【··案例··】【19.某易云音乐】请求逆向解析，数据算法解密（详细笔记）

某易云音乐

1. 定位爬取的数据包

以当前歌曲为例，可以看到当点击播放的时候会出现很多请求的接口，接下来一个接口一个接口的看，直到发现和歌曲下载有关的那一个为止。

最后定位到了/weapi/song/enhance/player/url/v1?csrf_token=这个接口。并且接口返回值里有一个URL为http://m801.music.126.net/20231116170739/11fc00fb99b8cc89ffd1e1bad7201477/jdyyaac/obj/w5rDlsOJwrLDjj7CmsOj/31248364361/113a/77e3/a0a5/c2a90b87a91199babf8ea42f08a0d8b8.m4a，这是一个m4a文件。其实这就是一个音频文件，类似于之前常见的mp3格式等等。

• M4A 是一种音频文件格式，它是 MPEG-4 Part 14 标准的一部分。M4A 文件通常包含以 Advanced Audio Coding (AAC) 编码的音频数据，但它也可以包含其他音频编码类型。这个格式的名称 “M4A” 是由 Apple 公司引入的，用于标识其在 iTunes 中使用的音频文件。
• M4A 文件通常具有较高的音频质量，并且相对于其他一些音频格式，文件大小较小。它是一种无损音频格式，可以提供高质量的音频体验。由于其高效的压缩算法，M4A 文件经常用于存储音乐、音效和其他类型的音频内容。
• 尽管 M4A 格式在音质和文件大小上有一些优势，但它可能不如其他格式如 MP3 在广泛的多平台兼容性上好。不过，许多现代设备和音频播放器都支持 M4A 格式，特别是在苹果的生态系统中，它是一种常见的音频文件格式。

接下来可以请求一下这个链接的文件是否能播放，如果能播放就是我们的目标

2. 接口分析

前文中找到了获取文件的接口，那么这个接口是如何工作的呢。

查看请求头

可以看到并没有加密的参数，唯一有可能营销的就是 Cookie，但是可以试试先不带 Cookies，其他的 UA 和 Referer 最好先带上。

查看参数

参数有两个，都是加密后的，所以重点就是这两个参数。

3. 获取加密方式

定位功能函数

定位加密行数有很多种方式，这里以全局搜索为例，可以搜索 encSecKey 这一的特殊字段，大概率能够搜到。其实这个关键字还是搜索到了很多条记录，但是可以都打上断点用排除的方式进行判断，最终定位到了core_xxx.js这个文件。

可以看到有两个字段parms和encSecKey，都是密文，但是不确定是不是我们要的结果。所以可以等这次执行完和浏览器上的值对比一下。需要注意前面有个x4b的值是一个URL，得确保这个URL是刚才查到的那个接口，否则就走错路了。

等请求跑完，对比后确认这个就是我们要找的加密函数。所以关键点就在下面的代码中:

var bVg5l = window.asrsea(JSON.stringify(i3x), bsk0x(["流泪", "强"]), bsk0x(WH9y.md), bsk0x(["爱心", "女孩", "惊恐", "大笑"]));

函数中的第一个参数是由歌曲id拼接的，其他的参数有的是固定值，有的不确定，可以检查一下。


d函数也调用了当前作用域下的其他几个函数。接下来就可以使用JS的方式进行逆向了。

方式1. 逐个补函数

主要思想就是用到哪个函数就复制哪个函数，优点就是减少了代码量和减少思考；缺点就是得一个个补，耗时较长。

首先围绕着d函数 进行逐个填补

const CryptoJS = require("crypto-js")  // 安装nodejs库 npm install crypto-js

function a(a) {
    var d, e, b = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789", c = "";
    for (d = 0; a > d; d += 1) e = Math.random() * b.length, e = Math.floor(e), c += b.charAt(e);
    return c
}

function b(a, b) {
    var c = CryptoJS.enc.Utf8.parse(b), d = CryptoJS.enc.Utf8.parse("0102030405060708"), e = CryptoJS.enc.Utf8.parse(a),
        f = CryptoJS.AES.encrypt(e, c, {
            iv: d, mode: CryptoJS.mode.CBC
        });
    return f.toString()
}

function c(a, b, c) {
    var d, e;
    return setMaxDigits(131), d = new RSAKeyPair(b, "", c), e = encryptedString(d, a)
}

function d(d, e, f, g) {
    var h = {}, i = a(16);
    return h.encText = b(d, g), h.encText = b(h.encText, i), h.encSecKey = c(i, e, f), h
}

function e(a, b, d, e) {
    var f = {};
    return f.encText = c(a + e, b, d), f
}

