Re: [PATCH] tpm: enable HMAC encryption for only x86-64 and aarch64

[James Bottomley]

On Tue, 2024-05-21 at 17:02 +0300, Jarkko Sakkinen wrote:
> Secondly, it also roots to the null key if a parent is not given. So
> it covers all the basic features of the HMAC patch set.

I don't think that can work.  The key file would be wrapped to the
parent and the null seed (and hence the wrapping) changes with every
reboot.  If you want a permanent key, it has to be in one of the
accessible permanent hierarchies (storage ideally or endorsement).

The spec has a mechanism for deriving the key from a permanent handle
if the system doesn't have it in-place.  I do have patches to use that
because that's the way most sealed objects and keys are generated
today.  I'll post them (although there'll be a bit of fixing up to do).

Regards,

James