# 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.
#

# This template is for policies restricting the locations of
# Appengine applications in GCP. You can specify a list of regions in the
# "locations" parameter. A cluster in the wrong region will raise a violation.

apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-appengine-location-v1
spec:
  crd:
    spec:
      names:
        kind: GCPAppengineLocationConstraintV1
      validation:
        openAPIV3Schema:
          properties:
            locations:
              type: array
              items:
                type: string
              description: "List of GCP regions (or region patterns) for
              Appengine applications locations (i.e 'asia*', 'europe-west2' etc.)."
  targets:
    validation.gcp.forsetisecurity.org:
      rego: | #INLINE("validator/appengine_location.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
        #
        #      http://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.GCPAppengineLocationConstraintV1

        import data.validator.gcp.lib as lib

        deny[{
        	"msg": message,
        	"details": metadata,
        }] {
        	constraint := input.constraint
        	lib.get_constraint_params(constraint, params)

        	asset := input.asset

        	# Applies to appengine applications only
        	asset.asset_type == "appengine.googleapis.com/Application"

        	# Retrieve the list of allowed locations
        	locations := params.locations

        	# The asset raises a violation if location_is_valid is evaluated to false
        	not location_is_valid(asset, locations)

        	message := sprintf("%v is in violation.", [asset.name])
        	metadata := {
        		"resource": asset.name,
        		"valid-locations": locations,
        	}
        }

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

        location_is_valid(asset, locations) {
        	# ensure we have a data object
        	resource := asset.resource.data

        	# Retrieve the location
        	resource_location := resource.locationId

        	# iterate through the locations
        	location := locations[_]

        	# the resource location is valid if it matches one of the passed locations
        	re_match(location, resource_location)
        }
        #ENDINLINE
