[FEATURE] Add cert-manager Support on Kubernetes Integration

[polarstack]

What's needed and why ?
Hi All

• As a BunkerWeb User having cert-manager in the Kubernetes Integration would make my experience even more cloud native.
• As a Homelab User on a Kubernetes Cluster I would like to configure cert-manager with the DNS-01 challenge instead of HTTP-01 to be able, to close all unnecessary ports and apply GeoBlocking (Let's Encrypt does not support IP sets to apply/whitelist on a Firewall).
• As a potential Business Customer I can store my Certificates in Hashicorp Vault or Venafi and apply them to my Ingress as they are supported by cert-manager.

I see the certbot-dns-* examples which could cover at least the second use case (e.g. ../examples/certbot-dns-cloudflare/docker-compose.yml), but as far as I understands it needs you to mount the "certs" Volume to bunkerweb, scheduler and a custom certbot container with the corresponding config. But not sure how I would implement that on Kubernetes. Using Kubernetes Secrets and Ingress Annotations would make it more natively on that Integration.

Implementations ideas (optional)
The Documentation for cert-manager is here: https://cert-manager.io/docs/
But the Installation and Configuration of cert-manager can be out of scope

cert-manager stores the key and crt in a Kubernetes Secret:

# k3s kubectl describe secrets/dummy-secret  -n dummy-namespace
Name:         dummy-secret-tls-0
Namespace:    dummy-namespace
Labels:       controller.cert-manager.io/fao=true
Annotations:  cert-manager.io/alt-names: myapp.example.com
              cert-manager.io/certificate-name: dummy-secret-tls-0
              cert-manager.io/common-name: myapp.example.com
              cert-manager.io/issuer-group: cert-manager.io
              cert-manager.io/issuer-kind: ClusterIssuer
              cert-manager.io/issuer-name: my-issuer-example

Type:  kubernetes.io/tls

Data
====
tls.key:  xxxx bytes
tls.crt:  yyyy bytes

On the Ingress the mapping happens in the annotations section:

Annotations:                   cert-manager.io/cluster-issuer: my-issuer-example
                               cert-manager.io/private-key-rotation-policy: Always

Not a specialist as I'm still learning, but I guess the Ingress Annotation triggers cert-manager which then stores the crt/key as a secret. Finally the ingress controller (e.g. Traefik) picks it up and deploys/configures the TLS termination. Maybe it's also triggered by the Ingress Controller itself. See for example the official Kubernetes NGinx Ingress Chart: https://github.com/kubernetes/ingress-nginx/blob/afd1311f8529c21fdf6621bf683bec814e698f1d/charts/ingress-nginx/templates/admission-webhooks/cert-manager.yaml

As one can have multiple issuer, I would suggest to leave that as a matter of cert-manager and define the secret only:

annotations:
   bunkerweb.io/myapp.example.com_CLUSTER_ISSUER_CERTIFICATE: dummy-secret-tls-0

Finally the BunkerWeb Scheduler(?) would pick up the secret and store it in /certs/ like it does for example on http, server-http, modsec etc. with the ConfigMap Feature.

Hopefully I was able to explain the need simply, otherwise please let me know if I should elaborate. If you think this is an edge case and doesn't map your Roadmap, don't worry about it and close the issue :-)

[fl0ppy-d1sk]

Hello @polarstack,

That's an interesting idea. IMO it's even a must have.

Looks like we should parse the tls part of the ingress resource but we need to dig deeper.

[fl0ppy-d1sk]

Hello @polarstack,

Quick update : we now support tls section of Ingress in 1.5.5. Don't hesitate to test it by yourself.

Keeping this issue open because we still need to document (and test) the cert-manager integration.