Azure web app: Remove client secrets from app registration and use Managed Identity?

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31-08-2024

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Ditching Client Secrets: Transitioning to Managed Identity in Azure Web Apps

Moving away from client secrets and embracing Managed Identity is a crucial step in enhancing security and simplifying your application's authentication flow. This article will guide you through the process of transitioning from client secrets to Managed Identity in Azure Web Apps, using practical examples and insights from Stack Overflow.

Understanding the Problem:

As highlighted by a Stack Overflow user, security concerns often necessitate a move away from client secrets, which are susceptible to compromise. Managed Identity provides a secure and robust alternative by allowing your application to obtain access tokens without requiring explicitly stored credentials.

Key Components:

• Azure Active Directory (Azure AD): This is the identity and access management service that provides the framework for authentication and authorization in Azure.
• Managed Identity: This feature provides an identity for your Azure resources, allowing them to authenticate to other Azure services without requiring you to manage credentials.
• User Assigned Identity: This type of Managed Identity is explicitly assigned to a specific Azure resource (like your web app).

The Solution: A Step-by-Step Guide:

1. Enable Managed Identity for Your Web App:

   • Navigate to your Web App in the Azure portal.
   • Go to the "Identity" section.
   • Enable "System assigned" or "User assigned" identity. For this example, we'll focus on "User assigned" identity, as mentioned by the Stack Overflow user.
   • Assign a User Assigned Identity to your Web App.
   • Tip: You can create a new User Assigned Identity directly within the Web App's "Identity" settings.

2. Configure Your Application to Use the Managed Identity:

   • Update Your Code: Replace any code that utilizes your old client secret with the following steps:

     • Use the Microsoft.Identity.Web library, which provides convenient methods for working with Managed Identity.
     • Modify the program.cs file to integrate Managed Identity into your authentication setup. Refer to the documentation for Microsoft.Identity.Web for detailed instructions.

   • Example:

     builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
        .AddMicrosoftIdentityWebApp(builder.Configuration.GetSection("AzureAd"))
        .EnableTokenAcquisitionToCallDownstreamApi(new string[] { "api://{Guid API}/Users.ReadWrite.All" })
        .AddInMemoryTokenCaches()
        .ConfigureTokenAcquisitionOnBehalfOfUser(options =>
        {
            options.ClientId = "<Your Application's Client Id>";
            options.ClientSecret = null; // No secret required with Managed Identity!
            // Configure other options, like token caching, as needed.
        });
     

3. Grant Permissions to Your User Assigned Identity:

   • In your Azure AD, go to your API registration.
   • Navigate to "Permissions" -> "Add a permission" -> "Azure AD" -> "Select an API" -> Choose the API your Web App needs to access.
   • Grant the required permissions to your User Assigned Identity.

Addressing the React App Scenario:

The React app scenario presented in the Stack Overflow question involves the Web App acquiring an access token and passing it to the React application. This token is then used by the React app to interact with another API.

Here's how you can adapt this scenario to use Managed Identity:

1. Acquire Token in the Web App:

   • Use the Microsoft.Identity.Web library's TokenAcquisition class to acquire an access token.
   • Example:

     private readonly ITokenAcquisition _tokenAcquisition;
     
     public HomeController(ITokenAcquisition tokenAcquisition)
     {
         _tokenAcquisition = tokenAcquisition;
     }
     
     public async Task<IActionResult> Index()
     {
         var accessToken = await _tokenAcquisition.GetAccessTokenForUserAsync(new[] { "api://{Guid API}/Users.ReadWrite.All" });
         // Pass the accessToken to your React app.
         return View();
     }
     

2. Pass Token to React App:

   • Include the access token in your React app's initial data payload, for instance, within the HTML markup or as a JavaScript variable.

3. React App Authentication:

   • Your React app can use the provided access token to authenticate requests to the other API, using libraries like axios or fetch.

Important Considerations:

• Scope: Ensure that the permissions granted to your User Assigned Identity align with the required actions for your Web App and the React app.
• Security Best Practices:
  • Limit the permissions granted to your Managed Identity to the bare minimum necessary.
  • Implement secure token storage and handling mechanisms in your React app.
  • Consider employing a token validation mechanism on your backend API to ensure the received tokens are valid.

Conclusion:

Transitioning to Managed Identity is a powerful way to improve your application's security posture by eliminating the need for client secrets. By following these steps and incorporating the best practices outlined above, you can effectively adopt Managed Identity and enhance the overall security and manageability of your Azure Web App. Remember to leverage resources like Stack Overflow and the Microsoft Azure documentation for comprehensive guidance and support.