From: Dominick Grift <dac.override@gmail.com>
To: Laurent Bigonville <bigon@debian.org>
Cc: selinux-refpolicy@vger.kernel.org
Subject: Re: systemd --user for GDM started as unconfined_t instead of xdm_t
Date: Sun, 6 Oct 2019 11:41:56 +0200 [thread overview]
Message-ID: <20191006094156.GB469820@brutus.lan> (raw)
In-Reply-To: <a8196af0-1615-e78c-c21d-7525252d0441@debian.org>
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On Sun, Oct 06, 2019 at 11:22:00AM +0200, Laurent Bigonville wrote:
> Hello,
>
> I discovered today that the GDM own processes are started as unconfined_t
> instead of xdm_t because systemd --user process itself is started in that
> context.
>
> This is probably related to:
>
> commit da156aea1e89a6ff6025be7e50c9c8173e5a6dcf
> Author: Chris PeBenito <Christopher.PeBenito@microsoft.com>
> Date: Fri Apr 19 11:50:59 2019 -0400
>
> systemd: Add initial policy for systemd --user.
>
> This is just a start; it does not cover all uses.
>
> Signed-off-by: Chris PeBenito <Christopher.PeBenito@microsoft.com>
>
> Was that expected and/or wanted?
It just means that gdm hooks into pam, and since 1. your __default__ id is set to unconfined_u and 2. you do not have a private id for gdm (and gnome-initial-setup) systemd will start gdm's systemd --user instance with unconfined_u:unconfined_r:unconfined_t.
One (ugly but arguable less ugly than the alternative) solution is to create a "xdm_u" and allow systemd to run a systemd --user instance on behalf of gdm with "xdm_u:system_r:xdm_t"
That way you can tell selinux that gdm's systemd --user instance should never transition out of xdm_u:system_r:xdm_t
echo "system_r:init_t:s0 system_r:xdm_t:s0" > /etc/selinux/TYPE/contexts/users/xdm_u
Then all processes in the gdm session should stay in xdm_t (but some processes will be associate with xdm_u and other with system_u).
You would probably also want to add to semanage.conf:
ignoredirs = /var/lib/gdm;/run/gnome-initial-setup
and make sure that selinux does not relabel /run/user/$(id -u gdm)
>
> Kind regards,
>
> Laurent Bigonville
>
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next prev parent reply other threads:[~2019-10-06 9:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-06 9:22 systemd --user for GDM started as unconfined_t instead of xdm_t Laurent Bigonville
2019-10-06 9:41 ` Dominick Grift [this message]
2019-10-06 10:01 ` Dominick Grift
2019-10-06 10:13 ` Dominick Grift
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