policyDefinitions/Kubernetes/host-network-ports/template.yaml

apiVersion: templates.gatekeeper.sh/v1beta1
kind: ConstraintTemplate
metadata:
  name: k8sazurehostnetworkingports
spec:
  crd:
    spec:
      names:
        kind: K8sAzureHostNetworkingPorts
      validation:
        # Schema for the `parameters` field
        openAPIV3Schema:
          properties:
            allowHostNetwork:
              type: boolean
            minPort:
              type: integer
            maxPort:
              type: integer
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package k8sazurehostnetworkingports

        violation[{"msg": msg, "details": {}}] {
          container := input_containers[_]
            input_share_hostnetwork(container)
            msg := sprintf("The specified hostNetwork and hostPort are not allowed, pod: %v, container: %v. Allowed values: %v", [input.review.object.metadata.name, container.name, input.parameters])
        }

        input_share_hostnetwork(container) {
            not input.parameters.allowHostNetwork
            input.review.object.spec.hostNetwork
        }

        input_share_hostnetwork(container) {
            hostPort := container.ports[_].hostPort
            hostPort < input.parameters.minPort
        }

        input_share_hostnetwork(container) {
            hostPort := container.ports[_].hostPort
            hostPort > input.parameters.maxPort
        }

        input_containers[c] {
            c := input.review.object.spec.containers[_]
        }

        input_containers[c] {
            c := input.review.object.spec.initContainers[_]
        }