batch-verify BLS to execution change messages (#4637)

beacon_chain/consensus_object_pools/block_clearance.nim

@@ -260,7 +260,7 @@ proc addHeadBlock*(
     var sigs: seq[SignatureSet]
     if (let e = sigs.collectSignatureSets(
         signedBlock, dag.db.immutableValidators,
-        dag.clearanceState, cache); e.isErr()):
+        dag.clearanceState, dag.cfg.genesisFork(), cache); e.isErr()):
       # A PublicKey or Signature isn't on the BLS12-381 curve
       info "Unable to load signature sets",
         err = e.error()

beacon_chain/consensus_object_pools/exit_pool.nim

@@ -15,6 +15,8 @@ import
   ../spec/[helpers, state_transition_block],
   "."/[attestation_pool, blockchain_dag]
 
+from ../spec/beaconstate import check_bls_to_execution_change
+
 export base, deques, blockchain_dag
 
 const
@@ -184,7 +186,7 @@ proc validateValidatorChangeMessage(
 proc validateValidatorChangeMessage(
     cfg: RuntimeConfig, state: ForkyBeaconState,
     msg: SignedBLSToExecutionChange): bool =
-  check_bls_to_execution_change(cfg, state, msg).isOk
+  check_bls_to_execution_change(cfg.genesisFork, state, msg, {}).isOk
 
 proc getValidatorChangeMessagesForBlock(
     subpool: var Deque, cfg: RuntimeConfig, state: ForkyBeaconState,

beacon_chain/gossip_processing/batch_validation.nim

@@ -456,3 +456,39 @@ proc scheduleContributionChecks*(
         contribution.beacon_block_root, contributionKey, contributionSig)
 
   ok((aggregatorFut, proofFut, contributionFut, contributionSig))
+
+proc scheduleBlsToExecutionChangeCheck*(
+      batchCrypto: ref BatchCrypto,
+      genesisFork: Fork, genesis_validators_root: Eth2Digest,
+      signedBLSToExecutionChange: SignedBLSToExecutionChange): Result[tuple[
+       blsToExecutionFut: Future[BatchResult],
+       sig: CookedSig], cstring] =
+  ## Schedule crypto verification of all signatures in a
+  ## SignedBLSToExecutionChange message
+  ##
+  ## The buffer is processed:
+  ## - when eager processing is enabled and the batch is full
+  ## - otherwise after 10ms (BatchAttAccumTime)
+  ##
+  ## This returns an error if crypto sanity checks failed
+  ## and a future with the deferred check otherwise.
+
+  # Must be genesis fork
+  doAssert genesis_fork.previous_version == genesis_fork.current_version
+
+  let
+    # Only called when matching already-known withdrawal credentials, so it's
+    # resistant to allowing loadWithCache DoSing
+    validatorChangePubkey =
+      signedBLSToExecutionChange.message.from_bls_pubkey.loadWithCache.valueOr:
+        return err("scheduleBlsToExecutionChangeCheck: cannot load BLS to withdrawals pubkey")
+
+    validatorChangeSig = signedBLSToExecutionChange.signature.load().valueOr:
+      return err("scheduleBlsToExecutionChangeCheck: invalid validator change signature")
+    validatorChangeFut = batchCrypto.withBatch("scheduleContributionAndProofChecks.contribution"):
+      bls_to_execution_change_signature_set(
+        genesis_fork, genesis_validators_root,
+        signedBLSToExecutionChange.message,
+        validatorChangePubkey, validatorChangeSig)
+
+  ok((validatorChangeFut, validatorChangeSig))

beacon_chain/gossip_processing/eth2_processor.nim

@@ -403,15 +403,17 @@ proc processSignedAggregateAndProof*(
     err(v.error())
 
 proc processBlsToExecutionChange*(
-    self: var Eth2Processor, src: MsgSource,
+    self: ref Eth2Processor, src: MsgSource,
-    blsToExecutionChange: SignedBLSToExecutionChange): ValidationRes =
+    blsToExecutionChange: SignedBLSToExecutionChange):
+    Future[ValidationRes] {.async.} =
   logScope:
     blsToExecutionChange = shortLog(blsToExecutionChange)
 
   debug "BLS to execution change received"
 
