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 6AB53C77B7A for ; Tue, 16 May 2023 14:05:45 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pyvIc-0003Lf-Vc; Tue, 16 May 2023 10:05:11 -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 1pyvIa-0003Jb-EO for qemu-devel@nongnu.org; Tue, 16 May 2023 10:05:08 -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 1pyvIY-0007DY-La for qemu-devel@nongnu.org; Tue, 16 May 2023 10:05:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684245905; 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=PgJulrzMqYNd6jbtIUiixZc6s/hIvgkOlxp7QoT/Mec=; b=CcFDBH4FCG8baIgzHBWeVWzijhlqkpRXFTqmBXAmoNW2cWJ4XWiDQsdpl6VuW1iGCyMSys SOpsxOeUu+6pXyOKhNBR/tniI/XSKQtPuTB3tHUACFhHcMd7onXb0C/ntH6rlrbCva3GCc Kow5YdSCa6JiBJm8inQVHl6OZaBWu/4= 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-609-TWdRMHKoO5m5OAn675MNMg-1; Tue, 16 May 2023 10:04:48 -0400 X-MC-Unique: TWdRMHKoO5m5OAn675MNMg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4BA67185A79C; Tue, 16 May 2023 14:04:41 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.91]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2A03C492B00; Tue, 16 May 2023 14:04:41 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 02FCC21E6806; Tue, 16 May 2023 16:04:40 +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> Date: Tue, 16 May 2023 16:04:39 +0200 In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Tue, 16 May 2023 11:29:49 +0100") Message-ID: <87ilcspe2w.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 10.11.54.9 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 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 (which >> > requires elevated privilleges that QEMU lacks). NB, libvirt would fetch >> > 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. 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. However, I now wonder why we fetch it from QEMU. Why not ship it with QEMU? > IOW, if we're trying to mitigate against compromised QEMU, we > *must* fetch it before vCPUs are started. If we're super paranoid, > we would want to fetch it before even opening untrusted disk images > too. It might push towards fetching it while probing capabilities > from a throw-away QEMU with "-m none" [...]