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('--encryption-block-size', type=str, required=True)
  18     parser.add_argument('--openssl-bin', type=str, required=True)
  19     parser.add_argument('--key', type=str, required=True)
  20     parser.add_argument('--iv', type=str, required=True)
  21     args = parser.parse_args()
  22
  23     assert re.match(r'V[0-9]\.[0-9]\.[0-9]\.[0-9]',
  24                     args.version), 'Version must start with Vx.x.x.x'
  25     encryption_block_size = int(args.encryption_block_size, 0)
  26     assert (encryption_block_size > 0 and encryption_block_size % 16 ==
  27             0), 'Encryption block size must be a multiple of the AES block size (16)'
  28
  29     image = open(args.input_file, 'rb').read()
  30     image_enc = []
  31     for i in range(0, len(image), encryption_block_size):
  32         chunk = image[i:i + encryption_block_size]
  33         chunk += b'\x00' * ((-len(chunk)) % 16)  # pad to AES block size (16)
  34         res = subprocess.run([
  35             args.openssl_bin,
  36             'enc',
  37             '-aes-256-cbc',
  38             '-nosalt',
  39             '-nopad',
  40             '-K', args.key,
  41             '-iv', args.iv
  42         ],
  43             check=True, input=chunk, stdout=subprocess.PIPE)
  44         image_enc.append(res.stdout)
  45     image_enc = b''.join(image_enc)
  46
  47     image_with_header = struct.pack(
  48         '>32s32s64s64s64s256s12sII',
  49         args.model.encode('ascii'),
  50         args.region.encode('ascii'),
  51         args.version.encode('ascii'),
  52         b'Thu Jan 1 00:00:00 1970',  # static date for reproducibility
  53         b'',  # reserved
  54         b'',  # RSA signature - omitted for now
  55         b'encrpted_img',
  56         len(image_enc),
  57         encryption_block_size,
  58     ) + image_enc
  59
  60     checksum = zlib.crc32(image_with_header, 0xffffffff) ^ 0xffffffff
  61
  62     with open(args.output_file, 'wb') as outfile:
  63         outfile.write(image_with_header)
  64         outfile.write(struct.pack('>I', checksum))
  65
  66
  67 if __name__ == "__main__":
  68     main()