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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 A8B95C49ED7 for ; Mon, 16 Sep 2019 13:17:31 +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 7EED620644 for ; Mon, 16 Sep 2019 13:17:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EED620644 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]:34016 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i9qsk-0002L3-EX for qemu-devel@archiver.kernel.org; Mon, 16 Sep 2019 09:17:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39539) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i9qqh-0001ea-Nx for qemu-devel@nongnu.org; Mon, 16 Sep 2019 09:15:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i9qqe-0005c3-5q for qemu-devel@nongnu.org; Mon, 16 Sep 2019 09:15:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53364) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i9qqd-0005bL-TX for qemu-devel@nongnu.org; Mon, 16 Sep 2019 09:15:20 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8720F3090FC2; Mon, 16 Sep 2019 13:15:18 +0000 (UTC) Received: from work-vm (unknown [10.36.118.111]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E1A7F5C1D6; Mon, 16 Sep 2019 13:15:16 +0000 (UTC) Date: Mon, 16 Sep 2019 14:15:14 +0100 From: "Dr. David Alan Gilbert" To: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Message-ID: <20190916131514.GG2887@work-vm> References: <20190912122514.22504-1-marcandre.lureau@redhat.com> <20190912122514.22504-6-marcandre.lureau@redhat.com> <20190916100035.GC2887@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 16 Sep 2019 13:15:18 +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 v3 5/6] docs: start a document to describe D-Bus usage 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: "Daniel P. Berrange" , Juan Quintela , Michal Privoznik , QEMU , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Marc-Andr=E9 Lureau (marcandre.lureau@gmail.com) wrote: > Hi >=20 > On Mon, Sep 16, 2019 at 2:02 PM Dr. David Alan Gilbert > wrote: > > > > (Copying in Stefan since he was looking at DBus for virtiofs) > > > > * Marc-Andr=E9 Lureau (marcandre.lureau@redhat.com) wrote: > > > Signed-off-by: Marc-Andr=E9 Lureau > > > --- > > > docs/interop/dbus.rst | 73 ++++++++++++++++++++++++++++++++++++++= ++++ > > > docs/interop/index.rst | 1 + > > > 2 files changed, 74 insertions(+) > > > create mode 100644 docs/interop/dbus.rst > > > > > > diff --git a/docs/interop/dbus.rst b/docs/interop/dbus.rst > > > new file mode 100644 > > > index 0000000000..c08f026edc > > > --- /dev/null > > > +++ b/docs/interop/dbus.rst > > > @@ -0,0 +1,73 @@ > > > +=3D=3D=3D=3D=3D > > > +D-Bus > > > +=3D=3D=3D=3D=3D > > > + > > > +Introduction > > > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > + > > > +QEMU may be running with various helper processes involved: > > > + - vhost-user* processes (gpu, virtfs, input, etc...) > > > + - TPM emulation (or other devices) > > > + - user networking (slirp) > > > + - network services (DHCP/DNS, samba/ftp etc) > > > + - background tasks (compression, streaming etc) > > > + - client UI > > > + - admin & cli > > > + > > > +Having several processes allows stricter security rules, as well a= s > > > +greater modularity. > > > + > > > +While QEMU itself uses QMP as primary IPC (and Spice/VNC for remot= e > > > +display), D-Bus is the de facto IPC of choice on Unix systems. The > > > +wire format is machine friendly, good bindings exist for various > > > +languages, and there are various tools available. > > > + > > > +Using a bus, helper processes can discover and communicate with ea= ch > > > +other easily, without going through QEMU. The bus topology is also > > > +easier to apprehend and debug than a mesh. However, it is wise to > > > +consider the security aspects of it. > > > + > > > +Security > > > +=3D=3D=3D=3D=3D=3D=3D=3D > > > + > > > +A QEMU D-Bus bus should be private to a single VM. Thus, only > > > +cooperative tasks are running on the same bus to serve the VM. > > > + > > > +D-Bus, the protocol and standard, doesn't have mechanisms to enfor= ce > > > +security between peers once the connection is established. Peers m= ay > > > +have additional mechanisms to enforce security rules, based for > > > +example on UNIX credentials. > > > + > > > +dbus-daemon can enforce various policies based on the UID/GID of t= he > > > +processes that are connected to it. It is thus a good idea to run > > > +helpers as different UID from QEMU and set appropriate policies (s= o > > > +helper processes are only allowed to talk to qemu for example). > > > + > > > +For example, this allows only ``qemu`` user to talk to ``qemu-help= er`` > > > +``org.qemu.Helper1`` service: > > > + > > > +.. code:: xml > > > + > > > + > > > + > > > + > > > + > > > + > > > + > > > + > > > + > > > + > > > + > > > +dbus-daemon can also perfom SELinux checks based on the security > > > +context of the source and the target. For example, ``virtiofs_t`` > > > +could be allowed to send a message to ``svirt_t``, but ``virtiofs_= t`` > > > +wouldn't be allowed to send a message to ``virtiofs_t``. > > > > I think we need to start thinking about this more now rather than > > 'can'. . >=20 > Do you have a specific question we can answer or guide for qemu? Is > there something we have to document or implement? >=20 > Since qemu is not managing the extra processes or applying policies, I > don't know what else could be done. From qemu pov, it can rely on > management layer to trust the bus and the helpers, similar to trusting > the system in general. Well pretty much the same questions I asked in the discussion on v2; what is the supported configuration to ensure that one helper that's been compromised can't attack the others and qemu? Dave > > Dave > > > > > +Guidelines > > > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > > + > > > +When implementing new D-Bus interfaces, it is recommended to follo= w > > > +the "D-Bus API Design Guidelines": > > > +https://dbus.freedesktop.org/doc/dbus-api-design.html > > > + > > > +The "org.qemu*" prefix is reserved for the QEMU project. > > > diff --git a/docs/interop/index.rst b/docs/interop/index.rst > > > index b4bfcab417..fa4478ce2e 100644 > > > --- a/docs/interop/index.rst > > > +++ b/docs/interop/index.rst > > > @@ -13,6 +13,7 @@ Contents: > > > :maxdepth: 2 > > > > > > bitmaps > > > + dbus > > > live-block-operations > > > pr-helper > > > vhost-user > > > -- > > > 2.23.0 > > > > > -- > > 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