gcp_compute_allowed_networks.yaml

# Copyright 2019 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.
#
# Checks network interfaces on a compute instance against a provided allowlist of networks

apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-compute-allowed-networks-v2
spec:
  crd:
    spec:
      names:
        kind: GCPComputeAllowedNetworksConstraintV2
      validation:
        openAPIV3Schema:
          properties:
            allowed:
              description: "A list of full object URIs of the networks allowed, for example: ['https://www.googleapis.com/compute/v1/projects/vpc-sc-pub-sub-billing-alerts/global/networks/default1']"
              type: array
              items:
                type: string
  targets:
    validation.gcp.forsetisecurity.org:
      rego: | #INLINE("validator/compute_network_interface.rego")
            #
            # Copyright 2019 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.GCPComputeAllowedNetworksConstraintV2
            
            import data.validator.gcp.lib as lib
            
            deny[{
            	"msg": message,
            	"details": metadata,
            }] {
            	constraint := input.constraint
            	asset := input.asset
            	asset.asset_type == "compute.googleapis.com/Instance"
            
            	lib.get_constraint_params(input.constraint, params)
            
            	instance := asset.resource.data
            
            	interfaces := lib.get_default(instance, "networkInterfaces", [])
            	interface := interfaces[_]
            	full_network_uri := interface.network
            
            	allowlist := lib.get_default(params, "allowed", [])
            	allowed_networks := {n | n = allowlist[_]}
            
            	access_configs := lib.get_default(interface, "accessConfigs", [])
            
            	is_external_network := count(access_configs) > 0
            	is_network_allowed := count({full_network_uri} - allowed_networks) == 0
            
            	is_external_network == true
            	is_network_allowed == false
            
            	message := sprintf("Compute instance %v has interface %v with invalid access configuration.", [asset.name, interface.name])
            	metadata := {"resource": asset.name}
            }
            #ENDINLINE