Lockscreen can be bypassed after screen has blanked

[Sami Jaktholm]

Steps to reproduce:
1. Lock the screen
2. Let the lockscreen blank
3. Press ALT+TAB

What happens:
The application switcher appears and it's possible to switch between applications. The chosen application will get keyboard focus and any input will go there.

What should happen:
Nothing. Lockscreen should grab the keyboard and stop the input from going anywhere.

This has security implications. For example it's possible to open the "Run command" view and run "unity --replace" to destroy the lockscreen and open the session.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: unity 7.2.0+14.04.20140410.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-23.45-generic 3.13.8
Uname: Linux 3.13.0-23-generic x86_64
ApportVersion: 2.14.1-0ubuntu2
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CurrentDesktop: Unity
Date: Fri Apr 11 10:06:50 2014
InstallationDate: Installed on 2014-02-23 (46 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140223)
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Shiba (shiba89)]

On my system lockscreen lose keyboard focus even if not pressing Alt + Tab. The only way to unlock is to trigger "switch user" from the indicator.

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity - 7.2.0+14.04.20140411-0ubuntu1

---------------
unity (7.2.0+14.04.20140411-0ubuntu1) trusty; urgency=low

  [ Sami Jaktholm ]
  * Lockscreen: Give proper grabs to the shield before releasing
    blank_window_. (LP: #1306417)
 -- Ubuntu daily release <email address hidden> Fri, 11 Apr 2014 09:00:46 +0000