← Policy catalog
</> ValidatingAdmissionPolicy · Apache-2.0

Binds a Role to an Anonymous Identity

clusterrolebinding-anonymous-subjects

severityModerate resourceClusterRoleBindings productKubernetes bundles1

Binding a ClusterRole to system:anonymous grants it cluster-wide to every unauthenticated caller that reaches the API server, and catch-all names like everyone or all-users leave nobody accountable for who exercises it.

Rejects unless

!has(object.subjects) || object.subjects.all(s,
  !(s.kind == "User" && variables.anonymousNames.exists(n, n == s.name))
)

ClusterRoleBindings must not bind roles to anonymous or broadly shared user identities.

Variables

anonymousNames

["system:anonymous","everyone","all-users"]

Remediation

Replace the anonymous or shared user subject with the specific named users, groups or ServiceAccounts that need the role. Fields: subjects[*].kind, subjects[*].name.

Applies to

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

Manifest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: clusterrolebinding-anonymous-subjects
  annotations:
    kubeapt.io/uuid: "2cf111fd-543c-4375-aca7-a3ffd4e6f700"
    security.kubeapt.io/displayName: "Binds a Role to an Anonymous Identity"
    security.kubeapt.io/description: "Binding a ClusterRole to system:anonymous grants it cluster-wide to every unauthenticated caller that reaches the API server, and catch-all names like everyone or all-users leave nobody accountable for who exercises it."
    security.kubeapt.io/resource: "ClusterRoleBindings"
    security.kubeapt.io/severity: "Moderate"
    security.kubeapt.io/remediation: "Replace the anonymous or shared user subject with the specific named users, groups or ServiceAccounts that need the role. Fields: subjects[*].kind, subjects[*].name."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - rbac.authorization.k8s.io
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - clusterrolebindings
  variables:
  - name: anonymousNames
    expression: |
      ["system:anonymous","everyone","all-users"]
  validations:
  - expression: |
      !has(object.subjects) || object.subjects.all(s,
        !(s.kind == "User" && variables.anonymousNames.exists(n, n == s.name))
      )
    message: |
      ClusterRoleBindings must not bind roles to anonymous or broadly shared user identities.

Save it as clusterrolebinding-anonymous-subjects.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 ./clusterrolebinding-anonymous-subjects.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 clusterrolebinding-anonymous-subjects -r ./manifests

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

$ kubeapt validate --policy-name clusterrolebinding-anonymous-subjects -A

Bundles

Source

View policy.yaml on GitHub →