Validate header timestamp in engine_forkchoiceUpdated (#2278)

* Validate header timestamp in engine_forkchoiceUpdated

* Fix fcUV3 error message

nimbus/beacon/api_handler/api_forkchoice.nim

@@ -51,6 +51,24 @@ template validateVersion(attr, com, apiVersion) =
  raise invalidParams("if timestamp is earlier than Shanghai," &
  " payloadAttributes must be PayloadAttributesV1")
 
+template validateHeaderTimestamp(header, com, apiVersion) =
+ # See fCUV3 specification No.2 bullet iii
+ # https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/cancun.md#specification-1
+ if com.isCancunOrLater(header.timestamp):
+ if apiVersion != Version.V3:
+ raise invalidAttr("forkChoiceUpdated" & $apiVersion &
+ " doesn't support head block with timestamp >= Cancun")
+ # See fCUV2 specification No.2 bullet 1
+ # https://github.com/ethereum/execution-apis/blob/v1.0.0-beta.4/src/engine/shanghai.md#specification-1
+ elif com.isShanghaiOrLater(header.timestamp):
+ if apiVersion != Version.V2:
+ raise invalidAttr("forkChoiceUpdated" & $apiVersion &
+ " doesn't support head block with Shanghai timestamp")
+ else:
+ if apiVersion != Version.V1:
+ raise invalidAttr("forkChoiceUpdated" & $apiVersion &
+ " doesn't support head block with timestamp earlier than Shanghai")
+
 proc forkchoiceUpdated*(ben: BeaconEngineRef,
  apiVersion: Version,
  update: ForkchoiceStateV1,
@@ -100,6 +118,8 @@ proc forkchoiceUpdated*(ben: BeaconEngineRef,
  com.syncReqNewHead(header)
  return simpleFCU(PayloadExecutionStatus.syncing)
 
+ validateHeaderTimestamp(header, com, apiVersion)
+
  # Block is known locally, just sanity check that the beacon client does not
  # attempt to push us back to before the merge.
  #