| Message ID | 20191218164434.2877-1-nramas@linux.microsoft.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | IMA: Deferred measurement of keys | expand |
On Wed, 2019-12-18 at 08:44 -0800, Lakshmi Ramasubramanian wrote: > 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 > CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE enabled then the IMA policy > 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. I didn't notice the "This is by design" here, referring to the memory never being freed. "This is by design" was suppose to refer to requiring a custom policy for measuring keys. For now, these two patches are queued in the next-integrity-testing branch, but I would appreciate your addressing not freeing the memory associated with the keys, if a custom policy is not loaded. Please note that I truncated the 2/2 patch description, as it repeats the existing verification example in commit ("2b60c0ecedf8 IMA: Read keyrings= option from the IMA policy"). thanks, Mimi
On 12/20/2019 11:01 AM, Mimi Zohar wrote: Hi Mimi, >> If the kernel is built with both CONFIG_IMA and >> CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE enabled then the IMA policy >> 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. > > I didn't notice the "This is by design" here, referring to the memory > never being freed. "This is by design" was suppose to refer to > requiring a custom policy for measuring keys. > > For now, these two patches are queued in the next-integrity-testing > branch, but I would appreciate your addressing not freeing the memory > associated with the keys, if a custom policy is not loaded. > > Please note that I truncated the 2/2 patch description, as it repeats > the existing verification example in commit ("2b60c0ecedf8 IMA: Read > keyrings= option from the IMA policy"). > > thanks, > > Mimi > Sure - I am fine with truncating the 2/2 patch description. Thanks for doing that. Regarding "Freeing the queued keys if custom policy is not loaded": Shall I create a new patch set to address that and have that be reviewed independent of this patch set? Like you'd suggested earlier, we can wait for a certain time, after IMA is initialized, and free the queue if a custom policy was not loaded. Please let me know. thanks, -lakshmi
On Fri, 2019-12-20 at 11:25 -0800, Lakshmi Ramasubramanian wrote: > On 12/20/2019 11:01 AM, Mimi Zohar wrote: > > Hi Mimi, > > >> If the kernel is built with both CONFIG_IMA and > >> CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE enabled then the IMA policy > >> 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. > > > > I didn't notice the "This is by design" here, referring to the memory > > never being freed. "This is by design" was suppose to refer to > > requiring a custom policy for measuring keys. > > > > For now, these two patches are queued in the next-integrity-testing > > branch, but I would appreciate your addressing not freeing the memory > > associated with the keys, if a custom policy is not loaded. > > > > Please note that I truncated the 2/2 patch description, as it repeats > > the existing verification example in commit ("2b60c0ecedf8 IMA: Read > > keyrings= option from the IMA policy"). > > > > thanks, > > > > Mimi > > > > Sure - I am fine with truncating the 2/2 patch description. Thanks for > doing that. > > Regarding "Freeing the queued keys if custom policy is not loaded": > > Shall I create a new patch set to address that and have that be reviewed > independent of this patch set? If it is just a single additional patch, feel free to post it without a cover letter. > > Like you'd suggested earlier, we can wait for a certain time, after IMA > is initialized, and free the queue if a custom policy was not loaded. Different types of systems vary in boot time, but perhaps a certain amount of time after IMA is initialized would be consistent. This would need to work for IoT devices/sensors to servers. Mimi
On 12/20/19 11:36 AM, Mimi Zohar wrote: >> >> Shall I create a new patch set to address that and have that be reviewed >> independent of this patch set? > > If it is just a single additional patch, feel free to post it without > a cover letter. Sure >> >> Like you'd suggested earlier, we can wait for a certain time, after IMA >> is initialized, and free the queue if a custom policy was not loaded. > > Different types of systems vary in boot time, but perhaps a certain > amount of time after IMA is initialized would be consistent. This > would need to work for IoT devices/sensors to servers. > > Mimi > Yes - I agree. thanks, -lakshmi
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 CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE enabled then the IMA policy 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@linux.microsoft.com/ 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. Changelog: 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 (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 | 123 +++++++++++++++++++ security/integrity/ima/ima_policy.c | 3 + 3 files changed, 141 insertions(+)