From 3eef848d7f7b01cad9cf27e3ffca456686d03704 Mon Sep 17 00:00:00 2001
From: tfrench-uber <tfrench@uber.com>
Date: Wed, 29 Dec 2021 16:44:44 -0500
Subject: [PATCH] validate input and output before unmarshal

---
 unmarshal.go      | 10 ++++++-
 unmarshal_test.go | 75 +++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 82 insertions(+), 3 deletions(-)

diff --git a/unmarshal.go b/unmarshal.go
index e66090d..957347c 100644
--- a/unmarshal.go
+++ b/unmarshal.go
@@ -3,6 +3,7 @@ package njson
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"reflect"
 
 	"github.com/tidwall/gjson"
@@ -14,6 +15,9 @@ var jsonNumberType = reflect.TypeOf(json.Number(""))
 
 // Unmarshal used to unmarshal nested json using "njson" tag
 func Unmarshal(data []byte, v interface{}) (err error) {
+	if !gjson.ValidBytes(data) {
+		return fmt.Errorf("invalid json: %v", string(data))
+	}
 
 	// catch code panic and return error message
 	defer func() {
@@ -29,7 +33,11 @@ func Unmarshal(data []byte, v interface{}) (err error) {
 		}
 	}()
 
-	elem := reflect.ValueOf(v).Elem()
+	rv := reflect.ValueOf(v)
+	if rv.Kind() != reflect.Ptr || rv.IsNil() {
+		return fmt.Errorf("can't unmarshal to invalid type %v", reflect.TypeOf(v))
+	}
+	elem := rv.Elem()
 	typeOfT := elem.Type()
 	for i := 0; i < elem.NumField(); i++ {
 		field := elem.Field(i)
diff --git a/unmarshal_test.go b/unmarshal_test.go
index ea7a3d7..20b0d5a 100644
--- a/unmarshal_test.go
+++ b/unmarshal_test.go
@@ -8,6 +8,77 @@ import (
 	"github.com/google/go-cmp/cmp"
 )
 
+func TestUnmarshalInvalidJson(t *testing.T) {
+	json := `
+	BAD JSON %% @
+	##
+	}`
+
+	type Name struct {
+		First string `njson:"first"`
+		Last  string `njson:"last"`
+	}
+
+	type User struct {
+		Name    Name   `njson:"name"`
+		Age     int    `njson:"age"`
+		Friends []Name `njson:"friends"`
+	}
+
+	actual := User{}
+
+	if err := Unmarshal([]byte(json), &actual); err == nil {
+		t.Error("error should not be nil")
+	}
+}
+
+func TestUnmarshalError(t *testing.T) {
+	json := `
+	{
+        "name": {"first": "Mohamed", "last": "Shapan"},
+        "age": 26,
+        "friends": [
+            {"first": "Asma", "age": 26},
+            {"first": "Ahmed", "age": 25},
+            {"first": "Mahmoud", "age": 30}
+        ]
+	}`
+
+	if err := Unmarshal([]byte(json), nil); err == nil {
+		t.Error("error should not be nil")
+	}
+}
+
+func TestUnmarshalByValueError(t *testing.T) {
+	json := `
+	{
+        "name": {"first": "Mohamed", "last": "Shapan"},
+        "age": 26,
+        "friends": [
+            {"first": "Asma", "age": 26},
+            {"first": "Ahmed", "age": 25},
+            {"first": "Mahmoud", "age": 30}
+        ]
+	}`
+
+	type Name struct {
+		First string `njson:"first"`
+		Last  string `njson:"last"`
+	}
+
+	type User struct {
+		Name    Name   `njson:"name"`
+		Age     int    `njson:"age"`
+		Friends []Name `njson:"friends"`
+	}
+
+	actual := User{}
+
+	if err := Unmarshal([]byte(json), actual); err == nil {
+		t.Error("error should not be nil")
+	}
+}
+
 func TestUnmarshalSmall(t *testing.T) {
 	json := `
 	{
@@ -260,7 +331,7 @@ func TestUnmarshalSlices(t *testing.T) {
 			[
 				[
 					601, 602, 603
-				],
+				]
 			]
 
 		],
@@ -429,7 +500,7 @@ func TestUnmarshalComplex(t *testing.T) {
 		],
 		"time_1": "2021-01-11T23:56:51.141Z",
 		"time_2": "2021-01-11T23:56:51.141+01:00",
-		"time_3": "2021-01-11T23:56:51.141-01:00",
+		"time_3": "2021-01-11T23:56:51.141-01:00"
 	  }
 	`