name: resource-lists
policies:
  -  policy.yaml
resources:
  -  resource.yaml
results:
  - policy: resource-lists
    rule: require-image-tag
    resources: 
    - myapp-pod1
    - myapp-pod2
    kind: Pod
    result: pass
  - policy: resource-lists
    rule: validate-image-tag
    resources: 
    - myapp-pod3
    kind: Pod
    result: pass

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: resource-lists
  annotations:
    policies.kyverno.io/category: Best Practices
    policies.kyverno.io/description: >-
      The ':latest' tag is mutable and can lead to unexpected errors if the 
      image changes. A best practice is to use an immutable tag that maps to 
      a specific version of an application pod.      
spec:
  validationFailureAction: audit
  rules:
  - name: require-image-tag
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "An image tag is required."  
      pattern:
        spec:
          containers:
          - image: "*:*"
  - name: validate-image-tag
    match:
      resources:
        kinds:
        - Pod
    validate:
      message: "Using a mutable image tag e.g. 'latest' is not allowed."
      pattern:
        spec:
          containers:
          - image: "!*:latest"

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod1
  labels:
    app: myapp1
spec: 
  containers:
  - name: nginx
    image: nginx:1.12

---
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod2
  labels:
    app: myapp2
spec: 
  containers:
  - name: nginx
    image: nginx:1.12

---
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod3
  labels:
    app: myapp3
spec: 
  containers:
  - name: nginx
    image: nginx:1.12

applying 1 policy to 3 resources...

│───│────────────────│────────────────────│────────────────────────│────────│
│ # │ POLICY         │ RULE               │ RESOURCE               │ RESULT │
│───│────────────────│────────────────────│────────────────────────│────────│
│ 1 │ resource-lists │ require-image-tag  │ default/Pod/myapp-pod1 │ Pass   │
│ 1 │ resource-lists │ require-image-tag  │ default/Pod/myapp-pod2 │ Pass   │
│ 2 │ resource-lists │ validate-image-tag │ default/Pod/myapp-pod3 │ Pass   │
│───│────────────────│────────────────────│────────────────────────│────────│