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Access and identity options for AKS enabled by Azure Arc

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Applies to: AKS on Azure Stack HCI 23H2

You can authenticate, authorize, secure, and control access to Kubernetes clusters in various ways:

Kubernetes RBAC and Azure RBAC help you secure your cluster access and provide only the minimum required permissions to developers and operators.

This article introduces the core concepts that help you authenticate and assign permissions in AKS.

Kubernetes RBAC

Kubernetes RBAC provides granular filtering of user actions. With this control mechanism:

  • You assign users or user groups permission to create and modify resources or view logs from running application workloads.
  • You can scope permissions to a single namespace or across the entire AKS cluster.
  • You create roles to define permissions, and then assign those roles to users with role bindings.

For more information, see Using Kubernetes RBAC authorization.

Roles and ClusterRoles

Roles

Before assigning permissions to users with Kubernetes RBAC, you define user permissions as a role. Grant permissions within a Kubernetes namespace using roles.

Kubernetes roles grant permissions; they don't deny permissions. To grant permissions across the entire cluster or to cluster resources outside a given namespace, you can use ClusterRoles.

ClusterRoles

A ClusterRole grants and applies permissions to resources across the entire cluster, not a specific namespace.

RoleBindings and ClusterRoleBindings

Once you define roles to grant permissions to resources, you assign those Kubernetes RBAC permissions with a RoleBinding. If your AKS cluster integrates with Microsoft Entra ID, RoleBindings grant permissions to Microsoft Entra users to perform actions within the cluster. See Control access using Microsoft Entra ID and Kubernetes RBAC

RoleBindings

Assign roles to users for a given namespace using RoleBindings. With RoleBindings, you can logically segregate a single AKS cluster, only enabling users to access the application resources in their assigned namespace.

To bind roles across the entire cluster, or to cluster resources outside a given namespace, use ClusterRoleBindings.

ClusterRoleBinding

With a ClusterRoleBinding, you bind roles to users and apply to resources across the entire cluster, not a specific namespace. This approach lets you grant administrators or support engineers access to all resources in the AKS cluster.

Kubernetes service accounts

Service accounts are one of the primary user types in Kubernetes. The Kubernetes API holds and manages service accounts. Service account credentials are stored as Kubernetes secrets, allowing them to be used by authorized pods to communicate with the API server. Most API requests provide an authentication token for a service account or a normal user account.

Normal user accounts allow more traditional access for human administrators or developers, not just services and processes. While Kubernetes doesn't provide an identity management solution to store regular user accounts and passwords, you can integrate external identity solutions into Kubernetes. For AKS clusters, this integrated identity solution is Microsoft Entra ID.

For more information about the identity options in Kubernetes, see Kubernetes authentication.

Azure role-based access control

Azure Role-based Access Control (RBAC) is an authorization system built on Azure Resource Manager that provides fine-grained access management of Azure resources.

RBAC system Description
Kubernetes RBAC Designed to work on Kubernetes resources within your AKS cluster.
Azure RBAC Designed to work on resources within your Azure subscription.

With Azure RBAC, you create a role definition that outlines the permissions to be applied. You then assign a user or group this role definition via a role assignment for a particular scope. The scope can be an individual resource, a resource group, or across the subscription.

For more information, see What is Azure role-based access control (Azure RBAC)?

There are two required levels of access to fully operate an AKS Arc cluster:

  • Access the AKS resource in your Azure subscription.
    • Control scaling or upgrading your cluster using the AKS enabled by Azure Arc APIs.
    • Pull your admin, certificate-based kubeconfig.
    • Pull your Entra ID enabled kubeconfig.
  • Access to the Kubernetes API. This access is controlled by either:
    • Kubernetes RBAC, or
    • Integrating Azure RBAC with AKS for Kubernetes authorization.

Azure RBAC to authorize access to the AKS resource

With Azure RBAC, you can provide your users (or identities) with granular access to AKS resources across one or more subscriptions. There are three roles available for this control plane action: Azure Kubernetes Service Arc Cluster Admin Role, Azure Kubernetes Service Arc Cluster User Role, and Azure Kubernetes Service Arc Contributor Role. Each role has a different permission scope as described in Azure built-in roles for Containers. For example, you can use the Azure Kubernetes Service Arc Contributor role to create, scale, and upgrade your cluster. Meanwhile, another user with the Azure Kubernetes Service Arc Cluster Admin role only has permission to pull the admin kubeconfig.

Azure RBAC for Kubernetes authorization

With the Azure RBAC integration, AKS uses a Kubernetes authorization webhook server so you can manage Microsoft Entra integrated Kubernetes cluster resource permissions and assignments using Azure role definition and role assignments.

Diagram of authorization flow.

As shown in this diagram, when using the Azure RBAC integration, all requests to the Kubernetes API follow the same authentication flow as described in Microsoft Entra integration.

If the identity making the request exists in Microsoft Entra ID, Azure teams with Kubernetes RBAC to authorize the request. If the identity exists outside of Microsoft Entra ID (for example, a Kubernetes service account), authorization defers to the normal Kubernetes RBAC.

In this scenario, you use Azure RBAC mechanisms and APIs to assign users built-in roles or create custom roles, just as you would with Kubernetes roles.

With this feature, you not only give users permissions to the AKS resource across subscriptions, but you also configure the role and permissions for inside each of those clusters controlling Kubernetes API access. There are four built-in roles available for this data plane action, each with its own scope of permissions, as described in the built-in roles section.

