Cis Ocp V190 4.2.4

---
name: cis-ocp-v190-4.2.4
description: "Ensure that the --client-ca-file argument is set as appropriate (Automated)"
category: cis-openshift
version: "1.9.0"
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 v1.9.0"
tech_stack: [kubernetes, openshift, redhat]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# CIS Red Hat OpenShift Container Platform Benchmark v1.9.0 - 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:

```bash
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
3. https://github.com/openshift/cluster-kube-apiserver-operator/blob/release-4.5/bindata/v4.1.0/config/defaultconfig.yaml#L28-L29
4. https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
5. https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-authentication-authorization/

## CIS Controls

| Controls Version | Control                                    | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------------------------ | ---- | ---- | ---- |
| v8               | 3.11 Encrypt Sensitive Data at Rest        |      | \*   | \*   |
| v7               | 14.8 Encrypt Sensitive Information at Rest |      |      | \*   |

## MITRE ATT&CK Mappings

| Techniques / Sub-techniques | Tactics | Mitigations |
| --------------------------- | ------- | ----------- |

## Profile

**Level 1** (Automated)