By default GDM switches to smartcard mode once one is plugged in,
smartcard auth can be disabled at gdm level though, by changing the
gsettings.


sudo -u gdm env -u XDG_RUNTIME_DIR -u DISPLAY DCONF_PROFILE=gdm 
dbus-run-session \
  gsettings set org.gnome.login-screen enable-smartcard-authentication false

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https://bugs.launchpad.net/bugs/1933027

Title:
  Gdm3 with smartcard asks for login/smartcard pin even if there is no
  smartcard authentication enabled

Status in gdm3 package in Ubuntu:
  Confirmed
Status in gnome-shell package in Ubuntu:
  Confirmed

Bug description:
  I use my Ubuntu PC with Yubikey almost always plugged in. It provides
  several security token interfaces, such as U2F, GPG smartcard,
  proprieritary Yubico interfaces (of which I mostly use TOTP codes),
  and also PIV smartcard. However, I haven't configured a PIV smartcard
  on it.

  Whenever I login into the system having Yubikey plugged in, I'm prompted for 
login name, and then for PIN for some smartcard while also being asked to plug 
in one. This is very misleading on several layers:
  1. I have the device providing smartcard plugged id,
  2. But it's not the smartcard GDM would think it is as it's not configured 
properly,
  3. There are no local smartcard-authenticating users right now in the system,
  3. There are no remote authentication systems configured on the system (so no 
ActiveDirectory-smartcard logins or such).

  If I unplug the token UX goes back on old good track.

  Given the circumstances above, I'd consider that GDM (and, on my bet,
  any PAM configuration it uses) shouldn't offer to login using
  smartcard if there is no way to actually do so. I feel something is
  off here, so I'm reporting a bug. It could be an upstream problem
  though; it also could be an upstream SSSD problem, or all combined.

  I believe there is a more clear user experience:
  1. GDM should display users that can login into the system, as it always does 
(if configured). It may also provide entering other login name (also if 
configured). This is GDM usually does without smartcards altogether.
  2. When user is chosen (from the list or manually typed in), check can this 
user even authenticate with smartcards (i.e. if any of available smartcards is 
actually recognised for this user). If so, then ask for PIN. Else, don't show 
anything about smartcards at all (this includes when SSSD is not configured for 
any AD or related and this user has no local smartcard configuration). This can 
switch there & back based on device events.
  I've seen other OS doing this.

  Ubuntu/Gnome session doesn't ask me for PIN for a smartcard on a lock
  screen, so I guess it doesn't support it at all or correctly finds out
  it can't be used. Even more, I couldn't find a way to actually add my
  smartcard as a local login method.

  ProblemType: Bug
  DistroRelease: Ubuntu 21.04
  Package: gdm3 3.38.2.1-2ubuntu1
  ProcVersionSignature: Ubuntu 5.11.0-18.19-generic 5.11.17
  Uname: Linux 5.11.0-18-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.11-0ubuntu65.1
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CurrentDesktop: ubuntu:GNOME
  Date: Sun Jun 20 14:02:02 2021
  InstallationDate: Installed on 2017-03-05 (1567 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 
(20160420.1)
  ProcEnviron:
   TERM=tmux-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=ru_RU.UTF-8
   SHELL=/bin/bash
  SourcePackage: gdm3
  UpgradeStatus: Upgraded to hirsute on 2021-05-13 (37 days ago)

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