接下来就运行当前js文件，报错缺哪个函数就补哪个函数。最后代码如下：

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 = "-" == a.charAt(0), c = b ? 1 : 0; c < a.length && "0" == a.charAt(c);)
        ++c;
    if (c == a.length)
        d = new BigInt;
    else {
        for (e = a.length - c,
                 f = e % dpl10,
             0 == f && (f = dpl10),
                 d = biFromNumber(Number(a.substr(c, f))),
                 c += f; c < a.length;)
            d = biAdd(biMultiply(d, lr10), biFromNumber(Number(a.substr(c, dpl10)))),
                c += dpl10;
        d.isNeg = b
    }
    return d
}

function biCopy(a) {
    var b = new BigInt(!0);
    return b.digits = a.digits.slice(0),
        b.isNeg = a.isNeg,
        b
}

function biFromNumber(a) {
    var c, b = new BigInt;
    for (b.isNeg = 0 > a,
             a = Math.abs(a),
             c = 0; a > 0;)
        b.digits[c++] = a & maxDigitVal,
            a >>= biRadixBits;
    return b
}

function reverseStr(a) {
    var c, b = "";
    for (c = a.length - 1; c > -1; --c)
        b += a.charAt(c);
    return b
}

function biToString(a, b) {
    var d, e, c = new BigInt;
    for (c.digits[0] = b,
             d = biDivideModulo(a, c),
             e = hexatrigesimalToChar[d[1].digits[0]]; 1 == biCompare(d[0], bigZero);)
        d = biDivideModulo(d[0], c),
            digit = d[1].digits[0],
            e += hexatrigesimalToChar[d[1].digits[0]];
    return (a.isNeg ? "-" : "") + reverseStr(e)
}

function biToDecimal(a) {
    var c, d, b = new BigInt;
    for (b.digits[0] = 10,
             c = biDivideModulo(a, b),
             d = String(c[1].digits[0]); 1 == biCompare(c[0], bigZero);)
        c = biDivideModulo(c[0], b),
            d += String(c[1].digits[0]);
    return (a.isNeg ? "-" : "") + reverseStr(d)
}

function digitToHex(a) {
    var b = 15
        , c = "";
    for (i = 0; 4 > i; ++i)
        c += hexToChar[a & b],
            a >>>= 4;
    return reverseStr(c)
}

function biToHex(a) {
    var d, b = "";
    for (biHighIndex(a),
             d = biHighIndex(a); d > -1; --d)
        b += digitToHex(a.digits[d]);
    return b
}

function charToHex(a) {
    var h, b = 48, c = b + 9, d = 97, e = d + 25, f = 65, g = 90;
    return h = a >= b && c >= a ? a - b : a >= f && g >= a ? 10 + a - f : a >= d && e >= a ? 10 + a - d : 0
}

function hexToDigit(a) {
    var d, b = 0, c = Math.min(a.length, 4);
    for (d = 0; c > d; ++d)
        b <<= 4,
            b |= charToHex(a.charCodeAt(d));
    return b
}

function biFromHex(a) {
    var d, e, b = new BigInt, c = a.length;
    for (d = c,
             e = 0; d > 0; d -= 4,
             ++e)
        b.digits[e] = hexToDigit(a.substr(Math.max(d - 4, 0), Math.min(d, 4)));
    return b
}

function biFromString(a, b) {
    var g, h, i, j, c = "-" == a.charAt(0), d = c ? 1 : 0, e = new BigInt, f = new BigInt;
    for (f.digits[0] = 1,
             g = a.length - 1; g >= d; g--)
        h = a.charCodeAt(g),
            i = charToHex(h),
            j = biMultiplyDigit(f, i),
            e = biAdd(e, j),
            f = biMultiplyDigit(f, b);
    return e.isNeg = c,
        e
}

function biDump(a) {
    return (a.isNeg ? "-" : "") + a.digits.join(" ")
}

function biAdd(a, b) {
    var c, d, e, f;
    if (a.isNeg != b.isNeg)
        b.isNeg = !b.isNeg,
            c = biSubtract(a, b),
            b.isNeg = !b.isNeg;
    else {
        for (c = new BigInt,
                 d = 0,
                 f = 0; f < a.digits.length; ++f)
            e = a.digits[f] + b.digits[f] + d,
                c.digits[f] = 65535 & e,
                d = Number(e >= biRadix);
        c.isNeg = a.isNeg
    }
    return c
}

function biSubtract(a, b) {
    var c, d, e, f;
    if (a.isNeg != b.isNeg)
        b.isNeg = !b.isNeg,
            c = biAdd(a, b),
            b.isNeg = !b.isNeg;
    else {
        for (c = new BigInt,
                 e = 0,
                 f = 0; f < a.digits.length; ++f)
            d = a.digits[f] - b.digits[f] + e,
                c.digits[f] = 65535 & d,
            c.digits[f] < 0 && (c.digits[f] += biRadix),
                e = 0 - Number(0 > d);
        if (-1 == e) {
            for (e = 0,
                     f = 0; f < a.digits.length; ++f)
                d = 0 - c.digits[f] + e,
                    c.digits[f] = 65535 & d,
                c.digits[f] < 0 && (c.digits[f] += biRadix),
                    e = 0 - Number(0 > d);
            c.isNeg = !a.isNeg
        } else
            c.isNeg = a.isNeg
    }
    return c
}

function biHighIndex(a) {
    for (var b = a.digits.length - 1; b > 0 && 0 == a.digits[b];)
        --b;
    return b
}

function biNumBits(a) {
    var e, b = biHighIndex(a), c = a.digits[b], d = (b + 1) * bitsPerDigit;
    for (e = d; e > d - bitsPerDigit && 0 == (32768 & c); --e)
        c <<= 1;
    return e
}

function biMultiply(a, b) {
    var d, h, i, k, c = new BigInt, e = biHighIndex(a), f = biHighIndex(b);
    for (k = 0; f >= k; ++k) {
        for (d = 0,
                 i = k,
                 j = 0; e >= j; ++j,
                 ++i)
            h = c.digits[i] + a.digits[j] * b.digits[k] + d,
                c.digits[i] = h & maxDigitVal,
                d = h >>> biRadixBits;
        c.digits[k + e + 1] = d
    }
    return c.isNeg = a.isNeg != b.isNeg,
        c
}

