Implementation of the OTP algorithm described at http://motp.sourceforge.net in Python. Supports reading secret and PIN from the command-line or from a config file. Allows to paste the generated token to the system's clipboard directly.

otp.py

#!/usr/bin/env python3
#
# Copyright 2019 Sascha Peilicke <sascha@peilicke.de>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Implementation of the "Mobile" OTP algorithm using secret and PIN
as described at http://motp.sourceforge.net

The config file is a regular INI file, just add the following contents

   [my-conf]
   secret=abcdfedfg
   pin=1234

And invoke the script with `otp --config my-conf`, to avoid pasting
secret and PIN on the command-line.
"""

import argparse
import hashlib
import math
import os.path
import sys
import time

CONFIG_FILE = os.path.expanduser("~/.otprc")


def get_one_time_password(secret: str, pin: str):
    timestamp = int(math.floor(time.time() / 10))
    frob = str(timestamp) + secret + pin
    m = hashlib.md5()
    m.update(bytes(frob, "utf-8"))
    return m.hexdigest()[:6]


def copy_to_clipboard(token: str):
    from tkinter import Tk
    t = Tk()
    t.withdraw()
    t.clipboard_clear()
    t.clipboard_append(token)
    t.update()


def load_credentials_from(config_file: str, env: str):
    import configparser
    config = configparser.ConfigParser()
    config.read(config_file)
    secret = config[env]["secret"]
    pin = config[env]["pin"]
    return secret, pin


def main():
    parser = argparse.ArgumentParser(prog="otp",
                                     description="generates an OTP token using secret and PIN as described at "
                                                 "http://motp.sourceforge.net")
    parser.add_argument("--secret", help="secret (16 characters)")
    parser.add_argument("--pin", help="PIN (4 digits)")
    parser.add_argument("--config", help="load secret and pin from {} instead".format(CONFIG_FILE))
    parser.add_argument("--clipboard", action="store_true", help="copy generated token to clipboard")
    parser.add_argument("-v", "--verbose", action="store_true", help="Verbosity level (-v or -vv)")
    args = parser.parse_args()

    if (not args.secret or not args.pin) and not args.config:
        print("please provide either '--secret' and '--pin' or '--config'")
        parser.print_help()
        sys.exit(1)
    if args.config:
        if not os.path.isfile(CONFIG_FILE):
            print("please create configuration file '{}' first".format(CONFIG_FILE))
            sys.exit(1)
        if args.verbose:
            print("loading secret and PIN from '{}'...".format(CONFIG_FILE))
        args.secret, args.pin = load_credentials_from(CONFIG_FILE, args.config)

    token = get_one_time_password(args.secret, args.pin)
    if args.clipboard:
        copy_to_clipboard(token)
    else:
        print(token)


if __name__ == "__main__":
    sys.exit(main())

Ideally, save this file to ~/bin/otp or /usr/local/bin/otp and invoke it either like this:

otp --secret foo --pin 1234 --clipboard

or like this:

otp --config my-config

To get help: otp --help

Note: if you're using macOS Catalina make sure you install Python 3.8 (not available in homebrew yet) to prevent errors with Tkinter