fix: build message digest with solidity abi encoding

internal/service/api/handlers/get_signed_state.go

@@ -5,6 +5,7 @@ import (
 	"math/big"
 	"net/http"
 
+	"github.com/ethereum/go-ethereum/accounts/abi"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/rarimo/proof-verification-relayer/internal/data"
 	"github.com/rarimo/proof-verification-relayer/internal/service/api/requests"
@@ -66,30 +67,58 @@ func GetSignedState(w http.ResponseWriter, r *http.Request) {
 }
 
 func signState(state data.State, r *http.Request) ([]byte, error) {
+	digest, err := buildMessageDigest(state, r)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to build message digest")
+	}
+
+	signature, err := crypto.Sign(digest, Config(r).NetworkConfig().PrivateKey)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to sign state")
+	}
+
+	return signature, nil
+}
+
+func buildMessageDigest(state data.State, r *http.Request) ([]byte, error) {
 	rootBytes, err := hex.DecodeString(state.Root)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to decode signature digest", logan.F{"root": state.Root})
 	}
 
+	uint256Ty, _ := abi.NewType("uint256", "uint256", nil)
+	bytes32Ty, _ := abi.NewType("bytes32", "bytes32", nil)
+	addressTy, _ := abi.NewType("address", "address", nil)
+	stringTy, _ := abi.NewType("string", "string", nil)
+
 	//keccak256(abi.encodePacked(
 	//	REGISTRATION_ROOT_PREFIX,
 	//	sourceSMT,
 	//	address(this),
 	//	newRoot_,
 	//	transitionTimestamp_
 	//));
-	digest := crypto.Keccak256(
-		[]byte(Config(r).Replicator().RootPrefix),
-		Config(r).Replicator().SourceSMT.Bytes(),
-		Config(r).Replicator().Address.Bytes(),
-		rootBytes,
-		new(big.Int).SetUint64(state.Timestamp).Bytes(),
-	)
 
-	signature, err := crypto.Sign(digest, Config(r).NetworkConfig().PrivateKey)
+	args := abi.Arguments{
+		{Type: stringTy},
+		{Type: addressTy},
+		{Type: addressTy},
+		{Type: bytes32Ty},
+		{Type: uint256Ty},
+	}
+
+	rootBytes32 := [32]byte{}
+	copy(rootBytes32[:], rootBytes[:32])
+	packed, err := args.Pack(
+		Config(r).Replicator().RootPrefix,
+		Config(r).Replicator().SourceSMT,
+		Config(r).Replicator().Address,
+		rootBytes32,
+		new(big.Int).SetUint64(state.Timestamp),
+	)
 	if err != nil {
-		return nil, errors.Wrap(err, "failed to sign state")
+		return nil, errors.Wrap(err, "failed to pack signature msg digest")
 	}
 
-	return signature, nil
+	return crypto.Keccak256(packed), nil
 }