-  let v = self.validatorChangePool[].validateBlsToExecutionChange(
+  let v = await self.validatorChangePool[].validateBlsToExecutionChange(
-    blsToExecutionChange, self.getCurrentBeaconTime().slotOrZero.epoch)
+    self.batchCrypto, blsToExecutionChange,
+    self.getCurrentBeaconTime().slotOrZero.epoch)
 
   if v.isOk():
     trace "BLS to execution change validated"
@@ -422,7 +424,7 @@ proc processBlsToExecutionChange*(
     debug "Dropping BLS to execution change", validationError = v.error
     beacon_attester_slashings_dropped.inc(1, [$v.error[0]])
 
-  v
+  return v
 
 proc processAttesterSlashing*(
     self: var Eth2Processor, src: MsgSource,

beacon_chain/gossip_processing/gossip_validation.nim

@@ -814,8 +814,9 @@ proc validateAggregate*(
 
 # https://github.com/ethereum/consensus-specs/blob/v1.3.0-rc.2/specs/capella/p2p-interface.md#bls_to_execution_change
 proc validateBlsToExecutionChange*(
-    pool: ValidatorChangePool, signed_address_change: SignedBLSToExecutionChange,
+    pool: ValidatorChangePool, batchCrypto: ref BatchCrypto,
-    wallEpoch: Epoch): Result[void, ValidationError] =
+    signed_address_change: SignedBLSToExecutionChange,
+    wallEpoch: Epoch): Future[Result[void, ValidationError]] {.async.} =
   # [IGNORE] `current_epoch >= CAPELLA_FORK_EPOCH`, where `current_epoch` is
   # defined by the current wall-clock time.
   if not (wallEpoch >= pool.dag.cfg.CAPELLA_FORK_EPOCH):
@@ -834,11 +835,28 @@ proc validateBlsToExecutionChange*(
       return errIgnore("validateBlsToExecutionChange: can't validate against pre-Capella state")
     else:
       let res = check_bls_to_execution_change(
-        pool.dag.cfg, forkyState.data, signed_address_change)
+        pool.dag.cfg.genesisFork, forkyState.data, signed_address_change,
+        {skipBlsValidation})
       if res.isErr:
         return errReject(res.error)
 
-  ok()
+    # BLS to execution change signatures are batch-verified
+    let deferredCrypto = batchCrypto.scheduleBlsToExecutionChangeCheck(
+      pool.dag.cfg.genesisFork, pool.dag.genesis_validators_root,
+      signed_address_change)
+    if deferredCrypto.isErr():
+      return checkedReject(deferredCrypto.error)
+
+    let (cryptoFut, sig) = deferredCrypto.get()
+    case await cryptoFut
+    of BatchResult.Invalid:
+      return checkedReject("validateBlsToExecutionChange: invalid signature")
+    of BatchResult.Timeout:
+      return errIgnore("validateBlsToExecutionChange: timeout checking signature")
+    of BatchResult.Valid:
+      discard  # keep going only in this case
+
+  return ok()
 
 # https://github.com/ethereum/consensus-specs/blob/v1.3.0-rc.2/specs/phase0/p2p-interface.md#attester_slashing
 proc validateAttesterSlashing*(

beacon_chain/nimbus_beacon_node.nim

@@ -1543,11 +1543,13 @@ proc installMessageValidators(node: BeaconNode) =
     installSyncCommitteeeValidators(forkDigests.eip4844)
 
   template installBlsToExecutionChangeValidators(digest: auto) =
-    node.network.addValidator(
+    node.network.addAsyncValidator(
       getBlsToExecutionChangeTopic(digest),
-      proc(msg: SignedBLSToExecutionChange): ValidationResult =
+      proc(msg: SignedBLSToExecutionChange):
+          Future[ValidationResult] {.async.} =
         return toValidationResult(
-          node.processor[].processBlsToExecutionChange(MsgSource.gossip, msg)))
+          await node.processor.processBlsToExecutionChange(
+            MsgSource.gossip, msg)))
 
   installBlsToExecutionChangeValidators(forkDigests.capella)
   if node.dag.cfg.DENEB_FORK_EPOCH != FAR_FUTURE_EPOCH:

beacon_chain/spec/beaconstate.nim

@@ -696,6 +696,35 @@ proc check_attestation*(
 
   ok()
 
