Cis K8s V1110 1.2.4

---
name: cis-k8s-v1110-1.2.4
description: "Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate (Automated)"
category: cis-k8s
version: "1.11.0"
author: cyberstrike-official
tags: [cis, kubernetes, control-plane, api-server, kubelet-client-certificate, kubelet-client-key, tls, authentication]
cis_id: "1.2.4"
cis_benchmark: "CIS Kubernetes Benchmark v1.11.0"
tech_stack: [kubernetes]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# 1.2.4 Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate (Automated)

## Profile Applicability

- Level 1 - Master Node

## Description

Enable certificate based kubelet authentication.

## Rationale

The apiserver, by default, does not authenticate itself to the kubelet's HTTPS endpoints. The requests from the apiserver are treated anonymously. You should set up certificate-based kubelet authentication to ensure that the apiserver authenticates itself to kubelets when submitting requests.

## Impact

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

## Audit

Run the following command on the Control Plane node:

```bash
ps -ef | grep kube-apiserver
```

Verify that the `--kubelet-client-certificate` and `--kubelet-client-key` arguments exist and they are set as appropriate.

Alternative Audit:

```bash
kubectl get pod -nkube-system -lcomponent=kube-apiserver -o=jsonpath='{range .items[]}{.spec.containers[].command} {"\n"}{end}' | grep '--kubelet-client-certificate' | grep -i false
```

If the exit code is '1', then the control isn't present / failed.

## Remediation

Follow the Kubernetes documentation and set up the TLS connection between the apiserver and kubelets. Then, edit API server pod specification file `/etc/kubernetes/manifests/kube-apiserver.yaml` on the Control Plane node and set the kubelet client certificate and key parameters as below.

```
--kubelet-client-certificate=<path/to/client-certificate-file>
--kubelet-client-key=<path/to/client-key-file>
```

## Default Value

By default, certificate-based kubelet authentication is not set.

## References

1. https://kubernetes.io/docs/admin/kube-apiserver/
2. https://kubernetes.io/docs/admin/kubelet-authentication-authorization/
3. https://kubernetes.io/docs/concepts/cluster-administration/master-node-communication/#apiserver---kubelet

## CIS Controls

| Controls Version | Control                                                                       | IG 1 | IG 2 | IG 3 |
| ---------------- | ----------------------------------------------------------------------------- | ---- | ---- | ---- |
| v8               | 16.11 Leverage Vetted Modules or Services for Application Security Components |      | \*   | \*   |
| v7               | 9 Limitation and Control of Network Ports, Protocols, and Services            |      |      |      |