Minimize the admission of root containers
Set up the kubernetes integration.
Description
Do not generally permit containers to be run as the root user.
Rationale
Containers may run as any Linux user. Containers that run as the root user, while 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.
Audit
Get the set of PSPs with the following command: kubectl get psp
For each PSP, check whether running containers as root is enabled: kubectl get psp <name> -o=jsonpath='{.spec.runAsUser.rule}'
Verify that there is at least one PSP which returns MustRunAsNonRoot or MustRunAs with the range of UIDs not including 0.
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.
Impact
Pods with containers which run as the root user will not be permitted.
Default value
By default, PodSecurityPolicies are not defined.
References
- https://kubernetes.io/docs/concepts/policy/pod-security-policy/#enabling-pod-security-policies
CIS controls
Version 6 5.1 Minimize And Sparingly Use Administrative Privileges - Minimize administrative privileges and only use administrative accounts when they are required. Implement focused auditing on the use of administrative privileged functions and monitor for anomalous behavior.
