# 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 Cloud SQL instances to specific locations in GCP.
# Location names need to be exact match. It supports
# allowlist or denylist modes, as well as exempting selected
# Cloud SQL instances from the list.

apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-sql-location-v1
spec:
  crd:
    spec:
      names:
        kind: GCPSQLLocationConstraintV1
      validation:
        openAPIV3Schema:
          properties:
            mode:
              type: string
              enum: [denylist, allowlist]
              description: "String identifying the operational mode, allowlist or
                denylist. In allowlist mode, datasets 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 Cloud SQL instances to exempt from location restriction.
                String values in the array should correspond to the full name values
                of exempted Cloud SQL instances."
            locations:
              type: array
              items:
                type: string
              description: "Array of location names to be allowed or denied. Should
                be the region names (e.g. us-west2), as defined at https://cloud.google.com/sql/docs/mysql/locations
                and https://cloud.google.com/sql/docs/postgres/locations. Location
                names need to be exact match."
  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.GCPSQLLocationConstraintV1

        import data.validator.gcp.lib as lib

        ############################################
        # Find Cloud SQL Location Violations
        ############################################
        deny[{
        	"msg": message,
        	"details": metadata,
        }] {
        	constraint := input.constraint
        	lib.get_constraint_params(constraint, params)

        	# Verify that resource is Cloud SQL instance
        	asset := input.asset
        	asset.asset_type == "sqladmin.googleapis.com/Instance"

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

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

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