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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07266C3A5A4 for ; Fri, 23 Aug 2019 14:28:27 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id D026922CE3 for ; Fri, 23 Aug 2019 14:28:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D026922CE3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:56748 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i1AYD-0003xB-P5 for qemu-devel@archiver.kernel.org; Fri, 23 Aug 2019 10:28:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48978) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i1AW3-0002X0-CS for qemu-devel@nongnu.org; Fri, 23 Aug 2019 10:26:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i1AW1-0004Vu-Qt for qemu-devel@nongnu.org; Fri, 23 Aug 2019 10:26:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35238) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i1AW1-0004VO-Ij for qemu-devel@nongnu.org; Fri, 23 Aug 2019 10:26:09 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EC9E430832DC; Fri, 23 Aug 2019 14:26:08 +0000 (UTC) Received: from work-vm (ovpn-117-244.ams2.redhat.com [10.36.117.244]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 08E0C6CE61; Fri, 23 Aug 2019 14:26:04 +0000 (UTC) Date: Fri, 23 Aug 2019 15:26:02 +0100 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Message-ID: <20190823142602.GJ2784@work-vm> References: <20190808150325.21939-1-marcandre.lureau@redhat.com> <20190823112053.GE9654@redhat.com> <20190823114157.GG9654@redhat.com> <20190823130014.GG2784@work-vm> <20190823140948.GI2784@work-vm> <20190823142054.GK9654@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20190823142054.GK9654@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Fri, 23 Aug 2019 14:26:08 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v2 0/2] Add dbus-vmstate X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , Thomas Huth , Juan Quintela , qemu-devel , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > On Fri, Aug 23, 2019 at 03:09:48PM +0100, Dr. David Alan Gilbert wrote: > > * Marc-Andr=E9 Lureau (marcandre.lureau@gmail.com) wrote: > > > Hi > > >=20 > > > On Fri, Aug 23, 2019 at 5:00 PM Dr. David Alan Gilbert > > > wrote: > > > > > > > > * Daniel P. Berrang=E9 (berrange@redhat.com) wrote: > > > > > > > > > > > > > > > > > This means QEMU still has to iterate over every single client > > > > > on the bus to identify them. If you're doing that, there's > > > > > no point in owning a well known service at all. Just iterate > > > > > over the unique bus names and look for the exported object > > > > > path /org/qemu/VMState > > > > > > > > > > > > > Not knowing anything about DBus security, I want to ask how do > > > > we handle security here? > > >=20 > > > First of all, we are talking about cooperative processes, and havin= g a > > > specific bus for each qemu instance. So some amount of security/tru= st > > > is already assumed. > >=20 > > Some but we need to keep it as limited as possible; for example two > > reasons for having separate processes both come down to security: > >=20 > > a) vtpm - however screwy the qemu is, you can never get to the keys= in > > the vtpm >=20 > Processes connected to dbus can only call the DBus APIs that vtpm > actually exports. The vtpm should simply *not* export a DBus > API that allows anything to fetch the keys. >=20 > If it did want to export APIs for fetching keys, then we would > have to ensure suitable dbus /selinux policy was created to > prevent unwarranted access. This was really just one example of where the security/trust isn't assumed; however a more concrete case is migration of a vtpm, and even though it's probably encrypted blob you still don't want some other device to grab the migration data - or to say reinitialise the vtpm. > > b) virtio-gpu, loads of complex GPU code that can't break the main > > qemu process. >=20 > That's no problem - virtio-gpu crashes, it disappears from the dbus > bus, but everything else keeps running. Crashing is the easy case; assume it's malicious and you don't want it getting to say a storage device provided by another vhost-user device. > > > But if necessary, dbus can enforce policies on who is allowed to ow= n a > > > name, or to send/receive message from. As far as I know, this is > > > mostly user/group policies. > > >=20 > > > But there is also SELinux checks to send_msg and acquire_svc (see > > > dbus-daemon(1)) > >=20 > > But how does something like SELinux interact with a private dbus=20 > > rather than the system dbus? >=20 > There's already two dbus-daemon's on each host - the system one and > the session one, and they get different selinux contexts, > system_dbus_t and unconfined_dbus_t. >=20 > Since libvirt would be responsible for launching these private dbus > daemons it would be easy to make it run svirt_dbus_t for example. > Actually it would be svirt_dbus_t:s0:cNNN,cMMM to get uniqueness > per VM. >=20 > Will of course require us to talk to the SELinux maintainers to > get some sensible policy rules created. This all relies on SELinux and running privileged qemu/vhost-user pairs; needing to do that purely to enforce security seems wrong. Dave > > > > I want to know that the external device that's giving me migratio= n data > > > > is the device I think I'm speaking to, not one of the other devic= es; > > >=20 > > > DBus is not the problem nor the solution here. > >=20 > > Well, if the migration data was squirting down the existing vhost-use= r > > channel then there would be no risk here; so the use of dbus is creat= ing > > the problem. > >=20 > > > But what defines that device-service strong relationship? Can you > > > generalize it? I don't think so. > > >=20 > > > What DBus can guarantee is that the unique-id you are talking to is > > > always the same connection (thus the same process). > > >=20 > > > > I also dont want different devices chatting to each other over db= us > > > > unless we're very careful. > > >=20 > > > That's a bus policy job. > >=20 > > OK, as long as you somehow set it up. > >=20 > > Dave > >=20 > > > > > > > > Dave > > > > > > > > > Regards, > > > > > Daniel > > > > > -- > > > > > |: https://berrange.com -o- https://www.flickr.com/phot= os/dberrange :| > > > > > |: https://libvirt.org -o- https://fstop138.= berrange.com :| > > > > > |: https://entangle-photo.org -o- https://www.instagram.c= om/dberrange :| > > > > -- > > > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > > > > > >=20 > > >=20 > > > --=20 > > > Marc-Andr=E9 Lureau > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK >=20 > Regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberr= ange :| > |: https://libvirt.org -o- https://fstop138.berrange= .com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberr= ange :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK