linux-kernel - Re: [PATCH 01/11] evm: Execute evm_inode_init_security() only when the HMAC key is loaded

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Message-ID: <3c5840d3a827ccae575fc73d1aa4ed9f523c46b8.camel@linux.ibm.com>
Date:   Wed, 02 Sep 2020 09:40:51 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        "mjg59@...gle.com" <mjg59@...gle.com>, Petr Vorel <pvorel@...e.cz>
Cc:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>
Subject: Re: [PATCH 01/11] evm: Execute evm_inode_init_security() only when
 the HMAC key is loaded

On Wed, 2020-09-02 at 11:42 +0000, Roberto Sassu wrote:
> > From: Mimi Zohar [mailto:zohar@...ux.ibm.com]
> > Sent: Monday, August 24, 2020 7:45 PM
> > Hi Roberto,
> > 
> > On Fri, 2020-08-21 at 14:30 -0400, Mimi Zohar wrote:
> > > Sorry for the delay in reviewing these patches.   Missing from this
> > > patch set is a cover letter with an explanation for grouping these
> > > patches into a patch set, other than for convenience.  In this case, it
> > > would be along the lines that the original use case for EVM portable
> > > and immutable keys support was for a few critical files, not combined
> > > with an EVM encrypted key type.   This patch set more fully integrates
> > > the initial EVM portable and immutable signature support.
> > 
> > Thank you for more fully integrating the EVM portable signatures into
> > IMA.
> > 
> > " [PATCH 08/11] ima: Allow imasig requirement to be satisfied by EVM
> > portable signatures" equates an IMA signature to having a portable and
> > immutable EVM signature.  That is true in terms of signature
> > verification, but from an attestation perspective the "ima-sig"
> > template will not contain a signature.  If not the EVM signature, then
> > at least some other indication should be included in the measurement
> > list.
> 
> Would it be ok to print the EVM portable signature in the sig field if the IMA
> signature is not found? Later we can introduce the new template evm-sig
> to include all metadata necessary to verify the EVM portable signature.

As long as the attestation server can differentiate between the
signature types, including the EVM signature should be fine.

> 
> > Are you planning on posting the associated IMA/EVM regression tests?
> 
> I didn't have a look yet at the code. I will try to write some later.

It looks like ima_verify_signature() in ima-evm-utils could be extended
to support the EVM portable signature or at least not to fail the
signature verification.

Mimi