Kubernetes Security in Your CI/CD Pipeline

Kubernetes security involves implementing security measures and tools and adopting best practices for protecting Kubernetes workloads. Kubernetes is an open source container management platform across public, private and hybrid clouds. Organizations employ Kubernetes to manage containers and microservices architecture. 

Kubernetes is a highly complex system composed of many different components, which means you cannot protect it by enabling security modules or simply installing security tools. Kubernetes security requires addressing the various security risks that can impact all layers and services composing a Kubernetes cluster, including networks, nodes, pods and data.

To properly address Kubernetes security risks, Kubernetes administrators need to understand Kubernetes security tools and their limitations and utilize third-party tools that can integrate with a cluster to close security gaps.

CI/CD With Kubernetes 

Containerization and platforms like Kubernetes have created a new computing paradigm that increases consistency, velocity and agility. Engineering teams can leverage the common declarative language describing operational and application tasks, making Kubernetes a popular way to run distributed workloads. 

How Kubernetes Works

Once Kubernetes authors and applies the desired application state in declarative YAML, it can resolve the declared state. For example, Kubernetes will ensure the application has the right number of replicas and resolve the difference when it detects a deviation. Thus, the actual state remains the same as the declared state. 

Deploying to Kubernetes is fast and easy, even with minimal experience. You create a deployment YAML and give the kubectl apply command. Kubernetes uses rolling updates to make incremental changes when necessary. It is much easier to watch Kubernetes implement a rolling update than to hand-write rules to enable updates in another platform. 

Why use CI/CD?

When adopting Kubernetes, it is crucial to use CI/CD best practices. Kubernetes does not eliminate the need for a robust CI/CD pipeline—rather, Kubernetes offers advantages to help strengthen your CI/CD. 

Designing CI/CD pipelines can be challenging given Kubernetes’ restless nature and the microservices architecture. There are three main challenges to building and using Kubernetes CI/CD pipelines:

  • Automated tests—These allow you to create and deploy reliable cloud applications. You must fully test all commits by developers before continuing to the next stage of the pipeline. Testing can be challenging due to different cloud vendor integrations and the Kubernetes API.
  • Deployments and rollbacks—Kubernetes offers reliable, scalable deployment APIs to enable cloud application releases with minimal downtime. Your CD pipeline should include cloud-native deployment strategies like rolling upgrades, A/B testing or blue-green deployments. The deployment pipeline should also roll back to the latest working version when there is an issue in a deployment. Thus, the pipelines must include an effective deployment and rollback automation strategy.  
  • Scalability—When using Kubernetes in production, it might support tens or hundreds of applications. If you have multiple apps, the CI/CD tools you use must run multiple pipeline instances in parallel and watch many source code repositories. Thus, you must design the CI/CD pipeline for scalability, allocating sufficient resources for the workers. 

Best Practices for Securing Your Kubernetes CI/CD Pipeline 

Here are best practices to consider when building a secure CI/CD pipeline:

Keep Secrets Secure

In Kubernetes, secrets are digital credentials that help authenticate and authorize various CI/CD services and applications on a cluster. However, a source control system, such as GitHub, can expose secrets during a CI/CD pipeline deployment. To ensure secrets remain secured even when exposed, you should encrypt them when exposed outside the container.

Implement Git-Based Workflows (GitOps)

Git-based operations can trigger CI/CD pipelines, facilitating usability and collaboration. Git stores all pipeline changes and the source code in a single source repository, ensuring developers can review changes and eliminate identified errors before deploying. It also supports build snapshots and chat tools integration to help track and recover changes during failures.

Leverage Blue-Green Deployment Patterns

CI/CD pipelines deploy code into production after it passes certain requirements for each stage. Ideally, you want your CI/CD stages to work properly and result in accurate deployment. However, some scenarios, like security flaws or resource outages, can lead to issues. 

A blue-green deployment pattern can initialize an additional parallel set of deployment instances to existing production instances. It enables you to switch more easily during failures and downtimes.

Test and Scan Container Images

It is crucial to test and scan a container image whenever a new image is built during a continuous integration (CI) process. It can help detect vulnerabilities and fix them before they severely impact security. 

When testing a container image, you must ensure commands properly work in the container and verify they include correct specifications and contents. You can run an image scan to find vulnerabilities that a new build pushed to a container registry might introduce.

Secure Coding

Coding a container with security in mind ensures a solid security foundation. Any security measure and tool you add to your secure code helps further harden security. However, insecure design is much more difficult to fix. Here are best practices to securely code containers for Kubernetes deployments:

  • Use TLS to encrypt data in transit for securing transmission control protocol (TCP) network communications. 
  • Reduce the number of open TCP ports and keep only those required for monitoring or communications. 
  • Scan third-party code and libraries for vulnerabilities. 
  • Use a penetration testing tool for internet-facing applications. Check for common vulnerabilities like cross-site scripting (XSS) and SQL injection.

Conclusion

In this article I explained why CI/CD pipelines are an important element of Kubernetes security, and provided several critical best practices for securing your CI/CD pipelines:

  • Keep secrets secure – Ensure secrets are not kept in plaintext in source control or Kubernetes configuration files.
  • Implement Git-based workflows (GitOps) – Ensure a separation between CI and CD and fully declarative configuration of CI/CD pipelines.
  • Leverage blue-green deployment patterns – Make it possible to easily roll back to a previous version in case of security or stability issues.
  • Test and scan container images – Never use container images in any environment without scanning them for vulnerabilities.
  • Secure coding – Ensure you use secure coding practices for any application code running within a Kubernetes cluster.

Gilad David Mayaan

Gilad David Maayan is a technology writer who has worked with over 150 technology companies including SAP, Samsung NEXT, NetApp and Imperva, producing technical and thought leadership content that elucidates technical solutions for developers and IT leadership.

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