Kubernetes Security Best Practice
Kubernetes has become the go-to container orchestration platform for organizations worldwide due to its flexibility and scalability. However, as with any technology, ensuring robust security measures is crucial for safeguarding sensitive data and maintaining the integrity of Kubernetes clusters. In this blog post, we will discuss essential Kubernetes security best practices that every organization should implement to protect their infrastructure and applications.
Highlights: Kubernetes Security Best Practice
- An Orchestration Tool
Kubernetes has quickly become the de facto orchestration tool for deploying Kubernetes microservices and containers to the cloud. It offers a way of running groups of resources as a cluster and provides an entirely different abstraction level to single container deployments, allowing better management. From a developer’s perspective, it allows the rolling out of new features that align with business demands while not worrying about the underlying infrastructure complexities.
- Security Pitfalls
But there are pitfalls to consider when considering Kubernetes security best practices and Docker container security. Security teams must maintain the required visibility, compliance, and control, which is difficult because they do not control the underlying infrastructure. To help you on your security journey, you should introduce a chaos engineering project, specifically chaos engineering kubernetes.
This will help you find the breaking points and performance-related issues that may indirectly create security gaps in your Kubernetes cluster, making the cluster acceptable to Kubernetes attack vectors.
Before you proceed, you may find the following posts helpful:
Kubernetes Attack Vectors
- A key point: Video on Immutable Infrastructure
The following video discusses Immutable Infrastructure. The birth of virtualization gave rise to virtual servers and the ability to instantiate workloads within a shorter period. Similar to how virtualization brings new ways to improve server infrastructure, Immutable server infrastructure takes us one step further. Firstly, mutable server infrastructure is servers that require additional care once they have been deployed.
This may include an upgrade, downgrade, or a tweak configuration file for a specific optimization. Usually, this is done on a server-by-server basis. Secondly, an Immutable server infrastructure is servers that are not tweaked after deployment.
It’s an entirely new paradigm where if a change needs to occur, a new server is built from a standard image along with the required change included in that image.
Back to basics with Kubernetes security best practice
As workloads move to the cloud, Kubernetes is the most common orchestrator for managing them. The reason Kubernetes is popular is its declarative nature: It abstracts infrastructure details and allows users to specify the workloads they want to run and the desired outcomes.
However, securing, observing, and troubleshooting containerized workloads on Kubernetes are challenges. It needs a range of considerations, from infrastructure choices and cluster configuration to deployment controls, runtime, and network security. Keep in mind that Kubernetes is not secure by default.
Regularly Update Kubernetes:
Keeping your Kubernetes environment up to date is one of the fundamental aspects of maintaining a secure cluster. Regularly updating Kubernetes ensures that you have the latest security patches and bug fixes, reducing the risk of potential vulnerabilities.
Enable RBAC (Role-Based Access Control):
Implementing Role-Based Access Control (RBAC) is crucial for controlling and restricting user access within your Kubernetes cluster. By assigning appropriate roles and permissions to users, you can ensure that only authorized personnel can perform specific operations, minimizing the chances of unauthorized access and potential security breaches.
Use Network Policies:
Kubernetes Network Policies allow you to define and enforce rules for network traffic within your cluster. By utilizing network policies effectively, you can isolate workloads, control ingress and egress traffic, and prevent unauthorized communication between pods. This helps in reducing the attack surface and enhancing the overall security posture of your Kubernetes environment.
Employ Pod Security Policies:
Pod Security Policies (PSPs) enable you to define security configurations and restrictions for pods running in your Kubernetes cluster. By defining PSPs, you can enforce policies such as running pods with non-root users, disallowing privileged containers, and restricting host namespace sharing. These policies help prevent malicious activities and reduce the impact of potential security breaches.
Implement Image Security:
Ensuring the security of container images is crucial to protect your Kubernetes environment. Employing image scanning tools and registries that provide vulnerability assessments allows you to identify and address potential security issues within your images. Additionally, only using trusted and verified images from reputable sources reduces the risk of running compromised or malicious containers.
