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申明
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逆向指标
- 指标：网洛者反反爬虫练习平台第七题：JSVMPZL 初体验
- 链接：http://spider.wangluozhe.com/…
- 简介：平台注册须要邀请码，站长在群里，可后盾回复交换群加群获取，或者间接加网站底部站长 QQ 获取。要求采集 100 页的全副数字，并计算所有数据加和。次要难点在于 vvv 大佬开发的 JS 混同框架：jsvmpzl
逆向过程
间接搜寻，或者跟栈，能够轻松找到加密入口，关上 F12 有两个反调试，一是有限 debugger，右键 Never pause here 即可，二是定时器，控制台输出 for (let i = 1; i < 99999; i++) window.clearInterval(i); 过掉即可。
跟进 y__()，就能够看到 jsvmpzl 混同的代码了，如果有做过猿人学平台的题，会发现此混同和猿人学第 18 题（https://match.yuanrenxue.com/…）是一样的，在 y__() 第一行下个断点，察看 __v_() 第一个参数 _，_[2][0] 你会发现无关 MD5 算法的一些特色，如下图所示：
那么咱们间接大胆猜想一下，是不是就是某个数据通过 MD5 之后就是 _signature 了呢？再持续调试一下，留神 arguments 的变动：
很显著这个 window.byted_acrawler(window.sign()) 应该就是生成 _signature 的语句，这个办法和某字节系的 _signature 生成的办法名称是一样的，间接在控制台输入一下能够拿到值，其中 window.sign() 是取的工夫戳：
咱们后面猜想是 MD5，间接验证一下，发现并不是的，即使是同一个工夫戳，通过 window.byted_acrawler() 后失去的值每次也都不一样：
Hook 要害办法
通过后面的剖析，既然规范的 MD5 不行，那有没有可能是魔改的 MD5 呢？首先找个 JavaScript 规范的 MD5 代码看一下，比方：http://pajhome.org.uk/crypt/m…
能够留神到，源码外面有很多 md5_ff、md5_gg、md5_hh、md5_ii 的办法，最初一个值都是固定的，那么有没有可能此题就是在规范 MD5 的根底上批改了一些默认值呢？所以咱们能够间接 Hook 这些要害办法，在控制台输入传入的值，来一一比照一下，看看默认值是否是一样的，为了不便察看，咱们还能够为输入语句加上色彩，Hook 代码如下：
let oldFF = _[2][0]['md5_ff'];
let oldGG = _[2][0]['md5_gg'];
let oldHH = _[2][0]['md5_hh'];
let oldII = _[2][0]['md5_ii'];
let color_white_red = "color: white; background: red;"
let color_white_grey = "color: white; background: grey;"
let color_white_darkcyan = "color: white; background: darkcyan;"
let color_white_green = "color: white; background: green;"
let color_white_orange = "color: white; background: orange;"
_[2][0]['md5_ff'] = function (a, b, c, d, e, f, g) {
debugger;
let result = oldFF(a, b, c, d, e, f, g);
console.log("%c Function: %c md5_ff %c Result: %c %s %c Params: %c %s, %s, %s, %s, %s, %s, %s", color_white_red, color_white_grey, color_white_red, color_white_grey, result, color_white_red, color_white_grey, a, b, c, d, e, f, g)
return result;
};
_[2][0]['md5_gg'] = function (a, b, c, d, e, f, g) {
debugger;
let result = oldGG(a, b, c, d, e, f, g);
console.log("%c Function: %c md5_gg %c Result: %c %s %c Params: %c %s, %s, %s, %s, %s, %s, %s", color_white_red, color_white_darkcyan, color_white_red, color_white_darkcyan, result, color_white_red, color_white_darkcyan, a, b, c, d, e, f, g)
return result;
};
_[2][0]['md5_hh'] = function (a, b, c, d, e, f, g) {
debugger;
let result = oldHH(a, b, c, d, e, f, g);
console.log("%c Function: %c md5_hh %c Result: %c %s %c Params: %c %s, %s, %s, %s, %s, %s, %s", color_white_red, color_white_green, color_white_red, color_white_green, result, color_white_red, color_white_green, a, b, c, d, e, f, g)
return result;
};
_[2][0]['md5_ii'] = function (a, b, c, d, e, f, g) {
debugger;
let result = oldII(a, b, c, d, e, f, g);
console.log("%c Function: %c md5_ii %c Result: %c %s %c Params: %c %s, %s, %s, %s, %s, %s, %s", color_white_red, color_white_orange, color_white_red, color_white_orange, result, color_white_red, color_white_orange, a, b, c, d, e, f, g)
return result;
};Hook 代码写得比拟死板，相熟 JS 的大佬可本人优化一下，留神注入代码的机会，革除定时器后，断点运行到 y__() 办法后再注入，而后勾销断点，始终下一步，就能够在控制台看到输入的参数了，如下图所示：
与默认参数进行比照，能够发现 md5_hh() 里有两个默认参数被批改了：
默认的 -722521979 改成了 -722521939、76029189 改成了 76029185，本地代码批改一下即可：
/* ==================================
# @Time : 2021-12-23
# @Author : 微信公众号：K 哥爬虫
# @FileName: challenge_7.js
# @Software: PyCharm
# ================================== */
/*
* A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
