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From:   Topi Miettinen <toiwoton@gmail.com>
Subject: Re: [PATCH v24 00/25] LSM: Module stacking for AppArmor
To:     Casey Schaufler <casey@schaufler-ca.com>,
        casey.schaufler@intel.com, jmorris@namei.org,
        linux-security-module@vger.kernel.org, selinux@vger.kernel.org
Cc:     linux-audit@redhat.com, keescook@chromium.org,
        john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp,
        paul@paul-moore.com, sds@tycho.nsa.gov,
        linux-kernel@vger.kernel.org
References: <20210126164108.1958-1-casey.ref@schaufler-ca.com>
 <20210126164108.1958-1-casey@schaufler-ca.com>
Message-ID: <31ba0fe7-afdf-8f7d-e7a7-8f15d8c690a4@gmail.com>
Date:   Tue, 2 Feb 2021 14:05:38 +0200
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On 26.1.2021 18.40, Casey Schaufler wrote:
> This patchset provides the changes required for
> the AppArmor security module to stack safely with any other.

In my test, when kernel command line has apparmor before selinux in lsm= 
entry, the boot is not successful with enforcing=1:
systemd[1]: Failed to compute init label, ignoring.
systemd[1]: Failed to set SELinux security context 
system_u:object_r:cgroup_t:s0 for /sys/fs/cgroup: Invalid argument
systemd[1]: Failed to set SELinux security context 
system_u:object_r:pstore_t:s0 for /sys/fs/pstore: Invalid argument
systemd[1]: Failed to set SELinux security context 
system_u:object_r:sysfs_t:s0 for /sys/firmware/efi/efivars: Invalid argument
...
Failed to drop capability bounding set of usermode helpers: Operation 
not permitted
Failed to drop capability bounding set of usermode helpers.
systemd[1]: Freezing execution.

Probably SELinux libraries can't find or set the labels for the PID1 or 
any file systems. Before the init label message, systemd calls 
getcon_raw(), getfilecon_raw(), string_to_security_class() and 
security_compute_create_raw(), so one of these don't understand the LSM 
stacking.

Also the policy needs updating to handle process2:setdisplay:
SELinux:  Permission setdisplay in class process2 not defined in policy.
SELinux: the above unknown classes and permissions will be denied

With enforcing=0, many services start, but for example systemd-journald 
doesn't. This is probably related to the earlier problem with labels 
(maybe libraries try to use SELinux labels where kernel wants AppArmor 
profiles):
systemd[1]: Failed to set SELinux security context 
system_u:object_r:init_runtime_t:s0 for 
/run/systemd/units/invocation:systemd-user-sessions.service: Invalid 
argument

Switching the order so that apparmor is after selinux, boot is 
successful. Loading AppArmor profiles needs a permission from SELinux:

Feb 02 08:53:15 audit[963]: AVC avc:  denied  { mac_admin } for  pid=963 
comm="apparmor_parser" capability=33 
scontext=system_u:system_r:initrc_t:s0 
tcontext=system_u:system_r:initrc_t:s0 tclass=capability2 permissive=0
Feb 02 08:53:15 audit[963]: AVC apparmor="STATUS" 
operation="profile_replace" info="not policy admin" error=-13 
profile="unconfined" pid=963 comm="apparmor_parser"
Feb 02 08:53:15 audit: AUDIT1420 
subj_selinux=system_u:system_r:initrc_t:s0 subj_apparmor==unconfined
Feb 02 08:53:15 audit[963]: SYSCALL arch=c000003e syscall=1 success=no 
exit=-13 a0=7 a1=7a8f2ff04f80 a2=1e09 a3=0 items=0 ppid=961 pid=963 
auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 
tty=(none) ses=4294967295 comm="apparmor_parser" 
exe="/usr/sbin/apparmor_parser" subj=? key=(null)
Feb 02 08:53:15 audit: PROCTITLE 
proctitle=2F7362696E2F61707061726D6F725F706172736572002D2D77726974652D6361636865002D2D7265706C616365002D2D002F6574632F61707061726D6F722E64
Feb 02 08:53:15 apparmor.systemd[963]: /sbin/apparmor_parser: Unable to 
replace "/lib/systemd/systemd-resolved".  Permission denied; attempted 
to load a profile while confined?

