
+}
+
+/**
+ * ipe_new_policy - Allocate and parse an ipe_policy structure.
+ *
+ * @text: Supplies a pointer to the plain-text policy to parse.
+ * @textlen: Supplies the length of @text.
+ * @pkcs7: Supplies a pointer to a pkcs7-signed IPE policy.
+ * @pkcs7len: Supplies the length of @pkcs7.
+ *
+ * @text/@textlen Should be NULL/0 if @pkcs7/@pkcs7len is set.
+ *
+ * Return:
+ * * !IS_ERR - Success
+ * * -EBADMSG - Policy is invalid
+ * * -ENOMEM - Out of memory
+ */
+struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
+ const char *pkcs7, size_t pkcs7len)
+{
+ int rc = 0;
+ struct ipe_policy *new = NULL;
+
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return ERR_PTR(-ENOMEM);
+
+ if (!text) {
+ new->pkcs7len = pkcs7len;
+ new->pkcs7 = kmemdup(pkcs7, pkcs7len, GFP_KERNEL);
+ if (!new->pkcs7) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL,
+ VERIFYING_UNSPECIFIED_SIGNATURE,
+ set_pkcs7_data, new);
+ if (rc)
+ goto err;
+ } else {
+ new->textlen = textlen;
+ new->text = kstrdup(text, GFP_KERNEL);
+ if (!new->text) {
+ rc = -ENOMEM;
+ goto err;
+ }
+ }
+
+ rc = parse_policy(new);
+ if (rc)
+ goto err;
+
+ return new;
+err:
+ ipe_free_policy(new);
+ return ERR_PTR(rc);
+}
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
new file mode 100644
index 000000000000..77aa91f2b953
--- /dev/null
+++ b/security/ipe/policy.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_POLICY_H
+#define _IPE_POLICY_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+
+enum ipe_op_type {
+ IPE_OP_EXEC = 0,
+ IPE_OP_FIRMWARE,
+ IPE_OP_KERNEL_MODULE,
+ IPE_OP_KEXEC_IMAGE,
+ IPE_OP_KEXEC_INITRAMFS,
+ IPE_OP_IMA_POLICY,
+ IPE_OP_IMA_X509,
+ __IPE_OP_MAX
+};
+
+#define IPE_OP_INVALID __IPE_OP_MAX
+
+enum ipe_action_type {
+ IPE_ACTION_ALLOW = 0,
+ IPE_ACTION_DENY,
+ __IPE_ACTION_MAX
+};
+
+#define IPE_ACTION_INVALID __IPE_ACTION_MAX
+
+enum ipe_prop_type {
+ __IPE_PROP_MAX
+};
+
+#define IPE_PROP_INVALID __IPE_PROP_MAX
+
+struct ipe_prop {
+ struct list_head next;
+ enum ipe_prop_type type;
+ void *value;
+};
+
+struct ipe_rule {
+ enum ipe_op_type op;
+ enum ipe_action_type action;
+ struct list_head props;
+ struct list_head next;
+};
+
+struct ipe_op_table {
+ struct list_head rules;
+ enum ipe_action_type default_action;
+};
+
+struct ipe_parsed_policy {
+ const char *name;
+ struct {
+ u16 major;
+ u16 minor;
+ u16 rev;
+ } version;
+
+ enum ipe_action_type global_default_action;
+
+ struct ipe_op_table rules[__IPE_OP_MAX];
+};
+
+struct ipe_policy {
+ const char *pkcs7;
+ size_t pkcs7len;
+
+ const char *text;
+ size_t textlen;
+
+ struct ipe_parsed_policy *parsed;
+};
+
+struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
+ const char *pkcs7, size_t pkcs7len);
+void ipe_free_policy(struct ipe_policy *pol);
+
+#endif /* _IPE_POLICY_H */
diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
new file mode 100644
index 000000000000..c09458bd348d
--- /dev/null
+++ b/security/ipe/policy_parser.c
@@ -0,0 +1,487 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/parser.h>
+#include <linux/types.h>
+
+#include "policy.h"
+#include "policy_parser.h"
+
+#define START_COMMENT '#'
+#define IPE_POLICY_DELIM " \t"
+#define IPE_LINE_DELIM "\n\r"
+
+/**
+ * new_parsed_policy - Allocate and initialize a parsed policy.
+ *
+ * Return:
+ * * !IS_ERR - OK
+ * * -ENOMEM - Out of memory
+ */
+static struct ipe_parsed_policy *new_parsed_policy(void)
+{
+ size_t i = 0;
+ struct ipe_parsed_policy *p = NULL;
+ struct ipe_op_table *t = NULL;
+
+ p = kzalloc(sizeof(*p), GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ p->global_default_action = IPE_ACTION_INVALID;
+
+ for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
+ t = &p->rules[i];
+
+ t->default_action = IPE_ACTION_INVALID;
+ INIT_LIST_HEAD(&t->rules);
+ }
+
+ return p;
+}
+
+/**
+ * remove_comment - Truncate all chars following START_COMMENT in a string.
+ *
+ * @line: Supplies a poilcy line string for preprocessing.
+ */
+static void remove_comment(char *line)
+{
+ line = strchr(line, START_COMMENT);
+
+ if (line)
+ *line = '\0';
+}
+
+/**
+ * remove_trailing_spaces - Truncate all trailing spaces in a string.
+ *
+ * @line: Supplies a poilcy line string for preprocessing.
+ *
+ * Return: The length of truncated string.
+ */
+static size_t remove_trailing_spaces(char *line)
+{
+ size_t i = 0;
+
+ for (i = strlen(line); i > 0 && (line[i - 1] == ' ' || line[i - 1] == '\t'); --i)
+ ;
+
+ line[i] = '\0';
+
+ return i;
+}
+
+/**
+ * parse_version - Parse policy version.
+ * @ver: Supplies a version string to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Standard errno
+ */
+static int parse_version(char *ver, struct ipe_parsed_policy *p)
+{
+ int rc = 0;
+ size_t sep_count = 0;
+ char *token;
+ u16 *const cv[] = { &p->version.major, &p->version.minor, &p->version.rev };
+
+ while ((token = strsep(&ver, ".")) != NULL) {
+ /* prevent overflow */
+ if (sep_count >= ARRAY_SIZE(cv))
+ return -EBADMSG;
+
+ rc = kstrtou16(token, 10, cv[sep_count]);
+ if (rc)
+ return rc;
+
+ ++sep_count;
+ }
+
+ /* prevent underflow */
+ if (sep_count != ARRAY_SIZE(cv))
+ rc = -EBADMSG;
+
+ return rc;
+}
+
+enum header_opt {
+ IPE_HEADER_POLICY_NAME = 0,
+ IPE_HEADER_POLICY_VERSION,
+ __IPE_HEADER_MAX
+};
+
+static const match_table_t header_tokens = {
+ {IPE_HEADER_POLICY_NAME, "policy_name=%s"},
+ {IPE_HEADER_POLICY_VERSION, "policy_version=%s"},
+ {__IPE_HEADER_MAX, NULL}
+};
+
+/**
+ * parse_header - Parse policy header information.
+ * @line: Supplies header line to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Standard errno
+ */
+static int parse_header(char *line, struct ipe_parsed_policy *p)
+{
+ int rc = 0;
+ char *t, *ver = NULL;
+ substring_t args[MAX_OPT_ARGS];
+ size_t idx = 0;
+
+ while ((t = strsep(&line, IPE_POLICY_DELIM)) != NULL) {
+ int token;
+
+ if (*t == '\0')
+ continue;
+ if (idx >= __IPE_HEADER_MAX) {
+ rc = -EBADMSG;
+ goto out;
+ }
+
+ token = match_token(t, header_tokens, args);
+ if (token != idx) {
+ rc = -EBADMSG;
+ goto out;
+ }
+
+ switch (token) {
+ case IPE_HEADER_POLICY_NAME:
+ p->name = match_strdup(&args[0]);
+ if (!p->name)
+ rc = -ENOMEM;
+ break;
+ case IPE_HEADER_POLICY_VERSION:
+ ver = match_strdup(&args[0]);
+ if (!ver) {
+ rc = -ENOMEM;
+ break;
+ }
+ rc = parse_version(ver, p);
+ break;
+ default:
+ rc = -EBADMSG;
+ }
+ if (rc)
+ goto out;
+ ++idx;
+ }
+
+ if (idx != __IPE_HEADER_MAX) {
+ rc = -EBADMSG;
+ goto out;
+ }
+
+out:
+ kfree(ver);
+ return rc;
+}
+
+/**
+ * token_default - Determine if the given token is "DEFAULT".
+ * @token: Supplies the token string to be compared.
+ *
+ * Return:
+ * * 0 - The token is not "DEFAULT"
+ * * !0 - The token is "DEFAULT"
+ */
+static bool token_default(char *token)
+{
+ return !strcmp(token, "DEFAULT");
+}
+
+/**
+ * free_rule - Free the supplied ipe_rule struct.
+ * @r: Supplies the ipe_rule struct to be freed.
+ *
+ * Free a ipe_rule struct @r. Note @r must be removed from any lists before
+ * calling this function.
+ */
+static void free_rule(struct ipe_rule *r)
+{
+ struct ipe_prop *p, *t;
+
+ if (IS_ERR_OR_NULL(r))
+ return;
+
+ list_for_each_entry_safe(p, t, &r->props, next) {
+ list_del(&p->next);
+ kfree(p);
+ }
+
+ kfree(r);
+}
+
+static const match_table_t operation_tokens = {
+ {IPE_OP_EXEC, "op=EXECUTE"},
+ {IPE_OP_FIRMWARE, "op=FIRMWARE"},
+ {IPE_OP_KERNEL_MODULE, "op=KMODULE"},
+ {IPE_OP_KEXEC_IMAGE, "op=KEXEC_IMAGE"},
+ {IPE_OP_KEXEC_INITRAMFS, "op=KEXEC_INITRAMFS"},
+ {IPE_OP_IMA_POLICY, "op=IMA_POLICY"},
+ {IPE_OP_IMA_X509, "op=IMA_X509_CERT"},
+ {IPE_OP_INVALID, NULL}
+};
+
+/**
+ * parse_operation - Parse the operation type given a token string.
+ * @t: Supplies the token string to be parsed.
+ *
+ * Return: The parsed operation type.
+ */
+static enum ipe_op_type parse_operation(char *t)
+{
+ substring_t args[MAX_OPT_ARGS];
+
+ return match_token(t, operation_tokens, args);
+}
+
+static const match_table_t action_tokens = {
+ {IPE_ACTION_ALLOW, "action=ALLOW"},
+ {IPE_ACTION_DENY, "action=DENY"},
+ {IPE_ACTION_INVALID, NULL}
+};
+
+/**
+ * parse_action - Parse the action type given a token string.
+ * @t: Supplies the token string to be parsed.
+ *
+ * Return: The parsed action type.
+ */
+static enum ipe_action_type parse_action(char *t)
+{
+ substring_t args[MAX_OPT_ARGS];
+
+ return match_token(t, action_tokens, args);
+}
+
+/**
+ * parse_property - Parse the property type given a token string.
+ * @t: Supplies the token string to be parsed.
+ * @r: Supplies the ipe_rule the parsed property will be associated with.
+ *
+ * Return:
+ * * !IS_ERR - OK
+ * * -ENOMEM - Out of memory
+ * * -EBADMSG - The supplied token cannot be parsed
+ */
+static int parse_property(char *t, struct ipe_rule *r)
+{
+ return -EBADMSG;
+}
+
+/**
+ * parse_rule - parse a policy rule line.
+ * @line: Supplies rule line to be parsed.
+ * @p: Supplies the partial parsed policy.
+ *
+ * Return:
+ * * !IS_ERR - OK
+ * * -ENOMEM - Out of memory
+ * * -EBADMSG - Policy syntax error
+ */
+static int parse_rule(char *line, struct ipe_parsed_policy *p)
+{
+ int rc = 0;
+ bool first_token = true, is_default_rule = false;
+ bool op_parsed = false;
+ enum ipe_op_type op = IPE_OP_INVALID;
+ enum ipe_action_type action = IPE_ACTION_INVALID;
+ struct ipe_rule *r = NULL;
+ char *t;
+
+ r = kzalloc(sizeof(*r), GFP_KERNEL);
+ if (!r)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&r->next);
+ INIT_LIST_HEAD(&r->props);
+
+ while (t = strsep(&line, IPE_POLICY_DELIM), line) {
+ if (*t == '\0')
+ continue;
+ if (first_token && token_default(t)) {
+ is_default_rule = true;
+ } else {
+ if (!op_parsed) {
+ op = parse_operation(t);
+ if (op == IPE_OP_INVALID)
+ rc = -EBADMSG;
+ else
+ op_parsed = true;
+ } else {
+ rc = parse_property(t, r);
+ }
+ }
+
+ if (rc)
+ goto err;
+ first_token = false;
+ }
+
+ action = parse_action(t);
+ if (action == IPE_ACTION_INVALID) {
+ rc = -EBADMSG;
+ goto err;
+ }
+
+ if (is_default_rule) {
+ if (!list_empty(&r->props)) {
+ rc = -EBADMSG;
+ } else if (op == IPE_OP_INVALID) {
+ if (p->global_default_action != IPE_ACTION_INVALID)
+ rc = -EBADMSG;
+ else
+ p->global_default_action = action;
+ } else {
+ if (p->rules[op].default_action != IPE_ACTION_INVALID)
+ rc = -EBADMSG;
+ else
+ p->rules[op].default_action = action;
+ }
+ } else if (op != IPE_OP_INVALID && action != IPE_ACTION_INVALID) {
+ r->op = op;
+ r->action = action;
+ } else {
+ rc = -EBADMSG;
+ }
+
+ if (rc)
+ goto err;
+ if (!is_default_rule)
+ list_add_tail(&r->next, &p->rules[op].rules);
+ else
+ free_rule(r);
+
+ return rc;
+err:
+ free_rule(r);
+ return rc;
+}
+
+/**
+ * free_parsed_policy - free a parsed policy structure.
+ * @p: Supplies the parsed policy.
+ */
+void free_parsed_policy(struct ipe_parsed_policy *p)
+{
+ size_t i = 0;
+ struct ipe_rule *pp, *t;
+
+ if (IS_ERR_OR_NULL(p))
+ return;
+
+ for (i = 0; i < ARRAY_SIZE(p->rules); ++i)
+ list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) {
+ list_del(&pp->next);
+ free_rule(pp);
+ }
+
+ kfree(p->name);
+ kfree(p);
+}
+
+/**
+ * validate_policy - validate a parsed policy.
+ * @p: Supplies the fully parsed policy.
+ *
+ * Given a policy structure that was just parsed, validate that all
+ * necessary fields are present, initialized correctly.
+ *
+ * A parsed policy can be in an invalid state for use (a default was
+ * undefined) by just parsing the policy.
+ *
+ * Return:
+ * * 0 - OK
+ * * -EBADMSG - Policy is invalid
+ */
+static int validate_policy(const struct ipe_parsed_policy *p)
+{
+ size_t i = 0;
+
+ if (p->global_default_action != IPE_ACTION_INVALID)
+ return 0;
+
+ for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
+ if (p->rules[i].default_action == IPE_ACTION_INVALID)
+ return -EBADMSG;
+ }
+
+ return 0;
+}
+
+/**
+ * parse_policy - Given a string, parse the string into an IPE policy.
+ * @p: partially filled ipe_policy structure to populate with the result.
+ * it must have text and textlen set.
+ *
+ * Return:
+ * * 0 - OK
+ * * -EBADMSG - Policy is invalid
+ * * -ENOMEM - Out of Memory
+ */
+int parse_policy(struct ipe_policy *p)
+{
+ int rc = 0;
+ size_t len;
+ char *policy = NULL, *dup = NULL;
+ char *line = NULL;
+ bool header_parsed = false;
+ struct ipe_parsed_policy *pp = NULL;
+
+ if (!p->textlen)
+ return -EBADMSG;
+
+ policy = kmemdup_nul(p->text, p->textlen, GFP_KERNEL);
+ if (!policy)
+ return -ENOMEM;
+ dup = policy;
+
+ pp = new_parsed_policy();
+ if (IS_ERR(pp)) {
+ rc = PTR_ERR(pp);
+ goto out;
+ }
+
+ while ((line = strsep(&policy, IPE_LINE_DELIM)) != NULL) {
+ remove_comment(line);
+ len = remove_trailing_spaces(line);
+ if (!len)
+ continue;
+
+ if (!header_parsed) {
+ rc = parse_header(line, pp);
+ if (rc)
+ goto err;
+ header_parsed = true;
+ } else {
+ rc = parse_rule(line, pp);
+ if (rc)
+ goto err;
+ }
+ }
+
+ if (!header_parsed || validate_policy(pp)) {
+ rc = -EBADMSG;
+ goto err;
+ }
+
+ p->parsed = pp;
+
+out:
+ kfree(dup);
+ return rc;
+err:
+ free_parsed_policy(pp);
+ goto out;
+}
diff --git a/security/ipe/policy_parser.h b/security/ipe/policy_parser.h
new file mode 100644
index 000000000000..2b744103d06a
--- /dev/null
+++ b/security/ipe/policy_parser.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_POLICY_PARSER_H
+#define _IPE_POLICY_PARSER_H
+
+int parse_policy(struct ipe_policy *p);
+void free_parsed_policy(struct ipe_parsed_policy *p);
+
+#endif /* _IPE_POLICY_PARSER_H */
--
2.25.1
On 10/4/23 15:09, Fan Wu wrote:
| diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
| index 7afb1ce0cb99..9dd5c4769d79 100644
| --- a/security/ipe/Kconfig
| +++ b/security/ipe/Kconfig
| @@ -30,6 +30,19 @@ config IPE_PROP_DM_VERITY
| that was mounted with a signed root-hash or the volume's
| root hash matches the supplied value in the policy.
|
| + If unsure, answer Y.
| +
| +config IPE_PROP_FS_VERITY
| + bool "Enable property for fs-verity files"
| + depends on FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
| + help
| + This option enables the usage of properties "fsverity_signature"
| + and "fsverity_digest". These properties evaluates to TRUE when
evaluate
| + a file is fsverity enabled and with a signed digest or its
| + diegst matches the supplied value in the policy.
digest
| +
| + if unsure, answer Y.
| +
| endmenu
|
| endif
--
~Randy
On Wed, Oct 04, 2023 at 03:09:42PM -0700, Fan Wu wrote:
> +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> +static int fsverity_inode_setsecurity(struct inode *inode,
> + struct fsverity_descriptor *desc)
> +{
> + return security_inode_setsecurity(inode, FS_VERITY_INODE_SEC_NAME,
> + desc->signature,
> + le32_to_cpu(desc->sig_size), 0);
> +}
Why isn't the type of the second argument 'const struct fsverity_descriptor *'?
- Eric
On 10/4/2023 4:58 PM, Randy Dunlap wrote:
>
>
> On 10/4/23 15:09, Fan Wu wrote:
>
> | diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
> | index 7afb1ce0cb99..9dd5c4769d79 100644
> | --- a/security/ipe/Kconfig
> | +++ b/security/ipe/Kconfig
> | @@ -30,6 +30,19 @@ config IPE_PROP_DM_VERITY
> | that was mounted with a signed root-hash or the volume's
> | root hash matches the supplied value in the policy.
> |
> | + If unsure, answer Y.
> | +
> | +config IPE_PROP_FS_VERITY
> | + bool "Enable property for fs-verity files"
> | + depends on FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
> | + help
> | + This option enables the usage of properties "fsverity_signature"
> | + and "fsverity_digest". These properties evaluates to TRUE when
>
> evaluate
>
> | + a file is fsverity enabled and with a signed digest or its
> | + diegst matches the supplied value in the policy.
>
> digest
>
> | +
> | + if unsure, answer Y.
> | +
> | endmenu
> |
> | endif
>
>
Thanks for catching the typo/error. Not sure why my spell script didn't
find them. Maybe I should consider using a better tool.
-Fan
On 10/4/2023 7:27 PM, Eric Biggers wrote:
> On Wed, Oct 04, 2023 at 03:09:42PM -0700, Fan Wu wrote:
>> +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
>> +static int fsverity_inode_setsecurity(struct inode *inode,
>> + struct fsverity_descriptor *desc)
>> +{
>> + return security_inode_setsecurity(inode, FS_VERITY_INODE_SEC_NAME,
>> + desc->signature,
>> + le32_to_cpu(desc->sig_size), 0);
>> +}
>
> Why isn't the type of the second argument 'const struct fsverity_descriptor *'?
>
> - Eric
Thanks for the suggestion. I agree that adding 'const' here is a better
approach. I will update this in the next version.
-Fan
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> Users of IPE require a way to identify when and why an operation fails,
> allowing them to both respond to violations of policy and be notified
> of potentially malicious actions on their systems with respect to IPE
> itself.
>
> This patch introduces 3 new audit events.
>
> AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation
> of a resource.
> AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy
> has been changed to another loaded policy.
> AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded
> into the kernel.
>
> This patch also adds support for success auditing, allowing users to
> identify why an allow decision was made for a resource. However, it is
> recommended to use this option with caution, as it is quite noisy.
>
> Here are some examples of the new audit record types:
>
> AUDIT_IPE_ACCESS(1420):
>
> audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda"
> ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
>
> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
> ino=2 rule="DEFAULT action=DENY"
>
> audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs"
> ino=131 rule="DEFAULT action=DENY"
>
> The above three records were generated when the active IPE policy only
> allows binaries from the initial booted drive(sda) to run. The three
> identical `hello` binary were placed at different locations, only the
> first hello from sda was allowed.
>
> Field path followed by the file's path name.
>
> Field dev followed by the device name as found in /dev where the file is
> from.
> Note that for device mappers it will use the name `dm-X` instead of
> the name in /dev/mapper.
> For a file in a temp file system, which is not from a device, it will use
> `tmpfs` for the field.
> The implementation of this part is following another existing use case
> LSM_AUDIT_DATA_INODE in security/lsm_audit.c
>
> Field ino followed by the file's inode number.
>
> Field rule followed by the IPE rule made the access decision. The whole
> rule must be audited because the decision is based on the combination of
> all property conditions in the rule.
>
> Along with the syscall audit event, user can know why a blocked
> happened. For example:
>
> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
> ino=2 rule="DEFAULT action=DENY"
> audit[1956]: SYSCALL arch=c000003e syscall=59
> success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0
> a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 auid=4294967295 uid=0
> gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0
> ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null)
>
> The above two records showed bash used execve to run "hello" and got
> blocked by IPE. Note that the IPE records are always prior to a SYSCALL
> record.
>
> AUDIT_IPE_CONFIG_CHANGE(1421):
>
> audit: AUDIT1421
> old_active_pol_name="Allow_All" old_active_pol_version=0.0.0
> old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649
> new_active_pol_name="boot_verified" new_active_pol_version=0.0.0
> new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F
> auid=4294967295 ses=4294967295 lsm=ipe res=1
>
> The above record showed the current IPE active policy switch from
> `Allow_All` to `boot_verified` along with the version and the hash
> digest of the two policies. Note IPE can only have one policy active
> at a time, all access decision evaluation is based on the current active
> policy.
> The normal procedure to deploy a policy is loading the policy to deploy
> into the kernel first, then switch the active policy to it.
>
> AUDIT_IPE_POLICY_LOAD(1422):
>
> audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0
> policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD
> auid=4294967295 ses=4294967295 lsm=ipe res=1
>
> The above record showed a new policy has been loaded into the kernel
> with the policy name, policy version and policy hash.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
>
> v2:
> + Split evaluation loop, access control hooks,
> and evaluation loop from policy parser and userspace
> interface to pass mailing list character limit
>
> v3:
> + Move ipe_load_properties to patch 04.
> + Remove useless 0-initializations
> + Prefix extern variables with ipe_
> + Remove kernel module parameters, as these are
> exposed through sysctls.
> + Add more prose to the IPE base config option
> help text.
> + Use GFP_KERNEL for audit_log_start.
> + Remove unnecessary caching system.
> + Remove comments from headers
> + Use rcu_access_pointer for rcu-pointer null check
> + Remove usage of reqprot; use prot only.
> + Move policy load and activation audit event to 03/12
>
> v4:
> + Remove sysctls in favor of securityfs nodes
> + Re-add kernel module parameters, as these are now
> exposed through securityfs.
