I have a setup using pam_time to limit the times when my children can login to GNOME. It works in the sense that if they are not logged in, then when they try to login and the time is not an allowed time, they are refused, but if the time is an allowed time they can log in.
However, the same is not true for the lockscreen. I know that since gnome 3.8 or so the lock screen is just part of gnome shell, and there's no gnome-screensaver. But it seems like the authentication/authorization features of PAM are not being used by the lockscreen. If the kids are logged in, lock the screen, and then come back outside the time window, they can still unlock the screen, whereas if they are logged out, then they can't log in.
This makes me think that the gnome-shell is not using PAM at all for lock screen. Is that true? How can I time-limit the unlock of the lockscreen?