Tutorial: Connect an App Service app to SQL Database on behalf of the signed-in user

This tutorial shows you how to enable built-in authentication in an App Service app using the Microsoft Entra authentication provider, then extend it by connecting it to a back-end Azure SQL Database by impersonating the signed-in user (also known as the on-behalf-of flow). This is a more advanced connectivity approach to Tutorial: Access data with managed identity and has the following advantages in enterprise scenarios:

• Eliminates connection secrets to back-end services, just like the managed identity approach.
• Gives the back-end database (or any other Azure service) more control over who or how much to grant access to its data and functionality.
• Lets the app tailor its data presentation to the signed-in user.

In this tutorial, you add Microsoft Entra authentication to the sample web app you deployed in one of the following tutorials:

• Tutorial: Build an ASP.NET app in Azure with Azure SQL Database
• Tutorial: Build an ASP.NET Core and Azure SQL Database app in Azure App Service

When you're finished, your sample app will authenticate users connect to SQL Database securely on behalf of the signed-in user.

What you will learn:

If you don't have an Azure subscription, create a trial account before you begin.

Prerequisites

This article continues where you left off in either one of the following tutorials:

• Tutorial: Build an ASP.NET app in Azure with SQL Database
• Tutorial: Build an ASP.NET Core and SQL Database app in Azure App Service.

If you haven't already, follow one of the two tutorials first. Alternatively, you can adapt the steps for your own .NET app with SQL Database.

Prepare your environment for the Azure CLI.

1. Configure database server with Microsoft Entra authentication

First, enable Microsoft Entra authentication to SQL Database by assigning a Microsoft Entra user as the admin of the server. This user is different from the Microsoft account you used to sign up for your Azure subscription. It must be a user that you created, imported, synced, or invited into Microsoft Entra ID. For more information on allowed Microsoft Entra users, see Microsoft Entra features and limitations in SQL Database.

1. If your Microsoft Entra tenant doesn't have a user yet, create one by following the steps at Add or delete users using Microsoft Entra ID.

2. Find the object ID of the Microsoft Entra user using the az ad user list and replace <user-principal-name>. The result is saved to a variable.

   azureaduser=$(az ad user list --filter "userPrincipalName eq '<user-principal-name>'" --query [].id --output tsv)
   

   Tip

   To see the list of all user principal names in Microsoft Entra ID, run az ad user list --query [].userPrincipalName.

3. Add this Microsoft Entra user as an Active Directory admin using az sql server ad-admin create command. In the following command, replace <server-name> with the server name (without the .database.chinacloudapi.cn suffix).

   az sql server ad-admin create --resource-group <group-name> --server-name <server-name> --display-name ADMIN --object-id $azureaduser
   

4. Restrict the database server authentication to Active Directory authentication. This step effectively disables SQL authentication.

   az sql server ad-only-auth enable --resource-group <group-name> --name <server-name>
   

For more information on adding an Active Directory admin, see Provision Microsoft Entra admin (SQL Database).

2. Enable user authentication for your app

You enable authentication with Microsoft Entra ID as the identity provider. For more information, see Configure Microsoft Entra authentication for your App Services application.

1. In the Azure portal menu, select Resource groups or search for and select Resource groups from any page.

2. In Resource groups, find and select your resource group, then select your app.

3. In your app's left menu, select Authentication, and then select Add identity provider.

4. In the Add an identity provider page, select Microsoft as the Identity provider to sign in Microsoft and Microsoft Entra identities.

5. Accept the default settings and select Add.

   

3. Configure user impersonation to SQL Database

Currently, your Azure app connects to SQL Database uses SQL authentication (username and password) managed as app settings. In this step, you give the app permissions to access SQL Database on behalf of the signed-in Microsoft Entra user.

1. In the Authentication page for the app, select your app name under Identity provider. This app registration was automatically generated for you. Select API permissions in the left menu.

2. Select Add a permission, then select APIs my organization uses.

3. Type Azure SQL Database in the search box and select the result.

4. In the Request API permissions page for Azure SQL Database, select Delegated permissions and user_impersonation, then select Add permissions.

