Cis Oke V180 3.2.10

---
name: cis-oke-v180-3.2.10
description: "Ensure that the --rotate-server-certificates argument is set to true (Automated)"
category: cis-oke
version: "1.8.0"
author: cyberstrike-official
tags: [cis, oke, kubernetes, oci, worker-node, kubelet]
cis_id: "3.2.10"
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 3.2.10

## Profile Applicability

- **Level:** 1

## Description

Enable kubelet server certificate rotation.

## Rationale

`--rotate-server-certificates` causes the kubelet to both request a serving certificate after bootstrapping its client credentials and rotate the certificate as its existing credentials expire. This automated periodic rotation ensures that the there are no downtimes due to expired certificates and thus addressing availability in the CIA security triad.

Note: This recommendation only applies if you let kubelets get their certificates from the API server. In case your kubelet certificates come from an outside authority/tool (e.g. Vault) then you need to take care of rotation yourself.

## Impact

None

## Audit Procedure

### Audit Method 1

If using a Kubelet configuration file, check that there is an entry for `--rotate-server-certificates` is set to `true`.

First, SSH to the relevant node.

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

```bash
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:

```bash
sudo more etc/systemd/system/kubelet.service
```

Verify that the `--rotate-server-certificates=true`.

### Audit Method 2

If using the api configz endpoint consider searching for the status of `--rotate-server-certificates` 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:

```bash
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

### Remediation Method 1

If modifying the Kubelet service config file, edit the kubelet.service file `/etc/systemd/system/kubelet.service` and set the below parameter:

```
--rotate-server-certificates=true
```

### Remediation Method 2

If using the api configz endpoint consider searching for the status of `--rotate-server-certificates` by extracting the live configuration from the nodes running kubelet.

See detailed step-by-step configmap procedures in [Reconfigure a Node's Kubelet in a Live Cluster](https://kubernetes.io/docs/tasks/administer-cluster/reconfigure-kubelet/), and then rerun the curl statement from audit process to check for kubelet configuration changes.

```bash
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"
```

**For all remediations:** Based on your system, restart the `kubelet` service and check status:

```bash
systemctl daemon-reload
systemctl restart kubelet.service
systemctl status kubelet -l
```

## Default Value

See the OKE documentation for the default value.

## References

1. https://github.com/kubernetes/kubernetes/pull/45059
2. https://kubernetes.io/docs/admin/kubelet-tls-bootstrapping/#kubelet-configuration
3. https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Concepts/contengoverview.htm
4. https://kubernetes.io/docs/reference/access-authn-authz/kubelet-tls-bootstrapping/#certificate-rotation

## 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 |      | \*   | \*   |

## MITRE ATT&CK Mappings

| Techniques / Sub-techniques | Tactics | Mitigations |
| --------------------------- | ------- | ----------- |
| T1552                       | TA0006  | M1022       |

## Profile

**Level 1** (Automated)