Tutorial: Secure Azure SQL Database connection from App Service using a managed identity

App Service provides a highly scalable, self-patching web hosting service in Azure. It also provides a managed identity for your app, which is a turn-key solution for securing access to Azure SQL Database and other Azure services. Managed identities in App Service make your app more secure by eliminating secrets from your app, such as credentials in the connection strings. In this tutorial, you will add managed identity to the sample web app you built in one of the following tutorials:

When you're finished, your sample app will connect to SQL Database securely without the need of username and passwords.

Architecture diagram for tutorial scenario.

Note

The steps covered in this tutorial support the following versions:

  • .NET Framework 4.7.2 and above
  • .NET Core 2.2 and above

What you will learn:

  • Enable managed identities
  • Grant SQL Database access to the managed identity
  • Configure Entity Framework to use Azure AD authentication with SQL Database
  • Connect to SQL Database from Visual Studio using Azure AD authentication

Note

Azure AD authentication is different from Integrated Windows authentication in on-premises Active Directory (AD DS). AD DS and Azure AD use completely different authentication protocols. For more information, see Azure AD Domain Services documentation.

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

Prerequisites

This article continues where you left off in Tutorial: Build an ASP.NET app in Azure with SQL Database or 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.

To debug your app using SQL Database as the back end, make sure that you've allowed client connection from your computer. If not, add the client IP by following the steps at Manage server-level IP firewall rules using the Azure portal.

Prepare your environment for the Azure CLI.

  • Use the Bash environment in Azure Cloud Shell.

    Launch Cloud Shell in a new window

  • If you prefer, install the Azure CLI to run CLI reference commands.

    • If you're using a local installation, sign in to the Azure CLI by using the az login command. To finish the authentication process, follow the steps displayed in your terminal. For additional sign-in options, see Sign in with the Azure CLI.

    • When you're prompted, install Azure CLI extensions on first use. For more information about extensions, see Use extensions with the Azure CLI.

    • Run az version to find the version and dependent libraries that are installed. To upgrade to the latest version, run az upgrade.

Grant database access to Azure AD user

First enable Azure AD authentication to SQL Database by assigning an Azure AD user as the Active Directory 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 Azure AD. For more information on allowed Azure AD users, see Azure AD features and limitations in SQL Database.

  1. If your Azure AD tenant doesn't have a user yet, create one by following the steps at Add or delete users using Azure Active Directory.

  2. Find the object ID of the Azure AD 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 [].objectId --output tsv)
    

    Tip

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

  3. Add this Azure AD user as an Active Directory admin using az sql server ad-admin create command in the Cloud Shell. In the following command, replace <server-name> with the server name (without the .database.windows.net suffix).

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

For more information on adding an Active Directory admin, see Provision an Azure Active Directory administrator for your server

Set up Visual Studio

  1. Visual Studio for Windows is integrated with Azure AD authentication. To enable development and debugging in Visual Studio, add your Azure AD user in Visual Studio by selecting File > Account Settings from the menu, and click Add an account.

  2. To set the Azure AD user for Azure service authentication, select Tools > Options from the menu, then select Azure Service Authentication > Account Selection. Select the Azure AD user you added and click OK.

You're now ready to develop and debug your app with the SQL Database as the back end, using Azure AD authentication.

Modify your project

The steps you follow for your project depends on whether it's an ASP.NET project or an ASP.NET Core project.

  1. In Visual Studio, open the Package Manager Console and add the NuGet package Microsoft.Azure.Services.AppAuthentication:

    Install-Package Microsoft.Azure.Services.AppAuthentication -Version 1.4.0
    
  2. In Web.config, working from the top of the file and make the following changes:

    • In <configSections>, add the following section declaration in it:

      <section name="SqlAuthenticationProviders" type="System.Data.SqlClient.SqlAuthenticationProviderConfigurationSection, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
      
    • below the closing </configSections> tag, add the following XML code for <SqlAuthenticationProviders>.

      <SqlAuthenticationProviders>
        <providers>
          <add name="Active Directory Interactive" type="Microsoft.Azure.Services.AppAuthentication.SqlAppAuthenticationProvider, Microsoft.Azure.Services.AppAuthentication" />
        </providers>
      </SqlAuthenticationProviders>
      
    • Find the connection string called MyDbConnection and replace its connectionString value with "server=tcp:<server-name>.database.windows.net;database=<db-name>;UID=AnyString;Authentication=Active Directory Interactive". Replace <server-name> and <db-name> with your server name and database name.

