4.2.11 Verify that the RotateKubeletServerCertificate argument is set to true (Manual)
Profile Applicability
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 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
Ignore this check if serverTLSBootstrap is true in the kubelet config file or if the --rotate-server-certificates parameter is set on kubelet
Run the following command on each node:
ps -ef | grep kubelet
Verify that RotateKubeletServerCertificate argument exists and is set to true.
Remediation
Edit the kubelet service file /etc/kubernetes/kubelet.conf on each worker node and set the below parameter in KUBELET_CERTIFICATE_ARGS variable.
--feature-gates=RotateKubeletServerCertificate=true
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service
Default Value
By default, kubelet server certificate rotation is enabled.
References
- https://github.com/kubernetes/kubernetes/pull/45059
- https://kubernetes.io/docs/admin/kubelet-tls-bootstrapping/#kubelet-configuration
CIS Controls
| Controls Version | Control | IG 1 | IG 2 | IG 3 |
|---|
| v8 | 3.10 Encrypt Sensitive Data in Transit - Encrypt sensitive data in transit. Example implementations can include: Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). | | * | * |
| v7 | 14.4 Encrypt All Sensitive Information in Transit - Encrypt all sensitive information in transit. | | * | * |
