Re: Use one of many second factors authentication on PAM

[Celejar <celejar@gmail.com>]

On Sun, 14 Nov 2021 17:57:53 +0000
André Rodier <andre@rodier.me> wrote:

> 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 ?

I think you need to look into the details of PAM stacking. See here:

https://unix.stackexchange.com/a/638466

for a discussion of something similar to what you want to do (although you'll have to adapt it
to your specific preferences), and here for more information:

https://developer.ibm.com/tutorials/l-pam/

Celejar