template.yaml

# Copyright 2021 Open Policy Agent
#
# 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.

# https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/general/imagedigests/template.yaml
apiVersion: templates.gatekeeper.sh/v1beta1
kind: ConstraintTemplate
metadata:
  name: imagedigests
  annotations:
    description: Requires container images to contain a digest.
spec:
  crd:
    spec:
      names:
        kind: ImageDigests
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package imagedigests

        violation[{"msg": msg}] {
          container := input.review.object.spec.containers[_]
          satisfied := [re_match("@[a-z0-9]+([+._-][a-z0-9]+)*:[a-zA-Z0-9=_-]+", container.image)]
          not all(satisfied)
          msg := sprintf("container <%v> uses an image without a digest <%v>", [container.name, container.image])
        }

        violation[{"msg": msg}] {
          container := input.review.object.spec.initContainers[_]
          satisfied := [re_match("@[a-z0-9]+([+._-][a-z0-9]+)*:[a-zA-Z0-9=_-]+", container.image)]
          not all(satisfied)
          msg := sprintf("initContainer <%v> uses an image without a digest <%v>", [container.name, container.image])
        }