Classification:

compliance

Framework:

cis-kubernetes

Control:

1.2.27

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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.

Remediation

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

1. https://kubernetes.io/docs/admin/kube-apiserver/
2. https://github.com/kubernetes/kubernetes/issues/24167
3. 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