This just seems to need TE rules for the apparmor_parser.

Double equal sign in subj_apparmor==unconfined looks odd, should that be 
just one like subj_selinux?

Tools like ps, and KDE and Gnome System Monitors only show SELinux 
context, but it would be nice if MAC contexts for all enabled LSMs were 
shown.

-Topi

> 
> v24: Rebase to 5.11-rc1
>       Incorporate feedback from v23
>       - Address the IMA team's concerns about "label collisions".
>         A label collision occurs when there is ambiguity about
>         which of multiple LSMs is being targeted in the definition
>         of an integrity check rule.  A system with Smack and
>         AppArmor would be unable to distinguish which LSM is
>         important to an integrity rule referrencing the label
>         "unconfined" as that label is meaningful to both.
>         Provide a boot option to specify which LSM will be used in
>         IMA rules when multiple LSMs are present. (patch 04)
>         Pull LSM "slot" identification from later audit patches in
>         in support of this (patch 03).
>       - Pick up a few audit events that need to include supplimental
>         subject context records that had been missed in the
>         previous version.
> v23: Rebase to 5.10-rc4
>       Incorporate feedback from v22
>       - Change /proc/*/attr/display to /proc/*/attr/interface_lsm to
>         make the purpose clearer. (patch 0012)
>       - Include ABI documentation. (patch 0012, 0022)
>       - Introduce LSM documentation updates with the patches where
>         the interfaces are added rather than at the end. (patch 0012, 0022)
>       Include more maintainers and mail lists in To: and Cc: directives.
> v22: Rebase to 5.10-rc1
> v21: Rebase to 5.9-rc4
>       Incorporate feedback from v20
>       - Further revert UDS SO_PEERSEC to use scaffolding around
>         the interfaces that use lsmblobs and store only a single
>         secid. The possibility of multiple security modules
>         requiring data here is still a future problem.
>       - Incorporate Richard Guy Briggs' non-syscall auxiliary
>         records patch (patch 0019-0021) in place of my "supplimental"
>         records implementation. [I'm not sure I've given proper
>         attestation. I will correct as appropriate]
> v20: Rebase to 5.9-rc1
>       Change the BPF security module to use the lsmblob data. (patch 0002)
>       Repair length logic in subject label processing (patch 0015)
>       Handle -EINVAL from the empty BPF setprocattr hook (patch 0020)
>       Correct length processing in append_ctx() (patch 0022)
> v19: Rebase to 5.8-rc6
>       Incorporate feedback from v18
>       - Revert UDS SO_PEERSEC implementation to use lsmblobs
>         directly, rather than allocating as needed. The correct
>         treatment of out-of-memory conditions in the later case
>         is difficult to define. (patch 0005)
>       - Use a size_t in append_ctx() (patch 0021)
>       - Fix a memory leak when creating compound contexts. (patch 0021)
>       Fix build error when CONFIG_SECURITY isn't set (patch 0013)
>       Fix build error when CONFIG_SECURITY isn't set (patch 0020)
>       Fix build error when CONFIG_SECURITY isn't set (patch 0021)
> v18: Rebase to 5.8-rc3
>       Incorporate feedback from v17
>       - Null pointer checking in UDS (patch 0005)
>       Match changes in IMA code (patch 0012)
>       Fix the behavior of LSM context supplimental audit
>       records so that there's always exactly one when it's
>       appropriate for there to be one. This is a substantial
>       change that requires extention of the audit_context beyond
>       syscall events. (patch 0020)
> v17: Rebase to 5.7-rc4
> v16: Rebase to 5.6
>       Incorporate feedback from v15 - Thanks Stephen, Mimi and Paul
>       - Generally improve commit messages WRT scaffolding
>       - Comment ima_lsm_isset() (patch 0002)
>       - Some question may remain on IMA warning (patch 0002)
>       - Mark lsm_slot as __lsm_ro_after_init not __init_data (patch 0002)
>       - Change name of lsmblob variable in ima_match_rules() (patch 0003)
>       - Instead of putting a struct lsmblob into the unix_skb_parms
>         structure put a pointer to an allocated instance. There is
>         currently only space for 5 u32's in unix_skb_parms and it is
>         likely to get even tighter. Fortunately, the lifecycle
>         management of the allocated lsmblob is simple. (patch 0005)
>       - Dropped Acks due to the above change (patch 0005)
>       - Improved commentary on secmark labeling scaffolding. (patch 0006)
>       - Reduced secmark related labeling scaffolding. (patch 0006)
>       - Replace use of the zeroth entry of an lsmblob in scaffolding
>         with a function lsmblob_value() to hopefully make it less
>         obscure. (patch 0006)
>       - Convert security_secmark_relabel_packet to use lsmblob as
>         this reduces much of the most contentious scaffolding. (patch 0006)
>       - Dropped Acks due to the above change (patch 0006)
>       - Added BUILD_BUG_ON() for CIPSO tag 6. (patch 0018)
>       - Reworked audit subject information. Instead of adding fields in
>         the middle of existing records add a new record to the event. When
>         a separate record is required use subj="?". (patch 0020)
>       - Dropped Acks due to the above change (patch 0020)
>       - Reworked audit object information. Instead of adding fields in
>         the middle of existing records add a new record to the event. When
>         a separate record is required use obj="?". (patch 0021)
>       - Dropped Acks due to the above change (patch 0021)
>       - Enhanced documentation (patch 0022)
>       - Removed unnecessary error code check in security_getprocattr()
>         (patch 0021)
> v15: Rebase to 5.6-rc1
>       - Revise IMA data use (patch 0002)
>       Incorporate feedback from v14
>       - Fix lockdown module registration naming (patch 0002)
>       - Revise how /proc/self/attr/context is gathered. (patch 0022)
>       - Revise access modes on /proc/self/attr/context. (patch 0022)
>       - Revise documentation on LSM external interfaces. (patch 0022)
> v14: Rebase to 5.5-rc5
>       Incorporate feedback from v13
>       - Use an array of audit rules (patch 0002)
>       - Significant change, removed Acks (patch 0002)
>       - Remove unneeded include (patch 0013)
>       - Use context.len correctly (patch 0015)
>       - Reorder code to be more sensible (patch 0016)
>       - Drop SO_PEERCONTEXT as it's not needed yet (patch 0023)
> v13: Rebase to 5.5-rc2
>       Incorporate feedback from v12
>       - Print lsmblob size with %z (Patch 0002)
>       - Convert lockdown LSM initialization. (Patch 0002)
>       - Restore error check in nft_secmark_compute_secid (Patch 0006)
>       - Correct blob scaffolding in ima_must_appraise() (Patch 0009)
>       - Make security_setprocattr() clearer (Patch 0013)
>       - Use lsm_task_display more widely (Patch 0013)
>       - Use passed size in lsmcontext_init() (Patch 0014)
>       - Don't add a smack_release_secctx() hook (Patch 0014)
>       - Don't print warning in security_release_secctx() (Patch 0014)
>       - Don't duplicate the label in nfs4_label_init_security() (Patch 0016)
>       - Remove reviewed-by as code has significant change (Patch 0016)
>       - Send the entire lsmblob for Tag 6 (Patch 0019)
>       - Fix description of socket_getpeersec_stream parameters (Patch 0023)
>       - Retain LSMBLOB_FIRST. What was I thinking? (Patch 0023)
>       - Add compound context to LSM documentation (Patch 0023)
> v12: Rebase to 5.5-rc1
>       Fixed a couple of incorrect contractions in the text.
> v11: Rebase to 5.4-rc6
>       Incorporate feedback from v10
>       - Disambiguate reading /proc/.../attr/display by restricting
>         all use of the interface to the current process.
>       - Fix a merge error in AppArmor's display attribute check
> v10: Ask the security modules if the display can be changed.
> v9: There is no version 9
> v8: Incorporate feedback from v7
>      - Minor clean-up in display value management
>      - refactor "compound" context creation to use a common
>        append_ctx() function.
> v7: Incorporate feedback from v6
>      - Make setting the display a privileged operation. The
>        availability of compound contexts reduces the need for
>        setting the display.
> v6: Incorporate feedback from v5
