一、需求背景
WYY音乐作为国内主流音乐平台，其歌曲资源丰富但下载接口存在多重加密保护。本文将通过Python结合JS逆向技术，解析其核心加密逻辑，实现免费歌曲的下载功能。
二、技术难点分析
1. 接口加密机制
通过抓包分析可知，网易云核心接口使用两次加密：
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第一次：获取播放列表详情（/playlist/detail）
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第二次：获取歌曲下载地址（/song/enhance/player/url/v1）
2. 加密特征
请求参数包含两个关键字段：
params = 'wB86VLegW2dnyHI37+LxTZf4NrKoft+s6kROF0tcWs4LCQlrgaopaFZtak6x8TGsMPoLc1yXe8JEZP7CwGr5mA4/OoKXO/zUf9UYMyVuMMYRdLoKpMkWobbeLcwthG6kKBb5nDhxJOdDmvl+JS709WnXZYMbxZfXjKPgItjMujkjJYYT7LaG53f2mEFScsJI91gLV05T4DQlNRvpC6y6uHjwHBA/3LSrytaRinF7A40='
encSecKey = '71affe85fe12f4dd47ff873aa9c436fcf23ef1c2324020e3c268cdb33a03d7cab99377a066006861c9ca9e4e390d6a68c498415c5e77afd0cb6e6f077c793316587be7609873baab8935d68f1fa22c4287dcfb5b9b72062d1e11c9059b9d637b2820d9bd1c1265d13e8c4c86414a788b3db595c1fa3931a0fba02dbb9be93222'
三、逆向工程实现
1. 加密逻辑定位
通过浏览器开发者工具分析，定位到核心加密函数位于core_b7113131e0c3d9361b7b149f7ab7939f.js?b7113131e0c3d9361b7b149f7ab7939f.js中：
然后再根据参数关键词encSecKey在对应的js文件中搜索，进而分析通过js实现的方法
将所有涉及到的js文件中的function复制带自己电脑上的js文件中
完整js代码如下 后续可以将这份代码复制在本机命名为jm.js：
var data_01 = '00e0b509f6259df8642dbc35662901477df22677ec152b5ff68ace615bb7b725152b3ab17a876aea8a5aa76d2e417629ec4ee341f56135fccf695280104e0312ecbda92557c93870114af6c9d05c4f7f0c3685b7a46bee255932575cce10b424d813cfe4875d3e82047b97ddef52741d546b8e289dc6935b3ece0462db0a22b8e7'
const CryptoJS = require('crypto-js');
var maxDigits, ZERO_ARRAY, bigZero, bigOne, dpl10, lr10, hexatrigesimalToChar, hexToChar, highBitMasks, lowBitMasks, biRadixBase = 2, biRadixBits = 16, bitsPerDigit = biRadixBits, biRadix = 65536, biHalfRadix = biRadix >>> 1, biRadixSquared = biRadix * biRadix, maxDigitVal = biRadix - 1, maxInteger = 9999999999999998;
setMaxDigits(20),
dpl10 = 15,
lr10 = biFromNumber(1e15),
hexatrigesimalToChar = new Array("0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"),
hexToChar = new Array("0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"),
highBitMasks = new Array(0,32768,49152,57344,61440,63488,64512,65024,65280,65408,65472,65504,65520,65528,65532,65534,65535),
lowBitMasks = new Array(0,1,3,7,15,31,63,127,255,511,1023,2047,4095,8191,16383,32767,65535);
function RSAKeyPair(a, b, c) {
this.e = biFromHex(a),
this.d = biFromHex(b),
this.m = biFromHex(c),
this.chunkSize = 2 * biHighIndex(this.m),
this.radix = 16,
this.barrett = new BarrettMu(this.m)
}
function twoDigit(a) {
return (10 > a ? "0" : "") + String(a)
}
function encryptedString(a, b) {
for (var f, g, h, i, j, k, l, c = new Array, d = b.length, e = 0; d > e; )
c[e] = b.charCodeAt(e),
e++;
for (; 0 != c.length % a.chunkSize; )
c[e++] = 0;
for (f = c.length,
g = "",
e = 0; f > e; e += a.chunkSize) {
for (j = new BigInt,
h = 0,
i = e; i < e + a.chunkSize; ++h)
j.digits[h] = c[i++],
j.digits[h] += c[i++] << 8;
k = a.barrett.powMod(j, a.e),
l = 16 == a.radix ? biToHex(k) : biToString(k, a.radix),
g += l + " "
}
return g.substring(0, g.length - 1)
}
function decryptedString(a, b) {
var e, f, g, h, c = b.split(" "), d = "";
for (e = 0; e < c.length; ++e)
for (h = 16 == a.radix ? biFromHex(c[e]) : biFromString(c[e], a.radix),
g = a.barrett.powMod(h, a.d),
f = 0; f <= biHighIndex(g); ++f)
d += String.fromCharCode(255 & g.digits[f], g.digits[f] >> 8);
return 0 == d.charCodeAt(d.length - 1) && (d = d.substring(0, d.length - 1)),
d
}
function setMaxDigits(a) {
maxDigits = a,
ZERO_ARRAY = new Array(maxDigits);
for (var b = 0; b < ZERO_ARRAY.length; b++)
ZERO_ARRAY[b] = 0;
bigZero = new BigInt,
bigOne = new BigInt,
bigOne.digits[0] = 1
}
function BigInt(a) {
this.digits = "boolean" == typeof a && 1 == a ? null : ZERO_ARRAY.slice(0),
this.isNeg = !1
}
function biFromDecimal(a) {
for (var d, e, f, b = "-"
