# Cis K8S V1120 1.2.25

> Ensure that the --client-ca-file argument is set as appropriate (Automated)

- Skill: `cyberstrikeus/cis-k8s-v1120-1-2-25` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-k8s-v1120-1-2-25`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-k8s-v1120-1-2-25/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-k8s-v1120-1-2-25

---


# 1.2.25 Ensure that the --client-ca-file argument is set as appropriate (Automated)

## Profile Applicability

- Level 1 - Master Node

## Description

Setup TLS connection on the API server.

## Rationale

API server communication contains sensitive parameters that should remain encrypted in transit. Configure the API server to serve only HTTPS traffic. If `--client-ca-file` argument is set, any request presenting a client certificate signed by one of the authorities in the `client-ca-file` is authenticated with an identity corresponding to the CommonName of the client certificate.

## Impact

TLS and client certificate authentication must be configured for your Kubernetes cluster deployment.

## Audit

Run the following command on the Control Plane node:

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

Verify that the `--client-ca-file` argument exists and it is set as appropriate.

## Remediation

Follow the Kubernetes documentation and set up the TLS connection on the apiserver. Then, edit the API server pod specification file `/etc/kubernetes/manifests/kube-apiserver.yaml` on the master node and set the client certificate authority file.

```
--client-ca-file=<path/to/client-ca-file>
```

## Default Value

By default, `--client-ca-file` argument is not set.

## References

1. [https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/](https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/)
2. [https://github.com/kelseyhightower/docker-kubernetes-tls-guide](https://github.com/kelseyhightower/docker-kubernetes-tls-guide)

## CIS Controls

| Controls Version | Control                                           | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------------------------------- | ---- | ---- | ---- |
| v8               | 3.10 Encrypt Sensitive Data in Transit            |      | \*   | \*   |
| v7               | 14.4 Encrypt All Sensitive Information in Transit |      | \*   | \*   |