Handling Azure AD B2C Claims in Blazor Application

Introduction

Handling user authentication and managing claims are critical to building secure, personalized web applications. In my last article, we explored how to integrate Azure AD B2C as an identity provider for our Blazor application. This article will explore how to handle Azure AD B2C user claims in a Blazor application. Azure AD B2C allows you to define user attributes, enabling a rich and flexible identity management system. By leveraging the power of Blazor and the Microsoft Identity library, we will explore how to retrieve, process, and use these claims to customize user experiences.

User claims

The Microsoft Identity library integrates with Azure AD B2C to manage authentication and extract claims from ID tokens. When a user authenticates through Azure AD B2C, the library facilitates the retrieval of the ID token, which contains user-specific claims, such as email, name, or custom attributes defined in the Azure AD B2C policy. The library validates the token's signature, issuer, and audience to ensure its authenticity and securely parses the claims. As developers, we can access these claims through the library's intuitive object model to tailor application functionality, enforce custom authorization rules, or create personalized user experiences. By handling the complexities of token validation and claims extraction, the Microsoft Identity library simplifies the integration process with Azure AD B2C, allowing developers to focus on building secure and scalable applications.

1. Log in to the Azure portal and switch to your Azure AD B2C tenant.
2. Select User flows under the Policies Section.
   
3. Select the user flow. In my case, it is B2C_1_SignIn_SignUp_Demo. Select Application Claims. It will list all the available claims, including the system and custom claims.
   
4. You can retrieve all selected claims through the ID Token from your Blazor application.

Blazor Code

<AuthorizeView>
    <Authorized>
        <table class="table table-striped table-bordered table-condensed table-hover">
            <tr>
                <th>ClaimType</th>
                <th>Value</th>
            </tr>
            @foreach (var claim in context.User.Claims)
            {
                <tr>
                    <td>@claim.Type</td>
                    <td>@claim.Value</td>
                </tr>
            }
        </table>
        <a href="MicrosoftIdentity/Account/SignOut">Log out</a>
    </Authorized>
    <NotAuthorized>
        <a href="MicrosoftIdentity/Account/SignIn">Log in</a>
    </NotAuthorized>
</AuthorizeView>

The above code will iterate and retrieve the claims from the user context

The Microsoft Identity platform libraries process user authentication, retrieve claims from the ID token, and update the user context based on user information extracted from the token.

We can easily read all the user authentication statuses and information in the user context.

You can see the list of user claims in the user context in the above screenshot.

Let’s include the city claim from the Azure AD B2C User flow for testing purposes.

Run the application and check. You should now receive the city claim for the logged-in user as well.

Summary

This article shows how to handle Azure AD B2C claims in a Blazor application to build secure and personalized user experiences. We experimented with configuring user flows and retrieving claims from ID tokens using the Microsoft Identity library. We also discussed a practical example of accessing, processing, and utilizing claims within a Blazor. Following the step-by-step guidance, developers can seamlessly integrate Azure AD B2C claims into their Blazor projects, ensuring a scalable and secure identity management solution.

• GitHub Repository