JS code analysis in WeChat QR code login

In many places, there are applications such as QR code login, QR code payment, QR code account (the QR code stallion here, let alone fraud), QR code verification, multi-terminal There are more and more auxiliary authorization applications. Let’s first talk about what a QR code is. In fact, a QR code is a black and white code that stores binary data.Pictures, when a QR code is required to log in, the server will generate a temporary and unique QR code information and send it to the client with the QR code (picture) Write the form to the web page, and then you will see a unified four-square QR code. If done well, the QR code information should be time-sensitive. We will not consider these for the time being. Let’s take a simple WeChat login as an example. Let’s take a look,

First let’s talk about the entire authorization process:

In the client web page, https connections will be continuously sent to the server, and after very little data is transmitted here The connection is disconnected. Let’s take a look at the login1c709c.js file in the WeChat webpage:

(function($, _aoWin) {
_aoWin.QRLogin = {};
  _aoWin.LoginLog = "";
 var _sBaseHost = "",
    _oLoginQrCodeImg = document.getElementById("loginQrCode");
 if (document.domain == "qq.com") {
 _sBaseHost = "weixin.qq.com";
 } else if(location.hostname.match(/(wechat\.com)$/)){
 _sBaseHost = "wechat.com";
 }else{
    _sBaseHost = "wechatapp.com";
  }
 
 var show_tip = 1,
 _sCurUUId,
 _oResetTimeout,
    _aWebMMCallbacks = [],
    _oDetactWebMMInterval = setInterval(function(){
      if(_aoWin.WebMM){
        clearInterval(_oDetactWebMMInterval);
        var callback;
        while(callback = _aWebMMCallbacks.shift()){
          if(typeof(callback) != "function") continue;
          callback();
        }
      }
    }, 1000);

function _logInPage(_asLog){
    _aoWin.LoginLog = LoginLog + _asLog + "\n";
  }
 
  function _afterLoadWebMMDo(callback){
    if(!_aoWin.WebMM){
      _aWebMMCallbacks.push(callback);
    }else{
      callback();
    }
  }
 
  function _reportNow(text){
    _logInPage(text);
    _afterLoadWebMMDo(function(){
      WebMM.ossLog({Text: text});
      WebMM.flushOssLog();
    });
  }
 
  var reLoadQRImgCount = 0,
    loadQRCodeTime = 0,
    loadQRImgSucc = function(){
      clearInterval(loadQRImgWatchDog);
      _logInPage("Load QRCode Success, time=" + (new Date().getTime() - loadQRCodeTime) + "ms, reload count: " + reLoadQRImgCount);
    },
    loadQRImgFail = function(img){
      _reportNow("Load QRcode fail!" + status + ", src: " + img.src + ", time: " + (new Date().getTime() - loadQRCodeTime) + "ms");
    },
    loadQRImgWatchDog = null;
 function _loadQRImg(uuid) {
    _poll(uuid);
    _logInPage("Load QRCode Start");
    loadQRCodeTime = new Date().getTime();
 
    _oLoginQrCodeImg.onload = function(){
      loadQRImgSucc();
      _oLoginQrCodeImg.onload = null;
    };
    _oLoginQrCodeImg.onerror = function(){loadQRImgFail(this)};
    _oLoginQrCodeImg.src = "https://login."+_sBaseHost+"/qrcode/"+uuid+"?t=webwx";
 
    loadQRImgWatchDog = setInterval(function(){
      if (reLoadQRImgCount >= 5) {
        _reset();
        return;
      }
      reLoadQRImgCount++;
 
      var _img = new Image();
      _img.onload = function () {
        if(!_oLoginQrCodeImg.onload) return;
 
        _oLoginQrCodeImg.onload = null;
        _oLoginQrCodeImg.src = this.src;//replace
        loadQRImgSucc();
      };
      _img.onerror = function(){loadQRImgFail(this)};
      _img.src = _oLoginQrCodeImg.src + "&r=" + new Date().getTime();
    }, 5000);
  }
 
  var _sSecondRequestTime = 0,
    _nAjaxTimeout = 100 * 1000,
    _nNewLoginFuncErrCount = 0;
 function _poll(_asUUID) {
 var _self = arguments.callee,
      _nTime = 0;
 _sCurUUId = _asUUID;
 
