Secure an ASP.NET Core Blazor WebAssembly standalone app with Azure Active Directory B2C

Article
11/10/2022
56 minutes to read

This article explains how to create a standalone Blazor WebAssembly app that uses Azure Active Directory (AAD) B2C for authentication.

Create a tenant or identify an existing B2C tenant for the app to use in the Azure portal by following the guidance in the Create an AAD B2C tenant (Azure documentation) article. Return to this article immediately after creating or identifying a tenant to use.

Record the following information:

AAD B2C instance (for example, https://contoso.b2clogin.com/, which includes the trailing slash): The instance is the scheme and host of an Azure B2C app registration, which can be found by opening the Endpoints window from the App registrations page in the Azure portal.
AAD B2C Primary/Publisher/Tenant domain (for example, contoso.onmicrosoft.com): The domain is available as the Publisher domain in the Branding blade of the Azure portal for the registered app.

Navigate to Azure Active Directory in the Azure portal. Select App registrations in the sidebar. Select the New registration button.
Provide a Name for the app (for example, Blazor Standalone AAD B2C).
For Supported account types, select the multi-tenant option: Accounts in any organizational directory or any identity provider. For authenticating users with Azure AD B2C.
Set the Redirect URI drop down to Single-page application (SPA) and provide the following redirect URI: https://localhost/authentication/login-callback. If you know the production redirect URI for the Azure default host (for example, azurewebsites.net) or the custom domain host (for example, contoso.com), you can also add the production redirect URI at the same time that you're providing the localhost redirect URI. Be sure to include the port number for non-:443 ports in any production redirect URIs that you add.
If you're using an unverified publisher domain, confirm that Permissions > Grant admin consent to openid and offline_access permissions is selected. If the publisher domain is verified, this checkbox isn't present.
Select Register.

Note

Supplying the port number for a localhost AAD B2C redirect URI isn't required. For more information, see Redirect URI (reply URL) restrictions and limitations: Localhost exceptions (Azure documentation).

Record the Application (client) ID (for example, 41451fa7-82d9-4673-8fa5-69eff5a761fd).

In Authentication > Platform configurations > Single-page application (SPA):

Confirm the Redirect URI of https://localhost/authentication/login-callback is present.
In the Implicit grant section, ensure that the checkboxes for Access tokens and ID tokens are not selected.
The remaining defaults for the app are acceptable for this experience.
Select the Save button.

In Home > Azure AD B2C > User flows:

Create a sign-up and sign-in user flow

At a minimum, select the Application claims > Display Name user attribute to populate the context.User.Identity.Name in the LoginDisplay component (Shared/LoginDisplay.razor).

Record the sign-up and sign-in user flow name created for the app (for example, B2C_1_signupsignin).

In an empty folder, replace the placeholders in the following command with the information recorded earlier and execute the command in a command shell:

dotnet new blazorwasm -au IndividualB2C --aad-b2c-instance "{AAD B2C INSTANCE}" --client-id "{CLIENT ID}" --domain "{TENANT DOMAIN}" -o {APP NAME} -ssp "{SIGN UP OR SIGN IN POLICY}"

Placeholder	Azure portal name	Example
`{AAD B2C INSTANCE}`	Instance	`https://contoso.b2clogin.com/` (includes the trailing slash)
`{APP NAME}`	—	`BlazorSample`
`{CLIENT ID}`	Application (client) ID	`41451fa7-82d9-4673-8fa5-69eff5a761fd`
`{SIGN UP OR SIGN IN POLICY}`	Sign-up/sign-in user flow	`B2C_1_signupsignin1`
`{TENANT DOMAIN}`	Primary/Publisher/Tenant domain	`contoso.onmicrosoft.com`

The output location specified with the -o|--output option creates a project folder if it doesn't exist and becomes part of the app's name.

Add a pair of MsalProviderOptions for openid and offline_access DefaultAccessTokenScopes:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("openid");
    options.ProviderOptions.DefaultAccessTokenScopes.Add("offline_access");
});

After creating the app, you should be able to:

Log into the app using an AAD user account.
Request access tokens for Microsoft APIs. For more information, see:
- Access token scopes
- Quickstart: Configure an application to expose web APIs.

Authentication package

When an app is created to use an Individual B2C Account (IndividualB2C), the app automatically receives a package reference for the Microsoft Authentication Library (Microsoft.Authentication.WebAssembly.Msal). The package provides a set of primitives that help the app authenticate users and obtain tokens to call protected APIs.

If adding authentication to an app, manually add the Microsoft.Authentication.WebAssembly.Msal package to the app.

Note

For guidance on adding packages to .NET apps, see the articles under Install and manage packages at Package consumption workflow (NuGet documentation). Confirm correct package versions at NuGet.org.

The Microsoft.Authentication.WebAssembly.Msal package transitively adds the Microsoft.AspNetCore.Components.WebAssembly.Authentication package to the app.

Authentication service support

Support for authenticating users is registered in the service container with the AddMsalAuthentication extension method provided by the Microsoft.Authentication.WebAssembly.Msal package. This method sets up all of the services required for the app to interact with the Identity Provider (IP).

Program.cs:

builder.Services.AddMsalAuthentication(options =>
{
    builder.Configuration.Bind("AzureAdB2C", options.ProviderOptions.Authentication);
});

The AddMsalAuthentication method accepts a callback to configure the parameters required to authenticate an app. The values required for configuring the app can be obtained from the AAD configuration when you register the app.

Configuration is supplied by the wwwroot/appsettings.json file:

{
  "AzureAdB2C": {
    "Authority": "{AAD B2C INSTANCE}{DOMAIN}/{SIGN UP OR SIGN IN POLICY}",
    "ClientId": "{CLIENT ID}",
    "ValidateAuthority": false
  }
}

In the preceding configuration, the {AAD B2C INSTANCE} includes a trailing slash.

Example:

{
  "AzureAdB2C": {
    "Authority": "https://contoso.b2clogin.com/contoso.onmicrosoft.com/B2C_1_signupsignin1",
    "ClientId": "41451fa7-82d9-4673-8fa5-69eff5a761fd",
    "ValidateAuthority": false
  }
}

Access token scopes

The Blazor WebAssembly template doesn't automatically configure the app to request an access token for a secure API. To provision an access token as part of the sign-in flow, add the scope to the default access token scopes of the MsalProviderOptions:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("{SCOPE URI}");
});

Specify additional scopes with AdditionalScopesToConsent:

options.ProviderOptions.AdditionalScopesToConsent.Add("{ADDITIONAL SCOPE URI}");

For more information, see the following sections of the Additional scenarios article:

The framework defaults to pop-up login mode and falls back to redirect login mode if a pop-up can't be opened. Configure MSAL to use redirect login mode by setting the LoginMode property of MsalProviderOptions to redirect:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.LoginMode = "redirect";
});

The default setting is popup, and the string value isn't case-sensitive.

