cis-gke-v170-3-2-9

name	cis-gke-v170-3.2.9
description	Ensure that the RotateKubeletServerCertificate argument is set to true (Automated)
category	cis-gke
version	1.7.0
author	cyberstrike-official
tags	["cis","gke","kubernetes","gcp","kubelet","authentication","authorization","tls","event-capture","certificate-rotation"]
cis_id	3.2.9
cis_benchmark	CIS Google Kubernetes Engine (GKE) Benchmark v1.7.0
tech_stack	["kubernetes","gcp","gke"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

3.2.9 Ensure that the RotateKubeletServerCertificate argument is set to true (Automated)

Profile Applicability

• Level 1

Description

Enable kubelet server certificate rotation.

Rationale

RotateKubeletServerCertificate 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 (Confidentiality, Integrity, and Availability) 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 implement rotation yourself.

Impact

None

Audit

Audit Method 1:

First, SSH to each node.

Run the following command to find the Kubelet process:

ps -ef | grep kubelet

If the output of the command above includes the --rotate-kubelet-server-certificate executable argument verify that it is set to true.

If the process does not have the --rotate-kubelet-server-certificate executable argument then check the Kubelet config file. The output of the above command should return something similar to --config /etc/kubernetes/kubelet-config.yaml which is the location of the Kubelet config file.

Open the Kubelet config file:

cat /etc/kubernetes/kubelet-config.yaml

Verify that RotateKubeletServerCertificate argument exists in the featureGates section and is set to true.

Audit Method 2:

If using the api configz endpoint consider searching for the status of "RotateKubeletServerCertificate":true 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;

HOSTNAME_PORT="localhost-and-port-number"
NODE_NAME="The-Name-Of-Node-To-Extract-Configuration" from the output of "kubectl get nodes"

kubectl proxy --port=8001 &

export HOSTNAME_PORT=localhost:8001 (example host and port number)
 NODE_NAME=gke-cluster-1-pool1-5e572947-r2hg (example node name from )

curl -sSL