The API server should verify the kubelet's certificate before connecting
Set up the kubernetes integration.
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 kubelets port-forwarding functionality. These connections terminate at the kubelets HTTPS endpoint. By default, the apiserver does not verify the kubelets serving certificate, which makes the connection subject to man-in-the-middle attacks, and unsafe to run over untrusted and/or public networks.
Audit
Run the following command on the master node:
ps -ef | grep kube-apiserver
Verify that the --kubelet-certificate-authority argument exists and is set as appropriate.
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 master node and set the --kubelet-certificate-authority parameter to the path to the cert file for the certificate authority.
--kubelet-certificate-authority=<ca-string>
Impact
You require TLS to be configured on apiserver as well as kubelets.
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
Version 6.3.4 Use Only Secure Channels For Remote System Administration - Perform all remote administration of servers, workstation, network devices, and similar equipment over secure channels. Protocols such as telnet, VNC, RDP, or others that do not actively support strong encryption should only be used if they are performed over a secondary encryption channel, such as SSL, TLS or IPSEC.
Version 7.4.5 Use Multifactor Authentication For All Administrative Access - Use multi-factor authentication and encrypted channels for all administrative account access.
