scripts/netgear-encrypted-factory.py

   1 #!/usr/bin/env python3
   2
   3 import argparse
   4 import re
   5 import struct
   6 import subprocess
   7 import zlib
   8
   9
  10 def main():
  11     parser = argparse.ArgumentParser()
  12     parser.add_argument('--input-file', type=str, required=True)
  13     parser.add_argument('--output-file', type=str, required=True)
  14     parser.add_argument('--model', type=str, required=True)
  15     parser.add_argument('--region', type=str, required=True)
  16     parser.add_argument('--version', type=str, required=True)
  17     parser.add_argument('--hw-id-list', type=str)
  18     parser.add_argument('--model-list', type=str)
  19     parser.add_argument('--encryption-block-size', type=str, required=True)
  20     parser.add_argument('--openssl-bin', type=str, required=True)
  21     parser.add_argument('--key', type=str, required=True)
  22     parser.add_argument('--iv', type=str, required=True)
  23     args = parser.parse_args()
  24
  25     assert re.match(r'V[0-9]\.[0-9]\.[0-9]\.[0-9]',
  26                     args.version), 'Version must start with Vx.x.x.x'
  27     encryption_block_size = int(args.encryption_block_size, 0)
  28     assert (encryption_block_size > 0 and encryption_block_size % 16 ==
  29             0), 'Encryption block size must be a multiple of the AES block size (16)'
  30
  31     hw_id_list = args.hw_id_list.split(';') if args.hw_id_list else []
  32     model_list = args.model_list.split(';') if args.model_list else []
  33     hw_info = ';'.join(hw_id_list + model_list)
  34
  35     image = open(args.input_file, 'rb').read()
  36     image_enc = []
  37     for i in range(0, len(image), encryption_block_size):
  38         chunk = image[i:i + encryption_block_size]
  39         chunk += b'\x00' * ((-len(chunk)) % 16)  # pad to AES block size (16)
  40         res = subprocess.run([
  41             args.openssl_bin,
  42             'enc',
  43             '-aes-256-cbc',
  44             '-nosalt',
  45             '-nopad',
  46             '-K', args.key,
  47             '-iv', args.iv
  48         ],
  49             check=True, input=chunk, stdout=subprocess.PIPE)
  50         image_enc.append(res.stdout)
  51     image_enc = b''.join(image_enc)
  52
  53     image_with_header = struct.pack(
  54         '>32s32s64s64sIBBB13s200s100s12sII',
  55         args.model.encode('ascii'),
  56         args.region.encode('ascii'),
  57         args.version.encode('ascii'),
  58         b'Thu Jan 1 00:00:00 1970',  # static date for reproducibility
  59         0,  # product hw model
  60         0,  # model index
  61         len(hw_id_list),
  62         len(model_list),
  63         b'',  # reserved
  64         hw_info.encode('ascii'),
  65         b'',  # reserved
  66         b'encrpted_img',
  67         len(image_enc),
  68         encryption_block_size,
  69     ) + image_enc
  70
  71     checksum = zlib.crc32(image_with_header, 0xffffffff) ^ 0xffffffff
  72
  73     with open(args.output_file, 'wb') as outfile:
  74         outfile.write(image_with_header)
  75         outfile.write(struct.pack('>I', checksum))
  76
  77
  78 if __name__ == "__main__":
  79     main()