60 lines
1.4 KiB
Python
60 lines
1.4 KiB
Python
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import sys
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import os
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import re
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class DecodeError(ValueError):
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pass
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ESCAPE_RE = re.compile(br'--|-([A-F0-9]{2})')
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def decode_part(part):
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if not re.match(r'^[a-zA-Z0-9._-]*$', part):
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raise DecodeError('illegal characters found')
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part = part.encode('ascii')
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# Check if no '-' remains outside of legal escape sequences.
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if b'-' in ESCAPE_RE.sub(b'', part):
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raise DecodeError("'-' can be used only in '-HH' or '--'")
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def convert(m):
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if m.group(0) == b'--':
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return b'-'
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num = int(m.group(1), 16)
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return bytes([num])
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return ESCAPE_RE.sub(convert, part)
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def decode(arg):
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'''
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Decode the argument for executing. The format is as follows:
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- individual parts are split by '+'
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- bytes are escaped as '-HH' (where HH is hex code, capital letters only)
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- literal '-' is encoded as '--'
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- otherwise, only [a-zA-Z0-9._] are allowed
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:param arg: argument, as a string
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:returns: list of exec arguments (each as bytes)
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'''
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return [decode_part(part) for part in arg.split('+')]
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def main(argv=sys.argv):
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if len(argv) != 2:
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print('This service requires exactly one argument', file=sys.stderr)
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exit(1)
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try:
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command = decode(argv[1])
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except DecodeError as e:
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print('Decode error: {}'.format(e), file=sys.stderr)
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exit(1)
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os.execvp(command[0], command)
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if __name__ == '__main__':
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main()
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