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filter_legal_legalcn_decrypt.py

#!/usr/bin/env python3
from Crypto.Cipher import AES
from Crypto.Util.Padding import unpad
import gzip

STEAMCHINA_ENCRYPTION_KEY = bytes([
    0x06, 0x89, 0x2a, 0x9c, 0x7d, 0x9b, 0xc6, 0x98,
    0xc0, 0xf9, 0x03, 0x36, 0x0e, 0x3c, 0x22, 0x88,
    0xba, 0x3d, 0xe4, 0x0f, 0xf7, 0x11, 0x01, 0xc2,
    0x04, 0xb5, 0x20, 0xbe, 0x22, 0xc2, 0xad, 0xa4
])

def decrypt_aes_ecb(encrypted_iv, key):
    cipher = AES.new(key, AES.MODE_ECB)
    return cipher.decrypt(encrypted_iv)

def decrypt_aes_cbc(encrypted_data, key, iv):
    cipher = AES.new(key, AES.MODE_CBC, iv)
    return unpad(cipher.decrypt(encrypted_data), AES.block_size)

with open("filter_legal_legalcn.txt.gz", "rb") as f:
    encrypted_data = gzip.decompress(f.read())

# First 16 bytes is AES-ECB encrypted IV
decrypted_iv = decrypt_aes_ecb(encrypted_data[:16], STEAMCHINA_ENCRYPTION_KEY)

# Remaining bytes is AES-CBC encrypted data
decrypted_data = decrypt_aes_cbc(encrypted_data[16:], STEAMCHINA_ENCRYPTION_KEY, decrypted_iv)

if decrypted_data:
    with open("filter_legal_legalcn.txt", "wb") as f:
        f.write(decrypted_data)