function biMultiplyDigit(a, b) {
    var c, d, e, f;
    for (result = new BigInt,
             c = biHighIndex(a),
             d = 0,
             f = 0; c >= f; ++f)
        e = result.digits[f] + a.digits[f] * b + d,
            result.digits[f] = e & maxDigitVal,
            d = e >>> biRadixBits;
    return result.digits[1 + c] = d,
        result
}

function arrayCopy(a, b, c, d, e) {
    var g, h, f = Math.min(b + e, a.length);
    for (g = b,
             h = d; f > g; ++g,
             ++h)
        c[h] = a[g]
}

function biShiftLeft(a, b) {
    var e, f, g, h, c = Math.floor(b / bitsPerDigit), d = new BigInt;
    for (arrayCopy(a.digits, 0, d.digits, c, d.digits.length - c),
             e = b % bitsPerDigit,
             f = bitsPerDigit - e,
             g = d.digits.length - 1,
             h = g - 1; g > 0; --g,
             --h)
        d.digits[g] = d.digits[g] << e & maxDigitVal | (d.digits[h] & highBitMasks[e]) >>> f;
    return d.digits[0] = d.digits[g] << e & maxDigitVal,
        d.isNeg = a.isNeg,
        d
}

function biShiftRight(a, b) {
    var e, f, g, h, c = Math.floor(b / bitsPerDigit), d = new BigInt;
    for (arrayCopy(a.digits, c, d.digits, 0, a.digits.length - c),
             e = b % bitsPerDigit,
             f = bitsPerDigit - e,
             g = 0,
             h = g + 1; g < d.digits.length - 1; ++g,
             ++h)
        d.digits[g] = d.digits[g] >>> e | (d.digits[h] & lowBitMasks[e]) << f;
    return d.digits[d.digits.length - 1] >>>= e,
        d.isNeg = a.isNeg,
        d
}

function biMultiplyByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, 0, c.digits, b, c.digits.length - b),
        c
}

function biDivideByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, b, c.digits, 0, c.digits.length - b),
        c
}

function biModuloByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, 0, c.digits, 0, b),
        c
}

function biCompare(a, b) {
    if (a.isNeg != b.isNeg)
        return 1 - 2 * Number(a.isNeg);
    for (var c = a.digits.length - 1; c >= 0; --c)
        if (a.digits[c] != b.digits[c])
            return a.isNeg ? 1 - 2 * Number(a.digits[c] > b.digits[c]) : 1 - 2 * Number(a.digits[c] < b.digits[c]);
    return 0
}

function biDivideModulo(a, b) {
    var f, g, h, i, j, k, l, m, n, o, p, q, r, s, c = biNumBits(a), d = biNumBits(b), e = b.isNeg;
    if (d > c)
        return a.isNeg ? (f = biCopy(bigOne),
            f.isNeg = !b.isNeg,
            a.isNeg = !1,
            b.isNeg = !1,
            g = biSubtract(b, a),
            a.isNeg = !0,
            b.isNeg = e) : (f = new BigInt,
            g = biCopy(a)),
            new Array(f, g);
    for (f = new BigInt,
             g = a,
             h = Math.ceil(d / bitsPerDigit) - 1,
             i = 0; b.digits[h] < biHalfRadix;)
        b = biShiftLeft(b, 1),
            ++i,
            ++d,
            h = Math.ceil(d / bitsPerDigit) - 1;
    for (g = biShiftLeft(g, i),
             c += i,
             j = Math.ceil(c / bitsPerDigit) - 1,
             k = biMultiplyByRadixPower(b, j - h); -1 != biCompare(g, k);)
        ++f.digits[j - h],
            g = biSubtract(g, k);
    for (l = j; l > h; --l) {
        for (m = l >= g.digits.length ? 0 : g.digits[l],
                 n = l - 1 >= g.digits.length ? 0 : g.digits[l - 1],
                 o = l - 2 >= g.digits.length ? 0 : g.digits[l - 2],
                 p = h >= b.digits.length ? 0 : b.digits[h],
                 q = h - 1 >= b.digits.length ? 0 : b.digits[h - 1],
                 f.digits[l - h - 1] = m == p ? maxDigitVal : Math.floor((m * biRadix + n) / p),
                 r = f.digits[l - h - 1] * (p * biRadix + q),
                 s = m * biRadixSquared + (n * biRadix + o); r > s;)
            --f.digits[l - h - 1],
                r = f.digits[l - h - 1] * (p * biRadix | q),
                s = m * biRadix * biRadix + (n * biRadix + o);
        k = biMultiplyByRadixPower(b, l - h - 1),
            g = biSubtract(g, biMultiplyDigit(k, f.digits[l - h - 1])),
        g.isNeg && (g = biAdd(g, k),
            --f.digits[l - h - 1])
    }
    return g = biShiftRight(g, i),
        f.isNeg = a.isNeg != e,
    a.isNeg && (f = e ? biAdd(f, bigOne) : biSubtract(f, bigOne),
        b = biShiftRight(b, i),
        g = biSubtract(b, g)),
    0 == g.digits[0] && 0 == biHighIndex(g) && (g.isNeg = !1),
        new Array(f, g)
}