Imports file

The Microsoft.AspNetCore.Components.Authorization namespace is made available throughout the app via the _Imports.razor file:

@using System.Net.Http
@using System.Net.Http.Json
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.Forms
@using Microsoft.AspNetCore.Components.Routing
@using Microsoft.AspNetCore.Components.Web
@using Microsoft.AspNetCore.Components.Web.Virtualization
@using Microsoft.AspNetCore.Components.WebAssembly.Http
@using Microsoft.JSInterop
@using {APPLICATION ASSEMBLY}
@using {APPLICATION ASSEMBLY}.Shared

Index page

The Index page (wwwroot/index.html) page includes a script that defines the AuthenticationService in JavaScript. AuthenticationService handles the low-level details of the OIDC protocol. The app internally calls methods defined in the script to perform the authentication operations.

<script src="_content/Microsoft.Authentication.WebAssembly.Msal/AuthenticationService.js"></script>

App component

The App component (App.razor) is similar to the App component found in Blazor Server apps:

The CascadingAuthenticationState component manages exposing the AuthenticationState to the rest of the app.
The AuthorizeRouteView component makes sure that the current user is authorized to access a given page or otherwise renders the RedirectToLogin component.
The RedirectToLogin component manages redirecting unauthorized users to the login page.

Due to changes in the framework across releases of ASP.NET Core, Razor markup for the App component (App.razor) isn't shown in this section. To inspect the markup of the component for a given release, use either of the following approaches:

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the App component (App.razor) in the generated app.
Inspect the App component (App.razor) in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

RedirectToLogin component

The RedirectToLogin component (Shared/RedirectToLogin.razor):

Manages redirecting unauthorized users to the login page.
Preserves the current URL that the user is attempting to access so that they can be returned to that page if authentication is successful.

@inject NavigationManager Navigation
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@using Microsoft.Extensions.Options

@inject IOptionsSnapshot<RemoteAuthenticationOptions<ApiAuthorizationProviderOptions>> Options
@code {
    protected override void OnInitialized()
    {
        Navigation.NavigateToLogin(Options.Get(
            Microsoft.Extensions.Options.Options.DefaultName)
            .AuthenticationPaths.LogInPath);
    }
}

LoginDisplay component

The LoginDisplay component (Shared/LoginDisplay.razor) is rendered in the MainLayout component (Shared/MainLayout.razor) and manages the following behaviors:

For authenticated users:
- Displays the current username.
- Offers a button to log out of the app.
For anonymous users, offers the option to log in.

Due to changes in the framework across releases of ASP.NET Core, Razor markup for the LoginDisplay component isn't shown in this section. To inspect the markup of the component for a given release, use either of the following approaches:

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the LoginDisplay component in the generated app.
Inspect the LoginDisplay component in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

Authentication component

The page produced by the Authentication component (Pages/Authentication.razor) defines the routes required for handling different authentication stages.

The RemoteAuthenticatorView component:

Is provided by the Microsoft.AspNetCore.Components.WebAssembly.Authentication package.
Manages performing the appropriate actions at each stage of authentication.

@page "/authentication/{action}"
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication

<RemoteAuthenticatorView Action="@Action" />

@code {
    [Parameter]
    public string Action { get; set; }
}

Custom user flows

The Microsoft Authentication Library (Microsoft.Authentication.WebAssembly.Msal, NuGet package) doesn't support AAD B2C user flows by default. Create custom user flows in developer code.

For more information on how to build a challenge for a custom user flow, see User flows in Azure Active Directory B2C.

Troubleshoot

Logging

To enable debug or trace logging for Blazor WebAssembly authentication in ASP.NET Core 7.0 or later, see ASP.NET Core Blazor logging.

Common errors

Misconfiguration of the app or Identity Provider (IP)

The most common errors are caused by incorrect configuration. The following are a few examples:
- Depending on the requirements of the scenario, a missing or incorrect Authority, Instance, Tenant ID, Tenant domain, Client ID, or Redirect URI prevents an app from authenticating clients.
- An incorrect access token scope prevents clients from accessing server web API endpoints.
- Incorrect or missing server API permissions prevent clients from accessing server web API endpoints.
- Running the app at a different port than is configured in the Redirect URI of the Identity Provider's app registration.
Configuration sections of this article's guidance show examples of the correct configuration. Carefully check each section of the article looking for app and IP misconfiguration.

If the configuration appears correct:
- Analyze application logs.
- Examine the network traffic between the client app and the IP or server app with the browser's developer tools. Often, an exact error message or a message with a clue to what's causing the problem is returned to the client by the IP or server app after making a request. Developer tools guidance is found in the following articles:
  - Google Chrome (Google documentation)
  - Microsoft Edge
  - Mozilla Firefox (Mozilla documentation)
- Decode the contents of a JSON Web Token (JWT) used for authenticating a client or accessing a server web API, depending on where the problem is occurring. For more information, see Inspect the content of a JSON Web Token (JWT).
The documentation team responds to document feedback and bugs in articles (open an issue from the This page feedback section) but is unable to provide product support. Several public support forums are available to assist with troubleshooting an app. We recommend the following:
The preceding forums are not owned or controlled by Microsoft.

For non-security, non-sensitive, and non-confidential reproducible framework bug reports, open an issue with the ASP.NET Core product unit. Don't open an issue with the product unit until you've thoroughly investigated the cause of a problem and can't resolve it on your own and with the help of the community on a public support forum. The product unit isn't able to troubleshoot individual apps that are broken due to simple misconfiguration or use cases involving third-party services. If a report is sensitive or confidential in nature or describes a potential security flaw in the product that attackers may exploit, see Reporting security issues and bugs (dotnet/aspnetcore GitHub repository).
Unauthorized client for AAD

info: Microsoft.AspNetCore.Authorization.DefaultAuthorizationService[2] Authorization failed. These requirements were not met: DenyAnonymousAuthorizationRequirement: Requires an authenticated user.

Login callback error from AAD:
- Error: unauthorized_client
- Description: AADB2C90058: The provided application is not configured to allow public clients.
To resolve the error:
1. In the Azure portal, access the app's manifest.
2. Set the allowPublicClient attribute to null or true.

