cenroq · securing your clusters.

Rejects unless

!has(object.rules) || object.rules.all(r,
  !(
    (has(r.apiGroups) && has(r.resources) && has(r.verbs) &&
     r.apiGroups.exists(ag, ag == "") &&
     r.resources.exists(res, res == "pods") &&
     r.verbs.exists(v, variables.podWriteVerbs.exists(pv, pv == v)))
    ||
    (has(r.apiGroups) && has(r.resources) && has(r.verbs) &&
     r.apiGroups.exists(ag, ag == "") &&
     r.resources.exists(res, variables.execResources.exists(er, er == res)) &&
     r.verbs.exists(v, v == "create"))
  )
)

ClusterRoles must not allow pod creation/modification or exec/attach/portforward/ephemeralcontainers access.

Variables

podWriteVerbs

["create","update","patch","delete"]

execResources

["pods/exec","pods/attach","pods/portforward","pods/ephemeralcontainers"]

Remediation

Remove create, update, patch and delete on pods, and the create verb on the pods/exec, pods/attach, pods/portforward and pods/ephemeralcontainers subresources. Fields: rules[*].apiGroups, rules[*].resources, rules[*].verbs.

Applies to

clusterroles · rbac.authorization.k8s.io/v1 · CREATE, UPDATE

Manifest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: clusterrole-pod-exec-create
  annotations:
    kubeapt.io/uuid: "2c6c1af9-6e01-45bf-8d23-a17811b4dae0"
    security.kubeapt.io/displayName: "Grants Pod Create and Exec Access"
    security.kubeapt.io/description: "Pod write lets the holder run arbitrary images with any service account token in the cluster mounted, while exec, attach, port-forward and ephemeral container access opens a shell into running workloads and their credentials."
    security.kubeapt.io/resource: "ClusterRoles"
    security.kubeapt.io/severity: "Critical"
    security.kubeapt.io/remediation: "Remove create, update, patch and delete on pods, and the create verb on the pods/exec, pods/attach, pods/portforward and pods/ephemeralcontainers subresources. Fields: rules[*].apiGroups, rules[*].resources, rules[*].verbs."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - rbac.authorization.k8s.io
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - clusterroles
  variables:
  - name: podWriteVerbs
    expression: |
      ["create","update","patch","delete"]
  - name: execResources
    expression: |
      ["pods/exec","pods/attach","pods/portforward","pods/ephemeralcontainers"]
  validations:
  - expression: |
      !has(object.rules) || object.rules.all(r,
        !(
          (has(r.apiGroups) && has(r.resources) && has(r.verbs) &&
           r.apiGroups.exists(ag, ag == "") &&
           r.resources.exists(res, res == "pods") &&
           r.verbs.exists(v, variables.podWriteVerbs.exists(pv, pv == v)))
          ||
          (has(r.apiGroups) && has(r.resources) && has(r.verbs) &&
           r.apiGroups.exists(ag, ag == "") &&
           r.resources.exists(res, variables.execResources.exists(er, er == res)) &&
           r.verbs.exists(v, v == "create"))
        )
      )
    message: |
      ClusterRoles must not allow pod creation/modification or exec/attach/portforward/ephemeralcontainers access.

Save it as clusterrole-pod-exec-create.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 ./clusterrole-pod-exec-create.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 clusterrole-pod-exec-create -r ./manifests

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

$ kubeapt validate --policy-name clusterrole-pod-exec-create -A

Bundles

cenroq-best-practices

Source

View policy.yaml on GitHub →