Unprivileged Shutdown?

Unprivileged Shutdown?

[Dallin Dahl]

I have been using simple privilege escalation to poweroff the machine,
but looking through the source code for s6-linux-init-shutdownd and
friends, it appears the only constraint on interacting with the daemon
is the permissions on run-image/service/s6-linux-init-shutdownd/fifo.

The default appears to be:
600 root root
I've changed it on my system to be:
620 root power
and added my user to the power group.

This seems like the cleanest way to implement unprivileged
poweroff/reboot, but I'm concerned that it's not possible by default.
Is there a better way, or is it just meant to be done manually?

Thanks!
--Dallin

Re: Unprivileged Shutdown?

[Laurent Bercot]

>I have been using simple privilege escalation to poweroff the machine,
>but looking through the source code for s6-linux-init-shutdownd and
>friends, it appears the only constraint on interacting with the daemon
>is the permissions on run-image/service/s6-linux-init-shutdownd/fifo.
>
>The default appears to be:
>600 root root
>I've changed it on my system to be:
>620 root power
>and added my user to the power group.
>
>This seems like the cleanest way to implement unprivileged
>poweroff/reboot, but I'm concerned that it's not possible by default.
>Is there a better way, or is it just meant to be done manually?

  No, you are correct that it is the right mechanism.

  Allowing unprivileged shutdown is a dangerous operation and should
only be done is very specific circumstances (i.e. when a normal user
has complete seat and console access), so it's not the default and the
mechanism is fairly hidden.
  If there's demand, I can probably write a s6-linux-init-shutdown-perms
program in a future version that would let you specify the user/group
allowed to shutdown, rather than having you manually tinker with the
fifo.

--
  Laurent