coreos-installer < 0.10.0 writes world-readable Ignition config to installed system

Impact

On systems installed with coreos-installer before 0.10.0, the user-provided Ignition config was written to /boot/ignition/config.ign with world-readable permissions, granting unprivileged users access to any secrets included in the config.

Default configurations of Fedora CoreOS and RHEL CoreOS do not include any unprivileged user accounts. In addition, instances launched from a cloud image, and systems provisioned with the ignition.config.url kernel argument, do not use the config.ign file and are unaffected.

Patches

coreos-installer 0.10.0 and later writes the Ignition config with restricted permissions.

Workarounds

On Fedora CoreOS systems installed from version 34.20210711.3.0 (stable), 34.20210711.2.0 (testing), 34.20210711.1.1 (next) and later, the /boot/ignition directory and its contents are removed after provisioning is complete. All Fedora CoreOS systems that have updated to these versions or later have automatically removed the /boot/ignition directory and no action is required.

On other systems, /boot/ignition/config.ign can be removed manually, as it is not used after provisioning is complete:

sudo mount -o remount,rw /boot
sudo rm -rf /boot/ignition

References

For more information, see https://github.com/coreos/fedora-coreos-tracker/issues/889.

For more information

If you have any questions or comments about this advisory, open an issue in coreos-installer or email the CoreOS development mailing list.