Security Audit Request for Screenlocker Branch

Martin Gräßlin mgraesslin at
Wed Oct 12 11:10:48 BST 2011

On Wednesday 12 October 2011 09:10:40 Oswald Buddenhagen wrote:
> > Of course KWin is a more complex application than others, but given
> > what we need in a screen locker the difference becomes marginal IMHO.
> yes. one should consider decoupling the greeter from the core engine.
> > > > I myself have never run into a situation where KWin did not restart
> > > > [...]
> > > 
> > > even if it restarts, you still have a non-trivial racing window.
> > > additionally, it probably allows a waiting app (some popup) to grab
> > > input and thus make the subsequent re-lock fail.
> > 
> > ok, this is a concern I have not yet considered. Any ideas how we could
> > handle such a situation?
> by not crashing in the first place. seriously. think about it.
ok I have been thinking about it and have a new proposal:
* writing a kded module to only handle the screen locking (grab keyboard and 
* having greeter in a separate process, so that the kded module can restart 
the greeter in case it crashes
* use xproperty on all greeter windows to inform the compositor which windows 
belong to it
* use a kwin effect to additionally ensure that the screen is blanked and 
nothing gets above the greeter windows


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