ACME webhook for variomedia (cert-manager-webhook-variomedia)

cert-manager-webhook-variomedia 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 variomedia. 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 [variomedia LiveDNS API] to communicate with variomedia.

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-variomedia:latest:

make build

Image

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

jheyduk/cert-manager-webhook-variomedia

Release History

Refer to the ChangeLog file.

Compatibility

This webhook has been tested with cert-manager v0.13.1 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.

Testing with Minikube

1. Build this webhook in Minikube:

    minikube start --memory=4G --more-options
    eval $(minikube docker-env)
    make build
    docker images | grep webhook
   

2. Install cert-manager with Helm:

    kubectl create namespace cert-manager
    kubectl apply --validate=false -f https://raw.githubusercontent.com/jetstack/cert-manager/v0.13.1/deploy/manifests/00-crds.yaml
   
    helm repo add jetstack https://charts.jetstack.io
    helm install cert-manager --namespace cert-manager \
        --set 'extraArgs={--dns01-recursive-nameservers=8.8.8.8:53\,1.1.1.1:53}' \
        jetstack/cert-manager
   
    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   v0.13.1         v0.13.1         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
   

3. Create the secret to keep the variomedia API key in the default namespace, where later on the Issuer and the Certificate are created:

    kubectl create secret generic variomedia-credentials \
        --from-literal=api-token='<variomedia-API-KEY>'
   

   Note: See RBAC Authorization:

   A Role can only be used to grant access to resources within a single namespace.

   As far as I understand cert-manager, the Secret must reside in the same namespace as the Issuer and Certificate resource.

4. Grant permission for the service-account to access the secret holding the variomedia API key:

    kubectl apply -f rbac.yaml
   

5. 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-variomedia \
        --namespace cert-manager \
        --set image.repository=cert-manager-webhook-variomedia \
        --set image.tag=latest \
        --set logLevel=2 \
        ./deploy/cert-manager-webhook-variomedia
   

   To deploy using the image from Docker Hub (for example using the v0.1.1 tag):

    helm install cert-manager-webhook-variomedia \
        --namespace cert-manager \
        --set image.tag=v0.1.1 \
        --set logLevel=2 \
        ./deploy/cert-manager-webhook-variomedia
   

   Check the logs

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

6. Create a staging issuer (email addresses with the suffix example.com are forbidden):

    cat << EOF | sed "s/[email protected]/$email/" | kubectl apply -f -
    apiVersion: cert-manager.io/v1alpha2
    kind: Issuer
    metadata:
      name: letsencrypt-staging
      namespace: default
    spec:
      acme:
        # The ACME server URL
        server: https://acme-staging-v02.api.letsencrypt.org/directory
        # Email address used for ACME registration
        email: [email protected]
        # Name of a secret used to store the ACME account private key
        privateKeySecretRef:
          name: letsencrypt-staging
        solvers:
        - dns01:
            webhook:
              groupName: acme.jheyduk.dev
              solverName: variomedia
              config:
                apiKeySecretRef:
                  key: api-token
                  name: variomedia-credentials
    EOF
   

   Check status of the Issuer:

    kubectl describe issuer letsencrypt-staging
   

   Note: The production Issuer is similar.

7. Issue a Certificate for your $DOMAIN:

    cat << EOF | sed "s/example-com/$DOMAIN/" | kubectl apply -f -
    apiVersion: cert-manager.io/v1alpha2
    kind: Certificate
    metadata:
      name: example-com
    spec:
      dnsNames:
      - example-com
      issuerRef:
        name: letsencrypt-staging
      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
   

8. Issue a wildcard Certificate for your $DOMAIN:

    cat << EOF | sed "s/example-com/$DOMAIN/" | kubectl apply -f -
    apiVersion: cert-manager.io/v1alpha2
    kind: Certificate
    metadata:
      name: wildcard-example-com
    spec:
      dnsNames:
      - '*.example-com'
      issuerRef:
        name: letsencrypt-staging
      secretName: wildcard-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 wildcard-$DOMAIN-tls -o yaml
   

9. Uninstall this webhook:

   helm uninstall cert-manager-webhook-variomedia --namespace cert-manager
   kubectl delete -f rbac.yaml
   kubectl delete variomedia-credentials
   

10. Uninstalling cert-manager: This is out of scope here. Refer to the official documentation.

Development

Note: If some tool (IDE or build process) fails resolving a dependency, it may be the cause that a indirect dependency uses bzr for versioning. In such a case it may help to put the bzr binary into $PATH or $GOPATH/bin.

Release process

• Code changes result in a new image version and Git tag
• Helm chart changes result in a new chart version
• All other changes are pushed to master
• All versions are to be documented in ChangeLog

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. variomedia). 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 variomedia API. Therefore you must have a variomedia account, a domain and an API key.

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