>      - Add subj_<lsm>= and obj_<lsm>= fields to audit records
>      - Add /proc/.../attr/context to get the full context in
>        lsmname\0value\0... format as suggested by Simon McVittie
>      - Add SO_PEERCONTEXT for getsockopt() to get the full context
>        in the same format, also suggested by Simon McVittie.
>      - Add /sys/kernel/security/lsm_display_default to provide
>        the display default value.
> v5: Incorporate feedback from v4
>      - Initialize the lsmcontext in security_secid_to_secctx()
>      - Clear the lsmcontext in all security_release_secctx() cases
>      - Don't use the "display" on strictly internal context
>        interfaces.
>      - The SELinux binder hooks check for cases where the context
>        "display" isn't compatible with SELinux.
> v4: Incorporate feedback from v3
>      - Mark new lsm_<blob>_alloc functions static
>      - Replace the lsm and slot fields of the security_hook_list
>        with a pointer to a LSM allocated lsm_id structure. The
>        LSM identifies if it needs a slot explicitly. Use the
>        lsm_id rather than make security_add_hooks return the
>        slot value.
>      - Validate slot values used in security.c
>      - Reworked the "display" process attribute handling so that
>        it works right and doesn't use goofy list processing.
>      - fix display value check in dentry_init_security
>      - Replace audit_log of secids with '?' instead of deleting
>        the audit log
> v3: Incorporate feedback from v2
>      - Make lsmblob parameter and variable names more
>        meaningful, changing "le" and "l" to "blob".
>      - Improve consistency of constant naming.
>      - Do more sanity checking during LSM initialization.
>      - Be a bit clearer about what is temporary scaffolding.
>      - Rather than clutter security_getpeersec_dgram with
>        otherwise unnecessary checks remove the apparmor
>        stub, which does nothing useful.
> 
> Patch 01 moves management of the sock security blob
> from the individual modules to the infrastructure.
> 
> Patches 02-03 introduce a structure "lsmblob" that will gradually
> replace the "secid" as a shorthand for security module information.
> At this point lsmblob contains an array of u32 secids, one "slot"
> for each of the security modules compiled into the kernel that
> used secids. A "slot" is allocated when a security module requests
> one.
> 
> Patch 04 provides mechanism for the IMA subsystem to identify
> explicitly which LSM is subject to IMA policy. This includes
> a boot option for specifying the default and an additional option
> in IMA rules "lsm=".
> 
> Patches 05-13 change LSM interfaces to use the lsmblob instead
> of secids. It is important that the lsmblob be a fixed size entity
> that does not have to be allocated. Several of the places
> where it is used would have performance and/or locking
> issues with dynamic allocation.
> 
> Patch 14 provides a mechanism for a process to identify which
> security module's hooks should be used when displaying or
> converting a security context string.  A new interface
> /proc/self/attr/interface_lsm contains the name of the security
> module to show. Reading from this file will present the name of
> the module, while writing to it will set the value. Only names
> of active security modules are accepted. Internally, the name
> is translated to the appropriate "slot" number for the module
> which is then stored in the task security blob. Setting the
> display requires that all modules using the /proc interfaces
> allow the transition. The interface LSM of other processess
> can be neither read nor written. All suggested cases for
> reading the interface LSM of a different process have race
> conditions.
> 
> Patch 15 Starts the process of changing how a security
> context is represented. Since it is possible for a
> security context to have been generated by more than one
> security module it is now necessary to note which module
> created a security context so that the correct "release"
> hook can be called. There are several places where the
> module that created a security context cannot be inferred.
> 
> This is achieved by introducing a "lsmcontext" structure
> which contains the context string, its length and the
