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 initramfs:
policy_name=Allow_All_Initramfs policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
Allow any signed dm-verity volume and the initramfs:
policy_name=AllowSignedAndInitramfs 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 initramfs:
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_BLK_DEV_INITRD=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.
In addition, IPE has a python based integration
test suite https://github.com/microsoft/ipe/tree/test-suite that
can test both user interfaces and enforcement functionalities.
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]/
v11: https://lore.kernel.org/lkml/[email protected]/
v12: https://lore.kernel.org/lkml/[email protected]/
v13: https://lore.kernel.org/lkml/[email protected]/
v14: 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
v12:
* Address locking issues
* Change the implementation of boot_verified to trust initramfs only
* Update audit format for IPE decision events
* Refactor code for lsm_id
* Add IPE test suite link
v13:
* Rename the new security hook in initramfs
* Make the policy grammar independent of kernel config
* Correct IPE audit format
* Refactor policy update code
v14:
* Add more code comments/docs for dmverity/fsverity
* Fix incorrect code usage and format in dmverity
* Drop one accepted commit of dmverity
v15:
* Fix grammar issues
* Add more documentation to fsverity
* Switch security hooks from *_setsecurity() to *_setintegrity()
* Cleanup unnecessary headers
Deven Bowers (13):
security: add ipe lsm
ipe: add policy parser
ipe: add evaluation loop
ipe: add LSM hooks on execution and kernel read
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 (8):
initramfs|security: Add a security hook to do_populate_rootfs()
ipe: introduce 'boot_verified' as a trust provider
security: add new securityfs delete function
security: add security_bdev_setintegrity() hook
dm: add finalize hook to target_type
security: add security_inode_setintegrity() hook
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 | 774 ++++++++++++++++++
.../admin-guide/kernel-parameters.txt | 12 +
Documentation/filesystems/fsverity.rst | 13 +-
Documentation/security/index.rst | 1 +
Documentation/security/ipe.rst | 444 ++++++++++
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 | 24 +-
fs/verity/signature.c | 5 +-
include/linux/blk_types.h | 3 +
include/linux/device-mapper.h | 9 +
include/linux/dm-verity.h | 12 +
include/linux/lsm_hook_defs.h | 11 +
include/linux/lsm_hooks.h | 1 +
include/linux/security.h | 48 ++
include/uapi/linux/audit.h | 3 +
include/uapi/linux/lsm.h | 1 +
init/initramfs.c | 3 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 2 +
scripts/ipe/polgen/Makefile | 5 +
scripts/ipe/polgen/polgen.c | 145 ++++
security/Kconfig | 11 +-
security/Makefile | 1 +
security/inode.c | 25 +
security/ipe/.gitignore | 2 +
security/ipe/Kconfig | 75 ++
security/ipe/Makefile | 31 +
security/ipe/audit.c | 279 +++++++
security/ipe/audit.h | 19 +
security/ipe/digest.c | 120 +++
security/ipe/digest.h | 26 +
security/ipe/eval.c | 375 +++++++++
security/ipe/eval.h | 64 ++
security/ipe/fs.c | 247 ++++++
security/ipe/fs.h | 16 +
security/ipe/hooks.c | 284 +++++++
security/ipe/hooks.h | 52 ++
security/ipe/ipe.c | 98 +++
security/ipe/ipe.h | 26 +
security/ipe/policy.c | 229 ++++++
security/ipe/policy.h | 98 +++
security/ipe/policy_fs.c | 468 +++++++++++
security/ipe/policy_parser.c | 548 +++++++++++++
security/ipe/policy_parser.h | 11 +
security/ipe/policy_tests.c | 294 +++++++
security/security.c | 138 +++-
.../selftests/lsm/lsm_list_modules_test.c | 3 +
54 files changed, 5159 insertions(+), 11 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
--
2.44.0
This patch introduces a new hook to notify security system that the
content of initramfs has been unpacked into the rootfs.
Upon receiving this notification, the security system can activate
a policy to allow only files that originated from the initramfs to
execute or load into kernel during the early stages of booting.
This approach is crucial for minimizing the attack surface by
ensuring that only trusted files from the initramfs are operational
in the critical boot phase.
Signed-off-by: Fan Wu <[email protected]>
---
v1-v11:
+ Not present
v12:
+ Introduced
v13:
+ Rename the hook name to initramfs_populated()
v14:
+ No changes
v15:
+ No changes
---
include/linux/lsm_hook_defs.h | 2 ++
include/linux/security.h | 8 ++++++++
init/initramfs.c | 3 +++
security/security.c | 10 ++++++++++
4 files changed, 23 insertions(+)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 334e00efbde4..7db99ae75651 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -450,3 +450,5 @@ 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(void, LSM_RET_VOID, initramfs_populated, void)
diff --git a/include/linux/security.h b/include/linux/security.h
index 41a8f667bdfa..14fff542f2e3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2255,4 +2255,12 @@ static inline int security_uring_cmd(struct io_uring_cmd *ioucmd)
#endif /* CONFIG_SECURITY */
#endif /* CONFIG_IO_URING */
+#ifdef CONFIG_SECURITY
+extern void security_initramfs_populated(void);
+#else
+static inline void security_initramfs_populated(void)
+{
+}
+#endif /* CONFIG_SECURITY */
+
#endif /* ! __LINUX_SECURITY_H */
diff --git a/init/initramfs.c b/init/initramfs.c
index da79760b8be3..cc9115117896 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -17,6 +17,7 @@
#include <linux/namei.h>
#include <linux/init_syscalls.h>
#include <linux/umh.h>
+#include <linux/security.h>
#include "do_mounts.h"
@@ -719,6 +720,8 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie)
#endif
}
+ security_initramfs_populated();
+
done:
/*
* If the initrd region is overlapped with crashkernel reserved region,
diff --git a/security/security.c b/security/security.c
index 287bfac6b471..b10230c51c0b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5675,3 +5675,13 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
return call_int_hook(uring_cmd, ioucmd);
}
#endif /* CONFIG_IO_URING */
+
+/**
+ * security_initramfs_populated() - Notify LSMs that initramfs has been loaded
+ *
+ * Tells the LSMs the initramfs has been unpacked into the rootfs.
+ */
+void security_initramfs_populated(void)
+{
+ call_void_hook(initramfs_populated);
+}
--
2.44.0
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. This patch introduces
a new IPE property `boot_verified` which allows author of IPE policy to
indicate trust for files from initramfs.
The implementation of this feature utilizes the newly added
`initramfs_populated` hook. This hook marks the superblock of the rootfs
after the initramfs has been unpacked into it.
Before mounting the real rootfs on top of the initramfs, initramfs
script will recursively remove all files and directories on the
initramfs. This is typically implemented by using switch_root(8)
(https://man7.org/linux/man-pages/man8/switch_root.8.html).
Therefore the initramfs will be empty and not accessible after the real
rootfs takes over. It is advised to switch to a different policy
that doesn't rely on the `boot_verified` property after this point.
This ensures that the trust policies remain relevant and effective
throughout the system's operation.
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
v12:
+ Switch to use unpack_initramfs hook and security blob
v13:
+ Update the hook name
+ Rename the security blob field to initramfs
+ Remove the dependency on CONFIG_BLK_DEV_INITRD
v14:
+ No changes
v15:
+ No changes
---
security/ipe/eval.c | 37 +++++++++++++++++++++++++++++++++++-
security/ipe/eval.h | 5 +++++
security/ipe/hooks.c | 6 ++++++
security/ipe/hooks.h | 2 ++
security/ipe/ipe.c | 8 ++++++++
security/ipe/ipe.h | 1 +
security/ipe/policy.h | 2 ++
security/ipe/policy_parser.c | 35 +++++++++++++++++++++++++++++++++-
8 files changed, 94 insertions(+), 2 deletions(-)
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 4f425afffcad..bef204decbbf 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -16,6 +16,18 @@
struct ipe_policy __rcu *ipe_active_policy;
+#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
+
+/**
+ * build_ipe_sb_ctx - Build initramfs field of an evaluation context.
+ * @ctx: Supplies a pointer to the context to be populated.
+ * @file: Supplies the file struct of the file triggered IPE event.
+ */
+static void build_ipe_sb_ctx(struct ipe_eval_ctx *ctx, const struct file *const file)
+{
+ ctx->initramfs = ipe_sb(FILE_SUPERBLOCK(file))->initramfs;
+}
+
/**
* build_eval_ctx - Build an evaluation context.
* @ctx: Supplies a pointer to the context to be populated.
@@ -28,6 +40,22 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
{
ctx->file = file;
ctx->op = op;
+
+ if (file)
+ build_ipe_sb_ctx(ctx, file);
+}
+
+/**
+ * evaluate_boot_verified - Evaluate @ctx for the boot verified property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_boot_verified(const struct ipe_eval_ctx *const ctx)
+{
+ return ctx->initramfs;
}
/**
@@ -42,7 +70,14 @@ 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 !evaluate_boot_verified(ctx);
+ case IPE_PROP_BOOT_VERIFIED_TRUE:
+ return evaluate_boot_verified(ctx);
+ default:
+ return false;
+ }
}
/**
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index cfdf3c8dfe8a..884821494525 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -15,10 +15,15 @@
extern struct ipe_policy __rcu *ipe_active_policy;
+struct ipe_superblock {
+ bool initramfs;
+};
+
struct ipe_eval_ctx {
enum ipe_op_type op;
const struct file *file;
+ bool initramfs;
};
void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index 3aec88c074e1..23cf070438fa 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -4,6 +4,7 @@
*/
#include <linux/fs.h>
+#include <linux/fs_struct.h>
#include <linux/types.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
@@ -181,3 +182,8 @@ int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents)
build_eval_ctx(&ctx, NULL, op);
return ipe_evaluate_event(&ctx);
}
+
+void ipe_unpack_initramfs(void)
+{
+ ipe_sb(current->fs->root.mnt->mnt_sb)->initramfs = true;
+}
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 23205452f758..21f49cdc2fcd 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_unpack_initramfs(void);
+
#endif /* _IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 22bd95116087..3bf7c1331d5e 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -5,9 +5,11 @@
#include <uapi/linux/lsm.h>
#include "ipe.h"
+#include "eval.h"
#include "hooks.h"
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
+ .lbs_superblock = sizeof(struct ipe_superblock),
};
static const struct lsm_id ipe_lsmid = {
@@ -15,12 +17,18 @@ static const struct lsm_id ipe_lsmid = {
.id = LSM_ID_IPE,
};
+struct ipe_superblock *ipe_sb(const struct super_block *sb)
+{
+ return sb->s_security + ipe_blobs.lbs_superblock;
+}
+
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),
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(initramfs_populated, ipe_unpack_initramfs),
};
/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index a1c68d0fc2e0..fb8f0ad168b3 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -12,5 +12,6 @@
#define pr_fmt(fmt) "IPE: " fmt
#include <linux/lsm_hooks.h>
+struct ipe_superblock *ipe_sb(const struct super_block *sb);
#endif /* _IPE_H */
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index fb906f41522b..fb48024bb63e 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 612839b405f4..3fc8fea55b95 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;
}
/**
--
2.44.0
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 intended 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
v12:
+ No changes
v13:
+ No changes
v14:
+ No changes
v15:
+ No changes
---
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 14fff542f2e3..f35af7b6cfba 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2089,6 +2089,7 @@ 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 9e7cde913667..f21847badb7d 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,
--
2.44.0
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 security subsystem to easily
access that information. Worse, in the current implementation 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 certificate.
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
v12:
+ No changes
v13:
+ No changes
v14:
+ No changes
v15:
+ Drop security_bdev_setsecurity() for new hook
security_bdev_setintegrity() in the next commit
+ Update call_int_hook() for 260017f
---
block/bdev.c | 7 ++++
include/linux/blk_types.h | 3 ++
include/linux/lsm_hook_defs.h | 4 ++
include/linux/lsm_hooks.h | 1 +
include/linux/security.h | 12 ++++++
security/security.c | 69 +++++++++++++++++++++++++++++++++++
6 files changed, 96 insertions(+)
diff --git a/block/bdev.c b/block/bdev.c
index e7adaaf1c219..5a9f94219273 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>
@@ -313,6 +314,11 @@ 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;
}
@@ -322,6 +328,7 @@ 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 cb1526ec44b5..effe3c4e6b35 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -70,6 +70,9 @@ struct block_device {
#endif
bool bd_ro_warned;
int bd_writers;
+#ifdef CONFIG_SECURITY
+ void *security;
+#endif
/*
* keep this out-of-line as it's both big and not needed in the fast
* path
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 7db99ae75651..c335404470dc 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -452,3 +452,7 @@ LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
#endif /* CONFIG_IO_URING */
LSM_HOOK(void, LSM_RET_VOID, initramfs_populated, void)
+
+LSM_HOOK(int, 0, bdev_alloc_security, struct block_device *bdev)
+LSM_HOOK(void, LSM_RET_VOID, bdev_free_security, struct block_device *bdev)
+
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index a2ade0ffe9e7..f1692179aa56 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -78,6 +78,7 @@ 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 f35af7b6cfba..9965b5c50df4 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -509,6 +509,8 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
int security_locked_down(enum lockdown_reason what);
int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len,
void *val, size_t val_len, u64 id, u64 flags);
+int security_bdev_alloc(struct block_device *bdev);
+void security_bdev_free(struct block_device *bdev);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1483,6 +1485,16 @@ static inline int lsm_fill_user_ctx(struct lsm_ctx __user *uctx,
{
return -EOPNOTSUPP;
}
+
+static inline int security_bdev_alloc(struct block_device *bdev)
+{
+ return 0;
+}
+
+static inline void security_bdev_free(struct block_device *bdev)
+{
+}
+
#endif /* CONFIG_SECURITY */
#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
diff --git a/security/security.c b/security/security.c
index b10230c51c0b..4274bbee40d0 100644
--- a/security/security.c
+++ b/security/security.c
@@ -29,6 +29,7 @@
#include <linux/msg.h>
#include <linux/overflow.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)
@@ -232,6 +233,7 @@ 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. */
@@ -405,6 +407,7 @@ 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
@@ -737,6 +740,28 @@ 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
@@ -5568,6 +5593,50 @@ 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, 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);
+
#ifdef CONFIG_PERF_EVENTS
/**
* security_perf_event_open() - Check if a perf event open is allowed
--
2.44.0
This patch introduces a new hook to save block device's integrity
data. For example, for dm-verity, LSMs can use this hook to save
the roothash signature of a dm-verity into the security blob,
and LSMs can make access decisions based on the data inside
the signature, like the signer certificate.
Signed-off-by: Fan Wu <[email protected]>
--
v1-v14:
+ Not present
v15:
+ Introduced
---
include/linux/lsm_hook_defs.h | 2 ++
include/linux/security.h | 14 ++++++++++++++
security/security.c | 28 ++++++++++++++++++++++++++++
3 files changed, 44 insertions(+)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index c335404470dc..6808ae763913 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -455,4 +455,6 @@ LSM_HOOK(void, LSM_RET_VOID, initramfs_populated, void)
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_setintegrity, struct block_device *bdev,
+ enum lsm_intgr_type type, const void *value, size_t size)
diff --git a/include/linux/security.h b/include/linux/security.h
index 9965b5c50df4..eaff8868766a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -83,6 +83,10 @@ enum lsm_event {
LSM_POLICY_CHANGE,
};
+enum lsm_intgr_type {
+ __LSM_INTGR_MAX
+};
+
/*
* These are reasons that can be passed to the security_locked_down()
* LSM hook. Lockdown reasons that protect kernel integrity (ie, the
@@ -511,6 +515,9 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len,
void *val, size_t val_len, u64 id, u64 flags);
int security_bdev_alloc(struct block_device *bdev);
void security_bdev_free(struct block_device *bdev);
+int security_bdev_setintegrity(struct block_device *bdev,
+ enum lsm_intgr_type type, const void *value,
+ size_t size);
#else /* CONFIG_SECURITY */
static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -1495,6 +1502,13 @@ static inline void security_bdev_free(struct block_device *bdev)
{
}
+static inline int security_bdev_setintegrity(struct block_device *bdev,
+ enum lsm_intgr_type, type,
+ 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 4274bbee40d0..8d88529ac904 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5637,6 +5637,34 @@ void security_bdev_free(struct block_device *bdev)
}
EXPORT_SYMBOL(security_bdev_free);
+/**
+ * security_bdev_setintegrity() - Set the bdev's integrity data
+ * @bdev: block device
+ * @type: type of integrity, e.g. hash digest, signature, etc
+ * @value: the integrity value
+ * @size: size of the integrity value
+ *
+ * Register a verified integrity measurement of a bdev with the LSM.
