JS逆向|非常实用的扣代码教程来了，欢迎收藏

痛定思痛。 2022-12-19 03:44 74阅读 0赞

声明：本文只作学习研究，禁止用于非法用途，否则后果自负，如有侵权，请告知删除，谢谢！

经过简单的分析，已知某网站参数的加密位置在这里:

![format_png][]

在控制台下输入f()并回车:

![format_png 1][]

跟进该函数后，在第一行打上断点:

![format_png 2][]

按下快捷键F8，停在此处:

![format_png 3][]

单步执行，来到这行:

![format_png 4][]

代码 var n = r.wordsToBytes(s(t, e));调用了两个函数，分别是r.wordsToBytes 和 s,在控制台看看t,e的值:

![format_png 5][]

t是上面讲到的固定的实参，e则未定义，不用理会，因此我们先将s函数扣出来看看,按照上面的方法，控制台输入s并回车跟进，来到这里:

![format_png 6][]

一直到这里，都是与s相关的代码:

![format_png 7][]

因此，将这段代码扣出来,保存到文件(我这里命名为md5.js),注意去掉**s前面的括号**以及:

![format_png 8][]

保存以后，构造一个实参，并调用s函数:

![format_png 9][]

直接在node下面跑一下，看看报啥错:

![format_png 10][]

提示这里的o未定义，那跟进代码里面看看o是怎么定义的:

![format_png 11][]

分析代码不难得知，这里实际是调用了o.stringToBytes这个函数，控制台输入看看:

![format_png 12][]

双击跟进，来到这里:

![format_png 13][]

直接把这个 n 对象扣出来，加入到s函数代码中，然后在照着逻辑加入这么一行代码:

![format_png 14][]

再次运行，看结果:

![format_png 15][]

再次报错，r未定义，按照之前的方法，跟进到r相关的代码在这里:

![format_png 16][]

发现此时又定义了一个n，是base64的码表，因此按照上面的方式进入s函数肯定是不行的，因为变量名的污染，也导致的代码的臃肿，我这里以返回值的形式赋值，代码如下:

再次运行，有结果了:

![format_png 17][]

回到浏览器，看看这个s函数的值是否正确:

![format_png 18][]

控制台输入s(t,e):

![format_png 19][]

扣到这里，再分析函数r.wordsToBytes，发现居然就是刚才扣的r对象，这下就省事多了，直接比对结果吧:

![format_png 20][]

在扣出来的代码上添加输出即可:

console.log(r.wordsToBytes(s(tmp)));

运行看结果:

![format_png 21][]

与上面的结果也是惊人的一致。

回到浏览器，看这里return的是啥:

![format_png 22][]

这是一个三目表达式，直接在浏览器上看看逻辑：

![format_png 23][]

可以看到，最终执行了r.bytesToHex(n)，在扣出来的代码上添加输出:

console.log(r.bytesToHex(r.wordsToBytes(s(tmp))));

![format_png 24][]

可以看到，结果出来了。

至此，代码抠取完毕。至于怎么给Python调用，请参考之前的两篇文章。

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