On Mon, Apr 7, 2025 at 9:08 PM Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
> It's also the default policy on Debian 12 and RHEL9 that if you're
> logged into the GUI, any program can run:
>
> $ truncate -s 3g /tmp/a
> $ mkfs.hfs /tmp/a
> $ <write evil stuff on /tmp/a>
> $ udisksctl loop-setup -f /tmp/a
> $ udisksctl mount -b /dev/loopX
>
> and the user never sees a prompt. GNOME and KDE both display a
> notification when the mount finishes, but by then it could be too late.
> Someone should file a CVE against them too.
At least on SUSE orphaned and other problematic filesystem kernel modules
are blacklisted. I wonder why other distros didn't follow this approach.
> You can tighten this up by doing this:
>
> # cat > /usr/share/polkit-1/rules.d/always-ask-mount.rules << ENDL
> // don't allow mounting, reformatting, or loopdev creation without asking
> polkit.addRule(function(action, subject) {
> if ((action.id == "org.freedesktop.udisks2.loop-setup" ||
> action.id == "org.freedesktop.udisks2.filesystem-mount" ||
> action.id == "org.freedesktop.udisks2.modify-device") &&
> subject.local == true) {
> return polkit.Result.AUTH_ADMIN_KEEP;
> }
> });
> ENDL
Thanks for sharing this!
> so at least you have to authenticate with an admin account. We do love
> our footguns, don't we? At least it doesn't let you do that if you're
> ssh'd in...
IMHO guestmount and other userspace filesystem implementations should
be the default
for such mounts.
//richard
