linux-kernel - Re: [PATCH] lib: memcmp_nta: add timing-attack secure memcmp

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Message-ID: <87zjzallp5.fsf@mid.deneb.enyo.de>
Date:	Mon, 11 Feb 2013 20:00:54 +0100
From:	Florian Weimer <fw@...eb.enyo.de>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib: memcmp_nta: add timing-attack secure memcmp

* Daniel Borkmann:

> + * memcmp_nta - memcmp that is secure against timing attacks

It's not providing an ordering, so it should not have "cmp" in the
name.

> +	for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
> +		res |= (*su1 ^ *su2);

The compiler could still short-circuit this loop.  Unlikely at
present, but this looks like a maintenance hazard.
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