Some versions of Glance do not apply property protections as expected
---

### Summary ###
Tom Leaman reported an issue to the OpenStack mailing list that
affects Glance property protections. A permissive property setting in the
Glance property protections configuration file will override any previously
set stricter ones.

### Affected Services / Software ###
Glance, Folsom, Grizzly

### Discussion ###
Glance property protections limit the users who can perform CRUD operations on
a Glance property to those in specific roles. When the property protections
rules are processed in the Folsom and Grizzly OpenStack releases, a matching
rule will only stop the processing of subsequent rules if it authorizes the
attempted action. If there is a matching rule that would reject an action that
is followed by another matching rule that would accept the action, then the
action is accepted even though one may expect it to be rejected.

In the following policy-protections.conf example, the desired result is to
restrict 'update' and 'delete' permissions for any property beginning with
'provider_' to only users with the 'admin' role.

--- begin example property-protections.conf snippet ---
[^provider_.*$]
create = admin
read = admin,_member_
update = admin
delete = admin

[.*]
create = _member_
read = _member_
update = _member_
delete = _member_
--- end example property-protections.conf snippet ---

Due to the way that the rules are processed in the Folsom and Grizzly OpenStack
releases, the admin restriction for properties beginning with 'provider_' is
nullified by the '.*' permissions since it also matches the same properties.
This results in all users with the '_member_' role  being allowed the 'create',
'update', and 'delete' permissions on properties beginning with 'provider_',
which is not what was intended.

This bug only affects the use of user-roles in Glance. It does not occur when
policies are used to determine property protections.

### Recommended Actions ###
This issue has been fixed in Havana (Glance 2013.2.2) and subsequent releases
by changing the property protections rule processing to stop at the first rule
that matches the property, even if it does not allow the attempted action.

Users of affected releases should avoid using multiple rules that would match
the same property. Specifically, wildcard rules should be avoided unless they
are the most restricive rules defined.

If a permissive rule is needed that is intended to match all properties that
are not matched by other rules, a carefully crafted regular expression should
be used instead of a wildcard as demonstrated below.

--- begin example property-protections.conf snippet ---
[^provider_.*$]
create = admin
read = admin,_member_
update = admin
delete = admin

[^((?!provider_).)*$]
create = _member_
read = _member_
update = _member_
delete = _member_
--- end example property-protections.conf snippet ---

In the above example, 'create', 'update', and 'delete' operations are only
allowed for users with the '_member_' role for properties that do not begin
with 'provider_'.

Configuration files with multiple property protection entries set should be
tested to ensure that CRUD actions are constrained in the way the administrator
intended.

### Contacts / References ###
This OSSN : https://wiki.openstack.org/wiki/OSSN/OSSN-0013
Original Launchpad Bug : https://bugs.launchpad.net/glance/+bug/1271426
Original Report : http://lists.openstack.org/pipermail/openstack-dev/2014-January/024861.html
Glance Property Protections : https://wiki.openstack.org/wiki/Glance-property-protections
OpenStack Security ML : openstack-security@lists.openstack.org
OpenStack Security Group : https://launchpad.net/~openstack-ossg