From: "David Schwartz" <davids@webmaster.com>
To: "Theodore Tso" <tytso@mit.edu>, <jreiser@bitwagon.com>
Cc: "Matt Mackall" <mpm@selenic.com>, <linux-kernel@vger.kernel.org>,
<security@kernel.org>
Subject: RE: /dev/urandom uses uninit bytes, leaks user data
Date: Mon, 17 Dec 2007 12:59:04 -0800 [thread overview]
Message-ID: <MDEHLPKNGKAHNMBLJOLKAELOIOAC.davids@webmaster.com> (raw)
In-Reply-To: <4766A40D.4080804@BitWagon.com>
> The bottom line: At a cost of at most three unpredictable branches
> (whether to clear the bytes in the last word with indices congruent
> to 1, 2, or 3 modulo 4), then the code can reduce the risk from something
> small but positive, to zero. This is very inexpensive insurance.
> John Reiser, jreiser@BitWagon.com
Even if you're right, the change isn't free. You've simply presented
evidence of one non-zero benefit of it. You've given no ability to assess
the size of this benefit and no way to figure if it exceeds the cost. There
is also a non-zero *security* cost to this change.
DS
next prev parent reply other threads:[~2007-12-17 20:59 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-14 19:34 John Reiser
2007-12-14 20:13 ` Matt Mackall
2007-12-14 20:45 ` John Reiser
2007-12-14 23:23 ` Theodore Tso
2007-12-15 0:30 ` John Reiser
2007-12-15 4:32 ` Theodore Tso
2007-12-17 16:30 ` John Reiser
2007-12-17 17:36 ` Theodore Tso
2007-12-18 0:52 ` Andy Lutomirski
2007-12-18 3:05 ` Theodore Tso
2007-12-18 3:13 ` David Newall
2007-12-18 3:46 ` Theodore Tso
2007-12-18 4:09 ` David Newall
2007-12-18 4:23 ` Theodore Tso
2007-12-19 22:43 ` Bill Davidsen
2007-12-19 22:40 ` Bill Davidsen
2007-12-20 4:18 ` Andrew Lutomirski
2007-12-20 20:17 ` Phillip Susi
2007-12-21 16:10 ` Andrew Lutomirski
2007-12-22 1:14 ` Theodore Tso
2007-12-26 18:30 ` Phillip Susi
2007-12-20 20:36 ` Theodore Tso
2007-12-27 10:44 ` Pavel Machek
2007-12-18 5:12 ` David Schwartz
2007-12-17 20:59 ` David Schwartz [this message]
2007-12-15 7:13 ` Herbert Xu
2007-12-15 16:30 ` Matt Mackall
2007-12-17 17:28 ` Signed divides vs shifts (Re: [Security] /dev/urandom uses uninit bytes, leaks user data) Linus Torvalds
2007-12-17 17:48 ` Al Viro
2007-12-17 17:55 ` Eric Dumazet
2007-12-17 18:05 ` Ray Lee
2007-12-17 18:10 ` Eric Dumazet
2007-12-17 18:12 ` Ray Lee
2007-12-17 18:23 ` Al Viro
2007-12-17 18:28 ` [Security] Signed divides vs shifts (Re: " Linus Torvalds
2007-12-17 19:08 ` Al Viro
2007-12-15 7:20 /dev/urandom uses uninit bytes, leaks user data Matti Linnanvuori
2007-12-15 7:54 ` Valdis.Kletnieks
2007-12-15 22:44 linux
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