Restrict Ingress Classes in CEL expressions

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: restrict-ingress-classes
 5  annotations:
 6    policies.kyverno.io/title: Restrict Ingress Classes in CEL expressions
 7    policies.kyverno.io/category: Sample in CEL 
 8    policies.kyverno.io/severity: medium
 9    policies.kyverno.io/subject: Ingress
10    policies.kyverno.io/minversion: 1.11.0
11    kyverno.io/kubernetes-version: "1.26-1.27"
12    policies.kyverno.io/description: >-
13      Ingress classes should only be allowed which match up to deployed Ingress controllers
14      in the cluster. Allowing users to define classes which cannot be satisfied by a deployed
15      Ingress controller can result in either no or undesired functionality. This policy checks
16      Ingress resources and only allows those which define `HAProxy` or `nginx` in the respective
17      annotation. This annotation has largely been replaced as of Kubernetes 1.18 with the IngressClass
18      resource.
19spec:
20  validationFailureAction: Audit
21  background: true
22  rules:
23  - name: validate-ingress
24    match:
25      any:
26      - resources:
27          kinds:
28          - Ingress
29          operations:
30          - CREATE
31          - UPDATE
32    validate:
33      cel:
34        expressions: 
35          - expression: >-
36              object.metadata.?annotations[?'kubernetes.io/ingress.class'].orValue('') in ['HAProxy', 'nginx']      
37            message: "Unknown ingress class."