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JSFuck、AAEncode、JJEncode 都是同一个作者,JSFuck 由日本的 Yosuke HASEGAWA 在 2010 创造,它可以将任意 JavaScript 编码为仅使用 6 个符号的混淆形式 []()!+
,2012 年,Martin Kleppe 在 GitHub 上创建了一个 jsfuck 项目和一个 JSFuck.com 网站,其中包含使用该编码器实现的 Web 应用程序。JSFuck 可用于绕过对网站上提交的恶意代码的检测,例如跨站点脚本(XSS)攻击。JSFuck 的另一个潜在用途在于代码混淆,目前的 jQuery 就已经有经过 JSFuck 混淆后的功能齐全的版本。
在线体验地址:https://utf-8.jp/public/jsfuck.html http://www.jsfuck.com/
正常的一段 JS 代码:
alert(1)
经过 JSFuck 混淆之后的代码类似于:
[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((!![]+[])[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+!+[]]+(+[![]]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+!+[]]]+(!![]+[])[!+[]+!+[]+!+[]]+(+(!+[]+!+[]+!+[]+[+!+[]]))[(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([]+[])[([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]][([][[]]+[])[+!+[]]+(![]+[])[+!+[]]+((+[])[([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]+[])[+!+[]+[+!+[]]]+(!![]+[])[!+[]+!+[]+!+[]]]](!+[]+!+[]+!+[]+[!+[]+!+[]])+(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]])()((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[+!+[]+[!+[]+!+[]+!+[]]]+[+!+[]]+([+[]]+![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[!+[]+!+[]+[+[]]])
JSFuck 中常见的元素、数字、符号转换如下表,更多元素可参考 JSFuck 官方 GitHub 或 JSFuck 维基百科:
Value | JSFuck |
---|---|
false | ![] |
true | !![] or !+[] |
NaN | +[![]] |
undefined | [][[]] |
Infinity | +(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+[+!+[]]+[+[]]+[+[]]+[+[]]) |
Array | [] |
Number | +[] |
String | []+[] |
Boolean | ![] |
Function | []["filter"] |
eval | []["filter"]["constructor"]( CODE )() |
window | []["filter"]["constructor"]("return this")() |
+ | (+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+[+!+[]]+[+[]]+[+[]])+[])[!+[]+!+[]] |
. | (+(+!+[]+[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+[!+[]+!+[]]+[+[]])+[])[+!+[]] |
0 | +[] |
1 | +!![] or +!+[] |
2 | !![]+!![] or !+[]+!+[] |
3 | !![]+!![]+!![] or !+[]+!+[]+!+[] |
a | (![]+[])[+!+[]] |
d | ([][[]]+[])[!+[]+!+[]] |
e | (!![]+[])[!+[]+!+[]+!+[]] |
f | (![]+[])[+[]] |
我们以字母 a 为例,来演示一遍其混淆的流程:
"false"[1]
:字母 a 取自字符串 false,在 false 中,a 的索引值是 1;(false+[])[1]
:false 可以写成 false+[],即布尔常量 false 加上一个空数组;(![]+[])[1]
:false 又可以写成 ![],即否定应用于空数组;(![]+[])[+true]
:1 是一个数字,我们可以把它写成 +true;(![]+[])[+!![]]
:由于 false 是 ![],所以 true 就是 !![],生成最终混淆代码。JSFuck 在调用方法时通常都是通过 Function(xxx)() 和 eval(xxx) 的形式来执行,因此 JSFuck 常见解混淆的方式如下:
如前面 alert(1)
的混淆代码,复制最外层最后一个括号内的内容到浏览器,就可以看到源代码:
逆向的目标主要是翻页接口 _signature
参数,调用的加密方法仍然是 window.get_sign()
,和前面几题是一样的,本文不再赘述,不清楚的可以去看 K 哥上期的文章。
继续跟进,会发现是一个 JSFuck 混淆:
我们将这段代码复制出来,放到编辑器里面,这里以 PyCharm 为例,由于我们要选中匹配括号里的内容,所以我们可以设置一下 PyCharm 括号匹配高亮为红色,便于我们查找,依次点击 File - Settings - Editor - Color Scheme - General - Code - Matched brace,设置 Background 为显眼的颜色:
此时我们选中最后一个括号,往上找,就可以非常明显地看到与之匹配的另一个括号,如下图所示:
我们将括号里面的内容复制出来(可以包含括号,也可以不包含),放到浏览器控制台运行一下,就可以看到源码了:
除了这种方法以外,我们还可以使用 Hook 的方式,直接捕获源码然后打印输出,注意到这段混淆代码最后没有 ()
括号,那就是 eval 的方式执行的,我们编写 Hook eval 代码如下:
eval_ = eval;
eval = function (a){
debugger;
return eval_()
}
// 另外提供一个 Hook Function 的代码
// Function.prototype.constructor_ = Function.prototype.constructor;
// Function.prototype.constructor = function (a) {
// debugger;
// return Function.prototype.constructor_(a);
