Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver

Kai Huang
2022-04-19T23:02:55Z

On Tue, 2022-04-19 at 15:49 -0700, Dave Hansen wrote:
> On 4/19/22 15:21, Kai Huang wrote:
> > On Tue, 2022-04-19 at 07:13 -0700, Dave Hansen wrote:
> > > On 4/19/22 00:47, Kai Huang wrote:
> > > > > From security's perspective, attestation is an essential part of TDX. That
> > > > being said, w/o attestation support in TD guest, I guess nobody will seriously
> > > > use TD guest.
> > > Are you saying you can't think of a single threat model where there's a
> > > benefit to running a TDX guest without attestation? Will TDX only be
> > > used in environments where secrets are provisioned to guests on the
> > > basis of attestation?
> > >
> > I don't think anyone should provision secret to a TD before it get attested that
> > it is a genuine TD that he/she expected. If someone does that, he/she takes the
> > risk of losing the secret. Of course if someone just want to try a TD then w/o
> > attestation is totally fine.
>
> Yeah, but you said:
>
> w/o attestation support in TD guest, I guess nobody will
> seriously use TD guest.
>
> I'm trying to get to the bottom of that. That's a much more broad
> statement than something about when it's safe to deploy secrets.
>
> There are lots of secrets deployed in (serious) VMs today. There are
> lots of secrets deployed in (serious) SEV VMs that don't have
> attestation. Yet, the world somehow hasn't come crashing down.
>
> I think it's crazy to say that nobody will deploy secrets to TDX VMs
> without attestation. I think it's a step father into crazy land to say
> that no one will "seriously" use TDX guests without attestation.
>
> Let's be honest about this and not live in some fantasy world, please.

OK agree. No argument about this.

--
Thanks,
-Kai