RBAC overview

Role-based access control (RBAC) objects determine whether a user is allowed to perform a given action within a project.

Developers can use local roles and bindings to control who has access to their projects. Note that authorization is a separate step from authentication, which is more about determining the identity of who is taking the action.

Authorization is managed using:

Rules

Sets of permitted verbs on a set of objects. For example, whether a user or service account can create pods.

Roles

Collections of rules. You can associate, or bind, users and groups to multiple roles.

Bindings

Associations between users and/or groups with a role.

There are two levels of RBAC roles and bindings that control authorization:

Cluster RBAC

Roles and bindings that are applicable across all projects. Cluster roles exist cluster-wide, and cluster role bindings can reference only cluster roles.

Local RBAC

Roles and bindings that are scoped to a given project. While local roles exist only in a single project, local role bindings can reference both cluster and local roles.

A cluster role binding is a binding that exists at the cluster level. A role binding exists at the project level. The cluster role view must be bound to a user using a local role binding for that user to view the project. Create local roles only if a cluster role does not provide the set of permissions needed for a particular situation.

This two-level hierarchy allows reuse across multiple projects through the cluster roles while allowing customization inside of individual projects through local roles.

During evaluation, both the cluster role bindings and the local role bindings are used. For example:

  1. Cluster-wide "allow" rules are checked.

  2. Locally-bound "allow" rules are checked.

  3. Deny by default.

Default cluster roles

OpenShift Dedicated includes a set of default cluster roles that you can bind to users and groups cluster-wide or locally. You can manually modify the default cluster roles, if required, but you must take extra steps each time you restart a master node.

Default Cluster Role Description

admin

A project manager. If used in a local binding, an admin has rights to view any resource in the project and modify any resource in the project except for quota.

basic-user

A user that can get basic information about projects and users.

cluster-admin

A super-user that can perform any action in any project. When bound to a user with a local binding, they have full control over quota and every action on every resource in the project.

cluster-status

A user that can get basic cluster status information.

edit

A user that can modify most objects in a project but does not have the power to view or modify roles or bindings.

self-provisioner

A user that can create their own projects.

view

A user who cannot make any modifications, but can see most objects in a project. They cannot view or modify roles or bindings.

Be mindful of the difference between local and cluster bindings. For example, if you bind the cluster-admin role to a user by using a local role binding, it might appear that this user has the privileges of a cluster administrator. This is not the case. Binding the cluster-admin to a user in a project grants super administrator privileges for only that project to the user. That user has the permissions of the cluster role admin, plus a few additional permissions like the ability to edit rate limits, for that project. This binding can be confusing via the web console UI, which does not list cluster role bindings that are bound to true cluster administrators. However, it does list local role bindings that you can use to locally bind cluster-admin.

The relationships between cluster roles, local roles, cluster role bindings, local role bindings, users, groups and service accounts are illustrated below.

OpenShift Dedicated RBAC

Evaluating authorization

OpenShift Dedicated evaluates authorization by using:

Identity

The user name and list of groups that the user belongs to.

Action

The action you perform. In most cases, this consists of:

  • Project: The project you access. A project is a Kubernetes namespace with additional annotations that allows a community of users to organize and manage their content in isolation from other communities.

  • Verb : The action itself: get, list, create, update, delete, deletecollection, or watch.

  • Resource Name: The API endpoint that you access.

Bindings

The full list of bindings, the associations between users or groups with a role.

OpenShift Dedicated evaluates authorization by using the following steps:

  1. The identity and the project-scoped action is used to find all bindings that apply to the user or their groups.

  2. Bindings are used to locate all the roles that apply.

  3. Roles are used to find all the rules that apply.

  4. The action is checked against each rule to find a match.

  5. If no matching rule is found, the action is then denied by default.

Remember that users and groups can be associated with, or bound to, multiple roles at the same time.

Project administrators can visualize roles, including a matrix of the verbs and resources each are associated using the CLI to view local bindings.

