Ubuntu
gnome-screensaver package

Pressing Ctrl+Alt+Backspace when the screen is locked kills the X session

Bug #68695 reported by Manuel Lucena
20
This bug affects 1 person
Affects Status Importance Assigned to Milestone
GNOME Screensaver
Unknown
Medium
gnome-screensaver (Baltix)
Invalid
Undecided
Unassigned
gnome-screensaver (Ubuntu)
Fix Released
Wishlist
Unassigned

Bug Description

Binary package hint: gnome-screensaver

When the screen is locked, if you press Ctrl+Alt+Backspace, the X session is killed, and all the apps that were running on the desktop.

I have an Edgy updated from a Dapper (apt-get).

Pradeep (pradeep+-deactivatedaccount)
Changed in gnome-screensaver:
status: Unconfirmed → Confirmed
Revision history for this message
Pradeep (pradeep+-deactivatedaccount) wrote :

Since this pretty much defeats the purpose of locking a computer, allowing a non-user to force the system to logout, I'm marking this as a security vulnerability.

Revision history for this message
Malcolm Parsons (malcolm-parsons) wrote :

This behaviour comes from the xserver, not gnome-screensaver.
It can be disabled by adding
  Option "DontZap" "true"
to /etc/X11/xorg.conf

Revision history for this message
Pradeep (pradeep+-deactivatedaccount) wrote : Re: [Bug 68695] Re: Pressing Ctrl+Alt+Backspace when the screen is locked kills the X session

> This behaviour comes from the xserver, not gnome-screensaver.
> It can be disabled by adding
> Option "DontZap" "true"
> to /etc/X11/xorg.conf
won't that permanently disable Ctrl+Alt+Backspace?

Revision history for this message
Malcolm Parsons (malcolm-parsons) wrote :

Yes.

Revision history for this message
Oliver Grawert (ogra) wrote :

that should probably be filed upstream ...

Changed in gnome-screensaver:
importance: Undecided → Wishlist
Bug Watch Updater (bug-watch-updater)
Changed in gnome-screensaver:
status: Unknown → Unconfirmed
Bug Watch Updater (bug-watch-updater)
Changed in gnome-screensaver:
status: New → Invalid
Revision history for this message
Thomas O. (thomas-tgohome) wrote :

Well, I can see a reason for allowing it. For example, if gnome-screensaver were to freeze. It'd be no worse than pressing (and holding) the power button, and we can't disable that, so why disable Ctrl-Alt-BkSp?

Revision history for this message
christopherdstamper (christopherstamper) wrote :

This should be fixed.

Maybe x11 should have an option to disable 'zap' when in gnome-screensaver? (dunno how thatd work)

Revision history for this message
komputes (komputes) wrote :

>> This behaviour comes from the xserver, not gnome-screensaver.
>> It can be disabled by adding
>> Option "DontZap" "true"
>> to /etc/X11/xorg.conf
>won't that permanently disable Ctrl+Alt+Backspace
Jaunty's default X config will disable the zap (Ctrl+Alt+Backspace) option by default. I'm not sure if gnome-screensaver can block keys from accessing X. Perhaps if it is technically possible, gnome-screensaver could restrict all keys pressed to the password field and sanitize the input to filter out Ctrl+Alt+(Backspace,F1,F2...).

Bug Watch Updater (bug-watch-updater)
Changed in gnome-screensaver:
importance: Unknown → Medium
status: Invalid → Unknown
Revision history for this message
Marc Deslauriers (mdeslaur) wrote :

Ctrl+Alt+Backspace has been disabled by default for a few Ubuntu releases now. Closing this bug.

Changed in gnome-screensaver (Ubuntu):
status: Confirmed → Fix Released
Changed in gnome-screensaver (Baltix):
status: New → Invalid
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