fix(op-node): Include chainID in p2p signing hash

op-node/p2p/signer.go

@@ -30,7 +30,7 @@ func SigningHash(domain [32]byte, chainID *big.Int, payloadBytes []byte) (common
 	}
 	chainID.FillBytes(msgInput[32:64])
 	// payload_hash: third 32 bytes, hash of encoded payload
-	copy(msgInput[32:], crypto.Keccak256(payloadBytes))
+	copy(msgInput[64:], crypto.Keccak256(payloadBytes))
 
 	return crypto.Keccak256Hash(msgInput[:]), nil
 }

op-node/p2p/signer_test.go

+package p2p
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum-optimism/optimism/op-node/rollup"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSigningHash_DifferentDomain(t *testing.T) {
+	cfg := &rollup.Config{
+		L2ChainID: big.NewInt(100),
+	}
+
+	payloadBytes := []byte("arbitraryData")
+	hash, err := SigningHash(SigningDomainBlocksV1, cfg.L2ChainID, payloadBytes)
+	require.NoError(t, err, "creating first signing hash")
+
+	hash2, err := SigningHash([32]byte{3}, cfg.L2ChainID, payloadBytes)
+	require.NoError(t, err, "creating second signing hash")
+
+	require.NotEqual(t, hash, hash2, "signing hash should be different when domain is different")
+}
+
+func TestSigningHash_DifferentChainID(t *testing.T) {
+	cfg1 := &rollup.Config{
+		L2ChainID: big.NewInt(100),
+	}
+	cfg2 := &rollup.Config{
+		L2ChainID: big.NewInt(101),
+	}
+
+	payloadBytes := []byte("arbitraryData")
+	hash, err := SigningHash(SigningDomainBlocksV1, cfg1.L2ChainID, payloadBytes)
+	require.NoError(t, err, "creating first signing hash")
+
+	hash2, err := SigningHash(SigningDomainBlocksV1, cfg2.L2ChainID, payloadBytes)
+	require.NoError(t, err, "creating second signing hash")
+
+	require.NotEqual(t, hash, hash2, "signing hash should be different when chain ID is different")
+}
+
+func TestSigningHash_DifferentMessage(t *testing.T) {
+	cfg := &rollup.Config{
+		L2ChainID: big.NewInt(100),
+	}
+
+	hash, err := SigningHash(SigningDomainBlocksV1, cfg.L2ChainID, []byte("msg1"))
+	require.NoError(t, err, "creating first signing hash")
+
+	hash2, err := SigningHash(SigningDomainBlocksV1, cfg.L2ChainID, []byte("msg2"))
+	require.NoError(t, err, "creating second signing hash")
+
+	require.NotEqual(t, hash, hash2, "signing hash should be different when message is different")
+}
+
+func TestSigningHash_LimitChainID(t *testing.T) {
+	// ChainID with bitlen 257
+	chainID := big.NewInt(1)
+	chainID = chainID.SetBit(chainID, 256, 1)
+	cfg := &rollup.Config{
+		L2ChainID: chainID,
+	}
+	_, err := SigningHash(SigningDomainBlocksV1, cfg.L2ChainID, []byte("arbitraryData"))
+	require.ErrorContains(t, err, "chain_id is too large")
+}