linux-kernel - Re: [PATCH v3 2/2] ima: move APPRAISE_BOOTPARAM dependency on ARCH

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Date:   Tue, 30 Jun 2020 07:00:48 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Bruno Meneguele <bmeneg@...hat.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        erichte@...ux.ibm.com, nayna@...ux.ibm.com
Subject: Re: [PATCH v3 2/2] ima: move APPRAISE_BOOTPARAM dependency on
 ARCH_POLICY to runtime

On Mon, 2020-06-29 at 20:47 -0300, Bruno Meneguele wrote:

> 
> > I'm not if the "secure_boot" flag is available prior to calling
> > default_appraise_setup(), but if it is, you could modify the test
> > there to also check if the system is booted in secure boot mode (eg.
> > IS_ENABLED(CONFIG_IMA_APPRAISE_BOOTPARAM) &&
> > !arch_ima_get_secureboot())
> > 
> 
> Well pointed. I built a custom x86 kernel with some workaround to get
> this flag status within default_appraise_setup() and as a result the
> flag is was correctly available. 
> 
> Considering the nature of this flag (platform's firmware (in all
> arches?)) can we trust that every arch supporting secure/trusted boot
> will have it available in the __setup() call time?

Calling default_appraise_setup() could be deferred.

> 
> > > +		/* In secure and/or trusted boot the appraisal must be
> > > +		 * enforced, regardless kernel parameters, preventing
> > > +		 * runtime changes */
> > 
> > Only "appraise" rules are enforced.
> > 
> 
> Hmm.. do you mean the comment wording is wrong/"could be better",
> pointing the "appraise" action explicitly?

No, it's more than just the comment.  Like "trusted boot", IMA-
measurement only measures files, never enforces integrity.
 "ima_appraise" mode is only applicable to IMA-appraisal.

Mimi