function biDivide(a, b) {
    return biDivideModulo(a, b)[0]
}

function biModulo(a, b) {
    return biDivideModulo(a, b)[1]
}

function biMultiplyMod(a, b, c) {
    return biModulo(biMultiply(a, b), c)
}

function biPow(a, b) {
    for (var c = bigOne, d = a; ;) {
        if (0 != (1 & b) && (c = biMultiply(c, d)),
            b >>= 1,
        0 == b)
            break;
        d = biMultiply(d, d)
    }
    return c
}

function biPowMod(a, b, c) {
    for (var d = bigOne, e = a, f = b; ;) {
        if (0 != (1 & f.digits[0]) && (d = biMultiplyMod(d, e, c)),
            f = biShiftRight(f, 1),
        0 == f.digits[0] && 0 == biHighIndex(f))
            break;
        e = biMultiplyMod(e, e, c)
    }
    return d
}

function BarrettMu(a) {
    this.modulus = biCopy(a),
        this.k = biHighIndex(this.modulus) + 1;
    var b = new BigInt;
    b.digits[2 * this.k] = 1,
        this.mu = biDivide(b, this.modulus),
        this.bkplus1 = new BigInt,
        this.bkplus1.digits[this.k + 1] = 1,
        this.modulo = BarrettMu_modulo,
        this.multiplyMod = BarrettMu_multiplyMod,
        this.powMod = BarrettMu_powMod
}

function BarrettMu_modulo(a) {
    var i, b = biDivideByRadixPower(a, this.k - 1), c = biMultiply(b, this.mu), d = biDivideByRadixPower(c, this.k + 1),
        e = biModuloByRadixPower(a, this.k + 1), f = biMultiply(d, this.modulus),
        g = biModuloByRadixPower(f, this.k + 1), h = biSubtract(e, g);
    for (h.isNeg && (h = biAdd(h, this.bkplus1)),
             i = biCompare(h, this.modulus) >= 0; i;)
        h = biSubtract(h, this.modulus),
            i = biCompare(h, this.modulus) >= 0;
    return h
}

function BarrettMu_multiplyMod(a, b) {
    var c = biMultiply(a, b);
    return this.modulo(c)
}

function BarrettMu_powMod(a, b) {
    var d, e, c = new BigInt;
    for (c.digits[0] = 1,
             d = a,
             e = b; ;) {
        if (0 != (1 & e.digits[0]) && (c = this.multiplyMod(c, d)),
            e = biShiftRight(e, 1),
        0 == e.digits[0] && 0 == biHighIndex(e))
            break;
        d = this.multiplyMod(d, d)
    }
    return c
}

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);

虽然结果出来了，但是和刚才获取的不一样，这两个值是否有效呢？其实每次获取的都不会一样的，因为a函数中有个random获取的获取的是随机值。至于是否有效，可以将数据请求一下就知道是否可以了。

方式2. 根据作用域补函数

首先补充几个知识点。

匿名函数

JavaScript 中的匿名函数是指没有名字的函数，通常被用作一次性的、临时的函数。匿名函数有两种主要的形式：函数表达式和箭头函数。

函数表达式

函数表达式是指将函数赋值给一个变量或者常量，而不是声明一个具有名称的函数。这个函数可以是匿名的。

// 匿名函数表达式
const add = function(x, y) {
  return x + y;
};

// 使用匿名函数
console.log(add(2, 3)); // 输出 5

箭头函数

箭头函数是 ES6 引入的一种更简洁的函数写法。它可以更方便地定义匿名函数。

// 匿名箭头函数
const add = (x, y) => {
  return x + y;
};

// 如果函数体只有一行，可以省略大括号和 return
const multiply = (x, y) => x * y;

// 使用匿名箭头函数
console.log(add(2, 3));      // 输出 5
console.log(multiply(2, 3)); // 输出 6

匿名函数通常在需要临时处理某些逻辑的情况下使用，或者作为函数的参数传递。它们在创建回调函数、事件处理函数等场景中非常常见。由于匿名函数没有名字，因此不能通过名字调用，必须通过变量或者直接在表达式中使用。

在 JavaScript 中，每个函数都创建了一个新的作用域。函数内部的变量在函数外部是不可访问的，这被称为函数作用域。而匿名函数也遵循这一规则。

// 全局作用域
var globalVar = 'I am global';

function exampleFunction() {
  // 函数作用域
  var localVar = 'I am local';
  console.log(globalVar); // 可以访问全局变量
  console.log(localVar);  // 可以访问本地变量
}

exampleFunction();
// console.log(localVar); // 错误，localVar 不在此作用域可见

匿名函数通常与闭包密切相关。闭包是指一个函数能够记住并访问它被创建时所处的作用域，即使该函数在不同的作用域被调用。匿名函数经常被用作闭包。

function outerFunction() {
  var outerVar = 'I am outer';

  // 返回一个匿名函数，形成闭包
  return function() {
    console.log(outerVar); // 访问 outerFunction 的局部变量
  };
}

var closureFunction = outerFunction();
closureFunction(); // 输出 'I am outer'

在上述例子中，closureFunction 是一个匿名函数，它被赋值为 outerFunction 的返回值。由于匿名函数被返回并在外部作用域执行，它形成了一个闭包，可以访问外部函数 outerFunction 的局部变量 outerVar。

