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Date:   Mon, 13 Jan 2020 11:18:25 +0100
From:   Dominick Grift <dac.override@gmail.com>
To:     Chris PeBenito <pebenito@ieee.org>,
        refpolicy <selinux-refpolicy@vger.kernel.org>
Subject: Re: [RFC] refining systemd mountpoints
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        refpolicy <selinux-refpolicy@vger.kernel.org>
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On Mon, Jan 13, 2020 at 10:42:10AM +0100, Dominick Grift wrote:
> On Thu, Jan 09, 2020 at 10:42:40PM +0100, Dominick Grift wrote:
> > On Thu, Jan 09, 2020 at 04:06:38PM -0500, Chris PeBenito wrote:
> > > I'd like to refine how the policy handles systemd's mounton so that i=
t works
> > > similar to how we manage mountpoints for mount_t. Since systemd can b=
e made
> > > to mount over just about anything, I'm looking at adding a new condit=
ional
> > > that would allow init_t to mounton non_security_file_type, and then an
> > > interface like files_mountpoint().
> > >=20
> > > The question is for the implementation of the interface; I see two op=
tions,
> > > either the interface allows mounton for all file-like classes, or the
> > > classes are specified as a parameter:
> > >=20
> > > --------
> > > init.te:
> > > attribute init_mountpoint_type;
> > > allow init_t init_mountpoint_type:dir_file_class_set mounton;
> > >=20
> > > init.if:
> > > interface(`init_mountpoint',`
> > > typeattribute $1 init_mountpoint_type;
> > > ')

To be clear: I like this option:

1. You can BindPath/BindReadOnlyPath/BindReadWritePath/InaccessiblePath *an=
y* file in theory. So dir_file_class_set seems appropriate.
2. You might wat to extend it just a little though:

allow init_t init_mountpoint_type:dir_file_class_set { getattr mounton };
allow init_t init_mountpoint_type:dir search_dir_perms;


> > > --------
> > >=20
> > > or
> > >=20
> > > --------
> > > init.if:
> > > interface(`init_mountpoint',`
> > > allow init_t $1:$2 mounton;
> > > ')
> > > --------
> > >=20
> > > I like the first option because it is clearer since you can see the m=
ounton
> > > in init.te, but that is excessive access.  The second option could be=
 made
> > > to look like the first option, but it would need several attributes a=
nd
> > > interfaces, e.g. init_dir_mountpoint_type, init_file_mountpoint_type,=
 etc.
> > > which isn't so desirable.
> > >=20
> > > Any thoughts on this?
> >=20
> > I implemented the former in my policy. ie the dir_file_class_set equiv..
> >=20
> > 4163               (allow subj bind_path_obj_type_attribute (dirs (crea=
te)))
> > 4164               (allow subj bind_path_obj_type_attribute list_dir_pe=
rms)
> > 4165               (allow subj bind_path_obj_type_attribute (dir (mount=
on)))
> > 4166               (allow subj bind_path_obj_type_attribute create_file=
_perms)
> > 4167               (allow subj bind_path_obj_type_attribute (file (moun=
ton)))
> >=20
> > As you can see i even allow systemd to create the mountpoint in case it=
 does not exist. For example if /etc/machine-id does not exist and I have a=
 BindReadOnlyPath=3D/etc/machine-id then systemd will touch /etc/machine-id=
 and mount it ro
>=20
>=20
> Okay, I think I am wrong. It will not create the bind_path if it does not=
 exist. Not sure how I got to this...
>=20
> >=20
> > It also generally buggy. Systemd does not (alway's) use setfscreatecon =
to create the mountpoints. And sometimes it does use setfscreatecon where i=
t shouldnt.
> >=20
> > https://github.com/systemd/systemd/issues/13762
> >=20
> > >=20
> > > --=20
> > > Chris PeBenito
> >=20
> > --=20
> > Key fingerprint =3D 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> > https://sks-keyservers.net/pks/lookup?op=3Dget&search=3D0x3B6C5F1D2C7B6=
B02
> > Dominick Grift
>=20
>=20
>=20
> --=20
> Key fingerprint =3D 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> https://sks-keyservers.net/pks/lookup?op=3Dget&search=3D0x3B6C5F1D2C7B6B02
> Dominick Grift


--=20
Key fingerprint =3D 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=3Dget&search=3D0x3B6C5F1D2C7B6B02
Dominick Grift

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