+ *
+ * Return: Returns 0 on success, negative values on failure.
+ */
+int security_bdev_setintegrity(struct block_device *bdev,
+ enum lsm_intgr_type type, const void *value,
+ size_t size)
+{
+ int rc = 0;
+ struct security_hook_list *p;
+
+ hlist_for_each_entry(p, &security_hook_heads.bdev_setintegrity, list) {
+ rc = p->hook.bdev_setintegrity(bdev, type, value, size);
+ if (rc)
+ return rc;
+ }
+
+ return LSM_RET_DEFAULT(bdev_setintegrity);
+}
+EXPORT_SYMBOL(security_bdev_setintegrity);
+
#ifdef CONFIG_PERF_EVENTS
/**
* security_perf_event_open() - Check if a perf event open is allowed
--
2.44.0
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 adds two security hook calls in dm-verity to save the
dm-verity roothash and the roothash signature to the block device's
LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
which will be introduced in the next commit.
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
v12:
+ No changes
v13:
+ No changes
v14:
+ Correct code format
+ Remove unnecessary header and switch to dm_disk()
v15:
+ Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
+ Remove unnecessary headers
---
drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
drivers/md/dm-verity.h | 6 +++
include/linux/dm-verity.h | 12 ++++++
include/linux/security.h | 2 +
4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -22,6 +22,8 @@
#include <linux/scatterlist.h>
#include <linux/string.h>
#include <linux/jump_label.h>
+#include <linux/security.h>
+#include <linux/dm-verity.h>
#define DM_MSG_PREFIX "verity"
@@ -1017,6 +1019,38 @@ 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 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;
+}
+
+static void verity_free_sig(struct dm_verity *v)
+{
+ kfree(v->root_digest_sig);
+}
+
+#else
+
+static inline int verity_init_sig(struct dm_verity *v, const void *sig,
+ size_t sig_size)
+{
+ return 0;
+}
+
+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;
@@ -1035,6 +1069,7 @@ 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);
@@ -1434,6 +1469,13 @@ 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);
@@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
+ root_digest.digest = v->root_digest;
+ root_digest.digest_len = v->digest_size;
+ root_digest.alg = v->alg_name;
+
+ r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
+ sizeof(root_digest));
+ if (r)
+ return r;
+
+ return security_bdev_setintegrity(bdev,
+ LSM_INTGR_DMV_SIG,
+ 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,
@@ -1596,6 +1666,9 @@ 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 20b1bcf03474..6a5b8df5bafd 100644
--- a/drivers/md/dm-verity.h
+++ b/drivers/md/dm-verity.h
@@ -43,6 +43,9 @@ 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 */
@@ -56,6 +59,9 @@ struct dm_verity {
bool hash_failed:1; /* set if hash of any block failed */
bool use_bh_wq:1; /* try to verify in BH wq before normal 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..a799a8043d85
--- /dev/null
+++ b/include/linux/dm-verity.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_DM_VERITY_H
+#define _LINUX_DM_VERITY_H
+
+struct dm_verity_digest {
+ const char *alg;
+ const u8 *digest;
+ size_t digest_len;
+};
+
+#endif /* _LINUX_DM_VERITY_H */
diff --git a/include/linux/security.h b/include/linux/security.h
index eaff8868766a..60b40b523d57 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -84,6 +84,8 @@ enum lsm_event {
};
enum lsm_intgr_type {
+ LSM_INTGR_DMV_SIG,
+ LSM_INTGR_DMV_ROOTHASH,
__LSM_INTGR_MAX
};
--
2.44.0
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
v12:
+ Remove redundant code
v13:
+ Remove audit format macro
v14:
+ No changes
v15:
+ No changes
---
security/ipe/audit.c | 27 ++++++++++++++++--
security/ipe/audit.h | 1 +
security/ipe/eval.c | 11 +++++--
security/ipe/eval.h | 1 +
security/ipe/fs.c | 68 ++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 104 insertions(+), 4 deletions(-)
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index f167fdc87986..a480f27278df 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -93,8 +93,8 @@ void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
if (!ab)
return;
- audit_log_format(ab, "ipe_op=%s ipe_hook=%s pid=%d comm=",
- op, audit_hook_names[ctx->hook],
+ audit_log_format(ab, "ipe_op=%s ipe_hook=%s enforcing=%d pid=%d comm=",
+ op, audit_hook_names[ctx->hook], READ_ONCE(enforce),
task_tgid_nr(current));
audit_log_untrustedstring(ab, get_task_comm(comm, current));
@@ -212,3 +212,26 @@ 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(audit_context(), GFP_KERNEL, AUDIT_MAC_STATUS,
+ "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 274f7346ef42..3f3125478dd0 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -18,6 +18,7 @@
struct ipe_policy __rcu *ipe_active_policy;
bool success_audit;
+bool enforce = true;
#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
@@ -106,6 +107,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
const struct ipe_rule *rule = NULL;
const struct ipe_op_table *rules = NULL;
struct ipe_prop *prop = NULL;
+ int rc = 0;
rcu_read_lock();
@@ -158,9 +160,12 @@ 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;
- return 0;
+ if (!READ_ONCE(enforce))
+ rc = 0;
+
+ return rc;
}
/* Set the right module name */
@@ -171,3 +176,5 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
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 4631b236358e..0b50302611a4 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -16,6 +16,7 @@
extern struct ipe_policy __rcu *ipe_active_policy;
extern bool success_audit;
+extern bool enforce;
struct ipe_superblock {
bool initramfs;
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index 95407997cf0c..b16d87443a3b 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;
--
2.44.0
This patch introduces a new hook to save inode's integrity
data. For example, for fsverity enabled files, LSMs can use this hook to save
the verified fsverity builtin signature into the inode's security blob,
and LSMs can make access decisions based on the data inside the signature,
like the signer certificate.
Signed-off-by: Fan Wu <[email protected]>
--
v1-v14:
+ Not present
v15:
+ Introduced
---
include/linux/lsm_hook_defs.h | 3 +++
include/linux/security.h | 10 ++++++++++
security/security.c | 28 ++++++++++++++++++++++++++++
3 files changed, 41 insertions(+)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 6808ae763913..c88587fc3691 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -177,6 +177,9 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)
+LSM_HOOK(int, 0, inode_setintegrity, struct inode *inode,
+ enum lsm_intgr_type type, const void *value, size_t size)
+
LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
struct kernfs_node *kn)
LSM_HOOK(int, 0, file_permission, struct file *file, int mask)
diff --git a/include/linux/security.h b/include/linux/security.h
index 60b40b523d57..0885866b261e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -405,6 +405,9 @@ int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer
void security_inode_getsecid(struct inode *inode, u32 *secid);
int security_inode_copy_up(struct dentry *src, struct cred **new);
int security_inode_copy_up_xattr(const char *name);
+int security_inode_setintegrity(struct inode *inode,
+ enum lsm_intgr_type type, const void *value,
+ size_t size);
int security_kernfs_init_security(struct kernfs_node *kn_dir,
struct kernfs_node *kn);
int security_file_permission(struct file *file, int mask);
@@ -1021,6 +1024,13 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new)
return 0;
}
+static inline int security_inode_setintegrity(struct inode *inode,
+ enum lsm_intgr_type, type,
+ const void *value, size_t size)
+{
+ return 0;
+}
+
static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
struct kernfs_node *kn)
{
diff --git a/security/security.c b/security/security.c
index 8d88529ac904..c5d426d084ab 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2681,6 +2681,34 @@ int security_inode_copy_up_xattr(const char *name)
}
EXPORT_SYMBOL(security_inode_copy_up_xattr);
+/**
+ * security_inode_setintegrity() - Set the inode's integrity data
+ * @inode: inode
+ * @type: type of integrity, e.g. hash digest, signature, etc
+ * @value: the integrity value
+ * @size: size of the integrity value
+ *
+ * Register a verified integrity measurement of a inode with the LSM.
+ *
+ * Return: Returns 0 on success, negative values on failure.
+ */
+int security_inode_setintegrity(struct inode *inode,
+ enum lsm_intgr_type type, const void *value,
+ size_t size)
+{
+ int rc = 0;
+ struct security_hook_list *p;
+
+ hlist_for_each_entry(p, &security_hook_heads.inode_setintegrity, list) {
+ rc = p->hook.inode_setintegrity(inode, type, value, size);
+ if (rc)
+ return rc;
+ }
+
+ return LSM_RET_DEFAULT(inode_setintegrity);
+}
+EXPORT_SYMBOL(security_inode_setintegrity);
+
/**
* security_kernfs_init_security() - Init LSM context for a kernfs node
* @kn_dir: parent kernfs node
--
2.44.0
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
v12:
+ Refactor to use struct digest_info* instead of void*
+ Correct audit format
v13:
+ Remove the CONFIG_IPE_PROP_DM_VERITY dependency inside the parser
to make the policy grammar independent of the kernel config.
v14:
+ No changes
v15:
+ Fix one grammar issue in KCONFIG
+ Switch to use security_bdev_setintegrity() hook
---
security/ipe/Kconfig | 18 ++++++
security/ipe/Makefile | 1 +
security/ipe/audit.c | 29 ++++++++-
security/ipe/digest.c | 120 +++++++++++++++++++++++++++++++++++
security/ipe/digest.h | 26 ++++++++
security/ipe/eval.c | 91 +++++++++++++++++++++++++-
security/ipe/eval.h | 10 +++
security/ipe/hooks.c | 67 +++++++++++++++++++
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, 412 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..5433ca3fc855 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 evaluate
+ 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 a480f27278df..3acbfecc9f43 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")
@@ -49,8 +50,22 @@ static const char *const audit_hook_names[__IPE_HOOK_MAX] = {
static const char *const audit_prop_names[__IPE_PROP_MAX] = {
"boot_verified=FALSE",
"boot_verified=TRUE",
+ "dmverity_roothash=",
+ "dmverity_signature=FALSE",
+ "dmverity_signature=TRUE",
};
+/**
+ * audit_dmv_roothash - audit the roothash of a dmverity_roothash property.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @rh: Supplies a pointer to the digest structure.
+ */
+static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
+{
+ audit_log_format(ab, "%s", audit_prop_names[IPE_PROP_DMV_ROOTHASH]);
+ ipe_digest_audit(ab, rh);
+}
+
/**
* audit_rule - audit an IPE policy rule approximation.
* @ab: Supplies a pointer to the audit_buffer to append to.
@@ -62,8 +77,18 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
audit_log_format(ab, " rule=\"%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) {
+ switch (ptr->type) {
+ case IPE_PROP_DMV_ROOTHASH:
+ audit_dmv_roothash(ab, ptr->value);
+ break;
+ default:
+ audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
+ break;
+ }
+
+ 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..f6fde0b1fe74
--- /dev/null
+++ b/security/ipe/digest.c
@@ -0,0 +1,120 @@
+// 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.
+ *
+ * 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: The parsed digest_info structure.
+ */
+struct digest_info *ipe_digest_parse(const char *valstr)
+{
+ char *sep, *raw_digest;
+ size_t raw_digest_len;
+ int rc = 0;
+ char *alg = NULL;
+ u8 *digest = NULL;
+ struct digest_info *info = NULL;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return ERR_PTR(-ENOMEM);
+
+ sep = strchr(valstr, ':');
+ if (!sep) {
+ rc = -EBADMSG;
+ goto err;
+ }
+
+ alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
+ if (!alg) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ raw_digest = sep + 1;
+ raw_digest_len = strlen(raw_digest);
+
+ info->digest_len = (raw_digest_len + 1) / 2;
+ digest = kzalloc(info->digest_len, GFP_KERNEL);
+ if (!digest) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ rc = hex2bin(digest, raw_digest, info->digest_len);
+ if (rc < 0) {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ info->alg = alg;
+ info->digest = digest;
+ return info;
+
+err:
+ kfree(alg);
+ kfree(digest);
+ kfree(info);
+ return ERR_PTR(rc);
+}
+
+/**
+ * ipe_digest_eval - evaluate an IPE digest against another digest.
+ * @expected: Supplies the policy-provided digest value.
+ * @digest: Supplies the digest to compare against the policy digest value.
+ *
+ * Return:
+ * * true - digests match
+ * * false - digests do not match
+ */
+bool ipe_digest_eval(const struct digest_info *expected,
+ const struct digest_info *digest)
+{
+ return (expected->digest_len == digest->digest_len) &&
+ (!strcmp(expected->alg, digest->alg)) &&
+ (!memcmp(expected->digest, digest->digest, expected->digest_len));
+}
+
+/**
+ * ipe_digest_free - free an IPE digest.
+ * @info: Supplies a pointer the policy-provided digest to free.
+ */
+void ipe_digest_free(struct digest_info *info)
+{
+ if (IS_ERR_OR_NULL(info))
+ return;
+
+ kfree(info->alg);
+ 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.
+ * @info: 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.
+ */
+void ipe_digest_audit(struct audit_buffer *ab, const struct digest_info *info)
+{
+ audit_log_untrustedstring(ab, info->alg);
+ audit_log_format(ab, ":");
+ audit_log_n_hex(ab, info->digest, info->digest_len);
+}
diff --git a/security/ipe/digest.h b/security/ipe/digest.h
new file mode 100644
index 000000000000..13fa67071805
--- /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 <linux/types.h>
+#include <linux/audit.h>
+
+#include "policy.h"
+
+struct digest_info {
+ const char *alg;
+ const u8 *digest;
+ size_t digest_len;
+};
+
+struct digest_info *ipe_digest_parse(const char *valstr);
+void ipe_digest_free(struct digest_info *digest_info);
+void ipe_digest_audit(struct audit_buffer *ab, const struct digest_info *val);
+bool ipe_digest_eval(const struct digest_info *expected,
+ const struct digest_info *digest);
+
+#endif /* _IPE_DIGEST_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 3f3125478dd0..8dcf7809c9fc 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -15,10 +15,12 @@
#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)
#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
@@ -32,6 +34,23 @@ static void build_ipe_sb_ctx(struct ipe_eval_ctx *ctx, const struct file *const
ctx->initramfs = ipe_sb(FILE_SUPERBLOCK(file))->initramfs;
}
+#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 populated.
+ * @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 populated.
@@ -48,8 +67,10 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
ctx->op = op;
ctx->hook = hook;
- if (file)
+ if (file) {
build_ipe_sb_ctx(ctx, file);
+ build_ipe_bdev_ctx(ctx, d_real_inode(file->f_path.dentry));
+ }
}
/**
@@ -65,6 +86,68 @@ static bool evaluate_boot_verified(const struct ipe_eval_ctx *const ctx)
return ctx->initramfs;
}
+#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 &&
+ !!ctx->ipe_bdev->root_hash &&
+ ipe_digest_eval(p->value,
+ ctx->ipe_bdev->root_hash);
+}
+
+/**
+ * evaluate_dmv_sig_false: Analyze @ctx against a dmv sig false property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the property
+ * * false - The current @ctx doesn't match the property
+ */
+static bool evaluate_dmv_sig_false(const struct ipe_eval_ctx *const ctx)
+{
+ 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.
+ *
+ * Return:
+ * * true - The current @ctx match the property
+ * * false - The current @ctx doesn't match the property
+ */
+static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx)
+{
+ return !evaluate_dmv_sig_false(ctx);
+}
+#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)
+{
+ return false;
+}
+
+static bool evaluate_dmv_sig_true(const struct ipe_eval_ctx *const ctx)
+{
+ return false;
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
/**
* evaluate_property - Analyze @ctx against a property.
* @ctx: Supplies a pointer to the context to be evaluated.
