JS逆向|使用express框架开启服务并替换加密字符串

在阅读本文之前请确保电脑已安装好Node.js.

express,根据其Github上的描述，是一个:

Fast, unopinionated, minimalist web framework for node.

其Github地址：

https://github.com/expressjs/express

根据其Readme文档，安装:

npm install express

保存演示code:

const express = require('express')

const app = express()

app.get('/', function (req, res) {

res.send('Hello World')

})

app.listen(3000)

然后运行(控制台下输入node xxx.js),并打开浏览器，输入:

http://127.0.0.1:3000/

并回车，得到浏览器上的结果:

当然，这仅仅是个简单的例子，还需要了解function (req, res)的用途，上面的代码稍微改一下:

app.get('/', function (req, res) {

console.log(req.query);  //只增加这一行，看看打印结果

res.send('Hello World')

})

在浏览器上输入如下URL，并回车:

http://127.0.0.1:3000/?sign=123456

查看命令行下的结果:

这样就清楚了，直接构造参数，然后用res.send返回结果。

继续沿用上一篇文章的代码，将 大数组 + 位移函数 + 解密函数的代码添加进来，并构造参数，如下:

const express = require('express')

const app = express()

var _0x2075 = ['wrw3EMKc', 'BBdBHWk=', 'wplgd8O5dHbDtFfDucK9CsOS', 'f8KvAcKewoDClg==', 'XcKowo9uOyfChw==', 'XcKowpRzOzDCgMKuw5vCtH8=', 'HmQkw5vDt8OIBDbCpMKdw6Aaw7HDmcKb', 'wpxzdMO4', 'R8KHF1k1w5A=', 'w4LDgcOowrjDhg==', 'w6RKw6PCmVDDpw==', 'w6DDgsKrCsK5wqAwKsOMTkPDilwgB241RVBIw6rCvwpWw5fCo8OSw59pBcK7UlrCucOZHy7DgsO5wpx5J8K5wqbCtMOMwqvCsiUFw5s4JGfDmwQPw7Fawq3CgXlkJyE=', 'VcObYsOHKcKpwpI=', 'KkZfcE52w77ChsKgUQ==', 'CmQsw57DvA==', 'YV7CscOYZg==', 'w5jDt8OUwr46w5c6LsKEPsO0', 'F8OUMQhRw78Q', 'YMKzeTvCpMKzHcKKGSjCj2dJwq3Cj3/ChsKSFVpMw4sZwrg9H8OLw4/DqUlhYlpaa8KYJsO5AcK2wqnCmGhEwqkbdMKKLsO/wpBFMcKlC8OvKUkXZ8KpBsOxw4XDk8K5w4Y6w7VZO8K/wojCqcO2wqQow5Z+w6dew7I3TMObw6Ykw7I=', 'Mk8Bw6QawqU=', 'wo5zw4vCkxvDuSBqwoENw7rCrF3DksKewoPDqMKHNSzCgcK2fcKxPMKbGcKwCW5GZWRpw6fDmgHCjXrCnXE3w4zDqlt3w64lw7JiworDi8Knw5YoW1LDlUbDpkEtGQPDnw==', 'w6lvdMKW', 'w7JFdsOhwrBqwrlMYcKVJRjCuMKQwpLDtMONwprCsMORw4BtRV0oeEQPCgAmMgx2'];

(function(_0xf486e7, _0x2075d7) {

var _0x5c3a18 = function(_0x5b65b1) {

while (--_0x5b65b1) {

_0xf486e7['push'](_0xf486e7['shift']());

}

};

_0x5c3a18(++_0x2075d7);

}(_0x2075, 0xa4));

var _0x5c3a = function(_0xf486e7, _0x2075d7) {

_0xf486e7 = _0xf486e7 - 0x0;

var _0x5c3a18 = _0x2075[_0xf486e7];

if (_0x5c3a['vEVEZj'] === undefined) {

(function() {

var _0x2e1ca4;

try {

var _0x28e173 = Function('return\x20(function()\x20' + '{}.constructor(\x22return\x20this\x22)(\x20)' + ');');

_0x2e1ca4 = _0x28e173();

} catch (_0x16acc9) {

_0x2e1ca4 = window;

}

var _0x16f958 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

_0x2e1ca4['atob'] || (_0x2e1ca4['atob'] = function(_0x5a7812) {

var _0x3c7e74 = String(_0x5a7812)['replace'](/=+$/, '');

var _0x5e030c = '';

for (var _0x4eaee2 = 0x0, _0x5954ef, _0x29200e, _0x5a128b = 0x0; _0x29200e = _0x3c7e74['charAt'](_0x5a128b++); ~_0x29200e && (_0x5954ef = _0x4eaee2 % 0x4 ? _0x5954ef * 0x40 + _0x29200e : _0x29200e,

