Consume Keystone Project Delete Events

In most of openstack deployments, barbican is expected to be integrated with keystone for its resource authorization needs. Keystone and barbican share keystone project as a common entity reference. Which means, project needs to exist in keystone before barbican resources (e.g. secrets and containers) can be added for that project. But when project is deleted in keystone, there is no action taken by barbican to reflect the change and it keep maintaining that project dangling resource references as-is. This blueprint is addressing related issues in this area.

Problem Description

Barbican resources are managed at keystone project level. As part of barbican resource creation, barbican tenant (a.k.a. project) is mapped to keystone project and resource is associated with the tenant. Over time, many more resources are added to the tenant. Now when project is deleted from keystone, currently barbican stays unaware of that change and keeps its resources as-is. Those project resources are now invalid and are kind of dangling references to a non existing project.

  • As barbican feature set expands, the amount of such tenant resources will grow over time which can negatively impact performance of db operations.

  • Hardware Security Modules (HSM) has a upper limit on the number of key encryption keys it can store. These numbers are correlated to number of projects in barbican. Without project status awareness, related invalid keys cleanup cannot be done to reclaim space for new keys in HSM.

  • In a corner case of PKI token service usage, for a small time window, unexpired PKI token(s) can access a deleted project resource as it has yet to fetch and process related revocation events from keystone. By making barbican aware of deleted projects, even those PKI token would not have access to barbican resources. Just to be clear, in general PKI token would not have this issue if revocation events are fetched pretty frequently.

Proposed Change

Keystone publishes notifications whenever a project is created, updated and deleted. Proposal is to add notification listener in barbican to consume keystone public events.

Keystone event payload has project id as resource_info and barbican event listener logic will propagate it to make changes on resources associated with that project.

Following is keystone sample notification on project delete:

Message: ctxt = [{}], metadata = [{'timestamp': u'2014-06-12 00:20:03.584997', 'message_id': u'1ade0b2b-1584-48b9-a026-64bd06659baf'}]
Message: severity = [info], publisher_id = [identity.arunkant-uws], event_type = [identity.project.deleted]
Message: payload = [{u'resource_info': u'00ac7ea2a1a3486284c8e2af27b7bc9e'}]

Event listener will use oslo messaging library which provides a abstraction to allow usage of different type of messaging transport.

  • Deletion of a keystone project will invoke delete on related secret(s), container(s), tenant entity. Currently entity delete is a soft delete as specific fields are marked deleted but the record remains in datastore. In the event that a project is disabled, Keystone will invalidate the tokens for that project and the secrets owned by that project will be inaccessible. The secrets owned by Barbican won’t be soft deleted but they will be unreachable. Also, the keystone delete project and the barbican delete project should both generate CADF audit events and ideally a correlation identifier should be used between these two events. Also an extension field in the audit record should be used to declare the type of delete (soft or hard).

  • Keystone sends various notification events based on its own resource types (e.g. user, project, role etc.) and type of operation (e.g. created, updated, deleted etc.). This proposal scope is to act on keystone project delete event only.

  • Barbican will add a queue to exchange to listen keystone notifications. Queue specific attributes e.g. exchange name and type, queue name, binding pattern etc. are going to be configurable in barbican configuration. Some of these attribute values need to align with keystone notification configuration.

  • Keystone currently publishes notification only with info severity. The binding pattern of notifications.* will handle that.

  • Barbican queue is going to be durable to survive broker restart.

  • This feature is going to be configurable and not enabled by default similar to keystone authentication via pipeline configuration.

  • Notifications are acknowledged only when barbican listener has processed event information. Auto-acknoledgement is going to be false.

  • Barbican connection to message queue is authenticated using username and password. These credentials are going to be defined as part of barbican configuration.

  • Depending on SSL support available in oslo messaging for a specific transport provider, related configuration is going to be added in barbican configuration.

  • In initial version, there is no trust established between messaging queue and barbican instance(s). KDS (Key distribution service, Kite) may help around this in future once other services start using it for this kind of functionality.

  • Changes on resource side will be committed only when complete event processing is done otherwise change will be rolled back.

  • Once such event support is available in barbican, those events can be propagated to barbican’s external sub-components if it makes sense. One example of such sub-comonent can be clean up of key encryption keys in HSM (when this feature is added in future).


There can be other ways to get keystone project information like polling model or accessing keystone datastore directly but there are not scalable and may introduce tight coupling between services. Events based asynchronous approach is better as keystone notifications are primarily intended for other openstack services to take action based on events e.g. cleanup of their resources.

Data model impact

There is no data model impact as we are going to utilize existing entity soft delete functionality.

REST API impact


Security impact

A keystone public event does not contain sensitive data by itself. Event data has information about operation and resource id.

  • As implication of those events will result in deleting barbican resources so clear logging of events and action taken will be needed.

  • Once auditing support is added in barbican, the project delete event will be one type of audit activity.

  • Message queue connection information needs to be secured similar to other external resources connections e.g. database.

Notifications & Audit Impact

A new notification listener is added. Related auditing information is going to be added to system.

Other end user impact


Performance Impact

There should not be performance impact other than new message handling server is added on same host system.

  • As result of this change, barbican number of connections to db system may increase depending on load of actionable events. Generally the number of such events will be quite less considering keystone projects are likely not to deleted regularly.

  • Depending on keystone event activity, a deployer can choose to enable notification listener on some of barbican instances assuming there is pool of barbican instances in a setup.

Other deployer impact

  • This feature needs to be enabled as default configuration will have it disabled.

  • Related notification listener configuration needs to be configured as per deployer’s existing messaging infrastructure setup.

  • A message handling server is added, as a new process, to transport notification events from queue to barbican.

Developer impact




Primary assignee:

Arun Kant <>

Other contributors:


Work Items

  • Need to add notification listener configuration

  • Implement notification listener and message handling server using oslo messaging packages.

  • Identify actionable events and process to make changes on barbican resources.

  • Implement these actions as a unit and rollback in case of a processing error. One option, needs to be investigated, is to do all operations within a SQLAlchemy session.

  • If missing, add checks in order and other resource API so that create and update of resource is not allowed for deleted tenants (a.k.a. keystone projects)




Add any integration test provided needed messaging support is available.

Documentation Impact

There will be additional documentation around notification listener configuration. Possibly a new option similar to following link