@@ -82,6 +165,12 @@ static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
return !evaluate_boot_verified(ctx);
case IPE_PROP_BOOT_VERIFIED_TRUE:
return evaluate_boot_verified(ctx);
+ case IPE_PROP_DMV_ROOTHASH:
+ return evaluate_dmv_roothash(ctx, p);
+ case IPE_PROP_DMV_SIG_FALSE:
+ return evaluate_dmv_sig_false(ctx);
+ case IPE_PROP_DMV_SIG_TRUE:
+ return evaluate_dmv_sig_true(ctx);
default:
return false;
}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 0b50302611a4..494c0754f512 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -22,12 +22,22 @@ struct ipe_superblock {
bool initramfs;
};
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+struct ipe_bdev {
+ bool dm_verity_signed;
+ struct digest_info *root_hash;
+};
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
struct ipe_eval_ctx {
enum ipe_op_type op;
enum ipe_hook_type hook;
const struct file *file;
bool initramfs;
+#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 6bcc7908ed13..1abddd6e1e7f 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -8,10 +8,14 @@
#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"
#include "eval.h"
+#include "digest.h"
/**
* ipe_bprm_check_security - ipe security hook function for bprm check.
@@ -187,3 +191,66 @@ void ipe_unpack_initramfs(void)
{
ipe_sb(current->fs->root.mnt->mnt_sb)->initramfs = true;
}
+
+#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);
+
+ ipe_digest_free(blob->root_hash);
+}
+
+/**
+ * ipe_bdev_setintegrity - save integrity data from a bdev to IPE's LSM blob.
+ * @bdev: Supplies a pointer to a block_device that contains the LSM blob.
+ * @type: Supplies the integrity type.
+ * @value: Supplies the value to store.
+ * @len: The length of @value.
+ */
+int ipe_bdev_setintegrity(struct block_device *bdev, enum lsm_intgr_type type,
+ const void *value, size_t len)
+{
+ struct ipe_bdev *blob = ipe_bdev(bdev);
+
+ if (type == LSM_INTGR_DMV_ROOTHASH) {
+ const struct dm_verity_digest *digest = value;
+ struct digest_info *info = NULL;
+ u8 *raw_digest = NULL;
+ char *alg = NULL;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ raw_digest = kmemdup(digest->digest, digest->digest_len,
+ GFP_KERNEL);
+ if (!raw_digest)
+ goto err;
+
+ alg = kstrdup(digest->alg, GFP_KERNEL);
+ if (!alg)
+ goto err;
+
+ info->alg = alg;
+ info->digest = raw_digest;
+ info->digest_len = digest->digest_len;
+ blob->root_hash = info;
+ return 0;
+err:
+ kfree(info);
+ kfree(raw_digest);
+ kfree(alg);
+ return -ENOMEM;
+ } else if (type == LSM_INTGR_DMV_SIG) {
+ blob->dm_verity_signed = true;
+ return 0;
+ }
+
+ return 0;
+}
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index b92c1d78e253..6b735aac4028 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>
enum ipe_hook_type {
IPE_HOOK_BPRM_CHECK = 0,
@@ -35,4 +36,11 @@ int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents);
void ipe_unpack_initramfs(void);
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+void ipe_bdev_free_security(struct block_device *bdev);
+
+int ipe_bdev_setintegrity(struct block_device *bdev, enum lsm_intgr_type type,
+ 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 53820ca6d5b7..3d63e9672f12 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -7,11 +7,15 @@
#include "ipe.h"
#include "eval.h"
#include "hooks.h"
+#include "eval.h"
bool ipe_enabled;
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
.lbs_superblock = sizeof(struct ipe_superblock),
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ .lbs_bdev = sizeof(struct ipe_bdev),
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
static const struct lsm_id ipe_lsmid = {
@@ -24,6 +28,13 @@ struct ipe_superblock *ipe_sb(const struct super_block *sb)
return sb->s_security + ipe_blobs.lbs_superblock;
}
+#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),
@@ -31,6 +42,10 @@ 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(initramfs_populated, ipe_unpack_initramfs),
+#ifdef CONFIG_IPE_PROP_DM_VERITY
+ LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
+ LSM_HOOK_INIT(bdev_setintegrity, ipe_bdev_setintegrity),
+#endif /* CONFIG_IPE_PROP_DM_VERITY */
};
/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index 86c2b8394d93..64626702b689 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -16,4 +16,8 @@ struct ipe_superblock *ipe_sb(const struct super_block *sb);
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 dba5e71e089e..35629e9699f7 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 3fc8fea55b95..802e31f14b22 100644
--- a/security/ipe/policy_parser.c
+++ b/security/ipe/policy_parser.c
@@ -11,6 +11,7 @@
#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 +270,9 @@ 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"},
+ {IPE_PROP_DMV_ROOTHASH, "dmverity_roothash=%s"},
+ {IPE_PROP_DMV_SIG_FALSE, "dmverity_signature=FALSE"},
+ {IPE_PROP_DMV_SIG_TRUE, "dmverity_signature=TRUE"},
{IPE_PROP_INVALID, NULL}
};
@@ -287,6 +292,7 @@ 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 +301,22 @@ 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;
+ }
+ p->value = ipe_digest_parse(dup);
+ if (IS_ERR(p->value)) {
+ rc = PTR_ERR(p->value);
+ 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;
}
/**
--
2.44.0
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.
This patch introduces a new security_inode_setintegrity() hook call in
fsverity to store the verified fsverity signature in the inode's LSM blobs.
The hook call is executed after fsverity_verify_signature(), ensuring that
the signature is verified against fsverity's keyring.
The last commit in this patch set will add a link to the IPE documentation in
fsverity.rst.
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
v12:
+ Add constification to the hook call
v13:
+ No changes
v14:
+ Add doc/comment to built-in signature verification
v15:
+ Add more docs related to IPE
+ Switch the hook call to security_inode_setintegrity()
---
Documentation/filesystems/fsverity.rst | 12 ++++++++++--
fs/verity/fsverity_private.h | 2 +-
fs/verity/open.c | 24 +++++++++++++++++++++++-
fs/verity/signature.c | 5 ++++-
include/linux/security.h | 1 +
5 files changed, 39 insertions(+), 5 deletions(-)
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 13e4b18e5dbb..708c79631f32 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -461,7 +461,10 @@ Enabling this option adds the following:
3. A new sysctl "fs.verity.require_signatures" is made available.
When set to 1, the kernel requires that all verity files have a
- correctly signed digest as described in (2).
+ correctly signed digest as described in (2). Note that verification
+ happens as long as the file's signature exists regardless of the state of
+ "fs.verity.require_signatures", and the IPE LSM relies on this behavior
+ to save verified signature into LSM blobs.
The data that the signature as described in (2) must be a signature of
is the fs-verity file digest in the following format::
@@ -481,7 +484,7 @@ be carefully considered before using them:
- Builtin signature verification does *not* make the kernel enforce
that any files actually have fs-verity enabled. Thus, it is not a
- complete authentication policy. Currently, if it is used, the only
+ complete authentication policy. Currently, if it is used, one
way to complete the authentication policy is for trusted userspace
code to explicitly check whether files have fs-verity enabled with a
signature before they are accessed. (With
@@ -489,6 +492,11 @@ be carefully considered before using them:
enabled suffices.) But, in this case the trusted userspace code
could just store the signature alongside the file and verify it
itself using a cryptographic library, instead of using this feature.
+ Another approach is to utilize built-in signature verification in
+ conjunction with the IPE LSM, which supports defining
+ a kernel-enforced, system-wide authentication policy that allows only
+ files with an fs-verity signature enabled to perform certain operations,
+ such as execution. Note that IPE doesn't require fs.verity.require_signatures=1.
- A file's builtin signature can only be set at the same time that
fs-verity is being enabled on the file. Changing or deleting the
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
index b3506f56e180..a0e786c611c9 100644
--- a/fs/verity/fsverity_private.h
+++ b/fs/verity/fsverity_private.h
@@ -117,7 +117,7 @@ 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 fdeb95eca3af..8ad9cb5d6666 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_setintegrity(struct inode *inode,
+ const struct fsverity_descriptor *desc)
+{
+ return security_inode_setintegrity(inode, LSM_INTGR_FSV_SIG,
+ desc->signature,
+ le32_to_cpu(desc->sig_size));
+}
+#else
+static inline int fsverity_inode_setintegrity(struct inode *inode,
+ const struct fsverity_descriptor *desc)
+{
+ return 0;
+}
+#endif /* CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
+
/*
* 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;
@@ -241,6 +258,11 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
}
}
+ err = fsverity_inode_setintegrity(inode, desc);
+
+ if (err)
+ goto fail;
+
return vi;
fail:
diff --git a/fs/verity/signature.c b/fs/verity/signature.c
index 90c07573dd77..d4ed03a114e9 100644
--- a/fs/verity/signature.c
+++ b/fs/verity/signature.c
@@ -41,7 +41,10 @@ static struct key *fsverity_keyring;
* @sig_size: size of signature in bytes, or 0 if no signature
*
* If the file includes a signature of its fs-verity file digest, verify it
- * against the certificates in the fs-verity keyring.
+ * against the certificates in the fs-verity keyring. Note that verification
+ * happens as long as the file's signature exists regardless of the state of
+ * fsverity_require_signatures, and the IPE LSM relies on this behavior
+ * to save the verified file signature of the file into security blobs.
*
* Return: 0 on success (signature valid or not required); -errno on failure
*/
diff --git a/include/linux/security.h b/include/linux/security.h
index 0885866b261e..edd12c0a673a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -86,6 +86,7 @@ enum lsm_event {
enum lsm_intgr_type {
LSM_INTGR_DMV_SIG,
LSM_INTGR_DMV_ROOTHASH,
+ LSM_INTGR_FSV_SIG,
__LSM_INTGR_MAX
};
--
2.44.0
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
v11:
+ Introduced
v12:
+ No changes
v13:
+ No changes
v14:
+ Add documentation
v15:
+ No changes
---
drivers/md/dm.c | 12 ++++++++++++
include/linux/device-mapper.h | 9 +++++++++
2 files changed, 21 insertions(+)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 56aa2a8b9d71..16d3fd644176 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2270,6 +2270,18 @@ 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 82b2195efaca..ad368904b1d5 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -160,6 +160,14 @@ 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);
+/*
+ * This hook allows DM targets in an inactive table to complete their setup
+ * before the table is made active.
+ * Returns:
+ * < 0 : error
+ * = 0 : success
+ */
+typedef int (*dm_finalize_fn) (struct dm_target *target);
void dm_error(const char *message);
@@ -210,6 +218,7 @@ 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;
--
2.44.0
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
v12:
+ Fix audit format
+ Simplify property evaluation
v13:
+ Remove the CONFIG_IPE_PROP_FS_VERITY dependency inside the parser
to make the policy grammar independent of the kernel config.
v14:
+ No changes
v15:
+ Fix on grammar issue in Kconfig
+ Switch hook to security_inode_setintegrity()
---
security/ipe/Kconfig | 13 +++++
security/ipe/audit.c | 17 ++++++
security/ipe/eval.c | 108 ++++++++++++++++++++++++++++++++++-
security/ipe/eval.h | 10 ++++
security/ipe/hooks.c | 28 +++++++++
security/ipe/hooks.h | 6 ++
security/ipe/ipe.c | 13 +++++
security/ipe/ipe.h | 3 +
security/ipe/policy.h | 3 +
security/ipe/policy_parser.c | 6 ++
10 files changed, 206 insertions(+), 1 deletion(-)
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 5433ca3fc855..2003c01767ad 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 evaluate to TRUE when
+ a file is fsverity enabled and with a signed digest or its
+ digest 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 3acbfecc9f43..f508944a3ed1 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -53,6 +53,9 @@ static const char *const audit_prop_names[__IPE_PROP_MAX] = {
"dmverity_roothash=",
"dmverity_signature=FALSE",
"dmverity_signature=TRUE",
+ "fsverity_digest=",
+ "fsverity_signature=FALSE",
+ "fsverity_signature=TRUE",
};
/**
@@ -66,6 +69,17 @@ static void audit_dmv_roothash(struct audit_buffer *ab, const void *rh)
ipe_digest_audit(ab, rh);
}
+/**
+ * audit_fsv_digest - audit the digest of a fsverity_digest property.
+ * @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)
+{
+ audit_log_format(ab, "%s", audit_prop_names[IPE_PROP_FSV_DIGEST]);
+ ipe_digest_audit(ab, d);
+}
+
/**
* audit_rule - audit an IPE policy rule approximation.
* @ab: Supplies a pointer to the audit_buffer to append to.
@@ -82,6 +96,9 @@ static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
case IPE_PROP_DMV_ROOTHASH:
audit_dmv_roothash(ab, ptr->value);
break;
+ case IPE_PROP_FSV_DIGEST:
+ audit_fsv_digest(ab, ptr->value);
+ break;
default:
audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
break;
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index 8dcf7809c9fc..8cb8c64221e0 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -10,6 +10,7 @@
#include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/moduleparam.h>
+#include <linux/fsverity.h>
#include "ipe.h"
#include "eval.h"
@@ -51,6 +52,23 @@ 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 populated.
+ * @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 populated.
@@ -63,13 +81,17 @@ void build_eval_ctx(struct ipe_eval_ctx *ctx,
enum ipe_op_type op,
enum ipe_hook_type hook)
{
+ struct inode *ino;
+
ctx->file = file;
ctx->op = op;
ctx->hook = hook;
if (file) {
build_ipe_sb_ctx(ctx, file);
- build_ipe_bdev_ctx(ctx, d_real_inode(file->f_path.dentry));
+ ino = d_real_inode(file->f_path.dentry);
+ build_ipe_bdev_ctx(ctx, ino);
+ build_ipe_inode_ctx(ctx, ino);
}
}
@@ -148,6 +170,84 @@ 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];
+ struct digest_info info;
+
+ if (!ctx->ino)
+ return false;
+ if (!fsverity_get_digest((struct inode *)ctx->ino,
+ digest,
+ NULL,
+ &alg))
+ return false;
+
+ info.alg = hash_algo_name[alg];
+ info.digest = digest;
+ info.digest_len = hash_digest_size[alg];
+
+ return ipe_digest_eval(p->value, &info);
+}
+
+/**
+ * evaluate_fsv_sig_false - Analyze @ctx against a fsv sig false property.
+ * @ctx: Supplies a pointer to the context being evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the property
+ * * false - The current @ctx doesn't match the property
+ */
+static bool evaluate_fsv_sig_false(const struct ipe_eval_ctx *const ctx)
+{
+ 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.
+ *
+ * Return:
+ * * true - The current @ctx match the property
+ * * false - The current @ctx doesn't match the property
+ */
+static bool evaluate_fsv_sig_true(const struct ipe_eval_ctx *const ctx)
+{
+ return !evaluate_fsv_sig_false(ctx);
+}
+#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)
+{
+ return false;
+}
+
+static bool evaluate_fsv_sig_true(const struct ipe_eval_ctx *const ctx)
+{
+ 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.
@@ -171,6 +271,12 @@ static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
return evaluate_dmv_sig_false(ctx);
case IPE_PROP_DMV_SIG_TRUE:
return evaluate_dmv_sig_true(ctx);
+ case IPE_PROP_FSV_DIGEST:
+ return evaluate_fsv_digest(ctx, p);
+ case IPE_PROP_FSV_SIG_FALSE:
+ return evaluate_fsv_sig_false(ctx);
+ case IPE_PROP_FSV_SIG_TRUE:
+ return evaluate_fsv_sig_true(ctx);
default:
return false;
}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 494c0754f512..73ac905dc97d 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -29,6 +29,12 @@ 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;
enum ipe_hook_type hook;
@@ -38,6 +44,10 @@ 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 1abddd6e1e7f..b9dc23047463 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -254,3 +254,31 @@ int ipe_bdev_setintegrity(struct block_device *bdev, enum lsm_intgr_type type,
return 0;
}
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+/**
+ * ipe_inode_setintegrity - save integrity data from a inode to IPE's LSM blob.
+ * @inode: The inode to source the security blob from.
+ * @type: Supplies the integrity type.
+ * @value: The value to be stored.
+ * @size: The size of @value.
