Intro
Kubernetes has revolutionized container orchestration, but ensuring network security and access control within Kubernetes environments can be a complex endeavor. Even though network security is a key prerequisite to Kubernetes security overall, organizations often struggle with understanding and securing their Kubernetes networks, leaving them vulnerable to misconfigurations, vulnerabilities, and breaches.
How Does Kubernetes Handle Networking?
To alleviate these challenges, Kubernetes offers various mechanisms to enhance network security and access control. Let’s explore how Kubernetes handles network security and access control and discuss how the Kubernetes Security Operations Center (KSOC) can help organizations enhance their network security measures.
How Does Kubernetes Handle Network Security and Access Control?
Kubernetes handles network security by leveraging various features designed to protect communication between pods, clusters, and external entities.
Network Policies
Kubernetes Network Policies allow administrators to define rules that control inbound and outbound network traffic within a cluster. These policies can be applied to specific pods or namespaces, enabling fine-grained control over network access. By using kubectl get network policy command, administrators can list and manage network policies in their clusters to restrict communication between pods and namespaces based on specific criteria, such as IP addresses, labels, or namespaces.
Kubernetes Network Policy examples can be found in the Kubernetes documentation. These examples serve as useful references for implementing specific security requirements.
Kubernetes Ingress
Kubernetes ingress is handled using ingress controllers. Kubernetes ingress controllers manage inbound traffic coming into a cluster from external sources. By configuring ingress rules, organizations can control access to services and applications running within the cluster.
Kubernetes Egress
Conversely, egress is the opposite of ingress, representing any traffic that flows out from a service, pod, cluster, etc. to an outside endpoint. Many teams use an API Gateway or other kind of service in place of this direct outbound connection from Kubernetes. Some examples include the Cilium or Istio Egress Gateways. It is important to check the default egress policy because, unless you have changed it, the pod’s destination will default to the egress for the entire node.
Kubernetes Egress Example
If you were to start with your egress policies (preferably after ingress), your first step might be to isolate your pods for egress by applying a “default-deny-all” policy like the one below (isolating your pods for egress just means that it can effectively have an egress policy, otherwise all egress is open by default). This would effectively isolate all pods for egress.
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: default-deny-all-egress
spec:
podSelector: {}
egress:
- to:
ports:
- protocol: TCP
port: 53
- protocol: UDP
port: 53
policyTypes:
- Egress
Network Security Groups
In managed Kubernetes services like AKS (Azure Kubernetes Service), network security groups (NSGs) provide an additional layer of network security. AKS network security groups function as virtual firewalls, allowing organizations to define inbound and outbound network traffic rules at the subnet or pod level. By utilizing NSGs effectively, organizations can restrict network access and prevent unauthorized communication within Kubernetes clusters. Implementing Kubernetes network policy best practices is crucial to ensure a robust security posture within Kubernetes environments.
Kubernetes load balancing
Load balancing in Kubernetes networking is important in order to distribute traffic effectively to prevent denial of service issues or overloading that can service disruption. You can have internal load balancing that can be handled by the ClusterIP service, and is more straightforward. ClusterIP service is generally not something you would want to expose externally. You can also have external load balancing for traffic aiming outside the service, and this can be handled by Ingress (the alternative to get around the lack of flexibility in LoadBalancer, the Kubernetes default), NodePort (an extension of ClusterIP, useful for simple projects) or LoadBalancer (default, but complicated to configure). Load balancing is a critical, albeit potentially complicated, part of Kubernetes, especially for large, highly distributed environments.
Kubernetes EndpointSlices
To operate at scale, EndpointSlices are a useful capability. Unlike the traditional Kubernetes Endpoint resource, which stores all endpoints for a service in a single object, EndpointSlices split endpoint information and track multiple network endpoints within a cluster. Each EndpointSlice represents a subset of endpoints for a service, allowing for finer control and improved resource utilization.
Best Practices for Kubernetes Network Security
- Regularly Update and Patch Kubernetes Components: Stay up to date with the latest Kubernetes releases and security patches. Regularly update and patch Kubernetes components to mitigate known vulnerabilities and ensure a secure environment.
- Implement Network Security Tools: Leverage Kubernetes security tools such as Calico or Cilium. A Calico network policy or Cilium network policy can offer advanced network security capabilities like network policy enforcement and deep packet inspection.
- Limit Ingress and Egress Traffic: For both ingress and egress policies, it is recommended to control access to services and prevent unauthorized communication.
- Define and Enforce Network Policies: Create and enforce network policies that align with your organization's security requirements. Apply these policies to restrict communication between pods and namespaces based on specific criteria, such as IP addresses, labels, or namespaces.
How KSOC Can Help with Kubernetes Network Security
Kubernetes network components are one piece in the overall puzzle of Kubernetes risk; other important elements of risk include overly permissive RBAC policies, image CVEs, runtime alerts, public cloud misconfigurations, and manifest misconfigurations of Kubernetes itself. When viewed separately, the risk from each of these elements creates an enormous amount of noise. When viewed together, as part of a threat vector that shows combined risk, noise can be reduced by 98% and Kubernetes-targeted attacks can be identified as they happen versus after the fact in runtime. Contact us to see how you can triage your risk with threat vectors in the time it takes for your next coffee break.
Conclusion
Kubernetes revolutionized container orchestration, but network security and access control remain complex challenges. Kubernetes uses Network Policies, Ingress, Egress, and Network Security Groups for protection. Best practices include regular updates, security tools like Calico/Cilium, and defining/enforcing network policies. Through threat vectors, Kubernetes Security Operations Center (KSOC) addresses network security by combining it with other risks that would indicate broader risk. Integrating these strategies and leveraging KSOC enhances network security against Kubernetes-targeted attacks.