The cluster role bound to the project administrator is limited in a project through a local binding. It is not bound cluster-wide like the cluster roles granted to the cluster-admin or system:admin.

Cluster roles are roles defined at the cluster level but can be bound either at the cluster level or at the project level.

Projects and namespaces

A Kubernetes namespace provides a mechanism to scope resources in a cluster. The Kubernetes documentation has more information on namespaces.

Namespaces provide a unique scope for:

  • Named resources to avoid basic naming collisions.

  • Delegated management authority to trusted users.

  • The ability to limit community resource consumption.

Most objects in the system are scoped by namespace, but some are excepted and have no namespace, including nodes and users.

A project is a Kubernetes namespace with additional annotations and is the central vehicle by which access to resources for regular users is managed. A project allows a community of users to organize and manage their content in isolation from other communities. Users must be given access to projects by administrators, or if allowed to create projects, automatically have access to their own projects.

Projects can have a separate name, displayName, and description.

  • The mandatory name is a unique identifier for the project and is most visible when using the CLI tools or API. The maximum name length is 63 characters.

  • The optional displayName is how the project is displayed in the web console (defaults to name).

  • The optional description can be a more detailed description of the project and is also visible in the web console.

Each project scopes its own set of:

Objects

Pods, services, replication controllers, etc.

Policies

Rules for which users can or cannot perform actions on objects.

Constraints

Quotas for each kind of object that can be limited.

Service accounts

Service accounts act automatically with designated access to objects in the project.

Cluster administrators can create projects and delegate administrative rights for the project to any member of the user community. Cluster administrators can also allow developers to create their own projects.

Developers and administrators can interact with projects the CLI or the web console.

Default projects

OpenShift Dedicated comes with a number of default projects, and projects starting with openshift- are the most essential to users. These projects host master components that run as pods and other infrastructure components. The pods created in these namespaces that have a critical pod annotation are considered critical, and the have guaranteed admission by kubelet. Pods created for master components in these namespaces are already marked as critical.

Viewing cluster roles and bindings

You can use the oc CLI to view cluster roles and bindings by using the oc describe command.

Prerequisites
  • Install the oc CLI.

  • Obtain permission to view the cluster roles and bindings. Users with the dedicated-admins-cluster role can view cluster roles and bindings.

Procedure
  1. To view the cluster roles and their associated rule sets:

$ oc describe clusterrole.rbac
  1. To view the current set of cluster role bindings, which shows the users and groups that are bound to various roles:

$ oc describe clusterrolebinding.rbac

Viewing local roles and bindings

You can use the oc CLI to view local roles and bindings by using the oc describe command.

Prerequisites
  • Install the oc CLI.

  • Obtain permission to view the local roles and bindings:

    • Users with the dedicated-admins-cluster role can view and manage local roles and bindings.

    • Users with the admin default cluster role bound locally can view and manage roles and bindings in that project.

Procedure
  1. To view the current set of local role bindings, which show the users and groups that are bound to various roles for the current project:

    $ oc describe rolebinding.rbac
  2. To view the local role bindings for a different project, add the -n flag to the command:

    $ oc describe rolebinding.rbac -n joe-project
    Name:         admin
    Labels:       <none>
    Annotations:  <none>
    Role:
      Kind:  ClusterRole
      Name:  admin
    Subjects:
      Kind  Name        Namespace
      ----  ----        ---------
      User  kube:admin
    
    
    Name:         system:deployers
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows deploymentconfigs in this namespace to rollout pods in
                    this namespace.  It is auto-managed by a controller; remove
                    subjects to disa...
    Role:
      Kind:  ClusterRole
      Name:  system:deployer
    Subjects:
      Kind            Name      Namespace
      ----            ----      ---------
      ServiceAccount  deployer  joe-project
    
    
    Name:         system:image-builders
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows builds in this namespace to push images to this
                    namespace.  It is auto-managed by a controller; remove subjects
                    to disable.
    Role:
      Kind:  ClusterRole
      Name:  system:image-builder
    Subjects:
      Kind            Name     Namespace
      ----            ----     ---------
      ServiceAccount  builder  joe-project
    
    
    Name:         system:image-pullers
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows all pods in this namespace to pull images from this
                    namespace.  It is auto-managed by a controller; remove subjects
                    to disable.
    Role:
      Kind:  ClusterRole
      Name:  system:image-puller
    Subjects:
      Kind   Name                                Namespace
      ----   ----                                ---------
      Group  system:serviceaccounts:joe-project

Adding roles to users

You can use the oc adm administrator CLI to manage the roles and bindings.

