From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261977AbULKRdp (ORCPT ); Sat, 11 Dec 2004 12:33:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261978AbULKRdp (ORCPT ); Sat, 11 Dec 2004 12:33:45 -0500 Received: from thunk.org ([69.25.196.29]:64919 "EHLO thunker.thunk.org") by vger.kernel.org with ESMTP id S261977AbULKRd2 (ORCPT ); Sat, 11 Dec 2004 12:33:28 -0500 Date: Sat, 11 Dec 2004 12:33:17 -0500 From: "Theodore Ts'o" To: Adam Heath Cc: Matt Mackall , Bernard Normier , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: Concurrent access to /dev/urandom Message-ID: <20041211173317.GA28382@thunk.org> Mail-Followup-To: Theodore Ts'o , Adam Heath , Matt Mackall , Bernard Normier , linux-kernel@vger.kernel.org, Andrew Morton References: <20041208192126.GA5769@thunk.org> <20041208215614.GA12189@waste.org> <20041209015705.GB6978@thunk.org> <20041209212936.GO8876@waste.org> <20041210044759.GQ8876@waste.org> <20041210163558.GB10639@thunk.org> <20041210182804.GT8876@waste.org> <20041210212815.GB25409@thunk.org> <20041210222306.GV8876@waste.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 10, 2004 at 06:22:37PM -0600, Adam Heath wrote: > > Actually, I think this is a security issue. Since any plain old program can > read from /dev/urandom at any time, an attacker could attempt to read from > that device at the same moment some other program is doing so, and thereby > gain some knowledge as to the other program's state. It could be a potential exploit, but.... (a) it only applies on SMP machines (b) it's not a remote exploit; the attacker needs to have the ability to run arbitrary programs on the local machine (c) the attacker won't get all of other programs' reads of /dev/urandom, and (d) the attacker would have to have a program continuously reading from /dev/urandom, which would take up enough CPU time that it would be rather hard to hide. That's not to say that we shouldn't fix it at our earliest convenience, and I'd urge Andrew to push this to Linus for 2.6.10 --- but I don't think we need to move heaven and earth to try to accelerate the 2.6.10 release process, either. - Ted