On November 4, 2021 9:35 PM, Xu Min wrote:
> On November 4, 2021 4:21 PM, Gerd Hoffmann wrote:
> > Hi,
> >
> > > [SAMI] Apologies, I missed this in my previous review. I think the
> > > behaviour if both the TCG2 and CC measurement protocols are
> > > installed would be inconsistent between DxeTpmMeasurementLib and
> > > DxeTpm2MeasureBootLib. The main difference being in the later, the
> > > TCG2 protocol takes precedence for extending the measurement.
> >
> > Yes, we should have consistent behavior in both cases.
> In DxeTpmMeasurementLib, Cc measurement protocol is used as the first try. If
> it fails, then it try to measure with TCG2 / TCG protocol in turn.
> In DxeTpm2MeasureBootLib, TCG2 protocol is used the as the first try. If it
> fails,
> CC measurement protocol is tried in turn.
> Yes, this is inconsistent. I will update DxeTpm2MeasureBootLib to try Cc
> measurement protocol first, then try TCG2 protocol if Cc measurement protocol
> fails. In this way, only one protocol will be called to do the measurement.
> But
> TCG2 protocol is the first try, CC measurement protocol is the second try.
>
> >
> > > I think it would be good to modify DxeTpm2MeasureBootLib so that the
> > > CC measurement protocol is used if both protocols are installed.
> > > What do you think?
> >
> > Does it makes sense to use both protocols?
> Agree with Gerd. I don't think we should use both protocols to do the
> measurement.
> My suggestion is that, first try CC protocol, if it fails, then try TCG2
> protocol. Just
> as I explained above.
Another option will be that:
In DxeTpmMeasurementLib the pseudo would look like:
If (CC Protocol is installed) {
Status = CcMeasureAndLogData (...)
} else { // below is the original code
Status = Tpm20MeasureAndLogData (...)
If (EFI_ERROR (Status)) {
Status = Tpm12MeasureAndLogData (...)
}
}
In DxeTpm2MeasureBootLib, the pseudo would look like:
If (CC Protocol is installed) {
Status = DoCcMeasureBoot(...)
} else if (TCG2 protocol is installed) {
Status = DoTcg2MeasureBoot(...)
}
Sami & Gerd
What's your thougth?
Thanks
Min
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#83340): https://edk2.groups.io/g/devel/message/83340
Mute This Topic: https://groups.io/mt/86758672/21656
Group Owner: [email protected]
Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]]
-=-=-=-=-=-=-=-=-=-=-=-