Cookies and site data

Cookies and site data can persist across app updates and interfere with testing and troubleshooting. Clear the following when making app code changes, user account changes with the provider, or provider app configuration changes:

User sign-in cookies
App cookies
Cached and stored site data

One approach to prevent lingering cookies and site data from interfering with testing and troubleshooting is to:

Configure a browser
- Use a browser for testing that you can configure to delete all cookie and site data each time the browser is closed.
- Make sure that the browser is closed manually or by the IDE for any change to the app, test user, or provider configuration.
Use a custom command to open a browser in incognito or private mode in Visual Studio:
- Open Browse With dialog box from Visual Studio's Run button.
- Select the Add button.
- Provide the path to your browser in the Program field. The following executable paths are typical installation locations for Windows 10. If your browser is installed in a different location or you aren't using Windows 10, provide the path to the browser's executable.
  - Microsoft Edge: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe
  - Google Chrome: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
  - Mozilla Firefox: C:\Program Files\Mozilla Firefox\firefox.exe
- In the Arguments field, provide the command-line option that the browser uses to open in incognito or private mode. Some browsers require the URL of the app.
  - Microsoft Edge: Use -inprivate.
  - Google Chrome: Use --incognito --new-window {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
  - Mozilla Firefox: Use -private -url {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
- Provide a name in the Friendly name field. For example, Firefox Auth Testing.
- Select the OK button.
- To avoid having to select the browser profile for each iteration of testing with an app, set the profile as the default with the Set as Default button.
- Make sure that the browser is closed by the IDE for any change to the app, test user, or provider configuration.

App upgrades

A functioning app may fail immediately after upgrading either the .NET Core SDK on the development machine or changing package versions within the app. In some cases, incoherent packages may break an app when performing major upgrades. Most of these issues can be fixed by following these instructions:

Clear the local system's NuGet package caches by executing dotnet nuget locals all --clear from a command shell.
Delete the project's bin and obj folders.
Restore and rebuild the project.
Delete all of the files in the deployment folder on the server prior to redeploying the app.

Note

Use of package versions incompatible with the app's target framework isn't supported. For information on a package, use the NuGet Gallery or FuGet Package Explorer.

Run the Server app

When testing and troubleshooting a hosted Blazor WebAssembly solution, make sure that you're running the app from the Server project. For example in Visual Studio, confirm that the Server project is highlighted in Solution Explorer before you start the app with any of the following approaches:

Select the Run button.
Use Debug > Start Debugging from the menu.
Press F5.

Inspect the user

The ASP.NET Core framework's test assets include a Blazor WebAssembly client app with a User component that can be useful in troubleshooting. The User component can be used directly in apps or serve as the basis for further customization:

User test component in the dotnet/aspnetcore GitHub repository

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

Inspect the content of a JSON Web Token (JWT)

To decode a JSON Web Token (JWT), use Microsoft's jwt.ms tool. Values in the UI never leave your browser.

Example encoded JWT (shortened for display):

eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ilg1ZVhrNHh5b2pORnVtMWtsMll0djhkbE5QNC1j ... bQdHBHGcQQRbW7Wmo6SWYG4V_bU55Ug_PW4pLPr20tTS8Ct7_uwy9DWrzCMzpD-EiwT5IjXwlGX3IXVjHIlX50IVIydBoPQtadvT7saKo1G5Jmutgq41o-dmz6-yBMKV2_nXA25Q

Example JWT decoded by the tool for an app that authenticates against Azure AAD B2C:

{
  "typ": "JWT",
  "alg": "RS256",
  "kid": "X5eXk4xyojNFum1kl2Ytv8dlNP4-c57dO6QGTVBwaNk"
}.{
  "exp": 1610059429,
  "nbf": 1610055829,
  "ver": "1.0",
  "iss": "https://mysiteb2c.b2clogin.com/5cc15ea8-a296-4aa3-97e4-226dcc9ad298/v2.0/",
  "sub": "5ee963fb-24d6-4d72-a1b6-889c6e2c7438",
  "aud": "70bde375-fce3-4b82-984a-b247d823a03f",
  "nonce": "b2641f54-8dc4-42ca-97ea-7f12ff4af871",
  "iat": 1610055829,
  "auth_time": 1610055822,
  "idp": "idp.com",
  "tfp": "B2C_1_signupsignin"
}.[Signature]

Additional resources

Record the following information:

AAD B2C instance (for example, https://contoso.b2clogin.com/, which includes the trailing slash): The instance is the scheme and host of an Azure B2C app registration, which can be found by opening the Endpoints window from the App registrations page in the Azure portal.
AAD B2C Primary/Publisher/Tenant domain (for example, contoso.onmicrosoft.com): The domain is available as the Publisher domain in the Branding blade of the Azure portal for the registered app.

Navigate to Azure Active Directory in the Azure portal. Select App registrations in the sidebar. Select the New registration button.
Provide a Name for the app (for example, Blazor Standalone AAD B2C).
For Supported account types, select the multi-tenant option: Accounts in any organizational directory or any identity provider. For authenticating users with Azure AD B2C.
Set the Redirect URI drop down to Single-page application (SPA) and provide the following redirect URI: https://localhost/authentication/login-callback. If you know the production redirect URI for the Azure default host (for example, azurewebsites.net) or the custom domain host (for example, contoso.com), you can also add the production redirect URI at the same time that you're providing the localhost redirect URI. Be sure to include the port number for non-:443 ports in any production redirect URIs that you add.
If you're using an unverified publisher domain, confirm that Permissions > Grant admin consent to openid and offline_access permissions is selected. If the publisher domain is verified, this checkbox isn't present.
Select Register.

Note

Record the Application (client) ID (for example, 41451fa7-82d9-4673-8fa5-69eff5a761fd).

In Authentication > Platform configurations > Single-page application (SPA):

Confirm the Redirect URI of https://localhost/authentication/login-callback is present.
In the Implicit grant section, ensure that the checkboxes for Access tokens and ID tokens are not selected.
The remaining defaults for the app are acceptable for this experience.
Select the Save button.

In Home > Azure AD B2C > User flows:

Create a sign-up and sign-in user flow

At a minimum, select the Application claims > Display Name user attribute to populate the context.User.Identity.Name in the LoginDisplay component (Shared/LoginDisplay.razor).

Record the sign-up and sign-in user flow name created for the app (for example, B2C_1_signupsignin).

