policies/opa/gatekeeper/constraint-templates/8-svc-clusterip-ext-ips-allowed.yaml

apiVersion: templates.gatekeeper.sh/v1beta1
kind: ConstraintTemplate
metadata:
  name: k8ssvcclusteripexternalipsallow
spec:
  crd:
    spec:
      names:
        kind: K8sSvcClusterIpExternalIpsAllow
        listKind: K8sSvcClusterIpExternalIpsAllowList
        plural: k8ssvcclusteripexternalipsallow
        singular: k8ssvcclusteripexternalipsallow
      validation:
        # Schema for the `parameters` field
        openAPIV3Schema:
          properties:
            allowedOps:
              type: array
              items:
                type: string
            allowedIps:
              type: array
              items:
                type: string
            errMsg:
              type: string
  targets:
    - target: admission.k8s.gatekeeper.sh
      libs: 
        - |
          package lib.k8s.helpers

          allowed_operations = value {
            value := {"CREATE", "UPDATE"}
          }

          review_operation = value {
            value := input.review.operation
          }

          review_metadata_labels = value {
            value := input.review.object.metadata.labels
          }

          review_spec_template_metadata_labels = value {
            value := input.review.object.spec.template.metadata.labels
          }

          deployment_error = value {
            value := "DEPLOYMENT_INVALID"
          }

          deployment_containers = value {
            value := input.review.object.spec.template.spec.containers
          }

          deployment_role = value {
            value := input.review.object.spec.template.metadata.annotations["iam.amazonaws.com/role"]
          }

          ips_allowed(a,x) {
            allowedIPs := {ip | ip := a[_]}
            externalIPs := {ip | ip := x[_]}
            forbiddenIPs := externalIPs - allowedIPs
            count(forbiddenIPs) > 0
          }

          review_object = o {
            o := input.review.object
          }

          review_id = value {
            value := sprintf("%v/%v/%v", [
              review_namespace,
              review_name,
              review_kind
            ])
          }

          review_name = value {
            value := input.review.object.metadata.name
          }

          else = value {
            value := "NOT_FOUND"
          }

          review_namespace = value {
            value := input.review.object.metadata.namespace
          }

          else = value {
            value := "NOT_FOUND"
          }

          review_kind = value {
            value := input.review.kind.kind
          }

          else = value {
            value := "NOT_FOUND"
          }
      rego: |
        package k8sdepregistry

        import data.lib.k8s.helpers as helpers

        violation[{"msg": msg, "details": {}}] {
          helpers.review_operation = input.parameters.allowedOps[_]
          helpers.review_kind = "Service"
          helpers.review_object.spec.type = "ClusterIP"
          helpers.review_object.spec.externalIPs
          aips := input.parameters.allowedIps
          ips := helpers.review_object.spec.externalIPs
          helpers.ips_allowed(aips,ips)
          msg = sprintf("%v: ClusterIP service external IPs are not found in the Allowed IPs list. Allowed IPs: %v, Submitted IPs: %v. Resource ID (ns/name/kind): %v", [input.parameters.errMsg,aips,ips,helpers.review_id])
        }