Stephen Smalley <stephen.smalley@xxxxxxxxx> writes: > On Mon, Feb 18, 2019, 2:09 AM Dominick Grift <dac.override@xxxxxxxxx wrote: > > 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 > > I don't think so. object_r has always been handled specially. The kernel ignores the role-type definition for it and always exempts contexts > that contain it from user-role, role-type, and user-range restrictions. We didn't use to include it in the policy at all; I think CIL does but > we only generate a stub in the kernel policy with the role name and value but no types and the kernel ignores it. What exactly breaks with > pam_selinux? The login program (pam_selinux) is not able to relabel the login user tty (/dev/ttys0: user_u:base_r:base_t -> user_u:object_r:base_t) and so the user cannot log into the system in enforcing mode. Maybe a missing contexts config file? I suppose I should look at it again since you sound confident that this is not a bug. I also suppose Android uses checkpolicy so they would have noticed? > > > > >> > 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` > > > > 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. > > > > >> 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
