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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 timeimport execjsimport requestschallenge_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 signaturedef 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：