Re: [PATCH v2 3/5] virt: sevguest: Prep for kernel internal {get, get_ext}_report()

[Dionna Amalie Glaze]

> Definitely, instead it was this comment from James that gave me pause:
>
> "To get a bit off topic, I'm not sure derived keys are much use.  The
> problem is in SNP that by the time the PSP does the derivation, the key
> is both tied to the physical system and derived from a measurement too
> general to differentiate between VM images (so one VM could read
> another VMs stored secrets)."
>

Key derivation on AMD SEV-SNP is not necessarily tied to a physical
system with the introduction of VLEK-based attestation. It's now tied
to a CSP's fleet of machines. We can use key derivation in the SVSM as
a basis for further key derivation based on measurement registers, so
the utility increases to provide something like persisted sealed data
that can only be unsealed when the SVSM witnesses a particular runtime
measurement configuration.
We can use NIST 800-90A Rev. 1 for combining keys from the PSP with
measurement register values for example.

> http://lore.kernel.org/r/c6576d1682b576ba47556478a98f397ed518a177.camel@xxxxxxxxxxxxxxxxxxxxx




--
-Dionna Glaze, PhD (she/her)