Restrict Adding Capabilities

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: psp-restrict-adding-capabilities
  annotations:
    policies.kyverno.io/title: Restrict Adding Capabilities
    policies.kyverno.io/category: PSP Migration
    policies.kyverno.io/severity: medium
    kyverno.io/kyverno-version: 1.6.0
    policies.kyverno.io/minversion: 1.6.0
    kyverno.io/kubernetes-version: "1.23"
    policies.kyverno.io/subject: Pod
    policies.kyverno.io/description: Adding capabilities is a way for containers in a Pod to request higher levels of ability than those with which they may be provisioned. Many capabilities allow system-level control and should be prevented. Pod Security Policies (PSP) allowed a list of "good" capabilities to be added. This policy checks ephemeralContainers, initContainers, and containers to ensure the only capabilities that can be added are either NET_BIND_SERVICE or CAP_CHOWN.
spec:
  validationFailureAction: Audit
  background: true
  rules:
    - name: allowed-capabilities
      match:
        any:
          - resources:
              kinds:
                - Pod
      preconditions:
        all:
          - key: "{{ request.operation || 'BACKGROUND' }}"
            operator: NotEquals
            value: DELETE
      validate:
        message: Any capabilities added other than NET_BIND_SERVICE or CAP_CHOWN are disallowed.
        foreach:
          - list: request.object.spec.[ephemeralContainers, initContainers, containers][]
            deny:
              conditions:
                all:
                  - key: "{{ element.securityContext.capabilities.add[] || '' }}"
                    operator: AnyNotIn
                    value:
                      - NET_BIND_SERVICE
                      - CAP_CHOWN
                      - ""