From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hopwood Subject: Re: Fw: Xen on /. again Date: Fri, 21 Jan 2005 00:48:58 +0000 Message-ID: <41F0517A.5080503@blueyonder.co.uk> References: <41F02C8B.5010304@diku.dk> <200501202241.06631.maw48@cl.cam.ac.uk> Reply-To: david.nospam.hopwood@blueyonder.co.uk Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200501202241.06631.maw48@cl.cam.ac.uk> Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org Mark Williamson wrote: >>Also, I suppose you will wish to prevent covert channels between >>domains, e.g. domains communicating using various timing attacks (I move >>the disk head to the other end of the disk if I wish to tell you >>something), or by allocating/freeing certains parts of memory. >> >>How much will you need to dumb down the VMs view of what is going on in >>the machine to achieve this (not expose real time information, not >>expose real page tables), and how much of a VMM will there be left when >>you are done? > > Well domains are not aware of each other's memory usage, so I wouldn't have > thought that allocation / exposing real page tables would matter. (Except > dom0 can of course see everything if it wants). Information about other domains' memory usage is leaked via the hardware->physical mapping. > Timing related attacks are somewhat trickier to eliminate covert channels in, > although some randomisation can limit the bandwidth. Eliminating covert channels is completely infeasible. I don't see any value in aiming for this. It's not a useful security property in most circumstances. -- David Hopwood ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl