Primer

Like most OpenStack services, keystone protects its API using role-based access control (RBAC).

Users can access different APIs depending on the roles they have on a project, domain, or system, which we refer to as scope.

As of the Rocky release, keystone provides three roles called admin, member, and reader by default. Operators can grant these roles to any actor (e.g., group or user) on any scope (e.g., system, domain, or project). If you need a refresher on authorization scopes and token types, please refer to the token guide. The following sections describe how each default role behaves with keystone’s API across different scopes. Additionally, other service developers can use this document as a guide for implementing similar patterns in their services.

Default roles and behaviors across scopes allow operators to delegate more functionality to their team, auditors, customers, and users without maintaining custom policies.

Roles Definitions

The default roles provided by keystone, via keystone-manage bootstrap, are related through role implications. The admin role implies the member role, and the member role implies the reader role. These implications mean users with the admin role automatically have the member and reader roles. Additionally, users with the member role automatically have the reader role. Implying roles reduces role assignments and forms a natural hierarchy between the default roles. It also reduces the complexity of default policies by making check strings short. For example, a policy that requires reader can be expressed as:

"identity:list_foo": "role:reader"

Instead of:

"identity:list_foo": "role:admin or role:member or role:reader"

Reader

The reader role provides read-only access to resources within the system, a domain, or a project. Depending on the assignment scope, two users with the reader role can expect different API behaviors. For example, a user with the reader role on the system can list all projects within the deployment. A user with the reader role on a domain can only list projects within their domain.

By analyzing the scope of a role assignment, we increase the re-usability of the reader role and provide greater functionality without introducing more roles. For example, to accomplish this without analyzing assignment scope, you would need system-reader, domain-reader, and project-reader roles in addition to custom policies for each service.

It’s imperative to note that reader is the least authoritative role in the hierarchy because assignments using admin or member ultimately include the reader role. We document this explicitly so that reader roles are not overloaded with read-only access to sensitive information. For example, a deployment pursuing a specific compliance target may want to leverage the reader role to perform the audit. If the audit requires the auditor to evaluate sensitive information, like license keys or administrative metadata, within a given scope, auditors shouldn’t expect to perform these operations with the reader role. We justify this design decision because sensitive information should be explicitly protected, and not implicitly exposed.

The reader role should be implemented and used from the perspective of least-privilege, which may or may not fulfill your auditing use case.

Member

Within keystone, there isn’t a distinct advantage to having the member role instead of the reader role. The member role is more applicable to other services. The member role works nicely for introducing granularity between admin and reader roles. Other services might write default policies that require the member role to create resources, but the admin role to delete them. For example, users with reader on a project could list instance, users with member on a project can list and create instances, and users with admin on a project can list, create, and delete instances. Service developers can use the member role to provide more flexibility between admin and reader on different scopes.

Admin

We reserve the admin role for the most privileged operations within a given scope. It is important to note that having admin on a project, domain, or the system carries separate authorization and are not transitive. For example, users with admin on the system should be able to manage every aspect of the deployment because they’re operators. Users with admin on a project shouldn’t be able to manage things outside the project because it would violate the tenancy of their role assignment (this doesn’t apply consistently since services are addressing this individually at their own pace).

System Personas

This section describes authorization personas typically used for operators and deployers. You can find all users with system role assignments using the following query:

$ openstack role assignment list --names --system all
+--------+------------------------+------------------------+---------+--------+--------+-----------+
| Role   | User                   | Group                  | Project | Domain | System | Inherited |
+--------+------------------------+------------------------+---------+--------+--------+-----------+
| admin  |                        | system-admins@Default  |         |        | all    | False     |
| admin  | admin@Default          |                        |         |        | all    | False     |
| admin  | operator@Default       |                        |         |        | all    | False     |
| reader |                        | system-support@Default |         |        | all    | False     |
| admin  | operator@Default       |                        |         |        | all    | False     |
| member | system-support@Default |                        |         |        | all    | False     |
+--------+------------------------+------------------------+---------+--------+--------+-----------+

System Administrators

System administrators are allowed to manage every resource in keystone. System administrators are typically operators and cloud administrators. They can control resources that ultimately affect the behavior of the deployment. For example, they can add or remove services and endpoints in the catalog, create new domains, add federated mappings, and clean up stale resources, like a user’s application credentials or trusts.

You can find system administrators in your deployment with the following assignments:

$ openstack role assignment list --names --system all --role admin
+-------+------------------+-----------------------+---------+--------+--------+-----------+
| Role  | User             | Group                 | Project | Domain | System | Inherited |
+-------+------------------+-----------------------+---------+--------+--------+-----------+
| admin |                  | system-admins@Default |         |        | all    | False     |
| admin | admin@Default    |                       |         |        | all    | False     |
| admin | operator@Default |                       |         |        | all    | False     |
+-------+------------------+-----------------------+---------+--------+--------+-----------+

System Members & System Readers

In keystone, system members and system readers are very similar and have the same authorization. Users with these roles on the system can view all resources within keystone. They can list role assignments, users, projects, and group memberships, among other resources.

