policy-library/policies/templates/gcp_iam_allowed_bindings.yaml

# 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.

apiVersion: templates.gatekeeper.sh/v1alpha1
kind: ConstraintTemplate
metadata:
  name: gcp-iam-allowed-bindings-v3
spec:
  crd:
    spec:
      names:
        kind: GCPIAMAllowedBindingsConstraintV3
      validation:
        openAPIV3Schema:
          properties:
            mode:
              description: "Enforcement mode, defaults to allowlist"
              type: string
              enum: [denylist, allowlist]
            assetType:
              description: "Restrict which asset type this policy applies to"
              type: string
            assetNames:
              description: "CAI name of asset to restrict which specific assets this
                policy applies to. assetNames must have the same assetType defined
                above. E.g. '//bigquery.googleapis.com/projects/my-project/datasets/my-dataset'"
              type: array
              items:
                type: string
            role:
              description: "Role to restrict bindings for, ex. roles/owner; Wildcards
                (*) supported"
              type: string
            members:
              description: "Members to either allow or deny for the given role, depending
                on mode; Wildcards (*) supported"
              type: array
              items:
                type: string
  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.GCPIAMAllowedBindingsConstraintV3

        import data.validator.gcp.lib as lib

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

        	check_asset_type(asset, params)

        	# Check if resource is part of asset names to scan
        	include_list := lib.get_default(params, "assetNames", [])
        	is_included(include_list, asset.name)

        	binding := asset.iam_policy.bindings[_]
        	member := binding.members[_]
        	role := binding.role

        	glob.match(params.role, ["/"], role)

        	mode := lib.get_default(params, "mode", "allowlist")

        	matches_found = [m | m = config_pattern(params.members[_]); glob.match(m, [], member)]
        	target_match_count(mode, desired_count)
        	count(matches_found) != desired_count

        	message := sprintf("IAM policy for %v grants %v to %v", [asset.name, role, member])

        	metadata := {
        		"resource": asset.name,
        		"member": member,
        		"role": role,
        	}
        }

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

        # Determine the overlap between matches under test and constraint
        target_match_count(mode) = 0 {
        	mode == "denylist"
        }

        target_match_count(mode) = 1 {
        	mode == "allowlist"
        }

        check_asset_type(asset, params) {
        	lib.has_field(params, "assetType")
        	params.assetType == asset.asset_type
        }

        check_asset_type(asset, params) {
        	lib.has_field(params, "assetType") == false
        }

        is_included(include_list, asset_name) {
        	include_list != []
        	glob.match(include_list[_], ["/"], asset_name)
        }

        is_included(include_list, asset_name) {
        	include_list == []
        }

        # If the member in constraint is written as a single "*", turn it into super
        # glob "**". Otherwise, we won't be able to match everything.
        config_pattern(old_pattern) = "**" {
        	old_pattern == "*"
        }

        config_pattern(old_pattern) = old_pattern {
        	old_pattern != "*"
        }
        #ENDINLINE