Expose OAuth Endpoints from Kubernetes

The Configure Deployments using Helm tutorial shows how to run admin and runtime workloads in a Kubernetes cluster, deploy configuration and locate OAuth endpoints. For convenience, it uses HTTP endpoints on localhost. In the Configure Deployed Environments tutorial you can learn about the general approach to configure HTTPS and external URLs. This tutorial explains Kubernetes specific behaviors and summarizes how to use an API gateway in Kubernetes to provide external HTTPS URLs.

Expose Public Endpoints

To expose public endpoints, design domain-based URLs for the admin and runtime workloads.

Deploy an API Gateway

There are many cloud native API gateways that can run in Kubernetes. Usually, an API gateway uses a service type of LoadBalancer and the Curity workloads use a service type of ClusterIP. The API gateway deployment typically includes a Kubernetes controller that watches particular Kubernetes resources and updates the underlying gateway product when required. The following subsections provide example deployments using NGINX and Kong. Use an equivalent approach for other API gateways.

helm install nginx oci://ghcr.io/nginxinc/charts/nginx-gateway-fabric \
  --namespace apigateway \
  --create-namespace \
  --set nginxGateway.replicaCount=2

helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm repo update
helm upgrade --install ingress-nginx ingress-nginx/ingress-nginx \
    --namespace apigateway \
    --create-namespace \
    --set controller.replicaCount=2

View the API Gateway Service

Run a command of the following form to view the main resources deployed to the API gateway's namespace:

kubectl get all -n apigateway

A typical deployment consists of one or more API gateway pods and a service with type LoadBalancer. The service gets an external IP address that may initially remain in a Pending state.

NAME                            READY   STATUS    RESTARTS        AGE
pod/kong-kong-5b874fd59-97dqk   2/2     Running   2               3m48s
pod/kong-kong-5b874fd59-c2dxh   2/2     Running   2 (3m46s ago)   3m48s

NAME                                   TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)                         AGE
service/kong-kong-proxy                LoadBalancer   10.96.159.208   <pending>     443:31025/TCP                   3m48s

NAME                        READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/kong-kong   2/2     2            2           3m48s

NAME                                  DESIRED   CURRENT   READY   AGE
replicaset.apps/kong-kong-5b874fd59   2         2         2       3m48s

Enable Network Connectivity

Usually network connectivity starts with the creation of DNS domains and external IP addresses. OAuth clients can then use domain-based URLs to call OAuth endpoints inside the Kubernetes cluster.

A Kubernetes deployment requires some additional components to route the client requests to the workloads in a cluster.

• A load balancer uses one or more external IP addresses to receive traffic for one or more host names.
• The load balancer can route traffic to the API gateway that terminates the requests.
• The API gateway can preprocess requests, then forward them to OAuth endpoints.

There are many possible ways to enable network connectivity to an API gateway. Usually, networking infrastructure spins up a load balancer when you deploy a service type of LoadBalancer to the cluster. Real world deployments often use sophisticated load balancers that can route to multiple regions or availability zones.

Create Ingress Routes

Once network connectivity is in place, the ingress configuration is identical in any deployed environment, whether in the cloud, on premise or on your local machine. Instruct the API gateway to route to a Kubernetes Service with the following steps:

• Create a Kubernetes HttpRoute or Ingress resource in the namespace of the Kubernetes Service.
• Use the external hostname to match incoming requests.
• Use a reference to match the HttpRoute or Ingress to the API gateway.

Save YAML resources to a file and apply them with the kubectl tool to expose external endpoints from the cluster. Some gateways may require you to use custom resource definitions to express ingress routes, but should follow the same concepts.

Enable Ingress using the Helm Chart

As a default option, enable ingress with the Helm chart, which currently only supports the use of Kubernetes Ingress resources. To enable ingress, express settings like those shown here to a Helm values.yaml file, to expose runtime and admin endpoints from the cluster.

ingress:
  ingressClassName:
  runtime:
    enabled: true
    host: login.testcluster.example
  admin:
    enabled: true
    host: admin.testcluster.example

networkpolicy:
  enabled: true
  apigatewayNamespace: 'apigateway'

Create Ingress Routes Manually

If the Helm chart's ingress support does not meet your needs, create the API gateway resources manually, to expose OAuth and admin endpoints from the cluster.

