Kubernetes Security part 1/4 - A basics Definition and Introduction
Vishwas N.
Re-Inventing AI Acceleration for Enterprise | Training to be a Frugal Architect | Big Believer in "Product Ecosystem Fit" | Intrapreneur - Startup Swiss Army Knife(someone gave me this title)
It could appear difficult to secure Kubernetes. Kubernetes cannot be secured by merely turning on a security module or installing a security solution since it is a very complicated system made up of several unique components.
Instead, teams must handle every form of security risk that might have an impact on the many levels and services within a Kubernetes cluster, according to Kubernetes security. Teams must be aware of how to protect Kubernetes nodes, networks, pods, data, and other components.
Kubernetes administrators also need to be aware of the security tools that Kubernetes comes with out of the box and which third-party security solutions they'll need to integrate with their clusters to cover any holes. This is a complicated subject since, although not a security platform, Kubernetes does offer some native security features, such as Role-Based Access Control (RBAC).
If you're new to Kubernetes and still trying to understand how everything works, let alone how to keep it safe, all of the above may seem daunting. However, if you break the ideas down into manageable chunks, they are quite straightforward. To that aim, this article outlines the principles of each of the many aspects of Kubernetes security and offers best practices for security in Kubernetes at all layers and service levels.
Piece by Piece: Kubernetes Security
Thinking about the different threats that each component of the Kubernetes stack is exposed to, then identifying the tools and resources available to help protect them, maybe the easiest way to approach Kubernetes security.
The servers that makeup Kubernetes clusters are known as nodes. Nodes typically run some variation of Linux, however, worker nodes occasionally run Windows. From a security standpoint, it doesn't matter whether nodes are virtual machines or bare-metal servers. The same security measures you would use to safeguard any sort of server should be used to secure Kubernetes nodes. These consist of:
deleting unnecessary operating system files, libraries, and other components to reduce the attack surface. A smart practice is to provision nodes with lightweight Linux distributions like Alpine Linux.
You probably already know how to manage Kubernetes node security if you have expertise in securing servers at the operating system level in any kind of scenario. Security issues for nodes running Kubernetes are much the same as those for any other type of server at the node level.
Additionally, there are no essential distinctions between securing a worker node and a master node. However, the steps for protecting the operating system on a master node are the same as for a worker node. Master node security is somewhat more crucial because a breach on a master node might harm your cluster more.
Security for Kubernetes API
The many components of a cluster are connected through the Kubernetes API. It's one of the most crucial resources in Kubernetes to secure as a result.
The Kubernetes API is created with security as a given. Only requests that it can successfully authenticate and authorize will receive a response.
However, you can configure RBAC policies to control API authentication and authorization. As a result, the security of the API depends on your RBAC policies. Thus, a fundamental best practice for guaranteeing Kubernetes API security is the creation of safe RBAC policies that uphold the doctrine of least privilege and issue rights in a detailed manner.
Additionally, by utilizing admission controllers, you may increase API security even more. After the API server has authenticated and allowed requests, admission controllers review them. Admission controllers offer a secondary line of protection against requests that shouldn't be approved in this way. You can impose different security regulations on API requests by enabling and setting up admission controllers. Here is a list of the available rules.
Finally, network-level security for API queries may be achieved by setting up secure certificates and mandating that the API server responds to requests on a secure port rather than a local host.
Network Security for Kubernetes
Similar to pod security, Kubernetes network security begins by adhering to the best practices you would apply to protect any network.
If at all feasible, you should design a network architecture that keeps tasks away from the general Internet until they require an interface. To stop traffic from violating hosts, you should install firewalls at the gateway level. For indications of a breach, you should keep an eye on network activity. All of these actions may be carried out with the use of tools not related to Kubernetes, such as a service mesh.
But Kubernetes also provides a small set of native tools that can aid in protecting networking resources. Network policies are this tooling's primary form. Although network policies aren't specifically a security feature, administrators may use them to regulate how traffic moves throughout a Kubernetes cluster.
As a result, you may build network policies to conduct things like network-level pod isolation or traffic filtering.
Consider network policies as an extra resource that supplements the security rules that you incorporate into your entire network architecture rather than as a replacement for safeguarding networking settings outside of Kubernetes.
Security for Kubernetes Pods
A container or group of containers used to run an application is referred to as a pod in Kubernetes. So you must protect your pods to secure your apps.
Some pod security requirements call for procedures that are not Kubernetes-specific. Before deployment, you should do security checks on your application, and you should also scan container images. To find possible breaches or misuse, you should gather and examine pod logs.
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However, Kubernetes has certain native capabilities that, after pods have started operating, can strengthen security. These consist of:
RBAC rules, which may be used to control how users and services inside the cluster have access to pods.
Security contexts, specify the level of access that pods have.
As mentioned above, you may use network rules to isolate pods at the network level.
Admission controllers can apply extra rules that expand the RBAC-based rules you already established.
The nature of your workloads will determine the kinds of pod security measures you employ and how you configure them. Security measures for pods cannot be applied universally. For instance, some pods don't require communication and can be completely network-isolated from one another.
Regardless of your particular needs, you should assess the tools at your disposal to protect Kubernetes pods and make sure you make the most of them.
Data Security for Kubernetes
Except for the temporary data included in active pods and the log data kept on nodes, Kubernetes doesn't keep any data. The data that your clusters produce and/or access often resides in an external storage system that communicates with Kubernetes via a storage plugin.
Therefore, you should adhere to the best practices that you would employ to protect data inside any large-scale storage system to safeguard Kubernetes-related data. Data at rest should always be encrypted. To limit who may access data, use access control technologies. Be sure to securely lock down the servers that control your storage pools. Data backup can help you fend against data theft and ransomware threats.
Kubernetes does not provide any unique capabilities for safeguarding the relatively tiny quantities of data that reside natively inside its pods and nodes. However, you may safeguard it by utilizing the aforementioned best practices to safeguard your nodes and pods.
Additional Resources for Kubernetes Security
Administrators should be aware of additional security resources for Kubernetes in addition to the component-specific security measures mentioned above.
Audit Records
Optionally, Kubernetes may preserve detailed records of which operations were carried out in a cluster, who carried them out, and what the outcomes were. You may thoroughly audit your clusters using these audit logs to both investigate security events in the future and identify possible security vulnerabilities in real-time.
You must first construct an audit policy, which specifies how Kubernetes will record events before you can use audit logs. Complete information on creating audit policies is provided in the Kubernetes documentation. Additionally, as Kubernetes lacks the capabilities necessary for large-scale audit log analysis, you'll probably want to stream audit logs to a third-party monitoring or observability platform, which will enable you to see abnormalities and get alerts about security breaches. If not, you can only manually keep track of audit events, which is impractical on a large scale.
Namespaces
Namespaces in Kubernetes may be used to separate various workloads from one another.
It's a great practice from a security perspective to construct multiple namespaces for each team and/or kind of workload in your cluster, however, you can run everything inside a single namespace if you like. Use several namespaces, for instance, to divide your development/testing environment from your production environment.
Having to set various RBAC policies for each namespace is a need in many (but not all) situations, which adds to the administrative complexity of Kubernetes when managing several namespaces. The extra work is worthwhile, though, as it lessens the potential effects of a breach.
Using Kubernetes and External Security Tools
Even though Kubernetes offers certain tools to assist protect the resources that are operating inside of your cluster, Kubernetes is not intended to support the detection or management of security problems.
Conclusion
Since 1.13, Kubernetes has offered a beta version of the functionality known as encryption at rest. This will encrypt your etcd backups' Secret resources, shielding their contents from anyone who has access to them.