In an empty folder, replace the placeholders in the following command with the information recorded earlier and execute the command in a command shell:

dotnet new blazorwasm -au IndividualB2C --aad-b2c-instance "{AAD B2C INSTANCE}" --client-id "{CLIENT ID}" --domain "{TENANT DOMAIN}" -o {APP NAME} -ssp "{SIGN UP OR SIGN IN POLICY}"

Placeholder	Azure portal name	Example
`{AAD B2C INSTANCE}`	Instance	`https://contoso.b2clogin.com/` (includes the trailing slash)
`{APP NAME}`	—	`BlazorSample`
`{CLIENT ID}`	Application (client) ID	`41451fa7-82d9-4673-8fa5-69eff5a761fd`
`{SIGN UP OR SIGN IN POLICY}`	Sign-up/sign-in user flow	`B2C_1_signupsignin1`
`{TENANT DOMAIN}`	Primary/Publisher/Tenant domain	`contoso.onmicrosoft.com`

The output location specified with the -o|--output option creates a project folder if it doesn't exist and becomes part of the app's name.

Add a pair of MsalProviderOptions for openid and offline_access DefaultAccessTokenScopes:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("openid");
    options.ProviderOptions.DefaultAccessTokenScopes.Add("offline_access");
});

After creating the app, you should be able to:

Log into the app using an AAD user account.
Request access tokens for Microsoft APIs. For more information, see:
- Access token scopes
- Quickstart: Configure an application to expose web APIs.

Authentication package

If adding authentication to an app, manually add the Microsoft.Authentication.WebAssembly.Msal package to the app.

Note

The Microsoft.Authentication.WebAssembly.Msal package transitively adds the Microsoft.AspNetCore.Components.WebAssembly.Authentication package to the app.

Authentication service support

Program.cs:

builder.Services.AddMsalAuthentication(options =>
{
    builder.Configuration.Bind("AzureAdB2C", options.ProviderOptions.Authentication);
});

Configuration is supplied by the wwwroot/appsettings.json file:

{
  "AzureAdB2C": {
    "Authority": "{AAD B2C INSTANCE}{DOMAIN}/{SIGN UP OR SIGN IN POLICY}",
    "ClientId": "{CLIENT ID}",
    "ValidateAuthority": false
  }
}

In the preceding configuration, the {AAD B2C INSTANCE} includes a trailing slash.

Example:

{
  "AzureAdB2C": {
    "Authority": "https://contoso.b2clogin.com/contoso.onmicrosoft.com/B2C_1_signupsignin1",
    "ClientId": "41451fa7-82d9-4673-8fa5-69eff5a761fd",
    "ValidateAuthority": false
  }
}

Access token scopes

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("{SCOPE URI}");
});

Specify additional scopes with AdditionalScopesToConsent:

options.ProviderOptions.AdditionalScopesToConsent.Add("{ADDITIONAL SCOPE URI}");

For more information, see the following sections of the Additional scenarios article:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.LoginMode = "redirect";
});

The default setting is popup, and the string value isn't case-sensitive.

Imports file

The Microsoft.AspNetCore.Components.Authorization namespace is made available throughout the app via the _Imports.razor file:

@using System.Net.Http
@using System.Net.Http.Json
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.Forms
@using Microsoft.AspNetCore.Components.Routing
@using Microsoft.AspNetCore.Components.Web
@using Microsoft.AspNetCore.Components.Web.Virtualization
@using Microsoft.AspNetCore.Components.WebAssembly.Http
@using Microsoft.JSInterop
@using {APPLICATION ASSEMBLY}
@using {APPLICATION ASSEMBLY}.Shared

Index page

<script src="_content/Microsoft.Authentication.WebAssembly.Msal/AuthenticationService.js"></script>

App component

The App component (App.razor) is similar to the App component found in Blazor Server apps:

The CascadingAuthenticationState component manages exposing the AuthenticationState to the rest of the app.
The AuthorizeRouteView component makes sure that the current user is authorized to access a given page or otherwise renders the RedirectToLogin component.
The RedirectToLogin component manages redirecting unauthorized users to the login page.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the App component (App.razor) in the generated app.
Inspect the App component (App.razor) in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

RedirectToLogin component

The RedirectToLogin component (Shared/RedirectToLogin.razor):

Manages redirecting unauthorized users to the login page.
Preserves the current URL that the user is attempting to access so that they can be returned to that page if authentication is successful.

@inject NavigationManager Navigation
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@code {
    protected override void OnInitialized()
    {
        Navigation.NavigateTo(
            $"authentication/login?returnUrl={Uri.EscapeDataString(Navigation.Uri)}");
    }
}

LoginDisplay component

The LoginDisplay component (Shared/LoginDisplay.razor) is rendered in the MainLayout component (Shared/MainLayout.razor) and manages the following behaviors:

For authenticated users:
- Displays the current username.
- Offers a button to log out of the app.
For anonymous users, offers the option to log in.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the LoginDisplay component in the generated app.
Inspect the LoginDisplay component in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

Authentication component

The page produced by the Authentication component (Pages/Authentication.razor) defines the routes required for handling different authentication stages.

The RemoteAuthenticatorView component:

Is provided by the Microsoft.AspNetCore.Components.WebAssembly.Authentication package.
Manages performing the appropriate actions at each stage of authentication.

@page "/authentication/{action}"
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication

<RemoteAuthenticatorView Action="@Action" />

@code {
    [Parameter]
    public string Action { get; set; }
}

Custom user flows

The Microsoft Authentication Library (Microsoft.Authentication.WebAssembly.Msal, NuGet package) doesn't support AAD B2C user flows by default. Create custom user flows in developer code.

For more information on how to build a challenge for a custom user flow, see User flows in Azure Active Directory B2C.

Troubleshoot

Common errors

Misconfiguration of the app or Identity Provider (IP)

The most common errors are caused by incorrect configuration. The following are a few examples:
- Depending on the requirements of the scenario, a missing or incorrect Authority, Instance, Tenant ID, Tenant domain, Client ID, or Redirect URI prevents an app from authenticating clients.
- An incorrect access token scope prevents clients from accessing server web API endpoints.
- Incorrect or missing server API permissions prevent clients from accessing server web API endpoints.
- Running the app at a different port than is configured in the Redirect URI of the Identity Provider's app registration.
Configuration sections of this article's guidance show examples of the correct configuration. Carefully check each section of the article looking for app and IP misconfiguration.

