ACME webhook for DuckDNS (cert-manager-webhook-duckdns)

cert-manager-webhook-duckdns is an ACME webhook for cert-manager. It provides an ACME (read: Let's Encrypt) webhook for cert-manager, which allows to use a DNS-01 challenge with DuckDNS. This allows to provide Let's Encrypt certificates to Kubernetes for service protocols other than HTTP and furthermore to request wildcard certificates. Internally it uses the DuckDNS API to communicate with DuckDNS.

Quoting the ACME DNS-01 challenge:

This challenge asks you to prove that you control the DNS for your domain name by putting a specific value in a TXT record under that domain name. It is harder to configure than HTTP-01, but can work in scenarios that HTTP-01 can’t. It also allows you to issue wildcard certificates. After Let’s Encrypt gives your ACME client a token, your client will create a TXT record derived from that token and your account key, and put that record at _acme-challenge.<YOUR_DOMAIN>. Then Let’s Encrypt will query the DNS system for that record. If it finds a match, you can proceed to issue a certificate!

Building

Build the container image cert-manager-webhook-duckdns:latest:

make build

Image

Ready made images are hosted on Docker Hub (image tags). Use at your own risk:

joshuakraitberg/cert-manager-webhook-duckdns

Compatibility

This webhook has been tested with cert-manager v1.2.0 and Kubernetes v0.17.x on amd64. In theory it should work on other hardware platforms as well but no steps have been taken to verify this. Please drop me a note if you had success.

Install with helm

1. Install cert-manager with Helm:

    helm repo add jetstack https://charts.jetstack.io
    helm repo update
   
    helm install \
    cert-manager jetstack/cert-manager \
    --namespace cert-manager \
    --version v1.2.0 \
    --set 'extraArgs={--dns01-recursive-nameservers=8.8.8.8:53\,1.1.1.1:53}' \
    --create-namespace \
    --set installCRDs=true
   
    kubectl get pods --namespace cert-manager --watch
   

   Note: refer to Name servers in the official documentation according the extraArgs.

   Note: ensure that the custom CRDS of cert-manager match the major version of the cert-manager release by comparing the URL of the CRDS with the helm info of the charts app version:

        helm search repo jetstack
   

   Example output:

        NAME                    CHART VERSION   APP VERSION     DESCRIPTION
        jetstack/cert-manager	  v1.2.0       	  v1.2.0     	    A Helm chart for cert-manager
   

   Check the state and ensure that all pods are running fine (watch out for any issues regarding the cert-manager-webhook- pod and its volume mounts):

        kubectl describe pods -n cert-manager | less
   

2. Deploy this locally built webhook (add --dry-run to try it and --debug to inspect the rendered manifests; Set logLevel to 6 for verbose logs):

    helm install cert-manager-webhook-duckdns \
        --namespace cert-manager \
        --set duckdns.token='<token>' \
        --set clusterIssuer.production.create=true \
        --set clusterIssuer.staging.create=true \
        --set clusterIssuer.email=<email> \
        --set logLevel=2 \
        ./charts/cert-manager-webhook-duckdns
   

   Or you can use the helm repo provided here

    helm install cert-manager-webhook-duckdns \
        --namespace cert-manager \
        --set duckdns.token='<token>' \
        --set clusterIssuer.production.create=true \
        --set clusterIssuer.staging.create=true \
        --set clusterIssuer.email=<email> \
        --set logLevel=2 \
        joshuakraitberg.github.io/cert-manager-webhook-duckdns
   

   Check the logs

        kubectl get pods -n cert-manager --watch
        kubectl logs -n cert-manager cert-manager-webhook-duckdns-XYZ
   

3. Issue a Certificate for your $DOMAIN:

    cat << EOF | sed "s/example-com/$DOMAIN/" | kubectl apply -f -
    apiVersion: cert-manager.io/v1
    kind: Certificate
    metadata:
      name: example-com
      namespace: services
    spec:
      dnsNames:
      - 'example-com'
      issuerRef:
        name: cert-manager-webhook-duckdns-production
        kind: ClusterIssuer
      secretName: example-com-tls
    EOF
   

   Check the status of the Certificate:

    kubectl describe certificate $DOMAIN
   

   Display the details like the common name and subject alternative names:

    kubectl get secret $DOMAIN-tls -o yaml
   

4. Uninstall this webhook:

    helm uninstall cert-manager-webhook-duckdns --namespace cert-manager
    kubectl delete duckdns-credentials
   

5. Uninstalling cert-manager:

Refer to the official documentation.

Conformance test

Please note that the test is not a typical unit or integration test. Instead it invokes the web hook in a Kubernetes-like environment which asks the web hook to really call the DNS provider (.i.e. DuckDNS). It attempts to create an TXT entry like cert-manager-dns01-tests.example.com, verifies the presence of the entry via Google DNS. Finally it removes the entry by calling the cleanup method of web hook.

Note: Replace the string darwin in the URL below with an OS matching your system (e.g. linux).

As said above, the conformance test is run against the real DuckDNS API. Therefore you must have a DuckDNS account, a domain and an API token.

cp testdata/duckdns/api-key.yml.sample testdata/duckdns/api-key.yml
echo -n $YOUR_DUCKDNS_TOKEN | base64 | pbcopy # or xclip
$EDITOR testdata/duckdns/api-key.yml
./scripts/fetch-test-binaries.sh
TEST_ZONE_NAME=example.com. DNS_NAME=example.com go test -v .