Re: RFC: on adding new CLONE_* flags [WAS Re: [PATCH 0/4] clone: add CLONE_PIDFD]

[Enrico Weigelt, metux IT consult]

On 15.04.19 22:29, Andy Lutomirski wrote:

<snip>

> I would personally *love* it if distros started setting no_new_privs> for basically all processes.

Maybe a pam module for that would be fine.
But this should be configurable per-user, as so many things still rely
on suid.

Actually, I'd like to move all authentication / privilege switching
to factotum (login(1), sshd, etc then also could run as unprivileged
users).

> And pidfd actually gets us part of the> way toward a straightforward way to make sudo and su still work in a>
no_new_privs world: su could call into a daemon that would spawn the>
privileged task, and su would get a (read-only!) pidfd back and then>
wait for the fd and exit.

How exactly would the pidfd improve this scenario ?
IMHO, would just need to pass the inherited fd's to that daemon (eg.
via unix socket) which then sets them up in the new child process.

> I suppose that, done naively, this might> cause some odd effects with respect to tty handling, but I bet it's>
solveable.

Yes, signals and process groups would be a bit tricky. Some signals
could be transmitted in a similar way as ssh does.

But: how can we handle things like cgroups ?


--mtx

-- 
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
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