Date: Thu, 19 Jan 2012 17:35:23 -0600 From: Tim Zingelman <tez@...bsd.org> To: oss-security@...ts.openwall.com Subject: Re: Screen locking programs on Xorg 1.11 On Thu, Jan 19, 2012 at 1:18 PM, Florian Weimer <fw@...eb.enyo.de> wrote: >> I recently found out that it is possible to kill a screensaver/screen >> locker program on the latest version of Xorg (1.11 shipped with >> archlinux, debian wheezy..) using the Ctrl+Alt+Multiply key binding. > > This used to be, uhm, common knowledge: > > | Option "AllowDeactivateGrabs" "boolean" > | This option enables the use of the Ctrl+Alt+Keypad-Divide key > | sequence to deactivate any active keyboard and mouse > | grabs. Default: off. > | > | Option "AllowClosedownGrabs" "boolean" > | This option enables the use of the Ctrl+Alt+Keypad-Multiply key > | sequence to kill clients with an active keyboard or mouse grab as > | well as killing any application that may have locked the server, > | normally using the XGrabServer(3x) Xlib function. Default: off. > | > | Note that the options AllowDeactivateGrabs and AllowClosedownGrabs > | will allow users to remove the grab used by screen saver/locker > | programs. An API was written to such cases. If you enable this > | option, make sure your screen saver/locker is updated. > > <http://www.x.org/archive/X11R6.8.1/doc/Xorg.1.html> > > The API in question appears to be XF86MiscSetGrabKeysState: > > <http://cvsweb.xfree86.org/cvsweb/xc/programs/Xserver/hw/xfree86/XF86Config.man?hideattic=0#rev1.6> Given this additional information isn't this a vulnerability issue in the various screen lock applications rather than an issue with the Xorg server? - Tim
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