Information
Explicitly set a service account public key file for service accounts on the federation apiserver.
Rationale:
By default, if no '--service-account-key-file' is specified to the federation apiserver, it uses the private key from the TLS serving certificate to verify the 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'.
Solution
Edit the deployment specs and set '--service-account-key-file' argument as appropriate.
kubectl edit deployments federation-apiserver-deployment --namespace=federation-system
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.