C-0197 - Minimize the admission of containers with allowPrivilegeEscalation

Framework

cis-v1.23-t1.0.1

Severity

Medium

Description of the the issue

A container running with the allowPrivilegeEscalation flag set to true may have processes that can gain more privileges than their parent.

There should be at least one admission control policy defined which does not permit containers to allow privilege escalation. The option exists (and is defaulted to true) to permit setuid binaries to run.

If you have need to run containers which use setuid binaries or require privilege escalation, 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 containers to be run with the allowPrivilegeEscalation flag set to true. Allowing this right can lead to a process running a container getting more rights than it started with.

It's important to note that these rights are still constrained by the overall container sandbox, and this setting does not relate to the use of privileged containers.

How to check it manually

List the policies in use for each namespace in the cluster, ensure that each policy disallows the admission of containers which allow privilege escalation.

Remediation

Add policies to each namespace in the cluster which has user workloads to restrict the admission of conatiners with .spec.allowPrivilegeEscalationset to true.

Impact Statement

Pods defined with spec.allowPrivilegeEscalation: true will not be permitted unless they are run under a specific policy.

Default Value

By default, there are no restrictions on contained process ability to escalate privileges, within the context of the container.

Example

No example