gcp_external_ip_access_v1.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.
#
apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-external-ip-access-v1
  annotations:
    # Example of tying a template to a CIS benchmark
    benchmark: CIS11_5.03
spec:
  crd:
    spec:
      names:
        kind: GCPExternalIpAccessConstraintV1
      validation:
        openAPIV3Schema:
          properties:
            mode:
              type: string
              enum: [blacklist, whitelist]
            instances:
              type: array
              items:
                type: string
  targets:
   validation.gcp.forsetisecurity.org:
      rego: |
            #
            # Copyright 2018 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.GCPExternalIpAccessConstraintV1
            
            import data.validator.gcp.lib as lib
            
            ###########################
            # Find Whitelist Violations
            ###########################
            deny[{
            	"msg": message,
            	"details": metadata,
            }] {
            	constraint := input.constraint
            	lib.get_constraint_params(constraint, params)
            	asset := input.asset
            	asset.asset_type == "compute.googleapis.com/Instance"
            
            	# Find network access config block w/ external IP
            	instance := asset.resource.data
            	access_config := instance.networkInterface[_].accessConfig
            	external_ip := access_config[_].externalIp
            
            	# Check if instance is in blacklist/whitelist
            	target_instances := params.instances
            	matches := {asset.name} & cast_set(target_instances)
            	target_instance_match_count(params.mode, desired_count)
            	count(matches) == desired_count
            
            	message := sprintf("%v is not allowed to have an external IP.", [asset.name])
            	metadata := {"external_ip": external_ip}
            }
            
            ###########################
            # Rule Utilities
            ###########################
            
            # Determine the overlap between instances under test and constraint
            # By default (whitelist), we violate if there isn't overlap
            target_instance_match_count(mode) = 0 {
            	mode != "blacklist"
            }
            
            target_instance_match_count(mode) = 1 {
            	mode == "blacklist"
            }