* Digest Algorithm, as defined in RFC 1321.
* Version 2.2 Copyright (C) Paul Johnston 1999 - 2009
* Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
* Distributed under the BSD License
* See http://pajhome.org.uk/crypt/md5 for more info.
*/
/*
* Configurable variables. You may need to tweak these to be compatible with
* the server-side, but the defaults work in most cases.
*/
var hexcase = 0; /* hex output format. 0 - lowercase; 1 - uppercase */
var b64pad = ""; /* base-64 pad character."=" for strict RFC compliance */
/*
* These are the functions you'll usually want to call
* They take string arguments and return either hex or base-64 encoded strings
*/
function hex_md5(s) {return rstr2hex(rstr_md5(str2rstr_utf8(s))); }
function b64_md5(s) {return rstr2b64(rstr_md5(str2rstr_utf8(s))); }
function any_md5(s, e) {return rstr2any(rstr_md5(str2rstr_utf8(s)), e); }
function hex_hmac_md5(k, d)
{return rstr2hex(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
function b64_hmac_md5(k, d)
{return rstr2b64(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
function any_hmac_md5(k, d, e)
{return rstr2any(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d)), e); }
/*
* Perform a simple self-test to see if the VM is working
*/
function md5_vm_test()
{return hex_md5("abc").toLowerCase() == "900150983cd24fb0d6963f7d28e17f72";}
/*
* Calculate the MD5 of a raw string
*/
function rstr_md5(s)
{return binl2rstr(binl_md5(rstr2binl(s), s.length * 8));
}
/*
* Calculate the HMAC-MD5, of a key and some data (raw strings)
*/
function rstr_hmac_md5(key, data)
{var bkey = rstr2binl(key);
if(bkey.length > 16) bkey = binl_md5(bkey, key.length * 8);
var ipad = Array(16), opad = Array(16);
for(var i = 0; i < 16; i++)
{ipad[i] = bkey[i] ^ 0x36363636;
opad[i] = bkey[i] ^ 0x5C5C5C5C;
}
var hash = binl_md5(ipad.concat(rstr2binl(data)), 512 + data.length * 8);
return binl2rstr(binl_md5(opad.concat(hash), 512 + 128));
}
/*
* Convert a raw string to a hex string
*/
function rstr2hex(input)
{try { hexcase} catch(e) {hexcase=0;}
var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
var output = "";
var x;
for(var i = 0; i < input.length; i++)
{x = input.charCodeAt(i);
output += hex_tab.charAt((x >>> 4) & 0x0F)
+ hex_tab.charAt(x & 0x0F);
}
return output;
}
/*
* Convert a raw string to a base-64 string
*/
function rstr2b64(input)
{try { b64pad} catch(e) {b64pad='';}
var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var output = "";
var len = input.length;
for(var i = 0; i < len; i += 3)
{var triplet = (input.charCodeAt(i) << 16)
| (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
| (i + 2 < len ? input.charCodeAt(i+2) : 0);
for(var j = 0; j < 4; j++)
{if(i * 8 + j * 6 > input.length * 8) output += b64pad;
else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
}
}
return output;
}
/*
* Convert a raw string to an arbitrary string encoding
*/
function rstr2any(input, encoding)
{
var divisor = encoding.length;
var i, j, q, x, quotient;
/* Convert to an array of 16-bit big-endian values, forming the dividend */
var dividend = Array(Math.ceil(input.length / 2));
for(i = 0; i < dividend.length; i++)
{dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
}
/*
* Repeatedly perform a long division. The binary array forms the dividend,
* the length of the encoding is the divisor. Once computed, the quotient
* forms the dividend for the next step. All remainders are stored for later
* use.
