There has a been a similar question, but that's not exactly what I want.
I'd like to know if there is a plugin, or add-on, for lightdm or gdm that allows me to authenticate using my password AND google authenticator. I'm talking about entering your GA code into the desktop login — both GUI or command line, shell login — in order to gain access to your local desktop.
Best Answer
Take a look at this blog post titled: Google Two-Step Authentication On Your Desktop What is it?
Installation
Usage
According to the blog post there's a version of lightdm-kde that has the 2 factor authentication included which can take advantage of Google Authenticator when you add the included PAM module into your environment.
Resulting in your GUI logins looking like this:
source here