Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754716AbXLIBJU (ORCPT ); Sat, 8 Dec 2007 20:09:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752969AbXLIBJM (ORCPT ); Sat, 8 Dec 2007 20:09:12 -0500 Received: from dallas.jonmasters.org ([72.29.103.172]:42411 "EHLO dallas.jonmasters.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753074AbXLIBJK (ORCPT ); Sat, 8 Dec 2007 20:09:10 -0500 Subject: Re: entropy gathering (was Re: Why does reading from /dev/urandom deplete entropy so much?) From: Jon Masters To: Theodore Tso Cc: Willy Tarreau , Jeff Garzik , Matt Mackall , Mike McGrath , Alan Cox , Ray Lee , Adrian Bunk , Marc Haber , linux-kernel@vger.kernel.org, hmh@debian.org In-Reply-To: <20071208234721.GR17037@thunk.org> References: <20071204223345.GJ19691@waste.org> <4756B50B.3060100@redhat.com> <20071205144934.GL7259@thunk.org> <1197099477.20786.149.camel@perihelion> <20071208173204.GI17037@thunk.org> <475AD585.7020908@redhat.com> <20071208174908.GJ17037@thunk.org> <20071208181525.GL19691@waste.org> <475AF241.5000809@garzik.org> <20071208204239.GG15227@1wt.eu> <20071208234721.GR17037@thunk.org> Content-Type: text/plain Organization: World Organi[sz]ation Of Broken Dreams Date: Sat, 08 Dec 2007 20:07:51 -0500 Message-Id: <1197162471.12636.6.camel@perihelion> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 (2.12.0-3.fc8) Content-Transfer-Encoding: 7bit X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 74.92.29.237 X-SA-Exim-Mail-From: jonathan@jonmasters.org X-SA-Exim-Scanned: No (on dallas.jonmasters.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1463 Lines: 35 On Sat, 2007-12-08 at 18:47 -0500, Theodore Tso wrote: > On Sat, Dec 08, 2007 at 09:42:39PM +0100, Willy Tarreau wrote: > > I remember having installed openssh on an AIX machines years ago, and > > being amazed by the number of sources it collected entropy from. Simple > > commands such as "ifconfig -a", "netstat -i" and "du -a", "ps -ef", "w" > > provided a lot of entropy. > > Well.... not as many bits of entropy as you might think. But every > little bit helps, especially if some of it is not available to > adversary. I was always especially fond of the "du" entropy source with Solaris installations of OpenSSH (the PRNG used commands like "du" too). It was always amusing that a single network outage at the University would prevent anyone from ssh'ing into the "UNIX" machines. So yeah, if we want to take a giant leap backwards, I suggest jumping at this. Lots of these are not actually random - you can guess the free space on a network drive in some certain cases, you know what processes are likely to be created on a LiveCD, and many dmesg outputs are very similar, especially when there aren't precie timestamps included. But I do think it's time some of this got addressed :-) Cheers, Jon. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/