[RFC PATCH v8 00/17] Integrity Policy Enforcement LSM (IPE)
by Deven Bowers
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, to this general-purpose computing rule; however,
such as the scenario, wherein Linux distribution vendors trust only
their own keys - in this case, IPE can be used to enforce the trust
reqiurement.
IPE, instead of supporting web of trust, supports PKI, which generally
designates a set of entities that provide a measure absolute trust.
Commonly used in embedded systems,
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 (NOT the
policy syntax version). 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 will allow any execution. 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.
Available properties for IPE described in the documentation patch of this
series.
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. 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. User mode can interrogate the kernel to understand what
properties and the associated versions through the securityfs node,
$securityfs/ipe/config, which will return a string of form:
key1=version1
key2=version2
.
.
.
keyN=versionN
User-mode should correlate these versions with the supported values
identified in the documentation to determine whether a policy should
be accepted by the system without actually trying to deploy 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 userland is setup and ready to receive commands, at which
point a policy can be deployed via securityfs. This "boot policy" can be
specified via the config, SECURITY_IPE_BOOT_POLICY, which accepts a path
to a plain-text version of the IPE policy to apply. This policy will be
compiled into the kernel. If not specified, IPE will be disabled until a
policy is deployed and activated through the method above.
Policy Examples:
----------------
Allow all:
policy_name="Allow All" policy_version=0.0.0
DEFAULT action=ALLOW
Allow only initial superblock:
policy_name="Allow All Initial SB" policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
Allow any signed dm-verity volume and the initial superblock:
policy_name="AllowSignedAndInitial" policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
op=EXECUTE dmverity_signature=TRUE action=ALLOW
Prohibit execution from a specific dm-verity volume, while allowing
all signed volumes and the initial superblock:
policy_name="ProhibitSingleVolume" policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=DENY
op=EXECUTE boot_verified=TRUE action=ALLOW
op=EXECUTE dmverity_signature=TRUE action=ALLOW
Allow only a specific dm-verity volume:
policy_name="AllowSpecific" policy_version=0.0.0
DEFAULT action=DENY
op=EXECUTE dmverity_roothash=sha256:401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=ALLOW
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_SECURITY_IPE=y
CONFIG_SECURITY_IPE_KUNIT_TEST=y
CONFIG_IPE_PROP_BOOT_VERIFIED=y
CONFIG_IPE_PROP_DM_VERITY_SIGNATURE=y
CONFIG_IPE_PROP_DM_VERITY_ROOTHASH=y
CONFIG_IPE_PROP_FS_VERITY_SIGNATURE=y
CONFIG_IPE_PROP_FS_VERITY_DIGEST=y
Simply run:
make ARCH=um mrproper
./tools/testing/kunit/kunit.py run --kunitconfig <path/to/config>
And the tests will execute and report the result. For more indepth testing,
it will require you to create and mount a dm-verity volume or fs-verity
enabled file.
Documentation:
--------------
There is both documentation available on github at
https://microsoft.github.io/ipe, and Documentation in this patch series,
to be added in-tree.
Known Gaps:
-----------
IPE has two known gaps:
1. IPE cannot verify the integrity of anonymous executable memory, such as
the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code.
Unfortunately, as this is dynamically generated code, there is no way
for IPE to ensure the integrity of this code to form a trust basis. In all
cases, the return result for these operations will be whatever the admin
configures the DEFAULT action for "EXECUTE".
2. IPE cannot verify the integrity of interpreted languages' programs when
these scripts invoked via ``<interpreter> <file>``. This is because the
way interpreters execute these files, the scripts themselves are not
evaluated as executable code through one of IPE's hooks. Interpreters
can be enlightened to the usage of IPE by trying to mmap a file into
executable memory (+X), after opening the file and responding to the
error code appropriately. This also applies to included files, or high
value files, such as configuration files of critical system components.
Appendix:
---------
A. IPE Github Repository: https://github.com/microsoft/ipe
B. IPE Users' Guide: Documentation/admin-guide/LSM/ipe.rst
References:
-----------
1: https://lore.kernel.org/bpf/4d6932e96d774227b42721d9f645ba51@huawei.com/T/
FAQ:
----
Q: What is the difference between IMA and IPE?
A: See the documentation patch for more on this topic.
