The API server should explicitly set a service account public key file
Set up the kubernetes integration.
Description
Explicitly set a service account public key file for service accounts on the apiserver.
Rationale
By default, if no –service-account-key-file is specified to the apiserver, it uses the private key from the TLS serving certificate to verify service account tokens. To ensure that the keys for service account tokens could be rotated as needed, a separate public/private key pair should be used for signing service account tokens. Hence, the public key should be specified to the apiserver with –service-account-key-file.
Audit
Run the following command on the master node:
ps -ef | grep kube-apiserver
Verify that the --service-account-key-file argument exists and is set as appropriate.
Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and set the --service-account-key-file parameter to the public key file for service accounts: --service-account-key-file=<filename>
Impact
The corresponding private key must be provided to the controller manager. You would need to securely maintain the key file and rotate the keys based on your organization’s key rotation policy.
Default value
By default, --service-account-key-file argument is not set.
References
- https://kubernetes.io/docs/admin/kube-apiserver/
- https://github.com/kubernetes/kubernetes/issues/24167
CIS controls
Version 6 3 Secure Configurations for Hardware and Software on Mobile Devices, Laptops, Workstations, and Servers
Version 7 5 Secure Configuration for Hardware and Software on Mobile Devices, Laptops, Workstations and Servers