+ *
+ * Saves fsverity signature into inode security blob
+ *
+ * Return:
+ * * 0 - OK
+ * * !0 - Error
+ */
+int ipe_inode_setintegrity(struct inode *inode, enum lsm_intgr_type type,
+ const void *value, size_t size)
+{
+ struct ipe_inode *inode_sec = ipe_inode(inode);
+
+ if (type == LSM_INTGR_FSV_SIG) {
+ inode_sec->fs_verity_signed = size > 0 && value;
+ return 0;
+ }
+
+ return 0;
+}
+#endif /* CONFIG_CONFIG_IPE_PROP_FS_VERITY */
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 6b735aac4028..cfa9920aa2e5 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>
enum ipe_hook_type {
IPE_HOOK_BPRM_CHECK = 0,
@@ -43,4 +44,9 @@ int ipe_bdev_setintegrity(struct block_device *bdev, enum lsm_intgr_type type,
const void *value, size_t len);
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+int ipe_inode_setintegrity(struct inode *inode, enum lsm_intgr_type type,
+ const void *value, size_t size);
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
+
#endif /* _IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 3d63e9672f12..86b87e287b69 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -16,6 +16,9 @@ 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 */
};
static const struct lsm_id ipe_lsmid = {
@@ -35,6 +38,13 @@ 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),
@@ -46,6 +56,9 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
LSM_HOOK_INIT(bdev_setintegrity, ipe_bdev_setintegrity),
#endif /* CONFIG_IPE_PROP_DM_VERITY */
+#ifdef CONFIG_IPE_PROP_FS_VERITY
+ LSM_HOOK_INIT(inode_setintegrity, ipe_inode_setintegrity),
+#endif /* CONFIG_IPE_PROP_FS_VERITY */
};
/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index 64626702b689..57d3fc22fe10 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -19,5 +19,8 @@ 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 35629e9699f7..ae6264874fd3 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 802e31f14b22..48dc11739072 100644
--- a/security/ipe/policy_parser.c
+++ b/security/ipe/policy_parser.c
@@ -273,6 +273,9 @@ static const match_table_t property_tokens = {
{IPE_PROP_DMV_ROOTHASH, "dmverity_roothash=%s"},
{IPE_PROP_DMV_SIG_FALSE, "dmverity_signature=FALSE"},
{IPE_PROP_DMV_SIG_TRUE, "dmverity_signature=TRUE"},
+ {IPE_PROP_FSV_DIGEST, "fsverity_digest=%s"},
+ {IPE_PROP_FSV_SIG_FALSE, "fsverity_signature=FALSE"},
+ {IPE_PROP_FSV_SIG_TRUE, "fsverity_signature=TRUE"},
{IPE_PROP_INVALID, NULL}
};
@@ -302,6 +305,7 @@ 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 +321,8 @@ 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:
--
2.44.0
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
v12:
+ No changes
v13:
+ No changes
v14:
+ No changes
v15:
+ Fix one grammar issue in Kconfig
---
MAINTAINERS | 1 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 2 +
scripts/ipe/polgen/Makefile | 5 ++
scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
security/ipe/.gitignore | 2 +
security/ipe/Kconfig | 10 +++
security/ipe/Makefile | 11 +++
security/ipe/fs.c | 8 ++
security/ipe/ipe.c | 12 +++
11 files changed, 199 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 095e55f1a183..d84739ab2ef4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10715,6 +10715,7 @@ 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 6673cbb6194f..a392fc7a69c7 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -52,6 +52,7 @@ 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..b6f05cf3dc0e
--- /dev/null
+++ b/scripts/ipe/polgen/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+polgen
diff --git a/scripts/ipe/polgen/Makefile b/scripts/ipe/polgen/Makefile
new file mode 100644
index 000000000000..c20456a2f2e9
--- /dev/null
+++ b/scripts/ipe/polgen/Makefile
@@ -0,0 +1,5 @@
+# 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..07313d3fd74a
--- /dev/null
+++ b/security/ipe/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+boot-policy.c
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 2003c01767ad..a18c5915b723 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 an 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 b16d87443a3b..8af6e39f9914 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 86b87e287b69..788118a40c02 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -9,6 +9,7 @@
#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 = {
@@ -73,9 +74,20 @@ 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_lsmid);
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;
}
--
2.44.0
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
v12:
+ Correct locking and remove redundant code
v13:
+ Move the free of old policy into the ipe_update_policy function
v14:
+ No changes
v15:
+ No changes
---
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 | 123 ++++++++++
security/ipe/policy.h | 7 +
security/ipe/policy_fs.c | 468 +++++++++++++++++++++++++++++++++++++++
8 files changed, 722 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..4949296caeb5
--- /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: 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 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)
+ 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 3bf7c1331d5e..53820ca6d5b7 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -8,6 +8,8 @@
#include "eval.h"
#include "hooks.h"
+bool ipe_enabled;
+
static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
.lbs_superblock = sizeof(struct ipe_superblock),
};
@@ -44,6 +46,7 @@ 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_lsmid);
+ ipe_enabled = true;
return 0;
}
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index fb8f0ad168b3..86c2b8394d93 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -14,4 +14,6 @@
#include <linux/lsm_hooks.h>
struct ipe_superblock *ipe_sb(const struct super_block *sb);
+extern bool ipe_enabled;
+
#endif /* _IPE_H */
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index f22a576a6d68..0ba2b9c62c23 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 +71,68 @@ 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 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
+ */
+int 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;
+
+ old = (struct ipe_policy *)root->i_private;
+ if (!old)
+ return -ENOENT;
+
+ new = ipe_new_policy(text, textlen, pkcs7, pkcs7len);
+ if (IS_ERR(new))
+ return PTR_ERR(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;
+ swap(new->policyfs, old->policyfs);
+
+ mutex_lock(&ipe_policy_lock);
+ ap = rcu_dereference_protected(ipe_active_policy,
+ lockdep_is_held(&ipe_policy_lock));
+ if (old == ap) {
+ rcu_assign_pointer(ipe_active_policy, new);
+ mutex_unlock(&ipe_policy_lock);
+ synchronize_rcu();
+ } else {
+ mutex_unlock(&ipe_policy_lock);
+ }
+ ipe_free_policy(old);
+
+ return 0;
+err:
+ ipe_free_policy(new);
+ return rc;
+}
+
/**
* ipe_new_policy - Allocate and parse an ipe_policy structure.
*
@@ -99,3 +189,36 @@ 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, which i_private has the policy, 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;
+
+ mutex_lock(&ipe_policy_lock);
+
+ ap = rcu_dereference_protected(ipe_active_policy,
+ lockdep_is_held(&ipe_policy_lock));
+ if (ap == p) {
+ mutex_unlock(&ipe_policy_lock);
+ return 0;
+ }
+ if (ap && ver_to_u64(ap) > ver_to_u64(p)) {
+ mutex_unlock(&ipe_policy_lock);
+ return -EINVAL;
+ }
+
+ rcu_assign_pointer(ipe_active_policy, p);
+ mutex_unlock(&ipe_policy_lock);
+ synchronize_rcu();
+
+ return 0;
+}
diff --git a/security/ipe/policy.h b/security/ipe/policy.h
index fb48024bb63e..dba5e71e089e 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 +77,16 @@ 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);
+int 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..4bb7e09e58f6
--- /dev/null
+++ b/security/ipe/policy_fs.c
@@ -0,0 +1,468 @@
+// 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: Supplies 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/$name/policy".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the plain-text version of the policy
+ * on success.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_policy(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = simple_read_from_buffer(data, len, offset, p->text, p->textlen);
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * read_name: Read handler for "ipe/policies/$name/name".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies 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/$name/version".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the version string on success.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t read_version(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ ssize_t rc = 0;
+ size_t strsize = 0;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+ char buffer[MAX_VERSION_SIZE] = { 0 };
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ strsize = scnprintf(buffer, ARRAY_SIZE(buffer), "%hu.%hu.%hu",
+ p->parsed->version.major, p->parsed->version.minor,
+ p->parsed->version.rev);
+
+ rc = simple_read_from_buffer(data, len, offset, buffer, strsize);
+
+out:
+ inode_unlock_shared(root);
+
+ return rc;
+}
+
+/**
+ * setactive - Write handler for "ipe/policies/$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);
+
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ rc = -ENOENT;
+ goto out;
+ }
+
+ rc = ipe_set_active_pol(p);
+
+out:
+ inode_unlock(root);
+ return (rc < 0) ? rc : len;
+}
+
+/**
+ * getactive - Read handler for "ipe/policies/$name/active".
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * @data will be populated with the 1 or 0 depending on if the
+ * corresponding policy is active.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getactive(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ const char *str;
+ struct inode *root = NULL;
+ const struct ipe_policy *p = NULL;
+
+ root = d_inode(f->f_path.dentry->d_parent);
+
+ inode_lock_shared(root);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ inode_unlock_shared(root);
+ return -ENOENT;
+ }
+ inode_unlock_shared(root);
+
+ str = (p == rcu_access_pointer(ipe_active_policy)) ? "1" : "0";
+ rc = simple_read_from_buffer(data, len, offset, str, 1);
+
+ return rc;
+}
+
+/**
+ * update_policy - Write handler for "ipe/policies/$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 $name,
+ * in-place.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t update_policy(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ char *copy = NULL;
+ struct inode *root = NULL;
+ int rc = 0;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ copy = memdup_user(data, len);
+ if (IS_ERR(copy))
+ return PTR_ERR(copy);
+
+ root = d_inode(f->f_path.dentry->d_parent);
+ inode_lock(root);
+ rc = ipe_update_policy(root, NULL, 0, copy, len);
+ inode_unlock(root);
+
+ kfree(copy);
+ if (rc)
+ return rc;
+
+ return len;
+}
+
+/**
+ * delete_policy - write handler for "ipe/policies/$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);
+ p = (struct ipe_policy *)root->i_private;
+ if (!p) {
+ inode_unlock(root);
+ return -ENOENT;
+ }
+
+ mutex_lock(&ipe_policy_lock);
+ 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;
+ }
+ mutex_unlock(&ipe_policy_lock);
+
+ root->i_private = NULL;
+ inode_unlock(root);
+
+ 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))
+ return PTR_ERR(policyfs);
+
+ 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);
+ p->policyfs = policyfs;
+ root->i_private = p;
+ inode_unlock(root);
+
+ return 0;
+err:
+ securityfs_recursive_remove(policyfs);
+ return rc;
+}
--
2.44.0
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 ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1
pid=297 comm="sh" path="/root/vol/bin/hello" dev="tmpfs"
ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
audit: AUDIT1420 ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1
pid=299 comm="sh" path="/mnt/ipe/bin/hello" dev="dm-0"
ino=2 rule="DEFAULT action=DENY"
audit: AUDIT1420 ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1
pid=300 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 initramfs to run. The three identical `hello`
binary were placed at different locations, only the first hello from
the rootfs(initramfs) was allowed.
Field ipe_op followed by the IPE operation name associated with the log.
Field ipe_hook followed by the name of the LSM hook that triggered the IPE
event.
Field enforcing followed by the enforcement state of IPE. (it will be
introduced in the next commit)
Field pid followed by the pid of the process that triggered the IPE
event.
Field comm followed by the command line program name of the process that
triggered the IPE event.
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 ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1
pid=2138 comm="bash" 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=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F2676
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 indented 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
v12:
+ Add ipe_op, ipe_hook, and enforcing fields to AUDIT_IPE_ACCESS
v13:
+ Remove dependency on CONFIG_BLK_DEV_INITRD
+ Add field placeholders for anonymous files
v14:
+ No changes
v15:
+ No changes
---
include/uapi/linux/audit.h | 3 +
security/ipe/Kconfig | 2 +-
security/ipe/Makefile | 1 +
security/ipe/audit.c | 214 +++++++++++++++++++++++++++++++++++++
security/ipe/audit.h | 18 ++++
security/ipe/eval.c | 44 ++++++--
security/ipe/eval.h | 13 ++-
security/ipe/fs.c | 70 ++++++++++++
security/ipe/hooks.c | 10 +-
security/ipe/hooks.h | 11 ++
security/ipe/policy.c | 5 +
11 files changed, 374 insertions(+), 17 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..f167fdc87986
--- /dev/null
+++ b/security/ipe/audit.c
@@ -0,0 +1,214 @@
+// 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 + 1] = {
+ "EXECUTE",
+ "FIRMWARE",
+ "KMODULE",
+ "KEXEC_IMAGE",
+ "KEXEC_INITRAMFS",
+ "POLICY",
+ "X509_CERT",
+ "UNKNOWN",
+};
+
+static const char *const audit_hook_names[__IPE_HOOK_MAX] = {
+ "BPRM_CHECK",
+ "MMAP",
+ "MPROTECT",
+ "KERNEL_READ",
+ "KERNEL_LOAD",
+};
+
+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=\"%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.
+ */
+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];
+ char comm[sizeof(current->comm)];
+
+ if (act != IPE_ACTION_DENY && !READ_ONCE(success_audit))
+ return;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
+ if (!ab)
+ return;
+
+ audit_log_format(ab, "ipe_op=%s ipe_hook=%s pid=%d comm=",
+ op, audit_hook_names[ctx->hook],
+ task_tgid_nr(current));
+ audit_log_untrustedstring(ab, get_task_comm(comm, current));
+
+ 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);
+ } else {
+ audit_log_format(ab, " dev=? ino=?");
+ }
+ } else {
+ audit_log_format(ab, " path=? dev=? 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.
+ * @audit_format: Supplies a pointer to the audit format string
+ * @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.
+ * @op: Supplies a pointer to the previously activated policy to audit.
+ * @np: Supplies a pointer to the newly activated 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 bef204decbbf..274f7346ef42 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -9,12 +9,15 @@
#include <linux/file.h>
#include <linux/sched.h>
#include <linux/rcupdate.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;
#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb)
@@ -33,13 +36,16 @@ static void build_ipe_sb_ctx(struct ipe_eval_ctx *ctx, const struct file *const
* @ctx: Supplies a pointer to the context to be populated.
* @file: Supplies a pointer to the file to associated with the evaluation.
* @op: Supplies the IPE policy operation associated with the evaluation.
+ * @hook: Supplies the LSM hook associated with the evaluation.