> + Refactor property audit loop to a separate function.
>
> v5:
> + fix minor grammatical errors
> + do not group rule by curly-brace in audit record,
> reconstruct the exact rule.
>
> v6:
> + No changes
>
> v7:
> + Further split lsm creation, the audit system, the evaluation loop,
> and access control hooks into separate patches.
> + Further split audit system patch into two separate patches; one
> for include/uapi, and the usage of the new defines.
> + Split out the permissive functionality into another separate patch,
> for easier review.
> + Correct misuse of audit_log_n_untrusted string to audit_log_format
> + Use get_task_comm instead of comm directly.
> + Quote certain audit values
> + Remove unnecessary help text on choice options - these were
> previously
> idented at the wrong level
> + Correct a stale string constant (ctx_ns_enforce to ctx_enforce)
>
> v8:
>
> + Change dependency for CONFIG_AUDIT to CONFIG_AUDITSYSCALL
> + Drop ctx_* prefix
> + Reuse, where appropriate, the audit fields from the field
> dictionary. This transforms:
> ctx_pathname -> path
> ctx_ino -> ino
> ctx_dev -> dev
>
> + Add audit records and event examples to commit description.
> + Remove new_audit_ctx, replace with audit_log_start. All data that
> would provided by new_audit_ctx is already present in the syscall
> audit record, that is always emitted on these actions. The audit
> records should be correlated as such.
> + Change audit types:
> + AUDIT_TRUST_RESULT -> AUDIT_IPE_ACCESS
> + This prevents overloading of the AVC type.
> + AUDIT_TRUST_POLICY_ACTIVATE -> AUDIT_MAC_CONFIG_CHANGE
> + AUDIT_TRUST_POLICY_LOAD -> AUDIT_MAC_POLICY_LOAD
> + There were no significant difference in meaning between
> these types.
>
> + Remove enforcing parameter passed from the context structure
> for AUDIT_IPE_ACCESS.
> + This field can be inferred from the SYSCALL audit event,
> based on the success field.
>
> + Remove all fields already captured in the syscall record. "hook",
> an IPE specific field, can be determined via the syscall field in
> the syscall record itself, so it has been removed.
> + ino, path, and dev in IPE's record refer to the subject of the
> syscall, while the syscall record refers to the calling process.
>
> + remove IPE prefix from policy load/policy activation events
> + fix a bug wherein a policy change audit record was not fired when
> updating a policy
>
> v9:
> + Merge the AUDIT_IPE_ACCESS definition with the audit support commit
> + Change the audit format of policy load and switch
> + Remove the ipe audit kernel switch
>
> v10:
> + Create AUDIT_IPE_CONFIG_CHANGE and AUDIT_IPE_POLICY_LOAD
> + Change field names per upstream feedback
>
> v11:
> + Fix style issues
> ---
> include/uapi/linux/audit.h | 3 +
> security/ipe/Kconfig | 2 +-
> security/ipe/Makefile | 1 +
> security/ipe/audit.c | 195 +++++++++++++++++++++++++++++++++++++
> security/ipe/audit.h | 18 ++++
> security/ipe/eval.c | 32 ++++--
> security/ipe/eval.h | 8 ++
> security/ipe/fs.c | 70 +++++++++++++
> security/ipe/policy.c | 5 +
> 9 files changed, 327 insertions(+), 7 deletions(-)
> create mode 100644 security/ipe/audit.c
> create mode 100644 security/ipe/audit.h
...
> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
> new file mode 100644
> index 000000000000..e123701d5e3b
> --- /dev/null
> +++ b/security/ipe/audit.c
> @@ -0,0 +1,195 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/audit.h>
> +#include <linux/types.h>
> +#include <crypto/hash.h>
> +
> +#include "ipe.h"
> +#include "eval.h"
> +#include "hooks.h"
> +#include "policy.h"
> +#include "audit.h"
> +
> +#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
> +
> +#define IPE_AUDIT_HASH_ALG "sha256"
> +
> +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\
> + "policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\
> + "old_active_pol_version=%hu.%hu.%hu "\
> + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\
> + "new_active_pol_version=%hu.%hu.%hu "\
> + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +
> +static const char *const audit_op_names[__IPE_OP_MAX] = {
> + "EXECUTE",
> + "FIRMWARE",
> + "KMODULE",
> + "KEXEC_IMAGE",
> + "KEXEC_INITRAMFS",
> + "IMA_POLICY",
> + "IMA_X509_CERT",
> +};
> +
> +static const char *const audit_prop_names[__IPE_PROP_MAX] = {
> + "boot_verified=FALSE",
> + "boot_verified=TRUE",
> +};
I would suggest taking the same approach for both @audit_op_names and
@audit_prop_names; either include the field name in the string array
for both or leave it out of both.
> +/**
> + * audit_rule - audit an IPE policy rule approximation.
> + * @ab: Supplies a pointer to the audit_buffer to append to.
> + * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
> + */
> +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
> +{
> + const struct ipe_prop *ptr;
> +
> + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
> +
> + list_for_each_entry(ptr, &r->props, next)
> + audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
> +
> + audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
> +}
> +
> +/**
> + * ipe_audit_match - audit a match for IPE policy.
> + * @ctx: Supplies a pointer to the evaluation context that was used in the
> + * evaluation.
> + * @match_type: Supplies the scope of the match: rule, operation default,
> + * global default.
> + * @act: Supplies the IPE's evaluation decision, deny or allow.
> + * @r: Supplies a pointer to the rule that was matched, if possible.
> + * @enforce: Supplies the enforcement/permissive state at the point
> + * the enforcement decision was made.
> + */
Does it make sense to move @match_type into the ipe_eval_ctx struct?
> +void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
> + enum ipe_match match_type,
> + enum ipe_action_type act, const struct ipe_rule *const r)
> +{
> + struct inode *inode;
> + struct audit_buffer *ab;
> + const char *op = audit_op_names[ctx->op];
> +
> + if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit))
> + return;
> +
> + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
> + if (!ab)
> + return;
> +
> + if (ctx->file) {
> + audit_log_d_path(ab, "path=", &ctx->file->f_path);
> + inode = file_inode(ctx->file);
> + if (inode) {
> + audit_log_format(ab, " dev=");
> + audit_log_untrustedstring(ab, inode->i_sb->s_id);
> + audit_log_format(ab, " ino=%lu ", inode->i_ino);
> + }
> + }
> +
> + if (match_type == IPE_MATCH_RULE)
> + audit_rule(ab, r);
> + else if (match_type == IPE_MATCH_TABLE)
> + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op,
> + ACTSTR(act));
> + else
> + audit_log_format(ab, "rule=\"DEFAULT action=%s\"",
> + ACTSTR(act));
> +
> + audit_log_end(ab);
> +}
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> IPE's interpretation of the what the user trusts is accomplished through
> its policy. IPE's design is to not provide support for a single trust
> provider, but to support multiple providers to enable the end-user to
> choose the best one to seek their needs.
>
> This requires the policy to be rather flexible and modular so that
> integrity providers, like fs-verity, dm-verity, dm-integrity, or
> some other system, can plug into the policy with minimal code changes.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> + Split evaluation loop, access control hooks,
> and evaluation loop from policy parser and userspace
> interface to pass mailing list character limit
>
> v3:
> + Move policy load and activation audit event to 03/12
> + Fix a potential panic when a policy failed to load.
> + use pr_warn for a failure to parse instead of an
> audit record
> + Remove comments from headers
> + Add lockdep assertions to ipe_update_active_policy and
> ipe_activate_policy
> + Fix up warnings with checkpatch --strict
> + Use file_ns_capable for CAP_MAC_ADMIN for securityfs
> nodes.
> + Use memdup_user instead of kzalloc+simple_write_to_buffer.
> + Remove strict_parse command line parameter, as it is added
> by the sysctl command line.
> + Prefix extern variables with ipe_
>
> v4:
> + Remove securityfs to reverse-dependency
> + Add SHA1 reverse dependency.
> + Add versioning scheme for IPE properties, and associated
> interface to query the versioning scheme.
> + Cause a parser to always return an error on unknown syntax.
> + Remove strict_parse option
> + Change active_policy interface from sysctl, to securityfs,
> and change scheme.
>
> v5:
> + Cause an error if a default action is not defined for each
> operation.
> + Minor function renames
>
> v6:
> + No changes
>
> v7:
> + Further split parser and userspace interface into two
> separate commits, for easier review.
> + Refactor policy parser to make code cleaner via introducing a
> more modular design, for easier extension of policy, and
> easier review.
>
> v8:
> + remove unnecessary pr_info emission on parser loading
> + add explicit newline to the pr_err emitted when a parser
> fails to load.
>
> v9:
> + switch to match table to parse policy
> + remove quote syntax and KERNEL_READ operation
>
> v10:
> + Fix memory leaks in parser
> + Fix typos and change code styles
>
> v11:
> + Fix code style issues
> ---
> security/ipe/Makefile | 2 +
> security/ipe/policy.c | 101 ++++++++
> security/ipe/policy.h | 83 ++++++
> security/ipe/policy_parser.c | 487 +++++++++++++++++++++++++++++++++++
> security/ipe/policy_parser.h | 11 +
> 5 files changed, 684 insertions(+)
> create mode 100644 security/ipe/policy.c
> create mode 100644 security/ipe/policy.h
> create mode 100644 security/ipe/policy_parser.c
> create mode 100644 security/ipe/policy_parser.h
...
> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
> new file mode 100644
> index 000000000000..3a529c7950a1
> --- /dev/null
> +++ b/security/ipe/policy.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
...
> +static int set_pkcs7_data(void *ctx, const void *data, size_t len,
> + size_t asn1hdrlen)
> +{
> + struct ipe_policy *p = ctx;
> +
> + p->text = (const char *)data;
> + p->textlen = len;
> +
> + return 0;
> +}
The @asn1hdrlen parameter isn't used in this function, at least at this
point in the patchset, so you really should remove it. If it is needed
later in the patchset you can always update the function.
> diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
> new file mode 100644
> index 000000000000..c09458bd348d
> --- /dev/null
> +++ b/security/ipe/policy_parser.c
> @@ -0,0 +1,487 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
...
> +/**
> + * remove_trailing_spaces - Truncate all trailing spaces in a string.
> + *
> + * @line: Supplies a poilcy line string for preprocessing.
> + *
> + * Return: The length of truncated string.
> + */
> +static size_t remove_trailing_spaces(char *line)
> +{
> + size_t i = 0;
> +
> + for (i = strlen(line); i > 0 && (line[i - 1] == ' ' || line[i - 1] == '\t'); --i)
> + ;
Maybe I've asked this before, I can't remember: could you use the
isspace() macro here instead of explicitly checking for ' ' and '\t'?
i = strlen(line);
while (i > 0 && isspace(line[i - 1]))
i--;
line[i] = '\0';
> + line[i] = '\0';
> +
> + return i;
> +}
> +
> +/**
> + * parse_version - Parse policy version.
> + * @ver: Supplies a version string to be parsed.
> + * @p: Supplies the partial parsed policy.
> + *
> + * Return:
> + * * 0 - OK
> + * * !0 - Standard errno
> + */
> +static int parse_version(char *ver, struct ipe_parsed_policy *p)
> +{
> + int rc = 0;
> + size_t sep_count = 0;
> + char *token;
> + u16 *const cv[] = { &p->version.major, &p->version.minor, &p->version.rev };
> +
> + while ((token = strsep(&ver, ".")) != NULL) {
> + /* prevent overflow */
> + if (sep_count >= ARRAY_SIZE(cv))
> + return -EBADMSG;
> +
> + rc = kstrtou16(token, 10, cv[sep_count]);
> + if (rc)
> + return rc;
> +
> + ++sep_count;
> + }
> +
> + /* prevent underflow */
> + if (sep_count != ARRAY_SIZE(cv))
> + rc = -EBADMSG;
You could always just 'return -EBADMSG' here and 'return 0' below to
simplify things a little.
> + return rc;
> +}
> +
> +enum header_opt {
> + IPE_HEADER_POLICY_NAME = 0,
> + IPE_HEADER_POLICY_VERSION,
> + __IPE_HEADER_MAX
> +};
> +
> +static const match_table_t header_tokens = {
> + {IPE_HEADER_POLICY_NAME, "policy_name=%s"},
> + {IPE_HEADER_POLICY_VERSION, "policy_version=%s"},
> + {__IPE_HEADER_MAX, NULL}
> +};
> +
> +/**
> + * parse_header - Parse policy header information.
> + * @line: Supplies header line to be parsed.
> + * @p: Supplies the partial parsed policy.
> + *
> + * Return:
> + * * 0 - OK
> + * * !0 - Standard errno
> + */
> +static int parse_header(char *line, struct ipe_parsed_policy *p)
> +{
> + int rc = 0;
> + char *t, *ver = NULL;
> + substring_t args[MAX_OPT_ARGS];
> + size_t idx = 0;
> +
> + while ((t = strsep(&line, IPE_POLICY_DELIM)) != NULL) {
> + int token;
> +
> + if (*t == '\0')
> + continue;
> + if (idx >= __IPE_HEADER_MAX) {
> + rc = -EBADMSG;
> + goto out;
> + }
> +
> + token = match_token(t, header_tokens, args);
> + if (token != idx) {
> + rc = -EBADMSG;
> + goto out;
> + }
> +
> + switch (token) {
> + case IPE_HEADER_POLICY_NAME:
> + p->name = match_strdup(&args[0]);
> + if (!p->name)
> + rc = -ENOMEM;
> + break;
> + case IPE_HEADER_POLICY_VERSION:
> + ver = match_strdup(&args[0]);
> + if (!ver) {
> + rc = -ENOMEM;
> + break;
> + }
> + rc = parse_version(ver, p);
> + break;
> + default:
> + rc = -EBADMSG;
> + }
> + if (rc)
> + goto out;
> + ++idx;
> + }
> +
> + if (idx != __IPE_HEADER_MAX) {
> + rc = -EBADMSG;
> + goto out;
You probably don't need to 'goto out' here.
> + }
> +
> +out:
> + kfree(ver);
> + return rc;
> +}
...
> +/**
> + * parse_rule - parse a policy rule line.
> + * @line: Supplies rule line to be parsed.
> + * @p: Supplies the partial parsed policy.
> + *
> + * Return:
> + * * !IS_ERR - OK
> + * * -ENOMEM - Out of memory
> + * * -EBADMSG - Policy syntax error
> + */
> +static int parse_rule(char *line, struct ipe_parsed_policy *p)
> +{
> + int rc = 0;
> + bool first_token = true, is_default_rule = false;
> + bool op_parsed = false;
> + enum ipe_op_type op = IPE_OP_INVALID;
> + enum ipe_action_type action = IPE_ACTION_INVALID;
> + struct ipe_rule *r = NULL;
> + char *t;
> +
> + r = kzalloc(sizeof(*r), GFP_KERNEL);
> + if (!r)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&r->next);
> + INIT_LIST_HEAD(&r->props);
> +
> + while (t = strsep(&line, IPE_POLICY_DELIM), line) {
> + if (*t == '\0')
> + continue;
> + if (first_token && token_default(t)) {
> + is_default_rule = true;
> + } else {
> + if (!op_parsed) {
> + op = parse_operation(t);
> + if (op == IPE_OP_INVALID)
> + rc = -EBADMSG;
> + else
> + op_parsed = true;
> + } else {
> + rc = parse_property(t, r);
> + }
> + }
> +
> + if (rc)
> + goto err;
> + first_token = false;
> + }
> +
> + action = parse_action(t);
> + if (action == IPE_ACTION_INVALID) {
> + rc = -EBADMSG;
> + goto err;
> + }
> +
> + if (is_default_rule) {
> + if (!list_empty(&r->props)) {
> + rc = -EBADMSG;
> + } else if (op == IPE_OP_INVALID) {
> + if (p->global_default_action != IPE_ACTION_INVALID)
> + rc = -EBADMSG;
> + else
> + p->global_default_action = action;
> + } else {
> + if (p->rules[op].default_action != IPE_ACTION_INVALID)
> + rc = -EBADMSG;
> + else
> + p->rules[op].default_action = action;
> + }
> + } else if (op != IPE_OP_INVALID && action != IPE_ACTION_INVALID) {
> + r->op = op;
> + r->action = action;
> + } else {
> + rc = -EBADMSG;
> + }
I might be missing something important in the policy syntac, but could
this function, and perhaps the ipe_parsed_policy struct, be simplified
if the default action was an explicit rule?
"op=DEFAULT action=ALLOW"
> + if (rc)
> + goto err;
> + if (!is_default_rule)
> + list_add_tail(&r->next, &p->rules[op].rules);
> + else
> + free_rule(r);
> +
> + return rc;
> +err:
> + free_rule(r);
> + return rc;
> +}
> +
> +/**
> + * free_parsed_policy - free a parsed policy structure.
> + * @p: Supplies the parsed policy.
> + */
> +void free_parsed_policy(struct ipe_parsed_policy *p)
> +{
> + size_t i = 0;
> + struct ipe_rule *pp, *t;
> +
> + if (IS_ERR_OR_NULL(p))
> + return;
> +
> + for (i = 0; i < ARRAY_SIZE(p->rules); ++i)
> + list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) {
> + list_del(&pp->next);
> + free_rule(pp);
> + }
> +
> + kfree(p->name);
> + kfree(p);
> +}
> +
> +/**
> + * validate_policy - validate a parsed policy.
> + * @p: Supplies the fully parsed policy.
> + *
> + * Given a policy structure that was just parsed, validate that all
> + * necessary fields are present, initialized correctly.
> + *
> + * A parsed policy can be in an invalid state for use (a default was
> + * undefined) by just parsing the policy.
> + *
> + * Return:
> + * * 0 - OK
> + * * -EBADMSG - Policy is invalid
> + */
> +static int validate_policy(const struct ipe_parsed_policy *p)
> +{
> + size_t i = 0;
> +
> + if (p->global_default_action != IPE_ACTION_INVALID)
> + return 0;
Should the if conditional above be "==" and not "!="?
> + for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
> + if (p->rules[i].default_action == IPE_ACTION_INVALID)
> + return -EBADMSG;
> + }
> +
> + return 0;
> +}
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> IPE, like SELinux, supports a permissive mode. This mode allows policy
> authors to test and evaluate IPE policy without it effecting their
> programs. When the mode is changed, a 1404 AUDIT_MAC_STATUS
> be reported.
>
> This patch adds the following audit records:
>
> audit: MAC_STATUS enforcing=0 old_enforcing=1 auid=4294967295
> ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
> audit: MAC_STATUS enforcing=1 old_enforcing=0 auid=4294967295
> ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
>
> The audit record only emit when the value from the user input is
> different from the current enforce value.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> + Split evaluation loop, access control hooks,
> and evaluation loop from policy parser and userspace
> interface to pass mailing list character limit
>
> v3:
> + Move ipe_load_properties to patch 04.
> + Remove useless 0-initializations
> + Prefix extern variables with ipe_
> + Remove kernel module parameters, as these are
> exposed through sysctls.
> + Add more prose to the IPE base config option
> help text.
> + Use GFP_KERNEL for audit_log_start.
> + Remove unnecessary caching system.
> + Remove comments from headers
> + Use rcu_access_pointer for rcu-pointer null check
> + Remove usage of reqprot; use prot only.
> + Move policy load and activation audit event to 03/12
>
> v4:
> + Remove sysctls in favor of securityfs nodes
> + Re-add kernel module parameters, as these are now
> exposed through securityfs.
> + Refactor property audit loop to a separate function.
>
> v5:
> + fix minor grammatical errors
> + do not group rule by curly-brace in audit record,
> reconstruct the exact rule.
>
> v6:
> + No changes
>
> v7:
> + Further split lsm creation into a separate commit from the
> evaluation loop and audit system, for easier review.
> + Propagating changes to support the new ipe_context structure in the
> evaluation loop.
> + Split out permissive functionality into a separate patch for easier
> review.
> + Remove permissive switch compile-time configuration option - this
> is trivial to add later.
>
> v8:
> + Remove "IPE" prefix from permissive audit record
> + align fields to the linux-audit field dictionary. This causes the
> following fields to change:
> enforce -> permissive
>
> + Remove duplicated information correlated with syscall record, that
> will always be present in the audit event.
> + Change audit types:
> + AUDIT_TRUST_STATUS -> AUDIT_MAC_STATUS
> + There is no significant difference in meaning between
> these types.
>
> v9:
> + Clean up ipe_context related code
>
> v10:
> + Change audit format to comform with the existing format selinux is
> using
> + Remove the audit record emission during init to align with selinux,
> which does not perform this action.
>
> v11:
> + Remove redundant code
> ---
> security/ipe/audit.c | 22 ++++++++++++++
> security/ipe/audit.h | 1 +
> security/ipe/eval.c | 14 +++++++--
> security/ipe/eval.h | 1 +
> security/ipe/fs.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 104 insertions(+), 2 deletions(-)
...
> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> index 499b6b3338f2..78c54ff1fdd3 100644
> --- a/security/ipe/eval.c
> +++ b/security/ipe/eval.c
> @@ -167,9 +172,12 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
> ipe_audit_match(ctx, match_type, action, rule);
>
> if (action == IPE_ACTION_DENY)
> - return -EACCES;
> + rc = -EACCES;
> +
> + if (!enforcing)
> + rc = 0;
Why the local @enforcing variable? Why not:
if (!READ_ONCE(enforce))
rc = 0;
> - return 0;
> + return rc;
> }
>
> /**
> @@ -198,3 +206,5 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
>
> module_param(success_audit, bool, 0400);
> MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
> +module_param(enforce, bool, 0400);
> +MODULE_PARM_DESC(enforce, "Start IPE in enforce or permissive mode");
"enforcing"
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> This patch adds a target finalize hook.
>
> The hook is triggered just before activating an inactive table of a
> mapped device. If it returns an error the __bind get cancelled.
>
> The dm-verity target will use this hook to attach the dm-verity's
> roothash metadata to the block_device struct of the mapped device.
>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v1-v10:
> + Not present
> ---
> drivers/md/dm.c | 12 ++++++++++++
> include/linux/device-mapper.h | 7 +++++++
> 2 files changed, 19 insertions(+)
We need an ACK and confirmation from Alasdair and/or Mike that this
is the right approach.
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 64a1f306c96c..3be9cc35306d 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2239,6 +2239,18 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> goto out;
> }
>
> + for (unsigned int i = 0; i < t->num_targets; i++) {
> + struct dm_target *ti = dm_table_get_target(t, i);
> +
> + if (ti->type->finalize) {
> + ret = ti->type->finalize(ti);
> + if (ret) {
> + old_map = ERR_PTR(ret);
> + goto out;
> + }
> + }
> + }
> +
> old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
> rcu_assign_pointer(md->map, (void *)t);
> md->immutable_target_type = dm_table_get_immutable_target_type(t);
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 69d0435c7ebb..4040e84a8ec7 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -160,6 +160,12 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff,
> */
> typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff,
> void *addr, size_t bytes, struct iov_iter *i);
> +/*
> + * Returns:
> + * < 0 : error
> + * = 0 : success
> + */
> +typedef int (*dm_finalize_fn) (struct dm_target *target);
>
> void dm_error(const char *message);
>
> @@ -209,6 +215,7 @@ struct target_type {
> dm_dax_direct_access_fn direct_access;
> dm_dax_zero_page_range_fn dax_zero_page_range;
> dm_dax_recovery_write_fn dax_recovery_write;
> + dm_finalize_fn finalize;
>
> /* For internal device-mapper use. */
> struct list_head list;
> --
> 2.25.1
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> The device-mapper has a flag to mark targets as singleton, which is a
> required flag for immutable targets. Without this flag, multiple
> dm-verity targets can be added to a mapped device, which has no
> practical use cases and will let dm_table_get_immutable_target return
> NULL. This patch adds the missing flag, restricting only one
> dm-verity target per mapped device.
>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v1-v10:
> + Not present
> ---
> drivers/md/dm-verity-target.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
This seems reasonable to me and matches with other users of
DM_TARGET_IMMUTABLE.
Alasdair, Mike, can we get an ACK on this?
