As with any technological component, security must be a primary consideration when managing a Kubernetes environment. Applications are constantly at the risk of compromising with constantly evolving threat vectors. With more and more applications utilizing cloud platforms, adopting a cloud-native security model has become more important than ever to secure your environments and applications. This fact also applies to a containerized environment. There is a high possibility that a single vulnerability in a container can be exploited to gain control over the entire Kubernetes cluster. Thus, it is crucial to adopt the correct security model at the beginning.

Let’s expand upon each section to understand better what entrails this security model.

• Cloud
• Cluster
• Container
• Code

Let’s expand upon each section to gain a better understanding of what entrails this security model.

Cloud – Secure the Underlying Infrastructure

Even when dealing with managed Kubernetes services, you will have to deal with other infrastructure resources in some capacity. A managed service eliminates the need for managing the cluster hardware resources or keeping them updated. However, other cloud infrastructure components like Security Groups, firewalls, and network access controls need to be constantly evaluated to maintain a secure environment. Even those who have access to the cloud environment can be a risk factor if not properly managed.

If utilizing an external container registry, it should also be secured with proper authentication and authorization controls. Moreover, secure connectivity between the cluster and the registry should be ensured. These access controls should also be extended to any persistent storage outside the cluster and encrypted when possible.

Restricting access to the API server on the control plane and restricting access to the node with ingress only allowed from the control plane are good first steps to improve cloud security at the Kubernetes level.

Cluster – Securing Kubernetes

Next comes securing the cluster itself. The first step towards this is enabling role-based access control to restrict access to the Pods and restrict the privileges of users who have access to the cluster. Additionally, implementing Pod security standards with standardized policies that apply to all the Pods will greatly improve the security of the cluster while enforcing standardization across the environment.

Secrets stored in etcd are not encrypted by default, leading to serious security issues. Thus, all data at rest must be encrypted. Kubernetes enables implementing network policies to restrict communication between pods when it comes to internal networking. These policies limit which containers can communicate with each other, even if a container is compromised. TLS should be enforced on all traffic from an ingress point to the cluster parameter, regardless of the workload.

Containers- Building Secure Containers

The third point of the cloud-native security model is securing the containers. Developers must ensure that applications do not run as root when building a container image. If the application runs as a privileged user by default and is compromised, the attacker can directly gain access as a privileged user. Here, the best practice will be using separate user accounts/groups for the application and OS functionalities.

This process of separation can also be helpful when debugging a container, as users can easily identify the underlying issue. In Kubernetes, container exit codes help you diagnose issues. For example, Exit Code 1 indicates that a container shut down.

Image vulnerability scanning at build time and periodic scans of the container registry can be used to weed out any potential vulnerabilities when building the image. They are also helpful to quickly detect newly discovered vulnerabilities that can affect already built images. Enforcing image signing is also a must-have in any production environment. When it is coupled with a properly access-controlled container registry, the chances of incorrect images getting pulled to the Kubernetes environment will be reduced.

Code – Securing the Application

Even with the best security practices, an application that is vulnerable to all other security configurations becomes a moot point. Therefore, security should be an integral consideration at the application development level. Practices like static code analysis and checking for vulnerabilities in third-party libraries and application code can greatly reduce the chance of vulnerabilities causing issues in production. Even if a fix is unavailable for a discovered vulnerability, it can be properly tracked, and steps can be taken to reduce its impact on the application.

Other practices to secure an application include limiting the ports used in the application for communication and requiring TLS on all TCP communication to protect data at transit. Even simple changes like moving all the sensitive environment variables to Kubernetes secret can help improve the overall security posture of the application.

Conclusion

By adopting a cloud-native security model across your environment.Adopting a proper security model from code to the cloud level is the first step towards achieving a secure environment. Even with all the security controls and best practices implemented, there can be incidents that comprise a Kubernetes environment. However, these risks of unexpected vulnerabilities or attacks compromising your environment and the application can be greatly reduced.