linux-kernel - Re: [PATCH v2 3/4] KEYS: Added BUILTIN_TRUSTED_KEYS enum to measure keys added to builtin_trusted

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Date:   Mon, 28 Oct 2019 13:08:38 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        dhowells@...hat.com, casey@...aufler-ca.com, sashal@...nel.org,
        jamorris@...ux.microsoft.com,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH v2 3/4] KEYS: Added BUILTIN_TRUSTED_KEYS enum to measure
 keys added to builtin_trusted_keys keyring

On Mon, 2019-10-28 at 08:12 -0700, Lakshmi Ramasubramanian wrote:
> On 10/27/19 7:33 AM, Mimi Zohar wrote:
> 
> > .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?