C-0202 - Minimize the admission of Windows HostProcess Containers

Framework

cis-v1.10.0

Severity

High

Description of the the issue

A Windows container making use of the hostProcess flag can interact with the underlying Windows cluster node. As per the Kubernetes documentation, this provides "privileged access" to the Windows node.

Where Windows containers are used inside a Kubernetes cluster, there should be at least one admission control policy which does not permit hostProcess Windows containers.

If you need to run Windows containers which require hostProcess, this should be defined in a separate policy and you should carefully check to ensure that only limited service accounts and users are given permission to use that policy.

Related resources

MutatingWebhookConfiguration, Namespace, ValidatingWebhookConfiguration

What does this control test

Do not generally permit Windows containers to be run with the hostProcess flag set to true.

How to check it manually

List the policies in use for each namespace in the cluster, ensure that each policy disallows the admission of hostProcess containers

Remediation

Add policies to each namespace in the cluster which has user workloads to restrict the admission of hostProcess containers.

Impact Statement

Pods defined with securityContext.windowsOptions.hostProcess: true will not be permitted unless they are run under a specific policy.

Default Value

By default, there are no restrictions on the creation of hostProcess containers.

Example

No example