Inject Sidecar Container

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: inject-sidecar
  annotations:
    policies.kyverno.io/title: Inject Sidecar Container
    policies.kyverno.io/category: Sample
    policies.kyverno.io/subject: Deployment,Volume
    policies.kyverno.io/minversion: 1.6.0
    policies.kyverno.io/description: "The sidecar pattern is very common in Kubernetes whereby other applications can insert components via tacit modification of a submitted resource. This is, for example, often how service meshes and secrets applications are able to function transparently. This policy injects a sidecar container, initContainer, and volume into Pods that match an annotation called `vault.hashicorp.com/agent-inject: true`."
spec:
  rules:
    - name: inject-sidecar
      match:
        any:
          - resources:
              kinds:
                - Deployment
      mutate:
        patchStrategicMerge:
          spec:
            template:
              metadata:
                annotations:
                  (vault.hashicorp.com/agent-inject): "true"
              spec:
                containers:
                  - name: vault-agent
                    image: vault:1.5.4
                    imagePullPolicy: IfNotPresent
                    volumeMounts:
                      - mountPath: /vault/secrets
                        name: vault-secret
                initContainers:
                  - name: vault-agent-init
                    image: vault:1.5.4
                    imagePullPolicy: IfNotPresent
                    volumeMounts:
                      - mountPath: /vault/secrets
                        name: vault-secret
                volumes:
                  - name: vault-secret
                    emptyDir:
                      medium: Memory