Monitor and Audit Cluster Activity:
Implementing robust monitoring and auditing mechanisms is essential for detecting and responding to security incidents promptly. By leveraging Kubernetes-native monitoring solutions, you can gain visibility into cluster activity, detect anomalies, and generate alerts for suspicious behavior. Furthermore, regularly reviewing audit logs helps in identifying potential security breaches and provides valuable insights for enhancing the security posture of your Kubernetes environment.
Kubernetes Attack Vectors
The hot topic for security teams is how to improve Kubernetes security, implement Kubernetes security best practice within the cluster, and make container networking deployments more secure. Kubernetes is a framework that provides infrastructure and features. But it would be best to think outside the box regarding Kubernetes security best practices.
We are not saying that Kubernetes doesn’t have built-in security features to protect your application architecture! It includes logging and monitoring, debugging and introspection, identity, and authorization. But ask yourself, do these defaults cover all aspects of your security requirements? Remember that much of the complexity with Kubernetes can be abstract with OpenShift networking.
A key point: Video with OpenShift Networking
In the past, the application stack had very few components, maybe just a cache, web server, and database. The most common network service simply allows a source to reach an application endpoint or load balance to a number of endpoints using a load balancing algorithm. The sole purpose of the network was to provide endpoint reachability.
Changes inside the data center are driving networks and network services towards becoming more integrated with the application. Nowadays, the network function exists no longer solely to satisfy endpoint reachability; it is fully integrated and in the case of Red Hat’s Openshift the network is represented as a Software-Defined Networking (SDN) layer.
Traditional Security Constructs
Traditional security constructs don’t work with containers. And we have seen this with the introduction of Zero Trust Networking. Containers have a different security model as they are short-lived and immutable. For example, securing containers differs from securing a virtual machine (VM).
For one, the attack surface is smaller as containers usually only live for about a week, as opposed to a VM that may stay online forever. As a result, we need to manage vulnerabilities and compliance through the container scheduler lifecycle – from build tools, image registries, and production.
How do you measure security within a Kubernetes environment? No one can ever be 100% secure, but one should follow certain best practices to harden the gates against bad actors. You can have different levels of security within different parts of the Kubernetes domain. However, a general Kubernetes security best practice would be introducing as many layers of security between your Kubernetes environment and the bad actors to secure valuable company assets.
Hackers are growing in sophistication. We started with script kiddies in the 1980s and are now entering a world of artificial intelligence ( AI ) and machine learning (ML) in the hands of bad actors. They have the tools to throw everything and anything at your Kubernetes environment, dynamically changing attack vectors on the fly.
If you haven’t adequately secured the domain, once a bad actor gains access to your environment, they can move laterally throughout the application stack, silently accessing valuable assets.
Before we delve into some of Kubernetes’ security best practices and the Kubernetes attack vectors, let’s recap Kubernetes networking 101. Within Kubernetes, there will always be four common constructs – pods, services, labels, and replication controllers. All constructs combine to create an entire application stack.
Pods are the smallest scheduling unit within a Kubernetes environment that holds a set of closely related containers. Containers within a Pod share the same network namespace and must be installed on the same physical host. This enables processing to be performed locally without latency traversing from one physical host to another.
As I said, containers within a pod share the same network namespaces. As a result, the containers within a pod can reach each other’s ports on localhost. Therefore we need to introduce a tagging mechanism known as labels. Labels offer another level of abstraction by tagging items as a group. They are essentially key-value pairs categorizing constructs. For example, labels distinguish containers as part of an application stack’s web or database tier.
- Replication Controllers (RC)
Then we have replication controllers. Their primary purpose is to manage the lifecycle and state of the pods by ensuring the desired state always matches the actual state. The replication controllers ensure the correct numbers are running. Either creating or removing pods at any given time.
Other standard Kubernetes components are services. Services represent groups of pods acting as one, allowing pods to access services in other pods without directing service-destined traffic to the pod IP. Pods are targeted by accessing a service that represents a group of pods. A service can be analogous to a load balancer in front of a pod accepting front-end service-destined traffic.
- Kubernetes API server
Finally, the Kubernetes API server validates and configures data for the API objects, which include the construct mentioned above – pods, services, and replication controllers, to name a few.