*/
var full_length = Math.ceil(input.length * 8 /
(Math.log(encoding.length) / Math.log(2)));
var remainders = Array(full_length);
for(j = 0; j < full_length; j++)
{quotient = Array();
x = 0;
for(i = 0; i < dividend.length; i++)
{x = (x << 16) + dividend[i];
q = Math.floor(x / divisor);
x -= q * divisor;
if(quotient.length > 0 || q > 0)
quotient[quotient.length] = q;
}
remainders[j] = x;
dividend = quotient;
}
/* Convert the remainders to the output string */
var output = "";
for(i = remainders.length - 1; i >= 0; i--)
output += encoding.charAt(remainders[i]);
return output;
}
/*
* Encode a string as utf-8.
* For efficiency, this assumes the input is valid utf-16.
*/
function str2rstr_utf8(input)
{
var output = "";
var i = -1;
var x, y;
while(++i < input.length)
{
/* Decode utf-16 surrogate pairs */
x = input.charCodeAt(i);
y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
{x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
i++;
}
/* Encode output as utf-8 */
if(x <= 0x7F)
output += String.fromCharCode(x);
else if(x <= 0x7FF)
output += String.fromCharCode(0xC0 | ((x >>> 6) & 0x1F),
0x80 | (x & 0x3F));
else if(x <= 0xFFFF)
output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
0x80 | ((x >>> 6) & 0x3F),
0x80 | (x & 0x3F));
else if(x <= 0x1FFFFF)
output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
0x80 | ((x >>> 12) & 0x3F),
0x80 | ((x >>> 6) & 0x3F),
0x80 | (x & 0x3F));
}
return output;
}
/*
* Encode a string as utf-16
*/
function str2rstr_utf16le(input)
{
var output = "";
for(var i = 0; i < input.length; i++)
output += String.fromCharCode(input.charCodeAt(i) & 0xFF,
(input.charCodeAt(i) >>> 8) & 0xFF);
return output;
}
function str2rstr_utf16be(input)
{
var output = "";
for(var i = 0; i < input.length; i++)
output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
input.charCodeAt(i) & 0xFF);
return output;
}
/*
* Convert a raw string to an array of little-endian words
* Characters >255 have their high-byte silently ignored.
*/
function rstr2binl(input)
{var output = Array(input.length >> 2);
for(var i = 0; i < output.length; i++)
output[i] = 0;
for(var i = 0; i < input.length * 8; i += 8)
output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (i%32);
return output;
}
/*
* Convert an array of little-endian words to a string
*/
function binl2rstr(input)
{
var output = "";
for(var i = 0; i < input.length * 32; i += 8)
output += String.fromCharCode((input[i>>5] >>> (i % 32)) & 0xFF);
return output;
}
/*
* Calculate the MD5 of an array of little-endian words, and a bit length.