_0x4eaee2++ % 0x4) ? _0x5e030c += String['fromCharCode'](0xff & _0x5954ef >> (-0x2 * _0x4eaee2 & 0x6)) : 0x0) {

_0x29200e = _0x16f958['indexOf'](_0x29200e);

}

return _0x5e030c;

}

);

}());

var _0x3acf89 = function(_0x593a19, _0xfee22e) {

var _0x1b5349 = [], _0x4ddb21 = 0x0, _0x28ed27, _0x4b4996 = '', _0xbdd0c6 = '';

_0x593a19 = atob(_0x593a19);

for (var _0x1d6343 = 0x0, _0x3f947e = _0x593a19['length']; _0x1d6343 < _0x3f947e; _0x1d6343++) {

_0xbdd0c6 += '%' + ('00' + _0x593a19['charCodeAt'](_0x1d6343)['toString'](0x10))['slice'](-0x2);

}

_0x593a19 = decodeURIComponent(_0xbdd0c6);

var _0x1a120c;

for (_0x1a120c = 0x0; _0x1a120c < 0x100; _0x1a120c++) {

_0x1b5349[_0x1a120c] = _0x1a120c;

}

for (_0x1a120c = 0x0; _0x1a120c < 0x100; _0x1a120c++) {

_0x4ddb21 = (_0x4ddb21 + _0x1b5349[_0x1a120c] + _0xfee22e['charCodeAt'](_0x1a120c % _0xfee22e['length'])) % 0x100;

_0x28ed27 = _0x1b5349[_0x1a120c];

_0x1b5349[_0x1a120c] = _0x1b5349[_0x4ddb21];

_0x1b5349[_0x4ddb21] = _0x28ed27;

}

_0x1a120c = 0x0;

_0x4ddb21 = 0x0;

for (var _0x585b7f = 0x0; _0x585b7f < _0x593a19['length']; _0x585b7f++) {

_0x1a120c = (_0x1a120c + 0x1) % 0x100;

_0x4ddb21 = (_0x4ddb21 + _0x1b5349[_0x1a120c]) % 0x100;

_0x28ed27 = _0x1b5349[_0x1a120c];

_0x1b5349[_0x1a120c] = _0x1b5349[_0x4ddb21];

_0x1b5349[_0x4ddb21] = _0x28ed27;

_0x4b4996 += String['fromCharCode'](_0x593a19['charCodeAt'](_0x585b7f) ^ _0x1b5349[(_0x1b5349[_0x1a120c] + _0x1b5349[_0x4ddb21]) % 0x100]);

}

return _0x4b4996;

};

_0x5c3a['HKkhxp'] = _0x3acf89;

_0x5c3a['eabUGz'] = {};

_0x5c3a['vEVEZj'] = !![];

}

var _0x5b65b1 = _0x5c3a['eabUGz'][_0xf486e7];

if (_0x5b65b1 === undefined) {

if (_0x5c3a['vszZjY'] === undefined) {

_0x5c3a['vszZjY'] = !![];

}

_0x5c3a18 = _0x5c3a['HKkhxp'](_0x5c3a18, _0x2075d7);

_0x5c3a['eabUGz'][_0xf486e7] = _0x5c3a18;

} else {

_0x5c3a18 = _0x5b65b1;

}

return _0x5c3a18;

};

app.get('/', function (req, res) {

//req.query = {callback:"_0x5c3a('0x8', 'CwZq')"}

let callback = req.query.callback;

let value = eval(callback); //直接eval计算传递进来的解密函数及参数

console.log(callback,value);

res.send(value) //结果

})

app.listen(3000)

在node下运行后，在浏览器上进行简单的测试:

http://127.0.0.1:3000/?callback=_0x5c3a('0x8', 'CwZq')

回车后的结果:

这样，我们就可以用requests库进行请求，代码如下:

reg = re.compile(r"_0x5c3a\([\s\S]{12,14}'\)")

results = reg.findall(code) # code是所有混淆代码

for result in results:

params = {"callback":result} #构造参数

r = requests.get("http://127.0.0.1:3000/",params = params) #请求

print (result,r.text) #打印结果

code = code.replace(result,"'" + r.text + "'") #全局替换

结果如下:

和上一篇文章的结果一致，但效果明显要好很多，特别是在处理多个这样的调用时，其性能不是一个量级，因此在这里建议，卸载掉电脑上的pyexecjs在这个库吧，反正也没再更新了。

不过这里在使用get时，遇到了一个坑，就是当提交的参数里面包含特殊字符时(比如'&'),可能会解析错误，因此建议使用post方式，可自行百度相关教程。

Express

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