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Using Custom RBAC resources

KubeDB (version 0.13.0 and higher) supports finer user control over role based access permissions provided to an Elasticsearch instance. This tutorial will show you how to use KubeDB to run Elasticsearch instance with custom RBAC resources.

Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.

To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/elasticsearch folder in GitHub repository kubedb/docs.

Overview

KubeDB allows users to provide custom RBAC resources, namely, ServiceAccount, Role, and RoleBinding for Elasticsearch. This is provided via the spec.podTemplate.spec.serviceAccountName field in Elasticsearch crd. If this field is left empty, the KubeDB operator will create a service account name matching Elasticsearch crd name. Role and RoleBinding that provide necessary access permissions will also be generated automatically for this service account.

If a service account name is given, but there’s no existing service account by that name, the KubeDB operator will create one, and Role and RoleBinding that provide necessary access permissions will also be generated for this service account.

If a service account name is given, and there’s an existing service account by that name, the KubeDB operator will use that existing service account. Since this service account is not managed by KubeDB, users are responsible for providing necessary access permissions manually.

This guide will show you how to create custom Service Account, Role, and RoleBinding for an Elasticsearch Database named quick-elasticsearch to provide the bare minimum access permissions.

Custom RBAC for Elasticsearch

At first, let’s create a Service Acoount in demo namespace.

$ kubectl create serviceaccount -n demo my-custom-serviceaccount
serviceaccount/my-custom-serviceaccount created

It should create a service account.

$ kubectl get serviceaccount -n demo my-custom-serviceaccount -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-10-02T05:18:37Z"
  name: my-custom-serviceaccount
  namespace: demo
  resourceVersion: "15521"
  selfLink: /api/v1/namespaces/demo/serviceaccounts/my-custom-serviceaccount
  uid: 16cf2f6c-e4d4-11e9-b2b2-42010a940225
secrets:
- name: my-custom-serviceaccount-token-ptt25

Now, we need to create a role that has necessary access permissions for the Elasticsearch instance named quick-elasticsearch.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/elasticsearch/custom-rbac/es-custom-role.yaml
role.rbac.authorization.k8s.io/my-custom-role created

Below is the YAML for the Role we just created.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: my-custom-role
  namespace: demo
rules:
- apiGroups:
  - policy
  resourceNames:
  - elasticsearch-db
  resources:
  - podsecuritypolicies
  verbs:
  - use

This permission is required for Elasticsearch pods running on PSP enabled clusters.

Now create a RoleBinding to bind this Role with the already created service account.

$ kubectl create rolebinding my-custom-rolebinding --role=my-custom-role --serviceaccount=demo:my-custom-serviceaccount --namespace=demo
rolebinding.rbac.authorization.k8s.io/my-custom-rolebinding created

It should bind my-custom-role and my-custom-serviceaccount successfully.

$ kubectl get rolebinding -n demo my-custom-rolebinding -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  creationTimestamp: "2019-10-02T05:19:37Z"
  name: my-custom-rolebinding
  namespace: demo
  resourceVersion: "15726"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/demo/rolebindings/my-custom-rolebinding
  uid: 3a5e9277-e4d4-11e9-b2b2-42010a940225
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: my-custom-role
subjects:
- kind: ServiceAccount
  name: my-custom-serviceaccount
  namespace: demo

Now, create an Elasticsearch crd specifying spec.podTemplate.spec.serviceAccountName field to my-custom-serviceaccount.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/elasticsearch/custom-rbac/es-custom-db.yaml
elasticsearch.kubedb.com/quick-elasticsearch created

Below is the YAML for the Elasticsearch crd we just created.

apiVersion: kubedb.com/v1alpha2
kind: Elasticsearch
metadata:
  name: quick-elasticsearch
  namespace: demo
spec:
  version: 7.3.2
  storageType: Durable
  podTemplate:
    spec:
      serviceAccountName: my-custom-serviceaccount
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: DoNotTerminate
$ kubectl get es -n demo
NAME                  VERSION   STATUS    AGE
quick-elasticsearch   7.3.2     Running   74s

Now, wait a few minutes. the KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we should see that a pod with the name quick-elasticsearch-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo quick-elasticsearch-0
NAME                    READY   STATUS    RESTARTS   AGE
quick-elasticsearch-0   1/1     Running   0          93s

Reusing Service Account

An existing service account can be reused in another Elasticsearch Database. No new access permission is required to run the new Elasticsearch Database.

Now, create Elasticsearch crd minute-elasticsearch using the existing service account name my-custom-serviceaccount in the spec.podTemplate.spec.serviceAccountName field.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/elasticsearch/custom-rbac/es-custom-db-two.yaml
elasticsearch.kubedb.com/quick-elasticsearch created

Below is the YAML for the Elasticsearch crd we just created.

apiVersion: kubedb.com/v1alpha2
kind: Elasticsearch
metadata:
  name: minute-elasticsearch
  namespace: demo
spec:
  version: 7.3.2
  storageType: Durable
  podTemplate:
    spec:
      serviceAccountName: my-custom-serviceaccount
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: DoNotTerminate
$ kubectl get es -n demo
NAME                   VERSION   STATUS    AGE
minute-elasticsearch   7.3.2     Running   59s
quick-elasticsearch    7.3.2     Running   3m17s

Now, wait a few minutes. the KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we should see that a pod with the name minute-elasticsearch-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo minute-elasticsearch-0
NAME                     READY   STATUS    RESTARTS   AGE
minute-elasticsearch-0   1/1     Running   0          71s

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo es/quick-elasticsearch -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo es/quick-elasticsearch

kubectl patch -n demo es/minute-elasticsearch -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo es/minute-elasticsearch

kubectl delete -n demo role my-custom-role
kubectl delete -n demo rolebinding my-custom-rolebinding

kubectl delete sa -n demo my-custom-serviceaccount

kubectl delete ns demo

If you would like to uninstall the KubeDB operator, please follow the steps here.

Next Steps