attestation: add options to the EnforceIDKeyDigest config field to enable Microsoft Azure Attestation fallback when verifying AMD SNP-SEV id key digest

[daniel-weisse]

Proposed change(s)

• Change the EnforceIDKeyDigest option in the Constellation config from boolean to an enum. The following values are available (naming not final, looking for feedback/suggestions):
  • StrictChecking: requires the IDKeyDigest of the node to be in the list of trusted IDKeyDigests, error otherwise
  • MAAFallback: if a node's IDKeyDigest is not in the list of trusted digests, MAA is used to verify the SNP properties of the VM.
  • WarnOnly: emit a warning, but accept IDKeyDigests not in the list of trusted digests
• Enable MAA fallback in SNP attestation Validator
  • This requires some changes to the internal Validator API, mainly the GetTPMTrustedAttestationPublicKey and GetInstanceInfo functions now also accept extraData (userData hashed with nonce)

Additional info

• blocked until MAA issues are resolved on our node images

Checklist

• Update docs
• Add labels (e.g., for changelog category)
• Link to Milestone

[netlify]

✅ Deploy Preview for constellation-docs canceled.

Name	Link
🔨 Latest commit	09ec59f
🔍 Latest deploy log	https://app.netlify.com/sites/constellation-docs/deploys/641997e43ff90500081ac290

[malt3]

Just a heads-up: This branch should be rebased before merge and bazel build files should be generated.
This document has up-to-date information on the required tasks (bazel run gazelle).

[thomasten]

we should also think about renaming the key, but not sure what this means for backwards compat

[derpsteb]

Would be a breaking change from my pov. Maybe we can rename it when implementing #1436?
For that one we will need migration docs/code anyways.

EDIT: Oh. This requires migration docs/code already :D

[daniel-weisse]

Did a bunch of manual testing, but there is also this e2e test: https://github.com/edgelesssys/constellation/actions/runs/4417455739
It doesnt cover actually using the MAA fallback, but should make sure the new configs are set correctly.
For manual testing, one has to set the constellation-maa-url tag to the url of a MAA provider manually (at least until the changes from #1409 are in main)