[RFC][PATCH 4/8] ima: Add digest_cache_measure and digest_cache_appraise boot-time policies

[Mimi Zohar]

On Wed, 2024-02-14 at 15:35 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu at huawei.com>
> 
> Specify the 'digest_cache_measure' boot-time policy with 'ima_policy=' in
> the kernel command line to add the following rule at the beginning of the
> IMA policy, before other rules:
> 
> measure func=DIGEST_LIST_CHECK pcr=12
> 
> which will measure digest lists into PCR 12 (or the value in
> CONFIG_IMA_DIGEST_CACHE_MEASURE_PCR_IDX).
> 
> 'digest_cache_measure' also adds 'digest_cache=content pcr=12' to the other
> measure rules, if they have a compatible IMA hook. The PCR value still
> comes from CONFIG_IMA_DIGEST_CACHE_MEASURE_PCR_IDX.
> 
> Specify 'digest_cache_appraise' to add the following rule at the beginning,
> before other rules:
> 
> appraise func=DIGEST_LIST_CHECK appraise_type=imasig|modsig
> 
> which will appraise digest lists with IMA signatures or module-style
> appended signatures.
> 
> 'digest_cache_appraise' also adds 'digest_cache=content' to the other
> appraise rules, if they have a compatible IMA hook.

Defining two new built-in policies - digest_cache_measure, digest_cache_appraise
- in a single patch would be acceptable, if there wasn't anything else going on.

Changing other policy rules should not be made in this patch.  A clear
explanation as to why other policy rules need to be modified is needed.  It
shouldn't be hidden here.

thanks,

Mimi

> 
> Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
>