Profile applicability: Level 2
Use network policies to isolate traffic in the cluster network.
Running different applications on the same Kubernetes cluster creates a risk of one
compromised application attacking a neighboring application. Network segmentation
is important to ensure that containers can communicate only with those they are supposed
to. A network policy is a specification of how selections of pods are allowed to communicate
with each other and other network endpoints.
Network Policies are namespace scoped. When a network policy is introduced to a given
namespace, all traffic not allowed by the policy is denied. However, if there are
no network policies in a namespace all traffic will be allowed into and out of the
pods in that namespace.
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NoteBy default, network policies are not created.
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Impact
Once network policies are in use within a given namespace, traffic not explicitly
allowed by a network policy will be denied. As such it is important to ensure that,
when introducing network policies, legitimate traffic is not blocked.
Audit
Run the below commands and review the
NetworkPolicy objects created in the cluster.Command line statement to show namespaces with 1 or more Network Policies set:
kubectl get ns -o jsonpath='{range .items[*]}{.metadata.name}{"\n"}{end}' | while read ns; do count=$(kubectl get networkpolicy -n "$ns" --no-headers 2>/dev/null | wc -l | tr -d ' ') if [ "$count" -gt 0 ]; then echo -e "${ns}\t${count}" fi done
Command line statement to show namespaces with 0 Network Policies set:
for ns in $(kubectl get ns -o jsonpath='{.items[*].metadata.name}'); do count=$(kubectl get networkpolicy -n "$ns" --no-headers 2>/dev/null | wc -l | tr -d ' ') if [ "$count" -eq 0 ]; then echo -e "${ns}\t${count}" fi done
Remediation
Follow the documentation and create
NetworkPolicy objects as needed. See: GKE documentation for more information.