Previous Postings
-----------------
v1: https://patchwork.kernel.org/project/linux-security-module/list/?series=2...
v2: https://patchwork.kernel.org/project/linux-security-module/list/?series=2...
v3: https://patchwork.kernel.org/project/linux-security-module/list/?series=2...
v4: https://patchwork.kernel.org/project/linux-security-module/list/?series=3...
v5: https://patchwork.kernel.org/project/linux-security-module/list/?series=3...
v6: https://patchwork.kernel.org/project/linux-security-module/list/?series=3...
v7: https://patchwork.kernel.org/project/linux-security-module/list/?series=5...
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.
Deven Bowers (15):
security: add ipe lsm & initial context creation
ipe: add policy parser
ipe: add evaluation loop
ipe: add userspace interface
ipe: add LSM hooks on execution and kernel read
uapi|audit: add ipe audit message definitions
ipe: add auditing support
ipe: add permissive toggle
ipe: introduce 'boot_verified' as a trust provider
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 tests
documentation: add ipe documentation
Fan Wu (2):
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 | 739 ++++++++++++
.../admin-guide/kernel-parameters.txt | 12 +
Documentation/security/index.rst | 1 +
Documentation/security/ipe.rst | 559 +++++++++
MAINTAINERS | 9 +
block/bdev.c | 7 +
drivers/md/dm-verity-target.c | 25 +-
drivers/md/dm-verity-verify-sig.c | 16 +-
drivers/md/dm-verity-verify-sig.h | 10 +-
fs/verity/fsverity_private.h | 2 +-
fs/verity/open.c | 13 +-
fs/verity/signature.c | 1 +
include/asm-generic/vmlinux.lds.h | 16 +
include/linux/blk_types.h | 1 +
include/linux/dm-verity.h | 19 +
include/linux/fsverity.h | 2 +
include/linux/lsm_hook_defs.h | 5 +
include/linux/lsm_hooks.h | 12 +
include/linux/security.h | 22 +
include/uapi/linux/audit.h | 1 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 1 +
scripts/ipe/polgen/Makefile | 6 +
scripts/ipe/polgen/polgen.c | 145 +++
security/Kconfig | 11 +-
security/Makefile | 1 +
security/ipe/.gitignore | 1 +
security/ipe/Kconfig | 101 ++
security/ipe/Makefile | 37 +
security/ipe/audit.c | 227 ++++
security/ipe/audit.h | 39 +
security/ipe/ctx.c | 368 ++++++
security/ipe/ctx.h | 43 +
security/ipe/ctx_test.c | 718 ++++++++++++
security/ipe/eval.c | 240 ++++
security/ipe/eval.h | 52 +
security/ipe/fs.c | 340 ++++++
security/ipe/fs.h | 13 +
security/ipe/hooks.c | 298 +++++
security/ipe/hooks.h | 45 +
security/ipe/ipe.c | 159 +++
security/ipe/ipe.h | 28 +
security/ipe/ipe_parser.h | 59 +
security/ipe/modules.c | 272 +++++
security/ipe/modules.h | 17 +
security/ipe/modules/Kconfig | 66 ++
security/ipe/modules/Makefile | 12 +
security/ipe/modules/boot_verified.c | 26 +
security/ipe/modules/dmverity_roothash.c | 31 +
security/ipe/modules/dmverity_signature.c | 26 +
security/ipe/modules/fsverity_digest.c | 39 +
security/ipe/modules/fsverity_signature.c | 34 +
security/ipe/modules/ipe_module.h | 46 +
security/ipe/parsers.c | 143 +++
security/ipe/parsers/Makefile | 12 +
security/ipe/parsers/default.c | 106 ++
security/ipe/parsers/policy_header.c | 126 ++
security/ipe/policy.c | 1037 +++++++++++++++++
security/ipe/policy.h | 113 ++
security/ipe/policy_parser_tests.c | 313 +++++
security/ipe/policyfs.c | 528 +++++++++
security/security.c | 70 ++
64 files changed, 7409 insertions(+), 16 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/ctx.c
create mode 100644 security/ipe/ctx.h
create mode 100644 security/ipe/ctx_test.c
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/ipe_parser.h
create mode 100644 security/ipe/modules.c
create mode 100644 security/ipe/modules.h
create mode 100644 security/ipe/modules/Kconfig
create mode 100644 security/ipe/modules/Makefile
create mode 100644 security/ipe/modules/boot_verified.c
create mode 100644 security/ipe/modules/dmverity_roothash.c
create mode 100644 security/ipe/modules/dmverity_signature.c
create mode 100644 security/ipe/modules/fsverity_digest.c
create mode 100644 security/ipe/modules/fsverity_signature.c
create mode 100644 security/ipe/modules/ipe_module.h
create mode 100644 security/ipe/parsers.c
create mode 100644 security/ipe/parsers/Makefile
create mode 100644 security/ipe/parsers/default.c
create mode 100644 security/ipe/parsers/policy_header.c
create mode 100644 security/ipe/policy.c
create mode 100644 security/ipe/policy.h
create mode 100644 security/ipe/policy_parser_tests.c
create mode 100644 security/ipe/policyfs.c
--
2.25.1
2 years, 2 months
- 6
- 25
Excluding a script / process and its descendants from audit
by Stephen Smalley
Hi,
Is it possible to exclude a script from triggering audit records?
