Open Stack

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Hi,

The previous revision of this OSSN specified an incorrect workaround.
 This new revision should supersede the old revision.

Thanks,
- -NGK

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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 at lists.openstack.org
OpenStack Security Group : https://launchpad.net/~openstack-ossg
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