| name | cis-k8s-v1120-1.2.5 |
| description | Ensure that the --kubelet-certificate-authority argument is set as appropriate (Automated) |
| category | cis-k8s |
| version | 1.12.0 |
| author | cyberstrike-official |
| tags | ["cis","kubernetes","control-plane","api-server","authentication","kubelet","tls","certificate-authority"] |
| cis_id | 1.2.5 |
| cis_benchmark | CIS Kubernetes Benchmark v1.12.0 |
| tech_stack | ["kubernetes"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
1.2.5 Ensure that the --kubelet-certificate-authority argument is set as appropriate (Automated)
Profile Applicability
Description
Verify kubelet's certificate before establishing connection.
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.
Impact
You require TLS to be configured on apiserver as well as kubelets.
Audit
Run the following command on the Control Plane node:
ps -ef | grep kube-apiserver
Verify that the --kubelet-certificate-authority argument exists and is set as appropriate.
Alternative Audit
kubectl get pod -nkube-system -lcomponent=kube-apiserver -o=jsonpath='{range .items[]}{.spec.containers[].command} {"\n"}{end}' | grep '--kubelet-certificate-Authority' | grep -i false
If the exit code is '1', then the control isn't present / failed
Remediation
Follow the Kubernetes documentation and setup the TLS connection between the apiserver and kubelets. Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the Control Plane node and set the --kubelet-certificate-authority parameter to the path to the cert file for the certificate authority.
--kubelet-certificate-authority=<ca-string>
Default Value
By default, --kubelet-certificate-authority argument is not set.
References
- https://kubernetes.io/docs/admin/kube-apiserver/
- https://kubernetes.io/docs/admin/kubelet-authentication-authorization/
- https://kubernetes.io/docs/concepts/cluster-administration/master-node-communication/#apiserver---kubelet
CIS Controls
