Merge branch 'next-integrity.measure-keys' into next-integrity

Merge branch 'next-integrity.measure-keys' into next-integrity

From "KEYS: Measure keys when they are created or updated" cover letter:

Keys created or updated in the system are currently not measured.
Therefore an attestation service, for instance, would not be able to
attest whether or not the trusted keys keyring(s), for instance, contain
only known good (trusted) keys.

IMA measures system files, command line arguments passed to kexec,
boot aggregate, etc. It can be used to measure keys as well.
But there is no mechanism available in the kernel for IMA to
know when a key is created or updated.

This change aims to address measuring keys created or updated
in the system.

To achieve the above the following changes have been made:

 - Added a new IMA hook namely, ima_post_key_create_or_update, which
   measures the key. This IMA hook is called from key_create_or_update
   function. The key measurement can be controlled through IMA policy.

   A new IMA policy function KEY_CHECK has been added to measure keys.
   "keyrings=" option can be specified for KEY_CHECK to limit
   measuring the keys loaded onto the specified keyrings only.

   uid can be specified to further restrict key measurement for keys
   created by specific user.

   # measure keys loaded onto any keyring
   measure func=KEY_CHECK

   # measure keys loaded onto the IMA keyring only for root user
   measure func=KEY_CHECK uid=0 keyring=".ima"

   # measure keys on the BUILTIN and IMA keyrings into a different PCR
   measure func=KEY_CHECK keyring=".builtin_trusted_keys|.ima" pcr=11