If the configuration appears correct:
- Analyze application logs.
- Examine the network traffic between the client app and the IP or server app with the browser's developer tools. Often, an exact error message or a message with a clue to what's causing the problem is returned to the client by the IP or server app after making a request. Developer tools guidance is found in the following articles:
  - Google Chrome (Google documentation)
  - Microsoft Edge
  - Mozilla Firefox (Mozilla documentation)
- Decode the contents of a JSON Web Token (JWT) used for authenticating a client or accessing a server web API, depending on where the problem is occurring. For more information, see Inspect the content of a JSON Web Token (JWT).
The documentation team responds to document feedback and bugs in articles (open an issue from the This page feedback section) but is unable to provide product support. Several public support forums are available to assist with troubleshooting an app. We recommend the following:
The preceding forums are not owned or controlled by Microsoft.

For non-security, non-sensitive, and non-confidential reproducible framework bug reports, open an issue with the ASP.NET Core product unit. Don't open an issue with the product unit until you've thoroughly investigated the cause of a problem and can't resolve it on your own and with the help of the community on a public support forum. The product unit isn't able to troubleshoot individual apps that are broken due to simple misconfiguration or use cases involving third-party services. If a report is sensitive or confidential in nature or describes a potential security flaw in the product that attackers may exploit, see Reporting security issues and bugs (dotnet/aspnetcore GitHub repository).
Unauthorized client for AAD

info: Microsoft.AspNetCore.Authorization.DefaultAuthorizationService[2] Authorization failed. These requirements were not met: DenyAnonymousAuthorizationRequirement: Requires an authenticated user.

Login callback error from AAD:
- Error: unauthorized_client
- Description: AADB2C90058: The provided application is not configured to allow public clients.
To resolve the error:
1. In the Azure portal, access the app's manifest.
2. Set the allowPublicClient attribute to null or true.

Cookies and site data

User sign-in cookies
App cookies
Cached and stored site data

One approach to prevent lingering cookies and site data from interfering with testing and troubleshooting is to:

Configure a browser
- Use a browser for testing that you can configure to delete all cookie and site data each time the browser is closed.
- Make sure that the browser is closed manually or by the IDE for any change to the app, test user, or provider configuration.
Use a custom command to open a browser in incognito or private mode in Visual Studio:
- Open Browse With dialog box from Visual Studio's Run button.
- Select the Add button.
- Provide the path to your browser in the Program field. The following executable paths are typical installation locations for Windows 10. If your browser is installed in a different location or you aren't using Windows 10, provide the path to the browser's executable.
  - Microsoft Edge: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe
  - Google Chrome: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
  - Mozilla Firefox: C:\Program Files\Mozilla Firefox\firefox.exe
- In the Arguments field, provide the command-line option that the browser uses to open in incognito or private mode. Some browsers require the URL of the app.
  - Microsoft Edge: Use -inprivate.
  - Google Chrome: Use --incognito --new-window {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
  - Mozilla Firefox: Use -private -url {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
- Provide a name in the Friendly name field. For example, Firefox Auth Testing.
- Select the OK button.
- To avoid having to select the browser profile for each iteration of testing with an app, set the profile as the default with the Set as Default button.
- Make sure that the browser is closed by the IDE for any change to the app, test user, or provider configuration.

App upgrades

Clear the local system's NuGet package caches by executing dotnet nuget locals all --clear from a command shell.
Delete the project's bin and obj folders.
Restore and rebuild the project.
Delete all of the files in the deployment folder on the server prior to redeploying the app.

Note

Use of package versions incompatible with the app's target framework isn't supported. For information on a package, use the NuGet Gallery or FuGet Package Explorer.

Run the Server app

Select the Run button.
Use Debug > Start Debugging from the menu.
Press F5.

Inspect the user

User test component in the dotnet/aspnetcore GitHub repository

Note

Inspect the content of a JSON Web Token (JWT)

To decode a JSON Web Token (JWT), use Microsoft's jwt.ms tool. Values in the UI never leave your browser.

Example encoded JWT (shortened for display):

eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ilg1ZVhrNHh5b2pORnVtMWtsMll0djhkbE5QNC1j ... bQdHBHGcQQRbW7Wmo6SWYG4V_bU55Ug_PW4pLPr20tTS8Ct7_uwy9DWrzCMzpD-EiwT5IjXwlGX3IXVjHIlX50IVIydBoPQtadvT7saKo1G5Jmutgq41o-dmz6-yBMKV2_nXA25Q

Example JWT decoded by the tool for an app that authenticates against Azure AAD B2C:

{
  "typ": "JWT",
  "alg": "RS256",
  "kid": "X5eXk4xyojNFum1kl2Ytv8dlNP4-c57dO6QGTVBwaNk"
}.{
  "exp": 1610059429,
  "nbf": 1610055829,
  "ver": "1.0",
  "iss": "https://mysiteb2c.b2clogin.com/5cc15ea8-a296-4aa3-97e4-226dcc9ad298/v2.0/",
  "sub": "5ee963fb-24d6-4d72-a1b6-889c6e2c7438",
  "aud": "70bde375-fce3-4b82-984a-b247d823a03f",
  "nonce": "b2641f54-8dc4-42ca-97ea-7f12ff4af871",
  "iat": 1610055829,
  "auth_time": 1610055822,
  "idp": "idp.com",
  "tfp": "B2C_1_signupsignin"
}.[Signature]

Additional resources

Record the following information:

AAD B2C instance (for example, https://contoso.b2clogin.com/, which includes the trailing slash): The instance is the scheme and host of an Azure B2C app registration, which can be found by opening the Endpoints window from the App registrations page in the Azure portal.
AAD B2C Primary/Publisher/Tenant domain (for example, contoso.onmicrosoft.com): The domain is available as the Publisher domain in the Branding blade of the Azure portal for the registered app.

Navigate to Azure Active Directory in the Azure portal. Select App registrations in the sidebar. Select the New registration button.
Provide a Name for the app (for example, Blazor Standalone AAD B2C).
For Supported account types, select the multi-tenant option: Accounts in any organizational directory or any identity provider. For authenticating users with Azure AD B2C.
Set the Redirect URI drop down to Single-page application (SPA) and provide the following redirect URI: https://localhost/authentication/login-callback. If you know the production redirect URI for the Azure default host (for example, azurewebsites.net) or the custom domain host (for example, contoso.com), you can also add the production redirect URI at the same time that you're providing the localhost redirect URI. Be sure to include the port number for non-:443 ports in any production redirect URIs that you add.
If you're using an unverified publisher domain, confirm that Permissions > Grant admin consent to openid and offline_access permissions is selected. If the publisher domain is verified, this checkbox isn't present.
Select Register.