+# https://github.com/ethereum/consensus-specs/blob/v1.3.0-rc.2/specs/capella/beacon-chain.md#new-process_bls_to_execution_change
+proc check_bls_to_execution_change*(
+    genesisFork: Fork, state: capella.BeaconState | eip4844.BeaconState,
+    signed_address_change: SignedBLSToExecutionChange, flags: UpdateFlags):
+    Result[void, cstring] =
+  let address_change = signed_address_change.message
+
+  if not (address_change.validator_index < state.validators.lenu64):
+    return err("process_bls_to_execution_change: invalid validator index")
+
+  var withdrawal_credentials =
+    state.validators.item(address_change.validator_index).withdrawal_credentials
+
+  if not (withdrawal_credentials.data[0] == BLS_WITHDRAWAL_PREFIX):
+    return err("process_bls_to_execution_change: invalid withdrawal prefix")
+
+  if not (withdrawal_credentials.data.toOpenArray(1, 31) ==
+      eth2digest(address_change.from_bls_pubkey.blob).data.toOpenArray(1, 31)):
+    return err("process_bls_to_execution_change: invalid withdrawal credentials")
+
+  doAssert flags + {skipBlsValidation} == {skipBlsValidation}
+  if  skipBlsValidation notin flags and
+      not verify_bls_to_execution_change_signature(
+        genesisFork, state.genesis_validators_root, signed_address_change,
+        address_change.from_bls_pubkey, signed_address_change.signature):
+    return err("process_bls_to_execution_change: invalid signature")
+
+  ok()
+
 func get_proposer_reward*(state: ForkyBeaconState,
                           attestation: SomeAttestation,
                           base_reward_per_increment: Gwei,

beacon_chain/spec/signatures.nim

@@ -368,12 +368,13 @@ proc verify_builder_signature*(
   blsVerify(pubkey, signing_root.data, signature)
 
 # https://github.com/ethereum/consensus-specs/blob/v1.3.0-rc.2/specs/capella/beacon-chain.md#new-process_bls_to_execution_change
-func compute_bls_to_execution_change_signing_root(
+func compute_bls_to_execution_change_signing_root*(
     genesisFork: Fork, genesis_validators_root: Eth2Digest,
     msg: BLSToExecutionChange): Eth2Digest =
   # So the epoch doesn't matter when calling get_domain
   doAssert genesisFork.previous_version == genesisFork.current_version
 
+  # Fork-agnostic domain since address changes are valid across forks
   let domain = get_domain(
     genesisFork, DOMAIN_BLS_TO_EXECUTION_CHANGE, GENESIS_EPOCH,
     genesis_validators_root)

beacon_chain/spec/signatures_batch.nim

@@ -202,11 +202,21 @@ func contribution_and_proof_signature_set*(
 
   SignatureSet.init(pubkey, signing_root, signature)
 
-func collectSignatureSets*(
+func bls_to_execution_change_signature_set*(
+    genesisFork: Fork, genesis_validators_root: Eth2Digest,
+    msg: BLSToExecutionChange,
+    pubkey: CookedPubKey, signature: CookedSig): SignatureSet =
+  let signing_root = compute_bls_to_execution_change_signing_root(
+    genesisFork, genesis_validators_root, msg)
+
+  SignatureSet.init(pubkey, signing_root, signature)
+
+proc collectSignatureSets*(
        sigs: var seq[SignatureSet],
        signed_block: ForkySignedBeaconBlock,
        validatorKeys: auto,
        state: ForkedHashedBeaconState,
+       genesis_fork: Fork,
        cache: var StateCache): Result[void, cstring] =
   ## Collect all signature verifications that process_block would normally do
   ## except deposits, in one go.
@@ -218,7 +228,8 @@ func collectSignatureSets*(
   ## - Attester slashings
   ## - Attestations
   ## - VoluntaryExits
-  ## - SyncCommittee (altair+)
+  ## - SyncCommittee (Altair+)
+  ## - BLS to execution changes (Capella+)
   ##
   ## We do not include deposits as they can be invalid while still leaving the
   ## block valid
@@ -235,6 +246,8 @@ func collectSignatureSets*(
       return err("collectSignatureSets: invalid proposer index")
     epoch = signed_block.message.slot.epoch()
 
