cis-ocp-v160-4-2-4

name	cis-ocp-v160-4.2.4
description	Ensure that the --client-ca-file argument is set as appropriate (Automated)
category	cis-openshift
version	1.6.0
author	cyberstrike-official
tags	["cis","openshift","kubernetes","redhat","worker-nodes","kubelet"]
cis_id	4.2.4
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 4.2.4

Profile Applicability

• Level: 1

Description

Enable Kubelet authentication using certificates.

Rationale

The connections from the apiserver to the kubelet are used for fetching logs for pods, attaching (through kubectl) to running pods, and using the kubelet's port-forwarding functionality. These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's serving certificate, which makes the connection subject to man-in-the-middle attacks, and unsafe to run over untrusted and/or public networks. Enabling Kubelet certificate authentication ensures that the apiserver could authenticate the Kubelet before submitting any requests.

Impact

You require TLS to be configured on apiserver as well as kubelets.

Audit Procedure

OpenShift provides integrated management of certificates for internal cluster components. OpenShift 4 includes multiple CAs providing independent chains of trust, which ensure that a platform CA will never accidentally sign a certificate that can be used for the wrong purpose, increasing the security posture of the cluster. You can verify the client CA file with the following command:

for node in $(oc get nodes -ojsonpath='{.items[*].metadata.name}'); do
oc get --raw /api/v1/nodes/$node/proxy/configz | jq '.kubeletconfig.authentication.x509.clientCAFile'
done

Verify all the nodes are using /etc/kubernetes/kubelet-ca.crt as the clientCAFile value.

Remediation

None. Changing the clientCAFile value is unsupported.

Default Value

By default, the clientCAFile is set to /etc/kubernetes/kubelet-ca.crt.

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