On Wed 06 Dec 2017 at 22:52:17 +0100, Urs Thuermann wrote: > Yesterday, my 10 years old son logged into my laptop running Debian > jessie using his account, and curiously asked if he is allowed to try > the /sbin/reboot command. Knowing I have a Linux system as opposed to > some crappy Win machine, I replied "sure, go ahead and try". Seconds > later I was completely shocked when the machine actually rebooted... > > Of course, my son doesn't have any special privileges, no entry in > /etc/sudoers, etc. But then I see
He is privileged because he has physical access to the machine. > > $ ls -l /sbin/reboot > lrwxrwxrwx 1 root root 14 Apr 8 2017 /sbin/reboot -> /bin/systemctl > $ ls -l /bin/systemctl > -rwxr-xr-x 1 root root 538904 Apr 8 2017 /bin/systemctl > $ dpkg -S /bin/systemctl > systemd: /bin/systemctl > > The /bin/systemctl binary is not suid root, so I assume[1] it > communicates to systemd which then reboots the machine without > checking what user the request comes from. > > I wonder how can such a severe bug make it into a Debian stable > distribution? And is this just an insane default setting on Debian's > side or is it yet another instance of brain-dead systemd behavior? A user with physical access to the machine can press the ON/OFF switch or pull the plug out or switch to a terminal and do CTL+ALT+DEL. Which one of these actions is a bug in Debian? > Searching the man pages I couldn't find a way to fix this. How can > that be stopped? A cast-iron solution for stopping a user with physical access to a machine from powering it off has been sought for ages. -- Brian.
