Implementing Security Best Practices in Kubernetes Clusters on EKS/GKE

Jan 315 min read

Overview
Cluster Hardening
Network Security
Authentication & Authorization
Securing Container Images
Runtime Security
Data Protection
Logging & Monitoring
Continuous Integration and Continuous Deployment (CICD)
Conclusion
References

Illustration showing Kubernetes architecture with a focus on security best practices in EKS and GKE clusters, including RBAC, network policies, and container security.

Overview

Kubernetes has become the standard for container orchestration, offering scalability, flexibility, and reliability for modern applications. However, securing Kubernetes clusters is essential to mitigate potential risks such as unauthorized access, data breaches, and resource misuse. Both Amazon EKS (Elastic Kubernetes Service) and Google GKE (Google Kubernetes Engine) provide managed Kubernetes services but ensuring that these clusters are secure requires a proactive approach with best practices in mind.

In this blog, we'll cover key security best practices for Kubernetes clusters on EKS and GKE. We'll explore essential components like network policies, access control, auditing, and container image security, supported by use cases and examples.

Cluster Hardening

Keep Kubernetes Updated

Kubernetes, like any other software, is subject to vulnerabilities that are patched in each release. Therefore, always use the latest stable version of Kubernetes to ensure that you benefit from security fixes and improvements.

EKS: You can easily upgrade your cluster using eksctl or the AWS Management Console, and AWS automatically updates the control plane for you.
GKE: GKE offers a managed Kubernetes control plane that you can upgrade via the Google Cloud Console or gcloud CLI.

Additionally, enable Audit Logging on both EKS and GKE to track API server activities and detect any suspicious behavior early.

Control Plane Security

The Kubernetes control plane manages the entire cluster, and securing access to it is crucial.

Private API Endpoints: Both EKS and GKE offer options to restrict API access to only trusted IPs by enabling private endpoints for the Kubernetes API server.
RBAC (Role-Based Access Control): Configuring RBAC ensures that users and service accounts have only the permissions they need, adhering to the principle of least privilege. Define roles and role bindings to control access at a fine-grained level.

Network Security

Network Policies

Network policies define how pods can communicate with each other and with external services. By default, pods can communicate freely, which could lead to potential security risks.

EKS/GKE: Both services support Kubernetes Network Policies, allowing you to define inbound and outbound traffic rules at the pod level. Restricting traffic between different pods and services minimizes the attack surface.

Example Network Policy: Deny all traffic except from a specific namespace.

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-from-namespace
spec:
  podSelector: {}
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              name: allowed-namespace

Isolate Sensitive Resources

For sensitive workloads like databases or identity services, it's a good practice to segregate them into different namespaces and apply strict network policies to limit communication.

Both EKS and GKE also support Virtual Private Cloud (VPC) and private subnet configurations, enabling further isolation of workloads from the public internet.

Authentication & Authorization

RBAC and Service Accounts

RBAC plays a critical role in securing access to the Kubernetes API server. Define precise roles and role bindings to control who can access what resources.

Service Accounts: For applications running within your cluster, always use dedicated service accounts with minimum required privileges. Avoid using the default service account, as it may grant more permissions than necessary.

Example of a RoleBinding:

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: example-binding
  namespace: default
subjects:
  - kind: ServiceAccount
    name: example-sa
    namespace: default
roleRef:
  kind: Role
  name: example-role
  apiGroup: rbac.authorization.k8s.io

Identity Federation

Integrating Kubernetes clusters with cloud-native identity providers helps manage users and permissions consistently.

EKS: EKS integrates with AWS IAM, which can be used to manage user permissions via IAM roles for service accounts (IRSA). This allows Kubernetes workloads to assume IAM roles with permissions for accessing other AWS services.
GKE: GKE integrates with Google Cloud IAM, allowing fine-grained control over who can access the cluster and its resources.

Enable Multi-Factor Authentication (MFA)

For additional protection, enable MFA on your cloud accounts and Kubernetes access, ensuring that only authorized users can interact with the cluster.

Securing Container Images

Use Trusted Image Sources

The security of your containers starts with the images used to build them. Always pull container images from trusted sources, and ideally, build and store your own images in private registries.

EKS/GKE: Both support integration with managed image repositories like Amazon ECR and Google Container Registry (GCR). These registries can be used with image signing tools like cosign to verify the authenticity of the images.

Image Scanning and Vulnerability Assessment

Scan container images for vulnerabilities before deploying them to your cluster. Tools like Trivy, Clair, and Anchore can scan images for known vulnerabilities, helping ensure that only secure images are used.

Limit Container Privileges

Containers should run with the least privileges necessary. Enforce security policies that prevent containers from running as the root user unless absolutely necessary. Configure the securityContext to restrict capabilities like SYS_ADMIN and NET_ADMIN.

Runtime Security

Security Context and Pod Security Policies (PSP)

Kubernetes allows you to define SecurityContext for both pods and containers, setting limits on resource usage, restricting access to host resources, and controlling privileges.

PSP (Pod Security Policies) can be used to enforce security settings on pods, such as preventing privilege escalation or ensuring containers are run with specific user IDs.

As PSP is deprecated in newer Kubernetes versions, consider using alternatives like OPA (Open Policy Agent) and Kubernetes Gatekeeper to enforce security policies in a more flexible way.

Runtime Monitoring

Integrate Falco or Sysdig for real-time monitoring of system calls, which can help detect anomalous behaviors such as privilege escalations or unauthorized access attempts. These tools provide visibility into what’s happening inside your containers and help identify potential security threats before they escalate.

Data Protection

Encryption at Rest and In Transit

EKS/GKE: Both platforms provide encryption options for data at rest (e.g., Amazon EBS, Google Persistent Disks) and in transit (e.g., enabling TLS for pod communication). Always ensure that sensitive data is encrypted both at rest and during transit.

For application-specific data encryption, you can use Kubernetes-native solutions like Kubernetes Secrets, but consider integrating more robust external solutions like AWS Secrets Manager or HashiCorp Vault for better key management and enhanced security.

Backup and Disaster Recovery

Regularly back up your Kubernetes resources, including etcd (the key-value store that holds the cluster state), and have a disaster recovery plan in place. Both EKS and GKE offer automated backup solutions to protect your cluster state and workloads.

Logging & Monitoring

Enable Cluster Logging

Centralized logging helps identify and mitigate security incidents early. Both EKS and GKE offer integrations with logging services like Amazon CloudWatch Logs and Google Cloud Logging. Enable audit logs to track user and system activities, providing visibility into suspicious actions.

Prometheus and Grafana for Monitoring

Prometheus is the go-to tool for monitoring Kubernetes clusters, and Grafana can be used for visualizing metrics. Together, they can help you monitor not only the health of the cluster but also the security aspects, such as unusual resource consumption or unusual network activity.

Continuous Integration and Continuous Deployment (CI/CD)

Automated Vulnerability Scanning in Pipelines

Integrate security tools into your CI/CD pipeline to ensure that vulnerabilities are identified early in the development process. Tools like Snyk and Aqua Security can scan dependencies and container images during the build process, allowing you to catch security issues before they reach production.

Conclusion

Securing a Kubernetes cluster on EKS or GKE requires a multi-faceted approach. By leveraging cloud-native features like private API endpoints, RBAC, IAM integration, and image scanning, along with runtime security tools like Falco and security policies like PSP, you can ensure that your clusters are hardened against potential threats. Furthermore, continuous monitoring, vulnerability assessments, and encryption best practices will help maintain a strong security posture over time.

By implementing these security best practices, you not only safeguard your Kubernetes clusters but also build a robust foundation for running containerized applications in a secure and compliant manner.