接口鉴权之sign签名校验与JWT验证

需求描述：

　　项目里的几个Webapi接口需要进行鉴权，同接口可被小程序或网页调用，小程序里没有用户登录的概念，网页里有用户登录的概念，对于调用方来源是小程序的情况下进行放权，其他情况下需要有身份验证。也就是说给所有小程序请求进行放行，给网页请求进行jwt身份验证。由于我的小程序没有用户登录的功能，所以要针对小程序和网页设计出两套完全不同的鉴权方式。

　　

鉴权流程设计：

　　查阅相关资料，最终决定的鉴权方式：

• 小程序采用sign签名检验
• 网页采用目前比较流行的JWT的token校验

通过AOP的思想使用.Net的Attribute进行拦截请求

 代码实现

　　主要是服务端写一个Attribute，判断是小程序还是网页，然后采用不同的两种不同的鉴权方式。

　　

• Attribute代码：

    public class WxAllowFilterAttribute : BaseActionFilter
    {
        private static readonly int _errorCode = 401;
        public override void OnActionExecuting(HttpActionContext filterContext)
        {
            var iswx = filterContext.iswx();//判断是否是小程序发来的请求
            if (iswx)
            {
　　　　　　　　　　//小程序的签名校验
                if (!filterContext.checkwx()) {
                    filterContext.Response = Error("小程序签名验证失败", _errorCode);
                };
            }
            else
            {
　　　　　　　　　　//JWT的token校验
                string token = filterContext.GetToken();
                if (string.IsNullOrEmpty(token))
                {
                    filterContext.Response = Error("缺少token", _errorCode);
                    return;
                }
                if (!JWTHelper.CheckToken(token, JWTHelper.JWTSecret))
                {
                    filterContext.Response = Error("token校验失败!", _errorCode);
                    return;
                }

                var payload = JWTHelper.GetPayload<JWTPayload>(token);
                if (payload.Expire < DateTime.Now)
                {
                    filterContext.Response = Error("token过期!", _errorCode);
                    return;
                }
                base.OnActionExecuting(filterContext);
            }
        }
    }

• 扩展类

public static class HttpRequest
    {
        public static readonly string wx_secret = ConfigurationManager.AppSettings["wx_secret"];
        /// <summary>
        /// 获取Token
        /// </summary>
        /// <param name="req">请求</param>
        /// <returns></returns>
        public static string GetToken(this HttpActionContext req)
        {
            string tokenHeader = req.Request.Headers.Authorization == null ? "" : req.Request.Headers.Authorization.Parameter;
            if (string.IsNullOrEmpty(tokenHeader))
                return null;
            string pattern = "^Bearer (.*?)$";
            if (!Regex.IsMatch(tokenHeader, pattern))
                throw new Exception("token格式不对!格式为:Bearer {token}");

            string token = Regex.Match(tokenHeader, pattern).Groups[1].ToString();
            if (string.IsNullOrEmpty(token))
                throw new Exception("token不能为空!");
            return token;
        }
        /// <summary>
        /// 判断是否微信
        /// </summary>
        /// <param name="req"></param>
        /// <returns></returns>
        public static bool iswx(this HttpActionContext req)
        {
            var queryList = req.Request.RequestUri.Query.Split('&').ToList<string>();
            Dictionary<String, String> pList = new Dictionary<String, String>();
            if (queryList.Count < 2)
            {
                return false;
            }
            else
            {
                queryList.ForEach(x =>
                {
                    var a = x.Split('=');
                    if (a.Count() >= 2)
                    {
                        pList.Add(a[0], a[1]);
                    }
                });
                var iswx = pList.Any(x => x.Key == "app_key" && x.Value == "wx");//判断是否有微信标识的字段
                return iswx;
            }


