1from __future__ import print_function 2# 3# Option ROM signing utility 4# 5# Authors: 6# Jan Kiszka <jan.kiszka@siemens.com> 7# 8# This work is licensed under the terms of the GNU GPL, version 2 or later. 9# See the COPYING file in the top-level directory. 10 11import sys 12import struct 13 14if len(sys.argv) < 3: 15 print('usage: signrom.py input output') 16 sys.exit(1) 17 18fin = open(sys.argv[1], 'rb') 19fout = open(sys.argv[2], 'wb') 20 21magic = fin.read(2) 22if magic != b'\x55\xaa': 23 sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1]) 24 25size_byte = ord(fin.read(1)) 26fin.seek(0) 27data = fin.read() 28 29size = size_byte * 512 30if len(data) > size: 31 sys.stderr.write('error: ROM is too large (%d > %d)\n' % (len(data), size)) 32 sys.exit(1) 33elif len(data) < size: 34 # Add padding if necessary, rounding the whole input to a multiple of 35 # 512 bytes according to the third byte of the input. 36 # size-1 because a final byte is added below to store the checksum. 37 data = data.ljust(size-1, b'\0') 38else: 39 if ord(data[-1:]) != 0: 40 sys.stderr.write('WARNING: ROM includes nonzero checksum\n') 41 data = data[:size-1] 42 43fout.write(data) 44 45checksum = 0 46for b in data: 47 # catch Python 2 vs. 3 differences 48 if isinstance(b, int): 49 checksum += b 50 else: 51 checksum += ord(b) 52checksum = (256 - checksum) % 256 53 54# Python 3 no longer allows chr(checksum) 55fout.write(struct.pack('B', checksum)) 56 57fin.close() 58fout.close() 59