54 lines
1.2 KiB
Python
Executable File
54 lines
1.2 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# Option ROM signing utility
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#
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# Authors:
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# Jan Kiszka <jan.kiszka@siemens.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2 or later.
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# See the COPYING file in the top-level directory.
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import sys
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import struct
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if len(sys.argv) < 3:
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print('usage: signrom.py input output')
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sys.exit(1)
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fin = open(sys.argv[1], 'rb')
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fout = open(sys.argv[2], 'wb')
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magic = fin.read(2)
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if magic != b'\x55\xaa':
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sys.exit("%s: option ROM does not begin with magic 55 aa" % sys.argv[1])
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size_byte = ord(fin.read(1))
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fin.seek(0)
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data = fin.read()
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size = size_byte * 512
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if len(data) > size:
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sys.stderr.write('error: ROM is too large (%d > %d)\n' % (len(data), size))
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sys.exit(1)
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elif len(data) < size:
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# Add padding if necessary, rounding the whole input to a multiple of
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# 512 bytes according to the third byte of the input.
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# size-1 because a final byte is added below to store the checksum.
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data = data.ljust(size-1, b'\0')
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else:
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if ord(data[-1:]) != 0:
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sys.stderr.write('WARNING: ROM includes nonzero checksum\n')
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data = data[:size-1]
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fout.write(data)
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checksum = 0
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for b in data:
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checksum = (checksum - b) & 255
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fout.write(struct.pack('B', checksum))
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fin.close()
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fout.close()
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