← Policy catalog
</> ValidatingAdmissionPolicy · Apache-2.0

Binds a Privileged Role Such as cluster-admin

rolebinding-powerful-roles

severityHigh resourceRoleBindings productKubernetes bundles1

Roles like cluster-admin, admin and edit carry sweeping verbs across nearly every API resource, so one compromised subject in the binding gains full control of the namespace and its secrets.

Rejects unless

!has(object.roleRef) || !(object.roleRef.kind in ["ClusterRole","Role"] &&
  variables.powerfulRoles.exists(rn, rn == object.roleRef.name))

RoleBindings must not reference powerful roles such as cluster-admin/admin/edit.

Variables

powerfulRoles

["cluster-admin","admin","edit","ns-admin","full-access"]

Remediation

Point roleRef at a purpose-built role that lists only the resources and verbs the subject needs. Fields: roleRef.kind, roleRef.name.

Applies to

  • rolebindings · rbac.authorization.k8s.io/v1 · CREATE, UPDATE

Manifest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: rolebinding-powerful-roles
  annotations:
    kubeapt.io/uuid: "c0fb63ca-f7fc-4f04-b552-83c54f503fef"
    security.kubeapt.io/displayName: "Binds a Privileged Role Such as cluster-admin"
    security.kubeapt.io/description: "Roles like cluster-admin, admin and edit carry sweeping verbs across nearly every API resource, so one compromised subject in the binding gains full control of the namespace and its secrets."
    security.kubeapt.io/resource: "RoleBindings"
    security.kubeapt.io/severity: "High"
    security.kubeapt.io/remediation: "Point roleRef at a purpose-built role that lists only the resources and verbs the subject needs. Fields: roleRef.kind, roleRef.name."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - rbac.authorization.k8s.io
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - rolebindings
  variables:
  - name: powerfulRoles
    expression: |
      ["cluster-admin","admin","edit","ns-admin","full-access"]
  validations:
  - expression: |
      !has(object.roleRef) || !(object.roleRef.kind in ["ClusterRole","Role"] &&
        variables.powerfulRoles.exists(rn, rn == object.roleRef.name))
    message: |
      RoleBindings must not reference powerful roles such as cluster-admin/admin/edit.

Save it as rolebinding-powerful-roles.yaml — the commands below assume that name.

Validate with kubeapt

Check a workload against this one policy, before anything is installed on a cluster.

$ kubeapt validate -p ./rolebinding-powerful-roles.yaml -r ./workload.yaml

Or without the file, from the published policy set — -r takes a directory too:

$ kubeapt policies download && kubeapt validate --policy-name rolebinding-powerful-roles -r ./manifests

Or against every namespace in the cluster your kubeconfig points at:

$ kubeapt validate --policy-name rolebinding-powerful-roles -A

Bundles

Source

View policy.yaml on GitHub →