匿名函数在闭包中经常用于保持某个函数内的状态，并在以后的调用中保留这个状态。

总的来说，匿名函数和作用域之间的关系表现在匿名函数遵循函数作用域规则，并且匿名函数常常用于创建闭包，以保留函数创建时的作用域。

整体思路

• 首先复制全局变量
• 然后复制重点功能函数

那么具体怎么做呢？举个例子，刚才d函数嵌套使用了c函数，c函数又使用了RSAKeyPair函数，但是RSAKeyPair这个函数明显和c不在一个作用域里，所以就要把这个函数所在的作用域的代码全部复制过来。

JavaScript 的顶级作用域是指代码中不包含在任何函数内的部分，即全局作用域。在浏览器环境中，顶级作用域通常是整个页面。在 Node.js 等环境中，顶级作用域可以是整个 Node.js 模块。

在顶级作用域中声明的变量和函数具有全局作用域，可以被程序中的任何其他作用域访问。这意味着在全局范围内声明的变量在整个程序中都是可见的。

所以像RSAKeyPair这样类似的代码可以全部复制过来，如果运行报错就接着补。补完全局变量后就再补具体的功能函数。

代码

const CryptoJS = require('crypto-js');
// 全局变量
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 () {
    function a(a) {
        var d, e, b = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789", c = "";
        for (d = 0; a > d; d += 1) e = Math.random() * b.length, e = Math.floor(e), c += b.charAt(e);
        return c
    }

    function b(a, b) {
        var c = CryptoJS.enc.Utf8.parse(b), d = CryptoJS.enc.Utf8.parse("0102030405060708"),
            e = CryptoJS.enc.Utf8.parse(a), f = CryptoJS.AES.encrypt(e, c, {
                iv: d, mode: CryptoJS.mode.CBC
            });
        return f.toString()
    }

    function c(a, b, c) {
        var d, e;
        return setMaxDigits(131), d = new RSAKeyPair(b, "", c), e = encryptedString(d, a)
    }

    function d(d, e, f, g) {
        var h = {}, i = a(16);
        return h.encText = b(d, g), h.encText = b(h.encText, i), h.encSecKey = c(i, e, f), h
    }

    function e(a, b, d, e) {
        var f = {};
        return f.encText = c(a + e, b, d), f
    }

}();


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 = "-" == a.charAt(0), c = b ? 1 : 0; c < a.length && "0" == a.charAt(c);) ++c;
    if (c == a.length) d = new BigInt; else {
        for (e = a.length - c, f = e % dpl10, 0 == f && (f = dpl10), d = biFromNumber(Number(a.substr(c, f))), c += f; c < a.length;) d = biAdd(biMultiply(d, lr10), biFromNumber(Number(a.substr(c, dpl10)))), c += dpl10;
        d.isNeg = b
    }
    return d
}

function biCopy(a) {
    var b = new BigInt(!0);
    return b.digits = a.digits.slice(0), b.isNeg = a.isNeg, b
}

function biFromNumber(a) {
    var c, b = new BigInt;
    for (b.isNeg = 0 > a, a = Math.abs(a), c = 0; a > 0;) b.digits[c++] = a & maxDigitVal, a >>= biRadixBits;
    return b
}

function reverseStr(a) {
    var c, b = "";
    for (c = a.length - 1; c > -1; --c) b += a.charAt(c);
    return b
}

function biToString(a, b) {
    var d, e, c = new BigInt;
    for (c.digits[0] = b, d = biDivideModulo(a, c), e = hexatrigesimalToChar[d[1].digits[0]]; 1 == biCompare(d[0], bigZero);) d = biDivideModulo(d[0], c), digit = d[1].digits[0], e += hexatrigesimalToChar[d[1].digits[0]];
    return (a.isNeg ? "-" : "") + reverseStr(e)
}

function biToDecimal(a) {
    var c, d, b = new BigInt;
    for (b.digits[0] = 10, c = biDivideModulo(a, b), d = String(c[1].digits[0]); 1 == biCompare(c[0], bigZero);) c = biDivideModulo(c[0], b), d += String(c[1].digits[0]);
    return (a.isNeg ? "-" : "") + reverseStr(d)
}

function digitToHex(a) {
    var b = 15, c = "";
    for (i = 0; 4 > i; ++i) c += hexToChar[a & b], a >>>= 4;
    return reverseStr(c)
}

function biToHex(a) {
    var d, b = "";
    for (biHighIndex(a), d = biHighIndex(a); d > -1; --d) b += digitToHex(a.digits[d]);
    return b
}

function charToHex(a) {
    var h, b = 48, c = b + 9, d = 97, e = d + 25, f = 65, g = 90;
    return h = a >= b && c >= a ? a - b : a >= f && g >= a ? 10 + a - f : a >= d && e >= a ? 10 + a - d : 0
}

function hexToDigit(a) {
    var d, b = 0, c = Math.min(a.length, 4);
    for (d = 0; c > d; ++d) b <<= 4, b |= charToHex(a.charCodeAt(d));
    return b
}

function biFromHex(a) {
    var d, e, b = new BigInt, c = a.length;
    for (d = c, e = 0; d > 0; d -= 4, ++e) b.digits[e] = hexToDigit(a.substr(Math.max(d - 4, 0), Math.min(d, 4)));
    return b
}

