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

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Message-ID: <f1228f212520c66a5f3610627a7e26f736b384c5.camel@linux.ibm.com>
Date: Fri, 08 Mar 2024 09:23:13 -0500
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


> > > @@ -971,6 +1006,16 @@ void __init ima_init_policy(void)
> > >  {
> > >  	int build_appraise_entries, arch_entries;
> > >  
> > > +	/*
> > > +	 * We need to load digest cache rules at the beginning, to avoid dont_
> > > +	 * rules causing ours to not be reached.
> > > +	 */
> > 
> > "lockdown" trusts IMA to measure and appraise kernel modules, if the rule
> > exists.  Placing the digest_cache first breaks this trust.
> 
> The new rules don't prevent other rules to be reached, since they are
> 'do' and not 'don_t' rules.

My mistake.  These are just the rules for measuring or appraising the digest
cache lists themselves, not the actual policy rules for using the digest_cache. 
This should be fine.

Perhaps update the comment to reflect initramfs usage.


thanks,

Mimi