gKFxSWGf

1import base64
2from Crypto.Cipher import AES
3from Crypto import Random
4
5secret_key = "abcdefghijklmnop" # not the real one =)
6
7#real version of this would do a database lookup
8#another user might be "admin" or "user2"
9def validate_credentials(user, password):
10    if user == "user1" and password == "asdf":
11        return True
12    else:
13        return False
14
15def pad(partial_block):
16    pad_length = AES.block_size - len(partial_block) % AES.block_size
17    if pad_length == 0:
18        pad_length = AES.block_size
19    return partial_block + chr(pad_length) * pad_length
20
21def unpad(decrypted_data):
22    pad_length = ord(decrypted_data[-1])
23    return decrypted_data[:-pad_length]
24
25# login authenticates the user with their password.
26#
27# Upon success, it creates an authentication token intended for the user
28# to pass with subsequent requests that require authentication.
29def login(user, password):
30    if not validate_credentials(user, password):
31        return ""
32
33    iv = Random.new().read(AES.block_size)
34    cipher = AES.new(secret_key, AES.MODE_CBC, iv )
35
36    encrypted_user = cipher.encrypt(pad(user))
37    return base64.b64encode(iv + encrypted_user)
38
39# get_user is used to extract the authenticated user name from a valid token
40def get_user(auth_token):
41    auth_token = base64.b64decode(auth_token)
42
43    iv = auth_token[:AES.block_size]
44    cipher = AES.new(secret_key, AES.MODE_CBC, iv )
45
46    decrypted_user = cipher.decrypt(auth_token[AES.block_size:])
47    return unpad(decrypted_user)
48
49def main():
50
51    token = raw_input("Do you have a token? (y/n)\n")
52
53    if token == "y":
54        ciphertext = raw_input("token?\n")
55
56        user = get_user(ciphertext)
57
58        print "You are logged in as", user
59    else:    
60        user = raw_input("user?\n")
61        password = raw_input("password?\n")
62
63        token = login(user, password)
64
65        if not token:
66            print "Wrong credentials\n"
67        else:
68            print "Success. here's your token:"
69            print token
70
71if __name__ == "__main__":
72    main()