Kubernetes provides a powerful platform and solution for deploying and managing containerized applications. Its ease of use and numerous benefits have made it a mainstream option for many developers and a significant part of many organizations’ IT infrastructure. However, its popularity also makes it a prime target for attackers. Securing your Kubernetes cluster is crucial for protecting your applications and the data they contain, maintaining system stability, and preventing unauthorized access. In this article, we look at tips and strategies provided by Kubernetes, Google, developers, and others for mitigating risks in your Kubernetes cluster.
Enable Role-Based Access Control (RBAC)
Role-based access control lets you define who can access your API and their permissions. This functionality is now enabled by default on Kubernetes 1.6 and above, but it might only be supported on later versions on some hosted and managed Kubernetes providers.
Before enabling this option, you should understand that it combines authorization controls. This means you must disable older Attribution-Based Access Control when you use it.
When using this option, go with namespace-specific permissions and avoid cluster-wide ones. This applies even when debugging because it is always better and safer to let users only have the specific permissions and access they need for specific situations.
Secure Your Image Containers
Image containers can introduce vulnerabilities when they are deployed and used. Kubernetes recommends you scan all images at build time to identify any vulnerabilities they may have before deploying them. It is best practice to use vulnerability scanners for this and to strongly consider only using signed images from trusted registries.
If you have a fast-moving development pipeline or do not want to do this, it is also a great idea to lean on managed Kubernetes K8s service providers. They have trusted and signed container images that you can deploy in a few seconds. Using their solutions gives you peace of mind in knowing that they have already dealt with the vulnerabilities so you do not have to look for them yourself.
Additionally, these services will patch and update their Kubernetes version for you to remove any discovered vulnerabilities and ensure your cluster continues performing optimally.
Implement the Principle of Least Privileges
Developers and users do not always require all the privileges that your Kubernetes cluster allows them to have. The principle of least privilege requires you to only provide the minimum permissions needed for your pods to run.
Doing this reduces the espoused attack surface that malicious actors can latch on to. It also ensures developers do not have the power to affect or interact with parts of the cluster that they are not supposed to.
Add a Third-party Authentication for Your Server API
Third-party authentication providers have already done the difficult work of allowing secure access and authorization for applications and software. It is the reason many developers rely on them because they do not have to spin up their own solutions and deal with the challenges and edge cases they will likely encounter doing so.
Using third-party authentication providers like GitHub and Google for your API server is one of the recommended best practices for API servers. These services provide additional security features, including multi-factor authentication features. They also ensure your API server does not change when you add or remove users.
It is also good practice to not manage your users at the API server level. Instead, you can use different connectors to do so and ensure the integrity of your cluster and API server.
Isolate Your Kubernetes Nodes
One of the most catastrophic mistakes people make when deploying Kubernetes is exposing their nodes to public networks. For the best security, ensure your nodes are on a separate network and not connected to public networks. Some security experts even encourage you to ensure that you configure them to avoid a direct connection to your corporate network.
When doing this, use Kubernetes control to isolate control and data traffic. If you do not do this, both will flow through the same connections, and open access to your data pathways means that there will be open access to the control pathways.
Security experts recommend you set your nodes to only allow connections from a master node on a specific port. You can set this up using the network access control list.
Ensure Proper Secret Management
Your secrets give anyone with access to them access to your Kubernetes cluster. The most common of these are passwords and API keys that should never end up in the hands of unauthorized persons or malicious actors.
Best practices demand you store these and other secret data as Kubernetes secrets. Additionally, you should ensure that these secrets remain encrypted whether they are at rest or in transit.
Crucially, never store them in your pod configuration or container images. Also, check that they are on your “gitignore” list if you use Git for version control. This will ensure they do not end up in a Git repository where anyone can find and use them.
Turn On Audit Logging
Ensure that your audit logs are enabled to easily monitor unwanted or unusual API calls. You should also be on the lookout for authentication failures that could indicate someone is trying to access your cluster using stolen credentials.
Kubernetes is flexible enough to allow you to tell it what events you want to log. You can set one of four logging options:
- None
- Requests – This logs requests and metadata but no responses
- Metadata only
- RequestResponse – This logs responses, requests, and metadata
Using a managed Kubernetes provider often means you access this data in your console. You do not have to set up the logging yourself, you have the data organized for easy analysis, and you can easily set up notifications so that you always know about authorization failures.
Developers and organizations can significantly improve the security of their Kubernetes clusters by following best practices. Doing so can mitigate the risk of vulnerabilities and all the issues associated with them. Even when you implement these practices, always remember that security is an ongoing process. So, you should continuously evaluate and adapt your security practices, especially as malicious actors continuously try to find ways to break into your clusters and applications.