[svsm-devel] vTPM service attestation format update

[James Bottomley]

On Fri, 2025-03-07 at 11:48 +0000, Geoffrey Ndu wrote:
> Since the single_service_manifest call for the vTPM effectively
> certifies EKs, why don’t the “selector” be the handle values for EK
> certificates, as specified by the TCG in 2.2.2.5.1 of “TCG EK
> Credential Profile For TPM Family 2.0; Level 0”? This approach would
> simplify the user experience, as every SVSM would function
> identically, and  SVSM vTPMs would exhibit analogous behaviour to
> physical TPMs.

Because to make life easier we might want to short circuit the EK/AK
makecredential/activatecredential round trip and simply construct a
signing EK to use in place of an arbitrary AK.  Then to make the
signing EK easily useful, we might want it not to have a policy
statement tying it to the endorsement hierarchy password (particularly
as we know that will be empty).  To allow this type of thing we need to
allow flexibility in the EK creation which isn't listed in the TCG
profile EK templates.

Regards,

James