linux-kernel - Re: [PATCH] ima: add a new CONFIG for loading arch-specific policies

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Date:   Thu, 27 Feb 2020 14:38:09 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        linux-integrity@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-efi@...r.kernel.org, linux-s390@...r.kernel.org
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Philipp Rudo <prudo@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ima: add a new CONFIG for loading arch-specific policies

On Wed, 2020-02-26 at 15:36 -0500, Mimi Zohar wrote:
> On Wed, 2020-02-26 at 11:21 -0800, Lakshmi Ramasubramanian wrote:
> > Hi Nayna,
> > 
> > > +
> > > +config IMA_SECURE_AND_OR_TRUSTED_BOOT
> > > +	bool
> > > +	depends on IMA
> > > +	depends on IMA_ARCH_POLICY
> > > +	default n
> > > +	help
> > > +	   This option is selected by architectures to enable secure and/or
> > > +	   trusted boot based on IMA runtime policies.
> > > 
> > 
> > Why is the default for this new config "n"?
> > Is there any reason to not turn on this config if both IMA and 
> > IMA_ARCH_POLICY are set to y?
> 
> Good catch.  Having "IMA_SECURE_AND_OR_TRUSTED_BOOT" depend on
> "IMA_ARCH_POLICY" doesn't make sense.  "IMA_ARCH_POLICY" needs to be
> selected.

After discussing this some more with Nayna, the new Kconfig indicates
that the architecture defines the arch_ima_get_secureboot() and
arch_get_ima_policy() functions, but doesn't automatically enable
IMA_ARCH_POLICY.  The decision to enable IMA_ARCH_POLICY is left up to
whoever is building the kernel.  The patch, at least this aspect of
it, is correct.

Mimi