151 lines
4.8 KiB
Python
151 lines
4.8 KiB
Python
import binascii
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import json
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import os
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import struct
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import base64
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from Cryptodome.Cipher import AES
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from Cryptodome.Util.Padding import unpad
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from Cryptodome.Util.strxor import strxor as xor
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from mutagen import mp3, flac, id3
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def regular_filename(filename):
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"""处理替换非法字符"""
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replaces = { # 处理非法字符所用的替换字典(根据网易云下载的文件分析得到)
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"|": "｜",
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":": "：",
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"<": "＜",
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">": "＞",
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"?": "？",
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"/": "／",
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"\\": "＼",
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"*": "＊",
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'"': "＂"
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}
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for k, v in replaces.items():
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filename = filename.replace(k, v)
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return filename
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def load_and_decrypt_from_ncm(file_path, target_dir, out_format) -> dict | str: # author: Nzix Repo: nondanee
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core_key = binascii.a2b_hex('687A4852416D736F356B496E62617857')
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meta_key = binascii.a2b_hex('2331346C6A6B5F215C5D2630553C2728')
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f = open(file_path, 'rb')
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# magic header
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header = f.read(8)
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assert binascii.b2a_hex(header) == b'4354454e4644414d'
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f.seek(2, 1)
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# key data
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key_length = f.read(4)
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key_length = struct.unpack('<I', bytes(key_length))[0]
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key_data = bytearray(f.read(key_length))
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key_data = bytes(bytearray([byte ^ 0x64 for byte in key_data]))
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cryptor = AES.new(core_key, AES.MODE_ECB)
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key_data = unpad(cryptor.decrypt(key_data), 16)[17:]
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key_length = len(key_data)
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# S-box (standard RC4 Key-scheduling algorithm)
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key = bytearray(key_data)
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S = bytearray(range(256))
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j = 0
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for i in range(256):
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j = (j + S[i] + key[i % key_length]) & 0xFF
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S[i], S[j] = S[j], S[i]
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# meta data
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meta_length = f.read(4)
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meta_length = struct.unpack('<I', bytes(meta_length))[0]
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if meta_length:
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meta_data = bytearray(f.read(meta_length))
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meta_data = bytes(bytearray([byte ^ 0x63 for byte in meta_data]))
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identifier = meta_data.decode('utf-8')
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meta_data = base64.b64decode(meta_data[22:])
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cryptor = AES.new(meta_key, AES.MODE_ECB)
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meta_data = unpad(cryptor.decrypt(meta_data), 16).decode('utf-8')
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meta_data = json.loads(meta_data[6:])
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else:
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meta_data = {'format': 'flac' if os.fstat(f.fileno()).st_size > 1024 ** 2 * 16 else 'mp3'}
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f.seek(5, 1)
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# album cover
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image_space = f.read(4)
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image_space = struct.unpack('<I', bytes(image_space))[0]
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image_size = f.read(4)
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image_size = struct.unpack('<I', bytes(image_size))[0]
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image_data = f.read(image_size) if image_size else None
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f.seek(image_space - image_size, 1)
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# media data
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if meta_length:
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output_path = os.path.join(target_dir, regular_filename(out_format % {"name": meta_data["musicName"],
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"artists": "".join(
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[x[0]+"," for x in meta_data["artist"]]
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)[:-1]} + "." + meta_data["format"]))
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else:
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output_path = os.path.join(target_dir, "Unnamed." + meta_data["format"])
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data = f.read()
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f.close()
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# stream cipher (modified RC4 Pseudo-random generation algorithm)
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stream = [S[(S[i] + S[(i + S[i]) & 0xFF]) & 0xFF] for i in range(256)]
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stream = bytes(bytearray(stream * (len(data) // 256 + 1))[1:1 + len(data)])
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data = xor(data, stream)
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m = open(output_path, 'wb')
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m.write(data)
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m.close()
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# media tag
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if meta_length:
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def embed(item, content, t):
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item.encoding = 0
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item.type = t
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item.mime = 'image/png' if content[0:4] == binascii.a2b_hex('89504E47') else 'image/jpeg'
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item.data = content
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if image_data:
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if meta_data['format'] == 'flac':
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audio = flac.FLAC(output_path)
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image = flac.Picture()
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embed(image, image_data, 3)
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audio.clear_pictures()
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audio.add_picture(image)
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audio.save()
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elif meta_data['format'] == 'mp3':
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audio = mp3.MP3(output_path)
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image = id3.APIC()
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embed(image, image_data, 6)
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audio.tags.add(image)
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audio.save()
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if meta_length:
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if meta_data['format'] == 'flac':
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audio = flac.FLAC(output_path)
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audio['description'] = identifier
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else:
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audio = mp3.EasyMP3(output_path)
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audio['title'] = 'placeholder'
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audio.tags.RegisterTextKey('comment', 'COMM')
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audio['comment'] = identifier
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audio['title'] = meta_data['musicName']
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audio['album'] = meta_data['album']
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audio['artist'] = '/'.join([artist[0] for artist in meta_data['artist']])
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audio.save()
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return meta_data
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else:
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return "no_meta_data"
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