From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with archive (Exim 4.43) id 1LaQ8C-0000nV-BW for mharc-grub-devel@gnu.org; Fri, 20 Feb 2009 02:49:08 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LaQ8A-0000mF-PR for grub-devel@gnu.org; Fri, 20 Feb 2009 02:49:06 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LaQ88-0000l2-P0 for Grub-devel@gnu.org; Fri, 20 Feb 2009 02:49:06 -0500 Received: from [199.232.76.173] (port=54026 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LaQ88-0000kj-JD for Grub-devel@gnu.org; Fri, 20 Feb 2009 02:49:04 -0500 Received: from xsmtp1.ethz.ch ([82.130.70.13]:39682) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LaQ87-0002mr-GU for Grub-devel@gnu.org; Fri, 20 Feb 2009 02:49:04 -0500 Received: from xfe1.d.ethz.ch ([82.130.124.41]) by xsmtp1.ethz.ch with Microsoft SMTPSVC(6.0.3790.3959); Fri, 20 Feb 2009 08:49:02 +0100 Received: from [192.168.2.75] ([81.221.97.38]) by xfe1.d.ethz.ch over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959); Fri, 20 Feb 2009 08:49:01 +0100 Message-ID: <499E6007.9050902@student.ethz.ch> Date: Fri, 20 Feb 2009 08:47:19 +0100 From: Jan Alsenz User-Agent: Thunderbird 2.0.0.19 (X11/20090104) MIME-Version: 1.0 To: grub-devel References: <499DB343.9020301@gmail.com> <499DF97E.1080800@student.ethz.ch> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig72A23DE0A467A1F8F00E80AE" X-OriginalArrivalTime: 20 Feb 2009 07:49:01.0824 (UTC) FILETIME=[B2245000:01C9932F] X-detected-operating-system: by monty-python.gnu.org: Windows 2000 SP4, XP SP1+ Cc: Alex Besogonov Subject: Re: A _good_ and valid use for TPM X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: The development of GRUB 2 List-Id: The development of GRUB 2 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Feb 2009 07:49:06 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig72A23DE0A467A1F8F00E80AE Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Alex Besogonov wrote: [skip] >>> As far as I understand - no. >> Actually - it is. >> Check the "TCG PC Client Specific Implementation Specification for Con= ventional >> Bios" or "TCG PC Specific Implementation Specification" at >> https://www.trustedcomputinggroup.org/specs/PCClient/ >> and look for CRTM (Core Root of Trust for Measurement) > Yes, BIOS is a root of trust, but not the Core Root. BIOS itself is > checked before execution (pages 20 and onwards in the "TCG PC Client > Specific Implementation Specification for Conventional Bios" spec), > even before dynamic memory is initialized. Well on page 32 they list two options, how to implement the CRTM: BIOS Boot Block or entire BIOS Since the BIOS is usually updateable, it seems that most manufacturers op= t for BIOS Boot Block, which I assume will be something like: "lets put the fir= st sector of the BIOS in ROM" (of course it might be something else completely, but I doubt it) >>> First, I don't think it's possible to implement SHA-1 hashing in MBR = - >>> there's probably just not enough space left in 512-byte code segment >>> for that. >> I am very sure of that. > Well, I spoke phcoder on Jabber - there might be a way to do this. > He's going to investigate it. Sounds interesting. >>> Second, the only safe action non TPM-aware MBR can perform if it >>> detects tampering is just shutting down hard. Everything else is >>> dangerous. >> Yeah, but an attacker could patch that out too. > Not if we first measure the MBR. It can be done without any > TPM-specific code in the MBR if I'm not very mistaken. Could you elaborate on that? E.g. where do you measure the MBR from? > PS: thanks for detailed explanation! Sure, glad I could help! Greets, Jan --------------enig72A23DE0A467A1F8F00E80AE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkmeYBkACgkQfZylhtn4Xvc7MgCgxfLwrA9zfQZweG1AKPXZqNG7 JsAAoJxW7V66Xzg9hozVZCvpM7P5bQLF =bFaV -----END PGP SIGNATURE----- --------------enig72A23DE0A467A1F8F00E80AE--