Bug#1027134: lightdm-autologin-greeter: greeter fails with error "autologin not configured"

[Farblos]

Package: lightdm-autologin-greeter
Version: 1.0-5
Severity: normal
X-Debbugs-Cc: in.cognito35 at arcor.de

Dear Maintainer,

   * What led up to the situation?

Installed lightdm and lightdm-autlogin-greeter, configured as follows:

-------------------- snip --------------------
[~]$ sudo lightdm --show-config
   [Seat:*]
B  greeter-session=lightdm-autologin-greeter
A  greeter-hide-users=true
A  session-wrapper=/etc/X11/Xsession
B  user-session=lightdm-xsession
D  autologin-user-timeout=0
D  autologin-user=farblos

Sources:
A  /usr/share/lightdm/lightdm.conf.d/01_debian.conf
B  /usr/share/lightdm/lightdm.conf.d/60-lightdm-autologin-greeter.conf
C  /etc/lightdm/lightdm.conf.d/lightdm-autologin-greeter.conf
D  /etc/lightdm/lightdm.conf
-------------------- snip --------------------

In addition, ensured that the user in question is part of group
autologin, since that is documented as requirement in a few
places:

-------------------- snip --------------------
[~]$ id farblos
uid=1000(farblos) gid=1000(farblos) groups=1000(farblos),4(adm),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev),101(systemd-journal),108(netdev),110(bluetooth),115(_cvsadmin),996(autologin)
-------------------- snip --------------------

Even though that does not make a difference: The issue described
here occurs with and without user farblos being in group
autologin.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

Rebooted, waited for the first lightdm session to come up, exited
the lightdm session to start a fresh one.

   * What was the outcome of this action?

According to the logs, the auto-login greeter fails to do its
job:

-------------------- snip --------------------
[...]
Traceback (most recent call last):
  File "/usr/lib/lightdm-autologin-greeter/lightdm-autologin-greeter", line 53, in <module>
    greeter.authenticate_autologin()
gi.repository.GLib.GError: lightdm_greeter_error: Can't authenticate autologin; autologin not configured (3)
-------------------- snip --------------------

Accordingly, lightdm errors out on the greeter and restarts
instead of simply starting a new session:

-------------------- snip --------------------
[+109.16s] DEBUG: Activating VT 7
[+109.16s] DEBUG: Activating login1 session c1
[+109.16s] DEBUG: Seat seat0 changes active session to c1
[+109.16s] DEBUG: Session c1 is already active
[+109.19s] DEBUG: Greeter connected version=1.26.0 api=1 resettable=false
[+109.20s] DEBUG: Greeter closed communication channel
[+109.20s] DEBUG: Session pid=1987: Exited with return value 1
[+109.20s] DEBUG: Seat seat0: Session stopped
[+109.20s] DEBUG: Seat seat0: Stopping; failed to start a greeter
[+109.20s] DEBUG: Seat seat0: Stopping
[+109.20s] DEBUG: Seat seat0: Stopping display server
[+109.20s] DEBUG: Sending signal 15 to process 1953
[+109.20s] DEBUG: Seat seat0 changes active session to
[+109.48s] DEBUG: Process 1953 exited with return value 0
[+109.48s] DEBUG: XServer 0: X server stopped
[+109.48s] DEBUG: Releasing VT 7
[+109.48s] DEBUG: XServer 0: Removing X server authority /var/run/lightdm/root/:0
[+109.48s] DEBUG: Seat seat0: Display server stopped
[+109.48s] DEBUG: Seat seat0: Stopped
[+109.48s] DEBUG: Required seat has stopped
[+109.48s] DEBUG: Stopping display manager
[+109.48s] DEBUG: Display manager stopped
[+109.48s] DEBUG: Stopping daemon
[+109.48s] DEBUG: Exiting with return value 1
-------------------- snip --------------------

systemd catches the exit and restarts the service:

-------------------- snip --------------------
Dec 28 10:57:04 sappc1 systemd[1]: lightdm.service: Main process exited, code=exited, status=1/FAILURE
Dec 28 10:57:04 sappc1 systemd[1]: lightdm.service: Failed with result 'exit-code'.
Dec 28 10:57:04 sappc1 systemd[1]: lightdm.service: Consumed 1.019s CPU time.
Dec 28 10:57:04 sappc1 systemd[1]: lightdm.service: Scheduled restart job, restart counter is at 1.
Dec 28 10:57:04 sappc1 systemd[1]: Stopped Light Display Manager.
Dec 28 10:57:04 sappc1 systemd[1]: lightdm.service: Consumed 1.019s CPU time.
Dec 28 10:57:04 sappc1 systemd[1]: Starting Light Display Manager...
Dec 28 10:57:04 sappc1 systemd[1]: Started Light Display Manager.
-------------------- snip --------------------

Of course, the overall effect is the same: A new session is
started and auto-logged-in, but I think not in the intended way.
(The same effect could be probably achieved by using /bin/false
as greeter.)

   * What outcome did you expect instead?

lightdm would just start another session without exiting.

-- System Information:
Debian Release: bookworm/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 6.0.0-4-amd64 (SMP w/16 CPU threads; PREEMPT)
Kernel taint flags: TAINT_USER
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages lightdm-autologin-greeter depends on:
ii  gir1.2-lightdm-1        1.26.0-8
ii  liblightdm-gobject-1-0  1.26.0-8
ii  lightdm                 1.26.0-8
ii  python3                 3.10.6-1
ii  python3-gi              3.42.2-3

lightdm-autologin-greeter recommends no packages.

lightdm-autologin-greeter suggests no packages.

-- no debconf information