Overview
Within Kubernetes, networks are an interesting beast. They become extremely muddled when one (CNI) utilizes OSI Layer 2-7 service mesh to handle not only network routing, network policies, load balancers, but also providing a container storage interface (CSI.) For simplicity sake, we will consider a simple network provider that only handles routing and network policies. Each provider will have their own gotchas, limitations, and hardening guides so please see their hardening documentation. By default, almost all network providers allow all traffic across all namespaces.
Common network providers will align to Kubernetes’ namespace model to construct and enforce network policies. These policies enable one to construct and enforce traffic within pods but also within and across namespaces. Beyond the traditional on-premise router, quotas and limits may be applied to enable one to request ports or load balancers. Like many enterprise routers, one may configure and enforce TLS connectivity.
Depending on which Ring, there exists multiple ports that may not need to be exposed to 0.0.0.0: 10250, 10255, 10256, 41949, etc…. Please restrict accordingly.
CIS Benchmark
5.3 Network Policies and CNI
5.3.1 Ensure that the CNI in use supports Network Policies (Manual)
246 5.3.2 Ensure that all Namespaces have Network Policies defined (Manual)