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index 26adcfea0302..80673b66c194 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -1503,7 +1503,7 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
>
> static struct target_type verity_target = {
> .name = "verity",
> - .features = DM_TARGET_IMMUTABLE,
> + .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> .version = {1, 9, 0},
> .module = THIS_MODULE,
> .ctr = verity_ctr,
> --
> 2.25.1
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> Allows author of IPE policy to indicate trust for a singular dm-verity
> volume, identified by roothash, through "dmverity_roothash" and all
> signed dm-verity volumes, through "dmverity_signature".
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> + No Changes
>
> v3:
> + No changes
>
> v4:
> + No changes
>
> v5:
> + No changes
>
> v6:
> + Fix an improper cleanup that can result in
> a leak
>
> v7:
> + Squash patch 08/12, 10/12 to [11/16]
>
> v8:
> + Undo squash of 08/12, 10/12 - separating drivers/md/ from security/
> & block/
> + Use common-audit function for dmverity_signature.
> + Change implementation for storing the dm-verity digest to use the
> newly introduced dm_verity_digest structure introduced in patch
> 14/20.
>
> v9:
> + Adapt to the new parser
>
> v10:
> + Select the Kconfig when all dependencies are enabled
>
> v11:
> + No changes
> ---
> security/ipe/Kconfig | 18 +++++
> security/ipe/Makefile | 1 +
> security/ipe/audit.c | 31 +++++++-
> security/ipe/digest.c | 142 +++++++++++++++++++++++++++++++++++
> security/ipe/digest.h | 26 +++++++
> security/ipe/eval.c | 101 ++++++++++++++++++++++++-
> security/ipe/eval.h | 13 ++++
> security/ipe/hooks.c | 51 +++++++++++++
> security/ipe/hooks.h | 8 ++
> security/ipe/ipe.c | 15 ++++
> security/ipe/ipe.h | 4 +
> security/ipe/policy.h | 3 +
> security/ipe/policy_parser.c | 24 +++++-
> 13 files changed, 433 insertions(+), 4 deletions(-)
> create mode 100644 security/ipe/digest.c
> create mode 100644 security/ipe/digest.h
...
> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
> index 0dd5f10c318f..b5c58655ac74 100644
> --- a/security/ipe/audit.c
> +++ b/security/ipe/audit.c
> @@ -13,6 +13,7 @@
> #include "hooks.h"
> #include "policy.h"
> #include "audit.h"
> +#include "digest.h"
>
> #define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
>
> @@ -40,8 +41,29 @@ static const char *const audit_op_names[__IPE_OP_MAX] = {
> static const char *const audit_prop_names[__IPE_PROP_MAX] = {
> "boot_verified=FALSE",
> "boot_verified=TRUE",
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> + "dmverity_roothash=",
> + "dmverity_signature=FALSE",
> + "dmverity_signature=TRUE",
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> };
>
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +/**
> + * audit_dmv_roothash - audit a roothash of a dmverity volume.
> + * @ab: Supplies a pointer to the audit_buffer to append to.
> + * @r: Supplies a pointer to the digest structure.
> + */
> +static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
> +{
> + ipe_digest_audit(ab, rh);
> +}
> +#else
> +static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
> +{
> +}
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
Since the "dmverity_roothash=" field name is going to be written to
the audit record regardless of CONFIG_IPE_PROP_DM_VERITY we should
ensure that it has a value of "?" instead of nothing. To fix that
I would suggest something like this:
#else
static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
{
audit_log_format(ab, "?");
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
> /**
> * audit_rule - audit an IPE policy rule approximation.
> * @ab: Supplies a pointer to the audit_buffer to append to.
> @@ -53,8 +75,13 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
>
> audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
>
> - list_for_each_entry(ptr, &r->props, next)
> - audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
> + list_for_each_entry(ptr, &r->props, next) {
> + audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
> + if (ptr->type == IPE_PROP_DMV_ROOTHASH)
> + audit_dmv_roothash(ab, ptr->value);
If you wanted to avoid the roothash change above, you could change the
code here so it didn't always write "dmverity_roothash=" into the audit
record.
> + audit_log_format(ab, " ");
> + }
>
> audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
> }
> diff --git a/security/ipe/digest.c b/security/ipe/digest.c
> new file mode 100644
> index 000000000000..7a42ca71880c
> --- /dev/null
> +++ b/security/ipe/digest.c
> @@ -0,0 +1,142 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#include "digest.h"
> +
> +/**
> + * ipe_digest_parse - parse a digest in IPE's policy.
> + * @valstr: Supplies the string parsed from the policy.
> + * @value: Supplies a pointer to be populated with the result.
> + *
> + * Digests in IPE are defined in a standard way:
> + * <alg_name>:<hex>
> + *
> + * Use this function to create a property to parse the digest
> + * consistently. The parsed digest will be saved in @value in IPE's
> + * policy.
> + *
> + * Return:
> + * * 0 - OK
> + * * !0 - Error
> + */
> +int ipe_digest_parse(const char *valstr, void **value)
Why is @value void? You should make it a digest_info type or simply
skip the second parameter and return a digest_info pointer.
> +{
> + char *sep, *raw_digest;
> + size_t raw_digest_len;
> + int rc = 0;
> + u8 *digest = NULL;
> + struct digest_info *info = NULL;
> +
> + info = kzalloc(sizeof(*info), GFP_KERNEL);
> + if (!info)
> + return -ENOMEM;
> +
> + sep = strchr(valstr, ':');
> + if (!sep) {
> + rc = -EBADMSG;
> + goto err;
> + }
> +
> + info->alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
> + if (!info->alg) {
> + rc = -ENOMEM;
> + goto err;
> + }
> +
> + raw_digest = sep + 1;
> + raw_digest_len = strlen(raw_digest);
> + info->raw_digest = kstrndup(raw_digest, raw_digest_len, GFP_KERNEL);
Since you're running a strlen() over @raw_digest, you might as well
just use kstrdup() instead of kstrndup().
> + if (!info->raw_digest) {
> + rc = -ENOMEM;
> + goto err_free_alg;
> + }
> +
> + info->digest_len = (raw_digest_len + 1) / 2;
> + digest = kzalloc(info->digest_len, GFP_KERNEL);
> + if (!digest) {
> + rc = -ENOMEM;
> + goto err_free_raw;
> + }
> +
> + rc = hex2bin(digest, raw_digest, info->digest_len);
> + if (rc < 0) {
> + rc = -EINVAL;
> + goto err_free_raw;
> + }
> +
> + info->digest = digest;
> + *value = info;
> + return 0;
> +
> +err_free_raw:
> + kfree(info->raw_digest);
> +err_free_alg:
> + kfree(info->alg);
> +err:
> + kfree(digest);
> + kfree(info);
> + return rc;
> +}
> +
> +/**
> + * ipe_digest_eval - evaluate an IPE digest against another digest.
> + * @expect: Supplies the policy-provided digest value.
> + * @digest: Supplies the digest to compare against the policy digest value.
> + * @digest_len: The length of @digest.
> + * @alg: Supplies the name of the algorithm used to calculated @digest.
> + *
> + * Return:
> + * * true - digests match
> + * * false - digests do not match
> + */
> +bool ipe_digest_eval(const void *expect, const u8 *digest, size_t digest_len,
> + const char *alg)
Similar to the above, why not make the @expect parameter a digest_info
type? Also, why not pass a second digest_info parameter instead of
a separate @digest, @digest_len, and @alg?
> +{
> + const struct digest_info *info = (struct digest_info *)expect;
> +
> + return (digest_len == info->digest_len) && !strcmp(alg, info->alg) &&
> + (!memcmp(info->digest, digest, info->digest_len));
> +}
> +
> +/**
> + * ipe_digest_free - free an IPE digest.
> + * @value: Supplies a pointer the policy-provided digest value to free.
> + */
> +void ipe_digest_free(void **value)
Another digest_info parameter/type issue.
> +{
> + struct digest_info *info = (struct digest_info *)(*value);
> +
> + if (IS_ERR_OR_NULL(info))
> + return;
> +
> + kfree(info->alg);
> + kfree(info->raw_digest);
> + kfree(info->digest);
> + kfree(info);
> +}
> +
> +/**
> + * ipe_digest_audit - audit a digest that was sourced from IPE's policy.
> + * @ab: Supplies the audit_buffer to append the formatted result.
> + * @val: Supplies a pointer to source the audit record from.
> + *
> + * Digests in IPE are defined in a standard way:
> + * <alg_name>:<hex>
> + *
> + * Use this function to create a property to audit the digest
> + * consistently.
> + *
> + * Return:
> + * 0 - OK
> + * !0 - Error
> + */
> +void ipe_digest_audit(struct audit_buffer *ab, const void *val)
Another digest_info parameter/type issue.
> +{
> + const struct digest_info *info = (struct digest_info *)val;
> +
> + audit_log_untrustedstring(ab, info->alg);
> + audit_log_format(ab, ":");
> + audit_log_untrustedstring(ab, info->raw_digest);
> +}
...
> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> index 78c54ff1fdd3..82ad48d7aa3d 100644
> --- a/security/ipe/eval.c
> +++ b/security/ipe/eval.c
> @@ -69,15 +88,89 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
> const struct file *file,
> enum ipe_op_type op)
> {
> + struct inode *ino = NULL;
> +
> if (op == IPE_OP_EXEC && file)
> pin_sb(FILE_SUPERBLOCK(file));
>
> ctx->file = file;
> ctx->op = op;
>
> - if (file)
> + if (file) {
> ctx->from_init_sb = from_pinned(FILE_SUPERBLOCK(file));
> + ino = d_real_inode(file->f_path.dentry);
> + build_ipe_bdev_ctx(ctx, ino);
You don't need @ino.
build_ipe_bdev_ctx(ctx, d_real_inode(file->f_path.dentry));
> + }
> +}
> +
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +/**
> + * evaluate_dmv_roothash - Evaluate @ctx against a dmv roothash property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_dmv_roothash(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return !!ctx->ipe_bdev &&
> + ipe_digest_eval(p->value,
> + ctx->ipe_bdev->digest,
> + ctx->ipe_bdev->digest_len,
> + ctx->ipe_bdev->digest_algo);
Building on my comments above in ipe_digest_eval(), if you convert it
to use digest_info structs this is simplified:
ipe_digest_eval(p->vlaue, ctx->ipe_bdev)
> +}
> +
> +/**
> + * evaluate_dmv_sig_false: Analyze @ctx against a dmv sig false property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_dmv_sig_false(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return !ctx->ipe_bdev || (!ctx->ipe_bdev->dm_verity_signed);
> +}
> +
> +/**
> + * evaluate_dmv_sig_true: Analyze @ctx against a dmv sig true property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return ctx->ipe_bdev && (!!ctx->ipe_bdev->dm_verity_signed);
> +}
Do you need both evaluate_dmv_sig_true() and evaluate_dmv_sig_false()?
If yes, you should make one call the other and return the inverse to
help ensure there are no oddities.
> diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
> index e9386762a597..8b8031e66f36 100644
> --- a/security/ipe/hooks.c
> +++ b/security/ipe/hooks.c
> @@ -193,3 +196,51 @@ void ipe_sb_free_security(struct super_block *mnt_sb)
> {
> ipe_invalidate_pinned_sb(mnt_sb);
> }
> +
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +/**
> + * ipe_bdev_free_security - free IPE's LSM blob of block_devices.
> + * @bdev: Supplies a pointer to a block_device that contains the structure
> + * to free.
> + */
> +void ipe_bdev_free_security(struct block_device *bdev)
> +{
> + struct ipe_bdev *blob = ipe_bdev(bdev);
> +
> + kfree(blob->digest);
> + kfree(blob->digest_algo);
> +}
> +
> +/**
> + * ipe_bdev_setsecurity - save data from a bdev to IPE's LSM blob.
> + * @bdev: Supplies a pointer to a block_device that contains the LSM blob.
> + * @key: Supplies the string key that uniquely identifies the value.
> + * @value: Supplies the value to store.
> + * @len: The length of @value.
> + */
> +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
> + const void *value, size_t len)
> +{
> + struct ipe_bdev *blob = ipe_bdev(bdev);
> +
> + if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) {
> + const struct dm_verity_digest *digest = value;
> +
> + blob->digest = kmemdup(digest->digest, digest->digest_len, GFP_KERNEL);
> + if (!blob->digest)
> + return -ENOMEM;
> +
> + blob->digest_algo = kstrdup_const(digest->algo, GFP_KERNEL);
> + if (!blob->digest_algo)
> + return -ENOMEM;
You need to cleanup @blob on error so you don't leak ipe_bdev::digest.
> + blob->digest_len = digest->digest_len;
> + return 0;
> + } else if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) {
> + blob->dm_verity_signed = true;
> + return 0;
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> dm-verity provides a strong guarantee of a block device's integrity. As
> a generic way to check the integrity of a block device, it provides
> those integrity guarantees to its higher layers, including the filesystem
> level.
>
> An LSM that control access to a resource on the system based on the
> available integrity claims can use this transitive property of
> dm-verity, by querying the underlying block_device of a particular
> file.
>
> The digest and signature information need to be stored in the block
> device to fulfill the next requirement of authorization via LSM policy.
> This will enable the LSM to perform revocation of devices that are still
> mounted, prohibiting execution of files that are no longer authorized
> by the LSM in question.
>
> This patch added two security hook calls in dm-verity to save the
> dm-verity roothash and the roothash signature to the block device's
> LSM blobs.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> + No Changes
>
> v3:
> + No changes
>
> v4:
> + No changes
>
> v5:
> + No changes
>
> v6:
> + Fix an improper cleanup that can result in
> a leak
>
> v7:
> + Squash patch 08/12, 10/12 to [11/16]
> + Use part0 for block_device, to retrieve the block_device, when
> calling security_bdev_setsecurity
>
> v8:
> + Undo squash of 08/12, 10/12 - separating drivers/md/ from
> security/ & block/
> + Use common-audit function for dmverity_signature.
> + Change implementation for storing the dm-verity digest to use the
> newly introduced dm_verity_digest structure introduced in patch
> 14/20.
> + Create new structure, dm_verity_digest, containing digest algorithm,
> size, and digest itself to pass to the LSM layer. V7 was missing the
> algorithm.
> + Create an associated public header containing this new structure and
> the key values for the LSM hook, specific to dm-verity.
> + Additional information added to commit, discussing the layering of
> the changes and how the information passed will be used.
>
> v9:
> + No changes
>
> v10:
> + No changes
>
> v11:
> + Add an optional field to save signature
> + Move the security hook call to the new finalize hook
> ---
> drivers/md/dm-verity-target.c | 71 +++++++++++++++++++++++++++++++++++
> drivers/md/dm-verity.h | 6 +++
> include/linux/dm-verity.h | 19 ++++++++++
> 3 files changed, 96 insertions(+)
> create mode 100644 include/linux/dm-verity.h
We need an ACK from Alasdair and/or Mike on this too.
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index 80673b66c194..db58b53649e3 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -13,6 +13,7 @@
> * access behavior.
> */
>
> +#include "dm-core.h"
> #include "dm-verity.h"
> #include "dm-verity-fec.h"
> #include "dm-verity-verify-sig.h"
> @@ -22,6 +23,9 @@
> #include <linux/scatterlist.h>
> #include <linux/string.h>
> #include <linux/jump_label.h>
> +#include <linux/security.h>
> +#include <linux/dm-verity.h>
> +#include <crypto/hash_info.h>
>
> #define DM_MSG_PREFIX "verity"
>
> @@ -952,6 +956,17 @@ static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
> blk_limits_io_min(limits, limits->logical_block_size);
> }
>
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +static void verity_free_sig(struct dm_verity *v)
> +{
> + kfree(v->root_digest_sig);
> +}
> +#else
> +static inline void verity_free_sig(struct dm_verity *v)
> +{
> +}
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> +
> static void verity_dtr(struct dm_target *ti)
> {
> struct dm_verity *v = ti->private;
> @@ -966,6 +981,7 @@ static void verity_dtr(struct dm_target *ti)
> kfree(v->salt);
> kfree(v->root_digest);
> kfree(v->zero_digest);
> + verity_free_sig(v);
>
> if (v->tfm)
> crypto_free_ahash(v->tfm);
> @@ -1157,6 +1173,25 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
> return r;
> }
>
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +static int verity_init_sig(struct dm_verity *v, const void *sig,
> + size_t sig_size)
> +{
> + v->sig_size = sig_size;
> + v->root_digest_sig = kmalloc(v->sig_size, GFP_KERNEL);
> + if (!v->root_digest)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +#else
> +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> + size_t sig_size)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> +
> /*
> * Target parameters:
> * <version> The current format is version 1.
> @@ -1365,6 +1400,13 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> ti->error = "Root hash verification failed";
> goto bad;
> }
> +
> + r = verity_init_sig(v, verify_args.sig, verify_args.sig_size);
> + if (r < 0) {
> + ti->error = "Cannot allocate root digest signature";
> + goto bad;
> + }
> +
> v->hash_per_block_bits =
> __fls((1 << v->hash_dev_block_bits) / v->digest_size);
>
> @@ -1501,6 +1543,32 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
> return 0;
> }
>
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> +static int verity_finalize(struct dm_target *ti)
> +{
> + struct block_device *bdev;
> + struct dm_verity_digest root_digest;
> + struct dm_verity *v;
> + int r;
> +
> + v = ti->private;
> + bdev = dm_table_get_md(ti->table)->disk->part0;
> + root_digest.digest = v->root_digest;
> + root_digest.digest_len = v->digest_size;
> + root_digest.algo = v->alg_name;
> +
> + r = security_bdev_setsecurity(bdev, DM_VERITY_ROOTHASH_SEC_NAME, &root_digest,
> + sizeof(root_digest));
> + if (r)
> + return r;
> +
> + return security_bdev_setsecurity(bdev,
> + DM_VERITY_SIGNATURE_SEC_NAME,
> + v->root_digest_sig,
> + v->sig_size);
> +}
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> +
> static struct target_type verity_target = {
> .name = "verity",
> .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> @@ -1513,6 +1581,9 @@ static struct target_type verity_target = {
> .prepare_ioctl = verity_prepare_ioctl,
> .iterate_devices = verity_iterate_devices,
> .io_hints = verity_io_hints,
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> + .finalize = verity_finalize,
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> };
> module_dm(verity);
>
> diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
> index 2f555b420367..a093d4a54615 100644
> --- a/drivers/md/dm-verity.h
> +++ b/drivers/md/dm-verity.h
> @@ -42,6 +42,9 @@ struct dm_verity {
> u8 *root_digest; /* digest of the root block */
> u8 *salt; /* salt: its size is salt_size */
> u8 *zero_digest; /* digest for a zero block */
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> + u8 *root_digest_sig; /* digest signature of the root block */
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> unsigned int salt_size;
> sector_t data_start; /* data offset in 512-byte sectors */
> sector_t hash_start; /* hash start in blocks */
> @@ -55,6 +58,9 @@ struct dm_verity {
> bool hash_failed:1; /* set if hash of any block failed */
> bool use_tasklet:1; /* try to verify in tasklet before work-queue */
> unsigned int digest_size; /* digest size for the current hash algorithm */
> +#ifdef CONFIG_IPE_PROP_DM_VERITY
> + unsigned int sig_size; /* digest signature size */
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> unsigned int ahash_reqsize;/* the size of temporary space for crypto */
> enum verity_mode mode; /* mode for handling verification errors */
> unsigned int corrupted_errs;/* Number of errors for corrupted blocks */
> diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
> new file mode 100644
> index 000000000000..bb0413d55d72
> --- /dev/null
> +++ b/include/linux/dm-verity.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _LINUX_DM_VERITY_H
> +#define _LINUX_DM_VERITY_H
> +
> +#include <linux/types.h>
> +#include <crypto/hash_info.h>
> +#include <linux/device-mapper.h>
> +
> +struct dm_verity_digest {
> + const char *algo;
> + const u8 *digest;
> + size_t digest_len;
> +};
> +
> +#define DM_VERITY_SIGNATURE_SEC_NAME DM_NAME ".verity-signature"
> +#define DM_VERITY_ROOTHASH_SEC_NAME DM_NAME ".verity-roothash"
> +
> +#endif /* _LINUX_DM_VERITY_H */
> --
> 2.25.1
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> Enable IPE policy authors to indicate trust for a singular fsverity
> file, identified by the digest information, through "fsverity_digest"
> and all files using fsverity's builtin signatures via
> "fsverity_signature".
>
> This enables file-level integrity claims to be expressed in IPE,
> allowing individual files to be authorized, giving some flexibility
> for policy authors. Such file-level claims are important to be expressed
> for enforcing the integrity of packages, as well as address some of the
> scalability issues in a sole dm-verity based solution (# of loop back
> devices, etc).
>
> This solution cannot be done in userspace as the minimum threat that
> IPE should mitigate is an attacker downloads malicious payload with
> all required dependencies. These dependencies can lack the userspace
> check, bypassing the protection entirely. A similar attack succeeds if
> the userspace component is replaced with a version that does not
> perform the check. As a result, this can only be done in the common
> entry point - the kernel.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v1-v6:
> + Not present
>
> v7:
> Introduced
>
> v8:
> * Undo squash of 08/12, 10/12 - separating drivers/md/ from security/
> * Use common-audit function for fsverity_signature.
> + Change fsverity implementation to use fsverity_get_digest
> + prevent unnecessary copy of fs-verity signature data, instead
> just check for presence of signature data.
> + Remove free_inode_security hook, as the digest is now acquired
> at runtime instead of via LSM blob.
>
> v9:
> + Adapt to the new parser
>
> v10:
> + Update the fsverity get digest call
>
> v11:
> + No changes
> ---
> security/ipe/Kconfig | 13 +++++
> security/ipe/audit.c | 23 ++++++++
> security/ipe/eval.c | 110 +++++++++++++++++++++++++++++++++++
> security/ipe/eval.h | 10 ++++
> security/ipe/hooks.c | 30 ++++++++++
> security/ipe/hooks.h | 7 +++
> security/ipe/ipe.c | 13 +++++
> security/ipe/ipe.h | 3 +
> security/ipe/policy.h | 3 +
> security/ipe/policy_parser.c | 8 +++
> 10 files changed, 220 insertions(+)
...
> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
> index b5c58655ac74..e3a8552a76a4 100644
> --- a/security/ipe/audit.c
> +++ b/security/ipe/audit.c
> @@ -79,6 +100,8 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
> audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
> if (ptr->type == IPE_PROP_DMV_ROOTHASH)
> audit_dmv_roothash(ab, ptr->value);
> + if (ptr->type == IPE_PROP_FSV_DIGEST)
> + audit_fsv_digest(ab, ptr->value);
My comments on audit_dmv_roothash() also apply here.
> audit_log_format(ab, " ");
> }
> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> index 82ad48d7aa3d..f0194b0ca2ff 100644
> --- a/security/ipe/eval.c
> +++ b/security/ipe/eval.c
> @@ -172,6 +191,91 @@ static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
> }
> #endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> +#ifdef CONFIG_IPE_PROP_FS_VERITY
> +/**
> + * evaluate_fsv_digest - Analyze @ctx against a fsv digest property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_fsv_digest(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + enum hash_algo alg;
> + u8 digest[FS_VERITY_MAX_DIGEST_SIZE];
> +
> + if (!ctx->ino)
> + return false;
> + if (!fsverity_get_digest((struct inode *)ctx->ino,
> + digest,
> + NULL,
> + &alg))
> + return false;
> +
> + return ipe_digest_eval(p->value,
> + digest,
> + hash_digest_size[alg],
> + hash_algo_name[alg]);
> +}
> +
> +/**
> + * evaluate_fsv_sig_false - Analyze @ctx against a fsv sig false property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_fsv_sig_false(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return !ctx->ino ||
> + !IS_VERITY(ctx->ino) ||
> + !ctx->ipe_inode ||
> + !ctx->ipe_inode->fs_verity_signed;
> +}
> +
> +/**
> + * evaluate_fsv_sig_true - Analyze @ctx against a fsv sig true property.
> + * @ctx: Supplies a pointer to the context being evaluated.
> + * @p: Supplies a pointer to the property being evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_fsv_sig_true(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return ctx->ino &&
> + IS_VERITY(ctx->ino) &&
> + ctx->ipe_inode &&
> + ctx->ipe_inode->fs_verity_signed;
> +}
See my previous comments about the false/true functions.