    Note

    The SqlAuthenticationProvider you just registered is based on top of the AppAuthentication library you installed earlier. By default, it uses a system-assigned identity. To leverage a user-assigned identity, you will need to provide an additional configuration. Please see connection string support for the AppAuthentication library.

    That's every thing you need to connect to SQL Database. When debugging in Visual Studio, your code uses the Azure AD user you configured in Set up Visual Studio. You'll set up SQL Database later to allow connection from the managed identity of your App Service app.

  3. Type Ctrl+F5 to run the app again. The same CRUD app in your browser is now connecting to the Azure SQL Database directly, using Azure AD authentication. This setup lets you run database migrations from Visual Studio.

Use managed identity connectivity

Next, you configure your App Service app to connect to SQL Database with a system-assigned managed identity.

Note

While the instructions in this section are for a system-assigned identity, a user-assigned identity can just as easily be used. To do this. you would need the change the az webapp identity assign command to assign the desired user-assigned identity. Then, when creating the SQL user, make sure to use the name of the user-assigned identity resource rather than the site name.

Enable managed identity on app

To enable a managed identity for your Azure app, use the az webapp identity assign command in the Cloud Shell. In the following command, replace <app-name>.

az webapp identity assign --resource-group myResourceGroup --name <app-name>

Note

To enable managed identity for a deployment slot, add --slot <slot-name> and use the name of the slot in <slot-name>.

Here's an example of the output:

{
  "additionalProperties": {},
  "principalId": "21dfa71c-9e6f-4d17-9e90-1d28801c9735",
  "tenantId": "72f988bf-86f1-41af-91ab-2d7cd011db47",
  "type": "SystemAssigned"
}

Grant permissions to managed identity

Note

If you want, you can add the identity to an Azure AD group, then grant SQL Database access to the Azure AD group instead of the identity. For example, the following commands add the managed identity from the previous step to a new group called myAzureSQLDBAccessGroup:

groupid=$(az ad group create --display-name myAzureSQLDBAccessGroup --mail-nickname myAzureSQLDBAccessGroup --query objectId --output tsv)
msiobjectid=$(az webapp identity show --resource-group myResourceGroup --name <app-name> --query principalId --output tsv)
az ad group member add --group $groupid --member-id $msiobjectid
az ad group member list -g $groupid
  1. In the Cloud Shell, sign in to SQL Database by using the SQLCMD command. Replace <server-name> with your server name, <db-name> with the database name your app uses, and <aad-user-name> and <aad-password> with your Azure AD user's credentials.

    sqlcmd -S <server-name>.database.windows.net -d <db-name> -U <aad-user-name> -P "<aad-password>" -G -l 30
    
  2. In the SQL prompt for the database you want, run the following commands to grant the permissions your app needs. For example,

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

    <identity-name> is the name of the managed identity in Azure AD. If the identity is system-assigned, the name is always the same as the name of your App Service app. For a deployment slot, the name of its system-assigned identity is <app-name>/slots/<slot-name>. To grant permissions for an Azure AD group, use the group's display name instead (for example, myAzureSQLDBAccessGroup).

  3. Type EXIT to return to the Cloud Shell prompt.

    Note

    The back-end services of managed identities also maintains a token cache that updates the token for a target resource only when it expires. If you make a mistake configuring your SQL Database permissions and try to modify the permissions after trying to get a token with your app, you don't actually get a new token with the updated permissions until the cached token expires.

    Note

    Azure Active Directory and managed identities are not supported for on-premises SQL Server.

Modify connection string

Remember that the same changes you made in Web.config or appsettings.json works with the managed identity, so the only thing to do is to remove the existing connection string in App Service, which Visual Studio created deploying your app the first time. Use the following command, but replace <app-name> with the name of your app.

az webapp config connection-string delete --resource-group myResourceGroup --name <app-name> --setting-names MyDbConnection

Publish your changes

All that's left now is to publish your changes to Azure.

  1. If you came from Tutorial: Build an ASP.NET app in Azure with SQL Database, publish your changes in Visual Studio. In the Solution Explorer, right-click your DotNetAppSqlDb project and select Publish.

    Publish from Solution Explorer

  2. In the publish page, click Publish.

    Important

    Ensure that your app service name doesn't match with any existing App Registrations. This will lead to Principal ID conflicts.

When the new webpage shows your to-do list, your app is connecting to the database using the managed identity.

Azure app after Code First Migration

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

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 in the Cloud Shell:

az group delete --name myResourceGroup

This command may take a minute to run.

Next steps

What you learned:

  • Enable managed identities
  • Grant SQL Database access to the managed identity
  • Configure Entity Framework to use Azure AD authentication with SQL Database
  • Connect to SQL Database from Visual Studio using Azure AD authentication