Bug 353440

Summary:	Can't unlock session - password is always wrong
Product:	[Unmaintained] kscreenlocker	Reporter:	Gauthier POGAM--LE MONTAGNER <gplm+kde>
Component:	kcheckpass	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED DOWNSTREAM
Severity:	grave	CC:	bshah, faure, gplm+kde, mgraesslin, rygyhy
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Exherbo
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Gauthier POGAM--LE MONTAGNER 2015-10-02 08:52:06 UTC

When the screen is locked (with shortcut or automatically), it is impossible to unlock the session.

The lockscreen always consider the password as wrong (and the problem doesn't come from the password as I tried with "ff" as password). Empty password doesn't work too.

The only solution is to kill all the graphic stuff or to reboot to unlock the screen (it caused lost of data multiple times - not saved stuff or files opened in my IDE were just empty when I re-opened them).

Reproducible: Always

Steps to Reproduce:
1. Login on your session
2. Lock the screen using anyway you want
3. Type your password

Actual Results:  
The screen locker doesn't unlock the session and display a message saying the password is wrong.

Expected Results:  
The session should be normally unlocked.

I use a 64-bit machine, on Exherbo with linux 4.2.1.
Everything is compiled from scratch (I recompiled the entire system few days ago).

KDE has been installed using the "plasma-desktop" package (http://git.exherbo.org/summer/packages/kde/plasma-desktop/index.html)
This is my "option.conf" file : http://paste.pound-python.org/show/FQx3hBX0sJwR3jnLJbrq/
For the rest, only default parameters where used (as provided by Exherbo package maintainer).

I use SDDM as lockscreen. No special parameters are used, and the problem is present since the beginning of the installation (few weeks ago).

Comment 1 Ry 2015-10-06 06:06:20 UTC

I've had the same experience on openSUSE 13.2 after moving to Tumbleweed (KDE 5/kernel 4.1.x).
This has been resolved for me by changing the attributes of kcheckpass:
sudo chmod u+s /usr/lib64/libexec/kcheckpass
This had been reported to work in other forums.

Comment 2 Martin Flöser 2015-12-15 17:34:41 UTC

@Gauthier: could you please test with changing the suid on kcheckpass?

Please note that this is the default which just does not get applied by distributions. If the problem is not resolved with changing as suggested, please reopen.

Comment 3 David Faure 2016-05-13 23:18:52 UTC

For the record, on OpenSuSE, making kcheckpass suid root is not enough, one should also make sure to compile kscreenlocker and plasma-workspace with the cmake options
-DKDE4_COMMON_PAM_SERVICE=xdm -DKDE4_KCHECKPASS_PAM_SERVICE=xdm
(yes, "KDE4", even in the KF5 version)