Important

You must enable Azure RBAC for Kubernetes authorization before doing role assignment. For more details and step by step guidance, see Use Azure RBAC for Kubernetes authorization.

Built-in roles

AKS enabled by Arc provides the following five built-in roles. They are similar to the Kubernetes built-in roles with a few differences, such as supporting CRDs. See the full list of actions allowed by each Azure built-in role.

Role Description
Azure Arc-enabled Kubernetes Cluster User Allows you to retrieve the Cluster Connect-based kubeconfig file to manage clusters from anywhere.
Azure Arc Kubernetes Viewer Allows read-only access to see most objects in a namespace.
Doesn't allow viewing secrets, because read permission on secrets enables access to ServiceAccount credentials in the namespace. These credentials in turn allow API access through that ServiceAccount value (a form of privilege escalation).
Azure Arc Kubernetes Writer Allows read/write access to most objects in a namespace.
Doesn't allow viewing or modifying roles or role bindings. However, this role allows accessing secrets and running pods as any ServiceAccount value in the namespace, so it can be used to gain the API access levels of any such ServiceAccount value in the namespace.
Azure Arc Kubernetes Admin Allows admin access. It's intended to be granted within a namespace through RoleBinding. If you use it in RoleBinding, it allows read/write access to most resources in a namespace, including the ability to create roles and role bindings within the namespace. This role doesn't allow write access to resource quota or to the namespace itself.
Azure Arc Kubernetes Cluster Admin Allows "superuser" access to execute any action on any resource. When you use it in ClusterRoleBinding, it gives full control over every resource in the cluster and in all namespaces. When you use it in RoleBinding, it gives full control over every resource in the role binding namespace, including the namespace itself.

Microsoft Entra integration

Enhance your AKS cluster security with Microsoft Entra integration. Built on enterprise identity management experience, Microsoft Entra ID is a multitenant, cloud-based directory and identity management service that combines core directory services, application access management, and identity protection. With Microsoft Entra ID, you can integrate on-premises identities into AKS clusters to provide a single source for account management and security.

Flowchart showing Entra integration.

With Microsoft Entra-integrated AKS clusters, you can grant users or groups access to Kubernetes resources within a namespace or across the cluster.

  • To obtain a kubectl configuration context, run the az aksarc get-credentials command.
  • When a user interacts with the AKS cluster using kubectl, they're prompted to sign in with their Microsoft Entra credentials.

This approach provides a single source for user account management and password credentials. The user can only access the resources as defined by the Kubernetes cluster administrator.

Microsoft Entra authentication is provided to AKS clusters with OpenID Connect. OpenID Connect is an identity layer built on top of the OAuth 2.0 protocol. For more information about OpenID Connect, see the OpenID Connect documentation. From inside the Kubernetes cluster, Webhook Token Authentication is used to verify authentication tokens. Webhook token authentication is configured and managed as part of the AKS cluster.

Summary

The following table contains a summary of how users can authenticate to Kubernetes when Microsoft Entra integration is enabled. In all cases, the sequence of commands is:

  1. Run az login to authenticate to Azure.
  2. Run az aksarc get-credentials to download credentials for the Kubernetes cluster into .kube/config.
  3. Run kubectl commands.
    • The first command can trigger browser-based authentication to authenticate to the Kubernetes cluster, as described in the following table.
Description Role grant required Cluster admin Microsoft Entra groups When to use
Admin login using client certificate Azure Kubernetes Service Arc Cluster Admin Role. This role allows az aksarc get-credentials to be used with the --admin flag, which downloads a non-Microsoft Entra cluster admin certificate into the user's .kube/config. This is the only purpose of the Azure Kubernetes Admin role. n/a If you're permanently blocked by not having access to a valid Microsoft Entra group with access to your cluster.
Microsoft Entra ID with manual (cluster) RoleBindings Azure Kubernetes Service Arc Cluster User Role. The User role allows az aksarc get-credentials to be used without the --admin flag. This is the only purpose of the Azure Kubernetes Service Cluster User role.) The result, on a Microsoft Entra ID-enabled cluster, is the download of an empty entry into .kube/config, which triggers browser-based authentication when it's first used by kubectl. Because the user is not in any Cluster Admin group, their rights are controlled entirely by any RoleBindings or ClusterRoleBindings that are set up by cluster admins. The (Cluster) RoleBindings nominate Microsoft Entra users or Microsoft Entra groups as their subjects. If no such bindings were set up, the user can't excute any kubectl commands. If you want fine-grained access control, and you're not using Azure RBAC for Kubernetes Authorization. Note that the user who sets up the bindings must sign in using one of the other methods listed in this table.
Microsoft Entra ID by member of cluster admin Microsoft Entra group (set using --aad-admin-group-object-ids flag in Azure CLI) Same as previous. User is a member of one of the groups listed here. AKS automatically generates a ClusterRoleBinding that binds all of the listed groups to the cluster-admin Kubernetes role. So users in these groups can run all kubectl commands as cluster-admin. If you want to grant users full admin rights, and are not using Azure RBAC for Kubernetes authorization.
Microsoft Entra ID with Azure RBAC for Kubernetes authorization Two roles:
Azure Kubernetes Service Arc Cluster User role (as described previously).
One of the Azure Arc Kubernetes roles described previously, or your own custom alternative.		 The admin roles field on the Configuration tab is irrelevant when Azure RBAC for Kubernetes authorization is enabled. You use Azure RBAC for Kubernetes authorization. This approach gives you fine-grained control, without the need to set up RoleBindings or ClusterRoleBindings.

Next steps