Note

Record the Application (client) ID (for example, 41451fa7-82d9-4673-8fa5-69eff5a761fd).

In Authentication > Platform configurations > Single-page application (SPA):

Confirm the Redirect URI of https://localhost/authentication/login-callback is present.
In the Implicit grant section, ensure that the checkboxes for Access tokens and ID tokens are not selected.
The remaining defaults for the app are acceptable for this experience.
Select the Save button.

In Home > Azure AD B2C > User flows:

Create a sign-up and sign-in user flow

At a minimum, select the Application claims > Display Name user attribute to populate the context.User.Identity.Name in the LoginDisplay component (Shared/LoginDisplay.razor).

Record the sign-up and sign-in user flow name created for the app (for example, B2C_1_signupsignin).

In an empty folder, replace the placeholders in the following command with the information recorded earlier and execute the command in a command shell:

dotnet new blazorwasm -au IndividualB2C --aad-b2c-instance "{AAD B2C INSTANCE}" --client-id "{CLIENT ID}" --domain "{TENANT DOMAIN}" -o {APP NAME} -ssp "{SIGN UP OR SIGN IN POLICY}"

Placeholder	Azure portal name	Example
`{AAD B2C INSTANCE}`	Instance	`https://contoso.b2clogin.com/`
`{APP NAME}`	—	`BlazorSample`
`{CLIENT ID}`	Application (client) ID	`41451fa7-82d9-4673-8fa5-69eff5a761fd`
`{SIGN UP OR SIGN IN POLICY}`	Sign-up/sign-in user flow	`B2C_1_signupsignin1`
`{TENANT DOMAIN}`	Primary/Publisher/Tenant domain	`contoso.onmicrosoft.com`

The output location specified with the -o|--output option creates a project folder if it doesn't exist and becomes part of the app's name.

Add a pair of MsalProviderOptions for openid and offline_access DefaultAccessTokenScopes:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("openid");
    options.ProviderOptions.DefaultAccessTokenScopes.Add("offline_access");
});

After creating the app, you should be able to:

Log into the app using an AAD user account.
Request access tokens for Microsoft APIs. For more information, see:
- Access token scopes
- Quickstart: Configure an application to expose web APIs.

Authentication package

If adding authentication to an app, manually add the Microsoft.Authentication.WebAssembly.Msal package to the app.

Note

The Microsoft.Authentication.WebAssembly.Msal package transitively adds the Microsoft.AspNetCore.Components.WebAssembly.Authentication package to the app.

Authentication service support

Program.cs:

builder.Services.AddMsalAuthentication(options =>
{
    builder.Configuration.Bind("AzureAdB2C", options.ProviderOptions.Authentication);
});

Configuration is supplied by the wwwroot/appsettings.json file:

{
  "AzureAdB2C": {
    "Authority": "{AAD B2C INSTANCE}{DOMAIN}/{SIGN UP OR SIGN IN POLICY}",
    "ClientId": "{CLIENT ID}",
    "ValidateAuthority": false
  }
}

Example:

{
  "AzureAdB2C": {
    "Authority": "https://contoso.b2clogin.com/contoso.onmicrosoft.com/B2C_1_signupsignin1",
    "ClientId": "41451fa7-82d9-4673-8fa5-69eff5a761fd",
    "ValidateAuthority": false
  }
}

Access token scopes

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("{SCOPE URI}");
});

Specify additional scopes with AdditionalScopesToConsent:

options.ProviderOptions.AdditionalScopesToConsent.Add("{ADDITIONAL SCOPE URI}");

For more information, see the following sections of the Additional scenarios article:

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.LoginMode = "redirect";
});

The default setting is popup, and the string value isn't case-sensitive.

Imports file

The Microsoft.AspNetCore.Components.Authorization namespace is made available throughout the app via the _Imports.razor file:

@using System.Net.Http
@using System.Net.Http.Json
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.Forms
@using Microsoft.AspNetCore.Components.Routing
@using Microsoft.AspNetCore.Components.Web
@using Microsoft.AspNetCore.Components.Web.Virtualization
@using Microsoft.AspNetCore.Components.WebAssembly.Http
@using Microsoft.JSInterop
@using {APPLICATION ASSEMBLY}
@using {APPLICATION ASSEMBLY}.Shared

Index page

<script src="_content/Microsoft.Authentication.WebAssembly.Msal/AuthenticationService.js"></script>

App component

The App component (App.razor) is similar to the App component found in Blazor Server apps:

The CascadingAuthenticationState component manages exposing the AuthenticationState to the rest of the app.
The AuthorizeRouteView component makes sure that the current user is authorized to access a given page or otherwise renders the RedirectToLogin component.
The RedirectToLogin component manages redirecting unauthorized users to the login page.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the App component (App.razor) in the generated app.
Inspect the App component (App.razor) in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

RedirectToLogin component

The RedirectToLogin component (Shared/RedirectToLogin.razor):

Manages redirecting unauthorized users to the login page.
Preserves the current URL that the user is attempting to access so that they can be returned to that page if authentication is successful.

@inject NavigationManager Navigation
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@code {
    protected override void OnInitialized()
    {
        Navigation.NavigateTo(
            $"authentication/login?returnUrl={Uri.EscapeDataString(Navigation.Uri)}");
    }
}

LoginDisplay component

The LoginDisplay component (Shared/LoginDisplay.razor) is rendered in the MainLayout component (Shared/MainLayout.razor) and manages the following behaviors:

For authenticated users:
- Displays the current username.
- Offers a button to log out of the app.
For anonymous users, offers the option to log in.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the LoginDisplay component in the generated app.
Inspect the LoginDisplay component in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

Authentication component

The page produced by the Authentication component (Pages/Authentication.razor) defines the routes required for handling different authentication stages.

The RemoteAuthenticatorView component:

Is provided by the Microsoft.AspNetCore.Components.WebAssembly.Authentication package.
Manages performing the appropriate actions at each stage of authentication.

@page "/authentication/{action}"
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication

<RemoteAuthenticatorView Action="@Action" />

@code {
    [Parameter]
    public string Action { get; set; }
}

Custom user flows

The Microsoft Authentication Library (Microsoft.Authentication.WebAssembly.Msal, NuGet package) doesn't support AAD B2C user flows by default. Create custom user flows in developer code.

