decrypt_huawei.py

import sys
import os
from binascii import hexlify, unhexlify
# pip install pycrypto
from Crypto.Cipher import AES
from Crypto.Hash import SHA256
from Crypto.Util import number

# HG352
modem_keys = {
    "HG352": {
        "RSA_D":
            "1B18D0048611500CA489C51D7389B19A"
            "F977E6F5BB8DD5E61A62E339499E6237"
            "C234740129EBD25EF226AB7E498A0830"
            "DF0A5D45F19F5055B906EBC5E71C16C5"
            "A99E36D4F369701FAE2403E445BA3CAE"
            "4B0C9526A82EDD90FECD78B7EDD5EA5E"
            "6C98A0C4CABF3148E99E78DA0D5EB972"
            "6F1533A6738F47C790037D532F403C0D",

        "RSA_N":
            "A93591A1BFCB7615555C12CFE3AF0B68"
            "5A6B94E8604A9441ABF7A5F268D4CBF9"
            "6022E2F0694D679D2C8E4C2D4C3C0C44"
            "60C5646E852A51EF7EBC2F0C88F08E80"
            "6D991446348EB7AF280E607DDA363F4F"
            "322E9B5005503F31F60353219F86443A"
            "04E573FFEF541D21ADD1043E478D81B1"
            "E79A5B434C5F64B3D5B141D7BEB59D71",
        "AES128CBC_KEY": "3E4F5612EF64305955D543B0AE350880",
        "AES128CBC_IV": "8049E91025A6B54876C3B4868090D3FC",
    },
    "HG658": {
        "RSA_D":
            "2345ADB2C06E54D7373E2A233A50150A"
            "4044E417FBF76FB1AC8A444E72A345AA"
            "14B7C349A4824C96DF9ECF7D8CC50425"
            "32930DBD40D86FDCD892398702E3EA51"
            "41C90F10494BB91440E89B104626CCCB"
            "E45A5133362359732954BD63FCA58929"
            "E3D890014FDF83847E6B19F0D9E1117E"
            "9706984EAA57E114934B273366C4DBD1",

        "RSA_N": "C206CF93A9E6EE1CE17984DD54422AC4"
                 "561A4EEB969D1BA81432626D6409FA03"
                 "3B3738F8BBA046ACEF3BAC35094B70AF"
                 "231D9DC43C1D68EDBEBE983E267B72FD"
                 "3C2A7614D60FA7457B92B6A45C49F307"
                 "EA23DE51E7E0C36D6440FC4F62C44CCB"
                 "4169914E43DBFDAE536F002B2D670CE0"
                 "A2A11FD1AF4C484C1A6FED9C228199A3",

        "AES128CBC_KEY": "48EE9D8621739F26C215C49071e2438A",
        "AES128CBC_IV": "A68FBBCA44BB1F5364A530608BCDEAAB",
    }
}

RSA_D = None  # not required
RSA_N = None
AES128CBC_IV = None
AES128CBC_KEY = None

XML_VERSION_STRING = b'<?xml version="1.0" ?>'


def print_usage():
    print("Usage : python " + sys.argv[0] + " config_file_path modem_model")
    print("modem_model only HG352 and HG658.")
    sys.exit(1)


def load_config(config_file):
    if os.path.isfile(config_file):
        cf = open(config_file, "rb")
        config = cf.read()
        cf.close()
    else:
        print("Config file not found..exiting")
        sys.exit(1)
    return config


def save_to_file(dest_file, data):
    with open(dest_file, "wb") as write_file:
        write_file.write(data)


def get_sha256_hash_from_sig(sig):
    sig_int = int(hexlify(sig), 16)
    rsa_n = int(RSA_N, 16)
    dec_sig_as_int = pow(sig_int, 0x10001, rsa_n)
    decrypted_sig = number.long_to_bytes(dec_sig_as_int, 128)
    target_sha256 = hexlify(decrypted_sig)[-64:]
    return target_sha256


def calc_actual_sha256_hash(enc_config_body):
    sha256 = SHA256.new()
    sha256.update(enc_config_body)
    actual_sha256_sig = sha256.hexdigest()
    actual_sha256_sig = str.encode(actual_sha256_sig)
    return actual_sha256_sig


def decrypt_body(enc_config_body):
    iv = unhexlify(AES128CBC_IV)
    key = unhexlify(AES128CBC_KEY)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    decrypted_data = cipher.decrypt(enc_config_body)
    # Strip block padding
    decrypted_data = decrypted_data.rstrip(b'\0')
    return decrypted_data


def decrypt_config(input_file, output_file):
    enc_config = load_config(input_file)
    sig = enc_config[:0x80]
    enc_config_body = enc_config[0x80:]

    print("verifying signature...")
    target_sha256_hash = get_sha256_hash_from_sig(sig)
    actual_sha256_hash = calc_actual_sha256_hash(enc_config_body)

    if actual_sha256_hash == target_sha256_hash:
        print("Signature ok...")
    else:
        print("Signature not ok...exiting")
        sys.exit(1)

    print("Decrypting...")
    decrypted_data = decrypt_body(enc_config_body)

    check_config(decrypted_data)

    print("Saving decrypted config to " + output_file + "...")
    save_to_file(output_file, decrypted_data)


def check_config(new_config_file):
    head = new_config_file[0:len(XML_VERSION_STRING)]
    if head != XML_VERSION_STRING:
        print("Not a valid config file...exiting")
        sys.exit(1)


def main():
    if len(sys.argv) < 3:
        print_usage()

    input_file = sys.argv[1]
    global modem_keys, RSA_D, RSA_N, AES128CBC_IV, AES128CBC_KEY
    sys.argv[2] = sys.argv[2].upper()  # required to be upper case.
    if sys.argv[2] not in modem_keys.keys():
        print("the only version available are : " + modem_keys.keys())
        sys.exit(1)

    keys = modem_keys[sys.argv[2]]
    RSA_D = keys["RSA_D"]
    RSA_N = keys["RSA_N"]
    AES128CBC_IV = keys["AES128CBC_IV"]
    AES128CBC_KEY = keys["AES128CBC_KEY"]

    output_file = "config.xml"

    decrypt_config(input_file, output_file)


if __name__ == "__main__":
    main()