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Date: Mon, 18 Jul 2016 17:49:00 -0700
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From: Matthew Garrett <mjg59@coreos.com>
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Subject: Re: [Qemu-devel] [PATCH] hw/misc: Add simple measurement hardware
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To: Stefan Berger <stefanb@us.ibm.com>
Cc: stefanb@linux.vnet.ibm.com, qemu-devel@nongnu.org, "Daniel P. Berrange" <berrange@redhat.com>, pbonzini@redhat.com, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

On Jul 18, 2016 17:46, "Stefan Berger" <stefanb@us.ibm.com> wrote:
>
>
> Matthew Garrett <mjg59@coreos.com> wrote on 07/18/2016 08:39:07 PM:
>
>
> >
> > On Jul 18, 2016 17:08, "Stefan Berger" <stefanb@us.ibm.com> wrote:
> > > The point of the TPM is that the device that holds the state of
> > the PCRs provides the signatures over their state rather than some
> > other 'entity' whose trustworthiness wouldn't be clear. Admittedly
> > the device comes with its own set of challenges.
>
> > The hypervisor holds the PCR state and also provides the signature.
> > If the hypervisor is untrustworthy than the state of the virtualised
> > system can never be verified, since it could simply have faked the
> > measurements passed to whatever the root of trust is.
>
> So the hypervisor will have the key for signing and provide the quote ?

Either the hypervisor itself or part of the associated platform. This
framework is typically inside the same trust boundary.