1. Prerequisite for configuring gatekeeper for a specific application:

create a client, called my-app in Keycloak. In the creation step select access-type: confidential
once created you will see a credentials tab for the newly created client with the secret. You will need that for the gatekeeper.yaml config file
create Realm role for that application my-app-role
create a group my-group and add the role my-app-role in role-mappings of the group
go to your user and add it to the my-group. This user will be authorized to access the secured application, once we configure it

2. Create a gatekeeper configuration file, gatekeeper.yaml, as a secret

client-id: my-app

client-secret: my-app-secret-from-credentials

discovery-url: https://my-keycloak-server.com/auth/realms/my-realm

skip-upstream-tls-verify: false

skip-openid-provider-tls-verify: true

encryption-key: random-secret-value-of-16-or-32-characters

listen: 0.0.0.0:3000

secure-cookie: false

enable-logging: true

enable-json-logging: true

enable-default-deny: true

enable-refresh-tokens: true

enable-session-cookies: true

debug: true

ingress.enabled: true

resources:

  - uri: /favicon

  white-listed: true

Values to be replaced and set in the above config file:

client-secret set from the client credentials tab
encryption-key random hash value 16 or 32 characters
discovery-url keycloak endpoint

Some of the important values explained:

discovery-url is keycloak's realm url that the my-app client resides in
skip-openid-provider-tls-verify ignores Keycloak's self-signed certificate warning for gatekeeper client request
enable-default-deny - all resources are by default secured unless explicitly allowed in resources
listen - port where the gatekeeper will start and listen on
redirection-url - where the successful login will be redirected to
upstream-url - where gatekeeper will forward the request after successful authorization
resources configures which resources can be accessed (white-listed) without authentication.

The configuration values are needed by the gatekeeper to communicate with Keycloak. So with the endpoint, we tell gatekeeper where to find the Keycloak server to talk to, with the client-id and client-secret gatekeeper can authenticate itself with Keycloak to make requests to it.

kubectl create secret generic gatekeeper --from-file= ./gatekeeper.yaml -n my-namespace

Now that you have set up all the necessary configuration, you need to deploy gatekeeper container inside the pod where the application you want to secure is running. SO gatekeeper will be a side-car container to your actual app, acting as a... well, gatekeeper to all incoming requests.

So to deploy both containers inside one pod, you need to configure it like this:

apiVersion: apps/v1

kind: Deployment

metadata:

  name: my-app

spec: 

  template:

    ...

    spec:

      containers:

      - image: keycloak/keycloak-gatekeeper:7.0.0

        name: gatekeeper

        ports:

        - containerPort: 3000

        args:

        - --config=/etc/secrets/gatekeeper.yaml

        - --redirection-url=https://my-app-server-url

        - --upstream-url=http://127.0.0.1:8080

        - --resources=uri=/*|roles=my-app-role

        volumeMounts:

        - name: gatekeeper-secrets

          mountPath: /etc/secrets

      - image: my-app-image

        name: my-app

        ports:

        - containerPort: 8080

      volumes:

      - name: gatekeeper-secrets

        secret:

          secretName: gatekeeper

So with the above configuration, a pod will be created with the application and gatekeeper containers and the gatekeeper.yaml file that we created above will be mounted inside the gatekeeper container.

As you see in the deployment config, gatekeeper container has args configured.

redirection-url is where the successful login will be redirected to. This points to the url of the my-app, which will also land with the gatekeeper
upstream-url - after the redirect-url is called for the authenticated user, gatekeeper will allow access to my-app, by forwarding the request to it on http://127.0.0.1:8080.

Why http://127.0.0.1:8080? because both my-app and gatekeeper run in the same pod, they can communicate via localhost.

So, now we need to configure the service for my-app to forward the incoming requests NOT to my-app, but to the gatekeeper container. As you see from above my-app and gatekeeper are running on different ports (8080 and 3000), so we just need to tell the service to forward the request to gatekeeper's port 3000.

apiVersion: v1

kind: Service

metadata:

  name: my-service

spec:

  selector:

    service: my-service

  type: ClusterIP

  ports:

  - port: 32111

    targetPort: 3000

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How to setup a Keycloak Gatekeeper to secure the services in your Kubernetes cluster