[v7,0/3] IMA: Deferred measurement of keys
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Message ID 20200103195435.2647-1-nramas@linux.microsoft.com
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  • IMA: Deferred measurement of keys
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Lakshmi Ramasubramanian Jan. 3, 2020, 7:54 p.m. UTC
The IMA subsystem supports measuring asymmetric keys when the key is
created or updated[1]. But keys created or updated before a custom
IMA policy is loaded are currently not measured. This includes keys
added, for instance, to either the .ima or .builtin_trusted_keys keyrings,
which happens early in the boot process.

Measuring the early boot keys, by design, requires loading
a custom IMA policy. This change adds support for queuing keys
created or updated before a custom IMA policy is loaded.
The queued keys are processed when a custom policy is loaded.
Keys created or updated after a custom policy is loaded are measured
immediately (not queued). In the case when a custom policy is not loaded
within 5 minutes of IMA initialization, the queued keys are freed.

[1] https://lore.kernel.org/linux-integrity/20191211164707.4698-1-nramas@linux.microsoft.com/

Testing performed:

  * Ran kernel self-test following the instructions given in
    https://www.kernel.org/doc/Documentation/kselftest.txt
  * Ran the lkp-tests using the job script provided by
    kernel test robot <rong.a.chen@intel.com>
  * Booted the kernel with this change.
  * Added .builtin_trusted_keys in "keyrings=" option in
    the IMA policy and verified the keys added to this
    keyring are measured.
  * Specified only func=KEY_CHECK and not "keyrings=" option,
    and verified the keys added to builtin_trusted_keys keyring
    are processed.
  * Added keys at runtime and verified they are measured
    if the IMA policy permitted.
      => For example, added keys to .ima keyring and verified.

Changelog:

  v7

  => Updated cover letter per Mimi's suggestions.
  => Updated "Reported-by" tag to be specific about
     the issues fixed in the patch.

  v6

  => Replaced mutex with a spinlock to sychronize access to
     queued keys. This fixes the problem reported by
     "kernel test robot <rong.a.chen@intel.com>"
     https://lore.kernel.org/linux-integrity/2a831fe9-30e5-63b4-af10-a69f327f7fb7@linux.microsoft.com/T/#t
  => Changed ima_queue_key() to a static function. This fixes
     the issue reported by "kbuild test robot <lkp@intel.com>"
     https://lore.kernel.org/linux-integrity/1577370464.4487.10.camel@linux.ibm.com/
  => Added the patch to free the queued keys if a custom IMA policy
     was not loaded to this patch set.

  v5

  => Removed temp keys list in ima_process_queued_keys()

  v4

  => Check and set ima_process_keys flag with mutex held.

  v3

  => Defined ima_process_keys flag to be static.
  => Set ima_process_keys with ima_keys_mutex held.
  => Added a comment in ima_process_queued_keys() function
     to state the use of temporary list for keys.

  v2

  => Rebased the changes to v5.5-rc1
  => Updated function names, variable names, and code comments
     to be less verbose.

  v1

  => Code cleanup

  v0

  => Based changes on v5.4-rc8
  => The following patchsets should be applied in that order
     https://lore.kernel.org/linux-integrity/1572492694-6520-1-git-send-email-zohar@linux.ibm.com
     https://lore.kernel.org/linux-integrity/20191204224131.3384-1-nramas@linux.microsoft.com/
  => Added functions to queue and dequeue keys, and process
     the queued keys when custom IMA policies are applied.

Lakshmi Ramasubramanian (3):
  IMA: Define workqueue for early boot key measurements
  IMA: Call workqueue functions to measure queued keys
  IMA: Defined timer to free queued keys

 security/integrity/ima/ima.h                 |  17 ++
 security/integrity/ima/ima_asymmetric_keys.c | 159 +++++++++++++++++++
 security/integrity/ima/ima_init.c            |   8 +-
 security/integrity/ima/ima_policy.c          |   3 +
 4 files changed, 186 insertions(+), 1 deletion(-)