fix(consensus): prevent double-commit of equivocating blocks in Linearizer #24499
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…rizer The Linearizer could double-commit equivocating blocks at the same (Round, Author) slot because is_committed() checks full BlockRef including Digest. Two blocks with same slot but different digests were treated as separate blocks. Fix: Add is_any_block_at_slot_committed() check to filter ancestors where any block at that slot has already been committed. Attack scenario: 1. Byzantine validator creates Block A (Round 1), commits via main chain 2. Same validator creates Block B (Round 1, different digest) 3. Block B propagates through side chain 4. Later leader commits Block B even though slot was already committed The fix ensures only one block per (Round, Author) slot can be committed. Fixes MystenLabs#24498 Signed-off-by: SherlockShemol <[email protected]>
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Description
This PR fixes a safety vulnerability where the Linearizer could double-commit equivocating blocks at the same (Round, Author) slot.
Fixes #24498
Problem
In
linearize_sub_dag(), the commit status check usesis_committed(BlockRef)which includes the Digest:Since two equivocating blocks have different digests, they are treated as different blocks. If Block A is committed first,
is_committed(Block B)still returnsfalse, allowing Block B to be committed later through a different DAG path.Solution
Added
is_any_block_at_slot_committed(Slot)method to check if ANY block at a given (Round, Author) slot has been committed, regardless of digest:Changes
dag_state.rs: Addis_any_block_at_slot_committed()methodlinearizer.rs: Add trait method and use it inlinearize_sub_dag()test_dag_builder.rs: Implement trait method for test mockequivocation_commit_test.rs: Add test casesTest Plan
cargo test -p consensus-core equivocation_commit- New tests passcargo test -p consensus-core linearizer- Existing tests pass