Re: [PATCH 1/2] Allow greeter to start dbus and transition

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

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On Sun, Dec 23, 2018 at 05:33:59PM +0100, Dominick Grift wrote:
> On Sat, Dec 22, 2018 at 02:28:15PM -0500, Chris PeBenito wrote:
> > On 12/20/18 8:41 PM, David Sugar wrote:
> > > The display manager lightdm (and I think gdm) start a dbus binary.
> > > This allows that to happen in a special dbus domain.
> > > 
> > > type=AVC msg=audit(1544626796.378:201): avc:  denied  { execute } for  pid=9973 comm="dbus-launch" name="dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544626796.378:201): avc:  denied  { read open } for  pid=9973 comm="dbus-launch" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544626796.378:201): avc:  denied  { execute_no_trans } for  pid=9973 comm="dbus-launch" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544626796.378:201): avc:  denied  { map } for  pid=9973 comm="dbus-daemon" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544628523.635:3208): avc:  denied  { execute } for  pid=16376 comm="at-spi-bus-laun" name="dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544628523.635:3208): avc:  denied  { read open } for  pid=16376 comm="at-spi-bus-laun" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544628523.635:3208): avc:  denied  { execute_no_trans } for  pid=16376 comm="at-spi-bus-laun" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > type=AVC msg=audit(1544628523.635:3208): avc:  denied  { map } for  pid=16376 comm="dbus-daemon" path="/usr/bin/dbus-daemon" dev="dm-1" ino=6695040 scontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:dbusd_exec_t:s0 tclass=file permissive=1
> > > 
> > > Signed-off-by: Dave Sugar <dsugar@tresys.com>
> > > ---
> > >   policy/modules/services/xserver.te | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/policy/modules/services/xserver.te b/policy/modules/services/xserver.te
> > > index fa7ce88e..12ad3a87 100644
> > > --- a/policy/modules/services/xserver.te
> > > +++ b/policy/modules/services/xserver.te
> > > @@ -568,6 +568,7 @@ optional_policy(`
> > >   optional_policy(`
> > >   	dbus_system_bus_client(xdm_t)
> > >   	dbus_connect_system_bus(xdm_t)
> > > +	dbus_role_template(xdm, system_r, xdm_t)
> > >   	optional_policy(`
> > >   		accountsd_dbus_chat(xdm_t)
> > 
> > This doesn't sit well with me.  XDM isn't a user, or is system_r a user
> > role, so it shouldn't be using this template.  On my system,
> > at-spi-bus-launcher is running as part of my user session, not as part of
> > XDM.  It seems like this may be a transition problem.
> 
> It does not sit well with me either but gdm is actually a "user" in way's. and it has a session.
> 
> the gdm DM policy should never have been merged with XDM DM policy as XDM is much cleaner.
> 
> GDM is nasty

In dssp2 i actually have a seuser for gdm:

# seinfo -xugdm.id

Users: 1
   user gdm.id roles sys.role level s0 range s0;

And believe me, I did not do that for fun. In distributions with systemd --user this is just needed because
systemd will spawn a --user instance for gdm and this user instance spawns all kinds of processes on gdm's behalf

for example dbus instance, the last thing you want is to have a gdm dbus instance running with system_dbusd_t

> 
> > 
> > -- 
> > Chris PeBenito
> 
> -- 
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> Dominick Grift



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Dominick Grift

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