From 6f7c4fffe72cd61c97e13647f1fe845c5d7c80e1 Mon Sep 17 00:00:00 2001
From: Etan Kissling <etan@nimbus.team>
Date: Fri, 16 Aug 2024 22:52:35 +0200
Subject: [PATCH] Synchronously check all `transactions` to have non-zero
 length (#6491)

Reject blocks with zero length transactions early when no EL connected.

- https://github.com/ethereum/consensus-specs/pull/3885
---
 .../gossip_processing/block_processor.nim     | 49 ++++++++++---------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/beacon_chain/gossip_processing/block_processor.nim b/beacon_chain/gossip_processing/block_processor.nim
index f6e845b66..262011f18 100644
--- a/beacon_chain/gossip_processing/block_processor.nim
+++ b/beacon_chain/gossip_processing/block_processor.nim
@@ -13,7 +13,7 @@ import
   ../sszdump
 
 from std/deques import Deque, addLast, contains, initDeque, items, len, shrink
-from std/sequtils import mapIt
+from std/sequtils import anyIt, mapIt
 from ../consensus_object_pools/consensus_manager import
   ConsensusManager, checkNextProposer, optimisticExecutionBlockHash,
   runProposalForkchoiceUpdated, shouldSyncOptimistically, updateHead,
@@ -541,31 +541,32 @@ proc storeBlock(
 
   if NewPayloadStatus.noResponse == payloadStatus:
     # When the execution layer is not available to verify the payload, we do the
-    # required check on the CL side instead and proceed as if the EL was syncing
-
-    # TODO run https://github.com/ethereum/consensus-specs/blob/v1.3.0/specs/deneb/beacon-chain.md#blob-kzg-commitments
-    # https://github.com/ethereum/execution-apis/blob/main/src/engine/experimental/blob-extension.md#specification
-    # "This validation MUST be instantly run in all cases even during active
-    # sync process."
-    #
-    # Client software MUST validate `blockHash` value as being equivalent to
-    # `Keccak256(RLP(ExecutionBlockHeader))`
-    # https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.3/src/engine/paris.md#specification
-    #
-    # This should simulate an unsynced EL, which still must perform these
-    # checks. This means it must be able to do so without context, beyond
-    # whatever data the block itself contains.
+    # required checks on the CL instead and proceed as if the EL was syncing
+    # https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.4/specs/bellatrix/beacon-chain.md#verify_and_notify_new_payload
+    # https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.4/specs/deneb/beacon-chain.md#modified-verify_and_notify_new_payload
     when typeof(signedBlock).kind >= ConsensusFork.Bellatrix:
-      template payload(): auto = signedBlock.message.body.execution_payload
-      if  signedBlock.message.is_execution_block and
-          payload.block_hash !=
+      if signedBlock.message.is_execution_block:
+        template payload(): auto = signedBlock.message.body.execution_payload
+
+        template returnWithError(msg: string): untyped =
+          debug msg, executionPayload = shortLog(payload)
+          self[].dumpInvalidBlock(signedBlock)
+          doAssert strictVerification notin dag.updateFlags
+          self.consensusManager.quarantine[].addUnviable(signedBlock.root)
+          return err((VerifierError.Invalid, ProcessingStatus.completed))
+
+        if payload.transactions.anyIt(it.len == 0):
+          returnWithError "Execution block contains zero length transactions"
+
+        if payload.block_hash !=
             signedBlock.message.compute_execution_block_hash():
-        debug "Execution block hash validation failed",
-          execution_payload = shortLog(payload)
-        self[].dumpInvalidBlock(signedBlock)
-        doAssert strictVerification notin dag.updateFlags
-        self.consensusManager.quarantine[].addUnviable(signedBlock.root)
-        return err((VerifierError.Invalid, ProcessingStatus.completed))
+          returnWithError "Execution block hash validation failed"
+
+        # [New in Deneb:EIP4844]
+        # TODO run https://github.com/ethereum/consensus-specs/blob/v1.3.0/specs/deneb/beacon-chain.md#blob-kzg-commitments
+        # https://github.com/ethereum/execution-apis/blob/main/src/engine/experimental/blob-extension.md#specification
+        # "This validation MUST be instantly run in all cases even during active
+        # sync process."
 
   let newPayloadTick = Moment.now()