linux-kernel - Re: [RFC][PATCH 4/8] ima: Add digest_cache_measure and digest_cache

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Date: Mon, 11 Mar 2024 09:01:03 -0400
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>, corbet@....net,
        dmitry.kasatkin@...il.com, eric.snowberg@...cle.com,
        paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com
Cc: linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-security-module@...r.kernel.org,
        wufan@...ux.microsoft.com, pbrobinson@...il.com, zbyszek@...waw.pl,
        hch@....de, mjg59@...f.ucam.org, pmatilai@...hat.com, jannh@...gle.com,
        dhowells@...hat.com, jikos@...nel.org, mkoutny@...e.com,
        ppavlu@...e.com, petr.vorel@...il.com, petrtesarik@...weicloud.com,
        mzerqung@...inter.de, kgold@...ux.ibm.com,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [RFC][PATCH 4/8] ima: Add digest_cache_measure and
 digest_cache_appraise boot-time policies

On Wed, 2024-02-14 at 15:35 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.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@...wei.com>
>