From 7f1250a7fea716a13c1678a14dbc417ff57e461f Mon Sep 17 00:00:00 2001 From: =?utf8?q?=C3=81lvaro=20Fern=C3=A1ndez=20Rojas?= Date: Tue, 2 Jun 2020 08:37:54 +0200 Subject: [PATCH] scripts: support Sercomm crypto MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Sercomm firmwares are encrypted with AES 256 CBC. The key is generated with a custom algorithm from the firmware tag: char key[32]; char version[32]; char iv[32]; char random[32]; char size[32]; Key must be generated with Sercomm's algorithm. However, the rest of the header can be empty. IV and random are set to 0 on purpose. Signed-off-by: Álvaro Fernández Rojas --- scripts/sercomm-crypto.py | 86 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100755 scripts/sercomm-crypto.py diff --git a/scripts/sercomm-crypto.py b/scripts/sercomm-crypto.py new file mode 100755 index 0000000000..bed3e494b6 --- /dev/null +++ b/scripts/sercomm-crypto.py @@ -0,0 +1,86 @@ +#!/usr/bin/env python3 + +import argparse +import binascii +import hashlib +import os +import struct + +def create_header(key, version, iv, random, size): + header = struct.pack('32s32s32s32s32s', key, version, iv, random, size) + + return header + +def create_output(args): + in_st = os.stat(args.input_file) + in_size = in_st.st_size + + key = "".encode('ascii') + version = args.version.encode('ascii') + iv = "".encode('ascii') + random = "".encode('ascii') + size = str(in_size).encode('ascii') + header = create_header(key, version, iv, random, size) + + out_f = open(args.output_file, 'w+b') + out_f.write(header) + out_f.close() + + md5 = hashlib.md5() + md5.update(header[0x60:0x80]) + md5.update(header[0x20:0x40]) + md5_1 = md5.digest() + + md5 = hashlib.md5() + md5.update(header[0x80:0xA0]) + md5.update(header[0x20:0x40]) + md5_2 = md5.digest() + + key = md5_1 + md5_2 + + key_f = open(args.key_file, 'w+b') + key_f.write(binascii.hexlify(bytearray(key))) + key_f.close() + + print("AES 256 CBC Key:", binascii.hexlify(bytearray(key))) + +def main(): + global args + + parser = argparse.ArgumentParser(description='') + + parser.add_argument('--input-file', + dest='input_file', + action='store', + type=str, + help='Input file') + + parser.add_argument('--key-file', + dest='key_file', + action='store', + type=str, + help='AES 256 CBC Key File') + + parser.add_argument('--output-file', + dest='output_file', + action='store', + type=str, + help='Output file') + + parser.add_argument('--version', + dest='version', + action='store', + type=str, + help='Version') + + args = parser.parse_args() + + if ((not args.input_file) or + (not args.key_file) or + (not args.output_file) or + (not args.version)): + parser.print_help() + + create_output(args) + +main() -- 2.30.2