Add three new test files for the Marmot MLS implementation:
- MlsGroupLifecycleTest: End-to-end lifecycle tests covering Welcome
processing, cross-member encrypt/decrypt, multi-member groups, commit
processing, external joins, PSK proposals, and ReInit proposals.
- MlsGroupEdgeCaseTest: Security boundary tests for wrong epoch rejection,
corrupted ciphertext detection, invalid KeyPackage rejection, out-of-range
leaf indices, empty/large message handling, and add/remove/add cycles.
- MlsConformanceTest: Cross-implementation comparison tests verifying
KeyPackage structure, GroupInfo signatures, Welcome message format,
HPKE seal/open, SignWithLabel/VerifyWithLabel, LeafNode signatures,
deterministic key schedule, and commit structure conformance.
Fix GroupInfo signature bug (RFC 9420 Section 12.4.3.1):
- buildWelcome() and groupInfo() were signing only groupContext.toTlsBytes()
but verifySignature() checked against encodeTbs() which includes
GroupContext + extensions + confirmationTag + signer. Now both methods
build an unsigned GroupInfo first and sign its full TBS encoding.
Enhance MlsGroupManager KDoc with usage examples, responsibility breakdown,
and cross-implementation notes.
8 tests are @Ignore'd documenting a known bug: processCommit() does not
derive the same epoch secrets as commit(), causing cross-member AEAD
failures after epoch transitions.
https://claude.ai/code/session_018f67fqNReg3dEXcDimYLY1
Claude
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