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 7AB48C4345F for ; Mon, 15 Apr 2024 12:01:04 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rwL0J-0007k2-I5; Mon, 15 Apr 2024 08:00:07 -0400 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 1rwL0I-0007jp-0J for qemu-devel@nongnu.org; Mon, 15 Apr 2024 08:00:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rwL0E-0000M3-3W for qemu-devel@nongnu.org; Mon, 15 Apr 2024 08:00:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1713182397; 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=fvU8E3B83BnGdeHugFlEaCsPpS0YttDvgUvXtVZb1sY=; b=Jfe7AQgfqPieDAUGZj2Pg+ohwSbdzy/up9q52jSzXo7NuSd6orABqWm57qsN4AULpb1Oo6 7/Tvca1jIeut/gh8hWOdeKJIIdxDhF9/FZqpBbEBk7UHPcnhdU1XTgwhrgf82T5mG8WFBj w/qyRV5JatxKyn4MNHD20Ah5+yJ6UUA= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-50-Papqf8NGO0KHgnH3oYmTJg-1; Mon, 15 Apr 2024 07:59:53 -0400 X-MC-Unique: Papqf8NGO0KHgnH3oYmTJg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2EE4F1C07F20; Mon, 15 Apr 2024 11:59:53 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B26341121313; Mon, 15 Apr 2024 11:59:50 +0000 (UTC) Date: Mon, 15 Apr 2024 12:59:44 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Gerd Hoffmann Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Marcel Apfelbaum , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Cole Robinson Subject: Re: secure boot & direct kernel load (was: Re: [PATCH] x86/loader: only patch linux kernels) Message-ID: References: <20240410072126.617063-1-kraxel@redhat.com> <20240410032448-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.185, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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, Apr 10, 2024 at 12:35:13PM +0200, Gerd Hoffmann wrote: > On Wed, Apr 10, 2024 at 03:26:29AM -0400, Michael S. Tsirkin wrote: > > On Wed, Apr 10, 2024 at 09:21:26AM +0200, Gerd Hoffmann wrote: > > > If the binary loaded via -kernel is *not* a linux kernel (in which > > > case protocol == 0), do not patch the linux kernel header fields. > > > > > > It's (a) pointless and (b) might break binaries by random patching > > > and (c) changes the binary hash which in turn breaks secure boot > > > verification. > > > > > > Background: OVMF happily loads and runs not only linux kernels but > > > any efi binary via direct kernel boot. > > > > > > Note: Breaking the secure boot verification is a problem for linux > > > kernels too, but fixed that is left for another day ... > > > > Um we kind of care about Linux ;) > > > > What's the plan? I suspect we should just add a command line flag > > to skip patching? And once we do that, it seems safer to just > > always rely on the flag? > > Well, there are more problems to solve here than just the patching. So > lets have a look at the bigger picture before discussion the details ... > > [ Cc'ing Daniel + Cole ] > > Current state of affairs is that OVMF supports two ways to boot a linux > kernel: > > (1) Just load it as EFI binary and boot via linux kernel EFI stub, > which is the modern way to load a linux kernel (which is why you > can boot not only linux kernels but any efi binary). > > (2) Use the old EFI handover protocol. Which is the RHEL-6 era way to > boot a linux kernel on EFI. > > For method (1) secure boot verification must pass. For (2) not. So if > you try to use direct kernel boot with secure boot enabled OVMF will > first try (1), which will fail, then go fallback to (2). > > The reason for the failure is not only the patching, but also the fact > that the linux kernel is typically verified by shim.efi (and the distro > keys compiled into the binary) instead of the firmware. > > Going though (2) is not ideal for multiple reasons, so we need some > strategy how we'll go handle direct kernel load with uefi and secure > boot in a way that (1) works. > > Options I see: > > (a) Stop using direct kernel boot, let virt-install & other tools > create vfat boot media with shim+kernel+initrd instead. > > (b) Enroll the distro signing keys in the efi variable store, so > booting the kernel without shim.efi works. > > (c) Add support for loading shim to qemu (and ovmf), for example > with a new '-shim' command line option which stores shim.efi > in some new fw_cfg file. The problem with this is that now virt-install has to actually find the correct a shim.efi binary. It is already somewhat hard to find a suitable kerenl+initrd binary, and AFAIK, the places where we get these binaries don't have shim.efi alongside. eg for RHEL/Fedora we grab kernel+initrd from the pxeboot dir: https://fedora.mirrorservice.org/fedora/linux/development/rawhide/Everything/x86_64/os/images/pxeboot/ This same problem with affect both options (a) and (c). In various forums we have discussed adding the secureboot certs to the libosinfo database, so that we can have a customized EFI varstore with minimized certs, even for the ISO / HDD boot scenario. If we do that, then (b) is trivial for direct kernel boot too. (b) kills all birds with the same stone :-) > > (b) + (c) both require a fix for the patching issue. The options > I see here are: > > (A) Move the patching from qemu to the linuxboot option rom. > Strictly speaking it belongs there anyway. It doesn't look > that easy though, for qemu it is easier to gather all > information needed ... > > (B) Provide both patched and unpatched setup header, so the > guest can choose what it needs. > > (C) When implementing (c) above we can piggyback on the -shim > switch and skip patching in case it is present. > > (D) Add a flag to skip the patching. > > Comments? Other/better ideas? I guess (b) + (D) is probably my preference. 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 :|