extensions: don't expose host system fontconfig cache
Metadata
Current evaluation
Merged in snapcore/snapcraft#3509 via commit 6efa4ef6c, preventing GNOME and KDE desktop plugs from exposing the host fontconfig cache.
Resolution: closed resolved
Reason: PR #3509 was merged as commit 6efa4ef6c. It sets mount-host-font-cache to false in the desktop plug, blocking host /var/cache/fontconfig exposure with snapd 2.50 and newer.
Evaluated by: mr-cal-bot
No scores available.
Issue body
- [x] Have you followed the [guidelines for contributing](https://github.com/snapcore/snapcraft/blob/master/CONTRIBUTING.md)?
- [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)?
- [x] Have you successfully run `./runtests.sh static`?
- [x] Have you successfully run `./runtests.sh tests/unit`?
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This PR updates the GNOME and KDE extensions to configure their desktop plug to set the `mount-host-font-cache: false` interface attribute. In snapd 2.50, this will instruct the interface not to mount `/var/cache/fontconfig` into the sandbox mount namespace, ensuring that cache files found in that directory cannot be used. More details can be found in https://github.com/snapcore/snapd/pull/9805.
All of these extensions include code to build a private version of the fontconfig cache, so the host cache can only be a source of problems.
Snapd versions prior to 2.50 do not support this interface attribute, so will ignore it and behave as before. So there is no need to delay merging this until it is released or update the `assumes` setting.
Evaluation history
| Date | Model | Scores | Action | Summary |
|---|---|---|---|---|
| stealth/space-bunny-alpha | — | closed resolved | Merged in snapcore/snapcraft#3509 via commit 6efa4ef6c, preventing GNOME and KDE desktop plugs from exposing the host fontconfig cache. | |
| stealth/space-bunny-alpha | — | closed resolved | Merged #3509 as commit 6efa4ef6c, setting mount-host-font-cache: false for GNOME and KDE desktop plugs to prevent host /var/cache/fontconfig exposure. | |
| qwen/qwen3.6-35b-a3b | — | — | Merged updates to GNOME and KDE extensions disable mounting the host fontconfig cache into the sandbox. Setting mount-host-font-cache to false prevents interference, as extensions build private caches. Approved and merged after passing CI. | |
| qwen3.6-35b-a3b-mtp-q6 | — | — | Merged to master. Configures GNOME and KDE extensions to disable host fontconfig cache mounting via the mount-host-font-cache attribute. Prevents sandbox cache conflicts and remains backward compatible with snapd versions prior to 2.50. |
Update history
No update history recorded yet.
Related work
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Related To:
snapd#9805
(confidence 98%)
Added the snapd desktop interface attribute that the Snapcraft extensions now configure.
Related issues
| Issue | Project | State | Summary | Similarity |
|---|---|---|---|---|
| #4257 Stop fontconfig from loading from host’s /etc/fonts/conf.d | snapcraft | merged | Merged as snapcraft#4257 via commit 7877ca5bb, preventing fontconfig from loading host /etc/fonts/conf.d and fixing conflicting font selection. | |
| #3361 extensions: use SNAP_COMMON instead of SNAP_DATA for fonts | snapcraft | merged | Merged PR #3361 in commit f9501944d, switching desktop extension font paths from SNAP_DATA to SNAP_COMMON to prevent font breakage during background snap updates. |