// };
刷新网页,直接断下,此时 a 的值就是源码:
将源码复制下来,本地分析一下:
(function () {
let time_tmp = Date.now();
let date = Date.parse(new Date());
window = {};
let click = window.document.onclick;
let key_tmp;
let iv_tmp;
if (!click) {
key_tmp = date * 1234;
} else {
key_tmp = date * 1244;
}
if (time_tmp - window.time < 1000) {
iv_tmp = date * 4321;
} else {
iv_tmp = date * 4311;
}
const key = CryptoJS.enc.Utf8.parse(key_tmp);
var iv = CryptoJS.enc.Utf8.parse(iv_tmp);
(function tmp(date, key, iv) {
function Encrypt(word) {
let srcs = CryptoJS.enc.Utf8.parse(word);
let encrypted = CryptoJS.AES.encrypt(srcs, key, {
iv: iv,
mode: CryptoJS.mode.CBC,
padding: CryptoJS.pad.Pkcs7
});
return encrypted.ciphertext.toString().toUpperCase();
}
window.sign = Encrypt(date);
})(date, key, iv);
})();
可以看到就是一个 AES 加密,这里主要注意有两个 if-else 语句,第一个判断是否存在 window.document.onclick
,第二个是时间差的判断,我们可以在控制台去尝试取一下 window.document.onclick
和 window.time
,看一下到底走的是 if 还是 else,在本地把这两个值也补全即可,实际上经过K哥测试 window.document.onclick
为 null,然后不管是走 if 还是 else 都是可以拿到结果的,所以对于本题来说,两个 window 对象都无所谓,直接去掉,key_tmp
和 iv_tmp
任意取值都可以。
自此本题分析完毕,本地改写之后,配合 Python 代码携带 _signature 挨个计算每一页的数据,最终提交成功:
GitHub 关注 K 哥爬虫,持续分享爬虫相关代码!欢迎 star !https://github.com/kgepachong/
以下只演示部分关键代码,不能直接运行! 完整代码仓库地址:https://github.com/kgepachong/crawler/
/* ==================================
# @Time : 2021-12-13
# @Author : 微信公众号:K哥爬虫
# @FileName: challenge_4.js
# @Software: PyCharm
# ================================== */
var CryptoJS = require('crypto-js')
let date = Date.parse(new Date());
window = {};
let key_tmp = date * 1234;
// let key_tmp = date * 1244;
let iv_tmp = date * 4321;
// let iv_tmp = date * 4311;
const key = CryptoJS.enc.Utf8.parse(key_tmp);
var iv = CryptoJS.enc.Utf8.parse(iv_tmp);
(function tmp(date, key, iv) {
function Encrypt(word) {
let srcs = CryptoJS.enc.Utf8.parse(word);
let encrypted = CryptoJS.AES.encrypt(srcs, key, {
iv: iv,
mode: CryptoJS.mode.CBC,
padding: CryptoJS.pad.Pkcs7
});
return encrypted.ciphertext.toString().toUpperCase();
}
window.sign = Encrypt(date);
})(date, key, iv);
function getSign() {
return window.sign
}
// 测试输出
// console.log(getSign())
# ==================================
# --*-- coding: utf-8 --*--
# @Time : 2021-12-13
# @Author : 微信公众号:K哥爬虫
# @FileName: challenge_4.py
# @Software: PyCharm
# ==================================
import execjs
import requests
challenge_api = "http://spider.wangluozhe.com/challenge/api/4"
headers = {
"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",
"Cookie": "将 cookie 值改为你自己的!",
"Host": "spider.wangluozhe.com",
"Origin": "http://spider.wangluozhe.com",
"Referer": "http://spider.wangluozhe.com/challenge/4",
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36",
"X-Requested-With": "XMLHttpRequest"
}
def get_signature():
with open('challenge_4.js', 'r', encoding='utf-8') as f:
ppdai_js = execjs.compile(f.read())
signature = ppdai_js.call("getSign")
print("signature: ", signature)
return signature
def main():
result = 0
for page in range(1, 101):
data = {
"page": page,
"count": 10,
"_signature": get_signature()
}
response = requests.post(url=challenge_api, headers=headers, data=data).json()
for d in response["data"]:
result += d["value"]
print("结果为: ", result)
if __name__ == '__main__':
main()