function biFromString(a, b) {
    var g, h, i, j, c = "-" == a.charAt(0), d = c ? 1 : 0, e = new BigInt, f = new BigInt;
    for (f.digits[0] = 1, g = a.length - 1; g >= d; g--) h = a.charCodeAt(g), i = charToHex(h), j = biMultiplyDigit(f, i), e = biAdd(e, j), f = biMultiplyDigit(f, b);
    return e.isNeg = c, e
}

function biDump(a) {
    return (a.isNeg ? "-" : "") + a.digits.join(" ")
}

function biAdd(a, b) {
    var c, d, e, f;
    if (a.isNeg != b.isNeg) b.isNeg = !b.isNeg, c = biSubtract(a, b), b.isNeg = !b.isNeg; else {
        for (c = new BigInt, d = 0, f = 0; f < a.digits.length; ++f) e = a.digits[f] + b.digits[f] + d, c.digits[f] = 65535 & e, d = Number(e >= biRadix);
        c.isNeg = a.isNeg
    }
    return c
}

function biSubtract(a, b) {
    var c, d, e, f;
    if (a.isNeg != b.isNeg) b.isNeg = !b.isNeg, c = biAdd(a, b), b.isNeg = !b.isNeg; else {
        for (c = new BigInt, e = 0, f = 0; f < a.digits.length; ++f) d = a.digits[f] - b.digits[f] + e, c.digits[f] = 65535 & d, c.digits[f] < 0 && (c.digits[f] += biRadix), e = 0 - Number(0 > d);
        if (-1 == e) {
            for (e = 0, f = 0; f < a.digits.length; ++f) d = 0 - c.digits[f] + e, c.digits[f] = 65535 & d, c.digits[f] < 0 && (c.digits[f] += biRadix), e = 0 - Number(0 > d);
            c.isNeg = !a.isNeg
        } else c.isNeg = a.isNeg
    }
    return c
}

function biHighIndex(a) {
    for (var b = a.digits.length - 1; b > 0 && 0 == a.digits[b];) --b;
    return b
}

function biNumBits(a) {
    var e, b = biHighIndex(a), c = a.digits[b], d = (b + 1) * bitsPerDigit;
    for (e = d; e > d - bitsPerDigit && 0 == (32768 & c); --e) c <<= 1;
    return e
}

function biMultiply(a, b) {
    var d, h, i, k, c = new BigInt, e = biHighIndex(a), f = biHighIndex(b);
    for (k = 0; f >= k; ++k) {
        for (d = 0, i = k, j = 0; e >= j; ++j, ++i) h = c.digits[i] + a.digits[j] * b.digits[k] + d, c.digits[i] = h & maxDigitVal, d = h >>> biRadixBits;
        c.digits[k + e + 1] = d
    }
    return c.isNeg = a.isNeg != b.isNeg, c
}

function biMultiplyDigit(a, b) {
    var c, d, e, f;
    for (result = new BigInt, c = biHighIndex(a), d = 0, f = 0; c >= f; ++f) e = result.digits[f] + a.digits[f] * b + d, result.digits[f] = e & maxDigitVal, d = e >>> biRadixBits;
    return result.digits[1 + c] = d, result
}

function arrayCopy(a, b, c, d, e) {
    var g, h, f = Math.min(b + e, a.length);
    for (g = b, h = d; f > g; ++g, ++h) c[h] = a[g]
}

function biShiftLeft(a, b) {
    var e, f, g, h, c = Math.floor(b / bitsPerDigit), d = new BigInt;
    for (arrayCopy(a.digits, 0, d.digits, c, d.digits.length - c), e = b % bitsPerDigit, f = bitsPerDigit - e, g = d.digits.length - 1, h = g - 1; g > 0; --g, --h) d.digits[g] = d.digits[g] << e & maxDigitVal | (d.digits[h] & highBitMasks[e]) >>> f;
    return d.digits[0] = d.digits[g] << e & maxDigitVal, d.isNeg = a.isNeg, d
}

function biShiftRight(a, b) {
    var e, f, g, h, c = Math.floor(b / bitsPerDigit), d = new BigInt;
    for (arrayCopy(a.digits, c, d.digits, 0, a.digits.length - c), e = b % bitsPerDigit, f = bitsPerDigit - e, g = 0, h = g + 1; g < d.digits.length - 1; ++g, ++h) d.digits[g] = d.digits[g] >>> e | (d.digits[h] & lowBitMasks[e]) << f;
    return d.digits[d.digits.length - 1] >>>= e, d.isNeg = a.isNeg, d
}

function biMultiplyByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, 0, c.digits, b, c.digits.length - b), c
}

function biDivideByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, b, c.digits, 0, c.digits.length - b), c
}

function biModuloByRadixPower(a, b) {
    var c = new BigInt;
    return arrayCopy(a.digits, 0, c.digits, 0, b), c
}

function biCompare(a, b) {
    if (a.isNeg != b.isNeg) return 1 - 2 * Number(a.isNeg);
    for (var c = a.digits.length - 1; c >= 0; --c) if (a.digits[c] != b.digits[c]) return a.isNeg ? 1 - 2 * Number(a.digits[c] > b.digits[c]) : 1 - 2 * Number(a.digits[c] < b.digits[c]);
    return 0
}

