Use Azure role-based access control to define access to the Kubernetes configuration file in Azure Kubernetes Service (AKS)

Grein
08/01/2024

You can interact with Kubernetes clusters using the kubectl tool. The Azure CLI provides an easy way to get the access credentials and kubeconfig configuration file to connect to your AKS clusters using kubectl. You can use Azure role-based access control (Azure RBAC) to limit who can get access to the kubeconfig file and the permissions they have.

This article shows you how to assign Azure roles that limit who can get the configuration information for an AKS cluster.

Before you begin

This article assumes that you have an existing AKS cluster. If you need an AKS cluster, create one using Azure CLI, Azure PowerShell, or the Azure portal.
This article also requires that you're running Azure CLI version 2.0.65 or later. Run az --version to find the version. If you need to install or upgrade, see Install Azure CLI.

Available permissions for cluster roles

When you interact with an AKS cluster using the kubectl tool, a configuration file, called kubeconfig, defines cluster connection information. This configuration file is typically stored in ~/.kube/config. Multiple clusters can be defined in this kubeconfig file. You can switch between clusters using the kubectl config use-context command.

The az aks get-credentials command lets you get the access credentials for an AKS cluster and merges these credentials into the kubeconfig file. You can use Azure RBAC to control access to these credentials. These Azure roles let you define who can retrieve the kubeconfig file and what permissions they have within the cluster.

There are two Azure roles you can apply to a Microsoft Entra user or group:

Azure Kubernetes Service Cluster Admin Role
- Allows access to Microsoft.ContainerService/managedClusters/listClusterAdminCredential/action API call. This API call lists the cluster admin credentials.
- Downloads kubeconfig for the clusterAdmin role.
Azure Kubernetes Service Cluster User Role
- Allows access to Microsoft.ContainerService/managedClusters/listClusterUserCredential/action API call. This API call lists the cluster user credentials.
- Downloads kubeconfig for clusterUser role.

Note

On clusters that use Microsoft Entra ID, users with the clusterUser role have an empty kubeconfig file that prompts a login. Once logged in, users have access based on their Microsoft Entra user or group settings. Users with the clusterAdmin role have admin access.

On clusters that don't use Microsoft Entra ID, the clusterUser role has same effect of clusterAdmin role.

Assign role permissions to a user or group

To assign one of the available roles, you need to get the resource ID of the AKS cluster and the ID of the Microsoft Entra user account or group using the following steps:

Get the cluster resource ID using the az aks show command for the cluster named myAKSCluster in the myResourceGroup resource group. Provide your own cluster and resource group name as needed.
Use the az account show and az ad user show commands to get your user ID.
Assign a role using the az role assignment create command.

The following example assigns the Azure Kubernetes Service Cluster Admin Role to an individual user account:

# Get the resource ID of your AKS cluster
AKS_CLUSTER=$(az aks show --resource-group myResourceGroup --name myAKSCluster --query id -o tsv)

# Get the account credentials for the logged in user
ACCOUNT_UPN=$(az account show --query user.name -o tsv)
ACCOUNT_ID=$(az ad user show --id $ACCOUNT_UPN --query objectId -o tsv)

# Assign the 'Cluster Admin' role to the user
az role assignment create \
    --assignee $ACCOUNT_ID \
    --scope $AKS_CLUSTER \
    --role "Azure Kubernetes Service Cluster Admin Role"

If you want to assign permissions to a Microsoft Entra group, update the --assignee parameter shown in the previous example with the object ID for the group rather than the user.

To get the object ID for a group, use the az ad group show command. The following command gets the object ID for the Microsoft Entra group named appdev:

az ad group show --group appdev --query objectId -o tsv

Important

In some cases, such as Microsoft Entra guest users, the user.name in the account is different than the userPrincipalName.

$ az account show --query user.name -o tsv
user@contoso.com

$ az ad user list --query "[?contains(otherMails,'user@contoso.com')].{UPN:userPrincipalName}" -o tsv
user_contoso.com#EXT#@contoso.onmicrosoft.com

In this case, set the value of ACCOUNT_UPN to the userPrincipalName from the Microsoft Entra user. For example, if your account user.name is user@contoso.com, this action would look like the following example:

ACCOUNT_UPN=$(az ad user list --query "[?contains(otherMails,'user@contoso.com')].{UPN:userPrincipalName}" -o tsv)

Get and verify the configuration information

Once the roles are assigned, use the az aks get-credentials command to get the kubeconfig definition for your AKS cluster. The following example gets the --admin credentials, which works correctly if the user has been granted the Cluster Admin Role:

az aks get-credentials --resource-group myResourceGroup --name myAKSCluster --admin

You can then use the kubectl config view command to verify that the context for the cluster shows that the admin configuration information has been applied.

$ kubectl config view

Your output should look similar to the following example output:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://myaksclust-myresourcegroup-19da35-4839be06.hcp.eastus.azmk8s.io:443
  name: myAKSCluster
contexts:
- context:
    cluster: myAKSCluster
    user: clusterAdmin_myResourceGroup_myAKSCluster
  name: myAKSCluster-admin
current-context: myAKSCluster-admin
kind: Config
preferences: {}
users:
- name: clusterAdmin_myResourceGroup_myAKSCluster
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED
    token: e9f2f819a4496538b02cefff94e61d35

Remove role permissions

To remove role assignments, use the az role assignment delete command. Specify the account ID and cluster resource ID that you obtained in the previous steps. If you assigned the role to a group rather than a user, specify the appropriate group object ID rather than account object ID for the --assignee parameter.

az role assignment delete --assignee $ACCOUNT_ID --scope $AKS_CLUSTER

Next steps

For enhanced security on access to AKS clusters, integrate Microsoft Entra authentication.

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