> "slot" number of the security module that created it.
> The security_release_secctx() interface is changed,
> replacing the (string,len) pointer pair with a lsmcontext
> pointer.
> 
> Patches 16-18 convert the security interfaces from
> (string,len) pointer pairs to a lsmcontext pointer.
> The slot number identifying the creating module is
> added by the infrastructure. Where the security context
> is stored for extended periods the data type is changed.
> 
> The Netlabel code is converted to save lsmblob structures
> instead of secids in Patch 19. This is not strictly
> necessary as there can only be one security module that
> uses Netlabel at this point. Using a lsmblob is much
> cleaner, as the interfaces that use the data have all
> been converted.
> 
> Patch 20 adds checks to the binder hooks which verify
> that both ends of a transaction use the same interface LSM.
> 
> Patches 21-23 add addition audit records for subject and
> object LSM data when there are multiple security modules
> with such data. The AUDIT_MAC_TASK_CONTEXTS record is used
> in conjuction with a "subj=?" field to identify the subject
> data. The AUDIT_MAC_OBJ_CONTEXTS record is used in conjuction
> with a "obj=?" field to identify the object data.  The
> AUDIT_MAC_TASK_CONTEXTS record identifies the security module
> with the data: "subj_selinux=xyz_t subj_apparmor=abc". The
> AUDIT_MAC_OBJ_CONTEXTS record identifies the security module
> with the data: "obj_selinux=xyz_t obj_apparmor=abc".  While
> AUDIT_MAC_TASK_CONTEXTS records will always contain an entry
> for each possible security modules, AUDIT_MAC_OBJ_CONTEXTS
> records will only contain entries for security modules for
> which the object in question has data.
> 
> An example of the MAC_TASK_CONTEXTS (1420) record is:
> 
>      type=UNKNOWN[1420]
>      msg=audit(1600880931.832:113)
>      subj_apparmor==unconfined
>      subj_smack=_
> 
> An example of the MAC_OBJ_CONTEXTS (1421) record is:
> 
>      type=UNKNOWN[1421]
>      msg=audit(1601152467.009:1050):
>      obj_selinux=unconfined_u:object_r:user_home_t:s0
> 
> Patch 24 adds a new interface for getting the compound security
> contexts, /proc/self/attr/context.  An example of the content
> of this file is:
> 
>      selinux\0one_u:one_r:one_t:s0-s0:c0.c1023\0apparmor\0unconfined\0
> 
> Finally, with all interference on the AppArmor hooks removed,
> Patch 25 removes the exclusive bit from AppArmor. An unnecessary
> stub hook was also removed.
> 
> The Ubuntu project is using an earlier version of this patchset in
> their distribution to enable stacking for containers.
> 
> Performance measurements to date have the change within the "noise".
> The sockperf and dbench results are on the order of 0.2% to 0.8%
> difference, with better performance being as common as worse. The
> benchmarks were run with AppArmor and Smack on Ubuntu.
> 
> https://github.com/cschaufler/lsm-stacking.git#stack-5.11-rc1-v24
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> 
> 
> Casey Schaufler (25):
>    LSM: Infrastructure management of the sock security
>    LSM: Add the lsmblob data structure.
>    LSM: provide lsm name and id slot mappings
>    IMA: avoid label collisions with stacked LSMs
>    LSM: Use lsmblob in security_audit_rule_match
>    LSM: Use lsmblob in security_kernel_act_as
>    LSM: Use lsmblob in security_secctx_to_secid
>    LSM: Use lsmblob in security_secid_to_secctx
>    LSM: Use lsmblob in security_ipc_getsecid
>    LSM: Use lsmblob in security_task_getsecid
>    LSM: Use lsmblob in security_inode_getsecid
>    LSM: Use lsmblob in security_cred_getsecid
>    IMA: Change internal interfaces to use lsmblobs
>    LSM: Specify which LSM to display
>    LSM: Ensure the correct LSM context releaser
>    LSM: Use lsmcontext in security_secid_to_secctx
>    LSM: Use lsmcontext in security_inode_getsecctx
>    LSM: security_secid_to_secctx in netlink netfilter
>    NET: Store LSM netlabel data in a lsmblob
>    LSM: Verify LSM display sanity in binder
>    audit: add support for non-syscall auxiliary records
>    Audit: Add new record for multiple process LSM  attributes
>    Audit: Add a new record for multiple object LSM attributes
>    LSM: Add /proc attr entry for full LSM context
