scripts: support Sercomm crypto

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 <noltari@gmail.com>
This commit is contained in:
Álvaro Fernández Rojas 2020-06-02 08:37:54 +02:00
parent 58bdbe7321
commit 7f1250a7fe
1 changed files with 86 additions and 0 deletions

86
scripts/sercomm-crypto.py Executable file
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#!/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()