The API server should validate the service account token in etcd
Set up the kubernetes integration.
Description
Validate service account before validating token.
Rationale
If –service-account-lookup is not enabled, the apiserver only verifies that the authentication token is valid, and does not validate that the service account token mentioned in the request is actually present in etcd. This allows using a service account token even after the corresponding service account is deleted. This is an example of time of check to time of use security issue.
Audit
Run the following command on the master node:
ps -ef | grep kube-apiserver
Verify that if the --service-account-lookup argument exists it is set to true.
Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and set the below parameter. --service-account-lookup=true Alternatively, you can delete the --service-account-lookup parameter from this file so that the default takes effect.
Impact
None
Default value
By default, --service-account-lookup argument is set to true.
References
- https://kubernetes.io/docs/admin/kube-apiserver/
- https://github.com/kubernetes/kubernetes/issues/24167
- https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use
CIS controls
Version 6 16 Account Monitoring and Control Account Monitoring and Control Version 7 16 Account Monitoring and Control Account Monitoring and Control
