Managed Service Identity (MSI) for Azure resources

Managed Service Identity (MSI) is a preview feature of Azure Active Directory. Make sure you review the known issues before you begin. For more information about previews, see Supplemental Terms of Use for Microsoft Azure Previews.

A common challenge when building cloud applications is how to manage the credentials that need to be in your code for authenticating to cloud services. Keeping these credentials secure is an important task. Ideally, they never appear on developer workstations or get checked into source control. Azure Key Vault provides a way to securely store credentials and other keys and secrets, but your code needs to authenticate to Key Vault to retrieve them. Managed Service Identity (MSI) makes solving this problem simpler by giving Azure services an automatically managed identity in Azure Active Directory (Azure AD). You can use this identity to authenticate to any service that supports Azure AD authentication, including Key Vault, without having any credentials in your code.

How does it work?

When you enable Managed Service Identity on an Azure service, Azure automatically creates an identity for the service instance in the Azure AD tenant used by your Azure subscription. Under the covers, Azure provisions the credentials for the identity onto the service instance. Your code can then make a local request to get access tokens for services that support Azure AD authentication. Azure takes care of rolling the credentials used by the service instance. If the service instance is deleted, Azure automatically cleans up the credentials and the identity in Azure AD.

Here's an example of how Managed Service Identity works with Azure Virtual Machines.

Virtual Machine MSI example

  1. Azure Resource Manager receives a message to enable MSI on a VM.
  2. Azure Resource Manager creates a Service Principal in Azure AD to represent the identity of the VM. The Service Principal is created in the Azure AD tenant that is trusted by this subscription.
  3. Azure Resource Manager configures the Service Principal details in the MSI VM Extension of the VM. This step includes configuring client ID and certificate used by the extension to get access tokens from Azure AD.
  4. Now that the Service Principal identity of the VM is known, it can be granted access to Azure resources. For example, if your code needs to call Azure Resource Manager, then you would assign the VM’s Service Principal the appropriate role using Role-Based Access Control (RBAC) in Azure AD. If your code needs to call Key Vault, then you would grant your code access to the specific secret or key in Key Vault.
  5. Your code running on the VM requests a token from a local endpoint that is hosted by the MSI VM extension: http://localhost:50342/oauth2/token. The resource parameter specifies the service to which the token is sent. For example, if you want your code to authenticate to Azure Resource Manager, you would use resource=https://management.azure.com/.
  6. The MSI VM Extension uses its configured client ID and certificate to request an access token from Azure AD. Azure AD returns a JSON Web Token (JWT) access token.
  7. Your code sends the access token on a call to a service that supports Azure AD authentication.

Each Azure service that supports Managed Service Identity has its own method for your code to obtain an access token. Check out the tutorials for each service to find out the specific method to get a token.

Try Managed Service Identity

Try a Managed Service Identity tutorial to learn end-to-end scenarios for accessing different Azure resources:

From MSI-enabled resource Learn how to
Azure VM (Windows) Access Azure Data Lake Store with a Windows VM Managed Service Identity
Access Azure Resource Manager with a Windows VM Managed Service Identity
Access Azure SQL with a Windows VM Managed Service Identity
Access Azure Storage via access key with a Windows VM Managed Service Identity
Access Azure Storage via SAS with a Windows VM Managed Service Identity
Access a non-Azure AD resource with a Windows VM Managed Service Identity and Azure Key Vault
Azure VM (Linux) Access Azure Data Lake Store with a Linux VM Managed Service Identity
Access Azure Resource Manager with a Linux VM Managed Service Identity
Access Azure Storage via access key with a Linux VM Managed Service Identity
Access Azure Storage via SAS with a Linux VM Managed Service Identity
Access a non-Azure AD resource with a Linux VM Managed Service Identity and Azure Key Vault
Azure App Service Use Managed Service Identity with Azure App Service or Azure Functions
Azure Function Use Managed Service Identity with Azure App Service or Azure Functions

Which Azure services support Managed Service Identity?

Azure services that support Managed Service Identity can use MSI to authenticate to services that support Azure AD authentication. We are in the process of integrating MSI and Azure AD authentication across Azure. Check back often for updates.

Azure services that support Managed Service Identity

The following Azure services support Managed Service Identity.

Service Status Date Configure Get a token
Azure Virtual Machines Preview September 2017 Azure portal
PowerShell
Azure CLI
Azure Resource Manager templates
REST
.NET
Bash/Curl
Go
PowerShell
Azure App Service Preview September 2017 Azure portal
Azure Resource Manager template
.NET
REST
Azure Functions Preview September 2017 Azure portal
Azure Resource Manager template
.NET
REST
Azure Data Factory V2 Preview November 2017 Azure portal
PowerShell
REST
SDK

Azure services that support Azure AD authentication

The following services support Azure AD authentication, and have been tested with client services that use Managed Service Identity.

Service Resource ID Status Date Assign access
Azure Resource Manager https://management.azure.com/ Available September 2017 Azure portal
PowerShell
Azure CLI
Azure Key Vault https://vault.azure.net/ Available September 2017
Azure Data Lake https://datalake.azure.net/ Available September 2017
Azure SQL https://database.windows.net/ Available October 2017
Azure Event Hubs https://eventhubs.azure.net/ Available December 2017
Azure Service Bus https://servicebus.azure.net/ Available December 2017

How much does Managed Service Identity cost?

Managed Service Identity comes with Azure Active Directory Free, which is the default for Azure subscriptions. There is no additional cost for Managed Service Identity.

Support and feedback

We would love to hear from you!