[LightDM] Guest logins and PAM

[Veli-Matti Lintu]

Hi,

I've been going through lightdm's guest login flow to find a place where I could initialise sessions for normal logins and guest sessions the same way. This includes creating some directories and files as root and setting some env variables. So far I've been using pam_env.so and pam_exec.so to call the scripts in various stages of the PAM stack. Some of these are called also for ssh logins, so PAM has been a natural place for these.

lightdm uses a separate PAM stacks for normal and autologins, but it seems to bypass PAM completely for guest logins. What is the background for this? Would it be possible to add PAM support for guest logins? I'm not yet familiar enough with the code to say this myself. I'm about to start digging into the code better, but having some pointers would be really nice.

Thanks,

Veli-Matti