No way to trigger fingerprint authentication on lock screen

Bug #1310104 reported by Rüdiger Kupper on 2014-04-19
This bug affects 18 people
Affects Status Importance Assigned to Milestone
lightdm (Ubuntu)

Bug Description

With fprintd/libpam_fprintd installed, the user can in all places authenticate via the fingerprint reader. (Command line, login screen, light locker screen). However, light locker does not interact well with fingerprint authentication:
Immediately after locking the session, the user can unlock via fingerprint. But once the fingerprint authentication times out, light locker waits for a password to be typed, and the user cannot re-initiate fingerprint authentication. The usual way of pressing ESC does not have effect. There even is a state, where light locker does not accept fingerprint nor password authentication -- the user is left without any possibility to unlock the screen. This is not acceptable.
Please correct light locker's behavior with respect to libpam-fprintd authentication.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: light-locker (not installed)
ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Apr 19 23:21:11 2014
EcryptfsInUse: Yes
InstallationDate: Installed on 2012-12-20 (484 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
SourcePackage: light-locker
UpgradeStatus: Upgraded to trusty on 2014-04-18 (1 days ago)

description: updated
Peter de Ridder (cavalier) wrote :

light-locker doesn't handle the authentication. This is handled by lightdm.
What happens it this:
light-locker send a lock signal to lightdm.
lightdm spawns a new X server and starts a lightm greeter in it.
lightdm with the greeter as user interface handle the pam authentication.

affects: light-locker (Ubuntu) → lightdm (Ubuntu)

Thank you for pointing me to the right package.
To specify:
The lock screen behaves differently from the login screen: On the login screen, I can press ESC to re-initiate the login process (i.e., the fingerprint reader will be queried again). On the lock screen, this does *not* work. Once fingerprint authentication has timed out, I cannot get it back. Hence there must be some difference -- the lock screen is *not* a copy of the login greeter with only one user to choose from. (Which is what I understand from your explanation).

I need to correct myself:
- on the login screen (lightdm greeter showing all users), ESC does not re-initiate fingerprint authentication. However, pressing the up/down arrow keys does
- on the lock screen (lightdm greeter showing only one user), pressing the up/down arrow keys naturally does do nothing, so fingerprint authentication cannot be triggered

Hence, there should be a way of triggering fingerprint authentication without the need of selecting another user, for both the login and the lock screen.

summary: - Light locker interacts badly with fingerprint authentication
+ No way to trigger fingerprint authentication on lock screen
Niklas Gidion (nikgid) wrote :

Same behaviour here, just as Rüdiger Kupper described it. I am also affected.
Everything worked beautifully with Ubuntu 13.10.
After the update to Ubuntu 14.04 (via dist-upgrade) the trouble with fprintd and lightdm started for me.
My guess is: every person with a laptop with fingerprint-reader running Ubuntu 14.04 might be affected by this.
What could I do, what files could I provide to help solve this?

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in lightdm (Ubuntu):
status: New → Confirmed
Murz (murznn) wrote :

Confirm, and same problem on Ubuntu 14.10 RC too.

Jens Bo (jb-jens-jb) wrote :

I have the same issue. Not a solution, but a good work around for me was to turn on the onscreen keyboard in the universal access settings.

This leads to a (fallback?) old school login screen which has no problem with the finger print reader.

Changed in lightdm (Ubuntu):
importance: Undecided → Low
Gabriel Boucher (solidgumby) wrote :

Same issue here with 16.04.1

grafviktor (grafviktor) wrote :

Also confirming that 16.04.1 has the same issue. It's actually quite annoying in my case, because usually I never turn off my laptop, but just closing it's lid :-/

I've got the same problem with Ubuntu 16.04.2 LTS on ThinkPad x260
(default installation with Unity and Lightdm)

Had to switch to an alternative implementation "fingerprint-gui" from

The experience is much better.
Specifically, pressing Escape on the Lock screen re-starts the fingerprint authentication.

Same problem in Ubuntu 17.04 on ThinkPad T530, fprintd version 0.7.0-1.

As a note: This bug appeared in Trusty and is still present in Zesty. It is very likely it affects all users using fingerprint readers.

tags: added: utopic xenial zesty
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