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From:   Dominick Grift <dominick.grift@defensec.nl>
To:     Chris PeBenito <pebenito@ieee.org>
Cc:     Russell Coker <russell@coker.com.au>,
        selinux-refpolicy@vger.kernel.org
Subject: Re: machinectl shell policy
References: <8322849.62pqQp6Oog@liv> <1723812.Y751QtlBzf@liv>
        <ypjl8s9m5nbi.fsf@defensec.nl> <5735537.jZnottUgFY@liv>
        <f142c9ee-ce7e-7f7d-dec4-9d93ddd49c43@ieee.org>
Date:   Mon, 04 Jan 2021 16:00:52 +0100
In-Reply-To: <f142c9ee-ce7e-7f7d-dec4-9d93ddd49c43@ieee.org> (Chris PeBenito's
        message of "Mon, 4 Jan 2021 09:48:42 -0500")
Message-ID: <ypjlmtxo4uhn.fsf@defensec.nl>
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Chris PeBenito <pebenito@ieee.org> writes:

> On 12/25/20 4:16 AM, Russell Coker wrote:
>> On Friday, 25 December 2020 6:58:41 PM AEDT Dominick Grift wrote:
>>> Russell Coker <russell@coker.com.au> writes:
>>>> On Thursday, 24 December 2020 7:37:50 PM AEDT Dominick Grift wrote:
>>>>>> To enable "machinectl shell" on recent versions of systemd we need
>>>>>> something like the above policy (which is not complete or ideal, still
>>>>>> doesn't work so no point polishing it) and something for the below.
>>>>>> What
>>>>>> is the below about?
>>>>>
>>>>> this should be thoroughly addressed. machined creates a login pty that
>>>>> gets relabeled on login as per type_change rules.
>>>>
>>>> Currently it's not being relabeled on Debian, but that's a separate issue.
>>>
>>> Maybe the required type_change rules arent present?
>> Here is all the policy to make it work.  Maybe we should have a type
>> like
>> system_dbusd_devpts_t for this.  This is not policy for inclusion, this is
>> policy to discuss before writing that policy.
>> term_user_pty(user_systemd_t, user_devpts_t)
>> term_login_pty(devpts_t)
>> allow user_systemd_t user_devpts_t:chr_file rw_file_perms;
>> # for machinectl shell
>> allow sysadm_t systemd_machined_t:dbus send_msg;
>> systemd_manage_userdb_runtime_dirs(systemd_machined_t)
>> systemd_manage_userdb_runtime_sock_files(systemd_machined_t)
>> term_use_ptmx(systemd_machined_t)
>> dev_getattr_fs(systemd_machined_t)
>> term_getattr_pty_fs(systemd_machined_t)
>> allow systemd_machined_t sysadm_t:dbus send_msg;
>> allow systemd_machined_t devpts_t:chr_file rw_file_perms;
>> allow system_dbusd_t systemd_machined_t:fd use;
>> allow system_dbusd_t devpts_t:chr_file { read write };
>> allow system_dbusd_t ptmx_t:chr_file { read write };
>> allow sysadm_t systemd_machined_t:fd use;
>> allow user_systemd_t shell_exec_t:file entrypoint;
>
> The pty stuff seems to make sense, but I'm curious why there is a
> transition into user_systemd_t for the shell.

The policy above is referencing "devpts_t", that is sub-optimal. there
shouldnt be any pty chr files with the devpts_t filesystem type


>
>> allow user_systemd_t systemd_machined_t:fd use;
>> allow user_systemd_t self:process signal;
>> allow user_t systemd_machined_t:fd use;
>> allow user_t user_systemd_t:fifo_file { getattr write };
>> allow user_t init_t:process signal;
>
>
>
>>>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=892001
>>>>
>>>> We have work in progress on dbus-broker in Debian.  Would it make sense to
>>>> only support dbus-broker in SE Linux policy?  Being forced to use only 1
>>>> of
>>>> the 2 dbus programs (and the newer and faster 1 of the 2) is a very small
>>>> trade-off, smaller than some of the other trade-offs for running SE Linux.
>
> I'd prefer to keep both unless it becomes onerous.
>
>
>>> should probably be able to support both (conditionally) but could get messy
>> Currently we have a heap of ifdef systemd in the policy, as probably
>> the only
>> people not wanting dbus-broker will be the ones not wanting systemd we could
>> include it in the same ifdef rules.
>
> The "else" of the ifdef can work.

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Dominick Grift