> +#else
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> IPE is designed to provide system level trust guarantees, this usually
> implies that trust starts from bootup with a hardware root of trust,
> which validates the bootloader. After this, the bootloader verifies the
> kernel and the initramfs.
>
> As there's no currently supported integrity method for initramfs, and
> it's typically already verified by the bootloader, introduce a property
> that causes the first superblock to have an execution to be "pinned",
> which is typically initramfs.
>
> When the "pinned" device is unmounted, it will be "unpinned" and
> `boot_verified` property will always evaluate to false afterward.
>
> We use a pointer with a spin_lock to "pin" the device instead of rcu
> because rcu synchronization may sleep, which is not allowed when
> unmounting a device.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> +No Changes
>
> v3:
> + Remove useless caching system
> + Move ipe_load_properties to this match
> + Minor changes from checkpatch --strict warnings
>
> v4:
> + Remove comments from headers that was missed previously.
> + Grammatical corrections.
>
> v5:
> + No significant changes
>
> v6:
> + No changes
>
> v7:
> + Reword and refactor patch 04/12 to [09/16], based on changes in the underlying system.
> + Add common audit function for boolean values
> + Use common audit function as implementation.
>
> v8:
> + No changes
>
> v9:
> + No changes
>
> v10:
> + Replace struct file with struct super_block
>
> v11:
> + Fix code style issues
> ---
> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
> security/ipe/eval.h | 2 +
> security/ipe/hooks.c | 12 ++++++
> security/ipe/hooks.h | 2 +
> security/ipe/ipe.c | 1 +
> security/ipe/policy.h | 2 +
> security/ipe/policy_parser.c | 35 +++++++++++++++++-
> 7 files changed, 124 insertions(+), 2 deletions(-)
>
> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> index 8a8bcc5c7d7f..bdac4abc0ddb 100644
> --- a/security/ipe/eval.c
> +++ b/security/ipe/eval.c
> @@ -9,6 +9,7 @@
> #include <linux/file.h>
> #include <linux/sched.h>
> #include <linux/rcupdate.h>
> +#include <linux/spinlock.h>
>
> #include "ipe.h"
> #include "eval.h"
> @@ -16,6 +17,44 @@
>
> struct ipe_policy __rcu *ipe_active_policy;
>
> +static const struct super_block *pinned_sb;
> +static DEFINE_SPINLOCK(pin_lock);
> +#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
> +
> +/**
> + * pin_sb - Pin the underlying superblock of @f, marking it as trusted.
> + * @sb: Supplies a super_block structure to be pinned.
> + */
> +static void pin_sb(const struct super_block *sb)
> +{
> + if (!sb)
> + return;
> + spin_lock(&pin_lock);
> + if (!pinned_sb)
> + pinned_sb = sb;
> + spin_unlock(&pin_lock);
> +}
> +
> +/**
> + * from_pinned - Determine whether @sb is the pinned super_block.
> + * @sb: Supplies a super_block to check against the pinned super_block.
> + *
> + * Return:
> + * * true - @sb is the pinned super_block
> + * * false - @sb is not the pinned super_block
> + */
> +static bool from_pinned(const struct super_block *sb)
> +{
> + bool rv;
> +
> + if (!sb)
> + return false;
> + spin_lock(&pin_lock);
> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
> + spin_unlock(&pin_lock);
It's okay for an initial version, but I still think you need to get
away from this spinlock in from_pinned() as quickly as possible.
Maybe I'm wrong, but this looks like a major source of lock contention.
I understand the issue around RCU and the potential for matching on
a reused buffer/address, but if you modified IPE to have its own LSM
security blob in super_block::security you could mark the superblock
when it was mounted and do a lockless lookup here in from_pinned().
> + return rv;
> +}
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> Enables an IPE policy to be enforced from kernel start, enabling access
> control based on trust from kernel startup. This is accomplished by
> transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a
> c-string literal that is parsed at kernel startup as an unsigned policy.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v2:
> + No Changes
>
> v3:
> + No Changes
>
> v4:
> + No Changes
>
> v5:
> + No Changes
>
> v6:
> + No Changes
>
> v7:
> + Move from 01/11 to 14/16
> + Don't return errno directly.
> + Make output of script more user-friendly
> + Add escaping for tab and '?'
> + Mark argv pointer const
> + Invert return code check in the boot policy parsing code path.
>
> v8:
> + No significant changes.
>
> v9:
> + No changes
>
> v10:
> + Update the init part code for rcu changes in the eval loop patch
>
> v11:
> + Fix code style issues
> ---
> MAINTAINERS | 1 +
> scripts/Makefile | 1 +
> scripts/ipe/Makefile | 2 +
> scripts/ipe/polgen/.gitignore | 1 +
> scripts/ipe/polgen/Makefile | 6 ++
> scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
> security/ipe/.gitignore | 1 +
> security/ipe/Kconfig | 10 +++
> security/ipe/Makefile | 11 +++
> security/ipe/fs.c | 8 ++
> security/ipe/ipe.c | 12 +++
> 11 files changed, 198 insertions(+)
> create mode 100644 scripts/ipe/Makefile
> create mode 100644 scripts/ipe/polgen/.gitignore
> create mode 100644 scripts/ipe/polgen/Makefile
> create mode 100644 scripts/ipe/polgen/polgen.c
> create mode 100644 security/ipe/.gitignore
...
> diff --git a/scripts/ipe/polgen/polgen.c b/scripts/ipe/polgen/polgen.c
> new file mode 100644
> index 000000000000..40b6fe07f47b
> --- /dev/null
> +++ b/scripts/ipe/polgen/polgen.c
> @@ -0,0 +1,145 @@
...
> +static int write_boot_policy(const char *pathname, const char *buf, size_t size)
> +{
> + int rc = 0;
> + FILE *fd;
> + size_t i;
> +
> + fd = fopen(pathname, "w");
> + if (!fd) {
> + rc = errno;
> + goto err;
> + }
> +
> + fprintf(fd, "/* This file is automatically generated.");
> + fprintf(fd, " Do not edit. */\n");
> + fprintf(fd, "#include <linux/stddef.h>\n");
> + fprintf(fd, "\nextern const char *const ipe_boot_policy;\n\n");
> + fprintf(fd, "const char *const ipe_boot_policy =\n");
> +
> + if (!buf || size == 0) {
> + fprintf(fd, "\tNULL;\n");
> + fclose(fd);
> + return 0;
> + }
> +
> + fprintf(fd, "\t\"");
> +
> + for (i = 0; i < size; ++i) {
> + switch (buf[i]) {
> + case '"':
> + fprintf(fd, "\\\"");
> + break;
> + case '\'':
> + fprintf(fd, "'");
> + break;
The revision of IPE proposed in this patchset doesn't support parsing
single or double quotes, yes?
> + case '\n':
> + fprintf(fd, "\\n\"\n\t\"");
> + break;
> + case '\\':
> + fprintf(fd, "\\\\");
> + break;
> + case '\t':
> + fprintf(fd, "\\t");
> + break;
> + case '\?':
> + fprintf(fd, "\\?");
> + break;
Similar, are question marks supported by the parser?
> + default:
> + fprintf(fd, "%c", buf[i]);
> + }
> + }
> + fprintf(fd, "\";\n");
> + fclose(fd);
> +
> + return 0;
> +
> +err:
> + if (fd)
> + fclose(fd);
> + return rc;
> +}
...
> diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore
> new file mode 100644
> index 000000000000..eca22ad5ed22
> --- /dev/null
> +++ b/security/ipe/.gitignore
> @@ -0,0 +1 @@
> +boot-policy.c
> \ No newline at end of file
Add a newline please.
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> fsverity represents a mechanism to support both integrity and
> authenticity protection of a file, supporting both signed and unsigned
> digests.
>
> An LSM which controls access to a resource based on authenticity and
> integrity of said resource, can then use this data to make an informed
> decision on the authorization (provided by the LSM's policy) of said
> claim.
>
> This effectively allows the extension of a policy enforcement layer in
> LSM for fsverity, allowing for more granular control of how a
> particular authenticity claim can be used. For example, "all (built-in)
> signed fsverity files should be allowed to execute, but only these
> hashes are allowed to be loaded as kernel modules".
>
> This enforcement must be done in kernel space, as a userspace only
> solution would fail a simple litmus test: Download a self-contained
> malicious binary that never touches the userspace stack. This
> binary would still be able to execute.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v1-v6:
> + Not present
>
> v7:
> Introduced
>
> v8:
> + Split fs/verity/ changes and security/ changes into separate patches
> + Change signature of fsverity_create_info to accept non-const inode
> + Change signature of fsverity_verify_signature to accept non-const inode
> + Don't cast-away const from inode.
> + Digest functionality dropped in favor of:
> ("fs-verity: define a function to return the integrity protected
> file digest")
> + Reworded commit description and title to match changes.
> + Fix a bug wherein no LSM implements the particular fsverity @name
> (or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
>
> v9:
> + No changes
>
> v10:
> + Rename the signature blob key
> + Cleanup redundant code
> + Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
>
> v11:
> + No changes
> ---
> fs/verity/fsverity_private.h | 2 +-
> fs/verity/open.c | 26 +++++++++++++++++++++++++-
> include/linux/fsverity.h | 2 ++
> 3 files changed, 28 insertions(+), 2 deletions(-)
We need an ACK from some VFS folks on this.
> diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> index d071a6e32581..4a82716e852f 100644
> --- a/fs/verity/fsverity_private.h
> +++ b/fs/verity/fsverity_private.h
> @@ -108,7 +108,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
> unsigned int log_blocksize,
> const u8 *salt, size_t salt_size);
>
> -struct fsverity_info *fsverity_create_info(const struct inode *inode,
> +struct fsverity_info *fsverity_create_info(struct inode *inode,
> struct fsverity_descriptor *desc);
>
> void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
> diff --git a/fs/verity/open.c b/fs/verity/open.c
> index 6c31a871b84b..5b48e2c39086 100644
> --- a/fs/verity/open.c
> +++ b/fs/verity/open.c
> @@ -8,6 +8,7 @@
> #include "fsverity_private.h"
>
> #include <linux/mm.h>
> +#include <linux/security.h>
> #include <linux/slab.h>
>
> static struct kmem_cache *fsverity_info_cachep;
> @@ -172,12 +173,28 @@ static int compute_file_digest(const struct fsverity_hash_alg *hash_alg,
> return err;
> }
>
> +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> +static int fsverity_inode_setsecurity(struct inode *inode,
> + struct fsverity_descriptor *desc)
> +{
> + return security_inode_setsecurity(inode, FS_VERITY_INODE_SEC_NAME,
> + desc->signature,
> + le32_to_cpu(desc->sig_size), 0);
> +}
> +#else
> +static inline int fsverity_inode_setsecurity(struct inode *inode,
> + struct fsverity_descriptor *desc)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_IPE_PROP_FS_VERITY*/
> +
> /*
> * Create a new fsverity_info from the given fsverity_descriptor (with optional
> * appended builtin signature), and check the signature if present. The
> * fsverity_descriptor must have already undergone basic validation.
> */
> -struct fsverity_info *fsverity_create_info(const struct inode *inode,
> +struct fsverity_info *fsverity_create_info(struct inode *inode,
> struct fsverity_descriptor *desc)
> {
> struct fsverity_info *vi;
> @@ -242,6 +259,13 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
> spin_lock_init(&vi->hash_page_init_lock);
> }
>
> + err = fsverity_inode_setsecurity(inode, desc);
> + if (err == -EOPNOTSUPP)
> + err = 0;
> +
> + if (err)
> + goto fail;
> +
> return vi;
>
> fail:
> diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
> index 1eb7eae580be..9666721baf15 100644
> --- a/include/linux/fsverity.h
> +++ b/include/linux/fsverity.h
> @@ -319,4 +319,6 @@ static inline int fsverity_prepare_setattr(struct dentry *dentry,
> return 0;
> }
>
> +#define FS_VERITY_INODE_SEC_NAME "fsverity.builtin-sig"
> +
> #endif /* _LINUX_FSVERITY_H */
> --
> 2.25.1
--
paul-moore.com
On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>
> Add various happy/unhappy unit tests for both IPE's parser.
I'm going to suggest: "... for IPE's policy parser."
Also, aside from the policy parser tests, are there any other IPE
functional tests? We do have a testing guideline for new LSM
submissions:
"New LSMs must be accompanied by a test suite to verify basic
functionality and help identify regressions. The test suite
must be publicly available without download restrictions
requiring accounts, subscriptions, etc. Test coverage does
not need to reach a specific percentage, but core functionality
and any user interfaces should be well covered by the test
suite. Maintaining the test suite in a public git repository is
preferable over tarball snapshots. Integrating the test suite
with existing automated Linux kernel testing services is
encouraged."
https://github.com/LinuxSecurityModule/kernel/blob/main/README.md#new-lsm-guidelines
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> v1-v6:
> + Not present
>
> v7:
> Introduced
>
> v8:
> + Remove the kunit tests with respect to the fsverity digest, as these
> require significant changes to work with the new method of acquiring
> the digest at runtime.
>
> v9:
> + Remove the kunit tests related to ipe_context
>
> v10:
> + No changes
>
> v11:
> + No changes
> ---
> security/ipe/Kconfig | 17 +++
> security/ipe/Makefile | 3 +
> security/ipe/policy_tests.c | 294 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 314 insertions(+)
> create mode 100644 security/ipe/policy_tests.c
--
paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> IPE's interpretation of the what the user trusts is accomplished through
>> its policy. IPE's design is to not provide support for a single trust
>> provider, but to support multiple providers to enable the end-user to
>> choose the best one to seek their needs.
>>
>> This requires the policy to be rather flexible and modular so that
>> integrity providers, like fs-verity, dm-verity, dm-integrity, or
>> some other system, can plug into the policy with minimal code changes.
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
...
>> ---
>> security/ipe/Makefile | 2 +
>> security/ipe/policy.c | 101 ++++++++
>> security/ipe/policy.h | 83 ++++++
>> security/ipe/policy_parser.c | 487 +++++++++++++++++++++++++++++++++++
>> security/ipe/policy_parser.h | 11 +
>> 5 files changed, 684 insertions(+)
>> create mode 100644 security/ipe/policy.c
>> create mode 100644 security/ipe/policy.h
>> create mode 100644 security/ipe/policy_parser.c
>> create mode 100644 security/ipe/policy_parser.h
>
> ...
>
>> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
>> new file mode 100644
>> index 000000000000..3a529c7950a1
>> --- /dev/null
>> +++ b/security/ipe/policy.c
>> @@ -0,0 +1,101 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) Microsoft Corporation. All rights reserved.
>> + */
>
> ...
>
>> +static int set_pkcs7_data(void *ctx, const void *data, size_t len,
>> + size_t asn1hdrlen)
>> +{
>> + struct ipe_policy *p = ctx;
>> +
>> + p->text = (const char *)data;
>> + p->textlen = len;
>> +
>> + return 0;
>> +}
>
> The @asn1hdrlen parameter isn't used in this function, at least at this
> point in the patchset, so you really should remove it. If it is needed
> later in the patchset you can always update the function.
>
Although the @asn1hdrlen is not used, it's a required parameter for the
pkcs7 callback. I guess adding a __always_unused might be the right
solution?
>> diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
>> new file mode 100644
>> index 000000000000..c09458bd348d
>> --- /dev/null
>> +++ b/security/ipe/policy_parser.c
>> @@ -0,0 +1,487 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) Microsoft Corporation. All rights reserved.
>> + */
>
> ...
>
>> +/**
>> + * remove_trailing_spaces - Truncate all trailing spaces in a string.
>> + *
>> + * @line: Supplies a poilcy line string for preprocessing.
>> + *
>> + * Return: The length of truncated string.
>> + */
>> +static size_t remove_trailing_spaces(char *line)
>> +{
>> + size_t i = 0;
>> +
>> + for (i = strlen(line); i > 0 && (line[i - 1] == ' ' || line[i - 1] == '\t'); --i)
>> + ;
>
> Maybe I've asked this before, I can't remember: could you use the
> isspace() macro here instead of explicitly checking for ' ' and '\t'?
> Yes, isspace() works here. I will update this part.
> i = strlen(line);
> while (i > 0 && isspace(line[i - 1]))
> i--;
> line[i] = '\0';
>
>> + line[i] = '\0';
>> +
>> + return i;
>> +}
>> +
>> +/**
>> + * parse_version - Parse policy version.
>> + * @ver: Supplies a version string to be parsed.
>> + * @p: Supplies the partial parsed policy.
>> + *
>> + * Return:
>> + * * 0 - OK
>> + * * !0 - Standard errno
>> + */
>> +static int parse_version(char *ver, struct ipe_parsed_policy *p)
>> +{
>> + int rc = 0;
>> + size_t sep_count = 0;
>> + char *token;
>> + u16 *const cv[] = { &p->version.major, &p->version.minor, &p->version.rev };
>> +
>> + while ((token = strsep(&ver, ".")) != NULL) {
>> + /* prevent overflow */
>> + if (sep_count >= ARRAY_SIZE(cv))
>> + return -EBADMSG;
>> +
>> + rc = kstrtou16(token, 10, cv[sep_count]);
>> + if (rc)
>> + return rc;
>> +
>> + ++sep_count;
>> + }
>> +
>> + /* prevent underflow */
>> + if (sep_count != ARRAY_SIZE(cv))
>> + rc = -EBADMSG;
>
> You could always just 'return -EBADMSG' here and 'return 0' below to
> simplify things a little.
>
I agree, this part is kind of unnecessary. I will update accordingly.
>> + return rc;
>> +}
>> +
>> +enum header_opt {
>> + IPE_HEADER_POLICY_NAME = 0,
>> + IPE_HEADER_POLICY_VERSION,
>> + __IPE_HEADER_MAX
>> +};
>> +
>> +static const match_table_t header_tokens = {
>> + {IPE_HEADER_POLICY_NAME, "policy_name=%s"},
>> + {IPE_HEADER_POLICY_VERSION, "policy_version=%s"},
>> + {__IPE_HEADER_MAX, NULL}
>> +};
>> +
>> +/**
>> + * parse_header - Parse policy header information.
>> + * @line: Supplies header line to be parsed.
>> + * @p: Supplies the partial parsed policy.
>> + *
>> + * Return:
>> + * * 0 - OK
>> + * * !0 - Standard errno
>> + */
>> +static int parse_header(char *line, struct ipe_parsed_policy *p)
>> +{
>> + int rc = 0;
>> + char *t, *ver = NULL;
>> + substring_t args[MAX_OPT_ARGS];
>> + size_t idx = 0;
>> +
>> + while ((t = strsep(&line, IPE_POLICY_DELIM)) != NULL) {
>> + int token;
>> +
>> + if (*t == '\0')
>> + continue;
>> + if (idx >= __IPE_HEADER_MAX) {
>> + rc = -EBADMSG;
>> + goto out;
>> + }
>> +
>> + token = match_token(t, header_tokens, args);
>> + if (token != idx) {
>> + rc = -EBADMSG;
>> + goto out;
>> + }
>> +
>> + switch (token) {
>> + case IPE_HEADER_POLICY_NAME:
>> + p->name = match_strdup(&args[0]);
>> + if (!p->name)
>> + rc = -ENOMEM;
>> + break;
>> + case IPE_HEADER_POLICY_VERSION:
>> + ver = match_strdup(&args[0]);
>> + if (!ver) {
>> + rc = -ENOMEM;
>> + break;
>> + }
>> + rc = parse_version(ver, p);
>> + break;
>> + default:
>> + rc = -EBADMSG;
>> + }
>> + if (rc)
>> + goto out;
>> + ++idx;
>> + }
>> +
>> + if (idx != __IPE_HEADER_MAX) {
>> + rc = -EBADMSG;
>> + goto out;
>
> You probably don't need to 'goto out' here.
>
Yes it's unnecessary, thanks for pointing that out.
>> + }
>> +
>> +out:
>> + kfree(ver);
>> + return rc;
>> +}
>
> ...
>
>> +/**
>> + * parse_rule - parse a policy rule line.
>> + * @line: Supplies rule line to be parsed.
>> + * @p: Supplies the partial parsed policy.
>> + *
>> + * Return:
>> + * * !IS_ERR - OK
>> + * * -ENOMEM - Out of memory
>> + * * -EBADMSG - Policy syntax error
>> + */
>> +static int parse_rule(char *line, struct ipe_parsed_policy *p)
>> +{
>> + int rc = 0;
>> + bool first_token = true, is_default_rule = false;
>> + bool op_parsed = false;
>> + enum ipe_op_type op = IPE_OP_INVALID;
>> + enum ipe_action_type action = IPE_ACTION_INVALID;
>> + struct ipe_rule *r = NULL;
>> + char *t;
>> +
>> + r = kzalloc(sizeof(*r), GFP_KERNEL);
>> + if (!r)
>> + return -ENOMEM;
>> +
>> + INIT_LIST_HEAD(&r->next);
>> + INIT_LIST_HEAD(&r->props);
>> +
>> + while (t = strsep(&line, IPE_POLICY_DELIM), line) {
>> + if (*t == '\0')
>> + continue;
>> + if (first_token && token_default(t)) {
>> + is_default_rule = true;
>> + } else {
>> + if (!op_parsed) {
>> + op = parse_operation(t);
>> + if (op == IPE_OP_INVALID)
>> + rc = -EBADMSG;
>> + else
>> + op_parsed = true;
>> + } else {
>> + rc = parse_property(t, r);
>> + }
>> + }
>> +
>> + if (rc)
>> + goto err;
>> + first_token = false;
>> + }
>> +
>> + action = parse_action(t);
>> + if (action == IPE_ACTION_INVALID) {
>> + rc = -EBADMSG;
>> + goto err;
>> + }
>> +
>> + if (is_default_rule) {
>> + if (!list_empty(&r->props)) {
>> + rc = -EBADMSG;
>> + } else if (op == IPE_OP_INVALID) {
>> + if (p->global_default_action != IPE_ACTION_INVALID)
>> + rc = -EBADMSG;
>> + else
>> + p->global_default_action = action;
>> + } else {
>> + if (p->rules[op].default_action != IPE_ACTION_INVALID)
>> + rc = -EBADMSG;
>> + else
>> + p->rules[op].default_action = action;
>> + }
>> + } else if (op != IPE_OP_INVALID && action != IPE_ACTION_INVALID) {
>> + r->op = op;
>> + r->action = action;
>> + } else {
>> + rc = -EBADMSG;
>> + }
>
> I might be missing something important in the policy syntac, but could
> this function, and perhaps the ipe_parsed_policy struct, be simplified
> if the default action was an explicit rule?
>
> "op=DEFAULT action=ALLOW"
>
The complexity here arises from our need for two types of default rules:
one for global settings and another for operation-specific settings.
To illustrate the flexibility of operation-specific default rules, users
can set their policy to have a default rule of 'DENY' for execution,
meaning all execution actions are prohibited by default. This let users
to create an allow-list for execution. At the same time, the default
rule for read can be set to 'ALLOW'. This let users to create an
deny-list for read.
Adding explicit default rules can simplify ipe_parsed_policy struct, but
that impose a burden on users that requires users always add the default
rules the end of the policy. In contrast, our current design allows
users to place the default rule anywhere in the policy. In practice, we
often position the default rule at the beginning of the policy, which
makes it more convenient for users to add new rules.
>> + if (rc)
>> + goto err;
>> + if (!is_default_rule)
>> + list_add_tail(&r->next, &p->rules[op].rules);
>> + else
>> + free_rule(r);
>> +
>> + return rc;
>> +err:
>> + free_rule(r);
>> + return rc;
>> +}
>> +
>> +/**
>> + * free_parsed_policy - free a parsed policy structure.
>> + * @p: Supplies the parsed policy.
>> + */
>> +void free_parsed_policy(struct ipe_parsed_policy *p)
>> +{
>> + size_t i = 0;
>> + struct ipe_rule *pp, *t;
>> +
>> + if (IS_ERR_OR_NULL(p))
>> + return;
>> +
>> + for (i = 0; i < ARRAY_SIZE(p->rules); ++i)
>> + list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) {
>> + list_del(&pp->next);
>> + free_rule(pp);
>> + }
>> +
>> + kfree(p->name);
>> + kfree(p);
>> +}
>> +
>> +/**
>> + * validate_policy - validate a parsed policy.