   

4. Configure App Service to return a usable access token

The app registration in Microsoft Entra ID now has the required permissions to connect to SQL Database by impersonating the signed-in user. Next, you configure your App Service app to give you a usable access token.

In powershell, run the following commands on the app to add the scope parameter to the authentication setting identityProviders.azureActiveDirectory.login.loginParameters.

authSettings=$(az webapp auth show --resource-group <group-name> --name <app-name>)
authSettings=$(echo "$authSettings" | jq '.properties' | jq '.identityProviders.azureActiveDirectory.login += {"loginParameters":["scope=openid profile email offline_access https://database.chinacloudapi.cn/user_impersonation"]}')
az webapp auth set --resource-group <group-name> --name <app-name> --body "$authSettings"

The commands effectively add a loginParameters property with extra custom scopes. Here's an explanation of the requested scopes:

• openid, profile, and email are requested by App Service by default already. For information, see OpenID Connect Scopes.
• https://database.chinacloudapi.cn/user_impersonation refers to Azure SQL Database. It's the scope that gives you a JWT token that includes SQL Database as a token audience.
• offline_access is included here for convenience (in case you want to refresh tokens).

Your apps are now configured. The app can now generate a token that SQL Database accepts.

5. Use the access token in your application code

The steps you follow for your project depends on whether you're using Entity Framework (default for ASP.NET) or Entity Framework Core (default for ASP.NET Core).

public MyDatabaseContext (DbContextOptions<MyDatabaseContext> options, IHttpContextAccessor accessor)
    : base(options)
{
    var conn = Database.GetDbConnection() as SqlConnection;
    conn.AccessToken = accessor.HttpContext.Request.Headers["X-MS-TOKEN-AAD-ACCESS-TOKEN"];
}

6. Publish your changes

When the new webpage shows your to-do list, your app is connecting to the database on behalf of the signed-in Microsoft Entra user.

You should now be able to edit the to-do list as before.

7. Clean up resources

In the preceding steps, you created Azure resources in a resource group. If you don't expect to need these resources in the future, delete the resource group by running the following command:

az group delete --name <group-name>

This command may take a minute to run.

Frequently asked questions

• Why do I get a Login failed for user '<token-identified principal>'. error?
• How do I add other Microsoft Entra users or groups in Azure SQL Database?
• How do I debug locally when using App Service authentication?
• What happens when access tokens expire?

Why do I get a Login failed for user '<token-identified principal>'. error?

The most common causes of this error are:

• You're running the code locally, and there's no valid token in the X-MS-TOKEN-AAD-ACCESS-TOKEN request header. See How do I debug locally when using App Service authentication?.
• Microsoft Entra authentication isn't configured on your SQL Database.
• The signed-in user isn't permitted to connect to the database. See How do I add other Microsoft Entra users or groups in Azure SQL Database?.

How do I add other Microsoft Entra users or groups in Azure SQL Database?

1. Connect to your database server, such as with sqlcmd or SSMS.

2. Create contained users mapped to Microsoft Entra identities in SQL Database documentation.

   The following Transact-SQL example adds a Microsoft Entra identity to SQL Server and gives it some database roles:

   CREATE USER [<user-or-group-name>] FROM EXTERNAL PROVIDER;
   ALTER ROLE db_datareader ADD MEMBER [<user-or-group-name>];
   ALTER ROLE db_datawriter ADD MEMBER [<user-or-group-name>];
   ALTER ROLE db_ddladmin ADD MEMBER [<user-or-group-name>];
   GO
   

How do I debug locally when using App Service authentication?

Because App Service authentication is a feature in Azure, it's not possible for the same code to work in your local environment. Unlike the app running in Azure, your local code doesn't benefit from the authentication middleware from App Service. You have a few alternatives:

• Connect to SQL Database from your local environment with Active Directory Interactive. The authentication flow doesn't sign in the user to the app itself, but it does connect to the back-end database with the signed-in user, and allows you to test database authorization locally.
• Manually copy the access token from https://<app-name>.chinacloudsites.cn/.auth/me into your code, in place of the X-MS-TOKEN-AAD-ACCESS-TOKEN request header.
• If you deploy from Visual Studio, use remote debugging of your App Service app.

What happens when access tokens expire?

Your access token expires after some time.

Next steps

What you learned: