Zte configuration file decrypt tool

decrypt_zte.py

#!/usr/bin/env python3

import re
import zlib
import struct
import sys


def extract_config_xml(config_bin):
    '''
    https://reverseengineering.stackexchange.com/a/9246
    '''
    config_xml = b''
    for zlib_chunk in re.finditer(b'\x78\xda', config_bin):
        zlib_chunk_start = zlib_chunk.start()
        zlib_chunk_header = config_bin[zlib_chunk_start - 12: zlib_chunk_start]
        xml_chunk_length, zlib_chunk_length, config_bin_length = \
            struct.unpack('>LLL', zlib_chunk_header)
        if xml_chunk_length == 0x10000 or config_bin_length == 0:
            zlib_chunk_end = zlib_chunk_start + zlib_chunk_length
            zlib_chunk = config_bin[zlib_chunk_start: zlib_chunk_end]
            xml_chunk = zlib.decompress(zlib_chunk)
            assert xml_chunk_length == len(xml_chunk)
            config_xml += xml_chunk
    return config_xml

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print('{} <zte_config> <xml_output>'.format(__file__))
        exit()
    in_file = sys.argv[1]
    out_file = in_file + '.xml'

    with open(in_file, 'rb') as f:
        xml = extract_config_xml(f.read())
        with open(out_file, 'wb') as fo:
            fo.write(xml)