Cis K8s V1110 1.2.11

---
name: cis-k8s-v1110-1.2.11
description: "Ensure that the admission control plugin AlwaysPullImages is set (Manual)"
category: cis-k8s
version: "1.11.0"
author: cyberstrike-official
tags: [cis, kubernetes, control-plane, api-server, admission-plugins, always-pull-images, image-security]
cis_id: "1.2.11"
cis_benchmark: "CIS Kubernetes Benchmark v1.11.0"
tech_stack: [kubernetes]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# 1.2.11 Ensure that the admission control plugin AlwaysPullImages is set (Manual)

## Profile Applicability

- Level 1 - Master Node

## Description

Always pull images.

## Rationale

Setting admission control policy to `AlwaysPullImages` forces every new pod to pull the required images every time. In a multi-tenant cluster users can be assured that their private images can only be used by those who have the credentials to pull them. Without this admission control policy, once an image has been pulled to a node, any pod from any user can use it simply by knowing the image's name, without any authorization check against the image ownership. When this plug-in is enabled, images are always pulled prior to starting containers, which means valid credentials are required.

## Impact

Credentials would be required to pull the private images every time. Also, in trusted environments, this might increases load on network, registry, and decreases speed.

This setting could impact offline or isolated clusters, which have images preloaded and do not have access to a registry to pull in-use images. This setting is not appropriate for clusters which use this configuration.

## Audit

Run the following command on the Control Plane node:

```bash
ps -ef | grep kube-apiserver
```

Verify that the `--enable-admission-plugins` argument is set to a value that includes `AlwaysPullImages`.

## Remediation

Edit the API server pod specification file `/etc/kubernetes/manifests/kube-apiserver.yaml` on the Control Plane node and set the `--enable-admission-plugins` parameter to include `AlwaysPullImages`.

```
--enable-admission-plugins=...,AlwaysPullImages,...
```

## Default Value

By default, `AlwaysPullImages` is not set.

## References

1. https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/
2. https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#alwayspullimages

## CIS Controls

| Controls Version | Control                                               | IG 1 | IG 2 | IG 3 |
| ---------------- | ----------------------------------------------------- | ---- | ---- | ---- |
| v8               | 3.3 Configure Data Access Control Lists               | \*   | \*   | \*   |
| v7               | 14.6 Protect Information through Access Control Lists | \*   | \*   | \*   |