I know that one can exclude an executable via -a never,exit -F
exe=/path/to/exe but I haven't been able to find a way to do the same
for a script.
Also, is there a way to have the exclusion applied to all child
processes spawned by the script?
Thanks.
2 years, 3 months
- 3
- 2
[PATCH v37 00/33] LSM: Module stacking for AppArmor
by Casey Schaufler
This patchset provides the changes required for
the AppArmor security module to stack safely with any other.
There are additional changes required for SELinux and Smack
to coexist. These are primarily in the networking code and
will be addressed after these changes are upstream.
v37: Rebase to 5.19-rc3
- Audit changes should be complete, all comments have been
addressed.
- Address indexing an empty array for the case where no
built in security modules require data in struct lsmblob.
- Fix a few checkpatch complaints.
v36: Rebase to 5.19-rc1
- Yet another rework of the audit changes. Rearranging how the
timestamp is managed allows auxiliary records to be generated
correctly with a minimum of fuss.
- In the end no LSM interface scaffolding remains. Secids have
been replaced with lsmblob structures in all cases, including
IMA and NetLabel.
v35: Rebase to 5.18-rc2
- Address the case where CONFIG_SECURITY is enabled but
no security modules that use secid slots are included.
The resulting blob.secid[0] instances, although never
present in a call path, raised concerns.
- Address the case in interface_lsm where the BPF module
returns -EINVAL, resulting in a failed setting of the
value that would be otherwise allowed.
v34: Rebase to 5.18-rc1
- Incorporate feedback on the audit generation.
v33:
- Rework the supplimental audit record generation once more,
this time taking pseudo-code provided by Paul Moore as a
basis. The resulting code is considerably simpler and fits
better with the existing code flow.
v32: Rebase to 5.17-rc2
- Incorporate additional feedback from v30.
v31: Rebase to 5.16-rc4
- Incorporate feedback from Paul Moore on the audit
component changes.
v30: Rebase to 5.16-rc1
- Replace the integrity sub-system reuse of the audit
subsystem event matching functions with IMA specific
functions. This is done because audit needs to maintain
information about multiple security modules in audit
rules while IMA to restricts the information to a single
security module.
- The binder hooks have been changed and are no longer
called with sufficient information to identify the
interface_lsm. Pass that information in the binder
message, and use that in the compatibility decision.
- Refactor the audit changes.
v29: Rebase to 5.15-rc1
- Rework the supplimental audit record generation. Attach
a list of supplimental data to the audit_buffer and
generate the auxiliary records as needed on event end.
This should be usable for other auxiliary data, such as
container IDs. There is other ongoing audit work that
will require integration with this.
v28: Rebase to 5.14-rc2
- Provide IMA rules bounds checking (patch 04)
- Quote contexts in MAC_TASK_CONTEXTS and MAC_OBJ_CONTEXTS
audit records because of AppArmor's use of '=' in context
values. (patch 22,23)
v27: Fixes for landlock (patch 02)
- Rework the subject audit record generation. This version is
simpler and reflects feedback from Paul Moore. (patch 22)
v26: Rebase to 5.13-rc1
- Include the landlock security module.
- Accomodate change from security_task_getsecid() to
security_task_getsecid_obj() and security_task_getsecid_subj().
v25: Rebase to 5.12-rc2
Incorporate feedback from v24
- The IMA team suggested improvements to the integrity rule
processing.
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 separates the audit rule processing from the
integrity rule processing. They were never really the
same, but void pointers could hide that. The changes
following use the rule pointers differently in audit
and IMA, so keeping the code common is not a good idea.
Patch 02 moves management of the sock security blob
from the individual modules to the infrastructure.
Patches 03-04 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 05 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 06-13 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 16-19 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.
