Details
Always pull images.
Rationale:
Setting admission control policy to ‘AlwaysPullImages’ forces every new pod to pull the required images every time. In a multitenant cluster users can be assured that their private images can only be used by those who have the credentials to pull them. Without this admisssion control policy, once an image has been pulled to a node, any pod from any user can use it simply by knowing the images 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.
Solution
Edit the API server pod specification file ‘/etc/kubernetes/manifests/kube-apiserver.yaml’ on the master node and set the ‘–admission-control’ parameter to include ‘AlwaysPullImages’.
–admission-control=…,AlwaysPullImages,…
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.
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Access Control.This control applies to the following type of system Unix.