44134 - Pentesting Tiller (Helm)

👉 Overview

👀 What ?

Pentesting Tiller (Helm) is a process of conducting an authorized simulated attack on a system or network that uses Tiller (Helm) to assess its security weakness. Tiller (Helm) is a package manager for Kubernetes. Its goal is to simplify the deployment of applications and services to Kubernetes clusters.

🧐 Why ?

Pentesting Tiller (Helm) is crucial because Kubernetes has become the de-facto standard for running containerized services and applications in the cloud, and Tiller (Helm) is often used to manage such deployments. A weak configuration or poorly managed Tiller (Helm) instance can expose the entire Kubernetes cluster to risk, leading to potential data breaches or server takeovers.

⛏️ How ?

Pentesting Tiller (Helm) involves a step by step process. First, you need to identify running Tiller instances in the Kubernetes cluster. Then, check if Tiller is protected by any authentication methods. If not, or if you can bypass the authentication, you can then interact with Tiller to list, install or delete Helm charts, potentially leading to unauthorized access to applications running in the Kubernetes cluster. Using tools like kube-hunter or kube-bench can help automate some of these steps.

⏳ When ?

Pentesting Tiller (Helm) should be done regularly, especially before deploying a new application or after major changes to the Kubernetes cluster. Regular pentesting can help identify and fix security vulnerabilities before they can be exploited by attackers.

⚙️ Technical Explanations

Tiller (Helm) is a critical component of the Kubernetes system that manages the lifecycle of applications defined by Helm Charts. Given its high level of access within the Kubernetes cluster, it is a prime target for potential attackers.

In a penetration test (pentest), the tester simulates an attack to identify potential vulnerabilities in the Tiller setup. The process begins with the tester attempting to interact with Tiller in the same way an attacker would. They observe the system's behavior, looking specifically for any misconfigurations. This could include instances where Tiller is run as a root user, or when Tiller's gRPC endpoint is exposed without proper authentication in place. Both scenarios could provide an attacker with unauthorized access to the system.

Once these vulnerabilities are identified, the tester tries to exploit them. This could involve gaining unauthorized access to the system or escalating their privileges within it. Importantly, these actions are carried out in a controlled and ethical manner.

The ultimate goal of the pentest is not to cause harm, but to identify and understand potential weaknesses in the system's security. The findings from the pentest are then used to strengthen the Tiller setup's security, thus reducing the risk of a successful attack. This could involve modifying configurations, updating security protocols, or even changing aspects of the system architecture.

Regular pentesting is crucial in maintaining strong security, especially considering the evolving nature of cyber threats. It is recommended to conduct pentests frequently, particularly before deploying a new application or after making significant changes to the Kubernetes cluster.

Let's consider a simplified educational example of a Pentest on Tiller (Helm) within a Kubernetes cluster.

Step 1: Identifying Tiller Instances

First, we need to identify running Tiller instances in the Kubernetes cluster. Here, we can use the kubectl command:

$ kubectl -n kube-system get pods | grep tiller

This will return a list of running Tiller instances in the kube-system namespace.

Step 2: Checking Tiller's Authentication

Second, we'll check if Tiller is protected by any authentication methods. We can try to list Helm releases, which should be denied if proper authentication is in place.

$ helm list

If the command returns a list of releases without requiring authentication, there might be a security issue.

Step 3: Interacting with Tiller

If no proper authentication is present, or if we managed to bypass it, we can interact with Tiller. For instance, we can install a new Helm chart:

$ helm install stable/nginx

This command tries to install the nginx chart from the stable repository. If it succeeds without requiring authentication, there's a significant security concern.

Step 4: Documenting Findings

All these steps, their results, and potential security concerns are documented. The goal is to provide comprehensive feedback to the system administrators for them to understand potential vulnerabilities and address them accordingly.

Remember, this example is highly simplified and for educational purposes. In a real-world scenario, pentesting Tiller (Helm) involves more complex and diverse strategies, including using automated tools like kube-hunter or kube-bench. It should also be performed by a trained cybersecurity professional to ensure the testing process does not inadvertently harm the system.