Patch 20 converts the Netlabel code to save lsmblob structures
instead of secids. 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 21 adds checks to the binder hooks which verify
that both ends of a transaction use the same interface LSM.
Patch 22 adds a parameter to security_secid_to_secctx()
that indicates which of the security modules should be used
to provide the context.
Patches 23-27 update the audit system to better handle auxiliary
records. This requires rearranging the timestamp and serial number
handling. The skb pointer used to collect audit data is replaced
by a list of skb pointers.
Patch 28 adds a supplimental audit record for subject
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_TASK_CONTEXTS record identifies the security module
with the data: subj_selinux=xyz_t subj_apparmor=abc.
An example of the MAC_TASK_CONTEXTS (1420) record is:
type=UNKNOWN[1420]
msg=audit(1600880931.832:113)
subj_apparmor==unconfined
subj_smack=_
Patch 29 adds a supplimental audit record for object
LSM data when there are multiple security modules with such data.
The AUDIT_MAC_OBJ_CONTEXTS record is used in conjuction The
with a "obj=?" field to identify the object data.
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_OBJ_CONTEXTS (1421) record is:
type=UNKNOWN[1421]
msg=audit(1601152467.009:1050):
obj_selinux=unconfined_u:object_r:user_home_t:s0
Patch 32 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 33 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-5.19-rc3-v37
Casey Schaufler (33):
integrity: disassociate ima_filter_rule from security_audit_rule
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_current_getsecid
LSM: Use lsmblob in security_inode_getsecid
LSM: Use lsmblob in security_cred_getsecid
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: Use lsmcontext in security_dentry_init_security
LSM: security_secid_to_secctx in netlink netfilter
NET: Store LSM netlabel data in a lsmblob
binder: Pass LSM identifier for confirmation
LSM: security_secid_to_secctx module selection
Audit: Keep multiple LSM data in audit_names
Audit: Create audit_stamp structure
LSM: Add a function to report multiple LSMs
Audit: Allow multiple records in an audit_buffer
Audit: Add record for multiple task security contexts
audit: multiple subject lsm values for netlabel
Audit: Add record for multiple object contexts
netlabel: Use a struct lsmblob in audit data
LSM: Removed scaffolding function lsmcontext_init
LSM: Add /proc attr entry for full LSM context
AppArmor: Remove the exclusive flag
Documentation/ABI/testing/ima_policy | 8 +-
.../ABI/testing/procfs-attr-lsm_display | 22 +
Documentation/security/lsm.rst | 28 +
drivers/android/binder.c | 47 +-
drivers/android/binder_internal.h | 1 +
fs/ceph/super.h | 3 +-
fs/ceph/xattr.c | 15 +-
fs/fuse/dir.c | 35 +-
fs/nfs/dir.c | 2 +-
fs/nfs/inode.c | 17 +-
fs/nfs/internal.h | 8 +-
fs/nfs/nfs4proc.c | 14 +-
fs/nfs/nfs4xdr.c | 22 +-
fs/nfsd/nfs4xdr.c | 20 +-
fs/proc/base.c | 2 +
include/linux/audit.h | 21 +-
include/linux/cred.h | 3 +-
include/linux/lsm_hooks.h | 19 +-
include/linux/nfs4.h | 8 +-
include/linux/nfs_fs.h | 2 +-
include/linux/security.h | 264 +++++++-
include/net/netlabel.h | 10 +-
include/net/scm.h | 15 +-
include/uapi/linux/audit.h | 2 +
kernel/audit.c | 261 +++++--
kernel/audit.h | 18 +-
kernel/auditfilter.c | 29 +-
kernel/auditsc.c | 160 ++---
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_kapi.c | 6 +-
net/netlabel/netlabel_unlabeled.c | 98 ++-
net/netlabel/netlabel_unlabeled.h | 2 +-
net/netlabel/netlabel_user.c | 10 +-
net/netlabel/netlabel_user.h | 2 +-
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 | 32 +-
security/integrity/ima/ima_api.c | 6 +-
security/integrity/ima/ima_appraise.c | 11 +-
security/integrity/ima/ima_main.c | 62 +-
security/integrity/ima/ima_policy.c | 92 ++-
security/landlock/cred.c | 2 +-
security/landlock/fs.c | 2 +-
security/landlock/ptrace.c | 2 +-
security/landlock/setup.c | 5 +
security/landlock/setup.h | 1 +
security/loadpin/loadpin.c | 8 +-
security/lockdown/lockdown.c | 7 +-
security/safesetid/lsm.c | 8 +-
security/security.c | 635 ++++++++++++++++--
security/selinux/hooks.c | 103 +--
security/selinux/include/classmap.h | 3 +-
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 | 4 +-
security/smack/smackfs.c | 12 +-
security/tomoyo/tomoyo.c | 8 +-
security/yama/yama_lsm.c | 7 +-
75 files changed, 1869 insertions(+), 746 deletions(-)
create mode 100644 Documentation/ABI/testing/procfs-attr-lsm_display
--
2.36.1
2 years, 3 months
- 3
- 38
Trying to understand audisp-remote network behavior
by Ken Hornstein
So we've been struggling with getting audisp-remote working in a
reliable manner. In summary, it works but the networking seems fragile.
