ExternalDNS and Cert Manager are two well known integrations within the Kubernetes ecosystem that can be used in conjunction to automate the creation of TLS certificates.

Before you begin

Follow the Get started guide to install Gloo Gateway v2, set up a gateway resource, and deploy the httpbin sample app.

Set up ExternalDNS

ExternalDNS is used to dynamically set up and control DNS records for discovered gateway and HTTP resources. When you create a gateway or HTTP resource, and you define a hostname, External DNS uses the external address that is assigned to the gateway’s load balancer service that serves this hostname, and uses this information to create a DNS record in the DNS provider that you configured.

You can later use Cert Manager to create TLS certificates for this hostname so that you can serve HTTPS traffic on your gateway.

  1. Create an HTTP route resource to expose httpbin on your domain. Replace <my-domain.com> with your domain. Note that you must own the domain to enable ExternalDNS to create DNS records on your behalf.

      kubectl apply -f- <<EOF
    apiVersion: gateway.networking.k8s.io/v1beta1
    kind: HTTPRoute
    metadata:
      name: httpbin
      namespace: httpbin
      labels:
        example: httpbin-route
    spec:
      parentRefs:
        - name: http
          namespace: gloo-system
      hostnames:
        - "<my-domain.com>"
      rules:
        - backendRefs:
            - name: httpbin
              port: 8000
    EOF
      
  2. Deploy the ExternalDNS components. The following example configures ExternalDNS to monitor gateway and HTTP route resources to determine the list of DNS records that must be created or changed. DNS records are set up in DigitalOcean. To find the ExternalDNS configuration for your DNS provider, see the Kubernetes documentation.

      cat <<EOF | kubectl apply -f -
    apiVersion: v1
    kind: ServiceAccount
    metadata:
      name: external-dns
      namespace: default
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRole
    metadata:
      name: external-dns
    rules:
    - apiGroups: [""]
      resources: ["namespaces"]
      verbs: ["get","watch","list"]
    - apiGroups: ["gateway.networking.k8s.io"]
      resources: ["gateways","httproutes","grpcroutes","tlsroutes","tcproutes","udproutes"] 
      verbs: ["get","watch","list"]
    ---
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: external-dns
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: external-dns
    subjects:
    - kind: ServiceAccount
      name: external-dns
      namespace: default
    ---
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      name: external-dns
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: external-dns
      strategy:
        type: Recreate
      template:
        metadata:
          labels:
            app: external-dns
        spec:
          serviceAccountName: external-dns
          containers:
          - name: external-dns
            image: registry.k8s.io/external-dns/external-dns:v0.13.5
            args:
            - --source=gateway-httproute
            - --provider=digitalocean
            - --log-level=debug
            env:
            - name: DO_TOKEN
              value: "<my-token>"
    EOF
      
  3. Wait for the DNS entry to get created. Note that depending on the DNS provider that you use, this process can take some time to complete. To verify that the DNS record is created, use the dig command as shown in the following example.

      dig <my-domain.com>
      

    Example output for a successfully created DNS record:

      ;; ANSWER SECTION:
    <my-domain.com>	300	IN	A	164.90.241.80
      

Set up Cert Manager

Cert Manager is a Kubernetes controller that helps you automate the process of obtaining and renewing certificates from various PKI providers, such as AWS Private CA, Gloo Cloud CA, or Vault. In this example, you learn how to install Cert Manager by using Helm and how to configure it to obtain TLS certificates for your domain from Let’s Encrypt.

  1. Install Cert Manager.

      helm upgrade --install cert-manager jetstack/cert-manager --namespace cert-manager --create-namespace \
      --set "extraArgs={--feature-gates=ExperimentalGatewayAPISupport=true}" --set installCRDs=true
      
  2. Create an issuer resource that represents the Certificate Authority (CA) that you want to use to issue the TLS certificates for your domain. In this example, you configure Cert Manager to obtain a Let’s Encrypt certificate by using the ACME protocol. To automate domain validation and certificate issuance, you use the http01 challenge. The http01 challenge is designed to prove that you have control over your domain by requiring you to store a challenge token in your cluster so that Let’s Encrypt can validate it. For more information about this challenge, see the Let’s Encrypt documentation.

