Minimize the admission of containers with the NET_RAW capability
Set up the kubernetes integration.
Description
Do not generally permit containers with the potentially dangerous NET_RAW capability.
Rationale
Containers run with a default set of capabilities as assigned by the container runtime. By default this can include potentially dangerous capabilities. With Docker as the container runtime, the NET_RAW capability is enabled, which may be misused by malicious containers. Ideally, all containers should drop this capability. There should be at least one PodSecurityPolicy (PSP) defined which prevents containers with the NET_RAW capability from launching. If you need to run containers with this capability, 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 NET_RAW is disabled: kubectl get psp <name> -o=jsonpath='{.spec.requiredDropCapabilities}'
Verify that there is at least one PSP which returns NET_RAW or ALL.
Create a PSP as described in the Kubernetes documentation, ensuring that the .spec.requiredDropCapabilities is set to include either NET_RAW or ALL.
Impact
Pods with containers which run with the NET_RAW capability 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
- https://www.nccgroup.trust/uk/our-research/abusing-privileged-and-unprivileged-linux-containers/
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.
