[PATCH v4 0/2] IMA: Deferred measurement of keys

From: Lakshmi Ramasubramanian
Date: Fri Dec 13 2019 - 12:18:39 EST

This patchset extends the previous version[1] by adding support for
deferred processing of keys.

With the patchset referenced above, the IMA subsystem supports
measuring asymmetric keys when the key is created or updated.
But keys created or updated before a custom IMA policy is loaded
are currently not measured. This includes keys added to, for instance,
.builtin_trusted_keys which happens early in the boot process.

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).

If the kernel is built with both CONFIG_IMA and
must be applied as a custom policy. Not providing a custom policy
in the above configuration would result in asymmeteric keys being queued
until a custom policy is loaded. This is by design.

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

Testing performed:

* 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.



=> Check and set ima_process_keys flag with mutex held.


=> 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.


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


=> Code cleanup


=> Based changes on v5.4-rc8
=> The following patchsets should be applied in that order
=> Added functions to queue and dequeue keys, and process
the queued keys when custom IMA policies are applied.

Lakshmi Ramasubramanian (2):
IMA: Define workqueue for early boot key measurements
IMA: Call workqueue functions to measure queued keys

security/integrity/ima/ima.h | 15 ++
security/integrity/ima/ima_asymmetric_keys.c | 136 +++++++++++++++++++
security/integrity/ima/ima_policy.c | 3 +
3 files changed, 154 insertions(+)