Deploying cert-manager

We suggest using cert-manager for provisioning the certificates for the webhook server. Other solutions should also work as long as they put the certificates in the desired location.

You can follow the cert-manager documentation to install it.

cert-manager also has a component called CA Injector, which is responsible for injecting the CA bundle into the MutatingWebhookConfiguration / ValidatingWebhookConfiguration.

To accomplish that, you need to use an annotation with key cert-manager.io/inject-ca-from in the MutatingWebhookConfiguration / ValidatingWebhookConfiguration objects. The value of the annotation should point to an existing certificate request instance in the format of <certificate-namespace>/<certificate-name>.

This is the kustomize patch we used for annotating the MutatingWebhookConfiguration / ValidatingWebhookConfiguration objects.

# This patch add annotation to admission webhook config and
# CERTIFICATE_NAMESPACE and CERTIFICATE_NAME will be substituted by kustomize
apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
  labels:
    app.kubernetes.io/name: project
    app.kubernetes.io/managed-by: kustomize
  name: mutating-webhook-configuration
  annotations:
    cert-manager.io/inject-ca-from: CERTIFICATE_NAMESPACE/CERTIFICATE_NAME
---
apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingWebhookConfiguration
metadata:
  labels:
    app.kubernetes.io/name: validatingwebhookconfiguration
    app.kubernetes.io/instance: validating-webhook-configuration
    app.kubernetes.io/component: webhook
    app.kubernetes.io/created-by: project
    app.kubernetes.io/part-of: project
    app.kubernetes.io/managed-by: kustomize
  name: validating-webhook-configuration
  annotations:
    cert-manager.io/inject-ca-from: CERTIFICATE_NAMESPACE/CERTIFICATE_NAME