C-0123 - Ensure that the admission control plugin AlwaysPullImages is set
Framework
cis-v1.23-t1.0.1
Severity
Medium
Description of the the issue
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.
Related resources
Pod
What does this control test
Always pull images.
How to check it manually
Run the following command on the Control Plane node:
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,...
Impact Statement
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 pre-loaded and do not have access to a registry to pull in-use images. This setting is not appropriate for clusters which use this configuration.
Default Value
By default, AlwaysPullImages
is not set.
Example
No example
Updated 9 days ago