function biDivideModulo(a, b) {
    var f, g, h, i, j, k, l, m, n, o, p, q, r, s, c = biNumBits(a), d = biNumBits(b), e = b.isNeg;
    if (d > c) return a.isNeg ? (f = biCopy(bigOne), f.isNeg = !b.isNeg, a.isNeg = !1, b.isNeg = !1, g = biSubtract(b, a), a.isNeg = !0, b.isNeg = e) : (f = new BigInt, g = biCopy(a)), new Array(f, g);
    for (f = new BigInt, g = a, h = Math.ceil(d / bitsPerDigit) - 1, i = 0; b.digits[h] < biHalfRadix;) b = biShiftLeft(b, 1), ++i, ++d, h = Math.ceil(d / bitsPerDigit) - 1;
    for (g = biShiftLeft(g, i), c += i, j = Math.ceil(c / bitsPerDigit) - 1, k = biMultiplyByRadixPower(b, j - h); -1 != biCompare(g, k);) ++f.digits[j - h], g = biSubtract(g, k);
    for (l = j; l > h; --l) {
        for (m = l >= g.digits.length ? 0 : g.digits[l], n = l - 1 >= g.digits.length ? 0 : g.digits[l - 1], o = l - 2 >= g.digits.length ? 0 : g.digits[l - 2], p = h >= b.digits.length ? 0 : b.digits[h], q = h - 1 >= b.digits.length ? 0 : b.digits[h - 1], f.digits[l - h - 1] = m == p ? maxDigitVal : Math.floor((m * biRadix + n) / p), r = f.digits[l - h - 1] * (p * biRadix + q), s = m * biRadixSquared + (n * biRadix + o); r > s;) --f.digits[l - h - 1], r = f.digits[l - h - 1] * (p * biRadix | q), s = m * biRadix * biRadix + (n * biRadix + o);
        k = biMultiplyByRadixPower(b, l - h - 1), g = biSubtract(g, biMultiplyDigit(k, f.digits[l - h - 1])), g.isNeg && (g = biAdd(g, k), --f.digits[l - h - 1])
    }
    return g = biShiftRight(g, i), f.isNeg = a.isNeg != e, a.isNeg && (f = e ? biAdd(f, bigOne) : biSubtract(f, bigOne), b = biShiftRight(b, i), g = biSubtract(b, g)), 0 == g.digits[0] && 0 == biHighIndex(g) && (g.isNeg = !1), new Array(f, g)
}

function biDivide(a, b) {
    return biDivideModulo(a, b)[0]
}

function biModulo(a, b) {
    return biDivideModulo(a, b)[1]
}

function biMultiplyMod(a, b, c) {
    return biModulo(biMultiply(a, b), c)
}

function biPow(a, b) {
    for (var c = bigOne, d = a; ;) {
        if (0 != (1 & b) && (c = biMultiply(c, d)), b >>= 1, 0 == b) break;
        d = biMultiply(d, d)
    }
    return c
}

function biPowMod(a, b, c) {
    for (var d = bigOne, e = a, f = b; ;) {
        if (0 != (1 & f.digits[0]) && (d = biMultiplyMod(d, e, c)), f = biShiftRight(f, 1), 0 == f.digits[0] && 0 == biHighIndex(f)) break;
        e = biMultiplyMod(e, e, c)
    }
    return d
}

function BarrettMu(a) {
    this.modulus = biCopy(a), this.k = biHighIndex(this.modulus) + 1;
    var b = new BigInt;
    b.digits[2 * this.k] = 1, this.mu = biDivide(b, this.modulus), this.bkplus1 = new BigInt, this.bkplus1.digits[this.k + 1] = 1, this.modulo = BarrettMu_modulo, this.multiplyMod = BarrettMu_multiplyMod, this.powMod = BarrettMu_powMod
}

function BarrettMu_modulo(a) {
    var i, b = biDivideByRadixPower(a, this.k - 1), c = biMultiply(b, this.mu), d = biDivideByRadixPower(c, this.k + 1),
        e = biModuloByRadixPower(a, this.k + 1), f = biMultiply(d, this.modulus),
        g = biModuloByRadixPower(f, this.k + 1), h = biSubtract(e, g);
    for (h.isNeg && (h = biAdd(h, this.bkplus1)), i = biCompare(h, this.modulus) >= 0; i;) h = biSubtract(h, this.modulus), i = biCompare(h, this.modulus) >= 0;
    return h
}

function BarrettMu_multiplyMod(a, b) {
    var c = biMultiply(a, b);
    return this.modulo(c)
}

function BarrettMu_powMod(a, b) {
    var d, e, c = new BigInt;
    for (c.digits[0] = 1, d = a, e = b; ;) {
        if (0 != (1 & e.digits[0]) && (c = this.multiplyMod(c, d)), e = biShiftRight(e, 1), 0 == e.digits[0] && 0 == biHighIndex(e)) break;
        d = this.multiplyMod(d, d)
    }
    return c
}

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);