*/
void build_eval_ctx(struct ipe_eval_ctx *ctx,
const struct file *file,
- enum ipe_op_type op)
+ enum ipe_op_type op,
+ enum ipe_hook_type hook)
{
ctx->file = file;
ctx->op = op;
+ ctx->hook = hook;
if (file)
build_ipe_sb_ctx(ctx, file);
@@ -95,6 +101,7 @@ 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;
@@ -109,14 +116,15 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
}
if (ctx->op == IPE_OP_INVALID) {
- if (pol->parsed->global_default_action == IPE_ACTION_DENY) {
- rcu_read_unlock();
- return -EACCES;
- }
- if (pol->parsed->global_default_action == IPE_ACTION_INVALID)
+ if (pol->parsed->global_default_action == IPE_ACTION_INVALID) {
WARN(1, "no default rule set for unknown op, ALLOW it");
+ action = IPE_ACTION_ALLOW;
+ } else {
+ action = pol->parsed->global_default_action;
+ }
rcu_read_unlock();
- return 0;
+ match_type = IPE_MATCH_GLOBAL;
+ goto eval;
}
rules = &pol->parsed->rules[ctx->op];
@@ -134,16 +142,32 @@ 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;
return 0;
}
+
+/* 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 884821494525..4631b236358e 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -10,10 +10,12 @@
#include <linux/types.h>
#include "policy.h"
+#include "hooks.h"
#define IPE_EVAL_CTX_INIT ((struct ipe_eval_ctx){ 0 })
extern struct ipe_policy __rcu *ipe_active_policy;
+extern bool success_audit;
struct ipe_superblock {
bool initramfs;
@@ -21,12 +23,21 @@ struct ipe_superblock {
struct ipe_eval_ctx {
enum ipe_op_type op;
+ enum ipe_hook_type hook;
const struct file *file;
bool initramfs;
};
-void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
+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, enum ipe_hook_type hook);
int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
#endif /* _IPE_EVAL_H */
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index 4949296caeb5..95407997cf0c 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)
@@ -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/hooks.c b/security/ipe/hooks.c
index 23cf070438fa..6bcc7908ed13 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -28,7 +28,7 @@ int ipe_bprm_check_security(struct linux_binprm *bprm)
{
struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
- build_eval_ctx(&ctx, bprm->file, IPE_OP_EXEC);
+ build_eval_ctx(&ctx, bprm->file, IPE_OP_EXEC, IPE_HOOK_BPRM_CHECK);
return ipe_evaluate_event(&ctx);
}
@@ -53,7 +53,7 @@ int ipe_mmap_file(struct file *f, unsigned long reqprot __always_unused,
struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
if (prot & PROT_EXEC) {
- build_eval_ctx(&ctx, f, IPE_OP_EXEC);
+ build_eval_ctx(&ctx, f, IPE_OP_EXEC, IPE_HOOK_MMAP);
return ipe_evaluate_event(&ctx);
}
@@ -85,7 +85,7 @@ int ipe_file_mprotect(struct vm_area_struct *vma,
return 0;
if (prot & PROT_EXEC) {
- build_eval_ctx(&ctx, vma->vm_file, IPE_OP_EXEC);
+ build_eval_ctx(&ctx, vma->vm_file, IPE_OP_EXEC, IPE_HOOK_MPROTECT);
return ipe_evaluate_event(&ctx);
}
@@ -135,7 +135,7 @@ int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
WARN(1, "no rule setup for kernel_read_file enum %d", id);
}
- build_eval_ctx(&ctx, file, op);
+ build_eval_ctx(&ctx, file, op, IPE_HOOK_KERNEL_READ);
return ipe_evaluate_event(&ctx);
}
@@ -179,7 +179,7 @@ int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents)
WARN(1, "no rule setup for kernel_load_data enum %d", id);
}
- build_eval_ctx(&ctx, NULL, op);
+ build_eval_ctx(&ctx, NULL, op, IPE_HOOK_KERNEL_LOAD);
return ipe_evaluate_event(&ctx);
}
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 21f49cdc2fcd..b92c1d78e253 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -9,6 +9,17 @@
#include <linux/binfmts.h>
#include <linux/security.h>
+enum ipe_hook_type {
+ IPE_HOOK_BPRM_CHECK = 0,
+ IPE_HOOK_MMAP,
+ IPE_HOOK_MPROTECT,
+ IPE_HOOK_KERNEL_READ,
+ IPE_HOOK_KERNEL_LOAD,
+ __IPE_HOOK_MAX
+};
+
+#define IPE_HOOK_INVALID __IPE_HOOK_MAX
+
int ipe_bprm_check_security(struct linux_binprm *bprm);
int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index 0ba2b9c62c23..8b9878f2375b 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);
@@ -114,6 +115,7 @@ int ipe_update_policy(struct inode *root, const char *text, size_t textlen,
root->i_private = new;
swap(new->policyfs, old->policyfs);
+ ipe_audit_policy_load(new);
mutex_lock(&ipe_policy_lock);
ap = rcu_dereference_protected(ipe_active_policy,
@@ -122,6 +124,7 @@ int ipe_update_policy(struct inode *root, const char *text, size_t textlen,
rcu_assign_pointer(ipe_active_policy, new);
mutex_unlock(&ipe_policy_lock);
synchronize_rcu();
+ ipe_audit_policy_activation(old, new);
} else {
mutex_unlock(&ipe_policy_lock);
}
@@ -220,5 +223,7 @@ int ipe_set_active_pol(const struct ipe_policy *p)
mutex_unlock(&ipe_policy_lock);
synchronize_rcu();
+ ipe_audit_policy_activation(ap, p);
+
return 0;
}
--
2.44.0
From: Deven Bowers <[email protected]>
Add various happy/unhappy unit tests for both IPE's policy parser.
Besides, a test suite for IPE functionality is available at
https://github.com/microsoft/ipe/tree/test-suite
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
v12:
+ No changes
v13:
+ No changes
v14:
+ No changes
v15:
+ 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 a18c5915b723..1b2a306155ae 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);
--
2.44.0
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 suggestions
+ Update audit events part
v11:
+ No changes
v12:
+ Update audit formats
+ Update initramfs related docs
+ Add test suite link
v13:
+ No changes
v14:
+ No changes
v15:
+ Update boot_verified part
+ Fix format issues
+ Add IPE doc link to fsverity.rst
---
Documentation/admin-guide/LSM/index.rst | 1 +
Documentation/admin-guide/LSM/ipe.rst | 774 ++++++++++++++++++
.../admin-guide/kernel-parameters.txt | 12 +
Documentation/filesystems/fsverity.rst | 1 +
Documentation/security/index.rst | 1 +
Documentation/security/ipe.rst | 444 ++++++++++
MAINTAINERS | 2 +
7 files changed, 1235 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..27496ce32f16
--- /dev/null
+++ b/Documentation/admin-guide/LSM/ipe.rst
@@ -0,0 +1,774 @@
+.. 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 seven files: ``pkcs7``, ``policy``,
+``name``, ``version``, ``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): ipe_op=EXECUTE ipe_hook=MMAP enforcing=1 pid=2241 comm="ld-linux.so" path="/deny/lib/libc.so.6" dev="sda2" ino=14549020 rule="DEFAULT action=DENY"
+ type=1300 audit(1653364370.067:61): SYSCALL arch=c000003e syscall=9 success=no exit=-13 a0=7f1105a28000 a1=195000 a2=5 a3=812 items=0 ppid=2219 pid=2241 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=2 comm="ld-linux.so" exe="/tmp/ipe-test/lib/ld-linux.so" subj=unconfined key=(null)
+ type=1327 audit(1653364370.067:61): 707974686F6E3300746573742F6D61696E2E7079002D6E00
+
+ type=1420 audit(1653364735.161:64): ipe_op=EXECUTE ipe_hook=MMAP enforcing=1 pid=2472 comm="mmap_test" path=? dev=? ino=? rule="DEFAULT action=DENY"
+ type=1300 audit(1653364735.161:64): SYSCALL arch=c000003e syscall=9 success=no exit=-13 a0=0 a1=1000 a2=4 a3=21 items=0 ppid=2219 pid=2472 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=2 comm="mmap_test" exe="/root/overlake_test/upstream_test/vol_fsverity/bin/mmap_test" subj=unconfined key=(null)
+ type=1327 audit(1653364735.161:64): 707974686F6E3300746573742F6D61696E2E7079002D6E00
+
+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 |
++===========+============+===========+=================================================================================+
+| ipe_op | string | No | The IPE operation name associated with the log |
++-----------+------------+-----------+---------------------------------------------------------------------------------+
+| ipe_hook | string | No | The name of the LSM hook that triggered the IPE event |
++-----------+------------+-----------+---------------------------------------------------------------------------------+
+| enforcing | integer | No | The current IPE enforcing state 1 is in enforcing mode, 0 is in permissive mode |
++-----------+------------+-----------+---------------------------------------------------------------------------------+
+| pid | integer | No | The pid of the process that triggered the IPE event. |
++-----------+------------+-----------+---------------------------------------------------------------------------------+
+| comm | string | No | The command line program name of the process that triggered the IPE event |
++-----------+------------+-----------+---------------------------------------------------------------------------------+
+| 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 descriptions:
+
++------------------------+------------+-----------+---------------------------------------------------+
+| 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 descriptions:
+
++----------------+------------+-----------+---------------------------------------------------+
+| 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 descriptions:
+
++---------------+------------+-----------+-------------------------------------------------------------------------------------------------+
+| 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 files from initramfs.
+ The format of this property is::
+
+ boot_verified=(TRUE|FALSE)
+
+
+ .. WARNING::
+
+ This property will trust files from initramfs(rootfs). It should
+ only be used during early booting stage. Before mounting the real
+ rootfs on top of the initramfs, initramfs
+ script will recursively remove all files and directories on the
+ initramfs. This is typically implemented by using switch_root(8) [#switch_root]_.
+ Therefore the initramfs will be empty and not accessible after the real
+ rootfs takes over. It is advised to switch to a different policy
+ that doesn't rely on the property after this point.
+ This ensures that the trust policies remain relevant and effective
+ throughout the system's operation.
+
+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 fsverity_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 initramfs
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=Allow_All_Initramfs policy_version=0.0.0
+ DEFAULT action=DENY
+
+ op=EXECUTE boot_verified=TRUE action=ALLOW
+
+Allow any signed dm-verity volume and the initramfs
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+ policy_name=AllowSignedAndInitramfs 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=AllowSignedAndInitramfs 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=AllowSignedAndInitramfs 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>`_
+- Documentation/security/ipe.rst
+
+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 only covers the IPE's
+ kernel read operations, 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] 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.
+
+.. [#switch_root] https://man7.org/linux/man-pages/man8/switch_root.8.html
+
+.. [#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 62feb8f31381..0767135d1111 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2305,6 +2305,18 @@
ipcmni_extend [KNL,EARLY] 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/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 708c79631f32..f09308099bd7 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -497,6 +497,7 @@ be carefully considered before using them:
a kernel-enforced, system-wide authentication policy that allows only
files with an fs-verity signature enabled to perform certain operations,
such as execution. Note that IPE doesn't require fs.verity.require_signatures=1.
+ Please refer to Documentation/admin-guide/LSM/ipe.rst for more details.
- A file's builtin signature can only be set at the same time that
fs-verity is being enabled on the file. Changing or deleting the
diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst
index 59f8fc106cb0..3e0a7114a862 100644
--- a/Documentation/security/index.rst
+++ b/Documentation/security/index.rst
@@ -19,3 +19,4 @@ 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..ec0f41844c34
--- /dev/null
+++ b/Documentation/security/ipe.rst
@@ -0,0 +1,444 @@
+.. 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 aforementioned specific data files.
+
+ Unlike executables, read operations (like those on the protected data
+ files), cannot be enforced to be globally integrity 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 implicit 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 for the policy parser. 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_BLK_DEV_INITRD=y
+
+ CONFIG_SECURITY_IPE=y
+ CONFIG_IPE_PROP_DM_VERITY=y
+ CONFIG_IPE_PROP_FS_VERITY=y
+ CONFIG_SECURITY_IPE_KUNIT_TEST=y
+
+In addition, IPE has a python based integration
+`test suite <https://github.com/microsoft/ipe/tree/test-suite>`_ that
+can test both user interfaces and enforcement functionalities.
diff --git a/MAINTAINERS b/MAINTAINERS
index d84739ab2ef4..ee081f7d5fa3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10715,6 +10715,8 @@ 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/
--
2.44.0
On Fri, Mar 15, 2024 at 08:35:48PM -0700, Fan Wu wrote:
> +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 evaluate to TRUE when
> + a file is fsverity enabled and with a signed digest
Again: why would anyone care if there is a signature, if that signature is not
checked.
I think you meant to write something like: "when a file is fsverity enabled and
has a valid builtin signature whose signing cert is in the .fs-verity keyring".
- Eric
On Fri, Mar 15, 2024 at 08:35:47PM -0700, Fan Wu 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.
>
> This patch introduces a new security_inode_setintegrity() hook call in
> fsverity to store the verified fsverity signature in the inode's LSM blobs.
> The hook call is executed after fsverity_verify_signature(), ensuring that
> the signature is verified against fsverity's keyring.
>
> The last commit in this patch set will add a link to the IPE documentation in
> fsverity.rst.
There are multiple types of fsverity signatures. Please make it clear which one
you're talking about ("fsverity builtin signatures").
> diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
> index 13e4b18e5dbb..708c79631f32 100644
> --- a/Documentation/filesystems/fsverity.rst
> +++ b/Documentation/filesystems/fsverity.rst
> @@ -461,7 +461,10 @@ Enabling this option adds the following:
>
> 3. A new sysctl "fs.verity.require_signatures" is made available.
> When set to 1, the kernel requires that all verity files have a
> - correctly signed digest as described in (2).
> + correctly signed digest as described in (2). Note that verification
> + happens as long as the file's signature exists regardless of the state of
> + "fs.verity.require_signatures", and the IPE LSM relies on this behavior
> + to save verified signature into LSM blobs.
This probably should go in item (2) instead, as that already mentions the
behavior when opening a file.
> The data that the signature as described in (2) must be a signature of
> is the fs-verity file digest in the following format::
> @@ -481,7 +484,7 @@ be carefully considered before using them:
>
> - Builtin signature verification does *not* make the kernel enforce
> that any files actually have fs-verity enabled. Thus, it is not a
> - complete authentication policy. Currently, if it is used, the only
> + complete authentication policy. Currently, if it is used, one
> way to complete the authentication policy is for trusted userspace
> code to explicitly check whether files have fs-verity enabled with a
> signature before they are accessed. (With
> @@ -489,6 +492,11 @@ be carefully considered before using them:
> enabled suffices.) But, in this case the trusted userspace code
> could just store the signature alongside the file and verify it
> itself using a cryptographic library, instead of using this feature.
> + Another approach is to utilize built-in signature verification in
> + conjunction with the IPE LSM, which supports defining
> + a kernel-enforced, system-wide authentication policy that allows only
> + files with an fs-verity signature enabled to perform certain operations,
> + such as execution. Note that IPE doesn't require fs.verity.require_signatures=1.
Make this a new paragraph.
Also, the acronym "IPE" should be spelled out somewhere.
IPE should be mentioned in the list in the "Use cases" section next to IMA, and
it can be spelled out there.
> +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> +static int fsverity_inode_setintegrity(struct inode *inode,
> + const struct fsverity_descriptor *desc)
> +{
> + return security_inode_setintegrity(inode, LSM_INTGR_FSV_SIG,
> + desc->signature,
> + le32_to_cpu(desc->sig_size));
> +}
> +#else
> +static inline int fsverity_inode_setintegrity(struct inode *inode,
> + const struct fsverity_descriptor *desc)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
> +
> /*
> * 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;
> @@ -241,6 +258,11 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode,
> }
> }
>
> + err = fsverity_inode_setintegrity(inode, desc);
> +
> + if (err)
> + goto fail;
Delete the blank line before 'if (err)'
> diff --git a/fs/verity/signature.c b/fs/verity/signature.c
> index 90c07573dd77..d4ed03a114e9 100644
> --- a/fs/verity/signature.c
> +++ b/fs/verity/signature.c
> @@ -41,7 +41,10 @@ static struct key *fsverity_keyring;
> * @sig_size: size of signature in bytes, or 0 if no signature
> *
> * If the file includes a signature of its fs-verity file digest, verify it
> - * against the certificates in the fs-verity keyring.
> + * against the certificates in the fs-verity keyring. Note that verification
> + * happens as long as the file's signature exists regardless of the state of
> + * fsverity_require_signatures, and the IPE LSM relies on this behavior
> + * to save the verified file signature of the file into security blobs.
"save the verified file signature of the file into security blobs" isn't what
IPE actually does, though. And even if it was, it would not explain why IPE
expects the signature to be verified.
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 0885866b261e..edd12c0a673a 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -86,6 +86,7 @@ enum lsm_event {
> enum lsm_intgr_type {
> LSM_INTGR_DMV_SIG,
> LSM_INTGR_DMV_ROOTHASH,
> + LSM_INTGR_FSV_SIG,
> __LSM_INTGR_MAX
> };
These are hard to understand because they are abbreviated too much. And again,
there are multiple type of fsverity signatures. How about:
enum lsm_integrity_type {
LSM_INTEGRITY_DM_VERITY_SIG,
LSM_INTEGRITY_DM_VERITY_ROOT_HASH,
LSM_INTEGRITY_FS_VERITY_BUILTIN_SIG,
__LSM_INTEGRITY_MAX
};
- Eric
On 3/15/2024 8:35 PM, Fan Wu wrote:
> This patch introduces a new hook to notify security system that the
> content of initramfs has been unpacked into the rootfs.
>
> Upon receiving this notification, the security system can activate
> a policy to allow only files that originated from the initramfs to
> execute or load into kernel during the early stages of booting.
>
> This approach is crucial for minimizing the attack surface by
> ensuring that only trusted files from the initramfs are operational
> in the critical boot phase.
>
> Signed-off-by: Fan Wu <[email protected]>
>
> ---
> v1-v11:
> + Not present
>
> v12:
> + Introduced
>
> v13:
> + Rename the hook name to initramfs_populated()
>
> v14:
> + No changes
>
> v15:
> + No changes
> ---
> include/linux/lsm_hook_defs.h | 2 ++
> include/linux/security.h | 8 ++++++++
> init/initramfs.c | 3 +++
> security/security.c | 10 ++++++++++
> 4 files changed, 23 insertions(+)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 334e00efbde4..7db99ae75651 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -450,3 +450,5 @@ 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(void, LSM_RET_VOID, initramfs_populated, void)
This is an awfully expensive way to set a flag. Adding a LSM hook list
isn't free. Isn't there a way to capture this state change through one of
the mount hooks?
