Required Labels

Description

Requires resources to contain specified labels, with values matching provided regular expressions.

Template

apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8srequiredlabels
  annotations:
    metadata.gatekeeper.sh/title: "Required Labels"
    metadata.gatekeeper.sh/version: 1.0.1
    description: >-
      Requires resources to contain specified labels, with values matching
      provided regular expressions.
spec:
  crd:
    spec:
      names:
        kind: K8sRequiredLabels
      validation:
        openAPIV3Schema:
          type: object
          properties:
            message:
              type: string
            labels:
              type: array
              description: >-
                A list of labels and values the object must specify.
              items:
                type: object
                properties:
                  key:
                    type: string
                    description: >-
                      The required label.
                  allowedRegex:
                    type: string
                    description: >-
                      If specified, a regular expression the annotation's value
                      must match. The value must contain at least one match for
                      the regular expression.
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package k8srequiredlabels

        get_message(parameters, _default) := _default {
          not parameters.message
        }

        get_message(parameters, _) := parameters.message

        violation[{"msg": msg, "details": {"missing_labels": missing}}] {
          provided := {label | input.review.object.metadata.labels[label]}
          required := {label | label := input.parameters.labels[_].key}
          missing := required - provided
          count(missing) > 0
          def_msg := sprintf("you must provide labels: %v", [missing])
          msg := get_message(input.parameters, def_msg)
        }

        violation[{"msg": msg}] {
          value := input.review.object.metadata.labels[key]
          expected := input.parameters.labels[_]
          expected.key == key
          # do not match if allowedRegex is not defined, or is an empty string
          expected.allowedRegex != ""
          not regex.match(expected.allowedRegex, value)
          def_msg := sprintf("Label <%v: %v> does not satisfy allowed regex: %v", [key, value, expected.allowedRegex])
          msg := get_message(input.parameters, def_msg)
        }

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/general/requiredlabels/template.yaml

Examples

must-have-owner

constraint

apiVersion: constraints.gatekeeper.sh/v1beta1
kind: K8sRequiredLabels
metadata:
  name: all-must-have-owner
spec:
  match:
    kinds:
      - apiGroups: [""]
        kinds: ["Namespace"]
  parameters:
    message: "All namespaces must have an `owner` label that points to your company username"
    labels:
      - key: owner
        allowedRegex: "^[a-zA-Z]+.agilebank.demo$"

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/general/requiredlabels/samples/all-must-have-owner/constraint.yaml

example-allowed

apiVersion: v1
kind: Namespace
metadata:
  name: allowed-namespace
  labels:
    owner: user.agilebank.demo

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/general/requiredlabels/samples/all-must-have-owner/example_allowed.yaml

example-disallowed

apiVersion: v1
kind: Namespace
metadata:
  name: disallowed-namespace

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/general/requiredlabels/samples/all-must-have-owner/example_disallowed.yaml