JS逆向:Webpack打包后的代码怎么搞？猿人学爬虫比赛第十六题详细题解

2023-11-02

实战地址

http://match.yuanrenxue.com/match/16

抓包分析

地址栏输入地址，按下F12并回车，发现数据在这里:

查看cookie，无加密相关的字段。请求的接口倒是有个m的加密参数，看来这题的主要目的就是看看m参数怎么进行加密的吧。

切换 Initiator,这请求也太明显了，点击下面所示的js文件:

跟进去并美化后，来到这里:

不用过多分析，m加密在这里:

r.m = n[e(528)](btoa, p_s),
r.t = p_s;

而这个实参 p_s 是由上面的这行代码生成的:

p_s = Date[e(496)](new Date)[e(517)]();

在 r.m 赋值的这行打上断点，请求第二页,控制台输入 btoa 并回车,双击跟进，来到这里:

看这个混淆，很明显的 obfuscator 混淆，直接将整个 732 copy下来保存到文件，并写出AST插件进行反混淆：

进行反混淆和删除垃圾代码，优化后的btoa函数:

function btoa(e) {
  var f = "U9876543210zyxwvutsrqpomnlkjihgfdecbaZXYWVUTSRQPONABHICESQWK2Fi+9876543210zyxwvutsrqpomnlkjihgfdecbaZXYWVUTSRQPONABHICESQWK2Fi";
  for (var o, a, s, l = 0, c = []; l < e["length"];) {
    a = e["charCodeAt"](l), s = l % 6;
    switch (s) {
      case 0:
        c["push"](f["charAt"](a >> 2));
        break;


      case 1:
          c["push"](f["charAt"]((2 & o) << 3 | a >> 4));
        break;


      case 2:
        c["push"](f["charAt"]((15 & o) << 2 | a >> 6)), c["push"](f["charAt"](a & 63));
        break;


      case 3:
        c["push"](f["charAt"](a >> 3));
        break;


      case 4:
        c["push"](f["charAt"]((o & 4) << 6 | a >> 6));
        break;


      case 5:
        c["push"](f["charAt"]((o & 15) << 4 | a >> 8)), c["push"](f["charAt"](a & 63));
    }


    o = a, l++;
  }
  
  c["push"](f["charAt"]((o & 3) << 4)), c["push"]("FM");
  
  return d(15) + md5(c["join"]("")) + d(10);
}

这里可以看到还有 d 函数和 md5 函数，分别进行抠取和优化。

优化后的d函数:

function d(e) {
  e = e ||32;
  var l = "ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678";
  var s = l["length"];
  var c = "";
  for (i = 0; i < e; i++) c += l["charAt"](Math["floor"](Math["random"]() * s));
  return c;
}

优化后的md5函数:

function md5(e) {
  function o(e, n) {
    e[n >> 5] |= 128 << n % 32;
    e[(n + 64 >>> 9 << 4) + 14] = n;
    var b = 1732584193;
    var x = -271733879;
    var T = -1732584194;
    var w = 271733878;


