From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: David Laight <David.Laight@ACULAB.COM>,
"Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Netdev <netdev@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
"Daniel J . Bernstein" <djb@cr.yp.to>,
Linus Torvalds <torvalds@linux-foundation.org>,
Eric Biggers <ebiggers3@gmail.com>
Subject: Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function
Date: Thu, 15 Dec 2016 16:53:12 +0100 [thread overview]
Message-ID: <924ef794-eae0-2a6b-508b-069718339edc@stressinduktion.org> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DB0240529@AcuExch.aculab.com>
On 15.12.2016 16:41, David Laight wrote:
> Try (retyped):
>
> echo 'struct { long a; long long b; } s; int bar { return sizeof s; }' >foo.c
> gcc [-m32] -O2 -S foo.c; cat foo.s
>
> And look at what is generated.
I used __alignof__(unsigned long long) with -m32.
>> Right now ipv6 addresses have an alignment of 4. So we couldn't even
>> naturally pass them to siphash but would need to copy them around, which
>> I feel like a source of bugs.
>
> That is more of a problem on systems that don't support misaligned accesses.
> Reading the 64bit values with two explicit 32bit reads would work.
> I think you can get gcc to do that by adding an aligned(4) attribute to the
> structure member.
Yes, and that is actually my fear, because we support those
architectures. I can't comment on that as I don't understand enough of this.
If someone finds a way to cause misaligned reads on a small box this
seems (maybe depending on sysctls they get fixed up or panic) to be a
much bigger issue than having a hash DoS.
Thanks,
Hannes
next prev parent reply other threads:[~2016-12-15 15:53 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-14 3:59 [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 2/4] siphash: add convenience functions for jhash converts Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 3/4] secure_seq: use siphash24 instead of md5_transform Jason A. Donenfeld
2016-12-14 12:53 ` Jason A. Donenfeld
2016-12-14 13:16 ` Hannes Frederic Sowa
2016-12-14 13:44 ` Jason A. Donenfeld
2016-12-14 14:47 ` David Laight
2016-12-14 17:49 ` Jason A. Donenfeld
2016-12-14 17:56 ` David Miller
2016-12-14 18:06 ` Jason A. Donenfeld
2016-12-14 19:22 ` Hannes Frederic Sowa
2016-12-14 19:38 ` Jason A. Donenfeld
2016-12-14 20:27 ` Hannes Frederic Sowa
2016-12-14 20:12 ` Tom Herbert
2016-12-14 21:01 ` Jason A. Donenfeld
2016-12-14 3:59 ` [PATCH v2 4/4] random: use siphash24 instead of md5 for get_random_int/long Jason A. Donenfeld
2016-12-14 11:21 ` [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa
2016-12-14 13:10 ` Jason A. Donenfeld
2016-12-14 15:09 ` Hannes Frederic Sowa
2016-12-14 19:47 ` Jason A. Donenfeld
2016-12-15 7:57 ` Herbert Xu
2016-12-15 8:15 ` [kernel-hardening] " Daniel Micay
2016-12-14 12:46 ` Jason A. Donenfeld
2016-12-14 22:03 ` Hannes Frederic Sowa
2016-12-14 23:29 ` Jason A. Donenfeld
2016-12-15 8:31 ` Hannes Frederic Sowa
2016-12-15 11:04 ` David Laight
2016-12-15 12:23 ` Hannes Frederic Sowa
2016-12-15 12:28 ` David Laight
2016-12-15 12:50 ` Hannes Frederic Sowa
2016-12-15 13:56 ` David Laight
2016-12-15 14:56 ` Hannes Frederic Sowa
2016-12-15 15:41 ` David Laight
2016-12-15 15:53 ` Hannes Frederic Sowa [this message]
2016-12-15 18:50 ` Jason A. Donenfeld
2016-12-15 20:31 ` Hannes Frederic Sowa
2016-12-15 20:43 ` Jason A. Donenfeld
2016-12-15 21:04 ` Peter Zijlstra
2016-12-15 21:09 ` Hannes Frederic Sowa
2016-12-15 21:17 ` Hannes Frederic Sowa
2016-12-15 21:09 ` Peter Zijlstra
2016-12-15 21:11 ` [kernel-hardening] " Jason A. Donenfeld
2016-12-15 21:14 ` Linus Torvalds
2016-12-14 18:46 ` [PATCH v3 1/3] " Jason A. Donenfeld
2016-12-14 18:46 ` [PATCH v3 2/3] secure_seq: use siphash24 instead of md5_transform Jason A. Donenfeld
2016-12-14 21:44 ` kbuild test robot
2016-12-14 18:46 ` [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long Jason A. Donenfeld
2016-12-14 21:56 ` kbuild test robot
2016-12-14 21:57 ` kbuild test robot
2016-12-15 10:14 ` David Laight
2016-12-15 18:51 ` Jason A. Donenfeld
2016-12-14 19:18 ` [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Tom Herbert
2016-12-14 19:35 ` Jason A. Donenfeld
2016-12-14 20:55 ` Jason A. Donenfeld
2016-12-14 21:35 ` Tom Herbert
2016-12-14 22:56 ` Jason A. Donenfeld
2016-12-14 23:14 ` Tom Herbert
2016-12-14 23:17 ` Jason A. Donenfeld
2016-12-18 0:06 ` Christian Kujau
2016-12-14 23:30 ` Linus Torvalds
2016-12-14 23:34 ` Jason A. Donenfeld
2016-12-15 0:10 ` Linus Torvalds
2016-12-15 10:22 ` David Laight
2016-12-14 21:15 ` kbuild test robot
2016-12-14 21:21 ` Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 1/4] " Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 2/4] siphash: add N[qd]word helpers Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 3/4] secure_seq: use siphash instead of md5_transform Jason A. Donenfeld
2016-12-15 1:46 ` [PATCH v4 4/4] random: use siphash instead of MD5 for get_random_int/long Jason A. Donenfeld
2016-12-15 4:23 ` [PATCH v4 1/4] siphash: add cryptographically secure hashtable function kbuild test robot
2016-12-15 21:25 [PATCH v2 " Jason A. Donenfeld
2016-12-15 21:45 ` Hannes Frederic Sowa
2016-12-15 23:43 ` Jason A. Donenfeld
2016-12-16 0:03 ` Hannes Frederic Sowa
2016-12-15 23:47 ` Jason A. Donenfeld
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