Bug#1084152: warzone2100: /usr/games/warzone2100 wrapper script assumes XAUTHORITY is set

[Simon McVittie]

Control: retitle -1 warzone2100: /usr/games/warzone2100 wrapper script assumes XAUTHORITY is set

On Sat, 05 Oct 2024 at 18:21:53 +0000, Philipp Klaus Krause wrote:
>On a Raspi 4B, I have warzone2100 installed. However, trying to run it fails:
>
>philipp at raspi-rebstock:~$ warzone2100
>bwrap: execvp /sys: No such file or directory
>philipp at raspi-rebstock:~$ which warzone2100
>/usr/games/warzone2100

This appears to be because the /usr/games/warzone2100 wrapper script 
invokes bubblewrap without sufficient caution, and assumes that the 
environment variable XAUTHORITY will always be set. If it isn't, the 
environment variable reference expands to 0 arguments, and bubblewrap's 
command-line parser gets confused.

Is there a reason why this game, specifically, needs to be sandboxed? Is 
it believed to be particularly susceptible to attacks?

If the wrapper script is necessary, I would recommend putting it through 
shellcheck(1), and using `set -eu -o pipefail` ("unofficial strict 
mode") since it's a bash script already; or maybe rewriting it in a 
language with less dysfunctional error behaviour than bash, such as 
Python, Perl or even C.

>--bind $HOME/.local/share/warzone2100 $HOME/.local/share/warzone2100

Should this (and other references to .local/share) be using
"${XDG_DATA_HOME:-"$HOME/.local/share"}", or does this game hard-code 
~/.local/share contrary to the XDG basedir spec[1]?

>--bind-try /run/user/$UID/pulse /run/user/$UID/pulse

This and other references to /run/user/$UID should probably be 
$XDG_RUNTIME_DIR, and should be quoted. In practice systemd does set 
XDG_RUNTIME_DIR=/run/user/$(id -u), but this is not an API guarantee.

>--dev /dev --dev-bind /dev/dri /dev/dri

This will prevent this game from using joysticks or gamepads, if that's 
relevant to its control scheme.

>--ro-bind-try $XAUTHORITY $XAUTHORITY

This should probably be something like

${XAUTHORITY+--ro-bind-try "$XAUTHORITY" "$XAUTHORITY"}

     smcv

[1] https://specifications.freedesktop.org/basedir-spec/latest/