Disallow Custom Snippets

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: disallow-ingress-nginx-custom-snippets
  annotations:
    policies.kyverno.io/title: Disallow Custom Snippets
    policies.kyverno.io/category: Security, NGINX Ingress
    policies.kyverno.io/subject: ConfigMap, Ingress
    policies.kyverno.io/minversion: 1.6.0
    kyverno.io/kyverno-version: 1.6.0
    kyverno.io/kubernetes-version: "1.23"
    policies.kyverno.io/description: "Users that can create or update ingress objects can use the custom snippets  feature to obtain all secrets in the cluster (CVE-2021-25742). This policy  disables allow-snippet-annotations in the ingress-nginx configuration and  blocks *-snippet annotations on an Ingress. See: https://github.com/kubernetes/ingress-nginx/issues/7837"
spec:
  validationFailureAction: Enforce
  rules:
    - name: check-config-map
      match:
        any:
          - resources:
              kinds:
                - ConfigMap
      validate:
        message: ingress-nginx allow-snippet-annotations must be set to false
        pattern:
          "=(data)":
            "=(allow-snippet-annotations)": "false"
    - name: check-ingress-annotations
      match:
        any:
          - resources:
              kinds:
                - networking.k8s.io/v1/Ingress
      validate:
        message: ingress-nginx custom snippets are not allowed
        pattern:
          metadata:
            "=(annotations)":
              X(*-snippet): "?*"