百度翻译爬虫js逆向解析
今天来看一下百度翻译js逆向解析。
问题
在翻译的接口输入：汉语中文，https://fanyi.baidu.com/?aldtype=16047#zh/en/汉语中文
找到它请求的接口：https://fanyi.baidu.com/v2transapi ，发现是post请求，携带的参数为
from: zh
to: en
query: 汉语中文
simple_means_flag: 3
sign: 523457.204784
token: 261d93745136045b7ea6a1badc54a075
经过测试发现，只有sign值在变化，影响结果
分析
全局搜索接口中的关键字符串v2transapi，发现只有一个js，https://fanyi.bdstatic.com/static/translation/pkg/index_9b62d56.js:formatted ，继续搜索v2transapi，如下图：
发现了接口url的拼接参数，sign:m(a)，这一行打断点调试，会定位到如下js当中的内容：
分析这一段js代码，发现这一段就是我们所需要的，如果会前端的知识相信会比较好理解，不然就对这一部分js进行断点调试，慢慢分析查看参数传递过程，会发现很多代码都是进行判断检测，整理出关键的代码，就是上图的方框里的内容。关键部分如下：
# u = null !== i ? i : (i = window[l] || "") || "";下面定义了var i=null;
# null !== i 为假，执行(i = window[l] || "")，结果为320305.131321201
# 这里多次运行发现window[1]是一个固定值：320305.131321201,(直接替换，调用js就可以得到结果了)，
# 简化成u= false ? : null : 320305.131321201 || "",最后u=320305.131321201是一个固定值
解决
将window[l]替换成320305.131321201，var i=null;调换一下位置，稍微整理一下js，如下：
jsCode = """
function a(r) {
if (Array.isArray(r)) {
for (var o = 0, t = Array(r.length); o < r.length; o++)
t[o] = r[o];
return t
}
return Array.from(r)
}
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 = null;
function e(r) {
var t = r.length;
t > 30 && (r = "" + r.substr(0, 10) + r.substr(Math.floor(t / 2) - 5, 10) + r.substr(-10, 10))
var u = void 0, l = "" + String.fromCharCode(103) + String.fromCharCode(116) + String.fromCharCode(107);
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)
}
"""
import execjs
query = '汉语中文'
sign = execjs.compile(jsCode).call("e", query)
print(sign)
得到的sign就是正确的结果了，每次查询的query不同，返回的sign不同，而同一个query，返回的sign始终相同。
将sign传入下面的代码(代码中的请求参数都必须要，否则报错)，就可以返回正确的翻译内容：
import requests
import json
data = {
"from": "zh",
"to": "en",
"query":query,
"transtype": "translang",
"simple_means_flag": "3",
"sign": sign,
"token": "261d93745136045b7ea6a1badc54a075",
}
headers = {
'Accept': '*/*',
'Accept-Encoding': 'gzip, deflate, br',
'Accept-Language': 'zh-CN,zh;q=0.9',
'Connection': 'keep-alive',
'Content-Length': '154',
'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8',
'Cookie': 'BAIDUID=BADB5E5D72667C5F54A34848245C74AB:FG=1; BIDUPSID=BADB5E5D72667C5F54A34848245C74AB; PSTM=1534988617; H_WISE_SIDS=124614_125822_108269_124694_125945_114745_123552_125629_120162_125735_118894_118867_118845_118820_118788_107311_125006_124978_117428_125776_125652_124636_124897_124939_125487_125171_125289_125710_125285_124938_124683_124030_110085_123289_125645_125428_125875; REALTIME_TRANS_SWITCH=1; FANYI_WORD_SWITCH=1; HISTORY_SWITCH=1; SOUND_SPD_SWITCH=1; SOUND_PREFER_SWITCH=1; BDUSS=0N6UHl4VTVQR1k2d0k1YWtMRmRRaTJhLWFpQk1mLWZwS3YxU01UTW0tMEtNaEpjQVFBQUFBJCQAAAAAAAAAAAEAAACrlRIPNDM0ODkwOTc0AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAql6lsKpepbS; Hm_lvt_64ecd82404c51e03dc91cb9e8c025574=1542288873,1542333802,1542365440,1542