linux-kernel - Re: [PATCH 0/6] Constant Time Memory Comparisons Are Important

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Message-ID: <20235732.W6WmnKk6cl@tauon.chronox.de>
Date:   Sun, 11 Jun 2017 23:06:14 +0200
From:   Stephan Müller <smueller@...onox.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        Anna Schumaker <anna.schumaker@...app.com>,
        David Howells <dhowells@...hat.com>,
        David Safford <safford@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Marcel Holtmann <marcel@...tmann.org>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        keyrings@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 0/6] Constant Time Memory Comparisons Are Important

Am Samstag, 10. Juni 2017, 04:59:06 CEST schrieb Jason A. Donenfeld:

Hi Jason,

> Whenever you're comparing two MACs, it's important to do this using
> crypto_memneq instead of memcmp. With memcmp, you leak timing information,
> which could then be used to iteratively forge a MAC. This is far too basic
> of a mistake for us to have so pervasively in the year 2017, so let's begin
> cleaning this stuff up. The following 6 locations were found with some
> simple regex greps, but I'm sure more lurk below the surface. If you
> maintain some code or know somebody who maintains some code that deals
> with MACs, tell them to double check which comparison function they're
> using.

Are you planning to send an update to your patch set? If yes, there is another 
one which should be converted too: crypto/rsa-pkcs1pad.c.

Otherwise, I will send a patch converting this one.

Thanks.

Ciao
Stephan