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 41a8f667bdfa..14fff542f2e3 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -2255,4 +2255,12 @@ static inline int security_uring_cmd(struct io_uring_cmd *ioucmd)
> #endif /* CONFIG_SECURITY */
> #endif /* CONFIG_IO_URING */
>
> +#ifdef CONFIG_SECURITY
> +extern void security_initramfs_populated(void);
> +#else
> +static inline void security_initramfs_populated(void)
> +{
> +}
> +#endif /* CONFIG_SECURITY */
> +
> #endif /* ! __LINUX_SECURITY_H */
> diff --git a/init/initramfs.c b/init/initramfs.c
> index da79760b8be3..cc9115117896 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -17,6 +17,7 @@
> #include <linux/namei.h>
> #include <linux/init_syscalls.h>
> #include <linux/umh.h>
> +#include <linux/security.h>
>
> #include "do_mounts.h"
>
> @@ -719,6 +720,8 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie)
> #endif
> }
>
> + security_initramfs_populated();
> +
> done:
> /*
> * If the initrd region is overlapped with crashkernel reserved region,
> diff --git a/security/security.c b/security/security.c
> index 287bfac6b471..b10230c51c0b 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -5675,3 +5675,13 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
> return call_int_hook(uring_cmd, ioucmd);
> }
> #endif /* CONFIG_IO_URING */
> +
> +/**
> + * security_initramfs_populated() - Notify LSMs that initramfs has been loaded
> + *
> + * Tells the LSMs the initramfs has been unpacked into the rootfs.
> + */
> +void security_initramfs_populated(void)
> +{
> + call_void_hook(initramfs_populated);
> +}
On Sun, 2024-03-17 at 22:17 -0700, Eric Biggers wrote:
> On Fri, Mar 15, 2024 at 08:35:48PM -0700, Fan Wu wrote:
> > +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 evaluate to TRUE when
> > + a file is fsverity enabled and with a signed digest
>
> Again: why would anyone care if there is a signature, if that signature is not
> checked.
>
> I think you meant to write something like: "when a file is fsverity enabled and
> has a valid builtin signature whose signing cert is in the .fs-verity keyring".
I was also thinking the same. I didn't follow the recent development
closely, but unless IPE locks somehow the .fs-verity keyring, the
property you suggested would not be immutable. Meaning that someone can
add/remove a key in that keyring, making the property true or false.
Roberto
On 3/17/2024 10:17 PM, Eric Biggers wrote:
> On Fri, Mar 15, 2024 at 08:35:48PM -0700, Fan Wu wrote:
>> +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 evaluate to TRUE when
>> + a file is fsverity enabled and with a signed digest
>
> Again: why would anyone care if there is a signature, if that signature is not
> checked.
>
> I think you meant to write something like: "when a file is fsverity enabled and
> has a valid builtin signature whose signing cert is in the .fs-verity keyring".
>
> - Eric
Thanks for the suggestion. I agree this is a more accurate description.
I'll update the description to include these details.
-Fan
On 3/18/2024 1:08 AM, Roberto Sassu wrote:
> On Sun, 2024-03-17 at 22:17 -0700, Eric Biggers wrote:
>> On Fri, Mar 15, 2024 at 08:35:48PM -0700, Fan Wu wrote:
>>> +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 evaluate to TRUE when
>>> + a file is fsverity enabled and with a signed digest
>>
>> Again: why would anyone care if there is a signature, if that signature is not
>> checked.
>>
>> I think you meant to write something like: "when a file is fsverity enabled and
>> has a valid builtin signature whose signing cert is in the .fs-verity keyring".
>
> I was also thinking the same. I didn't follow the recent development
> closely, but unless IPE locks somehow the .fs-verity keyring, the
> property you suggested would not be immutable. Meaning that someone can
> add/remove a key in that keyring, making the property true or false.
>
> Roberto
Yes, the .fs-verity keyring's mutability could affect the property's
immutability. However, we are not planing to "lock" the keyrings, but we
would like to use policies languages to express what certificate can be
trusted.
For example, we can have a rule like this:
#Certificate declaration
CERTIFICATE=MyCertificate CertThumbprint=DummyThumbprint
op=EXECUTE fsverity_signature=MyCertificate action=ALLOW
This will be our immediate next work after the initial version is accepted.
-Fan
On Mar 15, 2024 Fan Wu <[email protected]> wrote:
>
> This patch introduces a new hook to save block device's integrity
> data. For example, for dm-verity, LSMs can use this hook to save
> the roothash signature of a dm-verity into the security blob,
> and LSMs can make access decisions based on the data inside
> the signature, like the signer certificate.
>
> Signed-off-by: Fan Wu <[email protected]>
>
> --
> v1-v14:
> + Not present
>
> v15:
> + Introduced
>
> ---
> include/linux/lsm_hook_defs.h | 2 ++
> include/linux/security.h | 14 ++++++++++++++
> security/security.c | 28 ++++++++++++++++++++++++++++
> 3 files changed, 44 insertions(+)
I'm not sure why you made this a separate patch, help? If there is
no significant reason why this is separate, please squash it together
with patch 11/21.
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index c335404470dc..6808ae763913 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -455,4 +455,6 @@ LSM_HOOK(void, LSM_RET_VOID, initramfs_populated, void)
>
> 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_setintegrity, struct block_device *bdev,
> + enum lsm_intgr_type type, const void *value, size_t size)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 9965b5c50df4..eaff8868766a 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -83,6 +83,10 @@ enum lsm_event {
> LSM_POLICY_CHANGE,
> };
>
> +enum lsm_intgr_type {
> + __LSM_INTGR_MAX
> +};
> +
> /*
> * These are reasons that can be passed to the security_locked_down()
> * LSM hook. Lockdown reasons that protect kernel integrity (ie, the
> @@ -511,6 +515,9 @@ int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len,
> void *val, size_t val_len, u64 id, u64 flags);
> int security_bdev_alloc(struct block_device *bdev);
> void security_bdev_free(struct block_device *bdev);
> +int security_bdev_setintegrity(struct block_device *bdev,
> + enum lsm_intgr_type type, const void *value,
> + size_t size);
> #else /* CONFIG_SECURITY */
>
> static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
> @@ -1495,6 +1502,13 @@ static inline void security_bdev_free(struct block_device *bdev)
> {
> }
>
> +static inline int security_bdev_setintegrity(struct block_device *bdev,
> + enum lsm_intgr_type, type,
> + 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 4274bbee40d0..8d88529ac904 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -5637,6 +5637,34 @@ void security_bdev_free(struct block_device *bdev)
> }
> EXPORT_SYMBOL(security_bdev_free);
>
> +/**
> + * security_bdev_setintegrity() - Set the bdev's integrity data
Let's just say "Set the device's integrity data" and not ask people to
figure out "bdev", although I will admit it should be fairly obvious :)
> + * @bdev: block device
> + * @type: type of integrity, e.g. hash digest, signature, etc
> + * @value: the integrity value
> + * @size: size of the integrity value
> + *
> + * Register a verified integrity measurement of a bdev with the LSM.
> + *
> + * Return: Returns 0 on success, negative values on failure.
> + */
> +int security_bdev_setintegrity(struct block_device *bdev,
> + enum lsm_intgr_type type, const void *value,
> + size_t size)
> +{
> + int rc = 0;
> + struct security_hook_list *p;
> +
> + hlist_for_each_entry(p, &security_hook_heads.bdev_setintegrity, list) {
> + rc = p->hook.bdev_setintegrity(bdev, type, value, size);
> + if (rc)
> + return rc;
> + }
> +
> + return LSM_RET_DEFAULT(bdev_setintegrity);
We can just use the call_int_hook() macro here instead of open coding
everything, right?
> +}
> +EXPORT_SYMBOL(security_bdev_setintegrity);
> +
> #ifdef CONFIG_PERF_EVENTS
> /**
> * security_perf_event_open() - Check if a perf event open is allowed
> --
> 2.44.0
--
paul-moore.com
On Mar 15, 2024 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 adds two security hook calls in dm-verity to save the
> dm-verity roothash and the roothash signature to the block device's
> LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
> which will be introduced in the next commit.
>
> 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
>
> v12:
> + No changes
>
> v13:
> + No changes
>
> v14:
> + Correct code format
> + Remove unnecessary header and switch to dm_disk()
>
> v15:
> + Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
> + Remove unnecessary headers
> ---
> drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
> drivers/md/dm-verity.h | 6 +++
> include/linux/dm-verity.h | 12 ++++++
> include/linux/security.h | 2 +
> 4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -22,6 +22,8 @@
> #include <linux/scatterlist.h>
> #include <linux/string.h>
> #include <linux/jump_label.h>
> +#include <linux/security.h>
> +#include <linux/dm-verity.h>
>
> #define DM_MSG_PREFIX "verity"
>
> @@ -1017,6 +1019,38 @@ 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 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;
Either you meant to copy @sig into @v->root_digest_sig and forgot to
add the code for that, or we don't need to include @sig as a parameter
to this function. I'm guessing it is the former as it wouldn't make
sense to even have dm_verity::root_digest_sig if we weren't stashing
it here.
I'd also suggest looking at kmemdup() instead of a kmalloc()/memcpy()
combo.
> + return 0;
> +}
> +
> +static void verity_free_sig(struct dm_verity *v)
> +{
> + kfree(v->root_digest_sig);
> +}
> +#else
> +
> +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> + size_t sig_size)
> +{
> + return 0;
> +}
> +
> +static inline void verity_free_sig(struct dm_verity *v)
> +{
> +}
> +
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
It's been a while since I looked at this patch in the patchset, so
maybe I'm missing something, but in general we don't want CONFIG_XXX
checks in the kernel, outside of security/, that are specific to a
particular LSM (what happens when multiple LSMs need this?). Please
use CONFIG_SECURITY instead.
> static void verity_dtr(struct dm_target *ti)
> {
> struct dm_verity *v = ti->private;
> @@ -1035,6 +1069,7 @@ 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);
> @@ -1434,6 +1469,13 @@ 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);
>
> @@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
> + root_digest.digest = v->root_digest;
> + root_digest.digest_len = v->digest_size;
> + root_digest.alg = v->alg_name;
> +
> + r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
> + sizeof(root_digest));
> + if (r)
> + return r;
> +
> + return security_bdev_setintegrity(bdev,
> + LSM_INTGR_DMV_SIG,
> + v->root_digest_sig,
> + v->sig_size);
What happens if the second call fails, should we clear the
LSM_INTGR_DMV_ROOTHASH state in the LSM?
> +}
> +
> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
See my comments about CONFIG_SECURITY above. In fact, I would suggest
moving this up into that part of the file so you only need one #ifdef
block relating to CONFIG_SECURITY.
I would also recommend making a dummy function so we can get rid of
the conditional compilation in @verity_target below. For example:
#ifdef CONFIG_SECURITY
static int verity_finalize(struct dm_target *ti)
{
/* real implementation */
}
#else
static int verity_finalize(struct dm_target *ti)
{
return 0;
}
#endif /* CONFIG_SECURITY */
> static struct target_type verity_target = {
> .name = "verity",
> .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> @@ -1596,6 +1666,9 @@ 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);
If you create a dummy verity_finalize() function like above you can
get rid of the #ifdef checks.
> diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
> index 20b1bcf03474..6a5b8df5bafd 100644
> --- a/drivers/md/dm-verity.h
> +++ b/drivers/md/dm-verity.h
> @@ -43,6 +43,9 @@ 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 */
> @@ -56,6 +59,9 @@ struct dm_verity {
> bool hash_failed:1; /* set if hash of any block failed */
> bool use_bh_wq:1; /* try to verify in BH wq before normal 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 */
See the previous comments about CONFIG_SECURITY.
> diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
> new file mode 100644
> index 000000000000..a799a8043d85
> --- /dev/null
> +++ b/include/linux/dm-verity.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _LINUX_DM_VERITY_H
> +#define _LINUX_DM_VERITY_H
> +
> +struct dm_verity_digest {
> + const char *alg;
> + const u8 *digest;
> + size_t digest_len;
> +};
> +
> +#endif /* _LINUX_DM_VERITY_H */
> diff --git a/include/linux/security.h b/include/linux/security.h
> index eaff8868766a..60b40b523d57 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -84,6 +84,8 @@ enum lsm_event {
> };
>
> enum lsm_intgr_type {
> + LSM_INTGR_DMV_SIG,
> + LSM_INTGR_DMV_ROOTHASH,
> __LSM_INTGR_MAX
> };
>
> --
> 2.44.0
--
paul-moore.com
On Mar 15, 2024 Fan Wu <[email protected]> wrote:
>
> This patch introduces a new hook to save inode's integrity
> data. For example, for fsverity enabled files, LSMs can use this hook to save
> the verified fsverity builtin signature into the inode's security blob,
> and LSMs can make access decisions based on the data inside the signature,
> like the signer certificate.
>
> Signed-off-by: Fan Wu <[email protected]>
>
> --
> v1-v14:
> + Not present
>
> v15:
> + Introduced
>
> ---
> include/linux/lsm_hook_defs.h | 3 +++
> include/linux/security.h | 10 ++++++++++
> security/security.c | 28 ++++++++++++++++++++++++++++
> 3 files changed, 41 insertions(+)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 6808ae763913..c88587fc3691 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -177,6 +177,9 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
> LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
> LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
> LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)
> +LSM_HOOK(int, 0, inode_setintegrity, struct inode *inode,
> + enum lsm_intgr_type type, const void *value, size_t size)
> +
> LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
> struct kernfs_node *kn)
> LSM_HOOK(int, 0, file_permission, struct file *file, int mask)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 60b40b523d57..0885866b261e 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -405,6 +405,9 @@ int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer
> void security_inode_getsecid(struct inode *inode, u32 *secid);
> int security_inode_copy_up(struct dentry *src, struct cred **new);
> int security_inode_copy_up_xattr(const char *name);
> +int security_inode_setintegrity(struct inode *inode,
> + enum lsm_intgr_type type, const void *value,
> + size_t size);
> int security_kernfs_init_security(struct kernfs_node *kn_dir,
> struct kernfs_node *kn);
> int security_file_permission(struct file *file, int mask);
> @@ -1021,6 +1024,13 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new)
> return 0;
> }
>
> +static inline int security_inode_setintegrity(struct inode *inode,
> + enum lsm_intgr_type, type,
> + const void *value, size_t size)
> +{
> + return 0;
> +}
> +
> static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
> struct kernfs_node *kn)
> {
> diff --git a/security/security.c b/security/security.c
> index 8d88529ac904..c5d426d084ab 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2681,6 +2681,34 @@ int security_inode_copy_up_xattr(const char *name)
> }
> EXPORT_SYMBOL(security_inode_copy_up_xattr);
>
> +/**
> + * security_inode_setintegrity() - Set the inode's integrity data
> + * @inode: inode
> + * @type: type of integrity, e.g. hash digest, signature, etc
> + * @value: the integrity value
> + * @size: size of the integrity value
> + *
> + * Register a verified integrity measurement of a inode with the LSM.
> + *
> + * Return: Returns 0 on success, negative values on failure.
> + */
> +int security_inode_setintegrity(struct inode *inode,
> + enum lsm_intgr_type type, const void *value,
> + size_t size)
> +{
> + int rc = 0;
> + struct security_hook_list *p;
> +
> + hlist_for_each_entry(p, &security_hook_heads.inode_setintegrity, list) {
> + rc = p->hook.inode_setintegrity(inode, type, value, size);
> + if (rc)
> + return rc;
> + }
> +
> + return LSM_RET_DEFAULT(inode_setintegrity);
> +}
> +EXPORT_SYMBOL(security_inode_setintegrity);
Same as the block device variant of this hook, we should convert this
to use the call_int_hook() macro unless there is a strong reason to
leave it open coded.
> /**
> * security_kernfs_init_security() - Init LSM context for a kernfs node
> * @kn_dir: parent kernfs node
> --
> 2.44.0
--
paul-moore.com
On Mon, Mar 18, 2024 at 1:29 AM Eric Biggers <[email protected]> wrote:
> On Fri, Mar 15, 2024 at 08:35:47PM -0700, Fan Wu wrote:
> > fsverity represents a mechanism to support both integrity and
> > authenticity protection of a file, supporting both signed and unsigned
> > digests.