// 具体功能函数

function a(a) {
    var d, e, b = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789", c = "";
    for (d = 0; a > d; d += 1) e = Math.random() * b.length, e = Math.floor(e), c += b.charAt(e);
    return c
}

function b(a, b) {
    var c = CryptoJS.enc.Utf8.parse(b), d = CryptoJS.enc.Utf8.parse("0102030405060708"), e = CryptoJS.enc.Utf8.parse(a),
        f = CryptoJS.AES.encrypt(e, c, {
            iv: d, mode: CryptoJS.mode.CBC
        });
    return f.toString()
}

function c(a, b, c) {
    var d, e;
    return setMaxDigits(131), d = new RSAKeyPair(b, "", c), e = encryptedString(d, a)
}

function d(d, e, f, g) {
    var h = {}, i = a(16);
    return h.encText = b(d, g), h.encText = b(h.encText, i), h.encSecKey = c(i, e, f), h
}

function e(a, b, d, e) {
    var f = {};
    return f.encText = c(a + e, b, d), f
}

ret = d("{\"ids\":\"[2095868608]\",\"level\":\"standard\",\"encodeType\":\"aac\",\"csrf_token\":\"\"}", "010001", "00e0b509f6259df8642dbc35662901477df22677ec152b5ff68ace615bb7b725152b3ab17a876aea8a5aa76d2e417629ec4ee341f56135fccf695280104e0312ecbda92557c93870114af6c9d05c4f7f0c3685b7a46bee255932575cce10b424d813cfe4875d3e82047b97ddef52741d546b8e289dc6935b3ece0462db0a22b8e7", "0CoJUm6Qyw8W8jud")
console.log(ret)

其实代码并不重要，重要的是根据作用域补函数的方法。如果掌握了这个方法，整体时间绝对会比逐个补函数的方式快上N倍。就算代码量大个几倍又如何，没人在乎你用多少代码来实现的，只关心是否实现了功能。毕竟爬虫的逆向不能完全和企业的业务功能做比较。

Python 调用代码

import requests
import execjs

url = 'https://music.163.com/weapi/song/enhance/player/url/v1?csrf_token='

# （1）获取动态逆向值
with open("03.wangyiyun.js", encoding='utf8') as f:
    js_code = f.read()
x1 = '{"ids":"[2112572518]","level":"standard","encodeType":"aac","csrf_token":""}'
x2 = '010001'
x3 = '00e0b509f6259df8642dbc35662901477df22677ec152b5ff68ace615bb7b725152b3ab17a876aea8a5aa76d2e417629ec4ee341f56135fccf695280104e0312ecbda92557c93870114af6c9d05c4f7f0c3685b7a46bee255932575cce10b424d813cfe4875d3e82047b97ddef52741d546b8e289dc6935b3ece0462db0a22b8e7'
x4 = '0CoJUm6Qyw8W8jud'

js_compile = execjs.compile(js_code)
ret = js_compile.call("d", x1, x2, x3, x4)
print(ret)

data = {
    'params': ret['encText'],
    'encSecKey': ret['encSecKey']
}

# （2）发起请求
headers = {
    'Cookie': 'NMTID=00OUP-lPsbfCaizqEbTs44xdWI9iVEAAAGMs2OS2A; _iuqxldmzr_=32; _ntes_nnid=11283d80021405d3ce8ab6d87d13f707,1703816695136; _ntes_nuid=11283d80021405d3ce8ab6d87d13f707; WEVNSM=1.0.0; WNMCID=zwlxbn.1703816696122.01.0; WM_TID=llm1JvK0VU5EUQEQVQbF5NoOfAvC4dTS; sDeviceId=YD-WlJjpmN14vtEAhVRFROE4N8ebU7cBIcE; ntes_utid=tid._.pt009SV%252BTntFAwABFFKQpd4ePVrYUXR5._.0; JSESSIONID-WYYY=a%2FO%5C3E1jgS6M1SkRdBm%5CTg3hM%5C00DGc3EgmgYKVPwb0YWOWjDfZWEcgYTJiOlUzmtN0%2FvdZjpps3GT0oHbrpAogaTjcf0STxbs%5C8DP%5CvUeOf%2B5YVqPfpCjGIiQvKxHR6U213e9a9jARDrWnDiftyzO8EH%2By1btI6BZOMP2oHnBnunoI0%3A1704512275710; WM_NI=atC7iPZN92iGZ6dFn3SVpKOOYte4SjnQL4gxsnh4eyl8ZJ%2FmEdbQqR90m%2BWk8vOcIClrOINZ3O%2FxsOk7XNWdSwN8K6GIZzFta2bOd0NWVorKcL%2B4FIo7nWlrUGlkskg9aFk%3D; WM_NIKE=9ca17ae2e6ffcda170e2e6eea9f47b96e898b8e75c8ee78ab2c55e938a8a83c8658dbba59af56eaf978cb1e52af0fea7c3b92aa3ac8dd8ec5c9a92f7d3ec4d9aeaaca7ed39918ac0acce459bacabd5d262ae8f84d5e674b1b2a8d5e873b0e896abae6787bcaeb2f45afbf0a3ccd661fcaa8184cc49b0ae81aacd52f191e199f245a9e998afd67091a982d9ca3e8597969bc580a3eeaeb0e73c8e899a90f141a194e5d5c543ade9a2b8ef7a9799a48cf261a5e7afa7ea37e2a3',
    'Origin': 'https://music.163.com',
    'Referer': 'https://music.163.com/',
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36'
}
res = requests.post(url, data=data, headers=headers)
print(res.text)

python调用的代码就很简单了，唯一的变量就是歌曲ID。其实歌曲ID这个获取也很假单，比如有个歌单，是不是就可以批量获取ID了。举个例子，就算在接口中没有找到合适的数据，但是也可以用xpath进行解析啊。方法有很多，有效就行。

4. 总结

通过两种JS补函数的方式实现了当前功能的逆向。方法有多种，只要能实现即可。简单的功能简单做，复杂的功能复杂做。