        }
        /// <summary>
        /// 检验微信sign是否合法
        /// </summary>
        /// <param name="req"></param>
        /// <returns></returns>
        public static bool checkwx(this HttpActionContext req)
        {
            var queryList = req.Request.RequestUri.Query.Split('&').ToList<string>();
            Dictionary<String, String> pList = new Dictionary<String, String>();
            queryList.ForEach(x =>
            {
                var a = x.Split('=');
                if (a.Count() >= 2)
                {
                    pList.Add(a[0], a[1]);
                }
            });
            var app_key = pList["app_key"];
            var app_secret = wx_secret;
            var timetamp = pList["timestamp"];
            var sign = pList["sign"];
            if (!string.IsNullOrEmpty(timetamp)) { 
                var tamp=Convert.ToInt64(timetamp);
                var nowtamp = ToTimestamp(DateTime.Now);
                var a = nowtamp-tamp;
                if (a >= 15) {
                    return false;
                }
            }
            StringBuilder sb = new StringBuilder();
            sb.Append(app_key);
            sb.Append(app_secret);
            sb.Append(timetamp);
            var newsign = GetMD5(sb.ToString());
            return newsign == sign;

        }
        public static string GetMD5(string sDataIn)
        {
            MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider();
            byte[] bytes = Encoding.UTF8.GetBytes(sDataIn);
            byte[] buffer2 = provider.ComputeHash(bytes);
            provider.Clear();
            string str = "";
            for (int i = 0; i < buffer2.Length; i++)
            {
                str = str + buffer2[i].ToString("X").PadLeft(2, '0');
            }
            return str.ToLower();
        }

        public static long ToTimestamp(this DateTime target)
        {
            return (target.ToUniversalTime().Ticks - 621355968000000000) / 10000000;
        }
    }

• Filter基类

public class BaseActionFilter : ActionFilterAttribute
    {
        //public virtual void OnActionExecuting(HttpActionContext filterContext)
        //{
        //}
        //public virtual void OnActionExecuted(HttpActionContext filterContext)
        //{
        //}
        /// <summary>
        /// 返回JSON
        /// </summary>
        /// <param name="json">json字符串</param>
        /// <returns></returns>
        public HttpResponseMessage JsonContent(string json)
        {
            var content = new StringContent(json, Encoding.UTF8, "application/json");
            return new HttpResponseMessage { Content = content, StatusCode = HttpStatusCode.OK };
        }
        public HttpResponseMessage IsSuccess()
        {
            AjaxResult res = new AjaxResult
            {
                IsSuccess = true,
                Msg = "请求成功！"
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }

        /// <summary>
        /// 返回成功
        /// </summary>
        /// <param name="msg">消息</param>
        /// <returns></returns>
        public HttpResponseMessage IsSuccess(string msg)
        {
            AjaxResult res = new AjaxResult
            {
                IsSuccess = true,
                Msg = msg
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }

        /// <summary>
        /// 返回成功
        /// </summary>
        /// <param name="data">返回的数据</param>
        /// <returns></returns>
        public HttpResponseMessage IsSuccess<T>(T data)
        {
            AjaxResult<T> res = new AjaxResult<T>
            {
                IsSuccess = true,
                Msg = "请求成功！",
                Data = data
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }

        /// <summary>
        /// 返回错误
        /// </summary>
        /// <returns></returns>
        public HttpResponseMessage Error()
        {
            AjaxResult res = new AjaxResult
            {
                IsSuccess = false,
                Msg = "请求失败！"
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }

        /// <summary>
        /// 返回错误
        /// </summary>
        /// <param name="msg">错误提示</param>
        /// <returns></returns>
        public HttpResponseMessage Error(string msg)
        {
            AjaxResult res = new AjaxResult
            {
                IsSuccess = false,
                Msg = msg,
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }

        /// <summary>
        /// 返回错误
        /// </summary>
        /// <param name="msg">错误提示</param>
        /// <param name="errorCode">错误代码</param>
        /// <returns></returns>
        public HttpResponseMessage Error(string msg, int errorCode)
        {
            AjaxResult res = new AjaxResult
            {
                IsSuccess = false,
                Msg = msg,
                StatusCode = errorCode
            };

