← Policy catalog
</> ValidatingAdmissionPolicy · Apache-2.0

Startup TCP Probe Targets an Arbitrary Host

initcontainer-startupprobe-tcpsocket-host

severityLow resourceInitContainers productKubernetes bundles2

Pointing the startup TCP probe at another host makes the kubelet open connections from the node to an arbitrary address, probing endpoints closed to pods, and a hung init container passes its startup gate.

Rejects unless

!has(object.spec.initContainers) || object.spec.initContainers.all(ic,
  !has(ic.startupProbe) ||
  !has(ic.startupProbe.tcpSocket) ||
  !has(ic.startupProbe.tcpSocket.host) ||
  ic.startupProbe.tcpSocket.host == ""
)

spec.initContainers[*].startupProbe.tcpSocket.host must be undefined or empty ("").

Remediation

Remove the host field so the probe targets the pod IP, or set it to an empty string. Field: spec.initContainers[*].startupProbe.tcpSocket.host.

Applies to

  • pods · v1 · CREATE, UPDATE

Manifest

apiVersion: admissionregistration.k8s.io/v1
kind: ValidatingAdmissionPolicy
metadata:
  name: initcontainer-startupprobe-tcpsocket-host
  annotations:
    kubeapt.io/uuid: "b45fe463-3d31-457e-9ad3-850462f795ff"
    security.kubeapt.io/displayName: "Startup TCP Probe Targets an Arbitrary Host"
    security.kubeapt.io/description: "Pointing the startup TCP probe at another host makes the kubelet open connections from the node to an arbitrary address, probing endpoints closed to pods, and a hung init container passes its startup gate."
    security.kubeapt.io/resource: "InitContainers"
    security.kubeapt.io/severity: "Low"
    security.kubeapt.io/remediation: "Remove the host field so the probe targets the pod IP, or set it to an empty string. Field: spec.initContainers[*].startupProbe.tcpSocket.host."
    security.kubeapt.io/product: "Kubernetes"
spec:
  failurePolicy: Fail
  matchConstraints:
    resourceRules:
    - apiGroups:
      - ''
      apiVersions:
      - v1
      operations:
      - CREATE
      - UPDATE
      resources:
      - pods
  validations:
  - expression: |
      !has(object.spec.initContainers) || object.spec.initContainers.all(ic,
        !has(ic.startupProbe) ||
        !has(ic.startupProbe.tcpSocket) ||
        !has(ic.startupProbe.tcpSocket.host) ||
        ic.startupProbe.tcpSocket.host == ""
      )
    message: |
      spec.initContainers[*].startupProbe.tcpSocket.host must be undefined or empty ("").

Save it as initcontainer-startupprobe-tcpsocket-host.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 ./initcontainer-startupprobe-tcpsocket-host.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 initcontainer-startupprobe-tcpsocket-host -r ./manifests

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

$ kubeapt validate --policy-name initcontainer-startupprobe-tcpsocket-host -A

Bundles

Source

View policy.yaml on GitHub →