From: Phillip Susi <psusi@cfl.rr.com>
To: Andrew Lutomirski <luto@myrealbox.com>
Cc: Theodore Tso <tytso@mit.edu>,
David Newall <david@davidnewall.com>,
John Reiser <jreiser@bitwagon.com>,
Matt Mackall <mpm@selenic.com>,
linux-kernel@vger.kernel.org, security@kernel.org
Subject: Re: /dev/urandom uses uninit bytes, leaks user data
Date: Thu, 20 Dec 2007 15:17:02 -0500 [thread overview]
Message-ID: <476ACDBE.2070600@cfl.rr.com> (raw)
In-Reply-To: <cb0375e10712192018l66671b34r1680077765e89fb0@mail.gmail.com>
Andrew Lutomirski wrote:
> I understand that there's no way that /dev/random can provide good
> output if there's insufficient entropy. But it still shouldn't leak
> arbitrary bits of user data that were never meant to be put into the
> pool at all.
It doesn't leak it though, it consumes it, and it then vanishes into the
entropy pool, never to be seen again.
> Step 1: Boot a system without a usable entropy source.
> Step 2: add some (predictable) "entropy" from userspace which isn't a
> multiple of 4, so up to three extra bytes get added.
> Step 3: Read a few bytes of /dev/random and send them over the network.
Only root can do 1 and 2, at which point, it's already game over.
next prev parent reply other threads:[~2007-12-20 20:17 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-14 19:34 /dev/urandom uses uninit bytes, leaks user data 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 [this message]
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
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
-- strict thread matches above, loose matches on Subject: below --
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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