Use one of many second factors authentication on PAM

[André Rodier <andre@rodier.me>]

Hello all,

I have been able to configure pam on Linux, to add two factors 
authentication for session, sudo, etc...

First, I tried Google authenticator and a code from my phone, and it is 
working like a charm.

Then, I commented out the google-authenticator entry, and tried a U2F 
key. Again, this is working very well, and the light blink after I type 
the password.

Same for a Yubikey, working like a charm, and I even have a clue message 
on GDM "Please touch your device".

Now, I would like to achieve the following:

- Having my password as the first authentication, of course mandatory.
- Then, being able to use one of my second authentication device.

This is basically what we have on Google, for instance.

Any idea ?

Thanks for your answers.

𝓐𝓡 - André Rodier.