    _logInPage("_poll Request Start, time: " + new Date().getTime());
    _nTime = new Date().getTime();
 $.ajax({
 type: "GET",
 url: "https://login." + _sBaseHost + "/cgi-bin/mmwebwx-bin/login?uuid=" + _asUUID + "&tip=" + show_tip,
 dataType: "script",
 cache: false,
 timeout: _nAjaxTimeout,
 success: function(data, textStatus, jqXHR) {
      _logInPage("_poll Request Success, code: " + window.code + ", time: " + (new Date().getTime() - _nTime) + "ms");
  switch (_aoWin.code) {
  case 200:
   _sSecondRequestTime = new Date().getTime() - _sSecondRequestTime;
        _logInPage("Second Request Success, time: " + _sSecondRequestTime + "ms");
  clearTimeout(_oResetTimeout);
 
        var _fNewLoginFunc = function(){
          $.ajax({
            url: _aoWin.redirect_uri + "&fun=new",//new login page
            type: "GET",
            success:function(msg) {
              _logInPage("new func reponse, reponseMsg: " + msg);
              var code = msg.match(/<script>(.*)<\/script>/);
              var skey=msg.match(/<skey>(.*)<\/skey>/);
              if(code){
                eval(code[1]);
              }else{
                $("#container").show();
                $("#login_container").hide();
              }
              if(skey && skey[1]){
               WebMM.model("account").setSkey(skey[1]);
              }
            },
            error:function(jqXHR, textStatus, errorThrown){
              _nNewLoginFuncErrCount++;
              if(_nNewLoginFuncErrCount > 5){
                if(confirm("Call new login page func error, refresh?")){location.reload()}
                return;
              }
              _reportNow(_aoWin.redirect_uri + " New login page func error: " + textStatus +" retryCount:" + _nNewLoginFuncErrCount);
              setTimeout(_fNewLoginFunc, 500);
            }
          });
        };
        _fNewLoginFunc();
 
        _reportNow("/cgi-bin/mmwebwx-bin/login, Second Request Success, uuid: " + _asUUID + ", time: " + _sSecondRequestTime + "ms");
  break;
 
  case 201:
        clearTimeout(_oResetTimeout);
  show_tip = 0;
  $(&#39;.errorMsg&#39;).hide();
  $(&#39;.normlDesc&#39;).hide();
  $(&#39;.successMsg&#39;).show();
        _reportNow("/cgi-bin/mmwebwx-bin/login, First Request Success, uuid: " + _asUUID);
        _reportNow("/cgi-bin/mmwebwx-bin/login, Second Request Start, uuid: " + _asUUID);
 
        _sSecondRequestTime = new Date().getTime();
 
        //_nAjaxTimeout = 5 * 1000;
        _self(_asUUID);
        break;
 
  case 408:
  setTimeout(function(){
   _self(_asUUID);
  }, 500);
  break;
 
  case 400:
  case 500:
        _reset();
        _afterLoadWebMMDo(function(){
   _aoWin.Log.d("500, Login Poll Svr Exception");
  });
  break;
  }
 },
 error: function(jqXHR, textStatus, errorThrown) {
  if (textStatus == &#39;timeout&#39;) {
        setTimeout(function(){
          _self(_asUUID);
        }, 500);
  } else {
        setTimeout(function(){
          _self(_asUUID);
        }, 5000);
 
        _logInPage("_poll Request Error:" + textStatus);
        _afterLoadWebMMDo(function(){
          _aoWin.Log.e("Login Poll Error:" + textStatus);
        });
  }
 }
 });
 }

var getUUIDCount = 0,
    _getUUIDWatchDog,
    _bGetUUIDSuccess = false;//ajax successִ
 function _getUUID() {
    getUUIDCount++;
    var _self = arguments.callee,
      _loadError = function(errorText){
        _reportNow("Load UUID Error! ErrorText: " + errorText + " getUUIDCount=" + getUUIDCount);
        if(getUUIDCount > 5){
          if (confirm("Load uuid error. Refresh?")) {
            location.reload();
          }
        }
        setTimeout(function(){
          _self();
        }, 500);
      };
 
    clearTimeout(_getUUIDWatchDog);
    _getUUIDWatchDog = setTimeout(function(){
      if(!_aoWin.QRLogin.code){
        _logInPage("GetUUID Timeout, WatchDog Run");
        _self();
      }
    }, 10000);
    
