Authenticator¶

def __init__(self, secret: str):
    """Creates a new Authenticator instance.
    Args:
      secret (str):
        User secret which is used in generating one
        time password.
    Returns:
      Authenticator instance.
    """

    self._secret = secret
    self.__check_secret(secret)

def create_hmac(self, secret: str, input: float) -> str:
    """Creates the hash value which is used in creating one time password.
    Args:
      secret (str):
        User secret which is used in generating one
        time password.
      input (float):
        The value of current UNIX time divided by 30.
    Returns:
      SHA1 hash value.
    """

    input_str = repr(input).encode("ascii")
    input_hash = hashlib.sha1(secret + input_str).hexdigest().encode("ascii")
    return hashlib.sha1(secret + input_hash).hexdigest()

def current_timestamp(self) -> time:
    """Returns the current UNIX time."""

    return time.time()

def decode_with_base32(self, upper_case_secret: str) -> bytes:
    """Creates a new Base32 decoded value from given string.
    Args:
      upper_case_secret (str):
        User secret which is used in generating one
        time password.
    Returns:
      Base32 decoded value.
    """

    return base64.b32decode(upper_case_secret)

def one_time_password(self, delay_time: float = 30.0) -> str:
    """Creates one time password using secret which must be set in constructor.
    Args:
      delay_time (float):
        Optional time interval for token availability.
    Returns:
      One time password as string.
    """

    secret_without_spaces = self.remove_spaces(self._secret)
    upper_case_secret = self.to_upper_case(secret_without_spaces)
    secret = self.decode_with_base32(upper_case_secret)
    input = self.current_timestamp() / delay_time
    hmac = self.create_hmac(secret, input)
    offset = ord(hmac[len(hmac) - 1]) & 0x0F
    hex_four_characters = binascii.hexlify(hmac[offset : offset + 4].encode())
    password = int(hex_four_characters, 32) % 1000000
    return password

def remove_spaces(self, secret: str) -> str:
    """Removes empty spaces from given string.
    Args:
      secret (str):
        User secret which is used in generating one
        time password.
    Returns:
      String without empty spaces.
    """

    secret_without_spaces = secret.replace(" ", "")
    secret_without_spaces = re.sub(r"\W", "", secret_without_spaces)
    return secret_without_spaces

def to_upper_case(self, secret_without_spaces: str) -> str:
    """Updates given string to uppercase without changing.
    Args:
      secret_without_spaces (str):
        User secret which is used in generating one
        time password.
    Returns:
      String in uppercase.
    """

    return secret_without_spaces.upper()