Dedicated administrators cannot manage cluster roles. They can manage cluster role bindings and local roles and bindings.

Binding, or adding, a role to users or groups gives the user or group the access that is granted by the role. You can add and remove roles to and from users and groups using oc adm policy commands.

You can bind any of the default cluster roles to local users or groups in your project.

Procedure
  1. Add a role to a user in a specific project:

    $ oc adm policy add-role-to-user <role> <user> -n <project>

    For example, you can add the admin role to the alice user in joe project by running:

    $ oc adm policy add-role-to-user admin alice -n joe
  2. View the local role bindings and verify the addition in the output:

    $ oc describe rolebinding.rbac -n <project>

    For example, to view the local role bindings for the joe project:

    $ oc describe rolebinding.rbac -n joe
    Name:         admin
    Labels:       <none>
    Annotations:  <none>
    Role:
      Kind:  ClusterRole
      Name:  admin
    Subjects:
      Kind  Name        Namespace
      ----  ----        ---------
      User  kube:admin
    
    
    Name:         admin-0
    Labels:       <none>
    Annotations:  <none>
    Role:
      Kind:  ClusterRole
      Name:  admin
    Subjects:
      Kind  Name   Namespace
      ----  ----   ---------
      User  alice (1)
    
    
    Name:         system:deployers
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows deploymentconfigs in this namespace to rollout pods in
                    this namespace.  It is auto-managed by a controller; remove
                    subjects to disa...
    Role:
      Kind:  ClusterRole
      Name:  system:deployer
    Subjects:
      Kind            Name      Namespace
      ----            ----      ---------
      ServiceAccount  deployer  joe
    
    
    Name:         system:image-builders
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows builds in this namespace to push images to this
                    namespace.  It is auto-managed by a controller; remove subjects
                    to disable.
    Role:
      Kind:  ClusterRole
      Name:  system:image-builder
    Subjects:
      Kind            Name     Namespace
      ----            ----     ---------
      ServiceAccount  builder  joe
    
    
    Name:         system:image-pullers
    Labels:       <none>
    Annotations:  openshift.io/description:
                    Allows all pods in this namespace to pull images from this
                    namespace.  It is auto-managed by a controller; remove subjects
                    to disable.
    Role:
      Kind:  ClusterRole
      Name:  system:image-puller
    Subjects:
      Kind   Name                                Namespace
      ----   ----                                ---------
      Group  system:serviceaccounts:joe
    1 The alice user has been added to the admins RoleBinding.

Local role binding commands

When you manage a user or group’s associated roles for local role bindings using the following operations, a project may be specified with the -n flag. If it is not specified, then the current project is used.

You can use the following commands for local RBAC management.

Table 1. Local role binding operations
Command Description

$ oc adm policy who-can <verb> <resource>

Indicates which users can perform an action on a resource.

$ oc adm policy add-role-to-user <role> <username>

Binds a specified role to specified users in the current project.

$ oc adm policy remove-role-from-user <role> <username>

Removes a given role from specified users in the current project.

$ oc adm policy remove-user <username>

Removes specified users and all of their roles in the current project.

$ oc adm policy add-role-to-group <role> <groupname>

Binds a given role to specified groups in the current project.

$ oc adm policy remove-role-from-group <role> <groupname>

Removes a given role from specified groups in the current project.

$ oc adm policy remove-group <groupname>

Removes specified groups and all of their roles in the current project.