linux-kernel - Re: [PATCH 7/8] ima: use ima_hash_algo for collision detection in the measurement list

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Date:   Fri, 31 Jan 2020 09:50:34 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        "james.bottomley@...senpartnership.com" 
        <james.bottomley@...senpartnership.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>
Cc:     "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>
Subject: Re: [PATCH 7/8] ima: use ima_hash_algo for collision detection in
 the measurement list

On Fri, 2020-01-31 at 14:41 +0000, Roberto Sassu wrote:
> I thought that using a stronger algorithm for hash collision detection but
> doing remote attestation with the weaker would not bring additional value.
> 
> If there is a hash collision on SHA1, an attacker can still replace the data of
> one of the two entries in the measurement list with the data of the other
> without being detected (without additional countermeasures).
> 
> If the verifier additionally checks for duplicate template digests, he could
> detect the attack (IMA would not add a new measurement entry with the
> same template digest of previous entries).
> 
> Ok, I will use ima_hash_algo for hash collision detection.

Thanks!

Mimi