core, eth/downloader: make body validation more strict (#26704)

eth/downloader/queue.go

@@ -781,14 +781,17 @@ func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, txListH
 			return errInvalidBody
 		}
 		if header.WithdrawalsHash == nil {
-			// discard any withdrawals if we don't have a withdrawal hash set
-			withdrawalLists[index] = nil
-		} else if *header.WithdrawalsHash == types.EmptyRootHash && withdrawalLists[index] == nil {
-			// if the withdrawal hash is the emptyRootHash,
-			// we expect withdrawals to be [] instead of nil
-			withdrawalLists[index] = make([]*types.Withdrawal, 0)
-		} else if withdrawalListHashes[index] != *header.WithdrawalsHash {
-			return errInvalidBody
+			// nil hash means there withdrawals should not be present in body
+			if withdrawalLists[index] != nil {
+				return errInvalidBody
+			}
+		} else { // non-nil hash: body must have withdrawals
+			if withdrawalLists[index] == nil {
+				return errInvalidBody
+			}
+			if withdrawalListHashes[index] != *header.WithdrawalsHash {
+				return errInvalidBody
+			}
 		}
 		return nil
 	}