We are using Kerberos authentication with audisp-remote, but that
doesn't seem to be related to the fragility (sadly the Kerberos support
does make it trivial to completely hang the server, but that's another
issue). This is on RHEL 7 which ships with audit-2.8.5, but as far as
I can tell the relevant code hasn't changed much from there to what
is on GitHub.
After staring at the code a lot and doing some experiments, here's what
I believe to be true. I'll gladly take corrections for anything I get
wrong.
- If a connection has _never_ been made successfully by audisp-remote,
it will retry the connection (in theory there's a limit to retries,
but that seems to be per-message; it will retry on every new message).
Fine, that seems reasonable.
- If the connection is lost for almost any reason (see below), the connection
is never retried using the default configuration. There might be some
corner cases where a retry can happen, but in my experience that is rare.
Once it's gone, it never gets retried, and audit messages build up until
the queue overflows.
- In theory if a graceful shutdown is received by audisp-remote (either
a zero-length read or a "ENDING" audit message), then retries can
happen; this is indicated by the "remote_ended" flag in the code. But
in my experience that is rare; during my experiments when I rebooted
our audit server that message was never sent (I guess the audit server
stop was received after the interfaces were shut down). If the audit
server crashes or you have a network failure, you end up getting an
error on a write and then the network is marked down and you get into
never-retry state.
- If you turn on heartbeats via heartbeat_timeout, the network connection
_will_ retry when a heartbeat is sent. However, the subtle issue here
is that a heartbeat is only sent when there are no incoming audit messages
within the heartbeat timeout.
The key issue seems to be in this part of the loop in main() (this section is
entered when audisp-remote receives an audit record):
// See if input fd is also set
if (FD_ISSET(ifd, &rfd)) {
do {
if (remote_fgets(event, sizeof(event), ifd)) {
if (!transport_ok && remote_ended &&
(config.remote_ending_action ==
FA_RECONNECT ||
!connected_once)) {
quiet = 1;
if (init_transport() ==
ET_SUCCESS) {
remote_ended = 0;
connected_once = 1;
}
quiet = 0;
}
In short, when a new audit record is received, init_transport()
(which tries to connect to the audit server) is only called _IF_ the
connection is down (transport_ok == 0) _and_ remote_ended is true _and_
remote_ending_action is set to FA_RECONNECT (the default) _or_ there
hasn't been at least one successful connection (connected_once == 0).
The problem with that is at least in our environment remote_ended is
never set to 1, so when the connection drops it is never retried, and
there aren't any other entry points in the normal event loop that would
ever cause the connection to retry.
The heartbeat code calls relay_event() directly (code that sends audit
events normally calls send_one() which returns if transport_ok is false)
and relay_event() calls either relay_sock_ascii() or relay_sock_managed()
and those two functions will call init_transport() if the network
connection is down. But as mentioned above, you need to make sure that
you try to send a heartbeat every so often; if you have a server generating
audit messages constantly then there won't be a heartbeat if you set the
heartbeat timeout too high.
You _can_ get a network connection retry if you encounter an error
inside of relay_sock_ascii() or relay_sock_managed(); I can't say
that didn't happen with us, but it sure seemed like it wasn't sufficient
and having the transport marked as failed was inevitible.
So, I guess my questions are:
- Is this all accurate?
- Is this how it's SUPPOSED to be? At least for us, network glitches
happen enough that most of our hosts ended up with overflowing
audisp-remote queues. Setting the heartbeat timeout seems to have
resolved that (but it took a little experimentation to figure out
the right value). It just seems surprising that it was easy to get
into a situation where you'd never retry a connection.
--Ken
2 years, 3 months
- 3
- 7
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