From 2ca28fb86168848994055696e6c69dadf386ef32 Mon Sep 17 00:00:00 2001
From: tersec <tersec@users.noreply.github.com>
Date: Wed, 8 Dec 2021 17:29:22 +0000
Subject: [PATCH] Merge BeaconBlock gossip validation (#3165)

* Merge BeaconBlock gossip validation

* figure/ground inversion

* revert cosmetic cleanups to reduce merge conflicts
---
 .../block_pools_types.nim                     |  4 ++
 .../consensus_object_pools/blockchain_dag.nim | 10 ++-
 beacon_chain/eth1/eth1_monitor.nim            |  2 +-
 .../gossip_processing/eth2_processor.nim      |  5 +-
 .../gossip_processing/gossip_validation.nim   | 62 +++++++++++++++++--
 beacon_chain/nimbus_beacon_node.nim           |  5 ++
 6 files changed, 78 insertions(+), 10 deletions(-)

diff --git a/beacon_chain/consensus_object_pools/block_pools_types.nim b/beacon_chain/consensus_object_pools/block_pools_types.nim
index d6cedd66b..25063326c 100644
--- a/beacon_chain/consensus_object_pools/block_pools_types.nim
+++ b/beacon_chain/consensus_object_pools/block_pools_types.nim
@@ -177,6 +177,10 @@ type
     eth1_deposit_index*: uint64
     beacon_proposers*: array[SLOTS_PER_EPOCH, Option[ValidatorIndex]]
     shuffled_active_validator_indices*: seq[ValidatorIndex]
+
+    # enables more efficient merge block validation
+    merge_transition_complete*: bool
+
     # balances, as used in fork choice
     effective_balances_bytes*: seq[byte]
 
diff --git a/beacon_chain/consensus_object_pools/blockchain_dag.nim b/beacon_chain/consensus_object_pools/blockchain_dag.nim
index 2539bdbd8..4e586e384 100644
--- a/beacon_chain/consensus_object_pools/blockchain_dag.nim
+++ b/beacon_chain/consensus_object_pools/blockchain_dag.nim
@@ -153,7 +153,15 @@ func init*(
         getStateField(state.data, current_justified_checkpoint),
       finalized_checkpoint: getStateField(state.data, finalized_checkpoint),
       shuffled_active_validator_indices:
-        cache.get_shuffled_active_validator_indices(state.data, epoch)
+        cache.get_shuffled_active_validator_indices(state.data, epoch),
+      merge_transition_complete:
+        case state.data.kind:
+        of BeaconStateFork.Phase0: false
+        of BeaconStateFork.Altair: false
+        of BeaconStateFork.Merge:
+          # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/merge/beacon-chain.md#is_merge_transition_complete
+          state.data.mergeData.data.latest_execution_payload_header !=
+            ExecutionPayloadHeader()
     )
 
   for i in 0'u64..<SLOTS_PER_EPOCH:
diff --git a/beacon_chain/eth1/eth1_monitor.nim b/beacon_chain/eth1/eth1_monitor.nim
index 8d7c86d85..40c71b28e 100644
--- a/beacon_chain/eth1/eth1_monitor.nim
+++ b/beacon_chain/eth1/eth1_monitor.nim
@@ -355,7 +355,7 @@ proc addBlock*(chain: var Eth1Chain, newBlock: Eth1Block) =
   chain.blocksByHash[newBlock.voteData.block_hash.asBlockHash] = newBlock
   eth1_chain_len.set chain.blocks.len.int64
 
-func hash(x: Eth1Data): Hash =
+func hash*(x: Eth1Data): Hash =
   hash(x.block_hash)
 
 template awaitWithRetries*[T](lazyFutExpr: Future[T],
diff --git a/beacon_chain/gossip_processing/eth2_processor.nim b/beacon_chain/gossip_processing/eth2_processor.nim
index d18d0cee4..697b03d21 100644
--- a/beacon_chain/gossip_processing/eth2_processor.nim
+++ b/beacon_chain/gossip_processing/eth2_processor.nim
@@ -12,7 +12,7 @@ import
   stew/results, bearssl,
   chronicles, chronos, metrics, taskpools,
   ../spec/[helpers, forks],
-  ../spec/datatypes/[altair, phase0],
+  ../spec/datatypes/[altair, merge, phase0],
   ../consensus_object_pools/[
     block_clearance, block_quarantine, blockchain_dag, exit_pool, attestation_pool,
     sync_committee_msg_pool],
@@ -172,7 +172,8 @@ proc new*(T: type Eth2Processor,
 
