一、分析请求参数

打开地址：

https://fanyi.baidu.com/
打开Chrome调试工具，然后随意输入一段文字，查看抓包结果。

• post请求
  • Form data 参数
    

如上图所示，Form Date中只有两项是会变化的：

1. query：我们要翻译的内容
2. sign：本文的BOSS出现了，一串意义不明的浮点数值。

• token是不变的，先给查找出来，全局搜索
• 全局搜索发现 token 的值
• token：13508e550366f3004701d561721e12bd

至此，我们便可以初步构造出表单date了以及URL& headers，代码见下：

import requests
import json
import jsonpath
import execjsurl = "https://fanyi.baidu.com/v2transapi"
headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0","Cookie": "BAIDUID=C3A44BD2BCAA852D78454F118D907CA2:FG=1; BIDUPSID=C3A44BD2BCAA852D78454F118D907CA2; PSTM=1558237711; delPer=0; H_PS_PSSID=1455_21097_29064_28519_28769_28723_28963_28838_28585_29071; PSINO=7; locale=zh; to_lang_often=%5B%7B%22value%22%3A%22en%22%2C%22text%22%3A%22%u82F1%u8BED%22%7D%2C%7B%22value%22%3A%22zh%22%2C%22text%22%3A%22%u4E2D%u6587%22%7D%5D; REALTIME_TRANS_SWITCH=1; FANYI_WORD_SWITCH=1; HISTORY_SWITCH=1; SOUND_SPD_SWITCH=1; SOUND_PREFER_SWITCH=1; Hm_lvt_64ecd82404c51e03dc91cb9e8c025574=1558237732; Hm_lpvt_64ecd82404c51e03dc91cb9e8c025574=1558237732; from_lang_often=%5B%7B%22value%22%3A%22zh%22%2C%22text%22%3A%22%u4E2D%u6587%22%7D%2C%7B%22value%22%3A%22en%22%2C%22text%22%3A%22%u82F1%u8BED%22%7D%5D; CHINA_PINYIN_SWITCH=0; DOUBLE_LANG_SWITCH=0"
}
data = {"from": "en","to": "zh","query": "",  # query 即我们要翻译的的内容"transtype": "translang","simple_means_flag": "3","sign": "",  # sign 是变化的需要我们执行js代码得到"token": "13508e550366f3004701d561721e12bd"  # token没有变化
}

二、分析sign —— JS逆向

• 全局搜索 sign

打断点-跟踪函数

• 可以看出来这是应该ajax请求，p里面的参数就是我们要找的参数。

• 在Sourth中找到刚才全局搜索到的js文件，然后搜索界面、打断点

• 打断点后刷新页面，输入字符后页面出现

我们发现 sign是通过m()函数生成的

• 然后鼠标放在m上面悬停一下会出现一个跳转，点击可以跳转到他的函数那里。

• 跳转过后我们看到m函数是

扣代码–生成sign

复制上图中的JS代码，我们新建一个JS文件，命名为： baidu_translata_js.js

js文件最初的模样O(∩_∩)O

function e(r) {var o = r.match(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g);if (null === o) {var t = r.length;t > 30 && (r = "" + r.substr(0, 10) + r.substr(Math.floor(t / 2) - 5, 10) + r.substr(-10, 10))} else {for (var e = r.split(/[\uD800-\uDBFF][\uDC00-\uDFFF]/), C = 0, h = e.length, f = []; h > C; C++)"" !== e[C] && f.push.apply(f, a(e[C].split(""))),C !== h - 1 && f.push(o[C]);var g = f.length;g > 30 && (r = f.slice(0, 10).join("") + f.slice(Math.floor(g / 2) - 5, Math.floor(g / 2) + 5).join("") + f.slice(-10).join(""))}var u = void 0, l = "" + String.fromCharCode(103) + String.fromCharCode(116) + String.fromCharCode(107);u = null !== i ? i : (i = window[l] || "") || "";// var u = void 0, i = null;// u = null !== i ? i : (i = "320305.131321201" || "") || "";for (var d = u.split("."), m = Number(d[0]) || 0, s = Number(d[1]) || 0, S = [], c = 0, v = 0; v < r.length; v++) {var A = r.charCodeAt(v);128 > A ? S[c++] = A : (2048 > A ? S[c++] = A >> 6 | 192 : (55296 === (64512 & A) && v + 1 < r.length && 56320 === (64512 & r.charCodeAt(v + 1)) ? (A = 65536 + ((1023 & A) << 10) + (1023 & r.charCodeAt(++v)),S[c++] = A >> 18 | 240,S[c++] = A >> 12 & 63 | 128) : S[c++] = A >> 12 | 224,S[c++] = A >> 6 & 63 | 128),S[c++] = 63 & A | 128)}for (var p = m, F = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(97) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(54)), D = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(51) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(98)) + ("" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(102)), b = 0; b < S.length; b++)p += S[b],p = n(p, F);return p = n(p, D),p ^= s,0 > p && (p = (2147483647 & p) + 2147483648),p %= 1e6,p.toString() + "." + (p ^ m)}

然后通过编译器（可以执行js的编译器）执行该文件，也可以通过Python中的 PyExecJS 模块执行 js代码

这里是通过python执行js

import execjsquery = 'Hello spider'
with open('baidu_translate_js.js', 'r', encoding='utf-8') as f:ctx = execjs.compile(f.read())sign = ctx.call('e', query)
print(sign)

• 问题来了（i未被定义）

execjs._exceptions.ProgramError: ReferenceError: i is not defined

• 我们继续在浏览器中加断点调试 查看 i 值 是怎么生成的

我们在 6819 行中发现i u = null !== i ? i : (i = window[l] || "") || ""; i是通过浏览器的window生成的，我们不是通过浏览器执行js的话，生成不了这个i，不过经过过我们多次尝试就可以发现这里的i值是不变的，所有很好操作。声明一下 i 就可以了

我们愉快的添加了下面这一行代码：

var i = "320305.131321201"

执行结果

紧接着我们再尝试执行函数，又出现错误提示n未定义。故技重施，找到n，发现是一个函数，进入到函数把整个代码扣下来再复制到js代码最前面。

我们再次运行，已经生成了sign值，

三 至此，我们来写代码吧

1 扣好的JS代码
baidu_translate_js.js

function n(r, o) {for (var t = 0; t < o.length - 2; t += 3) {var a = o.charAt(t + 2);a = a >= "a" ? a.charCodeAt(0) - 87 : Number(a),a = "+" === o.charAt(t + 1) ? r >>> a : r << a,r = "+" === o.charAt(t) ? r + a & 4294967295 : r ^ a}return r}var i = "320305.131321201"
function e(r) {var o = r.match(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g);if (null === o) {var t = r.length;t > 30 && (r = "" + r.substr(0, 10) + r.substr(Math.floor(t / 2) - 5, 10) + r.substr(-10, 10))} else {for (var e = r.split(/[\uD800-\uDBFF][\uDC00-\uDFFF]/), C = 0, h = e.length, f = []; h > C; C++)"" !== e[C] && f.push.apply(f, a(e[C].split(""))),C !== h - 1 && f.push(o[C]);var g = f.length;g > 30 && (r = f.slice(0, 10).join("") + f.slice(Math.floor(g / 2) - 5, Math.floor(g / 2) + 5).join("") + f.slice(-10).join(""))}var u = void 0, l = "" + String.fromCharCode(103) + String.fromCharCode(116) + String.fromCharCode(107);u = null !== i ? i : (i = window[l] || "") || "";for (var d = u.split("."), m = Number(d[0]) || 0, s = Number(d[1]) || 0, S = [], c = 0, v = 0; v < r.length; v++) {var A = r.charCodeAt(v);128 > A ? S[c++] = A : (2048 > A ? S[c++] = A >> 6 | 192 : (55296 === (64512 & A) && v + 1 < r.length && 56320 === (64512 & r.charCodeAt(v + 1)) ? (A = 65536 + ((1023 & A) << 10) + (1023 & r.charCodeAt(++v)),S[c++] = A >> 18 | 240,S[c++] = A >> 12 & 63 | 128) : S[c++] = A >> 12 | 224,S[c++] = A >> 6 & 63 | 128),S[c++] = 63 & A | 128)}for (var p = m, F = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(97) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(54)), D = "" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(51) + ("" + String.fromCharCode(94) + String.fromCharCode(43) + String.fromCharCode(98)) + ("" + String.fromCharCode(43) + String.fromCharCode(45) + String.fromCharCode(102)), b = 0; b < S.length; b++)p += S[b],p = n(p, F);return p = n(p, D),p ^= s,0 > p && (p = (2147483647 & p) + 2147483648),p %= 1e6,p.toString() + "." + (p ^ m)}

