Kubernetes Services: What Are They and How to Protect Them

Kubernetes is a vast distributed platform that utilizes services to communicate internally and externally. Understanding different types of services and how they work is the beginning of knowing how things go in and out of your cluster and pods.

In this article, you will learn what a Kubernetes service is and different types of Kubernetes services in detail. In addition, you will learn how to implement and protect Kubernetes services.

Prerequisites

If you want to work through the examples, you will need a running cluster, and the Kubectl command line tool.

What Are Kubernetes Services?

A Kubernetes service is a logical abstraction that enables communication between different components in Kubernetes. Services provide a consistent way to access and communicate with the application’s underlying components, regardless of where those components are located.

In Kubernetes the default type is ClusterIP. Services abstract a group of pods with the same functions. Services expose pods and clusters. Services are crucial for connecting the backend and front-end of your applications.

One of the key benefits of using Kubernetes services is that they enable you to manage your applications at a higher level of abstraction. Instead of having to manage individual containers and their interactions with each other, you can use services to define how your application should communicate and let Kubernetes handle the details. This can make it easier to deploy, scale, and manage your applications, especially if they are complex and distributed.

Another benefit of using Kubernetes services is that they provide a consistent way to access your application, regardless of where the underlying components are located. For example, if you have a microservice-based application, each service can be accessed using the same service name and port number, regardless of which host it is running on. This makes it easier for your application components to communicate with each other and reduces the complexity of managing distributed applications.

Five Types of Kubernetes Services

Below is an example of a service configuration YAML file. The configuration file. It has the metadata section which describes the names,app, and namespace.

The specification has the core components of the service. The externalTrafficPolicy property determines whether data will be distributed across the node or cluster. Set the property to local if you want the data to only be distributed within one node.

apiVersion: v1
kind: Service
metadata:
   name: my-service
   namespace: earth
   labels:
      app: nginx
spec:
   externalTrafficPolicy: Local
   ports:
   - name: http
     port: 80
     protocol: TCP
     targetPort: 80
   selector:
     app: nginx
   type: LoadBalancer

The last property in the configuration file is the service type. In this property you add your own Kubernetes service that is suitable for the type of traffic flow you want to facilitate in your cluster or node. Here are different Kubernetes services you can use:

1. ClusterIP service – The first type of Kubernetes service is the ClusterIP service. This is the default type of service and it provides an internal IP address that is only accessible within the cluster. This type of service is useful for applications that need to communicate with each other within the cluster, but don’t need to be exposed to the outside environment.
2. NodePort service – The second type of Kubernetes service is the NodePort service. This type of service exposes a specific port on each node in the cluster, allowing external traffic to access the service. This can be useful for applications that need to be accessed by users outside of the cluster, but still need to be managed by Kubernetes.
3. LoadBalancer service – The third type of Kubernetes service is the LoadBalancer service. This type of service exposes the application to the outside environment by creating a load balancer that distributes incoming traffic across the different components of the application. This is useful for applications that need to handle a large amount of traffic or need to be highly available.
4. ExternalName service – The fourth type of Kubernetes service is the ExternalName service. This type of service maps an external DNS name to a service within the cluster. This can be useful for accessing services that are external to the cluster, but still need to be managed by Kubernetes.
5. Headless service – The fifth type of Kubernetes service is the Headless service. This type of service is similar to a ClusterIP service, but it does not have a virtual IP address. Instead, it exposes the individual endpoints of the application, allowing direct communication with the underlying components of the application.

How to Protect Kubernetes Services

In this section, I will discuss some of the different techniques you can use to protect your Kubernetes services:

Using Network Policies

Ingoing and outgoing cluster traffic can carry both good and malicious content. Analyzing and filtering this content will help you to catch unwanted and unauthorized functions and scripts. In Kubernetes, there is a mechanism called NetworkPolicies which gives you control over what goes in and out of your cluster.

