add test for sync aggregate with bad domain in signature

tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_aggregate.py

@@ -63,6 +63,29 @@ def get_committee_indices(spec, state, duplicates=False):
         state.randao_mixes[randao_index] = hash(state.randao_mixes[randao_index])
 
 
+@with_altair_and_later
+@spec_state_test
+@always_bls
+def test_invalid_signature_bad_domain(spec, state):
+    committee_indices = compute_committee_indices(spec, state, state.current_sync_committee)
+    rng = random.Random(2020)
+    random_participant = rng.choice(committee_indices)
+
+    block = build_empty_block_for_next_slot(spec, state)
+    # Exclude one participant whose signature was included.
+    block.body.sync_aggregate = spec.SyncAggregate(
+        sync_committee_bits=[index != random_participant for index in committee_indices],
+        sync_committee_signature=compute_aggregate_sync_committee_signature(
+            spec,
+            state,
+            block.slot - 1,
+            committee_indices,  # full committee signs
+            domain_type=spec.DOMAIN_BEACON_ATTESTER,
+        )
+    )
+    yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
+
+
 @with_altair_and_later
 @spec_state_test
 @always_bls

tests/core/pyspec/eth2spec/test/helpers/sync_committee.py

@@ -7,8 +7,10 @@ from eth2spec.test.helpers.block import (
 from eth2spec.utils import bls
 
 
-def compute_sync_committee_signature(spec, state, slot, privkey, block_root=None):
-    domain = spec.get_domain(state, spec.DOMAIN_SYNC_COMMITTEE, spec.compute_epoch_at_slot(slot))
+def compute_sync_committee_signature(spec, state, slot, privkey, block_root=None, domain_type=None):
+    if not domain_type:
+        domain_type = spec.DOMAIN_SYNC_COMMITTEE
+    domain = spec.get_domain(state, domain_type, spec.compute_epoch_at_slot(slot))
     if block_root is None:
         if slot == state.slot:
             block_root = build_empty_block_for_next_slot(spec, state).parent_root
@@ -18,7 +20,7 @@ def compute_sync_committee_signature(spec, state, slot, privkey, block_root=None
     return bls.Sign(privkey, signing_root)
 
 
-def compute_aggregate_sync_committee_signature(spec, state, slot, participants, block_root=None):
+def compute_aggregate_sync_committee_signature(spec, state, slot, participants, block_root=None, domain_type=None):
     if len(participants) == 0:
         return spec.G2_POINT_AT_INFINITY
 
@@ -32,6 +34,7 @@ def compute_aggregate_sync_committee_signature(spec, state, slot, participants,
                 slot,
                 privkey,
                 block_root=block_root,
+                domain_type=domain_type,
             )
         )
     return bls.Aggregate(signatures)