2 执行js的python代码

import execjsquery = 'Hello spider'
with open('baidu_translate_js.js', 'r', encoding='utf-8') as f:ctx = execjs.compile(f.read())sign = ctx.call('e', query)
print(sign)

3 完成爬虫，解析数据

数据直接转为json数据，（response.json()）
很好解析

结构清晰，很好获取数据
response[‘trans_result’][‘data’][0][‘dst’]

四、封装优化——面向对象编程

#!/usr/bin/env python
# encoding: utf-8
# @software: PyCharm
# @time: 2019/5/22 9:26
# @author: Paulson●Wier
# @file: baidu_translate.py
# @desc:
import execjs
import requestsclass BaiduTranslateJS(object):def __init__(self, query):""":param query: 待翻译的内容cookie 值 可能会影响到翻译结果，可以将未登陆情况下百度翻译的cookie填写。"""self.query = queryself.url = "https://fanyi.baidu.com/v2transapi"self.headers = {"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0","Cookie": "BAIDUID=AFB6E3FB47D3EEA8C525D02E728E0991:FG=1; BIDUPSID=AFB6E3FB47D3EEA8C525D02E728E0991; PSTM=1556177968; REALTIME_TRANS_SWITCH=1; FANYI_WORD_SWITCH=1; HISTORY_SWITCH=1; SOUND_SPD_SWITCH=1; SOUND_PREFER_SWITCH=1; MCITY=-131%3A; Hm_lvt_64ecd82404c51e03dc91cb9e8c025574=1556507678,1557287607,1557714510,1557972796; BDSFRCVID=xr-sJeCCxG3twro9YX2saOEfCZPT14fNd2s33J; H_BDCLCKID_SF=tR3fL-08abrqqbRGKITjhPrM2hKLbMT-027OKKO2b-oobfTyDRbHXULELn6TLT_J5eobot8bthF0HPonHj85j6bQ3J; PSINO=2; delPer=0; H_PS_PSSID=1450_28937_21095_18560_29064_28518_29098_28722_28963_28836_28584_26350; locale=zh; yjs_js_security_passport=5b9f340d92cf7400bd5ba82b49a65bc0520935cc_1558490261_js; Hm_lpvt_64ecd82404c51e03dc91cb9e8c025574=1558493551; to_lang_often=%5B%7B%22value%22%3A%22jp%22%2C%22text%22%3A%22%u65E5%u8BED%22%7D%2C%7B%22value%22%3A%22en%22%2C%22text%22%3A%22%u82F1%u8BED%22%7D%2C%7B%22value%22%3A%22zh%22%2C%22text%22%3A%22%u4E2D%u6587%22%7D%5D; from_lang_often=%5B%7B%22value%22%3A%22jp%22%2C%22text%22%3A%22%u65E5%u8BED%22%7D%2C%7B%22value%22%3A%22zh%22%2C%22text%22%3A%22%u4E2D%u6587%22%7D%2C%7B%22value%22%3A%22en%22%2C%22text%22%3A%22%u82F1%u8BED%22%7D%5D"}self.data = {"from": "en","to": "zh","query": self.query,  # query 即我们要翻译的的内容"transtype": "translang","simple_means_flag": "3","sign": "",  # sign 是变化的需要我们执行js代码得到"token": "13508e550366f3004701d561721e12bd"  # token没有变化}def structure_form(self):"""读取js文件执行js代码得到我们苦求的sign值构造新的表单:return:"""with open('baidu_translate_js.js', 'r', encoding='utf-8') as f:ctx = execjs.compile(f.read())sign = ctx.call('e', self.query)# print(sign)# sign成功获取，写入dateself.data['sign'] = signdef get_response(self):"""通过构造的新的表单数据，访问api，获取翻译内容:return: 翻译结果"""self.structure_form()response = requests.post(self.url, headers=self.headers, data=self.data).json()# print(response)r = response['trans_result']['data'][0]['dst']return rif __name__ == '__main__':baidu_translate_spider = BaiduTranslateJS('this is a test')result = baidu_translate_spider.get_response()print(result)print(BaiduTranslateJS('this').get_response())print(BaiduTranslateJS('is').get_response())print(BaiduTranslateJS('my').get_response())print(BaiduTranslateJS('love').get_response())

结果

五、总结

百度翻译的JS逆向过程至此就结束了，分析流程和步骤相当清晰，如果帮助到了你，请点个赞呗。