[Bug 2060676] [NEW] [SRU] login: remove pam_lastlog.so from config

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Tim Andersson (andersson123):

[ Impact ]

 * The following line has been found in users logs when trying to log in to their systems:
   login[2449]: PAM unable to dlopen(pam_lastlog.so): /usr/lib/security/pam_lastlog.so: cannot open shared object file: No such file or directory
   This is the only known occurrence of the log. It occurs when users log in to their systems using a tty, or rather referred to as the 'login' method in shadow/pam etc. This log error message is not present when logging in via ssh, gdm, xdm, or other login methods, as they do not depend on the lastlog binary.

 * The upload fixes the issue by dropping pam_lastlog.so from all
config, as well as not installing the lastlog binary.

[ Test Plan ]

```
wget https://releases.ubuntu.com/noble/ubuntu-24.04.1-desktop-amd64.iso
qemu-system-x86_64 -boot d -cdrom /path/to/ubuntu-24.04.1-desktop-amd64.iso -m 8192M -smp 2 -hda /tmp/yarf-vm.qcow2 -enable-kvm -device qxl
# install the system, and reboot
# at the login screen post-reboot, press ctrl+alt+f2
# login via tty
journalctl -b 0 --no-pager | grep pam_lastlog.so
# and you will see the error message
sudo sed '/session    optional     pam_lastlog.so/d' /etc/pam.d/login
# logout
# log back in via tty
journalctl  # check the logs since you logged in, you will not see any mention of pam_lastlog.so
```

 * In order to test this after the fix lands in noble proposed, do the
same as above, except instead of manuall removing the entry from
/etc/pam.d/login, install the version of shadow from proposed, and
assert that the log messages are no longer present.

[ Where problems could occur ]

 * It seems extremely improbable anyone would configure login.pam to
explicitly *require* pam_lastlog.so, I also can't imagine anyone would
create any functionality that'd explicitly *depend* on pam_lastlog.so
being *required*.

[ Other Info ]

 * the pam_lastlog.so binary was dropped in shadow/1:4.13+dfsg1-5.
Included in this change also is dropping pam_lastlog.so from
debian/login.pam.

 * The version of shadow in oracular is 1:4.15.3-3ubuntu2, and thus this
error message isn't present in oracular onwards.

 * We absolutely *cannot* re-introduce pam_lastlog.so as it was dropped
as part of the time_t transition, see commit: https://github.com/linux-
pam/linux-pam/commit/357a4ddbe9b4b10ebd805d2af3e32f3ead5b8816

 * pam_lastlog2 is depended upon in util-linux after version 2.40-7. We
can make changes in shadow going forward that depends on pam_lastlog2
rather than pam_lastlog. But that's not really relevant to the SRU I
guess. These changes are planned to be implemented upstream
https://bugs.debian.org/cgi-bin/bugreport.cgi?att=0;bug=1068229;msg=39,
so likely from Ubuntu's side, we can just wait for the changes.

 * However, upstream, shadow still doesn't have any mention of lastlog2
in debian/login.pam. So we can't SRU a change to depend on this new
lastlog binary, as it's not in devel yet.

 * We could, however, SRU a change wherein we revert the dropping of
pam_lastlog.so in shadow, but this is more involved and would likely be
a separate SRU, wherein either that SRU or this one lands.

[Original description]

Imported from Debian bug http://bugs.debian.org/1068229:

Package: libpam-modules
Version: 1.5.3-6
Severity: normal

I noticed the following line in my logs:

login[2449]: PAM unable to dlopen(pam_lastlog.so):
/usr/lib/security/pam_lastlog.so: cannot open shared object file: No
such file or directory

I looked in the deb files from snapshot.debian.org, and noticed the last version
that had it was 1.5.2-9.1 - starting from 1.5.3-1 it disappeared.

Maybe it's fallout from the time_t transition and you're already aware of it, in
which case feel free to close.

Thanks,

-- M

-- System Information:
Debian Release: trixie/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, arm64

Kernel: Linux 6.7.9-amd64 (SMP w/4 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libpam-modules depends on:
ii  debconf [debconf-2.0]  1.5.86
ii  libaudit1              1:3.1.2-2.1
ii  libc6                  2.37-15.1
ii  libcrypt1              1:4.4.36-4
ii  libpam-modules-bin     1.5.3-6
ii  libpam0g               1.5.3-6
ii  libselinux1            3.5-2
ii  libsystemd0            255.4-1+b1

libpam-modules recommends no packages.

libpam-modules suggests no packages.

-- debconf information excluded

** Affects: shadow (Ubuntu)
     Importance: Medium
         Status: Fix Released

** Affects: shadow (Ubuntu Noble)
     Importance: Undecided
     Assignee: Tim Andersson (andersson123)
         Status: In Progress

** Affects: shadow (Ubuntu Oracular)
     Importance: Medium
         Status: Fix Released

** Affects: shadow (Debian)
     Importance: Unknown
         Status: Fix Released


** Tags: block-proposed-noble foundations-todo
-- 
[SRU] login: remove pam_lastlog.so from config
https://bugs.launchpad.net/bugs/2060676
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