xside: Introduce override_redirect protection #41
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Prior to this commit, an application (malicious or not) could create
a very large window with the override_redirect attribute set. If the
window in question was large enough to prevent the user from interacting
with the window manager and/or Qubes OS widgets, it was impossible to
terminate the application and/or the hosting VM via regular means.
Hence, this commit introduces a simple protection measure against very
large windows that have the override_redirect attribute set. The
protection works by unsetting the override_redirect attribute for
windows that attempt to cover more than 90% of the screen. Doing so
allows the user to move and/or minimize the windows in question.
When the protection takes effect for the first time, the user is warned
once with a persistent notification about what just happened and is
informed of a way to disable this protection on a per-VM basis.
("persistent" notifications need to be clicked on to be dismissed.)
The protection feature can be disabled via /etc/qubes/guid.conf in dom0,
and this commit introduces an example in the aforementioned file along
with an explanation to help users.
marmarek
approved these changes
Mar 31, 2020
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This pull request aims to mitigate/work around issue QubesOS/qubes-issues#5731 by unsetting the override_redirect flag of windows that cover more than 90% of the screen. Please see the commit message for further information.
This commit was tested with Qubes OS 4.0 only. For Qubes OS 4.1, I have only verified that the code compiles as expected.