*/
function binl_md5(x, len)
{
/* append padding */
x[len >> 5] |= 0x80 << ((len) % 32);
x[(((len + 64) >>> 9) << 4) + 14] = len;
var a = 1732584193;
var b = -271733879;
var c = -1732584194;
var d = 271733878;
for(var i = 0; i < x.length; i += 16)
{
var olda = a;
var oldb = b;
var oldc = c;
var oldd = d;
a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
c = md5_ff(c, d, a, b, x[i+ 2], 17, 606105819);
b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
d = md5_ff(d, a, b, c, x[i+ 5], 12, 1200080426);
c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
a = md5_ff(a, b, c, d, x[i+ 8], 7 , 1770035416);
d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
a = md5_ff(a, b, c, d, x[i+12], 7 , 1804603682);
d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
b = md5_ff(b, c, d, a, x[i+15], 22, 1236535329);
a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
c = md5_gg(c, d, a, b, x[i+11], 14, 643717713);
b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
d = md5_gg(d, a, b, c, x[i+10], 9 , 38016083);
c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
a = md5_gg(a, b, c, d, x[i+ 9], 5 , 568446438);
d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
b = md5_gg(b, c, d, a, x[i+ 8], 20, 1163531501);
a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
c = md5_gg(c, d, a, b, x[i+ 7], 14, 1735328473);
b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);
a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
c = md5_hh(c, d, a, b, x[i+11], 16, 1839030562);
b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
d = md5_hh(d, a, b, c, x[i+ 4], 11, 1272893353);
c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
a = md5_hh(a, b, c, d, x[i+13], 4 , 681279174);
d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
// 正文掉的是默认值
// c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521939);
// b = md5_hh(b, c, d, a, x[i+ 6], 23, 76029189);
b = md5_hh(b, c, d, a, x[i+ 6], 23, 76029185);
a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
c = md5_hh(c, d, a, b, x[i+15], 16, 530742520);
b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);
a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
d = md5_ii(d, a, b, c, x[i+ 7], 10, 1126891415);
c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
a = md5_ii(a, b, c, d, x[i+12], 6 , 1700485571);
d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
a = md5_ii(a, b, c, d, x[i+ 8], 6 , 1873313359);
d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
b = md5_ii(b, c, d, a, x[i+13], 21, 1309151649);
a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
c = md5_ii(c, d, a, b, x[i+ 2], 15, 718787259);
b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);
a = safe_add(a, olda);
b = safe_add(b, oldb);
c = safe_add(c, oldc);
d = safe_add(d, oldd);
}
return Array(a, b, c, d);
}
/*
* These functions implement the four basic operations the algorithm uses.
*/
function md5_cmn(q, a, b, x, s, t)
{return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s),b);
}
function md5_ff(a, b, c, d, x, s, t)
{return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t);
}
function md5_gg(a, b, c, d, x, s, t)
{return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t);
}
function md5_hh(a, b, c, d, x, s, t)
{return md5_cmn(b ^ c ^ d, a, b, x, s, t);
}
function md5_ii(a, b, c, d, x, s, t)
{return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
}
/*
* Add integers, wrapping at 2^32. This uses 16-bit operations internally
* to work around bugs in some JS interpreters.
*/
function safe_add(x, y)
{var lsw = (x & 0xFFFF) + (y & 0xFFFF);
var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
return (msw << 16) | (lsw & 0xFFFF);
}
/*
* Bitwise rotate a 32-bit number to the left.
