Skip to main content

Privileged Container

Description​

Controls the ability of any container to enable privileged mode. Corresponds to the privileged field in a PodSecurityPolicy. For more information, see https://kubernetes.io/docs/concepts/policy/pod-security-policy/#privileged

Template​

apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8spspprivilegedcontainer
  annotations:
    metadata.gatekeeper.sh/title: "Privileged Container"
    metadata.gatekeeper.sh/version: 1.1.2
    description: >-
      Controls the ability of any container to enable privileged mode.
      Corresponds to the `privileged` field in a PodSecurityPolicy. For more
      information, see
      https://kubernetes.io/docs/concepts/policy/pod-security-policy/#privileged
spec:
  crd:
    spec:
      names:
        kind: K8sPSPPrivilegedContainer
      validation:
        openAPIV3Schema:
          type: object
          description: >-
            Controls the ability of any container to enable privileged mode.
            Corresponds to the `privileged` field in a PodSecurityPolicy. For more
            information, see
            https://kubernetes.io/docs/concepts/policy/pod-security-policy/#privileged
          properties:
            exemptImages:
              description: >-
                Any container that uses an image that matches an entry in this list will be excluded
                from enforcement. Prefix-matching can be signified with `*`. For example: `my-image-*`.

                It is recommended that users use the fully-qualified Docker image name (e.g. start with a domain name)
                in order to avoid unexpectedly exempting images from an untrusted repository.
              type: array
              items:
                type: string
  targets:
    - target: admission.k8s.gatekeeper.sh
      code:
      - engine: K8sNativeValidation
        source:
          variables:
          - name: containers
            expression: 'has(variables.anyObject.spec.containers) ? variables.anyObject.spec.containers : []'
          - name: initContainers
            expression: 'has(variables.anyObject.spec.initContainers) ? variables.anyObject.spec.initContainers : []'
          - name: ephemeralContainers
            expression: 'has(variables.anyObject.spec.ephemeralContainers) ? variables.anyObject.spec.ephemeralContainers : []'
          - name: exemptImagePrefixes
            expression: |
              !has(variables.params.exemptImages) ? [] :
                variables.params.exemptImages.filter(image, image.endsWith("*")).map(image, string(image).replace("*", ""))
          - name: exemptImageExplicit
            expression: |
              !has(variables.params.exemptImages) ? [] : 
                variables.params.exemptImages.filter(image, !image.endsWith("*"))
          - name: exemptImages
            expression: |
              (variables.containers + variables.initContainers + variables.ephemeralContainers).filter(container,
                container.image in variables.exemptImageExplicit ||
                variables.exemptImagePrefixes.exists(exemption, string(container.image).startsWith(exemption))
              ).map(container, container.image)
          - name: badContainers
            expression: |
              (variables.containers + variables.initContainers + variables.ephemeralContainers).filter(container,
                !(container.image in variables.exemptImages) &&
                (has(container.securityContext) && has(container.securityContext.privileged) && container.securityContext.privileged)
              ).map(container, "Privileged container is not allowed: " + container.name +", securityContext.privileged: true")
          - name: isUpdate
            expression: has(request.operation) && request.operation == "UPDATE"
          validations:
          - expression: variables.isUpdate || size(variables.badContainers) == 0
            messageExpression: 'variables.badContainers.join(", ")' 
      - engine: Rego
        source:
          rego: |
            package k8spspprivileged

            import data.lib.exclude_update.is_update
            import data.lib.exempt_container.is_exempt

            violation[{"msg": msg, "details": {}}] {
                # spec.containers.privileged field is immutable.
                not is_update(input.review)

                c := input_containers[_]
                not is_exempt(c)
                c.securityContext.privileged
                msg := sprintf("Privileged container is not allowed: %v, securityContext: %v", [c.name, c.securityContext])
            }

            input_containers[c] {
                c := input.review.object.spec.containers[_]
            }

            input_containers[c] {
                c := input.review.object.spec.initContainers[_]
            }

            input_containers[c] {
                c := input.review.object.spec.ephemeralContainers[_]
            }
          libs:
            - |
              package lib.exclude_update

              is_update(review) {
                  review.operation == "UPDATE"
              }
            - |
              package lib.exempt_container

              is_exempt(container) {
                  exempt_images := object.get(object.get(input, "parameters", {}), "exemptImages", [])
                  img := container.image
                  exemption := exempt_images[_]
                  _matches_exemption(img, exemption)
              }

              _matches_exemption(img, exemption) {
                  not endswith(exemption, "*")
                  exemption == img
              }

              _matches_exemption(img, exemption) {
                  endswith(exemption, "*")
                  prefix := trim_suffix(exemption, "*")
                  startswith(img, prefix)
              }

Usage​

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/template.yaml

Examples​

privileged-containers-disallowed
constraint
apiVersion: constraints.gatekeeper.sh/v1beta1
kind: K8sPSPPrivilegedContainer
metadata:
  name: psp-privileged-container
spec:
  match:
    kinds:
      - apiGroups: [""]
        kinds: ["Pod"]
    excludedNamespaces: ["kube-system"]
  parameters:
    exemptImages:
    - "safeimages.com/*"

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/samples/psp-privileged-container/constraint.yaml
example-disallowed
apiVersion: v1
kind: Pod
metadata:
  name: nginx-privileged-disallowed
  labels:
    app: nginx-privileged
spec:
  containers:
  - name: nginx
    image: nginx
    securityContext:
      privileged: true
  initContainers:
  - name: nginx-init
    image: nginx
    securityContext:
      privileged: true

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/samples/psp-privileged-container/example_disallowed.yaml
example-allowed
apiVersion: v1
kind: Pod
metadata:
  name: nginx-privileged-allowed
  labels:
    app: nginx-privileged
spec:
  containers:
  - name: nginx
    image: nginx
    securityContext:
      privileged: false

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/samples/psp-privileged-container/example_allowed.yaml
disallowed-ephemeral
apiVersion: v1
kind: Pod
metadata:
  name: nginx-privileged-disallowed
  labels:
    app: nginx-privileged
spec:
  ephemeralContainers:
  - name: nginx
    image: nginx
    securityContext:
      privileged: true

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/samples/psp-privileged-container/disallowed_ephemeral.yaml
exempted-image
apiVersion: v1
kind: Pod
metadata:
  name: nginx-privileged-allowed-exempt
  labels:
    app: nginx-privileged
spec:
  containers:
  - name: nginx
    image: safeimages.com/nginx
    securityContext:
      privileged: true

Usage

kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/gatekeeper-library/master/library/pod-security-policy/privileged-containers/samples/psp-privileged-container/example_allowed_exempt.yaml