On Tue, Feb 19, 2019 at 01:37:16PM +0100, Dominick Grift wrote:
> Petr Lautrbach <plautrba@xxxxxxxxxx> writes:
>
> > Dominick Grift <dac.override@xxxxxxxxx> writes:
> >
> >> Paul Moore <paul@xxxxxxxxxxxxxx> writes:
> >>
> >>> On Sat, Feb 16, 2019 at 7:12 AM Dominick Grift
> >>> <dac.override@xxxxxxxxx> wrote:
> >>>>
> >>>> On Sat, Feb 16, 2019 at 01:04:12PM +0100, Dominick Grift wrote:
> >>>> > On Fri, Feb 15, 2019 at 02:48:45PM -0500, Stephen Smalley >
> >>>> wrote:
> >>>> > <snip>
> >>>> >
> >>>> > >
> >>>> > > Oh, I see: scripts/selinux/install_policy.sh just invokes > >
> >>>> checkpolicy
> >>>> > > without specifying -U / --handle-unknown, so the policy > >
> >>>> defaults to deny,
> >>>> > > and that would indeed render dbus-daemon and systemd > >
> >>>> broken with that
> >>>> > > policy. Might be as simple to fix as passing -U allow.
> >>>> >
> >>>> > I have looked a litte into this and here are some >
> >>>> observations:
> >>>> >
> >>>> > 1. You can boot mdp as-is in permissive mode if you use >
> >>>> `checkpolicy` with `-U allow`
> >>>> >
> >>>> > 2. You need *at least* an `/etc/selinux/dummy/seusers` with
> >>>> > `__default__:user_u` and an accompanying
> >>>> > `/etc/selinux/dummy/contexts/failsafe_context` with
> >>>> > `base_r:base_t` to boot mdp in enforcing
> >>>
> >>> Wow. I didn't expect we would get to this point so quickly.
> >>>
> >>> Originally my plan had been to just merge the mdp changes that
> >>> Stephen
> >>> submitted, and leave the rest for some other time. Although based
> >>> on
> >>> everything in this thread, it looks like we are really close to
> >>> having
> >>> something that you can build and boot without too many hacks.
> >>>
> >>>> > 3. There is an issue with checkpolicy and object_r:
> >>>> >
> >>>> > PAM libselinux clients such as `login` try to associate >
> >>>> `object_r` with the tty and fail.
> >>>> >
> >>>> > if you try to append: `role object_r; role object_r types >
> >>>> base_t;`
> >>>> > to policy.conf and compile that with `checkpolicy` then the
> >>>> > `roletype-rule` does *not* end up in the compiled policy for >
> >>>> some
> >>>> > reason.
> >>>
> >>> This sounds like a bug in checkpolicy ... ?
> >>
> >> Yes, looks like it
> >>
> >>>
> >>>> > thus, you cannot log in because object_r:base_t is not > valid.
> >>>> >
> >>>> > To hack around this add `default_role * source` rules to >
> >>>> policy.conf and recompile.
> >>>> >
> >>>> > This will allow you to log into the system locally in >
> >>>> enforcing mode.
> >>>> >
> >>>> > 4. I also noticed that fedoras' ssh seems to hardcode >
> >>>> `sshd_net_t`
> >>>> > for its "privsep" functionality so, while untested, you >
> >>>> probably
> >>>> > need an `openssh_contexts` with `privsep_preauth=base_t`
> >
> > "sshd_net_t" is really hardcoded as a fallback but
> > ssh_selinux_change_context("sshd_net_t"); is not a fatal operation.
> > If it fails it just logs a debug message and the type of the process
> > stays unaffected - by default it's sshd_t
> >
> > I believe that openssh_context is not necessary if you don't mind or
> > want to use different type for privsep preauth sshd processes.
>
> Thanks. So just a warning message. Might be possible to only log it if
> debug is enabled?
Whoops sorry. I overlooked the remainder of your reply. Thanks for addressing.
>
> >
> >
> >>> Petr, what's the deal with ssh on Fedora?
> >>
> >> I wonder whether it would be possible (and feasible) to not
> >> transition on
> >> privsep_preauth at all *unless* a privsep preauth type is specified
> >> in
> >> openssh_context.
> >>
> >> Currently it falls back to a hardcoded type to transition to if
> >> openssh_contexts does not exist.
> >>
> >> Then again, i would not want to risk breaking or regressing some of
> >> the nice
> >> functionality openssh in fedora has for selinux. It's state is
> >> currently
> >> very good even compared to RHEL.
> >
> > I think it's feasible without a big risk.
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=1678695
> >
> >>>
> >>>> The `install_policy.sh` script should probably also do a bash file
> >>>> test for `checkpolicy` and fail gracefully if its not found
> >
>
> --
> Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
> Dominick Grift
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
Attachment:
signature.asc
Description: PGP signature
