Disallow Privilege Escalation in CEL

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: disallow-privilege-escalation
  annotations:
    policies.kyverno.io/title: Disallow Privilege Escalation in CEL
    policies.kyverno.io/category: Pod Security Standards (Restricted) in CEL
    policies.kyverno.io/severity: medium
    policies.kyverno.io/subject: Pod
    policies.kyverno.io/minversion: 1.11.0
    kyverno.io/kyverno-version: 1.11.0
    kyverno.io/kubernetes-version: 1.26-1.27
    policies.kyverno.io/description: Privilege escalation, such as via set-user-ID or set-group-ID file mode, should not be allowed. This policy ensures the `allowPrivilegeEscalation` field is set to `false`.
spec:
  validationFailureAction: Audit
  background: true
  rules:
    - name: privilege-escalation
      match:
        any:
          - resources:
              kinds:
                - Pod
              operations:
                - CREATE
                - UPDATE
      validate:
        cel:
          variables:
            - name: allContainers
              expression: object.spec.containers +  object.spec.?initContainers.orValue([]) +  object.spec.?ephemeralContainers.orValue([])
          expressions:
            - expression: variables.allContainers.all(container,  container.?securityContext.allowPrivilegeEscalation.orValue(true) == false)
              message: Privilege escalation is disallowed.  All containers must set the securityContext.allowPrivilegeEscalation field to `false`.