Tutorial: Use a Windows VM system-assigned managed identity to access Azure Key Vault

Managed identities for Azure resources is a feature of Azure Active Directory. Each of the Azure services that support managed identities for Azure resources are subject to their own timeline. Make sure you review the availability status of managed identities for your resource and known issues before you begin.

This tutorial shows you how a Windows virtual machine (VM) can use a system-assigned managed identity to access Azure Key Vault. Serving as a bootstrap, Key Vault makes it possible for your client application to then use a secret to access resources not secured by Azure Active Directory (AD). Managed Service Identities are automatically managed by Azure and enable you to authenticate to services that support Azure AD authentication, without including authentication information in your code.

You learn how to:

  • Grant your VM access to a secret stored in a Key Vault
  • Get an access token using the VM identity and use it to retrieve the secret from Key Vault

Prerequisites

Create a Key Vault  

This section shows how to grant your VM access to a secret stored in a Key Vault. Using managed identities for Azure resources, your code can get access tokens to authenticate to resources that support Azure AD authentication.  However, not all Azure services support Azure AD authentication. To use managed identities for Azure resources with those services, store the service credentials in Azure Key Vault, and use the VM's managed identity to access Key Vault to retrieve the credentials.

First, we need to create a Key Vault and grant our VM’s system-assigned managed identity access to the Key Vault.

  1. Open the Azure portal

  2. At the top of the left navigation bar, select Create a resource

  3. In the Search the Marketplace box type in Key Vault and hit Enter.  

  4. Select Key Vault from the results.

  5. Select Create

  6. Provide a Name for the new Key Vault.

    Create a Key vault screen

  7. Fill out all required information making sure that you choose the subscription and resource group where you created the virtual machine that you are using for this tutorial.

  8. Select Review+ create

  9. Select Create

Create a secret

Next, add a secret to the Key Vault, so you can retrieve it later using code running in your VM. For the purpose of this tutorial, we are using PowerShell but the same concepts apply to any code executing in this virtual machine.

  1. Navigate to your newly created Key Vault.

  2. Select Secrets, and click Add.

  3. Select Generate/Import

  4. In the Create a secret screen from Upload options leave Manual selected.

  5. Enter a name and value for the secret.  The value can be anything you want. 

  6. Leave the activation date and expiration date clear, and leave Enabled as Yes

  7. Click Create to create the secret.

    Create a secret

Grant access

The managed identity used by the virtual machine needs to be granted access to read the secret that we will store in the Key Vault.

  1. Navigate to your newly created Key Vault

  2. Select Access Policy from the menu on the left side.

  3. Select Add Access Policy

    key vault create access policy screen

  4. In the Add access policy section under Configure from template (optional) choose Secret Management from the pull-down menu.

  5. Choose Select Principal, and in the search field enter the name of the VM you created earlier.  Select the VM in the result list and choose Select.

  6. Select Add

  7. Select Save.

Access data  

This section shows how to get an access token using the VM identity and use it to retrieve the secret from Key Vault. If you don’t have PowerShell 4.3.1 or greater installed, you'll need to download and install the latest version.

First, we use the VM’s system-assigned managed identity to get an access token to authenticate to Key Vault:  

  1. In the portal, navigate to Virtual Machines and go to your Windows virtual machine and in the Overview, click Connect.
  2. Enter in your Username and Password for which you added when you created the Windows VM.  
  3. Now that you have created a Remote Desktop Connection with the virtual machine, open PowerShell in the remote session.  
  4. In PowerShell, invoke the web request on the tenant to get the token for the local host in the specific port for the VM.  

The PowerShell request:

$Response = Invoke-RestMethod -Uri 'http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fvault.azure.net' -Method GET -Headers @{Metadata="true"} 

You can see what the response looks like below:

request with token response

Next, extract the access token from the response.  

   $KeyVaultToken = $Response.access_token

Finally, use PowerShell’s Invoke-WebRequest command to retrieve the secret you created earlier in the Key Vault, passing the access token in the Authorization header.  You’ll need the URL of your Key Vault, which is in the Essentials section of the Overview page of the Key Vault.  

Invoke-RestMethod -Uri https://<your-key-vault-URL>/secrets/<secret-name>?api-version=2016-10-01 -Method GET -Headers @{Authorization="Bearer $KeyVaultToken"}

The response will look like this: 

  value       id                                                                                    attributes
  -----       --                                                                                    ----------
  'My Secret' https://mi-lab-vault.vault.azure.net/secrets/mi-test/50644e90b13249b584c44b9f712f2e51 @{enabled=True; created=16…

Once you’ve retrieved the secret from the Key Vault, you can use it to authenticate to a service that requires a name and password.

Clean up resources

When you want to clean up the resources, visit the Azure portal, select Resource groups, locate, and select the resource group that was created in the process of this tutorial (such as mi-test), and then use the Delete resource group command.

Alternatively you may also do this via PowerShell or the CLI

Next steps

In this tutorial, you learned how to use a Windows VM system-assigned managed identity to access Azure Key Vault. To learn more about Azure Key Vault see: