LNhSUzpt

1import time
2import struct
3import hmac
4import hashlib
5import base64
6 
7def authenticate(secret_key, code_attempt):
8    tm = int(time.time() / 30)
9 
10    # try 30 seconds behind and ahead as well
11    for ix in [-1, 0, 1]:
12        # convert timestamp to raw bytes
13        b = struct.pack(">q", tm + ix)
14        
15        if get_code(secret_key, b) == str(code_attempt):
16            return True
17    
18    return False
19    
20def get_code(secret_key, raw_timestamp=None):
21    if raw_timestamp is None:
22        tm = int(time.time() / 30)
23        raw_timestamp = struct.pack(">q", tm)
24    
25    secret_key = base64.b32decode(secret_key)
26    
27    # generate HMAC-SHA1 from timestamp based on secret key
28    hm = hmac.HMAC(secret_key, raw_timestamp, hashlib.sha1).digest()
29
30    # extract 4 bytes from digest based on LSB
31    offset = ord(hm[-1]) & 0x0F
32    truncatedHash = hm[offset:offset+4]
33
34    # get the code from it
35    code = struct.unpack(">L", truncatedHash)[0]
36    code &= 0x7FFFFFFF;
37    code %= 1000000;
38
39    return ("%06d" % code)
40
41if __name__ == "__main__":
42    # debug
43    secret_key = raw_input('Secret Key: ').upper()
44    code = get_code(secret_key)
45    print "Code: %s" % code
46    print "Auth: %s" % authenticate(secret_key, code)