linux-kernel - Re: crypto: zeroization of sensitive data in af

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Date:	Mon, 10 Nov 2014 21:55:43 -0500
From:	Sandy Harris <sandyinchina@...il.com>
To:	Stephan Mueller <smueller@...onox.de>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	LKML <linux-kernel@...r.kernel.org>, linux-crypto@...r.kernel.org
Subject: Re: crypto: zeroization of sensitive data in af_alg

On Sun, Nov 9, 2014 at 5:33 PM, Stephan Mueller <smueller@...onox.de> wrote:

> while working on the AF_ALG interface, I saw no active zeroizations of memory
> that may hold sensitive data that is maintained outside the kernel crypto API
> cipher handles. ...

> I think I found the location for the first one: hash_sock_destruct that should
> be enhanced with a memset(0) of ctx->result.

See also a thread titled "memset() in crypto code?" on the linux
crypto list. The claim is that gcc can optimise memset() away so you
need a different function to guarantee the intended results. There's a
patch to the random driver that uses a new function
memzero_explicit(), and one of the newer C standards has a different
function name for the purpose.
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