cis-oke-v180-3-2-3

name	cis-oke-v180-3.2.3
description	Ensure that the --client-ca-file argument is set as appropriate (Automated)
category	cis-oke
version	1.8.0
author	cyberstrike-official
tags	["cis","oke","kubernetes","oci","worker-node","kubelet"]
cis_id	3.2.3
cis_benchmark	CIS Oracle Cloud Infrastructure Container Engine for Kubernetes (OKE) Benchmark v1.8.0
tech_stack	["kubernetes","oci","oke"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS OKE Benchmark v1.8.0 - Control 3.2.3

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

Audit Method 1

If using a Kubelet configuration file, check that there is an entry for --client-ca-file set to the location of the client certificate authority file.

First, SSH to the relevant node.

Run the following command on each node to find the appropriate Kubelet config file:

find / -name kubelet.service

The output of the above command should return the file and location /etc/systemd/system/kublet.service which is the location of the Kubelet service config file.

Open the Kubelet service config file:

sudo more etc/systemd/system/kubelet.service

Verify that the --client-ca-file argument exists and is set to the location of the client certificate authority file.

Audit Method 2

If using the api configz endpoint consider searching for the status of authentication..x509":("clientCAFile":"/etc/kubernetes/ca.crt by extracting the live configuration from the nodes running kubelet.

Set the local proxy port and the following variables and provide proxy port number and node name:

kubectl proxy --port=8001 &

export HOSTNAME_PORT=localhost:8001 (example host and port number)
export NODE_NAME=10.0.10.4 (example node name from "kubectl get nodes")

curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"

Remediation