From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C04FC77B7F for ; Fri, 12 May 2023 19:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238477AbjELTMJ (ORCPT ); Fri, 12 May 2023 15:12:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229901AbjELTMI (ORCPT ); Fri, 12 May 2023 15:12:08 -0400 Received: from cavan.codon.org.uk (cavan.codon.org.uk [176.126.240.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 476D86E89; Fri, 12 May 2023 12:12:05 -0700 (PDT) Received: by cavan.codon.org.uk (Postfix, from userid 1000) id C748140A6F; Fri, 12 May 2023 20:12:03 +0100 (BST) Date: Fri, 12 May 2023 20:12:03 +0100 From: Matthew Garrett To: Thomas Gleixner Cc: Ard Biesheuvel , Eric Biggers , Ross Philipson , linux-kernel@vger.kernel.org, x86@kernel.org, linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org, linux-crypto@vger.kernel.org, iommu@lists.linux-foundation.org, kexec@lists.infradead.org, linux-efi@vger.kernel.org, dpsmith@apertussolutions.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, James.Bottomley@hansenpartnership.com, luto@amacapital.net, nivedita@alum.mit.edu, kanth.ghatraju@oracle.com, trenchboot-devel@googlegroups.com Subject: Re: [PATCH v6 06/14] x86: Add early SHA support for Secure Launch early measurements Message-ID: <20230512191203.GA21013@srcf.ucam.org> References: <20230504145023.835096-1-ross.philipson@oracle.com> <20230504145023.835096-7-ross.philipson@oracle.com> <20230510012144.GA1851@quark.localdomain> <20230512110455.GD14461@srcf.ucam.org> <20230512112847.GF14461@srcf.ucam.org> <87pm75bs3v.ffs@tglx> <20230512161318.GA18400@srcf.ucam.org> <873541bej2.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <873541bej2.ffs@tglx> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Fri, May 12, 2023 at 08:17:21PM +0200, Thomas Gleixner wrote: > On Fri, May 12 2023 at 17:13, Matthew Garrett wrote: > > On Fri, May 12, 2023 at 03:24:04PM +0200, Thomas Gleixner wrote: > >> On Fri, May 12 2023 at 12:28, Matthew Garrett wrote: > >> > Unless we assert that SHA-1 events are unsupported, it seems a bit odd > >> > to force a policy on people who have both banks enabled. People with > >> > mixed fleets are potentially going to be dealing with SHA-1 measurements > >> > for a while yet, and while there's obviously a security benefit in using > >> > SHA-2 instead it'd be irritating to have to maintain two attestation > >> > policies. > >> > >> Why? > >> > >> If you have a mixed fleet then it's not too much asked to provide two > >> data sets. On a TPM2 system you can enforce SHA-2 and only fallback to > >> SHA-1 on TPM 1.2 hardware. No? > > > > No, beause having TPM2 hardware doesn't guarantee that your firmware > > enables SHA-2 (which also means this is something that could change with > > firmware updates, which means that refusing to support SHA-1 if the > > SHA-2 banks are enabled could result in an entirely different policy > > being required (and plausibly one that isn't implemented in their > > existing tooling) > > It's not rocket science to have both variants supported in tooling, > really. People who are currently using tboot are only getting SHA-1, so there's no obvious reason for them to have added support yet. *My* tooling all supports SHA-2 so I'm completely fine here, but either we refuse to support a bunch of hardware or we have to support SHA-1 anyway, and if we have to support it the only reason not to implement it even in the "SHA-2 is supported" case is because we have opinions about how other people implement their security.