>> + * @p: Supplies the fully parsed policy.
>> + *
>> + * Given a policy structure that was just parsed, validate that all
>> + * necessary fields are present, initialized correctly.
>> + *
>> + * A parsed policy can be in an invalid state for use (a default was
>> + * undefined) by just parsing the policy.
>> + *
>> + * Return:
>> + * * 0 - OK
>> + * * -EBADMSG - Policy is invalid
>> + */
>> +static int validate_policy(const struct ipe_parsed_policy *p)
>> +{
>> + size_t i = 0;
>> +
>> + if (p->global_default_action != IPE_ACTION_INVALID)
>> + return 0;
>
> Should the if conditional above be "==" and not "!="?
>No, "!=" is the correct one.
The purpose of validation is to ensure that we have enough default rules
to cover all cases. If the global default action not invalid, it means
we have a global default rule in the policy to cover all cases, thus we
simply return 0.
However, if there is no global default rule, then we need to ensure that
for each operation, there is a operation specific default rule, this is
validated in the for loop below.
-Fan
>> + for (i = 0; i < ARRAY_SIZE(p->rules); ++i) {
>> + if (p->rules[i].default_action == IPE_ACTION_INVALID)
>> + return -EBADMSG;
>> + }
>> +
>> + return 0;
>> +}
>
> --
> paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> IPE is designed to provide system level trust guarantees, this usually
>> implies that trust starts from bootup with a hardware root of trust,
>> which validates the bootloader. After this, the bootloader verifies the
>> kernel and the initramfs.
>>
>> As there's no currently supported integrity method for initramfs, and
>> it's typically already verified by the bootloader, introduce a property
>> that causes the first superblock to have an execution to be "pinned",
>> which is typically initramfs.
>>
>> When the "pinned" device is unmounted, it will be "unpinned" and
>> `boot_verified` property will always evaluate to false afterward.
>>
>> We use a pointer with a spin_lock to "pin" the device instead of rcu
>> because rcu synchronization may sleep, which is not allowed when
>> unmounting a device.
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
...
>> ---
>> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
>> security/ipe/eval.h | 2 +
>> security/ipe/hooks.c | 12 ++++++
>> security/ipe/hooks.h | 2 +
>> security/ipe/ipe.c | 1 +
>> security/ipe/policy.h | 2 +
>> security/ipe/policy_parser.c | 35 +++++++++++++++++-
>> 7 files changed, 124 insertions(+), 2 deletions(-)
>>
>> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
>> index 8a8bcc5c7d7f..bdac4abc0ddb 100644
>> --- a/security/ipe/eval.c
>> +++ b/security/ipe/eval.c
>> @@ -9,6 +9,7 @@
>> #include <linux/file.h>
>> #include <linux/sched.h>
>> #include <linux/rcupdate.h>
>> +#include <linux/spinlock.h>
>>
>> #include "ipe.h"
>> #include "eval.h"
>> @@ -16,6 +17,44 @@
>>
>> struct ipe_policy __rcu *ipe_active_policy;
>>
>> +static const struct super_block *pinned_sb;
>> +static DEFINE_SPINLOCK(pin_lock);
>> +#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
>> +
>> +/**
>> + * pin_sb - Pin the underlying superblock of @f, marking it as trusted.
>> + * @sb: Supplies a super_block structure to be pinned.
>> + */
>> +static void pin_sb(const struct super_block *sb)
>> +{
>> + if (!sb)
>> + return;
>> + spin_lock(&pin_lock);
>> + if (!pinned_sb)
>> + pinned_sb = sb;
>> + spin_unlock(&pin_lock);
>> +}
>> +
>> +/**
>> + * from_pinned - Determine whether @sb is the pinned super_block.
>> + * @sb: Supplies a super_block to check against the pinned super_block.
>> + *
>> + * Return:
>> + * * true - @sb is the pinned super_block
>> + * * false - @sb is not the pinned super_block
>> + */
>> +static bool from_pinned(const struct super_block *sb)
>> +{
>> + bool rv;
>> +
>> + if (!sb)
>> + return false;
>> + spin_lock(&pin_lock);
>> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
>> + spin_unlock(&pin_lock);
>
> It's okay for an initial version, but I still think you need to get
> away from this spinlock in from_pinned() as quickly as possible.
> Maybe I'm wrong, but this looks like a major source of lock contention.
>
> I understand the issue around RCU and the potential for matching on
> a reused buffer/address, but if you modified IPE to have its own LSM
> security blob in super_block::security you could mark the superblock
> when it was mounted and do a lockless lookup here in from_pinned().
>
Thank you for the suggestion. After some testing, I discovered that
switching to RCU to pin the super block and using a security blob to
mark a pinned super block works. This approach do avoid many spinlock
operations. I'll incorporate these changes in the next version of the patch.
-Fan
>> + return rv;
>> +}
>
> --
> paul-moore.com
On Wed, Oct 25, 2023 at 6:46 PM Fan Wu <[email protected]> wrote:
> On 10/23/2023 8:52 PM, Paul Moore wrote:
> > On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >>
> >> IPE's interpretation of the what the user trusts is accomplished through
> >> its policy. IPE's design is to not provide support for a single trust
> >> provider, but to support multiple providers to enable the end-user to
> >> choose the best one to seek their needs.
> >>
> >> This requires the policy to be rather flexible and modular so that
> >> integrity providers, like fs-verity, dm-verity, dm-integrity, or
> >> some other system, can plug into the policy with minimal code changes.
> >>
> >> Signed-off-by: Deven Bowers <[email protected]>
> >> Signed-off-by: Fan Wu <[email protected]>
> ...
> >> ---
> >> security/ipe/Makefile | 2 +
> >> security/ipe/policy.c | 101 ++++++++
> >> security/ipe/policy.h | 83 ++++++
> >> security/ipe/policy_parser.c | 487 +++++++++++++++++++++++++++++++++++
> >> security/ipe/policy_parser.h | 11 +
> >> 5 files changed, 684 insertions(+)
> >> create mode 100644 security/ipe/policy.c
> >> create mode 100644 security/ipe/policy.h
> >> create mode 100644 security/ipe/policy_parser.c
> >> create mode 100644 security/ipe/policy_parser.h
> >
> > ...
> >
> >> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
> >> new file mode 100644
> >> index 000000000000..3a529c7950a1
> >> --- /dev/null
> >> +++ b/security/ipe/policy.c
> >> @@ -0,0 +1,101 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Copyright (C) Microsoft Corporation. All rights reserved.
> >> + */
> >
> > ...
> >
> >> +static int set_pkcs7_data(void *ctx, const void *data, size_t len,
> >> + size_t asn1hdrlen)
> >> +{
> >> + struct ipe_policy *p = ctx;
> >> +
> >> + p->text = (const char *)data;
> >> + p->textlen = len;
> >> +
> >> + return 0;
> >> +}
> >
> > The @asn1hdrlen parameter isn't used in this function, at least at this
> > point in the patchset, so you really should remove it. If it is needed
> > later in the patchset you can always update the function.
>
> Although the @asn1hdrlen is not used, it's a required parameter for the
> pkcs7 callback. I guess adding a __always_unused might be the right
> solution?
Ah gotcha, I'm sorry for the noise, I obviously didn't catch that. As
for the __always_unused marking, yes, that's probably a good idea.
> >> +/**
> >> + * parse_rule - parse a policy rule line.
> >> + * @line: Supplies rule line to be parsed.
> >> + * @p: Supplies the partial parsed policy.
> >> + *
> >> + * Return:
> >> + * * !IS_ERR - OK
> >> + * * -ENOMEM - Out of memory
> >> + * * -EBADMSG - Policy syntax error
> >> + */
> >> +static int parse_rule(char *line, struct ipe_parsed_policy *p)
> >> +{
> >> + int rc = 0;
> >> + bool first_token = true, is_default_rule = false;
> >> + bool op_parsed = false;
> >> + enum ipe_op_type op = IPE_OP_INVALID;
> >> + enum ipe_action_type action = IPE_ACTION_INVALID;
> >> + struct ipe_rule *r = NULL;
> >> + char *t;
> >> +
> >> + r = kzalloc(sizeof(*r), GFP_KERNEL);
> >> + if (!r)
> >> + return -ENOMEM;
> >> +
> >> + INIT_LIST_HEAD(&r->next);
> >> + INIT_LIST_HEAD(&r->props);
> >> +
> >> + while (t = strsep(&line, IPE_POLICY_DELIM), line) {
> >> + if (*t == '\0')
> >> + continue;
> >> + if (first_token && token_default(t)) {
> >> + is_default_rule = true;
> >> + } else {
> >> + if (!op_parsed) {
> >> + op = parse_operation(t);
> >> + if (op == IPE_OP_INVALID)
> >> + rc = -EBADMSG;
> >> + else
> >> + op_parsed = true;
> >> + } else {
> >> + rc = parse_property(t, r);
> >> + }
> >> + }
> >> +
> >> + if (rc)
> >> + goto err;
> >> + first_token = false;
> >> + }
> >> +
> >> + action = parse_action(t);
> >> + if (action == IPE_ACTION_INVALID) {
> >> + rc = -EBADMSG;
> >> + goto err;
> >> + }
> >> +
> >> + if (is_default_rule) {
> >> + if (!list_empty(&r->props)) {
> >> + rc = -EBADMSG;
> >> + } else if (op == IPE_OP_INVALID) {
> >> + if (p->global_default_action != IPE_ACTION_INVALID)
> >> + rc = -EBADMSG;
> >> + else
> >> + p->global_default_action = action;
> >> + } else {
> >> + if (p->rules[op].default_action != IPE_ACTION_INVALID)
> >> + rc = -EBADMSG;
> >> + else
> >> + p->rules[op].default_action = action;
> >> + }
> >> + } else if (op != IPE_OP_INVALID && action != IPE_ACTION_INVALID) {
> >> + r->op = op;
> >> + r->action = action;
> >> + } else {
> >> + rc = -EBADMSG;
> >> + }
> >
> > I might be missing something important in the policy syntac, but could
> > this function, and perhaps the ipe_parsed_policy struct, be simplified
> > if the default action was an explicit rule?
> >
> > "op=DEFAULT action=ALLOW"
>
> The complexity here arises from our need for two types of default rules:
> one for global settings and another for operation-specific settings.
>
> To illustrate the flexibility of operation-specific default rules, users
> can set their policy to have a default rule of 'DENY' for execution,
> meaning all execution actions are prohibited by default. This let users
> to create an allow-list for execution. At the same time, the default
> rule for read can be set to 'ALLOW'. This let users to create an
> deny-list for read.
>
> Adding explicit default rules can simplify ipe_parsed_policy struct, but
> that impose a burden on users that requires users always add the default
> rules the end of the policy. In contrast, our current design allows
> users to place the default rule anywhere in the policy. In practice, we
> often position the default rule at the beginning of the policy, which
> makes it more convenient for users to add new rules.
Okay, thanks for the explanation.
> >> +/**
> >> + * free_parsed_policy - free a parsed policy structure.
> >> + * @p: Supplies the parsed policy.
> >> + */
> >> +void free_parsed_policy(struct ipe_parsed_policy *p)
> >> +{
> >> + size_t i = 0;
> >> + struct ipe_rule *pp, *t;
> >> +
> >> + if (IS_ERR_OR_NULL(p))
> >> + return;
> >> +
> >> + for (i = 0; i < ARRAY_SIZE(p->rules); ++i)
> >> + list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) {
> >> + list_del(&pp->next);
> >> + free_rule(pp);
> >> + }
> >> +
> >> + kfree(p->name);
> >> + kfree(p);
> >> +}
> >> +
> >> +/**
> >> + * validate_policy - validate a parsed policy.
> >> + * @p: Supplies the fully parsed policy.
> >> + *
> >> + * Given a policy structure that was just parsed, validate that all
> >> + * necessary fields are present, initialized correctly.
> >> + *
> >> + * A parsed policy can be in an invalid state for use (a default was
> >> + * undefined) by just parsing the policy.
> >> + *
> >> + * Return:
> >> + * * 0 - OK
> >> + * * -EBADMSG - Policy is invalid
> >> + */
> >> +static int validate_policy(const struct ipe_parsed_policy *p)
> >> +{
> >> + size_t i = 0;
> >> +
> >> + if (p->global_default_action != IPE_ACTION_INVALID)
> >> + return 0;
> >
> > Should the if conditional above be "==" and not "!="?
>
> >No, "!=" is the correct one.
>
> The purpose of validation is to ensure that we have enough default rules
> to cover all cases. If the global default action not invalid, it means
> we have a global default rule in the policy to cover all cases, thus we
> simply return 0.
>
> However, if there is no global default rule, then we need to ensure that
> for each operation, there is a operation specific default rule, this is
> validated in the for loop below.
Makes sense, thanks.
--
paul-moore.com
On Thu, Oct 26, 2023 at 5:33 PM Fan Wu <[email protected]> wrote:
> On 10/23/2023 8:52 PM, Paul Moore wrote:
> > On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >>
> >> IPE is designed to provide system level trust guarantees, this usually
> >> implies that trust starts from bootup with a hardware root of trust,
> >> which validates the bootloader. After this, the bootloader verifies the
> >> kernel and the initramfs.
> >>
> >> As there's no currently supported integrity method for initramfs, and
> >> it's typically already verified by the bootloader, introduce a property
> >> that causes the first superblock to have an execution to be "pinned",
> >> which is typically initramfs.
> >>
> >> When the "pinned" device is unmounted, it will be "unpinned" and
> >> `boot_verified` property will always evaluate to false afterward.
> >>
> >> We use a pointer with a spin_lock to "pin" the device instead of rcu
> >> because rcu synchronization may sleep, which is not allowed when
> >> unmounting a device.
> >>
> >> Signed-off-by: Deven Bowers <[email protected]>
> >> Signed-off-by: Fan Wu <[email protected]>
> ...
> >> ---
> >> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
> >> security/ipe/eval.h | 2 +
> >> security/ipe/hooks.c | 12 ++++++
> >> security/ipe/hooks.h | 2 +
> >> security/ipe/ipe.c | 1 +
> >> security/ipe/policy.h | 2 +
> >> security/ipe/policy_parser.c | 35 +++++++++++++++++-
> >> 7 files changed, 124 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> >> index 8a8bcc5c7d7f..bdac4abc0ddb 100644
> >> --- a/security/ipe/eval.c
> >> +++ b/security/ipe/eval.c
> >> @@ -9,6 +9,7 @@
> >> #include <linux/file.h>
> >> #include <linux/sched.h>
> >> #include <linux/rcupdate.h>
> >> +#include <linux/spinlock.h>
> >>
> >> #include "ipe.h"
> >> #include "eval.h"
> >> @@ -16,6 +17,44 @@
> >>
> >> struct ipe_policy __rcu *ipe_active_policy;
> >>
> >> +static const struct super_block *pinned_sb;
> >> +static DEFINE_SPINLOCK(pin_lock);
> >> +#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
> >> +
> >> +/**
> >> + * pin_sb - Pin the underlying superblock of @f, marking it as trusted.
> >> + * @sb: Supplies a super_block structure to be pinned.
> >> + */
> >> +static void pin_sb(const struct super_block *sb)
> >> +{
> >> + if (!sb)
> >> + return;
> >> + spin_lock(&pin_lock);
> >> + if (!pinned_sb)
> >> + pinned_sb = sb;
> >> + spin_unlock(&pin_lock);
> >> +}
> >> +
> >> +/**
> >> + * from_pinned - Determine whether @sb is the pinned super_block.
> >> + * @sb: Supplies a super_block to check against the pinned super_block.
> >> + *
> >> + * Return:
> >> + * * true - @sb is the pinned super_block
> >> + * * false - @sb is not the pinned super_block
> >> + */
> >> +static bool from_pinned(const struct super_block *sb)
> >> +{
> >> + bool rv;
> >> +
> >> + if (!sb)
> >> + return false;
> >> + spin_lock(&pin_lock);
> >> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
> >> + spin_unlock(&pin_lock);
> >
> > It's okay for an initial version, but I still think you need to get
> > away from this spinlock in from_pinned() as quickly as possible.
> > Maybe I'm wrong, but this looks like a major source of lock contention.
> >
> > I understand the issue around RCU and the potential for matching on
> > a reused buffer/address, but if you modified IPE to have its own LSM
> > security blob in super_block::security you could mark the superblock
> > when it was mounted and do a lockless lookup here in from_pinned().
>
> Thank you for the suggestion. After some testing, I discovered that
> switching to RCU to pin the super block and using a security blob to
> mark a pinned super block works. This approach do avoid many spinlock
> operations. I'll incorporate these changes in the next version of the patch.
I probably wasn't as clear as I should have been, I was thinking of
doing away with the @pinned_sb global variable entirely, as well as
its associated lock problems and simply marking the initramfs/initrd
superblock when it was mounted. I will admit that I haven't fully
thought about all the implementation details, but I think you could
leverage the security_sb_mount() hook to set a flag in IPE's
superblock metadata when the initramfs was mounted.
--
paul-moore.com
On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >
> > fsverity represents a mechanism to support both integrity and
> > authenticity protection of a file, supporting both signed and unsigned
> > digests.
> >
> > An LSM which controls access to a resource based on authenticity and
> > integrity of said resource, can then use this data to make an informed
> > decision on the authorization (provided by the LSM's policy) of said
> > claim.
> >
> > This effectively allows the extension of a policy enforcement layer in
> > LSM for fsverity, allowing for more granular control of how a
> > particular authenticity claim can be used. For example, "all (built-in)
> > signed fsverity files should be allowed to execute, but only these
> > hashes are allowed to be loaded as kernel modules".
> >
> > This enforcement must be done in kernel space, as a userspace only
> > solution would fail a simple litmus test: Download a self-contained
> > malicious binary that never touches the userspace stack. This
> > binary would still be able to execute.
> >
> > Signed-off-by: Deven Bowers <[email protected]>
> > Signed-off-by: Fan Wu <[email protected]>
> > ---
> > v1-v6:
> > + Not present
> >
> > v7:
> > Introduced
> >
> > v8:
> > + Split fs/verity/ changes and security/ changes into separate patches
> > + Change signature of fsverity_create_info to accept non-const inode
> > + Change signature of fsverity_verify_signature to accept non-const inode
> > + Don't cast-away const from inode.
> > + Digest functionality dropped in favor of:
> > ("fs-verity: define a function to return the integrity protected
> > file digest")
> > + Reworded commit description and title to match changes.
> > + Fix a bug wherein no LSM implements the particular fsverity @name
> > (or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
> >
> > v9:
> > + No changes
> >
> > v10:
> > + Rename the signature blob key
> > + Cleanup redundant code
> > + Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> >
> > v11:
> > + No changes
> > ---
> > fs/verity/fsverity_private.h | 2 +-
> > fs/verity/open.c | 26 +++++++++++++++++++++++++-
> > include/linux/fsverity.h | 2 ++
> > 3 files changed, 28 insertions(+), 2 deletions(-)
>
> We need an ACK from some VFS folks on this.
Eric and/or Ted, can we get either an ACK or some feedback on this patch?
For reference, the full patchset can be found on lore at the link below:
https://lore.kernel.org/linux-security-module/[email protected]/
> > diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> > index d071a6e32581..4a82716e852f 100644
> > --- a/fs/verity/fsverity_private.h
> > +++ b/fs/verity/fsverity_private.h
> > @@ -108,7 +108,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
> > unsigned int log_blocksize,
> > const u8 *salt, size_t salt_size);
> >
> > -struct fsverity_info *fsverity_create_info(const struct inode *inode,
> > +struct fsverity_info *fsverity_create_info(struct inode *inode,
> > struct fsverity_descriptor *desc);
> >
> > void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
> > diff --git a/fs/verity/open.c b/fs/verity/open.c
> > index 6c31a871b84b..5b48e2c39086 100644
> > --- a/fs/verity/open.c
> > +++ b/fs/verity/open.c
> > @@ -8,6 +8,7 @@
> > #include "fsverity_private.h"
> >
> > #include <linux/mm.h>
> > +#include <linux/security.h>
> > #include <linux/slab.h>
> >
> > static struct kmem_cache *fsverity_info_cachep;
> > @@ -172,12 +173,28 @@ static int compute_file_digest(const struct fsverity_hash_alg *hash_alg,
> > return err;
> > }
> >
> > +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> > +static int fsverity_inode_setsecurity(struct inode *inode,
> > + struct fsverity_descriptor *desc)
> > +{
> > + return security_inode_setsecurity(inode, FS_VERITY_INODE_SEC_NAME,
> > + desc->signature,
> > + le32_to_cpu(desc->sig_size), 0);
> > +}
> > +#else
> > +static inline int fsverity_inode_setsecurity(struct inode *inode,
> > + struct fsverity_descriptor *desc)
> > +{
> > + return 0;
> > +}
> > +#endif /* CONFIG_IPE_PROP_FS_VERITY*/
> > +
> > /*
> > * Create a new fsverity_info from the given fsverity_descriptor (with optional
> > * appended builtin signature), and check the signature if present. The
> > * fsverity_descriptor must have already undergone basic validation.
> > */
> > -struct fsverity_info *fsverity_create_info(const struct inode *inode,
> > +struct fsverity_info *fsverity_create_info(struct inode *inode,
> > struct fsverity_descriptor *desc)
> > {
> > struct fsverity_info *vi;
> > @@ -242,6 +259,13 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
> > spin_lock_init(&vi->hash_page_init_lock);
> > }
> >
> > + err = fsverity_inode_setsecurity(inode, desc);
> > + if (err == -EOPNOTSUPP)
> > + err = 0;
> > +
> > + if (err)
> > + goto fail;
> > +
> > return vi;
> >
> > fail:
> > diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
> > index 1eb7eae580be..9666721baf15 100644
> > --- a/include/linux/fsverity.h
> > +++ b/include/linux/fsverity.h
> > @@ -319,4 +319,6 @@ static inline int fsverity_prepare_setattr(struct dentry *dentry,
> > return 0;
> > }
> >
> > +#define FS_VERITY_INODE_SEC_NAME "fsverity.builtin-sig"
> > +
> > #endif /* _LINUX_FSVERITY_H */
> > --
> > 2.25.1
--
paul-moore.com
On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >
> > The device-mapper has a flag to mark targets as singleton, which is a
> > required flag for immutable targets. Without this flag, multiple
> > dm-verity targets can be added to a mapped device, which has no
> > practical use cases and will let dm_table_get_immutable_target return
> > NULL. This patch adds the missing flag, restricting only one
> > dm-verity target per mapped device.
> >
> > Signed-off-by: Fan Wu <[email protected]>
> > ---
> > v1-v10:
> > + Not present
> > ---
> > drivers/md/dm-verity-target.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
>
> This seems reasonable to me and matches with other users of
> DM_TARGET_IMMUTABLE.
>
> Alasdair, Mike, can we get an ACK on this?
A gentle ping with a reminder ...
For reference, the full patchset can be found on lore at the link below:
https://lore.kernel.org/linux-security-module/[email protected]/
> > diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> > index 26adcfea0302..80673b66c194 100644
> > --- a/drivers/md/dm-verity-target.c
> > +++ b/drivers/md/dm-verity-target.c
> > @@ -1503,7 +1503,7 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
> >
> > static struct target_type verity_target = {
> > .name = "verity",
> > - .features = DM_TARGET_IMMUTABLE,
> > + .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> > .version = {1, 9, 0},
> > .module = THIS_MODULE,
> > .ctr = verity_ctr,
> > --
> > 2.25.1
--
paul-moore.com
On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >
> > This patch adds a target finalize hook.
> >
> > The hook is triggered just before activating an inactive table of a
> > mapped device. If it returns an error the __bind get cancelled.
> >
> > The dm-verity target will use this hook to attach the dm-verity's
> > roothash metadata to the block_device struct of the mapped device.
> >
> > Signed-off-by: Fan Wu <[email protected]>
> > ---
> > v1-v10:
> > + Not present
> > ---
> > drivers/md/dm.c | 12 ++++++++++++
> > include/linux/device-mapper.h | 7 +++++++
> > 2 files changed, 19 insertions(+)
>
> We need an ACK and confirmation from Alasdair and/or Mike that this
> is the right approach.
A gentle ping with a reminder ...
