CIS-2.7 - Ensure that a unique Certificate Authority is used for etcd

Ensure that a unique Certificate Authority is used for etcd

Framework

CIS

Severity

High

Description of the the issue

etcd is a highly available key-value store used by Kubernetes deployments for persistent storage of all of its REST API objects. Its access should be restricted to specifically designated clients and peers only.

Authentication to etcd is based on whether the certificate presented was issued by a trusted certificate authority. There is no checking of certificate attributes such as common name or subject alternative name. As such, if any attackers were able to gain access to any certificate issued by the trusted certificate authority, they would be able to gain full access to the etcd database.

Related resources

Pod

What does this control test

Use a different certificate authority for etcd from the one used for Kubernetes.

How to check it manually

Review the CA used by the etcd environment and ensure that it does not match the CA certificate file used for the management of the overall Kubernetes cluster.

Run the following command on the master node:

ps -ef | grep etcd

Note the file referenced by the --trusted-ca-file argument.

Run the following command on the master node:

ps -ef | grep apiserver

Verify that the file referenced by the --client-ca-file for apiserver is different from the --trusted-ca-file used by etcd.

Remediation

Follow the etcd documentation and create a dedicated certificate authority setup for the etcd service.

Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master node and set the below parameter.

--trusted-ca-file=</path/to/ca-file>

Impact Statement

Additional management of the certificates and keys for the dedicated certificate authority will be required.

Default Value

By default, no etcd certificate is created and used.

Example

No example