    for (var d = 0; d < e["length"]; d += 16) {
      var m = b;
      var y = x;
      var v = T;
      var g = w;
      b = s(b, x, T, w, e[d + 0], 7, -680976936);
      w = s(w, b, x, T, e[d + 1], 12, -389564586);
      T = s(T, w, b, x, e[d + 2], 17, 606105819);
      x = s(x, T, w, b, e[d + 3], 22, -1044525330);
      b = s(b, x, T, w, e[d + 4], 7, -176418897);
      w = s(w, b, x, T, e[d + 5], 12, 1200080426);
      T = s(T, w, b, x, e[d + 6], 17, -1473231341);
      x = s(x, T, w, b, e[d + 7], 22, -45705983);
      b = s(b, x, T, w, e[d + 8], 7, 1770035416);
      w = s(w, b, x, T, e[d + 9], 12, -1958414417);
      T = s(T, w, b, x, e[d + 10], 17, -42063);
      x = s(x, T, w, b, e[d + 11], 22, -1990404162);
      b = s(b, x, T, w, e[d + 12], 7, 1804550682);
      w = s(w, b, x, T, e[d + 13], 12, -40341101);
      T = s(T, w, b, x, e[d + 14], 17, -1502002290);
      x = s(x, T, w, b, e[d + 15], 22, 1236531029);
      b = l(b, x, T, w, e[d + 1], 5, -165796510);
      w = l(w, b, x, T, e[d + 6], 9, -1069501632);
      T = l(T, w, b, x, e[d + 11], 14, 643717713);
      x = l(x, T, w, b, e[d + 0], 20, -373897302);
      b = l(b, x, T, w, e[d + 5], 5, -701520691);
      w = l(w, b, x, T, e[d + 10], 9, 38016083);
      T = l(T, w, b, x, e[d + 15], 14, -660478335);
      x = l(x, T, w, b, e[d + 4], 20, -405537848);
      b = l(b, x, T, w, e[d + 9], 5, 568446438);
      w = l(w, b, x, T, e[d + 14], 9, -1019803690);
      T = l(T, w, b, x, e[d + 3], 14, -187363961);
      x = l(x, T, w, b, e[d + 8], 20, 1163531501);
      b = l(b, x, T, w, e[d + 13], 5, -1444681467);
      w = l(w, b, x, T, e[d + 2], 9, -51403784);
      T = l(T, w, b, x, e[d + 7], 14, 1735328473);
      x = l(x, T, w, b, e[d + 12], 20, -1921207734);
      b = u(b, x, T, w, e[d + 5], 4, -378558);
      w = u(w, b, x, T, e[d + 8], 11, -2022574463);
      T = u(T, w, b, x, e[d + 11], 16, 1839030562);
      x = u(x, T, w, b, e[d + 14], 23, -35311556);
      b = u(b, x, T, w, e[d + 1], 4, -1530992060);
      w = u(w, b, x, T, e[d + 4], 11, 1272893353);
      T = u(T, w, b, x, e[d + 7], 16, -155497632);
      x = u(x, T, w, b, e[d + 10], 23, -1094730640);
      b = u(b, x, T, w, e[d + 13], 4, 681279174);
      w = u(w, b, x, T, e[d + 0], 11, -358537222);
      T = u(T, w, b, x, e[d + 3], 16, -722881979);
      x = u(x, T, w, b, e[d + 6], 23, 76029189);
      b = u(b, x, T, w, e[d + 9], 4, -640364487);
      w = u(w, b, x, T, e[d + 12], 11, -421815835);
      T = u(T, w, b, x, e[d + 15], 16, 530742520);
      x = u(x, T, w, b, e[d + 2], 23, -995338651);
      b = c(b, x, T, w, e[d + 0], 6, -198630844);
      w = c(w, b, x, T, e[d + 7], 10, 11261161415);
      T = c(T, w, b, x, e[d + 14], 15, -1416354905);
      x = c(x, T, w, b, e[d + 5], 21, -57434055);
      b = c(b, x, T, w, e[d + 12], 6, 1700485571);
      w = c(w, b, x, T, e[d + 3], 10, -1894446606);
      T = c(T, w, b, x, e[d + 10], 15, -1051523);
      x = c(x, T, w, b, e[d + 1], 21, -2054922799);
      b = c(b, x, T, w, e[d + 8], 6, 1873313359);
      w = c(w, b, x, T, e[d + 15], 10, -30611744);
      T = c(T, w, b, x, e[d + 6], 15, -1560198380);
      x = c(x, T, w, b, e[d + 13], 21, 1309151649);
      b = c(b, x, T, w, e[d + 4], 6, -145523070);
      w = c(w, b, x, T, e[d + 11], 10, -1120210379);
      T = c(T, w, b, x, e[d + 2], 15, 718787259);
      x = c(x, T, w, b, e[d + 9], 21, -343485551);
      b = f(b, m);
      x = f(x, y);
      T = f(T, v);
      w = f(w, g);
    }


    return Array(b, x, T, w);
  }


  function a(e, n, r, o, a, s) {
    return f(d(f(f(n, e), f(o, s)), a), r);
  }


  function s(e, n, r, o, s, l, u) {
    return a(n & r | ~n & o, e, n, s, l, u);
  }


  function l(e, n, r, o, s, l, u) {
    return a(n & o | r & ~o, e, n, s, l, u);
  }


  function u(e, n, r, o, s, l, u) {
    return a(n ^ r ^ o, e, n, s, l, u);
  }


  function c(e, n, r, o, s, l, u) {
    return a(r ^ (n | ~o), e, n, s, l, u);
  }


  function f(e, n) {
    var o = (65535 & e) + (n & 65535),
        a = (e >> 16) + (n >> 16) + (o >> 16);
    return a << 16 | o & 65535;
  }


  function d(e, n) {
    return e << n | e >>> 32 - n;
  }


  function p(e) {
    for (var r = Array(), o = 65535, a = 0; a < e["length"] * 16; a += 16) r[a >> 5] |= (e["charCodeAt"](a / 16) & o) << a % 32;


    return r;
  }


  function h(e) {
    for (var r = "0123456789abcdef", o = "", a = 0; a < e["length"] * 4; a++) o += r["charAt"](15 & e[a >> 2] >> a % 4 * 8 + 4) + r["charAt"](15 & e[a >> 2] >> a % 4 * 8);


    return o;
  }


  return function (e) {
    return h(o(p(e), 16 * e["length"]));
  }(e);
}

代码合并后，运行不再报错。很快就写出了 Python代码:

# -*- coding: utf-8 -*-
import time
import execjs
import requests




def main():
    sums = 0
    headers = {"User-Agent": "yuanrenxue.project",}


    with open("decode_16.js","r",encoding = "utf-8") as fp:
        jscode = fp.read()


    ctx = execjs.compile(jscode)
    
    for i in range(1, 6):
        t = str(int(time.time()*1000))


        m = ctx.call("btoa",t)
        
        params = {
            "m":m,
            "page":i,
            "t":t,
            }
        response = requests.get(url="http://match.yuanrenxue.com/api/match/16",params = params,headers=headers).json()
        for each in response["data"]:
            sums += each["value"]
    print(sums)
    # 287383




if __name__ == "__main__":
    main()

对于这个webpack打包的网站来说，基本没啥难度吧，先优化一波，去混淆，删除垃圾代码，再缺啥补啥就好，浏览器相关的都不用补。

当然，webpack也有技巧，不过很少用的，无脑抠就好，然后缺啥补啥。

我也不喜欢一大坨代码搞在一起，简单点，事情简单点，心情或许会好很多。

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