      kubectl apply -f- <<EOF
    apiVersion: cert-manager.io/v1
    kind: Issuer
    metadata:
      name: letsencrypt-http
      namespace: gloo-system
    spec:
      acme:
        email: hello@world.com
        #You can switch to live URL if you are brave
        #server: https://acme-v02.api.letsencrypt.org/directory
        server: https://acme-staging-v02.api.letsencrypt.org/directory
        privateKeySecretRef:
          name: letsencrypt-http-issuer-account-key
        solvers:
          - http01:
              gatewayHTTPRoute:
                parentRefs:
                  - name: http
                    namespace: gloo-system
                    kind: Gateway
    EOF
      
  3. Verify that your TLS certificates are created successfully. Note that depending on the CA that you use, this process might take a while to complete.

      kubectl get issuer letsencrypt-http -n gloo-system
      

    Example output for successfully issued TLS certificates:

       Status:
     Acme:
     Conditions:
         Last Transition Time:  2023-11-09T16:03:58Z
         Message:               The ACME account was registered with the ACME server
         Observed Generation:   1
         Reason:                ACMEAccountRegistered
         Status:                True
         Type:                  Ready
      
  4. Verify that the TLS certificate was added to the secret that you configured in the Cert Manager issuer resource.

      kubectl get secret letsencrypt-http-issuer-account-key -n gloo-system -o yaml
      

Configure an HTTPS listener on your gateway

  1. Add an HTTPS listener to the gateway that you set up as part of the Get started guide. Replace <my-domain.com> with your domain.

      kubectl apply -f- <<EOF
    apiVersion: gateway.networking.k8s.io/v1
    kind: Gateway
    metadata:
      name: http
      annotations:
        cert-manager.io/issuer: letsencrypt-http
      namespace: gloo-system
    spec:
      gatewayClassName: gloo-gateway
      listeners:
      - allowedRoutes:
          namespaces:
            from: All
        name: http
        port: 80
        protocol: HTTP
      - allowedRoutes:
          namespaces:
            from: All
        hostname: <my-hostname.com>
        name: https
        port: 443
        protocol: HTTPS
        tls:
          mode: Terminate
          certificateRefs:
            - name: letsencrypt-http-issuer-account-key
              kind: Secret
    EOF
      
  2. Verify that the gateway is configured successfully. You can also review the external address that is assigned to the gateway.

      kubectl get gateway http -n gloo-system
      

    Example output for an AWS EKS cluster:

      NAME   CLASS          ADDRESS                                                                  PROGRAMMED   AGE
    http   gloo-gateway   a3a6c06e2f4154185bf3f8af46abf22e-139567718.us-east-2.elb.amazonaws.com   True         93s
      

Test your HTTPS listener

With the TLS certificate in place, you can now test your HTTPS listener.

Send a curl request to the httpbin app on the domain that you configured.

  curl -vik https://<my-domain.com>/status/200
  

Example output:

  *   Trying 164.90.241.80:443...
* Connected to <my-domain.com> (164.90.241.80) port 443 (#0)
* ALPN: offers h2,http/1.1
* (304) (OUT), TLS handshake, Client hello (1):
* (304) (IN), TLS handshake, Server hello (2):
* (304) (IN), TLS handshake, Unknown (8):
* (304) (IN), TLS handshake, Certificate (11):
* (304) (IN), TLS handshake, CERT verify (15):
* (304) (IN), TLS handshake, Finished (20):
* (304) (OUT), TLS handshake, Finished (20):
* SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256
* ALPN: server accepted h2
* Server certificate:
*  subject: CN=<my-domain.com>
*  start date: Nov  9 15:32:59 2023 GMT
*  expire date: Feb  7 15:32:58 2024 GMT
*  issuer: C=US; O=Let's Encrypt; CN=R3
*  SSL certificate verify ok.
* using HTTP/2
* h2h3 [:method: GET]
* h2h3 [:path: /status/200]
* h2h3 [:scheme: https]
* h2h3 [:authority: <my-domain.com>]
* h2h3 [user-agent: curl/7.88.1]
* h2h3 [accept: */*]
* Using Stream ID: 1 (easy handle 0x12c812800)
> GET /status/200 HTTP/2
> Host: <my-domain.com>
> user-agent: curl/7.88.1
> accept: */*
>
< HTTP/2 200
HTTP/2 200
< access-control-allow-credentials: true
access-control-allow-credentials: true
< access-control-allow-origin: *
access-control-allow-origin: *
< date: Thu, 09 Nov 2023 17:28:17 GMT
date: Thu, 09 Nov 2023 17:28:17 GMT
< content-length: 0
content-length: 0
< x-envoy-upstream-service-time: 2
x-envoy-upstream-service-time: 2
< server: envoy
server: envoy

<
* Connection #0 to host <my-domain.com> left intact