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Using annotated Gateway API Gateway and/or HTTPRoutes as Source

This tutorial describes how to use annotated Gateway API resources as source for Certificate.

Install Istio on your cluster

Follow the Istio Kubernetes Gateway API to install the Gateway API and to install Istio.

These are the typical commands for the Istio installation with the Kubernetes Gateway API:

export KUEBCONFIG=...
curl -L https://istio.io/downloadIstio | sh -
kubectl get crd gateways.gateway.networking.k8s.io &> /dev/null || \
  { kubectl kustomize "github.com/kubernetes-sigs/gateway-api/config/crd?ref=v1.0.0" | kubectl apply -f -; }
istioctl install --set profile=minimal -y
kubectl label namespace default istio-injection=enabled

Verify that Gateway Source works

Install a sample service

With automatic sidecar injection:

$ kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.20/samples/httpbin/httpbin.yaml

Note: The sample service is not used in the following steps. It is deployed for illustration purposes only. To use it with certificates, you have to add an HTTPS port for it.

Using a Gateway as a source

Deploy the Gateway API configuration including a single exposed route (i.e., /get):

kubectl create namespace istio-ingress
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway
  namespace: istio-ingress
  annotations:
    #cert.gardener.cloud/dnsnames: "*.example.com" # alternative if you want to control the dns names explicitly.
    cert.gardener.cloud/purpose: managed
spec:
  gatewayClassName: istio
  listeners:
  - name: default
    hostname: "*.example.com"  # this is used by cert-controller-manager to extract DNS names
    port: 443
    protocol: HTTPS
    allowedRoutes:
      namespaces:
        from: All
    tls:                       # important: tls section must be defined with exactly one certificateRefs item
      certificateRefs:
        - name: foo-example-com
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: http
  namespace: default
spec:
  parentRefs:
  - name: gateway
    namespace: istio-ingress
  hostnames: ["httpbin.example.com"]  # this is used by cert-controller-manager to extract DNS names too
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /get
    backendRefs:
    - name: httpbin
      port: 8000
EOF

You should now see a created Certificate resource similar to:

$ kubectl -n istio-ingress get cert -oyaml
apiVersion: v1
items:
- apiVersion: cert.gardener.cloud/v1alpha1
  kind: Certificate
  metadata:
    generateName: gateway-gateway-
    name: gateway-gateway-kdw6h
    namespace: istio-ingress
    ownerReferences:
    - apiVersion: gateway.networking.k8s.io/v1
      blockOwnerDeletion: true
      controller: true
      kind: Gateway
      name: gateway
  spec:
    commonName: '*.example.com'
    secretName: foo-example-com
  status:
    ...
kind: List
metadata:
  resourceVersion: ""

Using a HTTPRoute as a source

If the Gateway resource is annotated with cert.gardener.cloud/purpose: managed, hostnames from all referencing HTTPRoute resources are automatically extracted. These resources don’t need an additional annotation.

Deploy the Gateway API configuration including a single exposed route (i.e., /get):

kubectl create namespace istio-ingress
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: gateway
  namespace: istio-ingress
  annotations:
    cert.gardener.cloud/purpose: managed
spec:
  gatewayClassName: istio
  listeners:
  - name: default
    hostname: null  # not set 
    port: 443
    protocol: HTTPS
    allowedRoutes:
      namespaces:
        from: All
    tls:                            # important: tls section must be defined with exactly one certificateRefs item
      certificateRefs:
        - name: foo-example-com
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: http
  namespace: default
spec:
  parentRefs:
  - name: gateway
    namespace: istio-ingress
  hostnames: ["httpbin.example.com"]  # this is used by dns-controller-manager to extract DNS names too
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /get
    backendRefs:
    - name: httpbin
      port: 8000
EOF

This should show a similar Certificate resource as above.