For more information on how to build a challenge for a custom user flow, see User flows in Azure Active Directory B2C.

Troubleshoot

Common errors

Misconfiguration of the app or Identity Provider (IP)

The most common errors are caused by incorrect configuration. The following are a few examples:
- Depending on the requirements of the scenario, a missing or incorrect Authority, Instance, Tenant ID, Tenant domain, Client ID, or Redirect URI prevents an app from authenticating clients.
- An incorrect access token scope prevents clients from accessing server web API endpoints.
- Incorrect or missing server API permissions prevent clients from accessing server web API endpoints.
- Running the app at a different port than is configured in the Redirect URI of the Identity Provider's app registration.
Configuration sections of this article's guidance show examples of the correct configuration. Carefully check each section of the article looking for app and IP misconfiguration.

If the configuration appears correct:
- Analyze application logs.
- Examine the network traffic between the client app and the IP or server app with the browser's developer tools. Often, an exact error message or a message with a clue to what's causing the problem is returned to the client by the IP or server app after making a request. Developer tools guidance is found in the following articles:
  - Google Chrome (Google documentation)
  - Microsoft Edge
  - Mozilla Firefox (Mozilla documentation)
- Decode the contents of a JSON Web Token (JWT) used for authenticating a client or accessing a server web API, depending on where the problem is occurring. For more information, see Inspect the content of a JSON Web Token (JWT).
The documentation team responds to document feedback and bugs in articles (open an issue from the This page feedback section) but is unable to provide product support. Several public support forums are available to assist with troubleshooting an app. We recommend the following:
The preceding forums are not owned or controlled by Microsoft.

For non-security, non-sensitive, and non-confidential reproducible framework bug reports, open an issue with the ASP.NET Core product unit. Don't open an issue with the product unit until you've thoroughly investigated the cause of a problem and can't resolve it on your own and with the help of the community on a public support forum. The product unit isn't able to troubleshoot individual apps that are broken due to simple misconfiguration or use cases involving third-party services. If a report is sensitive or confidential in nature or describes a potential security flaw in the product that attackers may exploit, see Reporting security issues and bugs (dotnet/aspnetcore GitHub repository).
Unauthorized client for AAD

info: Microsoft.AspNetCore.Authorization.DefaultAuthorizationService[2] Authorization failed. These requirements were not met: DenyAnonymousAuthorizationRequirement: Requires an authenticated user.

Login callback error from AAD:
- Error: unauthorized_client
- Description: AADB2C90058: The provided application is not configured to allow public clients.
To resolve the error:
1. In the Azure portal, access the app's manifest.
2. Set the allowPublicClient attribute to null or true.

Cookies and site data

User sign-in cookies
App cookies
Cached and stored site data

One approach to prevent lingering cookies and site data from interfering with testing and troubleshooting is to:

Configure a browser
- Use a browser for testing that you can configure to delete all cookie and site data each time the browser is closed.
- Make sure that the browser is closed manually or by the IDE for any change to the app, test user, or provider configuration.
Use a custom command to open a browser in incognito or private mode in Visual Studio:
- Open Browse With dialog box from Visual Studio's Run button.
- Select the Add button.
- Provide the path to your browser in the Program field. The following executable paths are typical installation locations for Windows 10. If your browser is installed in a different location or you aren't using Windows 10, provide the path to the browser's executable.
  - Microsoft Edge: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe
  - Google Chrome: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
  - Mozilla Firefox: C:\Program Files\Mozilla Firefox\firefox.exe
- In the Arguments field, provide the command-line option that the browser uses to open in incognito or private mode. Some browsers require the URL of the app.
  - Microsoft Edge: Use -inprivate.
  - Google Chrome: Use --incognito --new-window {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
  - Mozilla Firefox: Use -private -url {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
- Provide a name in the Friendly name field. For example, Firefox Auth Testing.
- Select the OK button.
- To avoid having to select the browser profile for each iteration of testing with an app, set the profile as the default with the Set as Default button.
- Make sure that the browser is closed by the IDE for any change to the app, test user, or provider configuration.

App upgrades

Clear the local system's NuGet package caches by executing dotnet nuget locals all --clear from a command shell.
Delete the project's bin and obj folders.
Restore and rebuild the project.
Delete all of the files in the deployment folder on the server prior to redeploying the app.

Note

Use of package versions incompatible with the app's target framework isn't supported. For information on a package, use the NuGet Gallery or FuGet Package Explorer.

Run the Server app

Select the Run button.
Use Debug > Start Debugging from the menu.
Press F5.

Inspect the user

User test component in the dotnet/aspnetcore GitHub repository

Note

Inspect the content of a JSON Web Token (JWT)

To decode a JSON Web Token (JWT), use Microsoft's jwt.ms tool. Values in the UI never leave your browser.

Example encoded JWT (shortened for display):

eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ilg1ZVhrNHh5b2pORnVtMWtsMll0djhkbE5QNC1j ... bQdHBHGcQQRbW7Wmo6SWYG4V_bU55Ug_PW4pLPr20tTS8Ct7_uwy9DWrzCMzpD-EiwT5IjXwlGX3IXVjHIlX50IVIydBoPQtadvT7saKo1G5Jmutgq41o-dmz6-yBMKV2_nXA25Q

Example JWT decoded by the tool for an app that authenticates against Azure AAD B2C:

{
  "typ": "JWT",
  "alg": "RS256",
  "kid": "X5eXk4xyojNFum1kl2Ytv8dlNP4-c57dO6QGTVBwaNk"
}.{
  "exp": 1610059429,
  "nbf": 1610055829,
  "ver": "1.0",
  "iss": "https://mysiteb2c.b2clogin.com/5cc15ea8-a296-4aa3-97e4-226dcc9ad298/v2.0/",
  "sub": "5ee963fb-24d6-4d72-a1b6-889c6e2c7438",
  "aud": "70bde375-fce3-4b82-984a-b247d823a03f",
  "nonce": "b2641f54-8dc4-42ca-97ea-7f12ff4af871",
  "iat": 1610055829,
  "auth_time": 1610055822,
  "idp": "idp.com",
  "tfp": "B2C_1_signupsignin"
}.[Signature]

Additional resources

Record the following information:

AAD B2C instance (for example, https://contoso.b2clogin.com/, which includes the trailing slash): The instance is the scheme and host of an Azure B2C app registration, which can be found by opening the Endpoints window from the App registrations page in the Azure portal.
AAD B2C Primary/Publisher/Tenant domain (for example, contoso.onmicrosoft.com): The domain is available as the Publisher domain in the Branding blade of the Azure portal for the registered app.