            return JsonContent(JsonHelper.SerializeObject(res));
        }
    }

• JWT扩展类

public class JWTHelper
    {
        private static readonly string _headerBase64Url = "{"alg":"HS256","typ":"JWT"}".Base64UrlEncode();
        public static readonly string JWTSecret = ConfigurationManager.AppSettings["JWTSecret"];
        /// <summary>
        /// 生成Token
        /// </summary>
        /// <param name="payloadJsonStr">数据JSON字符串</param>
        /// <param name="secret">密钥</param>
        /// <returns></returns>
        public static string GetToken(string payloadJsonStr, string secret)
        {
            string payloadBase64Url = payloadJsonStr.Base64UrlEncode();
            StringBuilder sb = new StringBuilder();
            StringBuilder sb1 = new StringBuilder();
            sb.AppendFormat("{0}", _headerBase64Url);
            sb.Append(".");
            sb.AppendFormat("{0}", payloadBase64Url);
            sb1 = sb;
            string sign = sb.ToString().ToHMACSHA256String(secret);

            string token = sb1.AppendFormat(".{0}", sign).ToString();

            return token;
        }


        /// <summary>
        /// 获取Token中的数据
        /// </summary>
        /// <typeparam name="T">泛型</typeparam>
        /// <param name="token">token</param>
        /// <returns></returns>
        public static T GetPayload<T>(string token)
        {
            if (string.IsNullOrEmpty(token))
            {
                return default(T);
            }
            return token.Split('.')[1].Base64UrlDecode().ToObject<T>();
        }

        /// <summary>
        /// 校验Token
        /// </summary>
        /// <param name="token">token</param>
        /// <param name="secret">密钥</param>
        /// <returns></returns>
        public static bool CheckToken(string token, string secret)
        {
            var items = token.Split('.');
            var oldSign = items[2];
            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("{0}", items[0]);
            sb.AppendFormat(".{0}", items[1]);
            string newSign = sb.ToString().ToHMACSHA256String(secret);
            return oldSign == newSign;
        }
    }

检验用户名密码是否正确的业务接口代码这里不贴了..

网页客户端的代码还没写完，主要思路就是判断缓存里是否有token，没有就去把用户名密码去调用服务端的登录接口拿到token后存到缓存里，之后的所有请求都在头部带上这个token。

小程序客户端代码 :

在app.js中定义一个公共的promise请求方法，并带上请求的参数(app_key,时间戳,md5加密后的sign等)，这里要注意区分get和post请求的区别，get是放在url后的,post是放在body里的，要对传参的格式要稍加处理

  request(params) {
    reqTime++;
    //加载弹框
    wx.showLoading({
      title: '加载中...',
      mask: true
    });
    //返回
    return new Promise((resolve, reject) => {
      var data = {
        app_key: this.globalData.app_key,
        timestamp: Math.round(new Date() / 1000),
        sign: ''
      }
      data.sign = utilMd5.hexMD5(`${this.globalData.app_key}${this.globalData.app_secret}${data.timestamp}`)
      if (params.method.toUpperCase() == 'POST') {
        if (!params.url.includes('?')) {
          params.url += '?'
        }
        var url = `&app_key=${this.globalData.app_key}&timestamp=${data.timestamp}&sign=${data.sign}`
        params = {
          ...params,
          url: params.url + url
        }
        data = params.data
      } else {
        data = {
          ...params.data,
          ...data
        }
      }
      params = {
        ...params,
        data: {
          ...data
        }
      }
      wx.request({
        //解构params获取请求参数
        ...params,
        success: (result) => {
          resolve(result);
        },
        fail: (err) => {
          reject(err);
        },
        complete: () => {
          reqTime--;
          //停止加载
          if (!reqTime)
            wx.hideLoading();
        }
      });
    });
  }

这边说明下，我的app_key和app_secret都是写在app.js里的公共变量中的，app_key在url里是暴露的，但是app_secret是绝不能被暴露的。光知道app_key是无法生成正确的sign的，必须app_key,app_secret和timestap三者的加密才能生成正确的sign。我把app_secret写在app.js中可能不是安全的做法，但是通过请求服务器去获取app.secret又要面临网络请求的安全问题，最多对字符串进行加密解密，但也不能说绝对安全了。app_secret怎么处理最安全我目前也没想到很好的办法。。

好了，以上就是小程序的鉴权方法，小程序客户端在请求时只需要调用这个公共方法就行。

鉴权测试结果

• 给控制器或者方法前面加上鉴权的特性[WxAllowFilter] 

• PostMan直接调用不带任何sign等参数

• 伪造小程序参数签名验证失败或者时间戳超过10秒

• 小程序内调用