OSSN-0013: 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:
[^provider_.*$]
create = admin
read = admin,_member_
update = admin
delete = admin
[.*]
create = _member_
read = _member_
update = _member_
delete = _member_
Due to the way that the rules are processed in the Folsom and Grizzly
OpenStack releases, the admin restriction for properties beginning with
provider_ is nullified by the ‘.*’ permissions since it also matches
the same properties. This results in all users with the _member_ role
being allowed the ‘create’, ‘update’, and ‘delete’ permissions on
properties beginning with provider_, which is not what was intended.
This bug only affects the use of user-roles in Glance. It does not occur when policies are used to determine property protections.
Recommended Actions¶
This issue has been fixed in Havana (Glance 2013.2.2) and subsequent releases by changing the property protections rule processing to stop at the first rule that matches the property, even if it does not allow the attempted action.
Users of affected releases should avoid using multiple rules that would match the same property. Specifically, wildcard rules should be avoided unless they are the most restrictive rules defined.
If a permissive rule is needed that is intended to match all properties that are not matched by other rules, a carefully crafted regular expression should be used instead of a wildcard as demonstrated below:
[^provider_.*$]
create = admin
read = admin,_member_
update = admin
delete = admin
[^((?!provider_).)*$]
create = _member_
read = _member_
update = _member_
delete = _member_
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://docs.openstack.org/security-notes/OSSN-0013.html
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
