Details

Kubelet is the primary agent on each node. The API server communicates with each kubelet to perform tasks such as starting/stopping pods. By default, kubelets allow all authenticated requests, even anonymous ones, without requiring any authorization checks from the API server. This default behavior bypasses any authorization controls put in place to limit what users may perform within the Kubernetes cluster. To change this behavior, the default setting of AlwaysAllow for the authorization mode must be set to ‘Webhook’.

Solution

Edit the Kubernetes Kubelet file in the/etc/sysconfig/ directory on the Kubernetes Master and Worker nodes.

Set the argument –authorization-mode to ‘Webhook’.

Restart each kubelet service after the change is made using the command:
service kubelet restart

Supportive Information

The following resource is also helpful.

• https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Kubernetes_V1R4_STIG.zip

This security hardening control applies to the following category of controls within NIST 800-53: Access Control.This control applies to the following type of system Unix.

References

• 800-53|AC-3
• CAT|I
• CCI|CCI-000213
• Rule-ID|SV-242392r712532_rule
• STIG-ID|CNTR-K8-000380
• Vuln-ID|V-242392

Source

• Tenable.com/audits