>    AppArmor: Remove the exclusive flag
> 
>   Documentation/ABI/testing/ima_policy          |   8 +-
>   Documentation/ABI/testing/procfs-attr-context |  14 +
>   .../ABI/testing/procfs-attr-lsm_display       |  22 +
>   Documentation/security/lsm.rst                |  28 +
>   drivers/android/binder.c                      |  26 +-
>   fs/ceph/xattr.c                               |   6 +-
>   fs/nfs/nfs4proc.c                             |   8 +-
>   fs/nfsd/nfs4xdr.c                             |  20 +-
>   fs/proc/base.c                                |   2 +
>   include/linux/audit.h                         |  43 +-
>   include/linux/cred.h                          |   3 +-
>   include/linux/lsm_hooks.h                     |  36 +-
>   include/linux/security.h                      | 185 +++++-
>   include/net/netlabel.h                        |  11 +-
>   include/net/scm.h                             |  15 +-
>   include/net/xfrm.h                            |  13 +-
>   include/uapi/linux/audit.h                    |   2 +
>   kernel/audit.c                                | 175 ++++--
>   kernel/audit.h                                |  11 +-
>   kernel/auditfilter.c                          |  36 +-
>   kernel/auditsc.c                              | 191 +++---
>   kernel/cred.c                                 |  12 +-
>   net/ipv4/cipso_ipv4.c                         |  26 +-
>   net/ipv4/ip_sockglue.c                        |  12 +-
>   net/netfilter/nf_conntrack_netlink.c          |  24 +-
>   net/netfilter/nf_conntrack_standalone.c       |  11 +-
>   net/netfilter/nfnetlink_queue.c               |  38 +-
>   net/netfilter/nft_meta.c                      |  10 +-
>   net/netfilter/xt_SECMARK.c                    |   7 +-
>   net/netlabel/netlabel_domainhash.c            |   4 +-
>   net/netlabel/netlabel_kapi.c                  |   6 +-
>   net/netlabel/netlabel_unlabeled.c             | 106 ++--
>   net/netlabel/netlabel_unlabeled.h             |   2 +-
>   net/netlabel/netlabel_user.c                  |  23 +-
>   net/netlabel/netlabel_user.h                  |   2 +-
>   net/xfrm/xfrm_policy.c                        |  10 +-
>   net/xfrm/xfrm_state.c                         |  20 +-
>   security/apparmor/include/apparmor.h          |   3 +-
>   security/apparmor/include/net.h               |   6 +-
>   security/apparmor/include/procattr.h          |   2 +-
>   security/apparmor/lsm.c                       | 105 ++--
>   security/apparmor/procattr.c                  |  22 +-
>   security/bpf/hooks.c                          |  12 +-
>   security/commoncap.c                          |   7 +-
>   security/integrity/ima/ima.h                  |  15 +-
>   security/integrity/ima/ima_api.c              |  17 +-
>   security/integrity/ima/ima_appraise.c         |   6 +-
>   security/integrity/ima/ima_main.c             |  54 +-
>   security/integrity/ima/ima_policy.c           |  97 ++-
>   security/integrity/integrity_audit.c          |   6 +-
>   security/loadpin/loadpin.c                    |   8 +-
>   security/lockdown/lockdown.c                  |   7 +-
>   security/safesetid/lsm.c                      |   8 +-
>   security/security.c                           | 561 ++++++++++++++++--
>   security/selinux/hooks.c                      |  99 ++--
>   security/selinux/include/classmap.h           |   2 +-
>   security/selinux/include/objsec.h             |   5 +
>   security/selinux/include/security.h           |   1 +
>   security/selinux/netlabel.c                   |  25 +-
>   security/selinux/ss/services.c                |   4 +-
>   security/smack/smack.h                        |   6 +
>   security/smack/smack_access.c                 |   2 +-
>   security/smack/smack_lsm.c                    |  91 +--
>   security/smack/smack_netfilter.c              |   8 +-
>   security/smack/smackfs.c                      |  13 +-
>   security/tomoyo/tomoyo.c                      |   8 +-
>   security/yama/yama_lsm.c                      |   7 +-
>   67 files changed, 1741 insertions(+), 634 deletions(-)
>   create mode 100644 Documentation/ABI/testing/procfs-attr-context
>   create mode 100644 Documentation/ABI/testing/procfs-attr-lsm_display
>