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Issue Let’s Encrypt certificate using Azure DNS

This tutorial shows how to issue free SSL certificate from Let’s Encrypt via DNS challenge for domains using Azure DNS service.

This article has been tested with a GKE cluster.

$ kubectl version --short
Client Version: v1.8.8
Server Version: v1.8.8-gke.0

1. Setup Issuer

Go to your DNS Zone page:

a-record

You’ll need this Subscription id and Resource group later while creating issuer.

Go to Azure Active Directory -> App registrations and click on New Registration

new-registration new-registration2

You’ll need the Application (client) ID and Directory (tenant) ID later for creating issuer.

client-tenant

Now, create a new client-secret.

client-secret

Copy the password for this client-secret and create a kubernetes secret:

kubectl create secret generic azuredns-secret --from-literal=client-secret="[email protected]_m[4"

Now go to Subscriptions page and click on the corresponding subscription for your dns zone:

subscriptions

Click on Access control (IAM) and Add -> Add role assignment. If you see this as Add role assignment (disabled) then have your portal administrator perform this step, otherwise ignore this.

Your administrator needs to go to the same page and add you as Owner or User Access Administrator

user-access

Now that you have access to this, go to Subscriptions -> Access control (IAM) -> Add and you should be able to Add role assignment. Add DNS Zone Contributor to dns-challenge (the app registration you created before)

dns-zone-contributor

Now create this issuer by applying issuer.yaml

apiVersion: cert-manager.io/v1
kind: Issuer
metadata:
  name: letsencrypt-staging-dns
  namespace: default
spec:
  acme:
    server: https://acme-staging-v02.api.letsencrypt.org/directory
    email: [email protected]
    # Name of a secret used to store the ACME account private key
    privateKeySecretRef:
      name: example-issuer-account-key
    solvers:
      - dns01:
          azuredns:
            # Service principal clientId (also called appId)
            clientID: riu478u-486ij8-uiu487j-468rjg8
            # A secretKeyRef to a service principal ClientSecret (password)
            clientSecretSecretRef:
              name: azuredns-secret
              key: client-secret
            # Azure subscription Id
            subscriptionID: 45ji8t4-rgi4859-g845jg-9jjf9945r
            # Azure AD tenant Id
            tenantID: 348585ej-4358fdg8-f4588fg-45889fg
            # ResourceGroup name where dns zone is provisioned
            resourceGroupName: dev
            hostedZoneName: appscode.info

2. Create Ingress

We are going to use a nginx server as the backend. To deploy nginx server, run the following commands:

kubectl run nginx --image=nginx
kubectl expose deployment nginx --name=web --port=80 --target-port=80

Now, Create ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: test-ingress-deploy-k8s-azure-dns
  namespace: default
  annotations:
    kubernetes.io/ingress.class: voyager
    certmanager.k8s.io/issuer: "letsencrypt-staging-dns"
    certmanager.k8s.io/acme-challenge-type: dns01
spec:
  tls:
    - hosts:
        - kiteci-azure-dns.appscode.info
      secretName: kiteci-azure-dns-tls
  rules:
    - host: kiteci-azure-dns.appscode.info
      http:
        paths:
          - backend:
              service:
                name: web
                port:
                  number: 80
            path: /

Then take the EXTERNAL-IP from the corresponding service and add a A-record in Azure DNS:

kubectl get svc
NAME                                          TYPE           CLUSTER-IP     EXTERNAL-IP       PORT(S)                      AGE
voyager-test-ingress-deploy-k8s-azure-dns     LoadBalancer   10.7.254.246   35.192.150.216    443:31233/TCP,80:32271/TCP   26h

3. Create Certificate

Then create this certificate.yaml

apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
  name: kiteci-azure-dns
  namespace: default
spec:
  secretName: kiteci-azure-dns-tls
  issuerRef:
    name: letsencrypt-staging-dns
  dnsNames:
    - kiteci-azure-dns.appscode.info

Now, List the certificates and describe that certificate and wait until you see Certificate issued successfully when you describe the certificate.

kubectl get certificates.certmanager.k8s.io --all-namespaces

Then visit kiteci-azure-dns.appscode.info from browser and check the certificate that it was issued from let’s encrypt. (For let’s encrypt staging environment, you will see that the certificate was issued by Fake LE Intermediate X1.)