ft: add check for invalid nonceIn

internal/usecase/path_sign_txn.go

@@ -220,13 +220,18 @@ func (b *Backend) validateAndGetTx(data *framework.FieldData) (*RequestFieldsTra
 		b.Logger().Error("Invalid gas limit", "gas", data.Get("gas").(string))
 		return nil, fmt.Errorf("invalid gas limit")
 	}
+
 	gasLimit := gasLimitIn.Uint64()
 	gasPrice := validNumber(data.Get("gasPrice").(string))
 	gasFeeCapStr := data.Get("gasFeeCap").(string) //nolint
 	gasTipCapStr := data.Get("gasTipCap").(string) //nolint
 	nonceIn := validNumber(data.Get("nonce").(string))
-	nonce := nonceIn.Uint64()
+	if nonceIn == nil {
+		b.Logger().Error("Invalid nonce", "nonce", data.Get("nonce").(string))
+		return nil, fmt.Errorf("invalid nonce")
+	}
 
+	nonce := nonceIn.Uint64()
 	var addressTo *common.Address
 	if rawAddressTo != "" {
 		addressToTemp := common.HexToAddress(rawAddressTo)

internal/usecase/path_sign_txn_test.go

@@ -173,4 +173,22 @@ func TestBackend_signTx(t *testing.T) {
 
 	sender, _ = types.Sender(types.LatestSignerForChainID(big.NewInt(1)), tx)
 	assert.Equal(t, address.Hex(), sender.Hex())
+
+	// sign TX with invalid nonce
+	dataToSign = "60fe47b10000000000000000000000000000000000000000000000000000000000000014"
+	req = logical.TestRequest(t, logical.CreateOperation, "key-managers/"+keeperSvc+"/txn/sign")
+	req.Storage = storage
+	data = map[string]interface{}{
+		"data":     dataToSign,
+		"address":  "0xBffc2f3Df75367B0f246aF6Ae42AFf59A33f2704",
+		"to":       "0xf809410b0d6f047c603deb311979cd413e025a84",
+		"gas":      2000,
+		"nonce":    "0x",
+		"gasPrice": 0,
+		"chainId":  "12345",
+	}
+	req.Data = data
+	_, err = b.HandleRequest(context.Background(), req)
+	assert.ErrorContains(t, err, "invalid nonce")
+
 }