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User guide: Kubernetes RBAC for service authorization (SubjectAccessReview API)

Manage permissions in the Kubernetes RBAC and let Authorino to check them in request-time with the authorization system of the cluster.

Authorino capabilities featured in this guide:

Authorino can delegate authorization decision to the Kubernetes authorization system, allowing permissions to be stored and managed using the Kubernetes Role-Based Access Control (RBAC) for example. The feature is based on the SubjectAccessReview API and can be used for resourceAttributes (parameters defined in the AuthConfig) or nonResourceAttributes (inferring HTTP path and verb from the original request).

Check out as well the user guide about Authentication with Kubernetes tokens (TokenReview API).

For further details about Authorino features in general, check the docs.


Requirements

  • Kubernetes server with permissions to install cluster-scoped resources (operator, CRDs and RBAC) and to create TokenRequests (to consume the protected service from outside the cluster)
  • jq

If you do not own a Kubernetes server already and just want to try out the steps in this guide, you can create a local containerized cluster by executing the command below. In this case, the main requirement is having Kind installed, with either Docker or Podman.

kind create cluster --name authorino-tutorial

The next steps walk you through installing Authorino, deploying and configuring a sample service called Talker API to be protected by the authorization service.

Using Kuadrant

If you are a user of Kuadrant and already have your workload cluster configured and sample service application deployed, as well as your Gateway API network resources applied to route traffic to your service, skip straight to step ❺.

At step ❺, instead of creating an AuthConfig custom resource, create a Kuadrant AuthPolicy one. The schema of the AuthConfig's spec matches the one of the AuthPolicy's, except spec.host, which is not available in the Kuadrant AuthPolicy. Host names in a Kuadrant AuthPolicy are inferred automatically from the Kubernetes network object referred in spec.targetRef and route selectors declared in the policy.

For more about using Kuadrant to enforce authorization, check out Kuadrant auth.

❶ Install the Authorino Operator (cluster admin required)

The following command will install the Authorino Operator in the Kubernetes cluster. The operator manages instances of the Authorino authorization service.

curl -sL https://raw.githubusercontent.com/Kuadrant/authorino-operator/main/utils/install.sh | bash -s

❷ Deploy Authorino

The following command will request an instance of Authorino as a separate service1 that watches for AuthConfig resources in the default namespace2, with TLS disabled3.

kubectl apply -f -<<EOF
apiVersion: operator.authorino.kuadrant.io/v1beta1
kind: Authorino
metadata:
  name: authorino
spec:
  listener:
    tls:
      enabled: false
  oidcServer:
    tls:
      enabled: false
EOF

❸ Deploy the Talker API

The Talker API is a simple HTTP service that echoes back in the response whatever it gets in the request. We will use it in this guide as the sample service to be protected by Authorino.

kubectl apply -f https://raw.githubusercontent.com/kuadrant/authorino-examples/main/talker-api/talker-api-deploy.yaml

❹ Setup Envoy

The following bundle from the Authorino examples deploys the Envoy proxy and configuration to wire up the Talker API behind the reverse-proxy, with external authorization enabled with the Authorino instance.4

kubectl apply -f https://raw.githubusercontent.com/kuadrant/authorino-examples/main/envoy/envoy-notls-deploy.yaml

The command above creates an Ingress with host name talker-api.127.0.0.1.nip.io. If you are using a local Kubernetes cluster created with Kind, forward requests from your local port 8000 to the Envoy service running inside the cluster:

kubectl port-forward deployment/envoy 8000:8000 2>&1 >/dev/null &

❺ Create an AuthConfig

Create an Authorino AuthConfig custom resource declaring the auth rules to be enforced.