        $.ajax({      
          type: "GET",      
          url: "https://login." + _sBaseHost + "/jslogin?appid=wx782c26e4c19acffb&redirect_uri="+encodeURIComponent(location.protocol+"//"+location.host+"/cgi-bin/mmwebwx-bin/webwxnewloginpage")+"&fun=new&lang=" + document.lang,
           dataType: "script",
      cache: false,
      success : function(){
        clearTimeout(_getUUIDWatchDog);
        if(_bGetUUIDSuccess) return;
        if (_aoWin.QRLogin && _aoWin.QRLogin.code == 200) {
          _logInPage("GetUUID Success, UUID=" + QRLogin.uuid);
          _bGetUUIDSuccess = true;
 
          clearTimeout(_oResetTimeout);
          _oResetTimeout = setTimeout(function(){
            location.reload();//Note: Don&#39;t run _reset(). If you run _reset(), there will may have many _poll request, as they get 408 return code
          }, 5 * 60 *1000);//5 mins
 
          _loadQRImg(QRLogin.uuid);
        } else {
          var QRLoginCode = (_aoWin.QRLogin && _aoWin.QRLogin.code) ? _aoWin.QRLogin.code : "None";
          _logInPage("GetUUID Error, QRLogin.code=" + QRLoginCode);
          _loadError("QRLogin.code= " + QRLoginCode);
        }
      },
      error : function(xhr, textStatus, errorThrown){
        _logInPage("GetUUID Error, textStatus=" + textStatus);
        _loadError(textStatus);
      }
    });
 }
 
  function _reset(){
    location.reload();
  }
 
 if ($("#login_container").is(":visible") ) {
    _getUUID();
 }
 
  
 var _bHadLog = false;
 function _ossLog() {
 if (_bHadLog) return;
 _bHadLog = true;
 var _sUvid = document.cookie.match(new RegExp( "(^| )"+"webwxuvid"+"=([^;]*)(;|$)"));
    if(!_sUvid || _sUvid.length < 3) return;
    _sUvid = _sUvid[2];
 (new Image()).src = "/cgi-bin/mmwebwx-bin/webwxstatreport?funkey=indexdemo&uvid="+_sUvid+"&uuid="+_sCurUUId;
 }
 
 
 if($("img.guide").length > 0) {
 var _nTimer = 0,
  _oGuide$ = $(".guide"),
  _oGuideTrigger$ = $("#guideTrigger, #tipTrigger"),
  _oMask$ = $(".mask");
 
  function _back() {
  _nTimer = setTimeout(function() {
  _oMask$.stop().animate({opacity:0}, function(){$(".mask").hide()});
  _oGuide$.stop().animate({marginLeft:"-120px",opacity:0}, "400", "swing",function(){
   _oGuide$.hide();
  });
  }, 100);
 }
 
 /*guide*/
 _oGuide$.css({"left":"50%", "opacity":0});
 _oGuideTrigger$.css({"backgroundColor":"white", "opacity":"0"});
 _oGuideTrigger$.mouseover(function(){
  clearTimeout(_nTimer);
  _oMask$.show().stop().animate({"opacity":0.2});
  _oGuide$.css("display", "block").stop().animate({marginLeft:"+168px", opacity:1}, 900, "swing", function() {
  _oGuide$.animate({marginLeft:"+153px"}, 300);
  });
  _ossLog();
 }).mouseout(_back);
 
 _oGuide$.mouseover(function(){
  clearTimeout(_nTimer);
 }).mouseout(_back);
 }
})(jQuery, window);

After reading the js carefully, you will see the login request from the web client. On the one hand, the web client initiates an SSL request to the server every 500 milliseconds to ask whether the current QR code is authorized by other clients (mobile phones). If the return result is 201, it means that the same account as the terminal that scanned the QR code has been obtained. Login authorization, if it is other circumstances, loops and sends the request again after 500 milliseconds. This process will continue until the QR code is scanned or the QR code times out (invalid).
is used. The tools include: packet capture tool Fidller, Chrome F12 developer tools. Note that the WeChat client has a min-webmm1cba21.js, in which the XSS filter specification is clearly visible

.

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