Access and identity options for Azure Kubernetes Service (AKS)
There are different ways to authenticate with and secure Kubernetes clusters. Using role-based access controls (RBAC), you can grant users or groups access to only the resources they need. With Azure Kubernetes Service (AKS), you can further enhance the security and permissions structure by using Azure Active Directory. These approaches help you secure your application workloads and customer data.
This article introduces the core concepts that help you authenticate and assign permissions in AKS:
- Kubernetes service accounts
- Azure Active Directory integration
- Role-based access controls (RBAC)
- Roles and ClusterRoles
- RoleBindings and ClusterRoleBindings
Kubernetes service accounts
One of the primary user types in Kubernetes is a service account. A service account exists in, and is managed by, the Kubernetes API. The credentials for service accounts are stored as Kubernetes secrets, which allows 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. Kubernetes itself doesn't provide an identity management solution where regular user accounts and passwords are stored. Instead, external identity solutions can be integrated into Kubernetes. For AKS clusters, this integrated identity solution is Azure Active Directory.
For more information on the identity options in Kubernetes, see Kubernetes authentication.
Azure Active Directory integration
The security of AKS clusters can be enhanced with the integration of Azure Active Directory (AD). Built on decades of enterprise identity management, Azure AD is a multi-tenant, cloud-based directory, and identity management service that combines core directory services, application access management, and identity protection. With Azure AD, you can integrate on-premises identities into AKS clusters to provide a single source for account management and security.
With Azure AD-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, a user can run the az aks get-credentials command. When a user then interacts with the AKS cluster with
kubectl, they are prompted to sign in with their Azure AD 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 cluster administrator.
Azure AD authentication in AKS clusters uses OpenID Connect, an identity layer built on top of the OAuth 2.0 protocol. OAuth 2.0 defines mechanisms to obtain and use access tokens to access protected resources, and OpenID Connect implements authentication as an extension to the OAuth 2.0 authorization process. For more information on OpenID Connect, see the Open ID Connect documentation. To verify the authentication tokens obtained from Azure AD through OpenID Connect, AKS clusters use Kubernetes Webhook Token Authentication. For more information, see the Webhook Token Authentication documentation.
Role-based access controls (RBAC)
To provide granular filtering of the actions that users can perform, Kubernetes uses role-based access controls (RBAC). This control mechanism lets you assign users, or groups of users, permission to do things like create or modify resources, or view logs from running application workloads. These permissions can be scoped to a single namespace, or granted across the entire AKS cluster. With Kubernetes RBAC, you create roles to define permissions, and then assign those roles to users with role bindings.
For more information, see Using RBAC authorization.
Azure role-based access controls (RBAC)
One additional mechanism for controlling access to resources is Azure role-based access controls (RBAC). Kubernetes RBAC is designed to work on resources within your AKS cluster, and Azure RBAC is designed to work on resources within your Azure subscription. With Azure RBAC, you create a role definition that outlines the permissions to be applied. A user or group is then assigned this role definition for a particular scope, which could be an individual resource, a resource group, or across the subscription.
For more information, see What is Azure RBAC?
Roles and ClusterRoles
Before you assign permissions to users with Kubernetes RBAC, you first define those permissions as a Role. Kubernetes roles grant permissions. There is no concept of a deny permission.
Roles are used to grant permissions within a namespace. If you need to grant permissions across the entire cluster, or to cluster resources outside a given namespace, you can instead use ClusterRoles.
A ClusterRole works in the same way to grant permissions to resources, but can be applied to resources across the entire cluster, not a specific namespace.
RoleBindings and ClusterRoleBindings
Once roles are defined to grant permissions to resources, you assign those Kubernetes RBAC permissions with a RoleBinding. If your AKS cluster integrates with Azure Active Directory, bindings are how those Azure AD users are granted permissions to perform actions within the cluster.
Role bindings are used to assign roles for a given namespace. This approach lets you logically segregate a single AKS cluster, with users only able to access the application resources in their assigned namespace. If you need to bind roles across the entire cluster, or to cluster resources outside a given namespace, you can instead use ClusterRoleBindings.
A ClusterRoleBinding works in the same way to bind roles to users, but can be applied 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.
To get started with Azure AD and Kubernetes RBAC, see Integrate Azure Active Directory with AKS.
For associated best practices, see Best practices for authentication and authorization in AKS.
For additional information on core Kubernetes and AKS concepts, see the following articles: