70 lines
1.6 KiB
Python
70 lines
1.6 KiB
Python
#!/usr/bin/env python
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from __future__ import print_function
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import base64
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import hashlib
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import hmac
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import struct
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import sys
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import time
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class TOTP():
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class TOTPException(Exception):
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def __init__(self, msg):
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self.msg = msg
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def __str__(self):
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return repr(self.msg)
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def __init__(self, secret):
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if not secret:
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raise TOTP.TOTPException('Invalid secret')
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self.secret = secret
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def generate(self):
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try:
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key = base64.b32decode(self.secret)
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num = int(time.time()) // 30
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msg = struct.pack('>Q', num)
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# Take a SHA1 HMAC of key and binary-packed time value
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digest = hmac.new(key, msg, hashlib.sha1).digest()
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# Last 4 bits of the digest tells which 4 bytes to use
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offset = ord(digest[19]) & 15
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token_base = digest[offset : offset+4]
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# Unpack that into an integer and strip it down
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token_val = struct.unpack('>I', token_base)[0] & 0x7fffffff
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token_num = token_val % 1000000
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# Pad with leading zeroes
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token = '{0:06d}'.format(token_num)
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return token
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except:
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raise TOTP.TOTPException('Invalid secret')
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def main(args):
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if len(args):
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token = sys.stdin.readline().strip() if args[0] == '-' else args[0]
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elif not sys.stdin.isatty():
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token = sys.stdin.readline().strip()
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else:
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return 'Usage: totp <secret>'
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try:
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print(TOTP(token).generate())
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except TOTP.TOTPException as e:
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return 'Error: ' + e.msg
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if __name__ == '__main__':
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try:
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sys.exit(main(sys.argv[1:]))
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except KeyboardInterrupt:
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sys.exit(1)
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