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 13FACC7EE2A for ; Tue, 16 May 2023 15:07:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pywG6-0001dy-3K; Tue, 16 May 2023 11:06:38 -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 1pywG0-0001d6-5H for qemu-devel@nongnu.org; Tue, 16 May 2023 11:06:32 -0400 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 1pywFy-0002kx-OP for qemu-devel@nongnu.org; Tue, 16 May 2023 11:06:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684249589; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2ZuK9iiVVg/uCFA85oKnDYSnzsHywZ7y2bdMTaBVy4w=; b=GD5dgp2/zLzKZIeHu7twA4BdZePwji1IIhFyAiUDKSG/JQpv5oecDn+Pzg5dem+06hWhqh Dx35gj8tMv/0pCcRxDcO++k8OrnSuJdFbHK9s+oWRW9l5gC7yBsIgfOAIJoi7oyhs8AyzO 8jk3hLdBMFLGSAyFy+l1QdLigVqNgGw= 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-533-L0IIi2KeOaeS0zREZZe3ZQ-1; Tue, 16 May 2023 11:06:26 -0400 X-MC-Unique: L0IIi2KeOaeS0zREZZe3ZQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 08BEB10146E3; Tue, 16 May 2023 15:06:26 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.91]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DB81640C2063; Tue, 16 May 2023 15:06:25 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id CE60521E66E3; Tue, 16 May 2023 17:06:24 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: Andrew Melnychenko , jasowang@redhat.com, mst@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org, yuri.benditovich@daynix.com, yan@daynix.com Subject: Re: [PATCH v2 5/6] qmp: Added new command to retrieve eBPF blob. References: <20230512122902.34345-1-andrew@daynix.com> <20230512122902.34345-6-andrew@daynix.com> <87zg64u0g7.fsf@pond.sub.org> <87ilcsshgf.fsf@pond.sub.org> <87ilcspe2w.fsf@pond.sub.org> Date: Tue, 16 May 2023 17:06:24 +0200 In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Tue, 16 May 2023 15:35:05 +0100") Message-ID: <87lehonwnj.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Tue, May 16, 2023 at 04:04:39PM +0200, Markus Armbruster wrote: >> Daniel P. Berrang=C3=A9 writes: >>=20 >> > On Tue, May 16, 2023 at 12:23:28PM +0200, Markus Armbruster wrote: >> >> Daniel P. Berrang=C3=A9 writes: >> >>=20 >> >> > On Tue, May 16, 2023 at 10:47:52AM +0200, Markus Armbruster wrote: >> >>=20 >> >> [...] >> >>=20 >> >> >> So, this is basically a way to retrieve an eBPF program by some >> >> >> well-known name. >> >> >>=20 >> >> >> Ignorant question: how are these programs desposited? >> >> > >> >> > The eBPF code blob is linked into QEMU at build time. THis API lets >> >> > libvirt fetch it from QEMU, in base64 format. When libvirt later >> >> > creates NICs, it can attach the eBPF code blob to the TAP device (w= hich >> >> > requires elevated privilleges that QEMU lacks). NB, libvirt would f= etch >> >> > the eBPF code from QEMU when probing capabilities, as once a VM is >> >> > running it is untrusted. >> >>=20 >> >> Okay, I can see how that helps. I trust the blob is in a read-only >> >> segment. Ideally, libvirt fetches it before the guest runs. >> > >> > Whether the blob is in a read-only segment or not isn't important, >> > because it transits writable memory in the QMP command marshalling. >>=20 >> True. We could bypass marshalling. Unclean hack. Or we could sign the >> bits cryptograhically. Key management headaches. Not worth it, because >> fetching it before QEMU becomes untrusted is easier. >>=20 >> However, I now wonder why we fetch it from QEMU. Why not ship it with >> QEMU? > > Fetching it from QEMU gives us a strong guarantee that the eBPF > code actually matches the QEMU binary we're talking to, which is > useful if you're dealing with RPMs which can be upgraded behind > your back, or have multiple parallel installs of QEMU. Yes, but what makes this one different from all the other things that need to match?