| name | cis-k8s-v1110-1.2.21 |
| description | Ensure that the --service-account-lookup argument is set to true (Automated) |
| category | cis-k8s |
| version | 1.11.0 |
| author | cyberstrike-official |
| tags | ["cis","kubernetes","control-plane","api-server","service-account-lookup","authentication","token-validation"] |
| cis_id | 1.2.21 |
| cis_benchmark | CIS Kubernetes Benchmark v1.11.0 |
| tech_stack | ["kubernetes"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
1.2.21 Ensure that the --service-account-lookup argument is set to true (Automated)
Profile Applicability
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.
Impact
None
Audit
Run the following command on the Control Plane 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 Control Plane 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.
Default Value
By default, --service-account-lookup argument is set to true.
References
- https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/
- https://github.com/kubernetes/kubernetes/issues/24167
- https://en.wikipedia.org/wiki/Time-of-check_to_time-of-use
CIS Controls
| Controls Version | Control | IG 1 | IG 2 | IG 3 |
|---|
| v8 | 3.3 Configure Data Access Control Lists | * | * | * |
| v7 | 16 Account Monitoring and Control | | | |