For reference, the full patchset can be found on lore at the link below:
https://lore.kernel.org/linux-security-module/[email protected]/
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index 64a1f306c96c..3be9cc35306d 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -2239,6 +2239,18 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> > goto out;
> > }
> >
> > + for (unsigned int i = 0; i < t->num_targets; i++) {
> > + struct dm_target *ti = dm_table_get_target(t, i);
> > +
> > + if (ti->type->finalize) {
> > + ret = ti->type->finalize(ti);
> > + if (ret) {
> > + old_map = ERR_PTR(ret);
> > + goto out;
> > + }
> > + }
> > + }
> > +
> > old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
> > rcu_assign_pointer(md->map, (void *)t);
> > md->immutable_target_type = dm_table_get_immutable_target_type(t);
> > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> > index 69d0435c7ebb..4040e84a8ec7 100644
> > --- a/include/linux/device-mapper.h
> > +++ b/include/linux/device-mapper.h
> > @@ -160,6 +160,12 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff,
> > */
> > typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff,
> > void *addr, size_t bytes, struct iov_iter *i);
> > +/*
> > + * Returns:
> > + * < 0 : error
> > + * = 0 : success
> > + */
> > +typedef int (*dm_finalize_fn) (struct dm_target *target);
> >
> > void dm_error(const char *message);
> >
> > @@ -209,6 +215,7 @@ struct target_type {
> > dm_dax_direct_access_fn direct_access;
> > dm_dax_zero_page_range_fn dax_zero_page_range;
> > dm_dax_recovery_write_fn dax_recovery_write;
> > + dm_finalize_fn finalize;
> >
> > /* For internal device-mapper use. */
> > struct list_head list;
> > --
> > 2.25.1
--
paul-moore.com
On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
>
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >
> > dm-verity provides a strong guarantee of a block device's integrity. As
> > a generic way to check the integrity of a block device, it provides
> > those integrity guarantees to its higher layers, including the filesystem
> > level.
> >
> > An LSM that control access to a resource on the system based on the
> > available integrity claims can use this transitive property of
> > dm-verity, by querying the underlying block_device of a particular
> > file.
> >
> > The digest and signature information need to be stored in the block
> > device to fulfill the next requirement of authorization via LSM policy.
> > This will enable the LSM to perform revocation of devices that are still
> > mounted, prohibiting execution of files that are no longer authorized
> > by the LSM in question.
> >
> > This patch added two security hook calls in dm-verity to save the
> > dm-verity roothash and the roothash signature to the block device's
> > LSM blobs.
> >
> > Signed-off-by: Deven Bowers <[email protected]>
> > Signed-off-by: Fan Wu <[email protected]>
> > ---
> > v2:
> > + No Changes
> >
> > v3:
> > + No changes
> >
> > v4:
> > + No changes
> >
> > v5:
> > + No changes
> >
> > v6:
> > + Fix an improper cleanup that can result in
> > a leak
> >
> > v7:
> > + Squash patch 08/12, 10/12 to [11/16]
> > + Use part0 for block_device, to retrieve the block_device, when
> > calling security_bdev_setsecurity
> >
> > v8:
> > + Undo squash of 08/12, 10/12 - separating drivers/md/ from
> > security/ & block/
> > + Use common-audit function for dmverity_signature.
> > + Change implementation for storing the dm-verity digest to use the
> > newly introduced dm_verity_digest structure introduced in patch
> > 14/20.
> > + Create new structure, dm_verity_digest, containing digest algorithm,
> > size, and digest itself to pass to the LSM layer. V7 was missing the
> > algorithm.
> > + Create an associated public header containing this new structure and
> > the key values for the LSM hook, specific to dm-verity.
> > + Additional information added to commit, discussing the layering of
> > the changes and how the information passed will be used.
> >
> > v9:
> > + No changes
> >
> > v10:
> > + No changes
> >
> > v11:
> > + Add an optional field to save signature
> > + Move the security hook call to the new finalize hook
> > ---
> > drivers/md/dm-verity-target.c | 71 +++++++++++++++++++++++++++++++++++
> > drivers/md/dm-verity.h | 6 +++
> > include/linux/dm-verity.h | 19 ++++++++++
> > 3 files changed, 96 insertions(+)
> > create mode 100644 include/linux/dm-verity.h
>
> We need an ACK from Alasdair and/or Mike on this too.
A gentle ping with a reminder ...
For reference, the full patchset can be found on lore at the link below:
https://lore.kernel.org/linux-security-module/[email protected]/
> > diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> > index 80673b66c194..db58b53649e3 100644
> > --- a/drivers/md/dm-verity-target.c
> > +++ b/drivers/md/dm-verity-target.c
> > @@ -13,6 +13,7 @@
> > * access behavior.
> > */
> >
> > +#include "dm-core.h"
> > #include "dm-verity.h"
> > #include "dm-verity-fec.h"
> > #include "dm-verity-verify-sig.h"
> > @@ -22,6 +23,9 @@
> > #include <linux/scatterlist.h>
> > #include <linux/string.h>
> > #include <linux/jump_label.h>
> > +#include <linux/security.h>
> > +#include <linux/dm-verity.h>
> > +#include <crypto/hash_info.h>
> >
> > #define DM_MSG_PREFIX "verity"
> >
> > @@ -952,6 +956,17 @@ static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
> > blk_limits_io_min(limits, limits->logical_block_size);
> > }
> >
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > +static void verity_free_sig(struct dm_verity *v)
> > +{
> > + kfree(v->root_digest_sig);
> > +}
> > +#else
> > +static inline void verity_free_sig(struct dm_verity *v)
> > +{
> > +}
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > +
> > static void verity_dtr(struct dm_target *ti)
> > {
> > struct dm_verity *v = ti->private;
> > @@ -966,6 +981,7 @@ static void verity_dtr(struct dm_target *ti)
> > kfree(v->salt);
> > kfree(v->root_digest);
> > kfree(v->zero_digest);
> > + verity_free_sig(v);
> >
> > if (v->tfm)
> > crypto_free_ahash(v->tfm);
> > @@ -1157,6 +1173,25 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
> > return r;
> > }
> >
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > +static int verity_init_sig(struct dm_verity *v, const void *sig,
> > + size_t sig_size)
> > +{
> > + v->sig_size = sig_size;
> > + v->root_digest_sig = kmalloc(v->sig_size, GFP_KERNEL);
> > + if (!v->root_digest)
> > + return -ENOMEM;
> > +
> > + return 0;
> > +}
> > +#else
> > +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> > + size_t sig_size)
> > +{
> > + return 0;
> > +}
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > +
> > /*
> > * Target parameters:
> > * <version> The current format is version 1.
> > @@ -1365,6 +1400,13 @@ static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> > ti->error = "Root hash verification failed";
> > goto bad;
> > }
> > +
> > + r = verity_init_sig(v, verify_args.sig, verify_args.sig_size);
> > + if (r < 0) {
> > + ti->error = "Cannot allocate root digest signature";
> > + goto bad;
> > + }
> > +
> > v->hash_per_block_bits =
> > __fls((1 << v->hash_dev_block_bits) / v->digest_size);
> >
> > @@ -1501,6 +1543,32 @@ int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned i
> > return 0;
> > }
> >
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > +static int verity_finalize(struct dm_target *ti)
> > +{
> > + struct block_device *bdev;
> > + struct dm_verity_digest root_digest;
> > + struct dm_verity *v;
> > + int r;
> > +
> > + v = ti->private;
> > + bdev = dm_table_get_md(ti->table)->disk->part0;
> > + root_digest.digest = v->root_digest;
> > + root_digest.digest_len = v->digest_size;
> > + root_digest.algo = v->alg_name;
> > +
> > + r = security_bdev_setsecurity(bdev, DM_VERITY_ROOTHASH_SEC_NAME, &root_digest,
> > + sizeof(root_digest));
> > + if (r)
> > + return r;
> > +
> > + return security_bdev_setsecurity(bdev,
> > + DM_VERITY_SIGNATURE_SEC_NAME,
> > + v->root_digest_sig,
> > + v->sig_size);
> > +}
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > +
> > static struct target_type verity_target = {
> > .name = "verity",
> > .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> > @@ -1513,6 +1581,9 @@ static struct target_type verity_target = {
> > .prepare_ioctl = verity_prepare_ioctl,
> > .iterate_devices = verity_iterate_devices,
> > .io_hints = verity_io_hints,
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > + .finalize = verity_finalize,
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > };
> > module_dm(verity);
> >
> > diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
> > index 2f555b420367..a093d4a54615 100644
> > --- a/drivers/md/dm-verity.h
> > +++ b/drivers/md/dm-verity.h
> > @@ -42,6 +42,9 @@ struct dm_verity {
> > u8 *root_digest; /* digest of the root block */
> > u8 *salt; /* salt: its size is salt_size */
> > u8 *zero_digest; /* digest for a zero block */
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > + u8 *root_digest_sig; /* digest signature of the root block */
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > unsigned int salt_size;
> > sector_t data_start; /* data offset in 512-byte sectors */
> > sector_t hash_start; /* hash start in blocks */
> > @@ -55,6 +58,9 @@ struct dm_verity {
> > bool hash_failed:1; /* set if hash of any block failed */
> > bool use_tasklet:1; /* try to verify in tasklet before work-queue */
> > unsigned int digest_size; /* digest size for the current hash algorithm */
> > +#ifdef CONFIG_IPE_PROP_DM_VERITY
> > + unsigned int sig_size; /* digest signature size */
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > unsigned int ahash_reqsize;/* the size of temporary space for crypto */
> > enum verity_mode mode; /* mode for handling verification errors */
> > unsigned int corrupted_errs;/* Number of errors for corrupted blocks */
> > diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
> > new file mode 100644
> > index 000000000000..bb0413d55d72
> > --- /dev/null
> > +++ b/include/linux/dm-verity.h
> > @@ -0,0 +1,19 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +#ifndef _LINUX_DM_VERITY_H
> > +#define _LINUX_DM_VERITY_H
> > +
> > +#include <linux/types.h>
> > +#include <crypto/hash_info.h>
> > +#include <linux/device-mapper.h>
> > +
> > +struct dm_verity_digest {
> > + const char *algo;
> > + const u8 *digest;
> > + size_t digest_len;
> > +};
> > +
> > +#define DM_VERITY_SIGNATURE_SEC_NAME DM_NAME ".verity-signature"
> > +#define DM_VERITY_ROOTHASH_SEC_NAME DM_NAME ".verity-roothash"
> > +
> > +#endif /* _LINUX_DM_VERITY_H */
> > --
> > 2.25.1
--
paul-moore.com
On Wed, Nov 01, 2023 at 08:40:06PM -0400, Paul Moore wrote:
> On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
> > On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> > >
> > > fsverity represents a mechanism to support both integrity and
> > > authenticity protection of a file, supporting both signed and unsigned
> > > digests.
> > >
> > > An LSM which controls access to a resource based on authenticity and
> > > integrity of said resource, can then use this data to make an informed
> > > decision on the authorization (provided by the LSM's policy) of said
> > > claim.
> > >
> > > This effectively allows the extension of a policy enforcement layer in
> > > LSM for fsverity, allowing for more granular control of how a
> > > particular authenticity claim can be used. For example, "all (built-in)
> > > signed fsverity files should be allowed to execute, but only these
> > > hashes are allowed to be loaded as kernel modules".
> > >
> > > This enforcement must be done in kernel space, as a userspace only
> > > solution would fail a simple litmus test: Download a self-contained
> > > malicious binary that never touches the userspace stack. This
> > > binary would still be able to execute.
> > >
> > > Signed-off-by: Deven Bowers <[email protected]>
> > > Signed-off-by: Fan Wu <[email protected]>
> > > ---
> > > v1-v6:
> > > + Not present
> > >
> > > v7:
> > > Introduced
> > >
> > > v8:
> > > + Split fs/verity/ changes and security/ changes into separate patches
> > > + Change signature of fsverity_create_info to accept non-const inode
> > > + Change signature of fsverity_verify_signature to accept non-const inode
> > > + Don't cast-away const from inode.
> > > + Digest functionality dropped in favor of:
> > > ("fs-verity: define a function to return the integrity protected
> > > file digest")
> > > + Reworded commit description and title to match changes.
> > > + Fix a bug wherein no LSM implements the particular fsverity @name
> > > (or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
> > >
> > > v9:
> > > + No changes
> > >
> > > v10:
> > > + Rename the signature blob key
> > > + Cleanup redundant code
> > > + Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> > >
> > > v11:
> > > + No changes
> > > ---
> > > fs/verity/fsverity_private.h | 2 +-
> > > fs/verity/open.c | 26 +++++++++++++++++++++++++-
> > > include/linux/fsverity.h | 2 ++
> > > 3 files changed, 28 insertions(+), 2 deletions(-)
> >
> > We need an ACK from some VFS folks on this.
>
> Eric and/or Ted, can we get either an ACK or some feedback on this patch?
>
> For reference, the full patchset can be found on lore at the link below:
>
> https://lore.kernel.org/linux-security-module/[email protected]/
Well, technically I already gave some (minor) feedback on this exact patch, and
it's not yet been addressed:
https://lore.kernel.org/linux-security-module/[email protected]/
Of course, it would also be nice if the commit message mentioned what the patch
actually does.
At a higher level, I've said before, I'm not super happy about the use of
fsverity builtin signatures growing. (For some of the reasons why, see the
guidance in the fsverity documentation at
https://docs.kernel.org/filesystems/fsverity.html#built-in-signature-verification)
That being said, if the people who are doing the broader review of IPE believe
this is how its fsverity integration should work, I can live with that; I don't
intend to block the IPE patchset if enough people want it to be merged. I've
really been hoping to see engagement with the people involved in IMA, as IPE
basically duplicates/replaces IMA. But I haven't seen that, so maybe things
need to move on without them.
- Eric
On Wed, Nov 1, 2023 at 10:54 PM Eric Biggers <[email protected]> wrote:
> On Wed, Nov 01, 2023 at 08:40:06PM -0400, Paul Moore wrote:
> > On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
> > > On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> > > >
> > > > fsverity represents a mechanism to support both integrity and
> > > > authenticity protection of a file, supporting both signed and unsigned
> > > > digests.
> > > >
> > > > An LSM which controls access to a resource based on authenticity and
> > > > integrity of said resource, can then use this data to make an informed
> > > > decision on the authorization (provided by the LSM's policy) of said
> > > > claim.
> > > >
> > > > This effectively allows the extension of a policy enforcement layer in
> > > > LSM for fsverity, allowing for more granular control of how a
> > > > particular authenticity claim can be used. For example, "all (built-in)
> > > > signed fsverity files should be allowed to execute, but only these
> > > > hashes are allowed to be loaded as kernel modules".
> > > >
> > > > This enforcement must be done in kernel space, as a userspace only
> > > > solution would fail a simple litmus test: Download a self-contained
> > > > malicious binary that never touches the userspace stack. This
> > > > binary would still be able to execute.
> > > >
> > > > Signed-off-by: Deven Bowers <[email protected]>
> > > > Signed-off-by: Fan Wu <[email protected]>
> > > > ---
> > > > v1-v6:
> > > > + Not present
> > > >
> > > > v7:
> > > > Introduced
> > > >
> > > > v8:
> > > > + Split fs/verity/ changes and security/ changes into separate patches
> > > > + Change signature of fsverity_create_info to accept non-const inode
> > > > + Change signature of fsverity_verify_signature to accept non-const inode
> > > > + Don't cast-away const from inode.
> > > > + Digest functionality dropped in favor of:
> > > > ("fs-verity: define a function to return the integrity protected
> > > > file digest")
> > > > + Reworded commit description and title to match changes.
> > > > + Fix a bug wherein no LSM implements the particular fsverity @name
> > > > (or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
> > > >
> > > > v9:
> > > > + No changes
> > > >
> > > > v10:
> > > > + Rename the signature blob key
> > > > + Cleanup redundant code
> > > > + Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> > > >
> > > > v11:
> > > > + No changes
> > > > ---
> > > > fs/verity/fsverity_private.h | 2 +-
> > > > fs/verity/open.c | 26 +++++++++++++++++++++++++-
> > > > include/linux/fsverity.h | 2 ++
> > > > 3 files changed, 28 insertions(+), 2 deletions(-)
> > >
> > > We need an ACK from some VFS folks on this.
> >
> > Eric and/or Ted, can we get either an ACK or some feedback on this patch?
> >
> > For reference, the full patchset can be found on lore at the link below:
> >
> > https://lore.kernel.org/linux-security-module/[email protected]/
>
> Well, technically I already gave some (minor) feedback on this exact patch, and
> it's not yet been addressed:
> https://lore.kernel.org/linux-security-module/[email protected]/
Hopefully Fan can comment on that, unless I'm forgetting some
implementation details it seems like a reasonable request.
> Of course, it would also be nice if the commit message mentioned what the patch
> actually does.
While I think the commit description does provide a reasonable summary
of IPE as it relates to fsverify, I agree that the specifics of the
changes presented in the patch are lacking. Fan, could you update the
commit description to add a paragraph explaining what IPE would do in
the security_inode_setsecurity() hook called from within
fsverity_inode_setsecurity()?
> At a higher level, I've said before, I'm not super happy about the use of
> fsverity builtin signatures growing. (For some of the reasons why, see the
> guidance in the fsverity documentation at
> https://docs.kernel.org/filesystems/fsverity.html#built-in-signature-verification)
> That being said, if the people who are doing the broader review of IPE believe
> this is how its fsverity integration should work, I can live with that ...
Fan can surely elaborate on this more, but my understanding is that
IPE can help provide the missing authorization piece.
> ... I don't
> intend to block the IPE patchset if enough people want it to be merged. I've
> really been hoping to see engagement with the people involved in IMA, as IPE
> basically duplicates/replaces IMA. But I haven't seen that, so maybe things
> need to move on without them.
We are getting a bit beyond the integration of IPE and fsverity so I
don't want to spend a lot of time here, but IPE and IMA work quite a
bit differently as they serve different purposes. IPE provides a file
authorization mechanism that grants access based on the specified
policy and the file's underlying backing store; IPE does not measure
files like IMA to provide additional integrity checking, it relies on
the storage medium's integrity mechanisms.
I have no doubt Fan could provide a much better summary if needed, and
of course there are the documentation patches in the patchset too.
--
paul-moore.com
On 11/2/2023 8:42 AM, Paul Moore wrote:
> On Wed, Nov 1, 2023 at 10:54 PM Eric Biggers <[email protected]> wrote:
>> On Wed, Nov 01, 2023 at 08:40:06PM -0400, Paul Moore wrote:
>>> On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <[email protected]> wrote:
>>>> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>>>>
>>>>> fsverity represents a mechanism to support both integrity and
>>>>> authenticity protection of a file, supporting both signed and unsigned
>>>>> digests.
>>>>>
>>>>> An LSM which controls access to a resource based on authenticity and
>>>>> integrity of said resource, can then use this data to make an informed
>>>>> decision on the authorization (provided by the LSM's policy) of said
>>>>> claim.
>>>>>
>>>>> This effectively allows the extension of a policy enforcement layer in
>>>>> LSM for fsverity, allowing for more granular control of how a
>>>>> particular authenticity claim can be used. For example, "all (built-in)
>>>>> signed fsverity files should be allowed to execute, but only these
>>>>> hashes are allowed to be loaded as kernel modules".
>>>>>
>>>>> This enforcement must be done in kernel space, as a userspace only
>>>>> solution would fail a simple litmus test: Download a self-contained
>>>>> malicious binary that never touches the userspace stack. This
>>>>> binary would still be able to execute.
>>>>>
>>>>> Signed-off-by: Deven Bowers <[email protected]>
>>>>> Signed-off-by: Fan Wu <[email protected]>
>>>>> ---
>>>>> v1-v6:
>>>>> + Not present
>>>>>
>>>>> v7:
>>>>> Introduced
>>>>>
>>>>> v8:
>>>>> + Split fs/verity/ changes and security/ changes into separate patches
>>>>> + Change signature of fsverity_create_info to accept non-const inode
>>>>> + Change signature of fsverity_verify_signature to accept non-const inode
>>>>> + Don't cast-away const from inode.
>>>>> + Digest functionality dropped in favor of:
>>>>> ("fs-verity: define a function to return the integrity protected
>>>>> file digest")
>>>>> + Reworded commit description and title to match changes.
>>>>> + Fix a bug wherein no LSM implements the particular fsverity @name
>>>>> (or LSM is disabled), and returns -EOPNOTSUPP, causing errors.
>>>>>
>>>>> v9:
>>>>> + No changes
>>>>>
>>>>> v10:
>>>>> + Rename the signature blob key
>>>>> + Cleanup redundant code
>>>>> + Make the hook call depends on CONFIG_FS_VERITY_BUILTIN_SIGNATURES
>>>>>
>>>>> v11:
>>>>> + No changes
>>>>> ---
>>>>> fs/verity/fsverity_private.h | 2 +-
>>>>> fs/verity/open.c | 26 +++++++++++++++++++++++++-
>>>>> include/linux/fsverity.h | 2 ++
>>>>> 3 files changed, 28 insertions(+), 2 deletions(-)
>>>>
>>>> We need an ACK from some VFS folks on this.
>>>
>>> Eric and/or Ted, can we get either an ACK or some feedback on this patch?
>>>
>>> For reference, the full patchset can be found on lore at the link below:
>>>
>>> https://lore.kernel.org/linux-security-module/[email protected]/
>>
>> Well, technically I already gave some (minor) feedback on this exact patch, and
>> it's not yet been addressed:
>> https://lore.kernel.org/linux-security-module/[email protected]/
Yes thanks for the review. We will certainly add the parameter
constification in the next version.
>
> Hopefully Fan can comment on that, unless I'm forgetting some
> implementation details it seems like a reasonable request.
>
>> Of course, it would also be nice if the commit message mentioned what the patch
>> actually does.
>
> While I think the commit description does provide a reasonable summary
> of IPE as it relates to fsverify, I agree that the specifics of the
> changes presented in the patch are lacking. Fan, could you update the
> commit description to add a paragraph explaining what IPE would do in
> the security_inode_setsecurity() hook called from within
> fsverity_inode_setsecurity()?
>
Sorry for the lack of clarity. The hook call happens right after the
built-in signature verification in fsverity. This hook's main job is to
allow LSM to store the verified signature so that it can be used for
future LSM checks.
>> At a higher level, I've said before, I'm not super happy about the use of
>> fsverity builtin signatures growing. (For some of the reasons why, see the
>> guidance in the fsverity documentation at
>> https://docs.kernel.org/filesystems/fsverity.html#built-in-signature-verification)
>> That being said, if the people who are doing the broader review of IPE believe
>> this is how its fsverity integration should work, I can live with that ...
>
> Fan can surely elaborate on this more, but my understanding is that
> IPE can help provide the missing authorization piece.
>
As Paul mentioned, with IPE, we can add kernel enforcement that only
files with the fs-verity built-in signature enabled are allowed.
Currently, IPE uses the above hook to save the signature in the file's
security blob, and then it decides whether to permit or deny file
operations based on the presence of the fs-verity built-in signature.
But our plans don't end there. In the future, we intend to add more
features to address the security gaps mentioned in the documentation
related to the fs-verity built-in signature. For instance, we will
introduce a certificate policy rule to limit which signatures can be
trusted, thus resolving issues related to the validity period of
certificates. Additionally, we will implement file path rules, allowing
different certificates to permit or deny access to different files.
>> ... I don't
>> intend to block the IPE patchset if enough people want it to be merged. I've
>> really been hoping to see engagement with the people involved in IMA, as IPE
>> basically duplicates/replaces IMA. But I haven't seen that, so maybe things
>> need to move on without them.
>
> We are getting a bit beyond the integration of IPE and fsverity so I
> don't want to spend a lot of time here, but IPE and IMA work quite a
> bit differently as they serve different purposes. IPE provides a file
> authorization mechanism that grants access based on the specified
> policy and the file's underlying backing store; IPE does not measure
> files like IMA to provide additional integrity checking, it relies on
> the storage medium's integrity mechanisms.
>
> I have no doubt Fan could provide a much better summary if needed, and
> of course there are the documentation patches in the patchset too.
>
I would like to emphasize that IPE is not meant to replace IMA.
