2fa.py

from base64 import b32decode
from hashlib import sha1
from hmac import new as hmac_new
from struct import pack, unpack
from time import time


def generate_totp(secretKey: str, timeWindow: int = 30, digitCount: int = 6) -> str:
    secretKey = secretKey.strip().replace(" ", "").upper()
    while len(secretKey) % 8:
        secretKey += "="

    keyBytes = b32decode(secretKey)

    currentTime = int(time())
    timeCounter = currentTime // timeWindow
    timeBytes = pack(">Q", timeCounter)

    hmacResult = hmac_new(keyBytes, timeBytes, sha1).digest()

    startPosition = hmacResult[-1] & 0x0F
    codeBytes = hmacResult[startPosition : startPosition + 4]

    codeNumber = unpack(">I", codeBytes)[0] & 0x7FFFFFFF
    otpValue = codeNumber % (10**digitCount)

    return str(otpValue).zfill(digitCount)


if __name__ == "__main__":
    userSecret = input("Enter your secret key: ")
    totpCode = generate_totp(userSecret)
    print(f"Your TOTP code: {totpCode}")