cenroq · securing your clusters.

Rejects unless

!has(object.data) || !object.data.exists(
  k,
  v,
  k.lowerAscii().matches(".*\\.(sh|bash|py|lua|js|ts|rb|pl|php|groovy|tmpl)$") ||
  v.matches("(?s).*#!/\\S+") ||
  v.matches("(?i).*\\b(function|import|require|process|exec)\\b.*")
)

Do not store executable code or scripts in ConfigMaps that applications run.

Remediation

Move scripts, shebang files and other executable content into the container image or a signed artifact, keeping only inert configuration values in the ConfigMap. Field: data.

Applies to

configmaps · v1 · CREATE, UPDATE

Manifest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: configmap-executable-code
  annotations:
    kubeapt.io/uuid: "2d9872e4-6538-497b-b9f1-64479e562fcd"
    security.kubeapt.io/displayName: "Stores Executable Code or Scripts"
    security.kubeapt.io/description: "Scripts stored in a ConfigMap and executed by a pod turn ConfigMap write access into code execution inside the container, bypassing image scanning, image signing and any review of what actually runs."
    security.kubeapt.io/resource: "ConfigMaps"
    security.kubeapt.io/severity: "Moderate"
    security.kubeapt.io/remediation: "Move scripts, shebang files and other executable content into the container image or a signed artifact, keeping only inert configuration values in the ConfigMap. Field: data."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - ''
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - configmaps
  validations:
  - expression: |
      !has(object.data) || !object.data.exists(
        k,
        v,
        k.lowerAscii().matches(".*\\.(sh|bash|py|lua|js|ts|rb|pl|php|groovy|tmpl)$") ||
        v.matches("(?s).*#!/\\S+") ||
        v.matches("(?i).*\\b(function|import|require|process|exec)\\b.*")
      )
    message: |
      Do not store executable code or scripts in ConfigMaps that applications run.

Save it as configmap-executable-code.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 ./configmap-executable-code.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 configmap-executable-code -r ./manifests

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

$ kubeapt validate --policy-name configmap-executable-code -A

Bundles

cenroq-best-practices

Source

View policy.yaml on GitHub →