Zuul dd30a921a2 Merge "Implement the Domain Manager Persona for Keystone"

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Default Roles

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.

In addition to admin, member, and reader role, from 2023.2 (Bobcat) release keystone will provide the service and manager roles by default as well. Operators can use the service role for service to service API calls instead of using admin role for the same. The service role will be separate from admin, member, reader and will not implicate any of these roles. Operators can give the manager role to users to within a domain to enable self-service management of users, groups, projects and role assignments within their domain.

Roles Definitions

The default roles provided by keystone via keystone-manage bootstrap (except for the service role) are related through role implications. The admin role implies the manager role, the manager implies the member role, and the member role implies the reader role. These implications mean users with the admin role automatically have the manager, member and reader roles. Additionally, users with the manager role automatically have the member and reader roles. 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:manager or role:member or role:reader"

Reader

Warning

While it's possible to use the reader role to perform audits, we highly recommend assessing the viability of using reader for auditing from the perspective of the compliance target you're pursuing.

The reader role is the least-privileged role within the role hierarchy described here. As such, OpenStack development teams, by default, do not advocate exposing sensitive information to users with the reader role, regardless of the scope. We have noted the need for a formal, read-only, role that is useful for inspecting all applicable resources within a particular scope, but it shouldn't be implemented as the lowest level of authorization. This work will come in a subsequent release where we support an elevated read-only role, that implies reader, but also exposes sensitive information, where applicable.

This will allow operators to grant third-party auditors a permissive role for viewing sensitive information, specifically for compliance targets that require it.

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.

Manager

The manager role takes a special place in keystone. It sits between the admin and member role, allowing limited identity management while being clearly differentiated from the admin role both in terms of purpose and privileges. The manager role is meant to be assigned in a domain scope and enables users to manage identity assets in a whole domain including users, projects, groups and role assignments. This enables identity self-service management capabilities for users within a domain without the need to assign the most privileged admin role to them.

The keystone default policies include a special rule that specifies the list of roles a user with the manager role is be able to assign and revoke within the domain scope. This prevents such user from escalating their own privileges or those of others beyond manager and for this purpose the list excludes the admin role. The list can be adjusted by cloud administrators via policy definitions in case the role model differs. For example, if a new role is introduced for a specific cloud environment, the list can be adjusted to allow users with the manager role to also assign it.

Other services might write default policies to enable the manager role to have more privileged managing rights or cross-project privileges in a domain.

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).

Service

We reserve the service role for Service-to-service communication. The aim of a service role is to allow a service to communicate with another service and possibly be granted elevated privileges by the service receiving the request. Before the introduction of the service role, a service had to be granted the admin role in order to have elevated privileges, which gave a service powers way beyond what was necessary. With the service role in place, we can now allow all service-to-service APIs to default to the service role only. For example, a policy that requires service can be expressed as:

"identity:create_foo": "role:service"

There might be exception service-to-service APIs which project think are useful to be used by admin or non-admin user then they can take the exceptional decision to default them to user role and service role. For example, a policy that requires service and admin can be expressed as:

"identity:create_foo": "role:service or role:admin"

Note

Unlike the other default roles, the service role is not a member of a role hierarchy. It is a standalone role.

Note

As of the Train release, keystone applies the following personas consistently across its API.

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     |
+--------+------------------------+------------------------+---------+--------+--------+-----------+

Warning

Filtering system role assignments is currently broken and is being tracked as a bug.

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     |
| manager | alice@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 Managers

Domain managers can only manage specific resources related to identity management within their domain. This includes creating new users, projects and groups as well as updating and deleting them. They can also assign and revoke roles between those or in relation to the domain. Furthermore, they can inspect role assignments within the domain.

Domain managers cannot change any aspects of the domain itself. The role assignments they can apply within their domain is limited to a specific list of applicable roles and in the default configuration, this excludes the admin role to prevent privilege escalation.

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

$ openstack role assignment list --names --domain foobar --role manager
+---------+-----------------+----------------------+---------+--------+--------+-----------+
| Role    | User            | Group                | Project | Domain | System | Inherited |
+---------+-----------------+----------------------+---------+--------+--------+-----------+
| manager | alice@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.

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