Fix BLST bindings: Error handling for infinite values of sigs and vks

[curiecrypt]

Content

If there is any identity element in the following vectors:

let transmuted_vks: Vec<blst_p2> = vks.iter().map(vk_from_p2_affine).collect();
let transmuted_sigs: Vec<blst_p1> = signatures.iter().map(sig_to_p1).collect();

The content of the following vectors in mithril-stm/src/multi_sig.rs:

let grouped_vks = p2_affines::from(transmuted_vks.as_slice());
let grouped_sigs = p1_affines::from(transmuted_sigs.as_slice());

Becomes vectors full of identity elements.

This PR includes the changes to avoid having an identity element in signature and verification lists.

In mithril-stm/src/multi_sig.rs:

• Signature::verify function is updated: If signature is an infinity value, it returns an error.
• VerificationKeyPoP::check function is updated: If the verification key is an infinity value, it returns an error.
• test_infinity_sig test is added.
• test_infinity_vk test is added.
• test_keyreg_with_infinity_vk test is added.

In mithril-stm/src/error.rs:

• MultiSignatureError is updated to cover
  • SignatureInfinity
  • VerificationKeyInfinity
• impl From<MultiSignatureError> for StmSignatureError is updated.
• impl<D: Digest + FixedOutput> From<MultiSignatureError> for StmAggregateSignatureError<D> is updated.
• impl From<MultiSignatureError> for CoreVerifierError is updated.
• pub(crate) fn blst_err_to_mithril is updated.

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • Update README file (if relevant)
  • Update documentation website (if relevant)
  • Add dev blog post (if relevant)

Issue(s)

Closes #2321

[github-actions]

Test Results

    3 files  ±0     56 suites  ±0   11m 29s ⏱️ + 1m 5s
1 729 tests +3  1 729 ✅ +3  0 💤 ±0  0 ❌ ±0 
2 125 runs  +3  2 125 ✅ +3  0 💤 ±0  0 ❌ ±0 

Results for commit d0d7787. ± Comparison against base commit 62ae79e.

♻️ This comment has been updated with latest results.

[jpraynaud]

LGTM 👍