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yogeshbdeshpande / draft-cca-rats-endorsements

Arm CCA Endorsements Draft
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Clarify whether Arm CCA platform config is mandatory or optional? #2

Open yogeshbdeshpande opened 2 weeks ago

yogeshbdeshpande commented 2 weeks ago

In the CCA Endorsement draft it is not clear whether the supply chain has to provide Arm CCA Platform Configuration or one can omit if the Config Parameter is not used..?

As per RMM specification: The CCA platform config claim is expected to contain the System Properties field which is present in the Root Non-volatile Storage (RNVS) public parameters.

This issue tracks need for a clear documentation of this aspect in the next revision of the specification!

thomas-fossati commented 2 weeks ago

There are at least three things to tease out about this claim:

  1. Exact semantics
  2. Optionality
  3. Matching criteria
yogeshbdeshpande commented 2 weeks ago

I am not convinced about item 3. The Platform Config, as received in Evidence should be an exact match of the Config as supplied in Reference Value, so 3. is not really something to tease about!

thomas-fossati commented 2 weeks ago

I am not convinced about item 3. The Platform Config, as received in Evidence should be an exact match of the Config as supplied in Reference Value, so 3. is not really something to tease about!

If the config ID is organised as a bitmap, with bit positions indicating specific platform features/settings, it makes sense for the verifier to check that only those of interest are enabled, and be neutral about others.