422410; __cfduid=dde3763f9db2ea63b180aa1372d14e3921542882903; BDSFRCVID=LNuOJeC62mNCkaT90LMd--Y9EeTt9t7TH6aItwTAQU9bjkQNDx7JEG0PfU8g0KubJmOPogKKKgOTHICF_2uxOjjg8UtVJeC6EG0P3J; H_BDCLCKID_SF=tR-tVC0-fCI3fP36q4co-4FjbqOH54cXHDOH0Kvzt-55OR5Jj65NW-FtMGtf2j3kyCT-hInH-RF5jDn-3MA--fF1hmcayhjMXbvXQp-2KhTCsq0x0-6le-bQypoa2b-HBIOMahvc5h7xOhIC05C-jTvBDG_eq-JQ2C7WsJjs24ThD6rnhPF3K4rbKP6-3MJO3b7zon6lJbrSSpO_5n3V3tkEKh6tb6oP-N7CohFLtC0BhK0Gj6Rjh-40b2TJK4625CoJsJOOaC7tqR7zKPnhK4t8HfJfhtJfHJue_II5JjuKhI-wjTD_D6J3eHtqqh5gW57Z0lOnMp05jt3uh6J_hKurXpKJ0JQ2aCDfhC5RLKOSVIO_e6LbejOWjHDs5-7ybCPXLn58Kb5_f5rnhPF3yMvDKP6-3MJO3b7JbpTvJbrSOUob-jrl5f63247XtbTwKRnlohFLtD8KMI-GjjRMK4_SMUoHetrK-D5XQbC8Kb7VbTC4LfnkbfJBD4-jXJJC2JvXQpOy5R5lfM7NyUOO5fI7yajK25KHbe5h2h5v3fOASIO63bbpQT8rbfDOK5Oib4j7htOnab3vOpvTXpO1yftzBN5thURB2DkO-4bCWJ5TMl5jDh05y6TXjH-ttTLDJn3fL-082R6oDn8k-PnVePF3LtnZKxtqtDDOBDJ7QI3lDbk6557ZbbDqhRJ8t4TnWncKWho1bIb_MR5cK65IhPrb2HJ405OT2j-O0KJcbRo0Hpb4hPJvyUPsXnO7BxJlXbrtXp7_2J0WStbKy4oTjxL1Db0eBjIHtnFJVI05fCvKeJbYK4oj5KCyMfca5C6JKCOa3RA8Kb7VbpR85fnkbfJBDxcw3-nKQnKj2p6eH66Zbq5N3b8B55-7yajKBR3fQg6I-CTt2JvG8lb9jU6pQT8rbR_OK5OibCrZWl7xab3vOpvTXpO1yftzBN5thURB2DkO-4bCWJ5TMl5jDh05y6ISKx-_J5te3f; MCITY=-%3A; H_PS_PSSID=1438_21081_18559_28019_26350; BDORZ=B490B5EBF6F3CD402E515D22BCDA1598; delPer=0; PSINO=5; locale=zh; Hm_lpvt_64ecd82404c51e03dc91cb9e8c025574=1544166294; from_lang_often=%5B%7B%22value%22%3A%22dan%22%2C%22text%22%3A%22%u4E39%u9EA6%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; to_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',
'Host': 'fanyi.baidu.com',
'Origin': 'https://fanyi.baidu.com',
'Referer': 'https://fanyi.baidu.com/?aldtype=16047',
'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36',
'X-Requested-With': 'XMLHttpRequest'
}
url = 'https://fanyi.baidu.com/v2transapi'
res = requests.post(url=url, headers=headers, data=data)
result = json.loads(res.text).get("trans_result").get('data')[0]
item = dict()
item[source] = result.get('dst')
print(item) #{'汉语中文': 'Chinese language'}
简书上有网友分析了js，获得的sign也都是一样的，如下：
# signCode = 'function a(r,o){for(var t=0;t="a"?a.charCodeAt(0)-87:Number(a),a="+"===o.charAt(t+1)?r>>>a:r<30&&(r=""+r.substr(0,10)+r.substr(Math.floor(o/2)-5,10)+r.substr(-10,10));var t=void 0,t=null!==C?C:(C=_gtk||"")||"";for(var e=t.split("."),h=Number(e[0])||0,i=Number(e[1])||0,d=[],f=0,g=0;gm?d[f++]=m:(2048>m?d[f++]=m>>6|192:(55296===(64512&m)&&g+1>18|240,d[f++]=m>>12&63|128):d[f++]=m>>12|224,d[f++]=m>>6&63|128),d[f++]=63&m|128)}for(var S=h,u="+-a^+6",l="+-3^+b+-f",s=0;sS&&(S=(2147483647&S)+2147483648),S%=1e6,S.toString()+"."+(S^h)}'
# import js2py
# call = js2py.eval_js(signCode)
# sign = call("汉语中文",'320305.131321201')
# print(sign)
总结
1.过程中遇到返回的997，998等参数都是sign值不对造成的。
2.for循环体中的位运算依然是解析难点，不建议解析出来，能调用得出正确结果最好。
有问题，欢迎留言交流！