*/
function bit_rol(num, cnt)
{return (num << cnt) | (num >>> (32 - cnt));
}
function getSignature() {return hex_md5(Date.parse(Date()).toString())
}
console.log(getSignature())Python 调用代码：
# ==================================
# --*-- coding: utf-8 --*--
# @Time : 2021-12-23
# @Author : 微信公众号：K 哥爬虫
# @FileName: challenge_7.py
# @Software: PyCharm
# ==================================
import time
import execjs
import requests
challenge_api = "http://spider.wangluozhe.com/challenge/api/7"
headers = {
"Cookie": "Cookie 替换成你的",
"Host": "spider.wangluozhe.com",
"Origin": "http://spider.wangluozhe.com",
"Referer": "http://spider.wangluozhe.com/challenge/7",
"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():
now = str(int(time.time())) + "000"
with open('challenge_7.js', 'r', encoding='utf-8') as f:
wlz_js = execjs.compile(f.read())
# signature = wlz_js.call("getSignature")
signature = wlz_js.call("hex_md5", now)
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()
print(response)
for d in response["data"]:
result += d["value"]
print("后果为:", result)
if __name__ == '__main__':
main() 这里还有一点小细节，如果是 Python 生成工夫戳传入 JS 的 hex_md5 办法的话，要保障工夫戳的最初三位为 0，不然校验通不过，通常的写法是 str(int(time.time() * 1000))，这里要改一下：str(int(time.time())) + "000"，不必 Python 的话，也能够在 JS 里写个办法间接返回 hex_md5(Date.parse(Date()).toString()) 也行。
还有一个问题就是如果你找的 MD5 代码不标准，精确来说是和题目应用的 MD5 代码不太一样的话，有可能本地要改的中央就不止这两处了，所以尽量找一个办法名都一样的 JS，能省不少事儿。
日志断点 / 插桩调试
除了 Hook 以外，咱们还能够通过插桩调试的形式，将整个生成 _signature 的流程、波及到的参数、生成的值，都通过日志的模式打印进去，逆向剖析其逻辑。PS：插桩，即日志断点，鼠标右键抉择 Add logpoint 即可增加一个日志断点，相当于 console.log()，此性能是 Chrome 73 版本新增的。
- Add breakpoint：增加一般断点；
- Add conditional breakpoint：增加条件断点，满足条件才断下；
- Add logpoint：增加日志断点；
- Never pause here：永不在此处断下；
- Add script to ignore list：网站的局部 JS，比方
jquery.min.js之类的库文件，咱们单步调试的时候并不想进入到该文件中，那么能够将此类文件右键增加疏忽掉。
要害的日志断点有以下三处：
- 第 605 行，
arguments为以后传入函数的参数值； - 第 141 行，
___.join(vV_)为以后调用的办法名称，也会输入办法中的参数名称； - 第 591 行，
__V(_, ___(u_), 0, 0, _U__).apply(void 0, y__(v___))为以后办法执行结束的后果。
必定有人会纳闷，如何晓得应该在这三个中央下日志断点呢？答案是只能本人单步、多步调试，找法则、仔细观察，就像交换群里的小小白大佬说的一样，屁股坐烂就行了。当然也不是只有这三个中央能输入对应的信息，有可能其余中央也能够，这就要看你本人调试了。
除了这三个中央的日志断点以外，倡议还能够在第 606 行打个断点，这样每次执行一个办法就断下，本地就能够跟着同步调试，挨个比照传入的参数和失去的后果，不至于一下子输入的货色太多，不不便查找。
第一步，gnature = window.byted_acrawler(window.sign())：
下一步，sign 办法，取工夫戳：
下一步，调用 hex_md5() 办法：
从这里就能够开始本地同步调试了，本地 MD5 下断点调试，能够看到失去的值不一样：
下一步，调用 str2binl() 办法，和本地失去的值是一样的：
下一步，调用 core_md5() 办法，失去的值和本地就不一样了，这里大抵能够确定此办法外部与规范算法有差异了：
下一步，调用 md5_ff() 办法，失去的值是一样的：
以此类推，最终会找到两个不一样的中央，即 md5_hh() 两个默认参数被批改了。
-722521979 被改成了 -722521939：
76029189 被改成了 76029185：
最终提交后果，验证胜利：