Kubernetes must have a Pod Security Admission control file configured.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-254800	CNTR-K8-002011	SV-254800r864040_rule		High

Description
An admission controller intercepts and processes requests to the Kubernetes API prior to persistence of the object, but after the request is authenticated and authorized. Kubernetes (> v1.23)offers a built-in Pod Security admission controller to enforce the Pod Security Standards. Pod security restrictions are applied at the namespace level when pods are created. The Kubernetes Pod Security Standards define different isolation levels for Pods. These standards let you define how you want to restrict the behavior of pods in a clear, consistent fashion.

Description

An admission controller intercepts and processes requests to the Kubernetes API prior to persistence of the object, but after the request is authenticated and authorized. Kubernetes (> v1.23)offers a built-in Pod Security admission controller to enforce the Pod Security Standards. Pod security restrictions are applied at the namespace level when pods are created. The Kubernetes Pod Security Standards define different isolation levels for Pods. These standards let you define how you want to restrict the behavior of pods in a clear, consistent fashion.

STIG	Date
Kubernetes Security Technical Implementation Guide	2022-09-13

Details

Check Text ( C-58411r863727_chk )
Change to the /etc/kubernetes/manifests directory on the Kubernetes Control Plane. Run the command: "grep -i admission-control-config-file *" If the setting "admission-control-config-file" is not configured in the Kubernetes API Server manifest file, this is a finding. Inspect the .yaml file defined by the --admission-control-config-file. Verify PodSecurity is properly configured. If least privilege is not represented, this is a finding.

Check Text ( C-58411r863727_chk )

Change to the /etc/kubernetes/manifests directory on the Kubernetes Control Plane. Run the command:

"grep -i admission-control-config-file *"

If the setting "admission-control-config-file" is not configured in the Kubernetes API Server manifest file, this is a finding.

Inspect the .yaml file defined by the --admission-control-config-file. Verify PodSecurity is properly configured.
If least privilege is not represented, this is a finding.

Fix Text (F-58357r863728_fix)
Modify the file /etc/kubernetes/manifests/kube-apiserver.yaml and add the flag --admission-control-config-file (with a valid path for the file) to the apiserver configuration. Create an admission controller config file: Example File: ```yaml apiVersion: apiserver.config.k8s.io/v1 kind: AdmissionConfiguration plugins: - name: PodSecurity configuration: apiVersion: pod-security.admission.config.k8s.io/v1beta1 kind: PodSecurityConfiguration # Defaults applied when a mode label is not set. defaults: enforce: "privileged" enforce-version: "latest" exemptions: # Don't forget to exempt namespaces or users that are responsible for deploying # cluster components, because they need to run privileged containers usernames: ["admin"] namespaces: ["kube-system"] See For More Details: Migrate from PSP to PSA: https://kubernetes.io/docs/tasks/configure-pod-container/migrate-from-psp/ Best Practice: https://kubernetes.io/docs/concepts/security/pod-security-policy/#recommended-practice

Fix Text (F-58357r863728_fix)

Modify the file /etc/kubernetes/manifests/kube-apiserver.yaml and add the flag --admission-control-config-file (with a valid path for the file) to the apiserver configuration.

Create an admission controller config file:
Example File:
```yaml
apiVersion: apiserver.config.k8s.io/v1
kind: AdmissionConfiguration
plugins:
- name: PodSecurity
configuration:
apiVersion: pod-security.admission.config.k8s.io/v1beta1
kind: PodSecurityConfiguration
# Defaults applied when a mode label is not set.
defaults:
enforce: "privileged"
enforce-version: "latest"
exemptions:
# Don't forget to exempt namespaces or users that are responsible for deploying
# cluster components, because they need to run privileged containers
usernames: ["admin"]
namespaces: ["kube-system"]

See For More Details:
Migrate from PSP to PSA:
https://kubernetes.io/docs/tasks/configure-pod-container/migrate-from-psp/

Best Practice: https://kubernetes.io/docs/concepts/security/pod-security-policy/#recommended-practice