From owner-freebsd-hackers@FreeBSD.ORG Tue Feb 26 19:08:13 2008 Return-Path: Delivered-To: hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 808A0106566B; Tue, 26 Feb 2008 19:08:13 +0000 (UTC) (envelope-from gregoryd.freebsd@free.fr) Received: from postfix1-g20.free.fr (postfix1-g20.free.fr [212.27.60.42]) by mx1.freebsd.org (Postfix) with ESMTP id 0AF9613C4CE; Tue, 26 Feb 2008 19:08:12 +0000 (UTC) (envelope-from gregoryd.freebsd@free.fr) Received: from smtp1-g19.free.fr (smtp1-g19.free.fr [212.27.42.27]) by postfix1-g20.free.fr (Postfix) with ESMTP id 9B84A232A9BC; Tue, 26 Feb 2008 19:42:26 +0100 (CET) Received: from smtp1-g19.free.fr (localhost.localdomain [127.0.0.1]) by smtp1-g19.free.fr (Postfix) with ESMTP id A5E981AB2B2; Tue, 26 Feb 2008 19:42:24 +0100 (CET) Received: from imp8-g19.free.fr (imp8-g19.free.fr [212.27.42.39]) by smtp1-g19.free.fr (Postfix) with ESMTP id 3511E1AB30D; Tue, 26 Feb 2008 19:42:24 +0100 (CET) Received: by imp8-g19.free.fr (Postfix, from userid 33) id 3B2AF3DD1; Tue, 26 Feb 2008 19:42:18 +0100 (CET) Received: from 145.242.11.2 ([145.242.11.2]) by imp.free.fr (IMP) with HTTP for ; Tue, 26 Feb 2008 19:42:17 +0100 Message-ID: <1204051337.47c45d89ea6eb@imp.free.fr> Date: Tue, 26 Feb 2008 19:42:17 +0100 From: gregoryd.freebsd@free.fr To: Eygene Ryabinkin References: <20080223010856.7244.qmail@smasher.org> <47C068B5.2090000@thedarkside.nl> <20080223185620.GA98105@eos.sc1.parodius.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit User-Agent: Internet Messaging Program (IMP) 3.2.8 X-Originating-IP: 145.242.11.2 Cc: Jeremy Chadwick , hackers@freebsd.org, Pieter de Boer , Atom Smasher Subject: Re: Zeroing sensitive memory chunks [Was: Security Flaw in Popular Disk Encryption Technologies] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Feb 2008 19:08:13 -0000 Quoting Eygene Ryabinkin : > *) New function OPENSSL_cleanse(), which is used to cleanse a section of > memory from it's contents. This is done with a counter that will > place alternating values in each byte. This can be used to solve > two issues: 1) the removal of calls to memset() by highly optimizing > compilers, and 2) cleansing with other values than 0, since those can > be read through on certain media, for example a swap space on disk. > [Geoff Thorpe] > > The '1)' is what I was talking about. '2)' is not very clear to > me now, I should research what Geoff meant. If anyone has an idea, > please comment. I thought it might mean that on certain media, such as disks, data can be read even after it has been overwriten a certain number of times (magnetic properties of the media, this is a method used by some police labs to recover lost data, I've been told, but maybe the man was just a paranoid). So even "cleansing" a crypted swap space this way would not render it safe (you would have to repeat it enough times so that the layers are definitively overwritten) Now I am no physics/chemics specialist, and this might not be the meaning of Geoff Thorpe: anyway you asked for an idea :-) And I would also like to know the end of it... gregory