TOTP module for Python.

totp.py

#!/usr/bin/env python2

""" Implementation of RFC 4226: HMAC-Based One-Time Password Algorithm (HTOP),
and RFC 6238: Time-Based One-Time Password Algorithm (TOTP).
"""
__author__ = 'acoster'
__copyright__ = 'Copyright 2012, Alexandre Coster'
__fixed__ = 'ver 20181001003525 alexx'

import hmac, time, base64, struct, hashlib, sys

def get_hotp(secret, counter):
    while len(secret) % 4 != 0:
        secret = secret[:-1]
    while len(secret) % 8 != 0:
        secret += '='
    secret  = base64.b32decode(secret, casefold=True)
    counter = struct.pack('>Q', counter)
    hash   = hmac.new(secret, counter, hashlib.sha1).digest()
    offset = ord(hash[19]) & 0xF
    return (struct.unpack(">I", hash[offset:offset + 4])[0] & 0x7FFFFFFF) % 1000000

def get_totp(secret):
    return get_hotp(secret, int(time.time()) // 30)

if len(sys.argv) == 2:
    print("{}".format(str(get_totp(sys.argv[1])).rjust(6, '0')))
else:
    print("Usage: totp.py <secret>")