cis-ocp-v160-4-2-5

name	cis-ocp-v160-4.2.5
description	Verify that the read only port is not used or is set to 0 (Automated)
category	cis-openshift
version	1.6.0
author	cyberstrike-official
tags	["cis","openshift","kubernetes","redhat","worker-nodes","kubelet"]
cis_id	4.2.5
cis_benchmark	CIS Red Hat OpenShift Container Platform Benchmark v1.6.0
tech_stack	["kubernetes","openshift","redhat"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Red Hat OpenShift Container Platform Benchmark v1.6.0 - Control 4.2.5

Profile Applicability

• Level: 1

Description

Disable the read-only port.

Rationale

The Kubelet process provides a read-only API in addition to the main Kubelet API. Unauthenticated access is provided to this read-only API which could possibly retrieve potentially sensitive information about the cluster.

Impact

Removal of the read-only port will require that any service which made use of it will need to be re-configured to use the main Kubelet API.

Audit Procedure

In OpenShift 4, the kubelet is managed by the Machine Config Operator. The kubelet config file is found at /etc/kubernetes/kubelet.conf. OpenShift disables the read-only port (10255) on all nodes by setting the read-only-port kubelet flag to 0 by default in OpenShift 4.6 and above. Run the following command to verify the kubelet-read-only-port is set to 0 for the Kubernetes API server configuration map.

oc -n openshift-kube-apiserver get cm config -o json | jq -r '.data."config.yaml"' | yq '.apiServerArguments."kubelet-read-only-port"'

Verify the output is a list that contains 0, like the following:

["0"]

Remediation

In earlier versions of OpenShift 4, the read-only-port argument is not used. Follow the instructions in the documentation to create a kubeletconfig CRD and set the kubelet-read-only-port is set to 0.

Default Value

By default, in OpenShift 4.5 and earlier, the --read-only-port is not used. In OpenShift 4.6 and above, the kubelet-read-only-port is set to 0.

References

1. https://docs.openshift.com/container-platform/latest/architecture/control-plane.html#understanding-machine-config-operator_control-plane
2. https://docs.openshift.com/container-platform/latest/post_installation_configuration/machine-configuration-tasks.html#create-a-kubeletconfig-crd-to-edit-kubelet-parameters_post-install-machine-configuration-tasks