gcp_iam_allowed_policy_member_domains_v1.yaml

# Copyright 2019 Google Inc.
#
# 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-iam-allowed-policy-member-domains-v1
spec:
  crd:
    spec:
      names:
        kind: GCPIAMAllowedPolicyMemberDomainsConstraintV1
      validation:
        openAPIV3Schema:
          properties:
            # Array of IAM policy member types to whitelist. IAM member types
            # in this list will not be checked by the constraint.
            # See https://cloud.google.com/iam/reference/rest/v1/Binding
            # for the typical types. Types are specified here without the ":"
            # suffix. By default, "projectOwner", "projectEditor", and
            # "projectViewer" types are whitelisted. Those are used in GCS and
            # BigQuery. See https://cloud.google.com/storage/docs/access-control/iam
            # and https://cloud.google.com/bigquery/docs/access-control for
            # more information.
            member_type_whitelist:
              type: array
              items:
                type: string
            # Array of domains to whitelist.
            domains:
              type: array
              items:
                type: string
            # Whether or not to allow subdomains. If true, all subdomains of whitelisted
            # domains are whitelisted as well.
            # For example, whitelisting "example.com" will cause IAM policy
            # member "user@sub.example.com" to be accepted.
            allow_sub_domains:
              type: boolean

  targets:
   validation.gcp.forsetisecurity.org:
      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.GCPIAMAllowedPolicyMemberDomainsConstraintV1
            
            import data.validator.gcp.lib as lib
            
            deny[{
            	"msg": message,
            	"details": metadata,
            }] {
            	constraint := input.constraint
            	lib.get_constraint_params(constraint, params)
            	asset := input.asset
            	unique_members := {m | m = asset.iam_policy.bindings[_].members[_]}
            	member_type_whitelist := lib.get_default(params, "member_type_whitelist", ["projectOwner", "projectEditor", "projectViewer"])
            
            	members_to_check := [m | m = unique_members[_]; not starts_with_whitelisted_type(member_type_whitelist, m)]
            	member := members_to_check[_]
            	allow_sub_domains := lib.get_default(params, "allow_sub_domains", true)
            	no_match(allow_sub_domains, params.domains, member)
            
            	message := sprintf("IAM policy for %v contains member from unexpected domain: %v", [asset.name, member])
            
            	metadata := {"resource": asset.name, "member": member}
            }
            
            no_match(allow_sub_domains, domains, member) {
            	allow_sub_domains == true
            	matched_domains := [m | m = member; re_match(sprintf("[:@.]%v$", [domains[_]]), member)]
            	count(matched_domains) == 0
            }
            
            no_match(allow_sub_domains, domains, member) {
            	allow_sub_domains == false
            	matched_domains := [m | m = member; re_match(sprintf("[:@]%v$", [domains[_]]), member)]
            	count(matched_domains) == 0
            }
            
            starts_with_whitelisted_type(whitelist, member) {
            	member_type := whitelist[_]
            	startswith(member, sprintf("%v:", [member_type]))
            }