..
> > diff --git a/fs/verity/signature.c b/fs/verity/signature.c
> > index 90c07573dd77..d4ed03a114e9 100644
> > --- a/fs/verity/signature.c
> > +++ b/fs/verity/signature.c
> > @@ -41,7 +41,10 @@ static struct key *fsverity_keyring;
> > * @sig_size: size of signature in bytes, or 0 if no signature
> > *
> > * If the file includes a signature of its fs-verity file digest, verify it
> > - * against the certificates in the fs-verity keyring.
> > + * against the certificates in the fs-verity keyring. Note that verification
> > + * happens as long as the file's signature exists regardless of the state of
> > + * fsverity_require_signatures, and the IPE LSM relies on this behavior
> > + * to save the verified file signature of the file into security blobs.
>
> "save the verified file signature of the file into security blobs" isn't what
> IPE actually does, though. And even if it was, it would not explain why IPE
> expects the signature to be verified.
We probably need to abstract away the IPE specific comments here as
these are general LSM hooks and could be used by additional LSMs in
the future. How about something like the following?
"Note that signatures are verified regardless of the state of the
'fsverity_require_signatures' variable and the LSM subsystem relies
on this behavior to help enforce file integrity policies. Please
discuss changes with the LSM list (thank you!)."
> > diff --git a/include/linux/security.h b/include/linux/security.h
> > index 0885866b261e..edd12c0a673a 100644
> > --- a/include/linux/security.h
> > +++ b/include/linux/security.h
> > @@ -86,6 +86,7 @@ enum lsm_event {
> > enum lsm_intgr_type {
> > LSM_INTGR_DMV_SIG,
> > LSM_INTGR_DMV_ROOTHASH,
> > + LSM_INTGR_FSV_SIG,
> > __LSM_INTGR_MAX
> > };
>
> These are hard to understand because they are abbreviated too much. And again,
> there are multiple type of fsverity signatures. How about:
>
> enum lsm_integrity_type {
> LSM_INTEGRITY_DM_VERITY_SIG,
> LSM_INTEGRITY_DM_VERITY_ROOT_HASH,
> LSM_INTEGRITY_FS_VERITY_BUILTIN_SIG,
> __LSM_INTEGRITY_MAX
> };
Ugh. I'm willing to concede that the existing enums are probably a
bit too terse, but the suggestions above are a bit too long for my
tastes (and my typin' fingers). How about a compromise like that
below?
enum lsm_integrity_type {
LSM_INT_DMVERITY_SIG,
LSM_INT_DMVERITY_ROOTHASH,
LSM_INT_FSVERITY_BUILTINSIG,
};
--
paul-moore.com
On Tue, Mar 19 2024 at 7:00P -0400,
Paul Moore <[email protected]> wrote:
> On Mar 15, 2024 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 adds two security hook calls in dm-verity to save the
> > dm-verity roothash and the roothash signature to the block device's
> > LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
> > which will be introduced in the next commit.
> >
> > 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
> >
> > v12:
> > + No changes
> >
> > v13:
> > + No changes
> >
> > v14:
> > + Correct code format
> > + Remove unnecessary header and switch to dm_disk()
> >
> > v15:
> > + Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
> > + Remove unnecessary headers
> > ---
> > drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
> > drivers/md/dm-verity.h | 6 +++
> > include/linux/dm-verity.h | 12 ++++++
> > include/linux/security.h | 2 +
> > 4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
> > --- a/drivers/md/dm-verity-target.c
> > +++ b/drivers/md/dm-verity-target.c
> > @@ -22,6 +22,8 @@
> > #include <linux/scatterlist.h>
> > #include <linux/string.h>
> > #include <linux/jump_label.h>
> > +#include <linux/security.h>
> > +#include <linux/dm-verity.h>
> >
> > #define DM_MSG_PREFIX "verity"
> >
> > @@ -1017,6 +1019,38 @@ 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 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;
>
> Either you meant to copy @sig into @v->root_digest_sig and forgot to
> add the code for that, or we don't need to include @sig as a parameter
> to this function. I'm guessing it is the former as it wouldn't make
> sense to even have dm_verity::root_digest_sig if we weren't stashing
> it here.
>
> I'd also suggest looking at kmemdup() instead of a kmalloc()/memcpy()
> combo.
>
> > + return 0;
> > +}
> > +
> > +static void verity_free_sig(struct dm_verity *v)
> > +{
> > + kfree(v->root_digest_sig);
> > +}
> > +#else
> > +
> > +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> > + size_t sig_size)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void verity_free_sig(struct dm_verity *v)
> > +{
> > +}
> > +
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> It's been a while since I looked at this patch in the patchset, so
> maybe I'm missing something, but in general we don't want CONFIG_XXX
> checks in the kernel, outside of security/, that are specific to a
> particular LSM (what happens when multiple LSMs need this?). Please
> use CONFIG_SECURITY instead.
>
> > static void verity_dtr(struct dm_target *ti)
> > {
> > struct dm_verity *v = ti->private;
> > @@ -1035,6 +1069,7 @@ 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);
> > @@ -1434,6 +1469,13 @@ 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);
> >
> > @@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
> > + root_digest.digest = v->root_digest;
> > + root_digest.digest_len = v->digest_size;
> > + root_digest.alg = v->alg_name;
> > +
> > + r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
> > + sizeof(root_digest));
> > + if (r)
> > + return r;
> > +
> > + return security_bdev_setintegrity(bdev,
> > + LSM_INTGR_DMV_SIG,
> > + v->root_digest_sig,
> > + v->sig_size);
>
> What happens if the second call fails, should we clear the
> LSM_INTGR_DMV_ROOTHASH state in the LSM?
>
> > +}
> > +
> > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> See my comments about CONFIG_SECURITY above. In fact, I would suggest
> moving this up into that part of the file so you only need one #ifdef
> block relating to CONFIG_SECURITY.
>
> I would also recommend making a dummy function so we can get rid of
> the conditional compilation in @verity_target below. For example:
>
> #ifdef CONFIG_SECURITY
> static int verity_finalize(struct dm_target *ti)
> {
> /* real implementation */
> }
> #else
> static int verity_finalize(struct dm_target *ti)
> {
> return 0;
> }
> #endif /* CONFIG_SECURITY */
>
> > static struct target_type verity_target = {
> > .name = "verity",
> > .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> > @@ -1596,6 +1666,9 @@ 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);
>
> If you create a dummy verity_finalize() function like above you can
> get rid of the #ifdef checks.
Think it is better to leave it as-is, to avoid calling the .finalize
hook if it isn't actually needed.
Mike
On Wed Mar 20, 2024 at 1:00 AM EET, Paul Moore wrote:
> On Mar 15, 2024 Fan Wu <[email protected]> wrote:
> >
> > This patch introduces a new hook to save block device's integrity
> > data. For example, for dm-verity, LSMs can use this hook to save
> > the roothash signature of a dm-verity into the security blob,
> > and LSMs can make access decisions based on the data inside
> > the signature, like the signer certificate.
> >
> > Signed-off-by: Fan Wu <[email protected]>
> >
> > --
> > v1-v14:
> > + Not present
> >
> > v15:
> > + Introduced
> >
> > ---
> > include/linux/lsm_hook_defs.h | 2 ++
> > include/linux/security.h | 14 ++++++++++++++
> > security/security.c | 28 ++++++++++++++++++++++++++++
> > 3 files changed, 44 insertions(+)
>
> I'm not sure why you made this a separate patch, help? If there is
> no significant reason why this is separate, please squash it together
> with patch 11/21.
Off-topic: it is weird to have *RFC* patch set at v15.
RFC by de-facto is something that can be safely ignored if you don't
have bandwidth. 15 versions of anything that can be safely ignored
is by definition spamming :-) I mean just conceptually.
So does the RFC still hold or what the heck is going on with this one?
Haven't followed for some time now...
BR, Jarkko
On Wed Mar 20, 2024 at 10:28 AM EET, Jarkko Sakkinen wrote:
> On Wed Mar 20, 2024 at 1:00 AM EET, Paul Moore wrote:
> > On Mar 15, 2024 Fan Wu <[email protected]> wrote:
> > >
> > > This patch introduces a new hook to save block device's integrity
> > > data. For example, for dm-verity, LSMs can use this hook to save
> > > the roothash signature of a dm-verity into the security blob,
> > > and LSMs can make access decisions based on the data inside
> > > the signature, like the signer certificate.
> > >
> > > Signed-off-by: Fan Wu <[email protected]>
> > >
> > > --
> > > v1-v14:
> > > + Not present
> > >
> > > v15:
> > > + Introduced
> > >
> > > ---
> > > include/linux/lsm_hook_defs.h | 2 ++
> > > include/linux/security.h | 14 ++++++++++++++
> > > security/security.c | 28 ++++++++++++++++++++++++++++
> > > 3 files changed, 44 insertions(+)
> >
> > I'm not sure why you made this a separate patch, help? If there is
> > no significant reason why this is separate, please squash it together
> > with patch 11/21.
>
> Off-topic: it is weird to have *RFC* patch set at v15.
>
> RFC by de-facto is something that can be safely ignored if you don't
> have bandwidth. 15 versions of anything that can be safely ignored
> is by definition spamming :-) I mean just conceptually.
>
> So does the RFC still hold or what the heck is going on with this one?
>
> Haven't followed for some time now...
I mean if this RFC trend continues I'll just put auto-filter for this
thread to put straight to the bin. There's enough non-RFC patch sets
to review.
BR, Jarkko
On Tue, Mar 19, 2024 at 10:19 PM Mike Snitzer <[email protected]> wrote:
> On Tue, Mar 19 2024 at 7:00P -0400,
> Paul Moore <[email protected]> wrote:
> > On Mar 15, 2024 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 adds two security hook calls in dm-verity to save the
> > > dm-verity roothash and the roothash signature to the block device's
> > > LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
> > > which will be introduced in the next commit.
> > >
> > > 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
> > >
> > > v12:
> > > + No changes
> > >
> > > v13:
> > > + No changes
> > >
> > > v14:
> > > + Correct code format
> > > + Remove unnecessary header and switch to dm_disk()
> > >
> > > v15:
> > > + Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
> > > + Remove unnecessary headers
> > > ---
> > > drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
> > > drivers/md/dm-verity.h | 6 +++
> > > include/linux/dm-verity.h | 12 ++++++
> > > include/linux/security.h | 2 +
> > > 4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
> > > --- a/drivers/md/dm-verity-target.c
> > > +++ b/drivers/md/dm-verity-target.c
> > > @@ -22,6 +22,8 @@
> > > #include <linux/scatterlist.h>
> > > #include <linux/string.h>
> > > #include <linux/jump_label.h>
> > > +#include <linux/security.h>
> > > +#include <linux/dm-verity.h>
> > >
> > > #define DM_MSG_PREFIX "verity"
> > >
> > > @@ -1017,6 +1019,38 @@ 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 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;
> >
> > Either you meant to copy @sig into @v->root_digest_sig and forgot to
> > add the code for that, or we don't need to include @sig as a parameter
> > to this function. I'm guessing it is the former as it wouldn't make
> > sense to even have dm_verity::root_digest_sig if we weren't stashing
> > it here.
> >
> > I'd also suggest looking at kmemdup() instead of a kmalloc()/memcpy()
> > combo.
> >
> > > + return 0;
> > > +}
> > > +
> > > +static void verity_free_sig(struct dm_verity *v)
> > > +{
> > > + kfree(v->root_digest_sig);
> > > +}
> > > +#else
> > > +
> > > +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> > > + size_t sig_size)
> > > +{
> > > + return 0;
> > > +}
> > > +
> > > +static inline void verity_free_sig(struct dm_verity *v)
> > > +{
> > > +}
> > > +
> > > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> >
> > It's been a while since I looked at this patch in the patchset, so
> > maybe I'm missing something, but in general we don't want CONFIG_XXX
> > checks in the kernel, outside of security/, that are specific to a
> > particular LSM (what happens when multiple LSMs need this?). Please
> > use CONFIG_SECURITY instead.
> >
> > > static void verity_dtr(struct dm_target *ti)
> > > {
> > > struct dm_verity *v = ti->private;
> > > @@ -1035,6 +1069,7 @@ 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);
> > > @@ -1434,6 +1469,13 @@ 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);
> > >
> > > @@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
> > > + root_digest.digest = v->root_digest;
> > > + root_digest.digest_len = v->digest_size;
> > > + root_digest.alg = v->alg_name;
> > > +
> > > + r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
> > > + sizeof(root_digest));
> > > + if (r)
> > > + return r;
> > > +
> > > + return security_bdev_setintegrity(bdev,
> > > + LSM_INTGR_DMV_SIG,
> > > + v->root_digest_sig,
> > > + v->sig_size);
> >
> > What happens if the second call fails, should we clear the
> > LSM_INTGR_DMV_ROOTHASH state in the LSM?
> >
> > > +}
> > > +
> > > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> >
> > See my comments about CONFIG_SECURITY above. In fact, I would suggest
> > moving this up into that part of the file so you only need one #ifdef
> > block relating to CONFIG_SECURITY.
> >
> > I would also recommend making a dummy function so we can get rid of
> > the conditional compilation in @verity_target below. For example:
> >
> > #ifdef CONFIG_SECURITY
> > static int verity_finalize(struct dm_target *ti)
> > {
> > /* real implementation */
> > }
> > #else
> > static int verity_finalize(struct dm_target *ti)
> > {
> > return 0;
> > }
> > #endif /* CONFIG_SECURITY */
> >
> > > static struct target_type verity_target = {
> > > .name = "verity",
> > > .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> > > @@ -1596,6 +1666,9 @@ 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);
> >
> > If you create a dummy verity_finalize() function like above you can
> > get rid of the #ifdef checks.
>
> Think it is better to leave it as-is, to avoid calling the .finalize
> hook if it isn't actually needed.
Fair enough, my personal preference is to minimize Kconfig conditional
code flow changes such as this, but I understand your point of view
and device-mapper is your code after all.
I believe the other issues still need to be addressed, but other than
that are you generally okay with the new "finalize" hook approach?
--
paul-moore.com
On 3/19/2024 4:00 PM, Paul Moore wrote:
> On Mar 15, 2024 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 adds two security hook calls in dm-verity to save the
>> dm-verity roothash and the roothash signature to the block device's
>> LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
>> which will be introduced in the next commit.
>>
>> 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
>>
>> v12:
>> + No changes
>>
>> v13:
>> + No changes
>>
>> v14:
>> + Correct code format
>> + Remove unnecessary header and switch to dm_disk()
>>
>> v15:
>> + Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
>> + Remove unnecessary headers
>> ---
>> drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
>> drivers/md/dm-verity.h | 6 +++
>> include/linux/dm-verity.h | 12 ++++++
>> include/linux/security.h | 2 +
>> 4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
>> --- a/drivers/md/dm-verity-target.c
>> +++ b/drivers/md/dm-verity-target.c
>> @@ -22,6 +22,8 @@
>> #include <linux/scatterlist.h>
>> #include <linux/string.h>
>> #include <linux/jump_label.h>
>> +#include <linux/security.h>
>> +#include <linux/dm-verity.h>
>>
>> #define DM_MSG_PREFIX "verity"
>>
>> @@ -1017,6 +1019,38 @@ 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 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;
>
> Either you meant to copy @sig into @v->root_digest_sig and forgot to
> add the code for that, or we don't need to include @sig as a parameter
> to this function. I'm guessing it is the former as it wouldn't make
> sense to even have dm_verity::root_digest_sig if we weren't stashing
> it here.
>
> I'd also suggest looking at kmemdup() instead of a kmalloc()/memcpy()
> combo.
>
Sorry, my mistake here. I must have thought I wrote kmemdup(). I will
fix this.