kind: HTTPRoute
apiVersion: gateway.networking.k8s.io/v1
metadata:
  name: idsvr-admin-route
  namespace: curity
spec:
  parentRefs:
  - name: kong-gateway
    namespace: apigateway
  hostnames:
  - admin.testcluster.example
  rules:
  - matches:
    - path:
        value: /
    backendRefs:
    - name: curity-idsvr-admin-svc
      kind: Service
      port: 6749
---
kind: HTTPRoute
apiVersion: gateway.networking.k8s.io/v1
metadata:
  name: idsvr-runtime-route
  namespace: curity
spec:
  parentRefs:
  - name: kong-gateway
    namespace: apigateway
  hostnames:
  - login.testcluster.example
  rules:
  - matches:
    - path:
        value: /
    backendRefs:
    - name: curity-idsvr-runtime-svc
      kind: Service
      port: 8443
---
kind: HTTPRoute
apiVersion: gateway.networking.k8s.io/v1
metadata:
  name: idsvr-oauthagent-route
  namespace: applications
spec:
  parentRefs:
  - name: kong-gateway
    namespace: apigateway
  hostnames:
  - api.demoapp.example
  rules:
  - matches:
    - path:
        value: /oauthagent/example
    backendRefs:
    - name: curity-idsvr-runtime-svc
      kind: Service
      port: 8443

Call OAuth Endpoints

Once you have ingress working, teams can administer the Curity configuration using the Admin UI and remote OAuth clients can call OAuth endpoints.

curl -i http://admin.testcluster.example/admin
curl -i http://login.testcluster.example/oauth/v2/oauth-anonymous/.well-known/openid-configuration

Enable HTTPS URLs

Next, you typically need to upgrade external endpoints to use HTTPS and there are multiple ways to enable this. Cloud platforms may enable you to terminate TLS at the load balancer and apply service annotations to the API gateway's service to use managed certificates that the cloud platform issues. The following format of annotation can be used with AWS load balancers:

service:
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-ssl-cert: arn:aws:acm:us-west-2:xxxxx:certificate/xxxxxxx

Cloud Native Certificate Automation

An alternative option that works in any deployed environment is to pass TCP level traffic through the load balancer and terminate most TLS traffic at the API gateway. When external TLS traffic terminates inside the cluster you must use a cloud native solution to provision external certificates.

The popular cert-manager tool can integrate with paid or free certificate providers using issuer resources. The following example uses a cert-manager ClusterIssuer to get certificates for AWS Route 53 domains from the free Let's Encrypt provider. Other options are possible, like a self signed issuer during rehearsal of deployments on a local computer.

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: api-gateway-issuer
spec:
  acme:
    server: https://acme-v02.api.letsencrypt.org/directory
    email: admin@testcluster.example
    privateKeySecretRef:
      name: letsencrypt
    solvers:
      - dns01:
          route53: {}

The cert-manager workloads can integrate with the chosen certificate issuer, which must prove that you own TLS hostnames. The issuer then returns a certificate to cert-manager, which saves the certificate and its underlying key to a Kubernetes secret. You can instruct cert-manager to get HTTPS certificates in various ways.

apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: api-gateway-certificate
spec:
  secretName: testcluster-example-tls
  isCA: false
  duration: 2160h
  renewBefore: 1440h
  privateKey:
    algorithm: ECDSA
    size: 256
  dnsNames:
    - admin.testcluster.example
    - login.testcluster.example
    - api.demoapp.example
  issuerRef:
    name: api-gateway-issuer
    kind: ClusterIssuer
    group: cert-manager.io

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: kong-gateway
spec:
  gatewayClassName: kong
  listeners:
  - name: testcluster.example
    port: 443
    protocol: HTTPS
    hostname: '*.testcluster.example'
    allowedRoutes:
      namespaces:
        from: 'All'
    tls:
      mode: Terminate
      certificateRefs:
      - name: testcluster-example-tls
  listeners:
  - name: demoapp.example
    port: 443
    protocol: HTTPS
    hostname: '*.demoapp.example'
    allowedRoutes:
      namespaces:
        from: 'All'
    tls:
      mode: Terminate
      certificateRefs:
      - name: testcluster-example-tls

Deployment Example

The GitHub link at the top of this page provides some example Kubernetes deployment resources for a local computer. The ingress tutorial shows how to expose HTTPS OAuth domain based URLs for the admin and runtime workloads, for both the Curity Identity Server and the Curity Token Handler:

• A local load balancer provider sets an external IP address for the API gateway.
• The local computer acts as a DNS service to enable the use of domain-based URLs.
• The OpenSSL tool creates a development root certificate authority.
• The cert-manager tool uses the root certificate authority to issue API gateway certificates.

For other Kubernetes environments use similar techniques with a real load balancer and real certificate authority.

Conclusion

In Kubernetes, use an API gateway to expose both APIs and OAuth endpoints to clients. The API gateway uses a Kubernetes Service of type LoadBalancer and external networking infrastructure enables connectivity to the cluster from the outside world. Once clients have working OAuth endpoints, explore the following common next steps for your Curity product.

• For the Curity Identity Server, take control over identity data for clustered deployments and integrate your preferred Kubernetes Data Storage.
• For the Curity Token Handler, integrate Kubernetes API Gateway Plugins to finalize the endpoints for Single Page Applications.

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