+  doAssert genesis_fork.previous_version == genesis_fork.current_version
+
   # 1. Block proposer
   # ----------------------------------------------------
   sigs.add block_signature_set(
@@ -395,6 +408,27 @@ func collectSignatureSets*(
               signed_block.message.body.sync_aggregate.sync_committee_signature.load().valueOr do:
                 return err("collectSignatureSets: cannot load signature"))
 
+  block:
+    # 8. BLS to execution changes
+    when typeof(signed_block).toFork() >= ConsensusFork.Capella:
+      withState(state):
+        when stateFork >= ConsensusFork.Capella:
+          for bls_change in signed_block.message.body.bls_to_execution_changes:
+            let sig = bls_change.signature.load.valueOr:
+              return err("collectSignatureSets: cannot load BLS to execution change signature")
+
+            # Otherwise, expensive loadWithCache can be spammed with irrelevant pubkeys
+            ? check_bls_to_execution_change(
+              genesis_fork, forkyState.data, bls_change, {skipBlsValidation})
+
+            let validator_pubkey =
+              bls_change.message.from_bls_pubkey.loadWithCache.valueOr:
+                return err("collectSignatureSets: cannot load BLS to execution change pubkey")
+
+            sigs.add bls_to_execution_change_signature_set(
+              genesis_fork, genesis_validators_root, bls_change.message,
+              validator_pubkey, sig)
+
   ok()
 
 proc batchVerify*(verifier: var BatchVerifier, sigs: openArray[SignatureSet]): bool =

beacon_chain/spec/state_transition_block.nim

@@ -387,36 +387,11 @@ proc process_voluntary_exit*(
   ? initiate_validator_exit(cfg, state, exited_validator, cache)
   ok()
 
-# https://github.com/ethereum/consensus-specs/blob/v1.3.0-alpha.1/specs/capella/beacon-chain.md#new-process_bls_to_execution_change
-proc check_bls_to_execution_change*(
-    cfg: RuntimeConfig, state: capella.BeaconState | eip4844.BeaconState,
-    signed_address_change: SignedBLSToExecutionChange): Result[void, cstring] =
-  let address_change = signed_address_change.message
-
-  if not (address_change.validator_index < state.validators.lenu64):
-    return err("process_bls_to_execution_change: invalid validator index")
-
-  var withdrawal_credentials =
-    state.validators.item(address_change.validator_index).withdrawal_credentials
-
-  if not (withdrawal_credentials.data[0] == BLS_WITHDRAWAL_PREFIX):
-    return err("process_bls_to_execution_change: invalid withdrawal prefix")
-
-  if not (withdrawal_credentials.data.toOpenArray(1, 31) ==
-      eth2digest(address_change.from_bls_pubkey.blob).data.toOpenArray(1, 31)):
-    return err("process_bls_to_execution_change: invalid withdrawal credentials")
-
-  if not verify_bls_to_execution_change_signature(
-      cfg.genesisFork, state.genesis_validators_root, signed_address_change,
-      address_change.from_bls_pubkey, signed_address_change.signature):
-    return err("process_bls_to_execution_change: invalid signature")
-
-  ok()
-
 proc process_bls_to_execution_change*(
     cfg: RuntimeConfig, state: var (capella.BeaconState | eip4844.BeaconState),
     signed_address_change: SignedBLSToExecutionChange): Result[void, cstring] =
-  ? check_bls_to_execution_change(cfg, state, signed_address_change)
+  ? check_bls_to_execution_change(
+    cfg.genesisFork, state, signed_address_change, {})
   let address_change = signed_address_change.message
   var withdrawal_credentials =
     state.validators.item(address_change.validator_index).withdrawal_credentials

beacon_chain/validators/message_router.nim

@@ -459,7 +459,7 @@ proc routeBlsToExecutionChange*(
     bls_to_execution_change: SignedBLSToExecutionChange):
     Future[SendResult] {.async.} =
   block:
-    let res = router[].processor[].processBlsToExecutionChange(
+    let res = await router.processor.processBlsToExecutionChange(
       MsgSource.api, bls_to_execution_change)
     if not res.isGoodForSending:
       warn "BLS to execution change request failed validation",