➕ Add CA injector content

slides/k8s/cainjector.md

@@ -0,0 +1,60 @@
+## CA injector - overview
+
+- The Kubernetes API server can invoke various webhooks:
+
+  - conversion webhooks (registered in CustomResourceDefinitions)
+
+  - mutation webhooks (registered in MutatingWebhookConfigurations)
+
+  - validation webhooks (registered in ValidatingWebhookConfiguration)
+
+- These webhooks must be served over TLS
+
+- These webhooks must use valid TLS certificates
+
+---
+
+## Webhook certificates
+
+- Option 1: certificate issued by a global CA
+
+  - doesn't work with internal services
+    <br/>
+    (their CN must be `<servicename>.<namespace>.svc`)
+
+- Option 2: certificate issued by private CA + CA certificate in system store
+
+  - requires access to API server certificates tore
+
+  - generally not doable on managed Kubernetes clusters
+
+- Option 3: certificate issued by private CA + CA certificate in `caBundle`
+
+  - pass the CA certificate in `caBundle` field
+    <br/>
+    (in CRD or webhook manifests)
+
+  - can be managed automatically by cert-manager
+
+---
+
+## CA injector - details
+
+- Add annotation to *injectable* resource
+  (CustomResouceDefinition, MutatingWebhookConfiguration, ValidatingWebhookConfiguration)
+
+- Annotation refers to the thing holding the certificate:
+
+  - `cert-manager.io/inject-ca-from: <namespace>/<certificate>`
+
+  - `cert-manager.io/inject-ca-from-secret: <namespace>/<secret>`
+
+  - `cert-manager.io/inject-apiserver-ca: true` (use API server CA)
+
+- When injecting from a Secret, the Secret must have a special annotation:
+
+  `cert-manager.io/allow-direct-injection: "true"`
+
+- See [cert-manager documentation][docs] for details
+
+[docs]: https://cert-manager.io/docs/concepts/ca-injector/

slides/kube-adv.yml

@@ -62,6 +62,7 @@ content:
   - k8s/ingress-tls.md
   - k8s/ingress-advanced.md
   - k8s/cert-manager.md
+  - k8s/cainjector.md
   - k8s/eck.md
 - #7
   - k8s/admission.md

slides/kube-selfpaced.yml

@@ -84,6 +84,7 @@ content:
   - k8s/ingress-advanced.md
   - k8s/ingress-tls.md
   - k8s/cert-manager.md
+  - k8s/cainjector.md
   - k8s/kustomize.md
   - k8s/helm-intro.md
   - k8s/helm-chart-format.md