Bug 500694 - Fingerprint reader cannot be used to log in after 30 seconds
Summary: Fingerprint reader cannot be used to log in after 30 seconds
Status: REPORTED
Alias: None
Product: plasmashell
Classification: Plasma
Component: Screen locking (show other bugs)
Version: 6.3.0
Platform: Other Linux
: NOR normal
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords: regression
Depends on:
Blocks:
 
Reported: 2025-02-24 21:22 UTC by sement
Modified: 2025-03-12 13:30 UTC (History)
5 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


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Description sement 2025-02-24 21:22:42 UTC
After a recent upgrade to KDE Plasma 6.3 (early KDE Plasma 6.2), I am having trouble unlocking my computer using the fingerprint reader.

SUMMARY

After locking the screen, unlocking with the fingerprint scanner only works for a few seconds. Earlier on KDE Plasma 6.2, after moving the mouse or pressing any key, it was possible to unlock the screen.
As I mentioned on KDE Plasma 6.3, this works only moments after locking the computer.

STEPS TO REPRODUCE
1.  Just lock screen
2.  Wait 30 secconds
3. 

OBSERVED RESULT

Can not unlock screen with fingerprint.

EXPECTED RESULT

Unlock screen like on KDE Plasma 6.2

SOFTWARE/OS VERSIONS

Linux/KDE Plasma:  Fedora 40 
KDE Plasma Version: 6.3.0 and 6.3.1
KDE Frameworks Version: 
Qt Version: 6.8.2-1

ADDITIONAL INFORMATION

Thinkpad T14 gen4
Comment 1 TraceyC 2025-02-27 01:32:28 UTC
After waiting 30 seconds, and you try to unlock the screen with the fingerprint reader, does the login screen say anything about putting your finger on the reader? Or has that text disappeared?
Comment 2 sement 2025-02-27 10:34:25 UTC
Look on the issue: https://discussion.fedoraproject.org/t/fingerprint-kde-plasma-6-3-problem-with-unlock-computer/144842/7

Lars l-c-g says:

The summary in this bug is something I have observed, too. In Plasma 6.3.x, after locking the screen, the password prompt is displayed immediately and the power LED next to my fingerprint scanner turns from white to green to indicate that it is ready and waiting for me to scan my finger. In Plasma 6.2.x, it would show the lockscreen wallpaper with the current time and only after I hit a key or clicked somewhere would it show my user picture, a password entry field, and fire up the fingerprint scanner.



I will try to describe the problem again, more precisely.

When I manually lock the screen (windows key + L) or automatically, the LED light on my fingerprint reader automatically goes out and the system waits for me to put my finger on it and unlock the screen. If I don't do this, after 30 seconds (maybe less), the reader shuts off and it is no longer possible to unlock the screen with my finger. In KDE 6.2 and lower versions, when I moved the mouse, pressed any key, the screen brightened and the fingerprint reader enabled unlocking anew. As of KDE 6.3 version, the reader is not active.
Comment 3 TraceyC 2025-02-27 17:31:08 UTC
Thanks for those details. I'll let someone more familiar with this functionality take it from here.
Comment 4 TraceyC 2025-03-04 01:07:17 UTC
This sounds like the same problem as https://bugs.kde.org/show_bug.cgi?id=469951 which was opened against 5.27.5
Comment 5 sement 2025-03-05 23:21:43 UTC
(In reply to TraceyC from comment #4)
> This sounds like the same problem as
> https://bugs.kde.org/show_bug.cgi?id=469951 which was opened against 5.27.5

It seems to me that the two problems are different. In my case, it is the lack of repeated ability to unlock the screen with the fingerprint reader after 30 seconds. In that case, there is a problem in scanning the finger too quickly before the user correctly places it on the fingerprint reader.
Comment 6 fhortner 2025-03-12 13:30:48 UTC
I am experiencing the exact same issue under Fedora 41 since I performed the updates on Feb. 8.
Only difference is that I am using an U2F USB Security Key instead of on fingerprint reader.

Since I am using a U2F USB Security Key as  second factor, that is prompting for touching it (blinking LED). Since when I am not on the computer (the reason for the Lock Screen to be activated), the USB Security key always runs into a timeout. And this timeout always results in an unlock failure after I enter the password.
solution so far without spamming the logs with invalid logins: disable U2F. But lets be hones, this is not really the sense of having U2F, is it?

Looks like the underlying issue is this bug:
https://bugs.kde.org/show_bug.cgi?id=499637