网易云音乐把.mp3音乐文件加密为.ncm文件,导致不能将下载好的音乐复制到其它设备或使用非网易云音乐播放器播放,该程序可将.ncm文件逆向解密为.mp3文件并保留最高音质。
另有C++已编译.exe转换器,将.ncm文件拖到.exe上直接执行转换,生成.mp3文件在.ncm文件相同路径。点击下载转换器
Python源码:
# 依赖pycrypto库
import binascii
import struct
import base64
import json
import os
from Crypto.Cipher import AES
def dump(file_path):
core_key = binascii.a2b_hex("687A4852416D736F356B496E62617857")
meta_key = binascii.a2b_hex("2331346C6A6B5F215C5D2630553C2728")
unpad = lambda s : s[0:-(s[-1] if type(s[-1]) == int else ord(s[-1]))]
f = open(file_path,'rb')
header = f.read(8)
assert binascii.b2a_hex(header) == b'4354454e4644414d'
f.seek(2, 1)
key_length = f.read(4)
key_length = struct.unpack('<I', bytes(key_length))[0]
key_data = f.read(key_length)
key_data_array = bytearray(key_data)
for i in range (0,len(key_data_array)): key_data_array[i] ^= 0x64
key_data = bytes(key_data_array)
cryptor = AES.new(core_key, AES.MODE_ECB)
key_data = unpad(cryptor.decrypt(key_data))[17:]
key_length = len(key_data)
key_data = bytearray(key_data)
key_box = bytearray(range(256))
c = 0
last_byte = 0
key_offset = 0
for i in range(256):
swap = key_box[i]
c = (swap + last_byte + key_data[key_offset]) & 0xff
key_offset += 1
if key_offset >= key_length: key_offset = 0
key_box[i] = key_box[c]
key_box[c] = swap
last_byte = c
meta_length = f.read(4)
meta_length = struct.unpack('<I', bytes(meta_length))[0]
meta_data = f.read(meta_length)
meta_data_array = bytearray(meta_data)
for i in range(0,len(meta_data_array)): meta_data_array[i] ^= 0x63
meta_data = bytes(meta_data_array)
meta_data = base64.b64decode(meta_data[22:])
cryptor = AES.new(meta_key, AES.MODE_ECB)
meta_data = unpad(cryptor.decrypt(meta_data)).decode('utf-8')[6:]
meta_data = json.loads(meta_data)
crc32 = f.read(4)
crc32 = struct.unpack('<I', bytes(crc32))[0]
f.seek(5, 1)
image_size = f.read(4)
image_size = struct.unpack('<I', bytes(image_size))[0]
image_data = f.read(image_size)
file_name = meta_data['musicName'] + '.' + meta_data['format']
m = open(os.path.join(os.path.split(file_path)[0],file_name),'wb')
chunk = bytearray()
while True:
chunk = bytearray(f.read(0x8000))
chunk_length = len(chunk)
if not chunk:
break
for i in range(1,chunk_length+1):
j = i & 0xff;
chunk[i-1] ^= key_box[(key_box[j] + key_box[(key_box[j] + j) & 0xff]) & 0xff]
m.write(chunk)
m.close()
f.close()
if __name__ == '__main__':
import sys
if len(sys.argv) > 1:
for file_path in sys.argv[1:]:
try:
dump(file_path)
except:
pass
else:
print("Usage: python ncmdump.py \"File Name\"")