policy-library/policies/templates/gcp_gke_cluster_location.yaml

# Copyright 2021 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-gke-cluster-location-v2
spec:
  crd:
    spec:
      names:
        kind: GKEClusterLocationConstraintV3
      validation:
        openAPIV3Schema:
          properties:
            mode:
              type: string
              enum: [denylist, allowlist]
              description: "String identifying the operational mode, allowlist or
                denylist. In allowlist mode, GKE clusters are only allowed in the
                locations specified in the 'locations' parameter. In denylist mode,
                resources are allowed in all locations except those listed in the
                'locations' parameter."
            exemptions:
              type: array
              items:
                type: string
              description: "Array of GKE clusters to exempt from location restriction.
                String values in the array should correspond to the full name values
                of exempted GKE clusters, e.g. //container.googleapis.com/projects/project-abc/zones/us-central1-c/clusters/my-cluster."
            locations:
              type: array
              items:
                type: string
              description: "Array of regions and/or zones in which GKE clusters can
                be created, e.g. us-central1-a, us-east1. Multiple locations can be
                specified. Regions and zones need to be specified separately, as this
                allows for restricting clusters to be zonal or regional, e.g. allowlisting
                us-central1 will allow regional clusters to be created, but will not
                implicitly allow zonal clusters in any us-central1 zone."
  targets:
    validation.gcp.forsetisecurity.org:
      rego: |-
        #
        # Copyright 2021 Google LLC
        #
        # Licensed under the Apache License, Version 2.0 (the "License");
        # you may not use this file except in compliance with the License.
        # You may obtain a copy of the License at
        #
        #     https://www.apache.org/licenses/LICENSE-2.0
        #
        # Unless required by applicable law or agreed to in writing, software
        # distributed under the License is distributed on an "AS IS" BASIS,
        # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
        # See the License for the specific language governing permissions and
        # limitations under the License.
        #

        package templates.gcp.GKEClusterLocationConstraintV3

        import data.validator.gcp.lib as lib

        deny[{
        	"msg": message,
        	"details": metadata,
        }] {
        	constraint := input.constraint
        	lib.get_constraint_params(constraint, params)
        	asset := input.asset
        	asset.asset_type == "container.googleapis.com/Cluster"

        	# Check if resource is in exempt list
        	exempt_list := params.exemptions
        	matches := {asset.name} & cast_set(exempt_list)
        	count(matches) == 0

        	# Check that location is in allowlist/denylist
        	target_location := asset.resource.data.location
        	asset_location := params.locations
        	location_matches := {target_location} & cast_set(asset_location)
        	target_location_match_count(params.mode, desired_count)
        	count(location_matches) == desired_count

        	message := sprintf("Cluster %v is in a disallowed location", [asset.name])
        	metadata := {"resource": asset.name}
        }

        ###########################
        # Rule Utilities
        ###########################

        # Determine the overlap between locations under test and constraint
        # By default (allowlist), we violate if there isn't overlap.

        target_location_match_count(mode) = 0 {
        	mode != "denylist"
        }

        target_location_match_count(mode) = 1 {
        	mode == "denylist"
        }
        #ENDINLINE