IPE is a different approach, specifically designed for a particular part
of IMA's capabilities, which is "appraisal. While IPE's approach also
limits IPE's use cases to highly secure, locked-down devices where
almost everything is made read-only. In contrast, IMA is a versatile
solution suitable for a wide range of scenarios, and IPE cannot address
all of these.
In practice, we often use both IMA (including measurement and appraisal)
and IPE simultaneously in production. These two solutions can coexist
and complement each other, and they are not mutually exclusive.
-Fan
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> Allows author of IPE policy to indicate trust for a singular dm-verity
>> volume, identified by roothash, through "dmverity_roothash" and all
>> signed dm-verity volumes, through "dmverity_signature".
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
>> ---
...
>> security/ipe/Kconfig | 18 +++++
>> security/ipe/Makefile | 1 +
>> security/ipe/audit.c | 31 +++++++-
>> security/ipe/digest.c | 142 +++++++++++++++++++++++++++++++++++
>> security/ipe/digest.h | 26 +++++++
>> security/ipe/eval.c | 101 ++++++++++++++++++++++++-
>> security/ipe/eval.h | 13 ++++
>> security/ipe/hooks.c | 51 +++++++++++++
>> security/ipe/hooks.h | 8 ++
>> security/ipe/ipe.c | 15 ++++
>> security/ipe/ipe.h | 4 +
>> security/ipe/policy.h | 3 +
>> security/ipe/policy_parser.c | 24 +++++-
>> 13 files changed, 433 insertions(+), 4 deletions(-)
>> create mode 100644 security/ipe/digest.c
>> create mode 100644 security/ipe/digest.h
>
> ...
>
>> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
>> index 0dd5f10c318f..b5c58655ac74 100644
>> --- a/security/ipe/audit.c
>> +++ b/security/ipe/audit.c
>> @@ -13,6 +13,7 @@
>> #include "hooks.h"
>> #include "policy.h"
>> #include "audit.h"
>> +#include "digest.h"
>>
>> #define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
>>
>> @@ -40,8 +41,29 @@ static const char *const audit_op_names[__IPE_OP_MAX] = {
>> static const char *const audit_prop_names[__IPE_PROP_MAX] = {
>> "boot_verified=FALSE",
>> "boot_verified=TRUE",
>> +#ifdef CONFIG_IPE_PROP_DM_VERITY
>> + "dmverity_roothash=",
>> + "dmverity_signature=FALSE",
>> + "dmverity_signature=TRUE",
>> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>> };
>>
>> +#ifdef CONFIG_IPE_PROP_DM_VERITY
>> +/**
>> + * audit_dmv_roothash - audit a roothash of a dmverity volume.
>> + * @ab: Supplies a pointer to the audit_buffer to append to.
>> + * @r: Supplies a pointer to the digest structure.
>> + */
>> +static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
>> +{
>> + ipe_digest_audit(ab, rh);
>> +}
>> +#else
>> +static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
>> +{
>> +}
>> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> Since the "dmverity_roothash=" field name is going to be written to
> the audit record regardless of CONFIG_IPE_PROP_DM_VERITY we should
> ensure that it has a value of "?" instead of nothing. To fix that
> I would suggest something like this:
>
> #else
> static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
> {
> audit_log_format(ab, "?");
> }
> #endif /* CONFIG_IPE_PROP_DM_VERITY */
>
>> /**
>> * audit_rule - audit an IPE policy rule approximation.
>> * @ab: Supplies a pointer to the audit_buffer to append to.
>> @@ -53,8 +75,13 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
>>
>> audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
>>
>> - list_for_each_entry(ptr, &r->props, next)
>> - audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
>> + list_for_each_entry(ptr, &r->props, next) {
>> + audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
>> + if (ptr->type == IPE_PROP_DMV_ROOTHASH)
>> + audit_dmv_roothash(ab, ptr->value);
>
> If you wanted to avoid the roothash change above, you could change the
> code here so it didn't always write "dmverity_roothash=" into the audit
> record.
>
Yes this sounds more reasonable to me, I will change this part to a
switch case statement to avoid unnessary logging.
>> + audit_log_format(ab, " ");
>> + }
>>
>> audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
>> }
>> diff --git a/security/ipe/digest.c b/security/ipe/digest.c
>> new file mode 100644
>> index 000000000000..7a42ca71880c
>> --- /dev/null
>> +++ b/security/ipe/digest.c
>> @@ -0,0 +1,142 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) Microsoft Corporation. All rights reserved.
>> + */
>> +
>> +#include "digest.h"
>> +
>> +/**
>> + * ipe_digest_parse - parse a digest in IPE's policy.
>> + * @valstr: Supplies the string parsed from the policy.
>> + * @value: Supplies a pointer to be populated with the result.
>> + *
>> + * Digests in IPE are defined in a standard way:
>> + * <alg_name>:<hex>
>> + *
>> + * Use this function to create a property to parse the digest
>> + * consistently. The parsed digest will be saved in @value in IPE's
>> + * policy.
>> + *
>> + * Return:
>> + * * 0 - OK
>> + * * !0 - Error
>> + */
>> +int ipe_digest_parse(const char *valstr, void **value)
>
> Why is @value void? You should make it a digest_info type or simply
> skip the second parameter and return a digest_info pointer.
>
Yes it should better just return a digest_info type pointer. I will
update this part.
>> +{
>> + char *sep, *raw_digest;
>> + size_t raw_digest_len;
>> + int rc = 0;
>> + u8 *digest = NULL;
>> + struct digest_info *info = NULL;
>> +
>> + info = kzalloc(sizeof(*info), GFP_KERNEL);
>> + if (!info)
>> + return -ENOMEM;
>> +
>> + sep = strchr(valstr, ':');
>> + if (!sep) {
>> + rc = -EBADMSG;
>> + goto err;
>> + }
>> +
>> + info->alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
>> + if (!info->alg) {
>> + rc = -ENOMEM;
>> + goto err;
>> + }
>> +
>> + raw_digest = sep + 1;
>> + raw_digest_len = strlen(raw_digest);
>> + info->raw_digest = kstrndup(raw_digest, raw_digest_len, GFP_KERNEL);
>
> Since you're running a strlen() over @raw_digest, you might as well
> just use kstrdup() instead of kstrndup().
>
Thanks I will update this part.
>> + if (!info->raw_digest) {
>> + rc = -ENOMEM;
>> + goto err_free_alg;
>> + }
>> +
>> + info->digest_len = (raw_digest_len + 1) / 2;
>> + digest = kzalloc(info->digest_len, GFP_KERNEL);
>> + if (!digest) {
>> + rc = -ENOMEM;
>> + goto err_free_raw;
>> + }
>> +
>> + rc = hex2bin(digest, raw_digest, info->digest_len);
>> + if (rc < 0) {
>> + rc = -EINVAL;
>> + goto err_free_raw;
>> + }
>> +
>> + info->digest = digest;
>> + *value = info;
>> + return 0;
>> +
>> +err_free_raw:
>> + kfree(info->raw_digest);
>> +err_free_alg:
>> + kfree(info->alg);
>> +err:
>> + kfree(digest);
>> + kfree(info);
>> + return rc;
>> +}
>> +
>> +/**
>> + * ipe_digest_eval - evaluate an IPE digest against another digest.
>> + * @expect: Supplies the policy-provided digest value.
>> + * @digest: Supplies the digest to compare against the policy digest value.
>> + * @digest_len: The length of @digest.
>> + * @alg: Supplies the name of the algorithm used to calculated @digest.
>> + *
>> + * Return:
>> + * * true - digests match
>> + * * false - digests do not match
>> + */
>> +bool ipe_digest_eval(const void *expect, const u8 *digest, size_t digest_len,
>> + const char *alg)
>
> Similar to the above, why not make the @expect parameter a digest_info
> type? Also, why not pass a second digest_info parameter instead of
> a separate @digest, @digest_len, and @alg?
>
The digest_info was inteneded to be used for policy only, which also
contains a raw string of digest in the policy that can be used during
audit. After second thought I start to think the raw_digest seems
unnecessary and I can refactor them all to use digest_info instead.
>> +{
>> + const struct digest_info *info = (struct digest_info *)expect;
>> +
>> + return (digest_len == info->digest_len) && !strcmp(alg, info->alg) &&
>> + (!memcmp(info->digest, digest, info->digest_len));
>> +}
>> +
>> +/**
>> + * ipe_digest_free - free an IPE digest.
>> + * @value: Supplies a pointer the policy-provided digest value to free.
>> + */
>> +void ipe_digest_free(void **value)
>
> Another digest_info parameter/type issue.
>
>> +{
>> + struct digest_info *info = (struct digest_info *)(*value);
>> +
>> + if (IS_ERR_OR_NULL(info))
>> + return;
>> +
>> + kfree(info->alg);
>> + kfree(info->raw_digest);
>> + kfree(info->digest);
>> + kfree(info);
>> +}
>> +
>> +/**
>> + * ipe_digest_audit - audit a digest that was sourced from IPE's policy.
>> + * @ab: Supplies the audit_buffer to append the formatted result.
>> + * @val: Supplies a pointer to source the audit record from.
>> + *
>> + * Digests in IPE are defined in a standard way:
>> + * <alg_name>:<hex>
>> + *
>> + * Use this function to create a property to audit the digest
>> + * consistently.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +void ipe_digest_audit(struct audit_buffer *ab, const void *val)
>
> Another digest_info parameter/type issue.
>
>> +{
>> + const struct digest_info *info = (struct digest_info *)val;
>> +
>> + audit_log_untrustedstring(ab, info->alg);
>> + audit_log_format(ab, ":");
>> + audit_log_untrustedstring(ab, info->raw_digest);
>> +}
>
> ...
>
>> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
>> index 78c54ff1fdd3..82ad48d7aa3d 100644
>> --- a/security/ipe/eval.c
>> +++ b/security/ipe/eval.c
>> @@ -69,15 +88,89 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
>> const struct file *file,
>> enum ipe_op_type op)
>> {
>> + struct inode *ino = NULL;
>> +
>> if (op == IPE_OP_EXEC && file)
>> pin_sb(FILE_SUPERBLOCK(file));
>>
>> ctx->file = file;
>> ctx->op = op;
>>
>> - if (file)
>> + if (file) {
>> ctx->from_init_sb = from_pinned(FILE_SUPERBLOCK(file));
>> + ino = d_real_inode(file->f_path.dentry);
>> + build_ipe_bdev_ctx(ctx, ino);
>
> You don't need @ino.
>
> build_ipe_bdev_ctx(ctx, d_real_inode(file->f_path.dentry));
>
This variable will make sense in the fsverity patch, I do agree it
doesn't make sense for this one. Will remove it.
>> + }
>> +}
>> +
>> +#ifdef CONFIG_IPE_PROP_DM_VERITY
>> +/**
>> + * evaluate_dmv_roothash - Evaluate @ctx against a dmv roothash property.
>> + * @ctx: Supplies a pointer to the context being evaluated.
>> + * @p: Supplies a pointer to the property being evaluated.
>> + *
>> + * Return:
>> + * * true - The current @ctx match the @p
>> + * * false - The current @ctx doesn't match the @p
>> + */
>> +static bool evaluate_dmv_roothash(const struct ipe_eval_ctx *const ctx,
>> + struct ipe_prop *p)
>> +{
>> + return !!ctx->ipe_bdev &&
>> + ipe_digest_eval(p->value,
>> + ctx->ipe_bdev->digest,
>> + ctx->ipe_bdev->digest_len,
>> + ctx->ipe_bdev->digest_algo);
>
> Building on my comments above in ipe_digest_eval(), if you convert it
> to use digest_info structs this is simplified:
>
> ipe_digest_eval(p->vlaue, ctx->ipe_bdev)
>
Yep but the seucrity blob also contains signature information. I will
make it like ipe_digest_eval(p->vlaue, ctx->ipe_bdev->dmv_digest_info)
>> +}
>> +
>> +/**
>> + * evaluate_dmv_sig_false: Analyze @ctx against a dmv sig false property.
>> + * @ctx: Supplies a pointer to the context being evaluated.
>> + * @p: Supplies a pointer to the property being evaluated.
>> + *
>> + * Return:
>> + * * true - The current @ctx match the @p
>> + * * false - The current @ctx doesn't match the @p
>> + */
>> +static bool evaluate_dmv_sig_false(const struct ipe_eval_ctx *const ctx,
>> + struct ipe_prop *p)
>> +{
>> + return !ctx->ipe_bdev || (!ctx->ipe_bdev->dm_verity_signed);
>> +}
>> +
>> +/**
>> + * evaluate_dmv_sig_true: Analyze @ctx against a dmv sig true property.
>> + * @ctx: Supplies a pointer to the context being evaluated.
>> + * @p: Supplies a pointer to the property being evaluated.
>> + *
>> + * Return:
>> + * * true - The current @ctx match the @p
>> + * * false - The current @ctx doesn't match the @p
>> + */
>> +static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx,
>> + struct ipe_prop *p)
>> +{
>> + return ctx->ipe_bdev && (!!ctx->ipe_bdev->dm_verity_signed);
>> +}
>
> Do you need both evaluate_dmv_sig_true() and evaluate_dmv_sig_false()?
> If yes, you should make one call the other and return the inverse to
> help ensure there are no oddities.
>
Yes this code is redundant. I also found the ipe_prop *p variable is
necssary. Will clean them up in the next version.
>> diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
>> index e9386762a597..8b8031e66f36 100644
>> --- a/security/ipe/hooks.c
>> +++ b/security/ipe/hooks.c
>> @@ -193,3 +196,51 @@ void ipe_sb_free_security(struct super_block *mnt_sb)
>> {
>> ipe_invalidate_pinned_sb(mnt_sb);
>> }
>> +
>> +#ifdef CONFIG_IPE_PROP_DM_VERITY
>> +/**
>> + * ipe_bdev_free_security - free IPE's LSM blob of block_devices.
>> + * @bdev: Supplies a pointer to a block_device that contains the structure
>> + * to free.
>> + */
>> +void ipe_bdev_free_security(struct block_device *bdev)
>> +{
>> + struct ipe_bdev *blob = ipe_bdev(bdev);
>> +
>> + kfree(blob->digest);
>> + kfree(blob->digest_algo);
>> +}
>> +
>> +/**
>> + * ipe_bdev_setsecurity - save data from a bdev to IPE's LSM blob.
>> + * @bdev: Supplies a pointer to a block_device that contains the LSM blob.
>> + * @key: Supplies the string key that uniquely identifies the value.
>> + * @value: Supplies the value to store.
>> + * @len: The length of @value.
>> + */
>> +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
>> + const void *value, size_t len)
>> +{
>> + struct ipe_bdev *blob = ipe_bdev(bdev);
>> +
>> + if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) {
>> + const struct dm_verity_digest *digest = value;
>> +
>> + blob->digest = kmemdup(digest->digest, digest->digest_len, GFP_KERNEL);
>> + if (!blob->digest)
>> + return -ENOMEM;
>> +
>> + blob->digest_algo = kstrdup_const(digest->algo, GFP_KERNEL);
>> + if (!blob->digest_algo)
>> + return -ENOMEM;
>
> You need to cleanup @blob on error so you don't leak ipe_bdev::digest.
>
Thanks for catching that. I will fix this.
-Fan
>> + blob->digest_len = digest->digest_len;
>> + return 0;
>> + } else if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) {
>> + blob->dm_verity_signed = true;
>> + return 0;
>> + }
>> +
>> + return -EOPNOTSUPP;
>> +}
>> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> --
> paul-moore.com
On 10/26/2023 3:12 PM, Paul Moore wrote:
> On Thu, Oct 26, 2023 at 5:33 PM Fan Wu <[email protected]> wrote:
>> On 10/23/2023 8:52 PM, Paul Moore wrote:
>>> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>>>
>>>> IPE is designed to provide system level trust guarantees, this usually
>>>> implies that trust starts from bootup with a hardware root of trust,
>>>> which validates the bootloader. After this, the bootloader verifies the
>>>> kernel and the initramfs.
>>>>
>>>> As there's no currently supported integrity method for initramfs, and
>>>> it's typically already verified by the bootloader, introduce a property
>>>> that causes the first superblock to have an execution to be "pinned",
>>>> which is typically initramfs.
>>>>
>>>> When the "pinned" device is unmounted, it will be "unpinned" and
>>>> `boot_verified` property will always evaluate to false afterward.
>>>>
>>>> We use a pointer with a spin_lock to "pin" the device instead of rcu
>>>> because rcu synchronization may sleep, which is not allowed when
>>>> unmounting a device.
>>>>
>>>> Signed-off-by: Deven Bowers <[email protected]>
>>>> Signed-off-by: Fan Wu <[email protected]>
>> ...
>>>> ---
>>>> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
>>>> security/ipe/eval.h | 2 +
>>>> security/ipe/hooks.c | 12 ++++++
>>>> security/ipe/hooks.h | 2 +
>>>> security/ipe/ipe.c | 1 +
>>>> security/ipe/policy.h | 2 +
>>>> security/ipe/policy_parser.c | 35 +++++++++++++++++-
>>>> 7 files changed, 124 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
>>>> index 8a8bcc5c7d7f..bdac4abc0ddb 100644
>>>> --- a/security/ipe/eval.c
>>>> +++ b/security/ipe/eval.c
>>>> @@ -9,6 +9,7 @@
>>>> #include <linux/file.h>
>>>> #include <linux/sched.h>
>>>> #include <linux/rcupdate.h>
>>>> +#include <linux/spinlock.h>
>>>>
>>>> #include "ipe.h"
>>>> #include "eval.h"
>>>> @@ -16,6 +17,44 @@
>>>>
>>>> struct ipe_policy __rcu *ipe_active_policy;
>>>>
>>>> +static const struct super_block *pinned_sb;
>>>> +static DEFINE_SPINLOCK(pin_lock);
>>>> +#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
>>>> +
>>>> +/**
>>>> + * pin_sb - Pin the underlying superblock of @f, marking it as trusted.
>>>> + * @sb: Supplies a super_block structure to be pinned.
>>>> + */
>>>> +static void pin_sb(const struct super_block *sb)
>>>> +{
>>>> + if (!sb)
>>>> + return;
>>>> + spin_lock(&pin_lock);
>>>> + if (!pinned_sb)
>>>> + pinned_sb = sb;
>>>> + spin_unlock(&pin_lock);
>>>> +}
>>>> +
>>>> +/**
>>>> + * from_pinned - Determine whether @sb is the pinned super_block.
>>>> + * @sb: Supplies a super_block to check against the pinned super_block.
>>>> + *
>>>> + * Return:
>>>> + * * true - @sb is the pinned super_block
>>>> + * * false - @sb is not the pinned super_block
>>>> + */
>>>> +static bool from_pinned(const struct super_block *sb)
>>>> +{
>>>> + bool rv;
>>>> +
>>>> + if (!sb)
>>>> + return false;
>>>> + spin_lock(&pin_lock);
>>>> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
>>>> + spin_unlock(&pin_lock);
>>>
>>> It's okay for an initial version, but I still think you need to get
>>> away from this spinlock in from_pinned() as quickly as possible.
>>> Maybe I'm wrong, but this looks like a major source of lock contention.
>>>
>>> I understand the issue around RCU and the potential for matching on
>>> a reused buffer/address, but if you modified IPE to have its own LSM
>>> security blob in super_block::security you could mark the superblock
>>> when it was mounted and do a lockless lookup here in from_pinned().
>>
>> Thank you for the suggestion. After some testing, I discovered that
>> switching to RCU to pin the super block and using a security blob to
>> mark a pinned super block works. This approach do avoid many spinlock
>> operations. I'll incorporate these changes in the next version of the patch.
>
> I probably wasn't as clear as I should have been, I was thinking of
> doing away with the @pinned_sb global variable entirely, as well as
> its associated lock problems and simply marking the initramfs/initrd
> superblock when it was mounted. I will admit that I haven't fully
> thought about all the implementation details, but I think you could
> leverage the security_sb_mount() hook to set a flag in IPE's
> superblock metadata when the initramfs was mounted.
>
> --
> paul-moore.com
I wasn't able to find a way to let LSM pin initramfs/initrd during mount
time. But I think we could replace the global variable with a flag
variable ipe_sb_state so we could use atomic operation to only mark one
drive as pinned without any lock. The code will be like:
static void pin_sb(const struct super_block *sb)
{
if (!sb)
return;
if (!test_and_set_bit_lock(IPE_SB_PINNED, &ipe_sb_state)) {
ipe_sb(sb)->pinned = true;
}
}
Would this sound better?
-Fan
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> Users of IPE require a way to identify when and why an operation fails,
>> allowing them to both respond to violations of policy and be notified
>> of potentially malicious actions on their systems with respect to IPE
>> itself.
>>
>> This patch introduces 3 new audit events.
>>
>> AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation
>> of a resource.
>> AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy
>> has been changed to another loaded policy.
>> AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded
>> into the kernel.
>>
>> This patch also adds support for success auditing, allowing users to
>> identify why an allow decision was made for a resource. However, it is
>> recommended to use this option with caution, as it is quite noisy.
>>
>> Here are some examples of the new audit record types:
>>
>> AUDIT_IPE_ACCESS(1420):
>>
>> audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda"
>> ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
>>
>> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
>> ino=2 rule="DEFAULT action=DENY"
>>
>> audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs"
>> ino=131 rule="DEFAULT action=DENY"
>>
>> The above three records were generated when the active IPE policy only
>> allows binaries from the initial booted drive(sda) to run. The three
>> identical `hello` binary were placed at different locations, only the
>> first hello from sda was allowed.
>>
>> Field path followed by the file's path name.
>>
>> Field dev followed by the device name as found in /dev where the file is
>> from.
>> Note that for device mappers it will use the name `dm-X` instead of
>> the name in /dev/mapper.
>> For a file in a temp file system, which is not from a device, it will use
>> `tmpfs` for the field.
>> The implementation of this part is following another existing use case
>> LSM_AUDIT_DATA_INODE in security/lsm_audit.c
>>
>> Field ino followed by the file's inode number.
>>
>> Field rule followed by the IPE rule made the access decision. The whole
>> rule must be audited because the decision is based on the combination of
>> all property conditions in the rule.
>>
>> Along with the syscall audit event, user can know why a blocked
>> happened. For example:
>>
>> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
>> ino=2 rule="DEFAULT action=DENY"
>> audit[1956]: SYSCALL arch=c000003e syscall=59
>> success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0
>> a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 auid=4294967295 uid=0
>> gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0
>> ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null)
>>
>> The above two records showed bash used execve to run "hello" and got
>> blocked by IPE. Note that the IPE records are always prior to a SYSCALL
>> record.
>>
>> AUDIT_IPE_CONFIG_CHANGE(1421):
>>
>> audit: AUDIT1421
>> old_active_pol_name="Allow_All" old_active_pol_version=0.0.0
>> old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649
>> new_active_pol_name="boot_verified" new_active_pol_version=0.0.0
>> new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F
>> auid=4294967295 ses=4294967295 lsm=ipe res=1
>>
>> The above record showed the current IPE active policy switch from
>> `Allow_All` to `boot_verified` along with the version and the hash
>> digest of the two policies. Note IPE can only have one policy active
>> at a time, all access decision evaluation is based on the current active
>> policy.
>> The normal procedure to deploy a policy is loading the policy to deploy
>> into the kernel first, then switch the active policy to it.
>>
>> AUDIT_IPE_POLICY_LOAD(1422):
>>
>> audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0
>> policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD
>> auid=4294967295 ses=4294967295 lsm=ipe res=1
>>
>> The above record showed a new policy has been loaded into the kernel
>> with the policy name, policy version and policy hash.
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
...
>> ---
>> include/uapi/linux/audit.h | 3 +
>> security/ipe/Kconfig | 2 +-
>> security/ipe/Makefile | 1 +
>> security/ipe/audit.c | 195 +++++++++++++++++++++++++++++++++++++
>> security/ipe/audit.h | 18 ++++
>> security/ipe/eval.c | 32 ++++--
>> security/ipe/eval.h | 8 ++
>> security/ipe/fs.c | 70 +++++++++++++
>> security/ipe/policy.c | 5 +
>> 9 files changed, 327 insertions(+), 7 deletions(-)
>> create mode 100644 security/ipe/audit.c
>> create mode 100644 security/ipe/audit.h
>
> ...
