On Mon, 2019-10-28 at 08:12 -0700, Lakshmi Ramasubramanian wrote:

On 10/27/19 7:33 AM, Mimi Zohar wrote:

quoted

.builtin_trusted_keys is a trusted keyring, which is created by the
kernel.  It cannot be deleted or replaced by userspace, so it should
be possible to correlate a keyring name with a keyring number on
policy load.

Yes - at policy load we can map a keyring name to a keyring number.

But at runtime we still need to know if the keyring parameter passed to 
the IMA hook function is configured to be measured.

void ima_post_key_create_or_update(struct key *keyring, struct key *key,
				   unsigned long flags, bool create);
{
    => Get the keyring number for the given "keyring".

There is no "getting" involved here.  Pass "keyring" to
process_buffer_measurement and on to ima_get_action().

    => Check if the keyring number is in the configured IMA policy.

ima_get_action() should do a simple compare of the valued stored in
the IMA policy with the value returned by key_serial().

Mimi

    => If yes, measure the key.
    => Else, do nothing.
}

Did I misunderstand what you had stated?