Control: 5.2.6 Minimize the admission of root containers
Description
Do not generally permit containers to be run as the root user.
Containers may run as any Linux user. Containers which run as the root user, whilst constrained by Container Runtime security features still have a escalated likelihood of container breakout.
Ideally, all containers should run as a defined non-UID 0 user.
There should be at least one PodSecurityPolicy (PSP) defined which does not permit root users in a container.
If you need to run root containers, this should be defined in a separate PSP and you should carefully check RBAC controls to ensure that only limited service accounts and users are given permission to access that PSP.
Remediation
Create a PSP as described in the Kubernetes documentation, ensuring that the .spec.runAsUser.rule is set to either MustRunAsNonRoot or MustRunAs with the range of UIDs not including 0.
References
Usage
Run the control in your terminal:
powerpipe control run kubernetes_compliance.control.cis_kube_v120_v100_5_2_6Snapshot and share results via Turbot Pipes:
powerpipe loginpowerpipe control run kubernetes_compliance.control.cis_kube_v120_v100_5_2_6 --shareSQL
This control uses a named query:
select coalesce(uid, concat(path, ':', start_line)) as resource, case when run_as_user ->> 'rule' = 'MustRunAsNonRoot' then 'ok' else 'alarm' end as status, case when run_as_user ->> 'rule' = 'MustRunAsNonRoot' then 'Pod security policy ' || name || ' restrict containers to run as non-root user.' else 'Pod security policy ' || name || ' does not restrict containers to run as non-root user.' end as reason , coalesce(context_name, '') as context_name, source_type, coalesce(path || ':' || start_line || '-' || end_line, '') as pathfrom kubernetes_pod_security_policy;