From: Florian Weimer <fw@deneb.enyo.de>
To: James Yonan <james@openvpn.net>
Cc: Daniel Borkmann <dborkman@redhat.com>,
Marcelo Cerri <mhcerri@linux.vnet.ibm.com>,
linux-crypto@vger.kernel.org, herbert@gondor.hengli.com.au
Subject: Re: [PATCH] crypto_mem_not_equal: add constant-time equality testing of memory regions
Date: Sun, 15 Sep 2013 17:45:53 +0200 [thread overview]
Message-ID: <878uyyks0e.fsf@mid.deneb.enyo.de> (raw)
In-Reply-To: <1379259179-2677-1-git-send-email-james@openvpn.net> (James Yonan's message of "Sun, 15 Sep 2013 09:32:59 -0600")
* James Yonan:
> + * Constant-time equality testing of memory regions.
> + * Returns 0 when data is equal, non-zero otherwise.
> + * Fast path if size == 16.
> + */
> +noinline unsigned long crypto_mem_not_equal(const void *a, const void *b, size_t size)
I think this should really return unsigned or int, to reduce the risk
that the upper bytes are truncated because the caller uses an
inappropriate type, resulting in a bogus zero result. Reducing the
value to 0/1 probably doesn't hurt performance too much. It also
doesn't encode any information about the location of the difference in
the result value, which helps if that ever leaks.
next prev parent reply other threads:[~2013-09-15 15:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 18:38 [PATCH] crypto_memcmp: add constant-time memcmp James Yonan
2013-09-10 18:57 ` Daniel Borkmann
2013-09-11 12:19 ` Marcelo Cerri
2013-09-11 17:20 ` James Yonan
2013-09-13 8:33 ` Daniel Borkmann
2013-09-15 15:32 ` [PATCH] crypto_mem_not_equal: add constant-time equality testing of memory regions James Yonan
2013-09-15 15:45 ` Florian Weimer [this message]
2013-09-15 16:59 ` James Yonan
2013-09-16 7:56 ` Daniel Borkmann
2013-09-16 17:10 ` James Yonan
2013-09-17 19:07 ` Daniel Borkmann
2013-09-19 0:13 ` James Yonan
2013-09-19 8:37 ` Daniel Borkmann
2013-09-16 17:25 ` Florian Weimer
2013-09-15 15:38 ` [PATCH] crypto_memcmp: add constant-time memcmp James Yonan
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