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RBAC Utils Module

Overview

Patrole manipulates the os_primary Tempest credentials, which are the primary set of Tempest credentials. It is necessary to use the same credentials across the entire test setup/test execution/test teardown workflow because otherwise 400-level errors will be thrown by OpenStack services.

This is because many services check the request context's project scope -- and in very rare cases, user scope. However, each set of Tempest credentials (via dynamic credentials) is allocated its own distinct project. For example, the os_admin and os_primary credentials each have a distinct project, meaning that it is not always possible for the os_primary credentials to access resources created by the os_admin credentials.

The only foolproof solution is to manipulate the role for the same set of credentials, rather than using distinct credentials for setup/teardown and test execution, respectively. This is especially true when considering custom policy rule definitions, which can be arbitrarily complex.

Role Overriding

Role overriding is the way Patrole is able to create resources and delete resources -- including those that require admin credentials -- while still being able to exercise the same set of Tempest credentials to perform the API action that authorizes the policy under test, by manipulating the role of the Tempest credentials.

Patrole implicitly splits up each test into 3 stages: set up, test execution, and teardown.

The role workflow is as follows:

Setup: Admin role is used automatically. The primary credentials are overridden with the admin role.
Test execution: [patrole] rbac_test_role is used manually via the call to with rbac_utils.override_role(self). Everything that is executed within this contextmanager uses the primary credentials overridden with the [patrole] rbac_test_role.
Teardown: Admin role is used automatically. The primary credentials have been overridden with the admin role.

Test Setup

Automatic role override in background.

Resources can be set up inside the resource_setup class method that Tempest provides. These resources are typically reserved for "expensive" resources in terms of memory or storage requirements, like volumes and VMs. These resources are always created via the admin role; Patrole automatically handles this.

Like Tempest, however, Patrole must also create resources inside tests themselves. At the beginning of each test, the primary credentials have already been overridden with the admin role. One can create whatever test-level resources one needs, without having to worry about permissions.

Test Execution

Manual role override required.

"Test execution" here means calling the API endpoint that enforces the policy action expected by the rbac_rule_validation decorator. Test execution should be performed only after calling with rbac_utils.override_role(self).

Immediately after that call, the API endpoint that enforces the policy should be called.

Examples

Always use the contextmanager before calling the API that enforces the expected policy action.

Example:

@rbac_rule_validation.action(
    service="nova",
    rule="os_compute_api:os-aggregates:show")
def test_show_aggregate_rbac(self):
    # Do test setup before the ``override_role`` call.
    aggregate_id = self._create_aggregate()
    # Call the ``override_role`` method so that the primary credentials
    # have the test role needed for test execution.
    with self.rbac_utils.override_role(self):
        self.aggregates_client.show_aggregate(aggregate_id)

When using a waiter, do the wait outside the contextmanager. "Waiting" always entails executing a GET request to the server, until the state of the returned resource matches a desired state. These GET requests enforce a different policy than the one expected. This is undesirable because Patrole should only test policies in isolation from one another.

Otherwise, the test result will be tainted, because instead of only the expected policy getting enforced with the os_primary role, at least two policies get enforced.

Example using waiter:

@rbac_rule_validation.action(
    service="nova",
    rule="os_compute_api:os-admin-password")
def test_change_server_password(self):
    original_password = self.servers_client.show_password(
        self.server['id'])
    self.addCleanup(self.servers_client.change_password, self.server['id'],
                    adminPass=original_password)

    with self.rbac_utils.override_role(self):
        self.servers_client.change_password(
            self.server['id'], adminPass=data_utils.rand_password())
    # Call the waiter outside the ``override_role`` contextmanager, so that
    # it is executed with admin role.
    waiters.wait_for_server_status(
        self.servers_client, self.server['id'], 'ACTIVE')

Below is an example of a method that enforces multiple policies getting called inside the contextmanager. The _complex_setup_method below performs the correct API that enforces the expected policy -- in this case self.resources_client.create_resource -- but then proceeds to use a waiter.

Incorrect:

def _complex_setup_method(self):
    resource = self.resources_client.create_resource(
        **kwargs)['resource']
    self.addCleanup(test_utils.call_and_ignore_notfound_exc,
                    self._delete_resource, resource)
    waiters.wait_for_resource_status(
        self.resources_client, resource['id'], 'available')
    return resource

@rbac_rule_validation.action(
    service="example-service",
    rule="example-rule")
def test_change_server_password(self):
    # Never call a helper function inside the contextmanager that calls a
    # bunch of APIs. Only call the API that enforces the policy action
    # contained in the decorator above.
    with self.rbac_utils.override_role(self):
        self._complex_setup_method()

To fix this test, see the "Example using waiter" section above. It is recommended to re-implement the logic in a helper method inside a test such that only the relevant API is called inside the contextmanager, with everything extraneous outside.

Test Cleanup