MusicServer/app/sdk/platforms/xm/decoder.py

"""喜马拉雅播放地址解码（对应 sdk/xm/decoder.ts，移植 Ximalaya-Downloader-Next adapters/decoder.py）。

算法：URL-safe Base64 → 尾 16 字节为 IV，正文先查 S-Box 置换表，
再按 16 字节块与 IV 异或、按 32 字节块与固定密钥异或，还原明文 URL。
PC 桌面端（device=win）另有 AES-ECB 变体（密钥取自官方客户端 4.0.14 asar）。
"""

from __future__ import annotations

import base64

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes

from app.sdk.platforms.kg.util import pkcs7_unpad

#: S-Box 置换表（www2/mweb2 设备类型）
PERMUTATION_TABLE_O = [
    183,
    174,
    108,
    16,
    131,
    159,
    250,
    5,
    239,
    110,
    193,
    202,
    153,
    137,
    251,
    176,
    119,
    150,
    47,
    204,
    97,
    237,
    1,
    71,
    177,
    42,
    88,
    218,
    166,
    82,
    87,
    94,
    14,
    195,
    69,
    127,
    215,
    240,
    225,
    197,
    238,
    142,
    123,
    44,
    219,
    50,
    190,
    29,
    181,
    186,
    169,
    98,
    139,
    185,
    152,
    13,
    141,
    76,
    6,
    157,
    200,
    132,
    182,
    49,
    20,
    116,
    136,
    43,
    155,
    194,
    101,
    231,
    162,
    242,
    151,
    213,
    53,
    60,
    26,
    134,
    211,
    56,
    28,
    223,
    107,
    161,
    199,
    15,
    229,
    61,
    96,
    41,
    66,
    158,
    254,
    21,
    165,
    253,
    103,
    89,
    3,
    168,
    40,
    246,
    81,
    95,
    58,
    31,
    172,
    78,
    99,
    45,
    148,
    187,
    222,
    124,
    55,
    203,
    235,
    64,
    68,
    149,
    180,
    35,
    113,
    207,
    118,
    111,
    91,
    38,
    247,
    214,
    7,
    212,
    209,
    189,
    241,
    18,
    115,
    173,
    25,
    236,
    121,
    249,
    75,
    57,
    216,
    10,
    175,
    112,
    234,
    164,
    70,
    206,
    198,
    255,
    140,
    230,
    12,
    32,
    83,
    46,
    245,
    0,
    62,
    227,
    72,
    191,
    156,
    138,
    248,
    114,
    220,
    90,
    84,
    170,
    128,
    19,
    24,
    122,
    146,
    80,
    39,
    37,
    8,
    34,
    22,
    11,
    93,
    130,
    63,
    154,
    244,
    160,
    144,
    79,
    23,
    133,
    92,
    54,
    102,
    210,
    65,
    67,
    27,
    196,
    201,
    106,
    143,
    52,
    74,
    100,
    217,
    179,
    48,
    233,
    126,
    117,
    184,
    226,
    85,
    171,
    167,
    86,
    2,
    147,
    17,
    135,
    228,
    252,
    105,
    30,
    192,
    129,
    178,
    120,
    36,
    145,
    51,
    163,
    77,
    205,
    73,
    4,
    188,
    125,
    232,
    33,
    243,
    109,
    224,
    104,
    208,
    221,
    59,
    9,
]

XOR_KEY_A = [
    204,
    53,
    135,
    197,
    39,
    73,
    58,
    160,
    79,
    24,
    12,
    83,
    180,
    250,
    101,
    60,
    206,
    30,
    10,
    227,
    36,
    95,
    161,
    16,
    135,
    150,
    235,
    116,
    242,
    116,
    165,
    171,
]

#: PC 桌面端 playUrlList 的 AES-ECB 密钥（客户端 4.0.14 asar Gt 函数提取）
WIN_AES_KEY = bytes.fromhex("aaad3e4fd540b0f79dca95606e72bf93")


def _b64url_to_buf(text: str) -> bytes:
    cleaned = text.replace("_", "/").replace("-", "+")
    cleaned += "=" * (-len(cleaned) % 4)
    return base64.b64decode(cleaned)


def decode_www2_url(encrypted: str) -> str:
    """www2/mweb2 加密 URL → 明文 URL。"""
    if not encrypted:
        return ""
    if encrypted.startswith("http"):
        return encrypted
    decoded = _b64url_to_buf(encrypted)
    if len(decoded) < 16:
        raise RuntimeError("密文长度不足（缺少 IV）")
    body = bytearray(decoded[:-16])
    iv = decoded[-16:]

    for i in range(len(body)):
        body[i] = PERMUTATION_TABLE_O[body[i]]
    for i in range(0, len(body), 16):
        count = min(16, len(body) - i)
        for j in range(count):
            body[i + j] ^= iv[j]
    for i in range(0, len(body), 32):
        count = min(32, len(body) - i)
        for j in range(count):
            body[i + j] ^= XOR_KEY_A[j]
    return bytes(body).decode("utf-8", errors="replace")


def decode_win_url(encrypted: str) -> str:
    """PC 桌面端（device=win）AES-ECB 加密 URL → 明文 URL（解出的是带签名付费地址）。"""
    if not encrypted:
        return ""
    if encrypted.startswith("http"):
        return encrypted
    decryptor = Cipher(algorithms.AES(WIN_AES_KEY), modes.ECB()).decryptor()
    plain = decryptor.update(_b64url_to_buf(encrypted)) + decryptor.finalize()
    return pkcs7_unpad(plain).decode("utf-8", errors="replace")