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Date: Tue, 08 Aug 2023 17:46:04 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Dionna Amalie Glaze <dionnaglaze@...gle.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@...ux.intel.com>, dhowells@...hat.com,
Brijesh Singh <brijesh.singh@....com>,
Peter Zijlstra <peterz@...radead.org>,
Tom Lendacky <thomas.lendacky@....com>,
Borislav Petkov <bp@...en8.de>,
Jarkko Sakkinen <jarkko@...nel.org>,
Samuel Ortiz <sameo@...osinc.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-coco@...ts.linux.dev, keyrings@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] keys: Introduce a keys frontend for attestation
reports
On Tue, 2023-08-08 at 13:04 -0700, Dionna Amalie Glaze wrote:
> > Trusting the vTPM is a one time thing. Once trust in the TPM is
> > established, you don't need to be worried about replay and you can
> > just use standard TPM primitives for everything onward, even when
> > doing point in time runtime attestation.
> >
>
> It's a one time thing for who?
Well, in TLS-TPM it tends to be a one time thing per endpoint
regardless of number of connections.
> It seems like you're still only looking at the 1. use case and not
> the 2. use case. Every different person establishing a connection
> with the service will need to independently establish trust in the
> TPM.
For an ephemeral TPM, the EK should be guaranteed to be random and
therefore non repeating, so there's not much need for the nonce to add
non-repeatability. So, in theory, the vTPM/EK binding can be published
once and relied on even for multiple different tenant endpoints, sort
of like the EK cert for a physical TPM.
James
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