feat(utils): add HashedL2ToL1Msg method

utils/bridge.go

@@ -1,10 +1,12 @@
 package utils
 
 import (
+	"encoding/binary"
 	"fmt"
 	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/zksync-sdk/zksync2-go/contracts/erc20"
 	"github.com/zksync-sdk/zksync2-go/contracts/l2bridge"
 	"github.com/zksync-sdk/zksync2-go/types"
@@ -91,3 +93,17 @@ func Erc20BridgeCalldata(l1TokenAddress, l1Sender, l2Receiver common.Address, am
 	}
 	return l2BridgeAbi.Pack("finalizeDeposit", l1Sender, l2Receiver, l1TokenAddress, amount, bridgeData)
 }
+
+// HashedL2ToL1Msg returns a `keccak` encoded message with a given sender address and
+// block number from the L1 messenger contract.
+func HashedL2ToL1Msg(sender common.Address, msg []byte, txNumberInBlock uint16) common.Hash {
+	txNumberInBlockBytes := make([]byte, 2)
+	binary.BigEndian.PutUint16(txNumberInBlockBytes, txNumberInBlock)
+
+	encodedMsg := append([]byte{0, 1}, txNumberInBlockBytes...)
+	encodedMsg = append(encodedMsg, L1MessengerAddress.Bytes()...)
+	encodedMsg = append(encodedMsg, common.LeftPadBytes(sender.Bytes(), 32)...)
+	encodedMsg = append(encodedMsg, crypto.Keccak256(msg)...)
+
+	return crypto.Keccak256Hash(encodedMsg)
+}

utils/bridge_test.go

@@ -0,0 +1,15 @@
+package utils
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestHashedL2ToL1Msg(t *testing.T) {
+	sender := common.HexToAddress("0x36615Cf349d7F6344891B1e7CA7C72883F5dc049")
+	withdrawETHMessage := common.FromHex("0x6c0960f936615cf349d7f6344891b1e7ca7c72883f5dc04900000000000000000000000000000000000000000000000000000001a13b8600")
+	withdrawETHMessageHash := common.HexToHash("0x521bd25904766c83fe868d6a29cbffa011afd8a1754f6c9a52b053b693e42f18")
+	expected := HashedL2ToL1Msg(sender, withdrawETHMessage, 0)
+	assert.Equal(t, expected, withdrawETHMessageHash, "Hashes should be the same")
+}