>
>> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
>> new file mode 100644
>> index 000000000000..e123701d5e3b
>> --- /dev/null
>> +++ b/security/ipe/audit.c
>> @@ -0,0 +1,195 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) Microsoft Corporation. All rights reserved.
>> + */
>> +
>> +#include <linux/slab.h>
>> +#include <linux/audit.h>
>> +#include <linux/types.h>
>> +#include <crypto/hash.h>
>> +
>> +#include "ipe.h"
>> +#include "eval.h"
>> +#include "hooks.h"
>> +#include "policy.h"
>> +#include "audit.h"
>> +
>> +#define ACTSTR(x) ((x) == IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
>> +
>> +#define IPE_AUDIT_HASH_ALG "sha256"
>> +
>> +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\
>> + "policy_digest=" IPE_AUDIT_HASH_ALG ":"
>> +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\
>> + "old_active_pol_version=%hu.%hu.%hu "\
>> + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":"
>> +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\
>> + "new_active_pol_version=%hu.%hu.%hu "\
>> + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":"
>> +
>> +static const char *const audit_op_names[__IPE_OP_MAX] = {
>> + "EXECUTE",
>> + "FIRMWARE",
>> + "KMODULE",
>> + "KEXEC_IMAGE",
>> + "KEXEC_INITRAMFS",
>> + "IMA_POLICY",
>> + "IMA_X509_CERT",
>> +};
>> +
>> +static const char *const audit_prop_names[__IPE_PROP_MAX] = {
>> + "boot_verified=FALSE",
>> + "boot_verified=TRUE",
>> +};
>
> I would suggest taking the same approach for both @audit_op_names and
> @audit_prop_names; either include the field name in the string array
> for both or leave it out of both.
>
Yes sure, I will move the "op=" into audit_op_names.
>> +/**
>> + * audit_rule - audit an IPE policy rule approximation.
>> + * @ab: Supplies a pointer to the audit_buffer to append to.
>> + * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
>> + */
>> +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
>> +{
>> + const struct ipe_prop *ptr;
>> +
>> + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
>> +
>> + list_for_each_entry(ptr, &r->props, next)
>> + audit_log_format(ab, "%s ", audit_prop_names[ptr->type]);
>> +
>> + audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
>> +}
>> +
>> +/**
>> + * ipe_audit_match - audit a match for IPE policy.
>> + * @ctx: Supplies a pointer to the evaluation context that was used in the
>> + * evaluation.
>> + * @match_type: Supplies the scope of the match: rule, operation default,
>> + * global default.
>> + * @act: Supplies the IPE's evaluation decision, deny or allow.
>> + * @r: Supplies a pointer to the rule that was matched, if possible.
>> + * @enforce: Supplies the enforcement/permissive state at the point
>> + * the enforcement decision was made.
>> + */
>
> Does it make sense to move @match_type into the ipe_eval_ctx struct?
>
I feel the @match_type is part of the evaluation result information,
which is the result of the context against the active policy. So I
prefer keeping it as a local variable in the evaluation loop.
-Fan
>> +void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
>> + enum ipe_match match_type,
>> + enum ipe_action_type act, const struct ipe_rule *const r)
>> +{
>> + struct inode *inode;
>> + struct audit_buffer *ab;
>> + const char *op = audit_op_names[ctx->op];
>> +
>> + if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit))
>> + return;
>> +
>> + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
>> + if (!ab)
>> + return;
>> +
>> + if (ctx->file) {
>> + audit_log_d_path(ab, "path=", &ctx->file->f_path);
>> + inode = file_inode(ctx->file);
>> + if (inode) {
>> + audit_log_format(ab, " dev=");
>> + audit_log_untrustedstring(ab, inode->i_sb->s_id);
>> + audit_log_format(ab, " ino=%lu ", inode->i_ino);
>> + }
>> + }
>> +
>> + if (match_type == IPE_MATCH_RULE)
>> + audit_rule(ab, r);
>> + else if (match_type == IPE_MATCH_TABLE)
>> + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op,
>> + ACTSTR(act));
>> + else
>> + audit_log_format(ab, "rule=\"DEFAULT action=%s\"",
>> + ACTSTR(act));
>> +
>> + audit_log_end(ab);
>> +}
>
> --
> paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> IPE, like SELinux, supports a permissive mode. This mode allows policy
>> authors to test and evaluate IPE policy without it effecting their
>> programs. When the mode is changed, a 1404 AUDIT_MAC_STATUS
>> be reported.
>>
>> This patch adds the following audit records:
>>
>> audit: MAC_STATUS enforcing=0 old_enforcing=1 auid=4294967295
>> ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
>> audit: MAC_STATUS enforcing=1 old_enforcing=0 auid=4294967295
>> ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
>>
>> The audit record only emit when the value from the user input is
>> different from the current enforce value.
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
>> ---
>> v2:
>> + Split evaluation loop, access control hooks,
>> and evaluation loop from policy parser and userspace
>> interface to pass mailing list character limit
>>
>> v3:
>> + Move ipe_load_properties to patch 04.
>> + Remove useless 0-initializations
>> + Prefix extern variables with ipe_
>> + Remove kernel module parameters, as these are
>> exposed through sysctls.
>> + Add more prose to the IPE base config option
>> help text.
>> + Use GFP_KERNEL for audit_log_start.
>> + Remove unnecessary caching system.
>> + Remove comments from headers
>> + Use rcu_access_pointer for rcu-pointer null check
>> + Remove usage of reqprot; use prot only.
>> + Move policy load and activation audit event to 03/12
>>
>> v4:
>> + Remove sysctls in favor of securityfs nodes
>> + Re-add kernel module parameters, as these are now
>> exposed through securityfs.
>> + Refactor property audit loop to a separate function.
>>
>> v5:
>> + fix minor grammatical errors
>> + do not group rule by curly-brace in audit record,
>> reconstruct the exact rule.
>>
>> v6:
>> + No changes
>>
>> v7:
>> + Further split lsm creation into a separate commit from the
>> evaluation loop and audit system, for easier review.
>> + Propagating changes to support the new ipe_context structure in the
>> evaluation loop.
>> + Split out permissive functionality into a separate patch for easier
>> review.
>> + Remove permissive switch compile-time configuration option - this
>> is trivial to add later.
>>
>> v8:
>> + Remove "IPE" prefix from permissive audit record
>> + align fields to the linux-audit field dictionary. This causes the
>> following fields to change:
>> enforce -> permissive
>>
>> + Remove duplicated information correlated with syscall record, that
>> will always be present in the audit event.
>> + Change audit types:
>> + AUDIT_TRUST_STATUS -> AUDIT_MAC_STATUS
>> + There is no significant difference in meaning between
>> these types.
>>
>> v9:
>> + Clean up ipe_context related code
>>
>> v10:
>> + Change audit format to comform with the existing format selinux is
>> using
>> + Remove the audit record emission during init to align with selinux,
>> which does not perform this action.
>>
>> v11:
>> + Remove redundant code
>> ---
>> security/ipe/audit.c | 22 ++++++++++++++
>> security/ipe/audit.h | 1 +
>> security/ipe/eval.c | 14 +++++++--
>> security/ipe/eval.h | 1 +
>> security/ipe/fs.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
>> 5 files changed, 104 insertions(+), 2 deletions(-)
>
> ...
>
>> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
>> index 499b6b3338f2..78c54ff1fdd3 100644
>> --- a/security/ipe/eval.c
>> +++ b/security/ipe/eval.c
>> @@ -167,9 +172,12 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
>> ipe_audit_match(ctx, match_type, action, rule);
>>
>> if (action == IPE_ACTION_DENY)
>> - return -EACCES;
>> + rc = -EACCES;
>> +
>> + if (!enforcing)
>> + rc = 0;
>
> Why the local @enforcing variable? Why not:
>
> if (!READ_ONCE(enforce))
> rc = 0;
>
Yes the variable is unnecessary, I will remove it.
-Fan
>> - return 0;
>> + return rc;
>> }
>>
>> /**
>> @@ -198,3 +206,5 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
>>
>> module_param(success_audit, bool, 0400);
>> MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
>> +module_param(enforce, bool, 0400);
>> +MODULE_PARM_DESC(enforce, "Start IPE in enforce or permissive mode");
>
> "enforcing"
>
> --
> paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> Enables an IPE policy to be enforced from kernel start, enabling access
>> control based on trust from kernel startup. This is accomplished by
>> transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a
>> c-string literal that is parsed at kernel startup as an unsigned policy.
>>
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
>> ---
>> v2:
>> + No Changes
>>
>> v3:
>> + No Changes
>>
>> v4:
>> + No Changes
>>
>> v5:
>> + No Changes
>>
>> v6:
>> + No Changes
>>
>> v7:
>> + Move from 01/11 to 14/16
>> + Don't return errno directly.
>> + Make output of script more user-friendly
>> + Add escaping for tab and '?'
>> + Mark argv pointer const
>> + Invert return code check in the boot policy parsing code path.
>>
>> v8:
>> + No significant changes.
>>
>> v9:
>> + No changes
>>
>> v10:
>> + Update the init part code for rcu changes in the eval loop patch
>>
>> v11:
>> + Fix code style issues
>> ---
>> MAINTAINERS | 1 +
>> scripts/Makefile | 1 +
>> scripts/ipe/Makefile | 2 +
>> scripts/ipe/polgen/.gitignore | 1 +
>> scripts/ipe/polgen/Makefile | 6 ++
>> scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
>> security/ipe/.gitignore | 1 +
>> security/ipe/Kconfig | 10 +++
>> security/ipe/Makefile | 11 +++
>> security/ipe/fs.c | 8 ++
>> security/ipe/ipe.c | 12 +++
>> 11 files changed, 198 insertions(+)
>> create mode 100644 scripts/ipe/Makefile
>> create mode 100644 scripts/ipe/polgen/.gitignore
>> create mode 100644 scripts/ipe/polgen/Makefile
>> create mode 100644 scripts/ipe/polgen/polgen.c
>> create mode 100644 security/ipe/.gitignore
>
> ...
>
>> diff --git a/scripts/ipe/polgen/polgen.c b/scripts/ipe/polgen/polgen.c
>> new file mode 100644
>> index 000000000000..40b6fe07f47b
>> --- /dev/null
>> +++ b/scripts/ipe/polgen/polgen.c
>> @@ -0,0 +1,145 @@
>
> ...
>
>> +static int write_boot_policy(const char *pathname, const char *buf, size_t size)
>> +{
>> + int rc = 0;
>> + FILE *fd;
>> + size_t i;
>> +
>> + fd = fopen(pathname, "w");
>> + if (!fd) {
>> + rc = errno;
>> + goto err;
>> + }
>> +
>> + fprintf(fd, "/* This file is automatically generated.");
>> + fprintf(fd, " Do not edit. */\n");
>> + fprintf(fd, "#include <linux/stddef.h>\n");
>> + fprintf(fd, "\nextern const char *const ipe_boot_policy;\n\n");
>> + fprintf(fd, "const char *const ipe_boot_policy =\n");
>> +
>> + if (!buf || size == 0) {
>> + fprintf(fd, "\tNULL;\n");
>> + fclose(fd);
>> + return 0;
>> + }
>> +
>> + fprintf(fd, "\t\"");
>> +
>> + for (i = 0; i < size; ++i) {
>> + switch (buf[i]) {
>> + case '"':
>> + fprintf(fd, "\\\"");
>> + break;
>> + case '\'':
>> + fprintf(fd, "'");
>> + break;
>
> The revision of IPE proposed in this patchset doesn't support parsing
> single or double quotes, yes? >
Actually all characters can be used in the policy. The previous revision
was removing the quote syntax, which supports having space in the policy
name like policy_name="example policy". But that is not related to the
boot policy generation code here.
The code here is to generate a C source code that will be linked into
IPE. Thus we have to escape these characters to conform with the C
language string literal standard.
-Fan
>> + case '\n':
>> + fprintf(fd, "\\n\"\n\t\"");
>> + break;
>> + case '\\':
>> + fprintf(fd, "\\\\");
>> + break;
>> + case '\t':
>> + fprintf(fd, "\\t");
>> + break;
>> + case '\?':
>> + fprintf(fd, "\\?");
>> + break;
>
> Similar, are question marks supported by the parser?
>
>> + default:
>> + fprintf(fd, "%c", buf[i]);
>> + }
>> + }
>> + fprintf(fd, "\";\n");
>> + fclose(fd);
>> +
>> + return 0;
>> +
>> +err:
>> + if (fd)
>> + fclose(fd);
>> + return rc;
>> +}
>
> ...
>
>> diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore
>> new file mode 100644
>> index 000000000000..eca22ad5ed22
>> --- /dev/null
>> +++ b/security/ipe/.gitignore
>> @@ -0,0 +1 @@
>> +boot-policy.c
>> \ No newline at end of file
>
> Add a newline please.
>
> --
> paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
>>
>> Add various happy/unhappy unit tests for both IPE's parser.
>
> I'm going to suggest: "... for IPE's policy parser."
Yeah this sounds more precise.
>
> Also, aside from the policy parser tests, are there any other IPE
> functional tests? We do have a testing guideline for new LSM
> submissions:
>
> "New LSMs must be accompanied by a test suite to verify basic
> functionality and help identify regressions. The test suite
> must be publicly available without download restrictions
> requiring accounts, subscriptions, etc. Test coverage does
> not need to reach a specific percentage, but core functionality
> and any user interfaces should be well covered by the test
> suite. Maintaining the test suite in a public git repository is
> preferable over tarball snapshots. Integrating the test suite
> with existing automated Linux kernel testing services is
> encouraged."
>
> https://github.com/LinuxSecurityModule/kernel/blob/main/README.md#new-lsm-guidelines
>
Yes we do have a test suite. I will add it in the next version.
-Fan
>> Signed-off-by: Deven Bowers <[email protected]>
>> Signed-off-by: Fan Wu <[email protected]>
>> ---
>> v1-v6:
>> + Not present
>>
>> v7:
>> Introduced
>>
>> v8:
>> + Remove the kunit tests with respect to the fsverity digest, as these
>> require significant changes to work with the new method of acquiring
>> the digest at runtime.
>>
>> v9:
>> + Remove the kunit tests related to ipe_context
>>
>> v10:
>> + No changes
>>
>> v11:
>> + No changes
>> ---
>> security/ipe/Kconfig | 17 +++
>> security/ipe/Makefile | 3 +
>> security/ipe/policy_tests.c | 294 ++++++++++++++++++++++++++++++++++++
>> 3 files changed, 314 insertions(+)
>> create mode 100644 security/ipe/policy_tests.c
>
> --
> paul-moore.com
On Thu, Nov 2, 2023 at 6:46 PM Fan Wu <[email protected]> wrote:
> On 10/26/2023 3:12 PM, Paul Moore wrote:
> > On Thu, Oct 26, 2023 at 5:33 PM Fan Wu <[email protected]> wrote:
> >> On 10/23/2023 8:52 PM, Paul Moore wrote:
> >>> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> >>>>
> >>>> IPE is designed to provide system level trust guarantees, this usually
> >>>> implies that trust starts from bootup with a hardware root of trust,
> >>>> which validates the bootloader. After this, the bootloader verifies the
> >>>> kernel and the initramfs.
> >>>>
> >>>> As there's no currently supported integrity method for initramfs, and
> >>>> it's typically already verified by the bootloader, introduce a property
> >>>> that causes the first superblock to have an execution to be "pinned",
> >>>> which is typically initramfs.
> >>>>
> >>>> When the "pinned" device is unmounted, it will be "unpinned" and
> >>>> `boot_verified` property will always evaluate to false afterward.
> >>>>
> >>>> We use a pointer with a spin_lock to "pin" the device instead of rcu
> >>>> because rcu synchronization may sleep, which is not allowed when
> >>>> unmounting a device.
> >>>>
> >>>> Signed-off-by: Deven Bowers <[email protected]>
> >>>> Signed-off-by: Fan Wu <[email protected]>
> >> ...
> >>>> ---
> >>>> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
> >>>> security/ipe/eval.h | 2 +
> >>>> security/ipe/hooks.c | 12 ++++++
> >>>> security/ipe/hooks.h | 2 +
> >>>> security/ipe/ipe.c | 1 +
> >>>> security/ipe/policy.h | 2 +
> >>>> security/ipe/policy_parser.c | 35 +++++++++++++++++-
> >>>> 7 files changed, 124 insertions(+), 2 deletions(-)
...
> >>>> +/**
> >>>> + * from_pinned - Determine whether @sb is the pinned super_block.
> >>>> + * @sb: Supplies a super_block to check against the pinned super_block.
> >>>> + *
> >>>> + * Return:
> >>>> + * * true - @sb is the pinned super_block
> >>>> + * * false - @sb is not the pinned super_block
> >>>> + */
> >>>> +static bool from_pinned(const struct super_block *sb)
> >>>> +{
> >>>> + bool rv;
> >>>> +
> >>>> + if (!sb)
> >>>> + return false;
> >>>> + spin_lock(&pin_lock);
> >>>> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
> >>>> + spin_unlock(&pin_lock);
> >>>
> >>> It's okay for an initial version, but I still think you need to get
> >>> away from this spinlock in from_pinned() as quickly as possible.
> >>> Maybe I'm wrong, but this looks like a major source of lock contention.
> >>>
> >>> I understand the issue around RCU and the potential for matching on
> >>> a reused buffer/address, but if you modified IPE to have its own LSM
> >>> security blob in super_block::security you could mark the superblock
> >>> when it was mounted and do a lockless lookup here in from_pinned().
> >>
> >> Thank you for the suggestion. After some testing, I discovered that
> >> switching to RCU to pin the super block and using a security blob to
> >> mark a pinned super block works. This approach do avoid many spinlock
> >> operations. I'll incorporate these changes in the next version of the patch.
> >
> > I probably wasn't as clear as I should have been, I was thinking of
> > doing away with the @pinned_sb global variable entirely, as well as
> > its associated lock problems and simply marking the initramfs/initrd
> > superblock when it was mounted. I will admit that I haven't fully
> > thought about all the implementation details, but I think you could
> > leverage the security_sb_mount() hook to set a flag in IPE's
> > superblock metadata when the initramfs was mounted.
>
> I wasn't able to find a way to let LSM pin initramfs/initrd during mount
> time ...
I haven't had to look at the kernel init code in a while, and I don't
recall ever looking at the initramfs code, but I spent some time
digging through the code and I wonder if it would be possible to mark
the initramfs superblock in wait_for_initramfs() via a new LSM hook
using @current->fs->root.mnt->mnt_sb? Although I'm not completely
sure that it's populated. Have you already looked at an approach like
this?
> But I think we could replace the global variable with a flag
> variable ipe_sb_state so we could use atomic operation to only mark one
> drive as pinned without any lock. The code will be like:
>
> static void pin_sb(const struct super_block *sb)
> {
> if (!sb)
> return;
>
> if (!test_and_set_bit_lock(IPE_SB_PINNED, &ipe_sb_state)) {
> ipe_sb(sb)->pinned = true;
> }
> }
>
> Would this sound better?
>
> -Fan
--
paul-moore.com
On Fri, Nov 3, 2023 at 6:15 PM Paul Moore <[email protected]> wrote:
> On Thu, Nov 2, 2023 at 6:46 PM Fan Wu <[email protected]> wrote:
> > On 10/26/2023 3:12 PM, Paul Moore wrote:
> > > On Thu, Oct 26, 2023 at 5:33 PM Fan Wu <[email protected]> wrote:
> > >> On 10/23/2023 8:52 PM, Paul Moore wrote:
> > >>> On Oct 4, 2023 Fan Wu <[email protected]> wrote:
> > >>>>
> > >>>> IPE is designed to provide system level trust guarantees, this usually
> > >>>> implies that trust starts from bootup with a hardware root of trust,
> > >>>> which validates the bootloader. After this, the bootloader verifies the
> > >>>> kernel and the initramfs.
> > >>>>
> > >>>> As there's no currently supported integrity method for initramfs, and
> > >>>> it's typically already verified by the bootloader, introduce a property
> > >>>> that causes the first superblock to have an execution to be "pinned",
> > >>>> which is typically initramfs.
> > >>>>
> > >>>> When the "pinned" device is unmounted, it will be "unpinned" and
> > >>>> `boot_verified` property will always evaluate to false afterward.
> > >>>>
> > >>>> We use a pointer with a spin_lock to "pin" the device instead of rcu
> > >>>> because rcu synchronization may sleep, which is not allowed when
> > >>>> unmounting a device.
> > >>>>
> > >>>> Signed-off-by: Deven Bowers <[email protected]>
> > >>>> Signed-off-by: Fan Wu <[email protected]>
> > >> ...
> > >>>> ---
> > >>>> security/ipe/eval.c | 72 +++++++++++++++++++++++++++++++++++-
> > >>>> security/ipe/eval.h | 2 +
> > >>>> security/ipe/hooks.c | 12 ++++++
> > >>>> security/ipe/hooks.h | 2 +
> > >>>> security/ipe/ipe.c | 1 +
> > >>>> security/ipe/policy.h | 2 +
> > >>>> security/ipe/policy_parser.c | 35 +++++++++++++++++-
> > >>>> 7 files changed, 124 insertions(+), 2 deletions(-)
>
> ...
>
> > >>>> +/**
> > >>>> + * from_pinned - Determine whether @sb is the pinned super_block.
> > >>>> + * @sb: Supplies a super_block to check against the pinned super_block.
> > >>>> + *
> > >>>> + * Return:
> > >>>> + * * true - @sb is the pinned super_block
> > >>>> + * * false - @sb is not the pinned super_block
> > >>>> + */
> > >>>> +static bool from_pinned(const struct super_block *sb)
> > >>>> +{
> > >>>> + bool rv;
> > >>>> +
> > >>>> + if (!sb)
> > >>>> + return false;
> > >>>> + spin_lock(&pin_lock);
> > >>>> + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == sb;
> > >>>> + spin_unlock(&pin_lock);
> > >>>
> > >>> It's okay for an initial version, but I still think you need to get
> > >>> away from this spinlock in from_pinned() as quickly as possible.
> > >>> Maybe I'm wrong, but this looks like a major source of lock contention.
> > >>>
> > >>> I understand the issue around RCU and the potential for matching on
> > >>> a reused buffer/address, but if you modified IPE to have its own LSM
> > >>> security blob in super_block::security you could mark the superblock
> > >>> when it was mounted and do a lockless lookup here in from_pinned().
> > >>
> > >> Thank you for the suggestion. After some testing, I discovered that
> > >> switching to RCU to pin the super block and using a security blob to
> > >> mark a pinned super block works. This approach do avoid many spinlock
> > >> operations. I'll incorporate these changes in the next version of the patch.
> > >
> > > I probably wasn't as clear as I should have been, I was thinking of
> > > doing away with the @pinned_sb global variable entirely, as well as
> > > its associated lock problems and simply marking the initramfs/initrd
> > > superblock when it was mounted. I will admit that I haven't fully
> > > thought about all the implementation details, but I think you could
> > > leverage the security_sb_mount() hook to set a flag in IPE's
> > > superblock metadata when the initramfs was mounted.
> >
> > I wasn't able to find a way to let LSM pin initramfs/initrd during mount
> > time ...
>
> I haven't had to look at the kernel init code in a while, and I don't
> recall ever looking at the initramfs code, but I spent some time
> digging through the code and I wonder if it would be possible to mark
> the initramfs superblock in wait_for_initramfs() via a new LSM hook
> using @current->fs->root.mnt->mnt_sb? Although I'm not completely
> sure that it's populated. Have you already looked at an approach like
> this?
Thinking about this more, the current IPE approach of treating the
first file access as being present in the initramfs is not correct
(one could build a system without an initramfs). I think we need to
do something like the above where the initramfs is explicitly marked
in the initramfs code.
> > But I think we could replace the global variable with a flag
> > variable ipe_sb_state so we could use atomic operation to only mark one
> > drive as pinned without any lock. The code will be like:
> >
> > static void pin_sb(const struct super_block *sb)
> > {
> > if (!sb)
> > return;
> >
> > if (!test_and_set_bit_lock(IPE_SB_PINNED, &ipe_sb_state)) {
> > ipe_sb(sb)->pinned = true;
> > }
> > }
> >
> > Would this sound better?
--
paul-moore.com