Juju: CloudSpec method leaking cloud credentials

Impact

If a user has login permission to a controller and knows the controller model UUID, they can call the CloudSpec method on the Controller facade and get cloud credentials used to bootstrap the controller.

The CloudSpec API is called by workers running in the controller to maintain connection to the cloud - this aspect is not the issue. The API is also called by the CLI when killing (force destroying a controller with juju kill-controller). This is the problematic aspect. The API is exposed to any client caller where that client has nothing more than logon permission on the controller. What should happen is that getting access to the credential should be limited to those client connections where the authenticated user has superuser or model admin permission.

This affect 2.9, 3.6, 4.0.6 (snap from 4.0/edge channel).

The fix will allow non-confidential, public information like cloud endpoint etc to be read, but only controller superusers or model admins will be able to see the credential details.

Patches

No patch exists.

Workarounds

The only mitigation is to restrict ingress to the controller API port 17070 on all controller machines (for vm deployments) or the controller service (for k8s deployments). The Juju CLI and other clients like libjuju or JAAS require ingress to port 17070 so any restricted access will need to take into account those access requirements.