The AuthConfig below sets all Kubernetes service accounts as trusted users of the API, and relies on the Kubernetes RBAC to enforce authorization using Kubernetes SubjectAccessReview API for non-resource endpoints:

Kuadrant users – Remember to create an AuthPolicy instead of an AuthConfig. For more, see Kuadrant auth. 
kubectl apply -f -<<EOF
apiVersion: authorino.kuadrant.io/v1beta3
kind: AuthConfig
metadata:
  name: talker-api-protection
spec:
  hosts:
  - talker-api.127.0.0.1.nip.io
  - envoy.default.svc.cluster.local
  authentication:
    "service-accounts":
      kubernetesTokenReview:
        audiences: ["https://kubernetes.default.svc.cluster.local"]
  authorization:
    "k8s-rbac":
      kubernetesSubjectAccessReview:
        user:
          selector: auth.identity.user.username
EOF

Check out the spec for the Authorino Kubernetes SubjectAccessReview authorization feature, for resource attributes permission checks where SubjectAccessReviews issued by Authorino are modeled in terms of common attributes of operations on Kubernetes resources (namespace, API group, kind, name, subresource, verb).

❻ Create roles associated with endpoints of the API

Because the k8s-rbac policy defined in the AuthConfig in the previous step is for non-resource access review requests, the corresponding roles and role bindings have to be defined at cluster scope.

Create a talker-api-greeter role whose users and service accounts bound to this role can consume the non-resource endpoints POST /hello and POST /hi of the API:

kubectl apply -f -<<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: talker-api-greeter
rules:
- nonResourceURLs: ["/hello"]
  verbs: ["post"]
- nonResourceURLs: ["/hi"]
  verbs: ["post"]
EOF

Create a talker-api-speaker role whose users and service accounts bound to this role can consume the non-resource endpoints POST /say/* of the API:

kubectl apply -f -<<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: talker-api-speaker
rules:
- nonResourceURLs: ["/say/*"]
  verbs: ["post"]
EOF

❼ Create the ServiceAccounts and permissions to consume the API

Create service accounts api-consumer-1 and api-consumer-2:

kubectl apply -f -<<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  name: api-consumer-1
EOF
kubectl apply -f -<<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
  name: api-consumer-2
EOF

Bind both service accounts to the talker-api-greeter role:

kubectl apply -f -<<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: talker-api-greeter-rolebinding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: talker-api-greeter
subjects:
- kind: ServiceAccount
  name: api-consumer-1
  namespace: default
- kind: ServiceAccount
  name: api-consumer-2
  namespace: default
EOF

Bind service account api-consumer-1 to the talker-api-speaker role:

kubectl apply -f -<<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: talker-api-speaker-rolebinding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: talker-api-speaker
subjects:
- kind: ServiceAccount
  name: api-consumer-1
  namespace: default
EOF

❽ Consume the API

Run a pod that consumes one of the greeting endpoints of the API from inside the cluster, as service account api-consumer-1, bound to the talker-api-greeter and talker-api-speaker cluster roles in the Kubernetes RBAC:

kubectl run greeter --attach --rm --restart=Never -q --image=quay.io/kuadrant/authorino-examples:api-consumer --overrides='{
  "apiVersion": "v1",
  "spec": {
    "containers": [{
      "name": "api-consumer", "image": "quay.io/kuadrant/authorino-examples:api-consumer", "command": ["./run"],
      "args":["--endpoint=http://envoy.default.svc.cluster.local:8000/hi","--method=POST","--interval=0","--token-path=/var/run/secrets/tokens/api-token"],
      "volumeMounts": [{"mountPath": "/var/run/secrets/tokens","name": "access-token"}]
    }],
    "serviceAccountName": "api-consumer-1",
    "volumes": [{"name": "access-token","projected": {"sources": [{"serviceAccountToken": {"path": "api-token","expirationSeconds": 7200}}]}}]
  }
}' -- sh
# Sending...
# 200

Run a pod that sends a POST request to /say/blah from within the cluster, as service account api-consumer-1:

kubectl run speaker --attach --rm --restart=Never -q --image=quay.io/kuadrant/authorino-examples:api-consumer --overrides='{
  "apiVersion": "v1",
  "spec": {
    "containers": [{
      "name": "api-consumer", "image": "quay.io/kuadrant/authorino-examples:api-consumer", "command": ["./run"],
      "args":["--endpoint=http://envoy.default.svc.cluster.local:8000/say/blah","--method=POST","--interval=0","--token-path=/var/run/secrets/tokens/api-token"],
      "volumeMounts": [{"mountPath": "/var/run/secrets/tokens","name": "access-token"}]
    }],
    "serviceAccountName": "api-consumer-1",
    "volumes": [{"name": "access-token","projected": {"sources": [{"serviceAccountToken": {"path": "api-token","expirationSeconds": 7200}}]}}]
  }
}' -- sh
# Sending...
# 200