 proc blockValidator*(
     self: var Eth2Processor,
-    signedBlock: phase0.SignedBeaconBlock | altair.SignedBeaconBlock): ValidationRes =
+    signedBlock: phase0.SignedBeaconBlock | altair.SignedBeaconBlock |
+                 merge.SignedBeaconBlock): ValidationRes =
   let
     wallTime = self.getCurrentBeaconTime()
     (afterGenesis, wallSlot) = wallTime.toSlot()
diff --git a/beacon_chain/gossip_processing/gossip_validation.nim b/beacon_chain/gossip_processing/gossip_validation.nim
index 6e5cf5650..483fa37a4 100644
--- a/beacon_chain/gossip_processing/gossip_validation.nim
+++ b/beacon_chain/gossip_processing/gossip_validation.nim
@@ -12,7 +12,7 @@ import
   chronicles, chronos, metrics,
   stew/results,
   # Internals
-  ../spec/datatypes/[phase0, altair],
+  ../spec/datatypes/[phase0, altair, merge],
   ../spec/[
     beaconstate, state_transition_block, forks, helpers, network, signatures],
   ../consensus_object_pools/[
@@ -141,10 +141,9 @@ func check_attestation_subnet(
     epochRef: EpochRef, attestation: Attestation,
     subnet_id: SubnetId): Result[void, ValidationError] =
   let
-    expectedSubnet =
-      compute_subnet_for_attestation(
-        get_committee_count_per_slot(epochRef),
-        attestation.data.slot, attestation.data.index.CommitteeIndex)
+    expectedSubnet = compute_subnet_for_attestation(
+      get_committee_count_per_slot(epochRef),
+      attestation.data.slot, attestation.data.index.CommitteeIndex)
 
   if expectedSubnet != subnet_id:
     return errReject("Attestation not on the correct subnet")
@@ -171,10 +170,59 @@ template checkedReject(error: ValidationError): untyped =
     raiseAssert $error[1]
   err(error)
 
+template validateBeaconBlockMerge(
+       signed_beacon_block: phase0.SignedBeaconBlock |
+                            altair.SignedBeaconBlock): untyped =
+  discard
+
+# https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/merge/p2p-interface.md#beacon_block
+template validateBeaconBlockMerge(
+       signed_beacon_block: merge.SignedBeaconBlock): untyped =
+  # If the execution is enabled for the block -- i.e.
+  # is_execution_enabled(state, block.body) then validate the following:
+  let executionEnabled =
+    if signed_beacon_block.message.body.execution_payload !=
+        default(ExecutionPayload):
+      true
+    elif dag.getEpochRef(parent_ref, parent_ref.slot.epoch).merge_transition_complete:
+      # Should usually be inexpensive, but could require cache refilling
+      true
+    else:
+      # Somewhat more expensive fallback, with database I/O, but should be
+      # mostly relevant around merge transition epochs. It's possible that
+      # the previous block is phase 0 or Altair, if this is the transition
+      # block itself.
+      let blockData = dag.get(parent_ref)
+      case blockData.data.kind:
+      of BeaconBlockFork.Phase0:
+        false
+      of BeaconBlockFork.Altair:
+        false
+      of BeaconBlockFork.Merge:
+        # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/merge/beacon-chain.md#process_execution_payload
+        # shows how this gets folded into the state each block; checking this
+        # is equivalent, without ever requiring state replay or any similarly
+        # expensive computation.
+        blockData.data.mergeData.message.body.execution_payload !=
+          default(ExecutionPayload)
+
+  if executionEnabled:
+    # [REJECT] The block's execution payload timestamp is correct with respect
+    # to the slot -- i.e. execution_payload.timestamp ==
+    # compute_timestamp_at_slot(state, block.slot).
+    let timestampAtSlot =
+      withState(dag.headState.data):
+        compute_timestamp_at_slot(state.data, signed_beacon_block.message.slot)
+    if not (signed_beacon_block.message.body.execution_payload.timestamp ==
+        timestampAtSlot):
+      return errReject("BeaconBlock: Mismatched execution payload timestamp")
+
 # https://github.com/ethereum/consensus-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#beacon_block
+# https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/merge/p2p-interface.md#beacon_block
 proc validateBeaconBlock*(
     dag: ChainDAGRef, quarantine: ref Quarantine,
-    signed_beacon_block: phase0.SignedBeaconBlock | altair.SignedBeaconBlock,
+    signed_beacon_block: phase0.SignedBeaconBlock | altair.SignedBeaconBlock |
+                         merge.SignedBeaconBlock,
     wallTime: BeaconTime, flags: UpdateFlags): Result[void, ValidationError] =
   # In general, checks are ordered from cheap to expensive. Especially, crypto
   # verification could be quite a bit more expensive than the rest. This is an
@@ -296,6 +344,8 @@ proc validateBeaconBlock*(
       signed_beacon_block.signature):
     return errReject("Invalid proposer signature")
 
+  validateBeaconBlockMerge(signed_beacon_block)
+
   ok()
 
 # https://github.com/ethereum/consensus-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#beacon_attestation_subnet_id
diff --git a/beacon_chain/nimbus_beacon_node.nim b/beacon_chain/nimbus_beacon_node.nim
index 0487d312f..bffe4e105 100644
--- a/beacon_chain/nimbus_beacon_node.nim
+++ b/beacon_chain/nimbus_beacon_node.nim
@@ -1047,6 +1047,11 @@ proc installMessageValidators(node: BeaconNode) =
     proc (signedBlock: altair.SignedBeaconBlock): ValidationResult =
       toValidationResult(node.processor[].blockValidator(signedBlock)))
 
+  node.network.addValidator(
+    getBeaconBlocksTopic(node.dag.forkDigests.merge),
+    proc (signedBlock: merge.SignedBeaconBlock): ValidationResult =
+      toValidationResult(node.processor[].blockValidator(signedBlock)))
+
   template installSyncCommitteeeValidators(digest: auto) =
     for committeeIdx in allSyncSubcommittees():
       closureScope: