Amazon EKS
TMA-EKS-3.2.8
Ensure serverTLSBootstrap and RotateKubeletServerCertificate are enabled
Description
In EKS, these settings are about the kubelet’s serving certificate, which is the certificate the kubelet presents from its HTTPS endpoint to callers. serverTLSBootstrap controls whether the kubelet uses the Kubernetes certificates API to bootstrap that serving certificate, while RotateKubeletServerCertificate keeps the related rotation support enabled when feature gates are managed. Reads every node's effective kubelet configuration through the API server (kubectl get --raw /api/v1/nodes/<node>/proxy/configz); requires kubectl with nodes/proxy access. RotateKubeletServerCertificate must not be false (it defaults to true).
How it is checked
Audit method: Shell command
nodes=$(kubectl get nodes -o jsonpath='{range .items[*]}{.metadata.name}{"\n"}{end}') || exit 1
[ -n "$nodes" ] || exit 1
ok=1
for n in $nodes; do
c=$(kubectl get --raw "/api/v1/nodes/$n/proxy/configz") || exit 1
if ! { printf '%s' "$c" | grep -Eq '"serverTLSBootstrap":true' && ! printf '%s' "$c" | grep -Eq '"RotateKubeletServerCertificate":false'; }; then echo "noncompliant: $n"; ok=0; fi
done
if [ "$ok" -eq 1 ]; then echo compliant; fi- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
If the audit shows serverTLSBootstrap is false, the kubelet is not entering the Kubernetes certificates API workflow for its serving certificate and the node should be treated as noncompliant. If RotateKubeletServerCertificate is false, or becomes unset because custom feature gates were supplied without re-including it, the related server certificate rotation support is not being preserved. If either field is missing, first confirm the configz response is complete, because Kubernetes identifies that endpoint as the view of the kubelet’s final actuated configuration. In EKS, remediation should be performed through the supported node provisioning or node update workflow, not by directly editing the kubelet config file on the host, because AWS applies durable node behavior through launch templates, merged user data, and managed node replacement workflows.
Properties
- Operating systems
- Any
- Tags
- eksworker-nodekubelet
- Reference
- CIS Amazon Elastic Kubernetes Service (EKS) Benchmark v2.0.0 - 3.2.8 Ensure serverTLSBootstrap and RotateKubeletServerCertificate are enabled
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
tmaegis scan --target eks