Kubernetes has emerged as the leading platform for orchestrating containerized applications. However, developers and administrators rely on an ecosystem of tools and platforms that have emerged around Kubernetes. One of these tools is Helm, a package manager that simplifies Kubernetes deployments. However, with the convenience and efficiency Helm offers, it also introduces significant security risks.
This article explores the risks associated with Kubernetes Helm charts and provides actionable strategies to mitigate potential vulnerabilities. Understanding and addressing these security challenges is crucial for maintaining a robust, secure Kubernetes environment.
What Are Kubernetes Helm Charts?
Helm is the package manager for Kubernetes that allows developers and operators to easily package, configure, and deploy applications and services in Kubernetes clusters. Helm charts are packages of pre-configured Kubernetes resources.
A Helm chart is a collection of files that describe a related set of Kubernetes resources. It organizes these files into a structure that defines how to deploy a single application or an entire system. This makes Helm Charts a powerful tool for Kubernetes deployments, allowing developers and operators to manage complex applications with ease.
However, despite the convenience and power of Kubernetes Helm Charts, there are inherent security risks associated with them. If not addressed and mitigated, these risks can lead to consequences such as insecure default settings, dependencies on external sources, insufficient access controls, and embedded secrets.
Four Security Risks in Helm Charts
1. Insecure Default Settings
One of the most common security risks associated with Kubernetes Helm Charts is insecure default settings. Many Helm charts come with their default settings tailored for ease of use and quick startup rather than security. These settings may leave the application and the Kubernetes cluster vulnerable to attacks.
For instance, a Helm chart may be configured by default to run containers as root or with privileged access. This could potentially give an attacker the ability to execute arbitrary code within the container, compromising the entire system. Similarly, some charts may have insecure network policies that allow all incoming and outgoing traffic, potentially exposing the application to external threats.
2. Dependencies and External Sources
Helm charts often depend on other charts or Docker images from external repositories. If these dependencies are not carefully managed, they can introduce vulnerabilities in the application and the Kubernetes cluster.
For instance, a Docker image from an unreliable source could contain malicious code or contain outdated libraries with known vulnerabilities. Similarly, a dependent chart from an untrusted source could introduce insecure configurations or hidden threats. As a result, it's critical to ensure that all dependencies come from trusted sources and are kept up-to-date.
3. Insufficient Access Controls
Insufficient access controls represent another major security risk in Helm Charts. Kubernetes, by design, is a multi-user environment where different users or groups can have different levels of access to the cluster. However, not all Helm charts are designed with this in mind.
Some charts do not adequately define roles and permissions, allowing users to perform actions beyond their intended scope. This could potentially allow a malicious user to escalate their privileges and gain unauthorized access to sensitive resources. Moreover, some charts do not isolate resources effectively, potentially allowing a user or a compromised application to affect other resources within the cluster.
4. Embedded Secrets
One of the most overlooked security risks in Helm Charts is embedded secrets. These can include API keys, passwords, and certificates that are required for the application to function. If these are embedded in the Helm chart, they could potentially be exposed to unauthorized users or leaked in logs.
For instance, if sensitive data is defined in a Helm chart, it will be included in the chart's package and could be easily viewed by anyone with access to the chart or the Helm repository. Similarly, if logged during the application's runtime, these secrets could be read by anyone with access to the logs.
Best Practices for Securing Helm Charts
Here are a few things you can do to address Helm security concerns:
Ensure the Security of External Dependencies
When using external dependencies, always source them from trusted repositories. It's advisable to review the source code of these dependencies whenever possible to ensure there are no hidden vulnerabilities or threats. Never use a Helm chart without understanding what dependencies it includes and ensuring they are safe.
Also, consider using a vulnerability scanner to automatically detect any potential security risks in these dependencies. Such scanners could identify Common Vulnerabilities and Exposures (CVEs) that might be present in the external dependencies, enabling you to address them before they become a problem.
Implementing Robust Access Control
Make use of the built-in Role-Based Access Control (RBAC) feature in Kubernetes to limit who can install and manage Helm Charts in your environment. RBAC allows you to define roles with specific permissions and assign these roles to users or groups. Also, ensure that Helm charts themselves apply the correct access controls for resources they deploy within the Kubernetes environment.
Validate and Sanitize Inputs to Helm Charts
Input validation is another important measure in securing Helm Charts. Since Helm Charts often accept input from users or other systems, there is a risk that these inputs could be manipulated to execute malicious commands.
To mitigate this risk, always validate any inputs to your Helm Charts. This includes ensuring that the input is of the expected type, is within the expected range, and does not contain any malicious code. Also, sanitize inputs to ensure they do not execute unintended commands. Sanitization involves cleaning the input data to remove or neutralize any potentially harmful elements.
Use Secrets Management Tools
Hardcoding secrets, such as API keys or passwords, in your Helm Charts is a significant security risk. Instead of hardcoding secrets, use external secret management tools like HashiCorp Vault or the Secrets object in Kubernetes. These tools securely store and manage secrets, providing them to your applications as needed. Also, ensure that secrets are encrypted both at rest and in transit to further enhance their security.
Regularly Audit and Update Helm Charts
Regularly audit and update your Helm Charts. Over time, new vulnerabilities may be discovered in the tools and dependencies your charts rely on.
Regular auditing of your Helm Charts will help to identify these potential vulnerabilities. These audits should include checking for updates to your dependencies, reviewing your access controls, and validating your inputs and secrets management.
Additionally, regularly update your Helm Charts to incorporate the latest security patches and improvements. This will help ensure that your applications remain secure as new threats emerge.
While Kubernetes Helm Charts can introduce security risks, these risks can be effectively managed through best practices. By ensuring the security of external dependencies, implementing robust access control, validating and sanitizing inputs, using external secrets management tools, and regularly auditing and updating your charts, you can create a more secure Kubernetes environment.
Editor’s Note: The opinions expressed in this guest author article are solely those of the contributor and do not necessarily reflect those of Tripwire.
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