validate sign tx request's body

Closes: #3176

client/lcd/lcd_test.go

@@ -17,6 +17,7 @@ import (
 
 	client "github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/client/tx"
+	"github.com/cosmos/cosmos-sdk/client/utils"
 	"github.com/cosmos/cosmos-sdk/cmd/gaia/app"
 
 	"github.com/cosmos/cosmos-sdk/crypto/keys/mintkey"
@@ -259,12 +260,10 @@ func TestCoinSendGenerateSignAndBroadcast(t *testing.T) {
 	var signedMsg auth.StdTx
 
 	payload := authrest.SignBody{
-		Tx:               msg,
-		LocalAccountName: name1,
-		Password:         pw,
-		ChainID:          viper.GetString(client.FlagChainID),
-		AccountNumber:    accnum,
-		Sequence:         sequence,
+		Tx: msg,
+		BaseReq: utils.NewBaseReq(
+			name1, pw, "", viper.GetString(client.FlagChainID), "", "", accnum, sequence, nil, false, false,
+		),
 	}
 	json, err := cdc.MarshalJSON(payload)
 	require.Nil(t, err)

client/lcd/test_helpers.go

@@ -645,12 +645,10 @@ func getAccount(t *testing.T, port string, addr sdk.AccAddress) auth.Account {
 func doSign(t *testing.T, port, name, password, chainID string, accnum, sequence uint64, msg auth.StdTx) auth.StdTx {
 	var signedMsg auth.StdTx
 	payload := authrest.SignBody{
-		Tx:               msg,
-		LocalAccountName: name,
-		Password:         password,
-		ChainID:          chainID,
-		AccountNumber:    accnum,
-		Sequence:         sequence,
+		Tx: msg,
+		BaseReq: utils.NewBaseReq(
+			name, password, "", chainID, "", "", accnum, sequence, nil, false, false,
+		),
 	}
 	json, err := cdc.MarshalJSON(payload)
 	require.Nil(t, err)

client/utils/rest.go

@@ -189,7 +189,7 @@ func ReadRESTReq(w http.ResponseWriter, r *http.Request, cdc *codec.Codec, req i
 
 	err = cdc.UnmarshalJSON(body, req)
 	if err != nil {
-		WriteErrorResponse(w, http.StatusBadRequest, err.Error())
+		WriteErrorResponse(w, http.StatusBadRequest, fmt.Sprintf("failed to decode JSON payload: %s", err))
 		return err
 	}