The system reader persona is useful for members of a support team or auditors if the audit doesn’t require access to sensitive information. You can find system members and system readers in your deployment with the following assignments:

$ openstack role assignment list --names --system all --role member --role reader
+--------+------------------------+------------------------+---------+--------+--------+-----------+
| Role   | User                   | Group                  | Project | Domain | System | Inherited |
+--------+------------------------+------------------------+---------+--------+--------+-----------+
| reader |                        | system-support@Default |         |        | all    | False     |
| admin  | operator@Default       |                        |         |        | all    | False     |
| member | system-support@Default |                        |         |        | all    | False     |
+--------+------------------------+------------------------+---------+--------+--------+-----------+

Domain Personas

This section describes authorization personas for people who manage their own domains, which contain projects, users, and groups. You can find all users with role assignments on a specific domain using the following query:

$ openstack role assignment list --names --domain foobar
+--------+-----------------+----------------------+---------+--------+--------+-----------+
| Role   | User            | Group                | Project | Domain | System | Inherited |
+--------+-----------------+----------------------+---------+--------+--------+-----------+
| reader | support@Default |                      |         | foobar |        | False     |
| admin  | jsmith@Default  |                      |         | foobar |        | False     |
| admin  |                 | foobar-admins@foobar |         | foobar |        | False     |
| member | jdoe@foobar     |                      |         | foobar |        | False     |
+--------+-----------------+----------------------+---------+--------+--------+-----------+

Domain Administrators

Domain administrators can manage most aspects of the domain or its contents. These users can create new projects and users within their domain. They can inspect the role assignments users have on projects within their domain.

Domain administrators aren’t allowed to access system-specific resources or resources outside their domain. Users that need control over project, group, and user creation are a great fit for domain administrators.

You can find domain administrators in your deployment with the following role assignment:

$ openstack role assignment list --names --domain foobar --role admin
+-------+----------------+----------------------+---------+--------+--------+-----------+
| Role  | User           | Group                | Project | Domain | System | Inherited |
+-------+----------------+----------------------+---------+--------+--------+-----------+
| admin | jsmith@Default |                      |         | foobar |        | False     |
| admin |                | foobar-admins@foobar |         | foobar |        | False     |
+-------+----------------+----------------------+---------+--------+--------+-----------+

Domain Members & Domain Readers

Domain members and domain readers have the same relationship as system members and system readers. They’re allowed to view resources and information about their domain. They aren’t allowed to access system-specific information or information about projects, groups, and users outside their domain.

The domain member and domain reader use-cases are great for support teams, monitoring the details of an account, or auditing resources within a domain assuming the audit doesn’t validate sensitive information. You can find domain members and domain readers with the following role assignments:

$ openstack role assignment list --names --role member --domain foobar
+--------+-------------+-------+---------+--------+--------+-----------+
| Role   | User        | Group | Project | Domain | System | Inherited |
+--------+-------------+-------+---------+--------+--------+-----------+
| member | jdoe@foobar |       |         | foobar |        | False     |
+--------+-------------+-------+---------+--------+--------+-----------+
$ openstack role assignment list --names --role reader --domain foobar
+--------+-----------------+-------+---------+--------+--------+-----------+
| Role   | User            | Group | Project | Domain | System | Inherited |
+--------+-----------------+-------+---------+--------+--------+-----------+
| reader | support@Default |       |         | foobar |        | False     |
+--------+-----------------+-------+---------+--------+--------+-----------+

Project Personas

This section describes authorization personas for users operating within a project. These personas are commonly used by end users. You can find all users with role assignments on a specific project using the following query:

$ openstack role assignment list --names --project production
+--------+----------------+----------------------------+-------------------+--------+--------+-----------+
| Role   | User           | Group                      | Project           | Domain | System | Inherited |
+--------+----------------+----------------------------+-------------------+--------+--------+-----------+
| admin  | jsmith@Default |                            | production@foobar |        |        | False     |
| admin  |                | production-admins@foobar   | production@foobar |        |        | False     |
| member |                | foobar-operators@Default   | production@foobar |        |        | False     |
| reader | alice@Default  |                            | production@foobar |        |        | False     |
| reader |                | production-support@Default | production@foobar |        |        | False     |
+--------+----------------+----------------------------+-------------------+--------+--------+-----------+

Project Administrators

Project administrators can only view and modify data within the project they have authorization on. They’re able to view information about their projects and set tags on their projects. They’re not allowed to view system or domain resources, as that would violate the tenancy of their role assignment. Since the majority of the resources in keystone’s API are system and domain-specific, project administrators don’t have much authorization.

You can find project administrators in your deployment with the following role assignment:

$ openstack role assignment list --names --project production --role admin
+-------+----------------+--------------------------+-------------------+--------+--------+-----------+
| Role  | User           | Group                    | Project           | Domain | System | Inherited |
+-------+----------------+--------------------------+-------------------+--------+--------+-----------+
| admin | jsmith@Default |                          | production@foobar |        |        | False     |
| admin |                | production-admins@foobar | production@foobar |        |        | False     |
+-------+----------------+--------------------------+-------------------+--------+--------+-----------+

Project Members & Project Readers

Project members and project readers can discover information about their projects. They can access important information like resource limits for their project, but they’re not allowed to view information outside their project or view system-specific information.

You can find project members and project readers in your deployment with the following role assignments:

$ openstack role assignment list --names --project production --role member
+--------+------+--------------------------+-------------------+--------+--------+-----------+
| Role   | User | Group                    | Project           | Domain | System | Inherited |
+--------+------+--------------------------+-------------------+--------+--------+-----------+
| member |      | foobar-operators@Default | production@foobar |        |        | False     |
+--------+------+--------------------------+-------------------+--------+--------+-----------+
$ openstack role assignment list --names --project production --role reader
+--------+---------------+----------------------------+-------------------+--------+--------+-----------+
| Role   | User          | Group                      | Project           | Domain | System | Inherited |
+--------+---------------+----------------------------+-------------------+--------+--------+-----------+
| reader | alice@Default |                            | production@foobar |        |        | False     |
| reader |               | production-support@Default | production@foobar |        |        | False     |
+--------+---------------+----------------------------+-------------------+--------+--------+-----------+

Writing Policies

If the granularity provided above doesn’t meet your specific use-case, you can still override policies and maintain them manually. You can read more about how to do that in oslo.policy usage documentation.