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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF48EC636CD for ; Wed, 1 Feb 2023 14:48:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pNEEy-00086i-Qp; Wed, 01 Feb 2023 09:37:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pNEDA-0005V5-Pz for qemu-devel@nongnu.org; Wed, 01 Feb 2023 09:35:48 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pNED3-00042Y-Dz for qemu-devel@nongnu.org; Wed, 01 Feb 2023 09:35:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675262135; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=G78sh9k2aYU7/sirb3voCyPm+703BKxdk5K8LUpkvFY=; b=RO6diWYDd8b9RqjsUVJXKX2bzRTY7LSx8cxuy+liVtUizWREdJVWqIBP8YMwuclXXLWhNF US05SQatxtLjC08QJW0zUqwXEaFnGt68avQMmLRmvl0a53qwIHLI7RDJWQKqMPUXIa1JZc ZMJNr271rZXoVUhD2b+74WFKTUr63Ik= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-663-KEGG-iovNeqvIuKBoVvGew-1; Wed, 01 Feb 2023 09:35:32 -0500 X-MC-Unique: KEGG-iovNeqvIuKBoVvGew-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DDE8585CBE1; Wed, 1 Feb 2023 14:35:31 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BBC16404CD80; Wed, 1 Feb 2023 14:35:30 +0000 (UTC) Date: Wed, 1 Feb 2023 14:35:28 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: James Bottomley Cc: qemu-devel@nongnu.org, Gerd Hoffmann , DOV MURIK , "Jason A. Donenfeld" Subject: Re: [PATCH] x86: fix q35 kernel measurements broken due to rng seeding Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Feb 01, 2023 at 08:57:10AM -0500, James Bottomley wrote: > The origin commit for rng seeding 67f7e426e5 ("hw/i386: pass RNG seed > via setup_data entry") modifies the kernel image file to append a > random seed. Obviously this makes the hash of the kernel file > non-deterministic and so breaks both measured and some signed boots. I recall raising that at the time https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg00710.html and Jason pointed me to a followup which I tested and believe fixed it for SEV: https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg00601.html but it doesn't look like that second patch ever merged. We went through so many patches I think it probably got obsoleted by something else, and no one rechecked SEV again. > The commit notes it's only for non-EFI (because EFI has a different > RNG seeding mechanism) so, since there are no non-EFI q35 systems, this > should be disabled for the whole of the q35 machine type to bring back > deterministic kernel file hashes. SeaBIOS is the default firmware for both q35 and i440fx. The majority of systems using q35 will be non-EFI today, and that is what the random seed was intended to address. I don't think we can just disable this for the whole of q35. When you say it breaks measured / signed boots, I presume you are specifically referring to SEV kernel hashes measurements ? Or is there a more general problem to solve ? > Obviously this still leaves the legacy bios case broken for at least > measured boot, but I don't think anyone cares about that now. > > Signed-off-by: James Bottomley > --- > hw/i386/pc_q35.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c > index 83c57c6eb1..11e8dd7ca7 100644 > --- a/hw/i386/pc_q35.c > +++ b/hw/i386/pc_q35.c > @@ -357,6 +357,7 @@ static void pc_q35_machine_options(MachineClass *m) > pcmc->default_nic_model = "e1000e"; > pcmc->pci_root_uid = 0; > pcmc->default_cpu_version = 1; > + pcmc->legacy_no_rng_seed = true; > > m->family = "pc_q35"; > m->desc = "Standard PC (Q35 + ICH9, 2009)"; > @@ -394,9 +395,7 @@ DEFINE_Q35_MACHINE(v7_2, "pc-q35-7.2", NULL, > > static void pc_q35_7_1_machine_options(MachineClass *m) > { > - PCMachineClass *pcmc = PC_MACHINE_CLASS(m); > pc_q35_7_2_machine_options(m); > - pcmc->legacy_no_rng_seed = true; > compat_props_add(m->compat_props, hw_compat_7_1, > hw_compat_7_1_len); > compat_props_add(m->compat_props, pc_compat_7_1, > pc_compat_7_1_len); > } This patch changes behaviour of the pc-q35-7.2 machine type. Any change will need to be in latest development 8.0 machine type only With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|