Re: [Xen-devel] [RFC PATCH 0/18] Xenstore stub domain

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-01-12 at 10:48 +0000, Tim Deegan wrote:
> At 11:33 +0100 on 12 Jan (1326367997), Joanna Rutkowska wrote:
> > Daniel,
> > 
> > Can you explain what is the rationale for moving the xenstored into a
> > stubdom? After all, if an attacker is able to compromise the xenstored,
> > there should be many ways now how to compromise other VMs in the system?
> > And it shouldn't matter whether the xenstored is in stubdom or whether
> > in Dom0. E.g. the attacker might redirect the block fronts to us some
> > false block backends, so that the VMs get compromised fs. One could
> > probably think of other attacks as well...?
> 
> I think the point is to protect xenstore from dom0, not dom0 from
> xenstore.  With stub-xenstore and driver domains, only the domain
> builder and PCIback need to have any privilege, and they can be moved
> out of dom0 too (e.g., http://dl.acm.org/citation.cfm?id=1346278 ,
> http://tjd.phlegethon.org/words/sosp11-xoar.html)

Also by isolating components you gain the ability to restart them
independently. Since xenstored is one of (the only?) dom0 component
which cannot be trivially restarted so putting it in a separate domain
means you can restart dom0.

Ian.



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