Classification:

compliance

Framework:

cis-kubernetes

Control:

1.2.28

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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.

Remediation

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

1. https://kubernetes.io/docs/admin/kube-apiserver/
2. 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