>> + return 0;
>> +}
>> +
>> +static void verity_free_sig(struct dm_verity *v)
>> +{
>> + kfree(v->root_digest_sig);
>> +}
>> +#else
>> +
>> +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
>> + size_t sig_size)
>> +{
>> + return 0;
>> +}
>> +
>> +static inline void verity_free_sig(struct dm_verity *v)
>> +{
>> +}
>> +
>> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> It's been a while since I looked at this patch in the patchset, so
> maybe I'm missing something, but in general we don't want CONFIG_XXX
> checks in the kernel, outside of security/, that are specific to a
> particular LSM (what happens when multiple LSMs need this?). Please
> use CONFIG_SECURITY instead.
>
>> static void verity_dtr(struct dm_target *ti)
>> {
>> struct dm_verity *v = ti->private;
>> @@ -1035,6 +1069,7 @@ 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);
>> @@ -1434,6 +1469,13 @@ 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);
>>
>> @@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
>> + root_digest.digest = v->root_digest;
>> + root_digest.digest_len = v->digest_size;
>> + root_digest.alg = v->alg_name;
>> +
>> + r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
>> + sizeof(root_digest));
>> + if (r)
>> + return r;
>> +
>> + return security_bdev_setintegrity(bdev,
>> + LSM_INTGR_DMV_SIG,
>> + v->root_digest_sig,
>> + v->sig_size);
>
> What happens if the second call fails, should we clear the
> LSM_INTGR_DMV_ROOTHASH state in the LSM?
>
Yes, we should also clear the ROOTHASH if the second failed. Probably we
can pass NULL to security_bdev_setintegrity to clear it like
security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, NULL, 0);
-Fan
>> +}
>> +
>> +#endif /* CONFIG_IPE_PROP_DM_VERITY */
>
> See my comments about CONFIG_SECURITY above. In fact, I would suggest
> moving this up into that part of the file so you only need one #ifdef
> block relating to CONFIG_SECURITY.
>
> I would also recommend making a dummy function so we can get rid of
> the conditional compilation in @verity_target below. For example:
>
> #ifdef CONFIG_SECURITY
> static int verity_finalize(struct dm_target *ti)
> {
> /* real implementation */
> }
> #else
> static int verity_finalize(struct dm_target *ti)
> {
> return 0;
> }
> #endif /* CONFIG_SECURITY */
>
>> static struct target_type verity_target = {
>> .name = "verity",
>> .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
>> @@ -1596,6 +1666,9 @@ 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);
>
> If you create a dummy verity_finalize() function like above you can
> get rid of the #ifdef checks.
>
>> diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h
>> index 20b1bcf03474..6a5b8df5bafd 100644
>> --- a/drivers/md/dm-verity.h
>> +++ b/drivers/md/dm-verity.h
>> @@ -43,6 +43,9 @@ 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 */
>> @@ -56,6 +59,9 @@ struct dm_verity {
>> bool hash_failed:1; /* set if hash of any block failed */
>> bool use_bh_wq:1; /* try to verify in BH wq before normal 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 */
>
> See the previous comments about CONFIG_SECURITY.
>
>> diff --git a/include/linux/dm-verity.h b/include/linux/dm-verity.h
>> new file mode 100644
>> index 000000000000..a799a8043d85
>> --- /dev/null
>> +++ b/include/linux/dm-verity.h
>> @@ -0,0 +1,12 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +
>> +#ifndef _LINUX_DM_VERITY_H
>> +#define _LINUX_DM_VERITY_H
>> +
>> +struct dm_verity_digest {
>> + const char *alg;
>> + const u8 *digest;
>> + size_t digest_len;
>> +};
>> +
>> +#endif /* _LINUX_DM_VERITY_H */
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index eaff8868766a..60b40b523d57 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -84,6 +84,8 @@ enum lsm_event {
>> };
>>
>> enum lsm_intgr_type {
>> + LSM_INTGR_DMV_SIG,
>> + LSM_INTGR_DMV_ROOTHASH,
>> __LSM_INTGR_MAX
>> };
>>
>> --
>> 2.44.0
>
> --
> paul-moore.com
On Wed, Mar 20 2024 at 1:23P -0400,
Paul Moore <[email protected]> wrote:
> On Tue, Mar 19, 2024 at 10:19 PM Mike Snitzer <[email protected]> wrote:
> > On Tue, Mar 19 2024 at 7:00P -0400,
> > Paul Moore <[email protected]> wrote:
> > > On Mar 15, 2024 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 adds two security hook calls in dm-verity to save the
> > > > dm-verity roothash and the roothash signature to the block device's
> > > > LSM blobs. The hook calls are depended on CONFIG_IPE_PROP_DM_VERITY,
> > > > which will be introduced in the next commit.
> > > >
> > > > 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
> > > >
> > > > v12:
> > > > + No changes
> > > >
> > > > v13:
> > > > + No changes
> > > >
> > > > v14:
> > > > + Correct code format
> > > > + Remove unnecessary header and switch to dm_disk()
> > > >
> > > > v15:
> > > > + Refactor security_bdev_setsecurity() to security_bdev_setintegrity()
> > > > + Remove unnecessary headers
> > > > ---
> > > > drivers/md/dm-verity-target.c | 73 +++++++++++++++++++++++++++++++++++
> > > > drivers/md/dm-verity.h | 6 +++
> > > > include/linux/dm-verity.h | 12 ++++++
> > > > include/linux/security.h | 2 +
> > > > 4 files changed, 93 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 bb5da66da4c1..e94cc6a755d5 100644
> > > > --- a/drivers/md/dm-verity-target.c
> > > > +++ b/drivers/md/dm-verity-target.c
> > > > @@ -22,6 +22,8 @@
> > > > #include <linux/scatterlist.h>
> > > > #include <linux/string.h>
> > > > #include <linux/jump_label.h>
> > > > +#include <linux/security.h>
> > > > +#include <linux/dm-verity.h>
> > > >
> > > > #define DM_MSG_PREFIX "verity"
> > > >
> > > > @@ -1017,6 +1019,38 @@ 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 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;
> > >
> > > Either you meant to copy @sig into @v->root_digest_sig and forgot to
> > > add the code for that, or we don't need to include @sig as a parameter
> > > to this function. I'm guessing it is the former as it wouldn't make
> > > sense to even have dm_verity::root_digest_sig if we weren't stashing
> > > it here.
> > >
> > > I'd also suggest looking at kmemdup() instead of a kmalloc()/memcpy()
> > > combo.
> > >
> > > > + return 0;
> > > > +}
> > > > +
> > > > +static void verity_free_sig(struct dm_verity *v)
> > > > +{
> > > > + kfree(v->root_digest_sig);
> > > > +}
> > > > +#else
> > > > +
> > > > +static inline int verity_init_sig(struct dm_verity *v, const void *sig,
> > > > + size_t sig_size)
> > > > +{
> > > > + return 0;
> > > > +}
> > > > +
> > > > +static inline void verity_free_sig(struct dm_verity *v)
> > > > +{
> > > > +}
> > > > +
> > > > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > >
> > > It's been a while since I looked at this patch in the patchset, so
> > > maybe I'm missing something, but in general we don't want CONFIG_XXX
> > > checks in the kernel, outside of security/, that are specific to a
> > > particular LSM (what happens when multiple LSMs need this?). Please
> > > use CONFIG_SECURITY instead.
> > >
> > > > static void verity_dtr(struct dm_target *ti)
> > > > {
> > > > struct dm_verity *v = ti->private;
> > > > @@ -1035,6 +1069,7 @@ 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);
> > > > @@ -1434,6 +1469,13 @@ 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);
> > > >
> > > > @@ -1584,6 +1626,34 @@ 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_disk(dm_table_get_md(ti->table))->part0;
> > > > + root_digest.digest = v->root_digest;
> > > > + root_digest.digest_len = v->digest_size;
> > > > + root_digest.alg = v->alg_name;
> > > > +
> > > > + r = security_bdev_setintegrity(bdev, LSM_INTGR_DMV_ROOTHASH, &root_digest,
> > > > + sizeof(root_digest));
> > > > + if (r)
> > > > + return r;
> > > > +
> > > > + return security_bdev_setintegrity(bdev,
> > > > + LSM_INTGR_DMV_SIG,
> > > > + v->root_digest_sig,
> > > > + v->sig_size);
> > >
> > > What happens if the second call fails, should we clear the
> > > LSM_INTGR_DMV_ROOTHASH state in the LSM?
> > >
> > > > +}
> > > > +
> > > > +#endif /* CONFIG_IPE_PROP_DM_VERITY */
> > >
> > > See my comments about CONFIG_SECURITY above. In fact, I would suggest
> > > moving this up into that part of the file so you only need one #ifdef
> > > block relating to CONFIG_SECURITY.
> > >
> > > I would also recommend making a dummy function so we can get rid of
> > > the conditional compilation in @verity_target below. For example:
> > >
> > > #ifdef CONFIG_SECURITY
> > > static int verity_finalize(struct dm_target *ti)
> > > {
> > > /* real implementation */
> > > }
> > > #else
> > > static int verity_finalize(struct dm_target *ti)
> > > {
> > > return 0;
> > > }
> > > #endif /* CONFIG_SECURITY */
> > >
> > > > static struct target_type verity_target = {
> > > > .name = "verity",
> > > > .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> > > > @@ -1596,6 +1666,9 @@ 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);
> > >
> > > If you create a dummy verity_finalize() function like above you can
> > > get rid of the #ifdef checks.
> >
> > Think it is better to leave it as-is, to avoid calling the .finalize
> > hook if it isn't actually needed.
>
> Fair enough, my personal preference is to minimize Kconfig conditional
> code flow changes such as this, but I understand your point of view
> and device-mapper is your code after all.
>
> I believe the other issues still need to be addressed,
Yes.
> but other than that are you generally okay with the new "finalize"
> hook approach?
I am, not seeing how we could avoid it.
Thanks,
Mike
On 3/20/2024 1:31 AM, Jarkko Sakkinen wrote:
> On Wed Mar 20, 2024 at 10:28 AM EET, Jarkko Sakkinen wrote:
>> On Wed Mar 20, 2024 at 1:00 AM EET, Paul Moore wrote:
>>> On Mar 15, 2024 Fan Wu <[email protected]> wrote:
>>>>
>>>> This patch introduces a new hook to save block device's integrity
>>>> data. For example, for dm-verity, LSMs can use this hook to save
>>>> the roothash signature of a dm-verity into the security blob,
>>>> and LSMs can make access decisions based on the data inside
>>>> the signature, like the signer certificate.
>>>>
>>>> Signed-off-by: Fan Wu <[email protected]>
>>>>
>>>> --
>>>> v1-v14:
>>>> + Not present
>>>>
>>>> v15:
>>>> + Introduced
>>>>
>>>> ---
>>>> include/linux/lsm_hook_defs.h | 2 ++
>>>> include/linux/security.h | 14 ++++++++++++++
>>>> security/security.c | 28 ++++++++++++++++++++++++++++
>>>> 3 files changed, 44 insertions(+)
>>>
>>> I'm not sure why you made this a separate patch, help? If there is
>>> no significant reason why this is separate, please squash it together
>>> with patch 11/21.
>>
>> Off-topic: it is weird to have *RFC* patch set at v15.
>>
>> RFC by de-facto is something that can be safely ignored if you don't
>> have bandwidth. 15 versions of anything that can be safely ignored
>> is by definition spamming :-) I mean just conceptually.
>>
>> So does the RFC still hold or what the heck is going on with this one?
>>
>> Haven't followed for some time now...
>
> I mean if this RFC trend continues I'll just put auto-filter for this
> thread to put straight to the bin. There's enough non-RFC patch sets
> to review.
>
> BR, Jarkko
Sorry about the confusion with the RFC tag – I wasn't fully aware of its
conventional meaning and how it's perceived in terms of importance and
urgency. Point taken, and I'll make sure to remove the RFC tag for
future submissions. Definitely not my intention to clog up the workflow
or seem like I'm spamming.
-Fan
On Wed Mar 20, 2024 at 10:31 PM EET, Fan Wu wrote:
>
>
> On 3/20/2024 1:31 AM, Jarkko Sakkinen wrote:
> > On Wed Mar 20, 2024 at 10:28 AM EET, Jarkko Sakkinen wrote:
> >> On Wed Mar 20, 2024 at 1:00 AM EET, Paul Moore wrote:
> >>> On Mar 15, 2024 Fan Wu <[email protected]> wrote:
> >>>>
> >>>> This patch introduces a new hook to save block device's integrity
> >>>> data. For example, for dm-verity, LSMs can use this hook to save
> >>>> the roothash signature of a dm-verity into the security blob,
> >>>> and LSMs can make access decisions based on the data inside
> >>>> the signature, like the signer certificate.
> >>>>
> >>>> Signed-off-by: Fan Wu <[email protected]>
> >>>>
> >>>> --
> >>>> v1-v14:
> >>>> + Not present
> >>>>
> >>>> v15:
> >>>> + Introduced
> >>>>
> >>>> ---
> >>>> include/linux/lsm_hook_defs.h | 2 ++
> >>>> include/linux/security.h | 14 ++++++++++++++
> >>>> security/security.c | 28 ++++++++++++++++++++++++++++
> >>>> 3 files changed, 44 insertions(+)
> >>>
> >>> I'm not sure why you made this a separate patch, help? If there is
> >>> no significant reason why this is separate, please squash it together
> >>> with patch 11/21.
> >>
> >> Off-topic: it is weird to have *RFC* patch set at v15.
> >>
> >> RFC by de-facto is something that can be safely ignored if you don't
> >> have bandwidth. 15 versions of anything that can be safely ignored
> >> is by definition spamming :-) I mean just conceptually.
> >>
> >> So does the RFC still hold or what the heck is going on with this one?
> >>
> >> Haven't followed for some time now...
> >
> > I mean if this RFC trend continues I'll just put auto-filter for this
> > thread to put straight to the bin. There's enough non-RFC patch sets
> > to review.
> >
> > BR, Jarkko
>
> Sorry about the confusion with the RFC tag – I wasn't fully aware of its
> conventional meaning and how it's perceived in terms of importance and
> urgency. Point taken, and I'll make sure to remove the RFC tag for
> future submissions. Definitely not my intention to clog up the workflow
> or seem like I'm spamming.
OK cool! Just wanted to point this out also because it already looks
good enough not to be considered as RFC in my eyes :-) If you keep RFC
it is by definition "look into if you have the bandwidth but please
do not take this to mainline". No means to nitpick here...
BR, Jarkko
On Sun, Mar 17, 2024 at 8:29 PM Casey Schaufler <casey@schaufler-cacom> wrote:
> On 3/15/2024 8:35 PM, Fan Wu wrote:
> > This patch introduces a new hook to notify security system that the
> > content of initramfs has been unpacked into the rootfs.
> >
> > Upon receiving this notification, the security system can activate
> > a policy to allow only files that originated from the initramfs to
> > execute or load into kernel during the early stages of booting.
> >
> > This approach is crucial for minimizing the attack surface by
> > ensuring that only trusted files from the initramfs are operational
> > in the critical boot phase.
> >
> > Signed-off-by: Fan Wu <[email protected]>
> >
> > ---
> > v1-v11:
> > + Not present
> >
> > v12:
> > + Introduced
> >
> > v13:
> > + Rename the hook name to initramfs_populated()
> >
> > v14:
> > + No changes
> >
> > v15:
> > + No changes
> > ---
> > include/linux/lsm_hook_defs.h | 2 ++
> > include/linux/security.h | 8 ++++++++
> > init/initramfs.c | 3 +++
> > security/security.c | 10 ++++++++++
> > 4 files changed, 23 insertions(+)
> >
> > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> > index 334e00efbde4..7db99ae75651 100644
> > --- a/include/linux/lsm_hook_defs.h
> > +++ b/include/linux/lsm_hook_defs.h
> > @@ -450,3 +450,5 @@ 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(void, LSM_RET_VOID, initramfs_populated, void)
>
> This is an awfully expensive way to set a flag. Adding a LSM hook list
> isn't free. Isn't there a way to capture this state change through one of
> the mount hooks?
Unfortunately no, the initramfs isn't mounted like a traditional
filesystem, it is "populated" by unpacking the cpio into the initramfs
at early boot. This LSM hook should be called exactly once during
boot, and the performance impact should be minimal; I should also be
wildly more performant than earlier revisions of this patchset that
required grabbing a single spinlock on every file access.
Of course if you have an idea on how this could be done
differently/better I think we're all open to new ideas ...
--
paul-moore.com