However the free certificates from Let’s Encrypt are only valid for 90 days and I have been notified to renew them already. I could run the cert-bot again to semi-automatically renew the certificates in my Kubernetes cluster, but there’s Cert Manager which claims to be able to fully automate the whole process. I have to give it a try.
The Cert Manager essentially is a bundle of a Kubernetes Operator + CRDs(Custom Resource Definition), I followed the installation steps and installed Cert Manager easily with default settings. I chose to install with plain manifests because I tried the Helm charts first but it had some issues with my FluxCD pipeline. The plain manifests include the Cert Manager operator, CRDs and relevant Kubernetes resources such as Namespace and Service Account.
To use the same CloudFlare DNS challenge I used with cert-bot, I created a secret containing my CF API token:
$ k create secret generic cloudflare-api-token -n cert-manager --from-literal=api-key=eQ9Ls6...
Note: it will take a while for the Cert Manager to self-signed certificate for itself and get ready for requests.
Then I created a ClusterIssuer using CloudFlare DNS challenge to verify domain authority:
$ cat <<EOF |k apply -f - apiVersion: cert-manager.io/v1 kind: ClusterIssuer metadata: name: letsencrypt-issuer spec: acme: email: <my email> server: https://acme-v02.api.letsencrypt.org/directory # this is the new CA chain preferredChain: "ISRG Root X1" # a secret name to save the private key privateKeySecretRef: name: letsencrypt-issuer solvers: - dns01: cloudflare: email: <my cloudflare email> # the secret to provide CloudFlare API Token apiTokenSecretRef: name: cloudflare-api-token key: api-key EOF
Then I checked if the ClusterIssuer is up:
$ k get clusterissuer NAME READY AGE letsencrypt-issuer True 1m
Almost done! The Cert Manager is now ready to manage certificates. I then created a Certificate resource to request and manage a new certificate:
$ cat <<EOF |k apply -f - apiVersion: cert-manager.io/v1 kind: Certificate metadata: name: wordpress-raynix # the cert will be in istio-system namespace to be used by istio namespace: istio-system spec: # the secret to hold this cert secretName: wordpress-raynix-cert duration: 2160h # 90d renewBefore: 360h # 15d subject: organizations: - raynix.info isCA: false privateKey: algorithm: RSA size: 2048 usages: - server auth - client auth # put all DNS names in the cert here dnsNames: - raynix.info # refer to the ClusterIssuer issuerRef: name: letsencrypt-issuer kind: ClusterIssuer EOF
Then it usually takes a minute or longer to actually see the secret in the newly created secret. The DNS challenge process is now run by the Cert Manager pod instead of the cert-bot.
As a last step, the new cert can be used in an Istio Gateway:
# this is the existing gateway apiVersion: networking.istio.io/v1beta1 kind: Gateway metadata: name: wordpress-gateway namespace: wordpress-raynix spec: selector: istio: ingressgateway servers: - hosts: - raynix.info port: name: https number: 443 protocol: HTTPS tls: # use the new cert in the new secret! credentialName: wordpress-raynix-cert mode: SIMPLE - hosts: - raynix.info port: name: http number: 80 protocol: HTTP tls: httpsRedirect: true
That’s it! Cert Manager claims that it can manage that cert and renew it accordingly, let’s see if that’s true 🙂