NetworkPolicies allow you to specify which services are allowed to communicate with each other, and that are not. This helps to prevent unauthorized access to your services and can improve the overall security of your Kubernetes cluster.

To implement network policies, you can use the Kubernetes API to define rules that specify which services are allowed to communicate with each other. These rules can be defined using labels and selectors, which enable you to specify which services the rules apply to. Once the rules are defined, they can be applied to your cluster using the kubectl command-line tool.

Network policies are a platform governance solution since they control communication access between services both internally and externally.

Kubernetes vulnerabilities can be exploited by cyberattackers which leads to internal services being used to transfer malicious scripts to other pods. Do not trust any service whether internally or externally. No one or no component has to be trusted without passing a security audit.

It is very important to make sure that network policies are immediately implemented before applying a service. Every service has to be monitored and controlled.

Network policies use the resource kind which is NetworkPolicy. Here are some interesting facts you should know about NetworkPolicies:

• Policies are attached to pods using label selectors and they are namespace scoped.
• Policy rule controls what goes in and out of the cluster by specifying protocols and ports. Policies control traffic at the port and IP address level.

Ingress facilitates traffic that goes into the cluster while the egress facilitates the traffic flow that goes out of the pod and cluster. By default inbound and outbound traffic is allowed until you set a NetworkPolicy.

Implementing the RBAC Mechanism

Services are a critical component in Kubernetes as they connect resources and open the gates for outgoing and incoming traffic. If they are configured by the wrong person, they could spell disaster.

In addition to network policies, you can also use authentication and access control mechanisms to control access to your Kubernetes services. For example, you can use Role-Based Access Control (RBAC) to assign various levels of access to different users. By using these mechanisms, you can ensure that only authorized users have access to your services and can help to prevent unauthorized access.

The RBAC mechanism has roles that define actions a user can do on a service in a specific namespace. These actions are called verbs, for example, the list verb allows the user to list all of the available services.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
   name: service-access-role
   namespace: redgate
rules:
   - apiGroups:
      - apps
      - autoscaling
      - batch
      - extensions
      - policy
      - rbac.authorization.k8s.io
   resources:
      - namespaces
      - services
   verbs: ["get", "list", "watch", "create", "delete"]

Roles are coupled with RoleBindings which state the users or subjects that are being given the permissions stated in the role. In this case, the network-service-account is being given the permissions in the previous role.

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
   name: service-rolebinding
   namespace: redgate
roleRef:
   apiGroup: rbac.authorization.k8s.io
   kind: Role
   name: service-access-role
subjects:
-  namespace: redgate
   kind: ServiceAccount
   name: network-service-account

Implementing Firewall

Implementing a firewall and NetworkPolicy side by side is important. When your applications are in production a firewall tracks and filters traffic to catch malicious activities while a NetworkPolicy controls access to your cluster. A firewall prevents data leaks from happening.

Monitoring Traffic

Observability and performance monitoring are crucial as they give you an insight on how your services are performing and spot services that are failing to communicate properly. Metrics and logs give you more details that help you debug NetworkPolicies and components that have issues. Being able to identify issues before attackers spot vulnerabilities and exploit them is crucial.

Auditing Components

Since Kubernetes does not have an inbuilt CNI (a Container Network Interface), it is very important to make sure that the CNIs you download and install in your cluster are safe and secure. Third party components do come with insecurities that can add flaws to your network architecture. Use trusted and verified components. Most of all, install updates immediately after they have been released, don’t wait for issues to remind you that you are using an outdated version. Up to date versions alway come with security patches.

Conclusion

This article served as an introduction to five Kubernetes services and various ways you can use to protect them. Kubernetes services have to be protected and regulated at all entries and configurations. There are many ways you can use to protect your services besides RBAC and NetworkPolicies. But, the techniques discussed in this article are the founding principles of keeping services secure. Having control over what goes in and out internally and externally of your cluster is the best vulnerability prevention exercise you can execute.

 

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