Restrict Binding to Cluster-Admin

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: restrict-binding-clusteradmin
 5  annotations:
 6    policies.kyverno.io/title: Restrict Binding to Cluster-Admin
 7    policies.kyverno.io/category: Security
 8    policies.kyverno.io/severity: medium
 9    policies.kyverno.io/subject: RoleBinding, ClusterRoleBinding, RBAC
10    kyverno.io/kyverno-version: 1.6.2
11    policies.kyverno.io/minversion: 1.6.0
12    kyverno.io/kubernetes-version: "1.23"
13    policies.kyverno.io/description: >-
14      The cluster-admin ClusterRole allows any action to be performed on any resource
15      in the cluster and its granting should be heavily restricted. This
16      policy prevents binding to the cluster-admin ClusterRole in
17      RoleBinding or ClusterRoleBinding resources.
18spec:
19  validationFailureAction: Audit
20  background: true
21  rules:
22    - name: clusteradmin-bindings
23      match:
24        any:
25        - resources:
26            kinds:
27              - RoleBinding
28              - ClusterRoleBinding
29      validate:
30        message: "Binding to cluster-admin is not allowed."
31        pattern:
32          roleRef: 
33            name: "!cluster-admin"