Admission control plugin AlwaysPullImages is set
Set up the kubernetes integration.
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 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.
Audit
Run the following command on the master node:
ps -ef | grep kube-apiserver
Verify the --enable-admission-plugins argument is set to a value that includes AlwaysPullImages.
Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and set the –enable-admission-plugins parameter to include AlwaysPullImages. –enable-admission-plugins=…,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. 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.
References
- https://kubernetes.io/docs/admin/kube-apiserver/ 2. https://kubernetes.io/docs/admin/admission-controllers/#alwayspullimages
CIS controls
Version 6 14.4 Protect Information With Access Control Lists All information stored on systems shall be protected with file system, network share, claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Version 7 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities.
