[Xen-users] Re: Exploiting XEN

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Petersson, Mats wrote:

> I guess that's a fair comment too. Dom0 is a large part of a Xen
> environment, and if Dom0 is compromised, then Xen can't really do that
> much to prevent the system from being crashed, subverted or other
> malicious acts. But I believe Xen itself is "safe" from Dom0 being
> compromised
It's not.  Dom0 (or any IO domain) has direct access to DMA controllers. 
 It can use DMA to overwrite the hypervisor's memory with arbitrary data.
It would be rather trivial for dom0 to escalate itself to ring 0 by 
simply locating the IDT, writing a new IDT to disk, and then doing a DMA 
read operation with the physical address of the IDT's.
Regards,

Anthony Liguori

 - but it's moot point, as Xen on it's own is about as useful
> as a chocalte teapot. 
>
> But Xen isn't really the "culprit" in this scenario - it's the same
> scenario for Linux (or whatever other OS we care to choose) without a
> hypervisor.
>
> --
> Mats
> > Dan.
> > --
> > |=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 
> > 978 392 2496 -=|
> > |=-           Perl modules: http://search.cpan.org/~danberr/  
> >             -=|
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