Also, consider the practice of chaos engineering to understand your Kubernetes environment better and test for resilience and breaking points. Chaos engineering Kubernetes breaks your system to help you better understand your system.
A key point: Video on Chaos Engineering
This educational tutorial will start with guidance on how the application has changed from the monolithic style to the microservices-based approach along with how this has affected failures. I will introduce to you how this can be solved by knowing exactly how your application and infrastructure perform under stress and what are their breaking points
Kubernetes Security Best Practice: Security 101
Now that you understand the most commonly used Kubernetes constructs let us delve into some of the central Kubernetes security best practices and Kubernetes attack vectors.
- Kubernetes API
Firstly, a bad actor can attack the Kubernetes API server to attack the cluster further. By design, each pod has a service account associated with it. The service account has full permissions and sufficient privileges to access the Kubernetes API server. A bad actor can get the token mounted in the pod and then use that token to gain access to the API server. Unfortunately, once they can access the Kubernetes API server, they can get information, such as secrets, to further compromise the cluster. For example, a bad actor could access the database server where sensitive and regulatory data is held.
- Kubernetes API – Mitigate
Another way to mitigate a Kubernetes API attack is to introduce role-based access control (RBAC). Essentially, RBAC gives rules to service accounts that can be assigned to the entire cluster. RBAC allows you to set permission on individual constructs such as pods and containers and then define rules based on individual use cases. Another Kubernetes best practice would be to introduce an API server firewall. This firewall would work similarly to a standard firewall, where you can allow and block ranges of addresses. Essentially, what this does is that it narrows the attack surface, hardening Kubernetes security.
- Secure pods with network policy
Introducing ingress and egress network policies would allow you to block network access to certain pods. Then only certain pods can communicate with each other. For example, network policies can be set up to restrict the web front end from communicating directly to the database tier.
There is also a risk of a user implementing unsecured pods. In this case, you can have network policies in place so that if an unsecured pod does appear in the Kubernetes environment, the Kubernetes API will reject them. Remember, left to its defaults, intra-cluster pod-to-pod communication is open. You may think a bad actor could sniff this traffic, but that’s harder to do than in everyday environments. A better strategy to harden Kubernetes security would be to use a network policy only to allow certain pods to communicate with each other.
- Container escape: In the past, an unpatched kernel or a bug in the web front-end allows a bad actor to get out of that container and gain access to other containers or even to the Kubelet process itself. Once the bad actor gets access to the Kubelet client, it can access the API server gaining a further foothold in the Kubernetes environment.
- Sandboxed Pods: One way to mitigate a container escape would be to introduce sandboxed pods inside a lightweight VM. A sandboxed pod provides additional barriers to security as it lies above the kernel itself. Providing layers of security above the kernel brings many Kubernetes security advantages. As the sandboxed pod runs inside a VM, an additional bug is required to break out of the container if there is a kernel exploit.
- Scanning containers: For adequate Kubernetes security, you should know if there is a vulnerability in your container image. Running containers with vulnerabilities exposes the entire system to attacks. Scanning all container images to discover and remove known vulnerabilities would be best. The scanning function should be integrated with runtime enforcement and remediation capabilities enabling a secure and compliant SDLC (Software Development Life Cycle).
- Restrict access to Kubectl: Kubectl is a powerful command-line interface for running commands against Kubernetes clusters. It allows you to create and update resources in a Kubernetes environment. Due to its potential, one should restrict access to this tool with firewall rules.
- Disabling the Kubernetes dashboard: Disabling the Kubernetes Dashboard is a must, as it has been part of some high-profile compromises. Previously, bad actors accessed a publicly unrestricted Kubernetes dashboard and privileged account credentials to access resources and mine cryptocurrency.
As Kubernetes adoption continues to grow, ensuring the security of your cluster becomes increasingly important. By following these Kubernetes security best practices, you can establish a robust security foundation for your infrastructure and applications.
Regularly updating Kubernetes, enabling RBAC, utilizing network policies, employing pod security policies, implementing image security measures, and monitoring cluster activity will significantly enhance your Kubernetes security posture. Embracing these best practices will not only protect your organization’s sensitive data but also provide peace of mind in today’s ever-evolving threat landscape.