Recent update to kallet pam prevents groups from being set correctly via lightdm

[Darragh Bailey]

It appears a recent update to Pam KWallet has resulted in groups not being set correctly when logging into my Ubuntu 16.04 system.

$ lsb_release -rd
Description: Ubuntu 16.04.5 LTS
Release: 16.04

$ apt-cache policy libpam-kwallet5
libpam-kwallet5:
  Installed: 4:5.5.5-0ubuntu1.3
  Candidate: 4:5.5.5-0ubuntu1.3
  Version table:
 *** 4:5.5.5-0ubuntu1.3 500
        500 http://ie.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/universe amd64 Packages
        100 /var/lib/dpkg/status
     4:5.5.5-0ubuntu1 500
        500 http://ie.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages

Expected Results:
Upon login to gnome3 shell within a terminal started I should be able to see all of my domain groups (via Winbind/Samba) and local groups when I run 'groups'

Actual Results:
I only see my default group returned

Other info:

On my broken system, performing 'cat /proc/$$/status' to inspect groups, and then replacing the '$$' with the value from ppid, I trace upwards 'bash' -> 'gnome-terminal-' -> 'upstart' -> 'lightdm' -> 'lightdm'

I discover that the parent 'lightdm' contains all of groups, but the child 'lightdm' is empty.

On a working system, the 'lightdm' parent process has it's groups empty, while the child 'lightdm' process contains all of the expected groups as do all of the subsequent child processes.

Testing login via console (Alt + F1) results in groups being set correctly, as does login over SSH, so it appears to be an issue between lightdm and kwallet.

Looking around the internet I found https://unix.stackexchange.com/questions/454593/groups-not-registering-in-x and following the suggestion I disabled pam_kwallet4.so and pam_kwallet5.so in /etc/pam.d/lightdm and rebooted and groups were now correctly passed down to the child process as expected.