2FA

#!/usr/bin/python3
import base64, hmac, sys, struct, time

def hotp(key, counter, digits=6, digest='sha1'):
	#Decode the key and add padding if too short
    key = base64.b32decode(key.upper() + '=' * ((8 - len(key)) % 8))
    print("Internal Key:", key)

    #Pack the integer in to a 64 bit integer
    counter = struct.pack('>Q', counter)
    print("Counter:", counter)

    #Use SHA1 HMAC to generate a new mac from the key and the counter
    mac = hmac.new(key, counter, digest).digest()
    print("MAC:", mac)

    #Use the last byte as a offset value
    #This offset value is used as a random starting value
    offset = mac[-1] & 0x0f

    #Get an 32bit integer value form the mac at the correct offset
    print("mac[{}]: {}".format(offset, mac[offset:offset+4]))
    
    #Get the positive part of the integer
    binary = struct.unpack('>L', mac[offset:offset+4])[0] & 0x7fffffff
    print("Binary data" , binary)

    #Take the lower n digits of the number and prepend zeros if needed
    return str(binary)[-digits:].rjust(digits, '0')

def totp(key, time_step=30, digits=6, digest='sha1'):
    return hotp(key, int(time.time() / time_step), digits, digest)

def main():
    #args = [int(x) if x.isdigit() else x for x in sys.argv[1:]]
    #for key in sys.stdin:
    print(totp("MZLXK2LULZ3H2MZYPJYWWS2LFBRXCKC3GBGHUMZDEVUUU4JQIFVQ"))

if __name__ == '__main__':
    main()