Authentication in Azure Kubernetes Service (AKS) explained

Securing your Azure Kubernetes Service (AKS) cluster is paramount, and understanding the available authentication methods is a critical first step. This post dives deep into the three primary authentication approaches for AKS, outlining their pros, cons, and recommended use cases.

The Three Authentication Modes

1. Local Account with Kubernetes RBAC (Default)
   • Description: This is the default and least secure option. It lacks any direct integration with Microsoft Entra ID (formerly Azure Active Directory) or Azure. While authentication can be done with built-in Kubernetes tools, it’s generally complex and cumbersome.
   • Disadvantages:
   • Insecure: Access tokens stored unencrypted in kubeconfig files pose a significant security risk. A stolen kubeconfig can grant an attacker full cluster control.
   • Difficult User Management: No direct link between Entra ID users/groups and Kubernetes, making user management challenging.
   • Poor Auditing: Tracking who is accessing the cluster and what actions they perform is difficult, as access often defaults to a generic admin user. - Recommendation: Not recommended for most scenarios, especially in production environments, unless your users are not managed within your Entra ID, which is a rare edge case.
2. Microsoft Entra ID Authentication with Kubernetes RBAC
   • Description: This method leverages Azure for authentication and Kubernetes for authorization. Users authenticate using their Entra ID credentials, and their permissions within the cluster are then defined by Kubernetes role bindings.
   • Advantages: Easier to manage than local accounts because it integrates with Azure users or groups for authentication.
   • Disadvantages:
   • Setup Complexity: Requires creating and managing roles and role bindings directly within Kubernetes, which can become complex for granular permissions.
   • Auditing Challenges: Auditing can still be difficult as it relies on group or user IDs that require lookup in Entra ID to fully identify users. - Recommendation: Recommended for scenarios where you need portable clusters and prefer to keep rule bindings contained within the cluster itself.
3. Microsoft Entra ID Authentication with Azure RBAC (Most Secure & Recommended)
   • Description: This is the most secure and highly recommended option, as both authentication and authorization are managed entirely within Azure using Azure RBAC.
   • Advantages:
   • Centralized Management & Auditing: All permissions are visible and manageable directly within the Azure portal or CLI, greatly simplifying auditing and compliance.
   • Ease of Use: Azure provides convenient built-in Kubernetes roles (e.g., admin, reader, writer), simplifying permission assignment. Custom roles can also be created for specific needs.
   • Granular Control: Permissions can be assigned at various scopes, from the entire cluster down to specific namespaces. - Implementation:
   • Assign the Azure Kubernetes Service Cluster Admin role for full cluster access.
   • Use Azure CLI for more granular, namespace-level permissions.
   • Users or groups need the Azure Kubernetes Service Cluster User role to download the kubeconfig file. - Recommendation: This is the easiest to manage, most secure, and Microsoft-recommended way to access and manage an AKS cluster.

Practical Demonstrations

The video includes practical demonstrations of setting up each authentication method, showcasing how to create clusters, configure access, and test permissions using kubectl commands. It vividly illustrates the security vulnerabilities of the local account method by demonstrating how an attacker can gain full control of a cluster with a stolen kubeconfig file.

Conclusion

Choosing the right authentication method for your AKS cluster is a critical security decision. While the local account option is the default, it should almost always be avoided in favor of Microsoft Entra ID integration. For the highest level of security, ease of management, and comprehensive auditing, Microsoft Entra ID Authentication with Azure RBAC stands out as the clear winner and the recommended approach for most production AKS environments. This method centralizes your identity and access management, aligning perfectly with modern cloud security best practices.

You can find all the code sample on GitHub.

This post was AI-generated based on the transcript of the video “Authentication in Azure Kubernetes Service (AKS) explained” and reviewed by me.

Video - Authentication in Azure Kubernetes Service (AKS) explained