Re: [RFC] ssh: remove unconfined_shell_domtrans(sshd_t)

[Dominick Grift <dac.override@gmail.com>]

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On Sun, Sep 01, 2019 at 01:19:56PM +0200, Nicolas Iooss wrote:
> On Sat, Aug 31, 2019 at 10:54 PM Chris PeBenito <pebenito@ieee.org> wrote:
> >
> > On 8/31/19 1:27 PM, Dominick Grift wrote:
> > > This call allows sshd_t associated processes with run shell with an automatic domain transition to unconfined_t.
> > > I was unable to make sense of the commit that added this:
> > >
> > > https://github.com/SELinuxProject/refpolicy/commit/708aab13932bb8830a2d37850cc0a5c72a5d4df4
> > >
> > > Debian's motd dynamic pam module makes sshd run a shell, we want this shell to run with sshd_t instead of unconfined_t
> > >
> > > This patch will make the ssh_sysadm_login boolean apply to unconfined ssh logins.
> > > To me this makes sense, as unconfined_t is targeted equivalent to the strict sysadm_t.
> > > The boolean could however be renamed to the more generic ssh_priv_login name.
> > >
> > > Signed-off-by: Dominick Grift <dac.override@gmail.com>
> > > ---
> > >   policy/modules/services/ssh.te | 4 ----
> > >   1 file changed, 4 deletions(-)
> > >
> > > diff --git a/policy/modules/services/ssh.te b/policy/modules/services/ssh.te
> > > index 4e75b6e1..a99ad912 100644
> > > --- a/policy/modules/services/ssh.te
> > > +++ b/policy/modules/services/ssh.te
> > > @@ -328,10 +328,6 @@ optional_policy(`
> > >       systemd_dbus_chat_logind(sshd_t)
> > >   ')
> > >
> > > -optional_policy(`
> > > -     unconfined_shell_domtrans(sshd_t)
> > > -')
> > > -
> > >   optional_policy(`
> > >       xserver_domtrans_xauth(sshd_t)
> > >       xserver_link_xdm_keys(sshd_t)
> >
> > I don't have any objections to this.
> 
> Would it be possible to extend this patch to other callers of
> unconfined_shell_domtrans, like the patch below? It will help fix
> issues with Debian's PAM module that generates the MOTD (Message Of
> The Day) in a dynamic way, using shell commands (cf.
> https://wiki.debian.org/motd for more information: calling system()
> triggers a transition to system_u:system_r:unconfined_t because of
> unconfined_shell_domtrans).

Not sure about remotelogin and rshd (are people still using this?), but I do believe one should be able to remove it from local_login_t.

> 
> diff --git a/policy/modules/services/remotelogin.te
> b/policy/modules/services/remotelogin.te
> index bc2292e37892..c7c9c5646785 100644
> --- a/policy/modules/services/remotelogin.te
> +++ b/policy/modules/services/remotelogin.te
> @@ -91,10 +91,6 @@ optional_policy(`
>   telnet_use_ptys(remote_login_t)
>  ')
> 
> -optional_policy(`
> - unconfined_shell_domtrans(remote_login_t)
> -')
> -
>  optional_policy(`
>   usermanage_read_crack_db(remote_login_t)
>  ')
> diff --git a/policy/modules/services/rshd.te b/policy/modules/services/rshd.te
> index 0f4caffc4f33..196ed2848e4b 100644
> --- a/policy/modules/services/rshd.te
> +++ b/policy/modules/services/rshd.te
> @@ -74,6 +74,5 @@ optional_policy(`
>  ')
> 
>  optional_policy(`
> - unconfined_shell_domtrans(rshd_t)
>   unconfined_signal(rshd_t)
>  ')
> diff --git a/policy/modules/system/locallogin.te
> b/policy/modules/system/locallogin.te
> index a56f3d1fbe16..632d2542972d 100644
> --- a/policy/modules/system/locallogin.te
> +++ b/policy/modules/system/locallogin.te
> @@ -200,10 +200,6 @@ optional_policy(`
>   systemd_write_inherited_logind_sessions_pipes(local_login_t)
>  ')
> 
> -optional_policy(`
> - unconfined_shell_domtrans(local_login_t)
> -')
> -
>  optional_policy(`
>   usermanage_read_crack_db(local_login_t)
>  ')
> 

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Dominick Grift

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