Run a pod that sends a POST request to /say/blah from within the cluster, as service account api-consumer-2, bound only to the talker-api-greeter cluster role in the Kubernetes RBAC:

kubectl run speaker --attach --rm --restart=Never -q --image=quay.io/kuadrant/authorino-examples:api-consumer --overrides='{
  "apiVersion": "v1",
  "spec": {
    "containers": [{
      "name": "api-consumer", "image": "quay.io/kuadrant/authorino-examples:api-consumer", "command": ["./run"],
      "args":["--endpoint=http://envoy.default.svc.cluster.local:8000/say/blah","--method=POST","--interval=0","--token-path=/var/run/secrets/tokens/api-token"],
      "volumeMounts": [{"mountPath": "/var/run/secrets/tokens","name": "access-token"}]
    }],
    "serviceAccountName": "api-consumer-2",
    "volumes": [{"name": "access-token","projected": {"sources": [{"serviceAccountToken": {"path": "api-token","expirationSeconds": 7200}}]}}]
  }
}' -- sh
# Sending...
# 403
Extra: consume the API as service account api-consumer-2 from outside the cluster

Obtain a short-lived access token for service account api-consumer-2, bound to the talker-api-greeter cluster role in the Kubernetes RBAC, using the Kubernetes TokenRequest API:

export ACCESS_TOKEN=$(echo '{ "apiVersion": "authentication.k8s.io/v1", "kind": "TokenRequest", "spec": { "expirationSeconds": 600 } }' | kubectl create --raw /api/v1/namespaces/default/serviceaccounts/api-consumer-2/token -f - | jq -r .status.token)

Consume the API as api-consumer-2 from outside the cluster:

curl -H "Authorization: Bearer $ACCESS_TOKEN" -X POST http://talker-api.127.0.0.1.nip.io:8000/hello -i
# HTTP/1.1 200 OK
curl -H "Authorization: Bearer $ACCESS_TOKEN" -X POST http://talker-api.127.0.0.1.nip.io:8000/say/something -i
# HTTP/1.1 403 Forbidden

Cleanup

If you have started a Kubernetes cluster locally with Kind to try this user guide, delete it by running:

kind delete cluster --name authorino-tutorial

Otherwise, delete the resources created in each step:

kubectl delete serviceaccount/api-consumer-1
kubectl delete serviceaccount/api-consumer-2
kubectl delete clusterrolebinding/talker-api-greeter-rolebinding
kubectl delete clusterrolebinding/talker-api-speaker-rolebinding
kubectl delete clusterrole/talker-api-greeter
kubectl delete clusterrole/talker-api-speaker
kubectl delete authconfig/talker-api-protection
kubectl delete -f https://raw.githubusercontent.com/kuadrant/authorino-examples/main/envoy/envoy-notls-deploy.yaml
kubectl delete -f https://raw.githubusercontent.com/kuadrant/authorino-examples/main/talker-api/talker-api-deploy.yaml
kubectl delete authorino/authorino

To uninstall the Authorino Operator and manifests (CRDs, RBAC, etc), run:

kubectl delete -f https://raw.githubusercontent.com/Kuadrant/authorino-operator/main/config/deploy/manifests.yaml

Footnotes

  1. In contrast to a dedicated sidecar of the protected service and other architectures. Check out Architecture > Topologies for all options. ↩

  2. namespaced reconciliation mode. See Cluster-wide vs. Namespaced instances. ↩

  3. For other variants and deployment options, check out Getting Started, as well as the Authorino CRD specification. ↩

  4. For details and instructions to setup Envoy manually, see Protect a service > Setup Envoy in the Getting Started page. If you are running your ingress gateway in Kubernetes and wants to avoid setting up and configuring your proxy manually, check out Kuadrant. ↩