Access to KubeVirt resources are controlled entirely by Kubernete’s Resource Based Access Control (RBAC) system. This system allows KubeVirt to tie directly into the existing authentication and authorization mechanisms Kubernetes already provides to its core api objects.

KubeVirt RBAC Role Basics

Typically, when people think of Kubernetes RBAC system, they’re thinking about granting users access to create/delete kubernetes objects (like Pods, deployments, etc), however those same RBAC mechanisms work naturally with KubeVirt objects as well.

When we look at KubeVirt’s objects, we can see they are structured just like the objects that come predefined in the Kubernetes core.

For example, look here’s an example of a VirtualMachine spec.

apiVersion: kubevirt.io/v1alpha1
kind: VirtualMachine
metadata:
  name: vm-ephemeral
spec:
  domain:
    devices:
      disks:
      - disk:
          bus: virtio
        name: registrydisk
        volumeName: registryvolume
    resources:
      requests:
        memory: 64M
  volumes:
  - name: registryvolume
    registryDisk:
      image: kubevirt/cirros-registry-disk-demo:devel

In the spec above, we see the KubeVirt VirtualMachine object has an apiVersion field and a kind field just like a Pod spec does. The kubevirt.io portion of the apiVersion field represents KubeVirt apiGroup the resource is a part of. The kind field reflects the resource type.

Using that information, we can create an RBAC role that gives a user permission to create, delete, and view all VirtualMachine objects.

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: vm-access
  labels:
    kubevirt.io: ""
rules:
  - apiGroups:
      - kubevirt.io
    resources:
      - virtualmachines
    verbs:
      - get
      - delete
      - create
      - update
      - patch
      - list
      - watch

This same logic can be applied when creating RBAC roles for other KubeVirt objects as well. If we wanted to extend this RBAC role to grant similar permissions for VirtualMachinePreset objects, we’d just have to add a second resource kubevirt.io resource list. The result would look like this.

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: vm-access
  labels:
    kubevirt.io: ""
rules:
  - apiGroups:
      - kubevirt.io
    resources:
      - virtualmachines
      - virtualmachinepresets
    verbs:
      - get
      - delete
      - create
      - update
      - patch
      - list
      - watch

KubeVirt Subresource RBAC Roles

Access to a VirtualMachines’s VNC and console stream using KubeVirt’s virtctl tool is managed by the Kubernetes RBAC system as well. Permissions for these resources work slightly different than the other KubeVirt objects though.

Console and VNC access is performed using the KubeVirt Stream API, which has its own api group called subresources.kubevirt.io. Below is an example of how to create a role that grants access to the VNC and console streams APIs.

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: vm-vnc-access
  labels:
    kubevirt.io: ""
rules:
  - apiGroups:
      - subresources.kubevirt.io
    resources:
      - virtualmachines/console
      - virtualmachines/vnc
    verbs:
      - get

Limiting RBAC To a Single Namespace.

A ClusterRole can be bound to a user in two different ways.

When a ClusterRoleBinding is used, a user is permitted access to all resources defined in the ClusterRole across all namespaces in the cluster.

When a RoleBinding is used, a user is limited to accessing only the resources defined in the ClusterRole within the namespace RoleBinding exists in.

Limiting RBAC To a Single Resource.

A user can also be limit to accessing only a single resource within a resource type. Below is an example that only grants VNC access to the VirtualMachine named ‘bobs-vm’

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: vm-vnc-access
  labels:
    kubevirt.io: ""
rules:
  - apiGroups:
      - subresources.kubevirt.io
    resources:
      - virtualmachines/console
      - virtualmachines/vnc
    resourceName:
      - bobs-vm
    verbs:
      - get

Default KubeVirt RBAC Roles

The next release of KubeVirt is coming with three default ClusterRoles that admins can use to grant users access to KubeVirt resources. In most cases, these roles will prevent admins from ever having to create their own custom KubeVirt RBAC roles.

More information about these default roles can be found in the KubeVirt user guide here