cyberstrikeus CIS Kubernetes Benchmark v1.12.0 - Control 4.2.10
Description
Enable kubelet client certificate rotation.
Rationale
The --rotate-certificates setting causes the kubelet to rotate its client certificates by creating new CSRs as its existing credentials expire. This automated periodic rotation ensures that the there is no downtime 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.
Note: This feature also require the RotateKubeletClientCertificate feature gate to be enabled (which is the default since Kubernetes v1.7)
Impact
None
Audit Procedure
Step 1: Verify via process arguments
Run the following command on each node:
ps -ef | grep kubelet
Verify that RotateKubeletServerCertificate argument is not present, or is set to true.
If the RotateKubeletServerCertificate argument is not present, verify that if there is a Kubelet config file specified by --config, that file does not contain RotateKubeletServerCertificate: false.
Remediation
If using a Kubelet config file, edit the file to add the line rotateCertificates: true or remove it altogether to use the default value.
If using command line arguments, edit the kubelet service file /etc/kubernetes/kubelet.conf on each worker node and remove --rotate-certificates=false argument from the KUBELET_CERTIFICATE_ARGS variable or set --rotate-certificates=true.
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service
Default Value
By default, kubelet client certificate rotation is enabled.
References
- https://github.com/kubernetes/kubernetes/pull/41912
- https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/#kubelet-configuration
- https://kubernetes.io/docs/imported/release/notes/
- https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
CIS Controls
| Controls Version | Control | IG 1 | IG 2 | IG 3 |
|---|---|---|---|---|
| v8 | 3.10 Encrypt Sensitive Data in TransitEncrypt 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 TransitEncrypt all sensitive information in transit. | ● | ● |
Profile Applicability
- Level 1 - Worker Node
Assessment Status
Automated