Navigate to Azure Active Directory in the Azure portal. Select App registrations in the sidebar. Select the New registration button.
Provide a Name for the app (for example, Blazor Standalone AAD B2C).
For Supported account types, select the multi-tenant option: Accounts in any organizational directory or any identity provider. For authenticating users with Azure AD B2C.
Leave the Redirect URI drop down set to Web and provide the following redirect URI: https://localhost/authentication/login-callback. If you know the production redirect URI for the Azure default host (for example, azurewebsites.net) or the custom domain host (for example, contoso.com), you can also add the production redirect URI at the same time that you're providing the localhost redirect URI. Be sure to include the port number for non-:443 ports in any production redirect URIs that you add.
If you're using an unverified publisher domain, confirm that Permissions > Grant admin consent to openid and offline_access permissions is selected. If the publisher domain is verified, this checkbox isn't present.
Select Register.

Note

Record the Application (client) ID (for example, 41451fa7-82d9-4673-8fa5-69eff5a761fd).

In Authentication > Platform configurations > Web:

Confirm the Redirect URI of https://localhost/authentication/login-callback is present.
In the Implicit grant section, select the checkboxes for Access tokens and ID tokens.
The remaining defaults for the app are acceptable for this experience.
Select the Save button.

In Home > Azure AD B2C > User flows:

Create a sign-up and sign-in user flow

At a minimum, select the Application claims > Display Name user attribute to populate the context.User.Identity.Name in the LoginDisplay component (Shared/LoginDisplay.razor).

Record the sign-up and sign-in user flow name created for the app (for example, B2C_1_signupsignin).

In an empty folder, replace the placeholders in the following command with the information recorded earlier and execute the command in a command shell:

dotnet new blazorwasm -au IndividualB2C --aad-b2c-instance "{AAD B2C INSTANCE}" --client-id "{CLIENT ID}" --domain "{TENANT DOMAIN}" -o {APP NAME} -ssp "{SIGN UP OR SIGN IN POLICY}"

Placeholder	Azure portal name	Example
`{AAD B2C INSTANCE}`	Instance	`https://contoso.b2clogin.com/`
`{APP NAME}`	—	`BlazorSample`
`{CLIENT ID}`	Application (client) ID	`41451fa7-82d9-4673-8fa5-69eff5a761fd`
`{SIGN UP OR SIGN IN POLICY}`	Sign-up/sign-in user flow	`B2C_1_signupsignin1`
`{TENANT DOMAIN}`	Primary/Publisher/Tenant domain	`contoso.onmicrosoft.com`

The output location specified with the -o|--output option creates a project folder if it doesn't exist and becomes part of the app's name.

After creating the app, you should be able to:

Log into the app using an AAD user account.
Request access tokens for Microsoft APIs. For more information, see:
- Access token scopes
- Quickstart: Configure an application to expose web APIs.

Authentication package

If adding authentication to an app, manually add the Microsoft.Authentication.WebAssembly.Msal package to the app.

Note

The Microsoft.Authentication.WebAssembly.Msal package transitively adds the Microsoft.AspNetCore.Components.WebAssembly.Authentication package to the app.

Authentication service support

Program.cs:

builder.Services.AddMsalAuthentication(options =>
{
    builder.Configuration.Bind("AzureAdB2C", options.ProviderOptions.Authentication);
});

Configuration is supplied by the wwwroot/appsettings.json file:

{
  "AzureAdB2C": {
    "Authority": "{AAD B2C INSTANCE}{DOMAIN}/{SIGN UP OR SIGN IN POLICY}",
    "ClientId": "{CLIENT ID}",
    "ValidateAuthority": false
  }
}

Example:

{
  "AzureAdB2C": {
    "Authority": "https://contoso.b2clogin.com/contoso.onmicrosoft.com/B2C_1_signupsignin1",
    "ClientId": "41451fa7-82d9-4673-8fa5-69eff5a761fd",
    "ValidateAuthority": false
  }
}

Access token scopes

builder.Services.AddMsalAuthentication(options =>
{
    ...
    options.ProviderOptions.DefaultAccessTokenScopes.Add("{SCOPE URI}");
});

Specify additional scopes with AdditionalScopesToConsent:

options.ProviderOptions.AdditionalScopesToConsent.Add("{ADDITIONAL SCOPE URI}");

For more information, see the following sections of the Additional scenarios article:

Imports file

The Microsoft.AspNetCore.Components.Authorization namespace is made available throughout the app via the _Imports.razor file:

@using System.Net.Http
@using System.Net.Http.Json
@using Microsoft.AspNetCore.Components.Authorization
@using Microsoft.AspNetCore.Components.Forms
@using Microsoft.AspNetCore.Components.Routing
@using Microsoft.AspNetCore.Components.Web
@using Microsoft.AspNetCore.Components.Web.Virtualization
@using Microsoft.AspNetCore.Components.WebAssembly.Http
@using Microsoft.JSInterop
@using {APPLICATION ASSEMBLY}
@using {APPLICATION ASSEMBLY}.Shared

Index page

<script src="_content/Microsoft.Authentication.WebAssembly.Msal/AuthenticationService.js"></script>

App component

The App component (App.razor) is similar to the App component found in Blazor Server apps:

The CascadingAuthenticationState component manages exposing the AuthenticationState to the rest of the app.
The AuthorizeRouteView component makes sure that the current user is authorized to access a given page or otherwise renders the RedirectToLogin component.
The RedirectToLogin component manages redirecting unauthorized users to the login page.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the App component (App.razor) in the generated app.
Inspect the App component (App.razor) in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

RedirectToLogin component

The RedirectToLogin component (Shared/RedirectToLogin.razor):

Manages redirecting unauthorized users to the login page.
Preserves the current URL that the user is attempting to access so that they can be returned to that page if authentication is successful.

@inject NavigationManager Navigation
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@code {
    protected override void OnInitialized()
    {
        Navigation.NavigateTo(
            $"authentication/login?returnUrl={Uri.EscapeDataString(Navigation.Uri)}");
    }
}

LoginDisplay component

The LoginDisplay component (Shared/LoginDisplay.razor) is rendered in the MainLayout component (Shared/MainLayout.razor) and manages the following behaviors:

For authenticated users:
- Displays the current username.
- Offers a button to log out of the app.
For anonymous users, offers the option to log in.

Create an app provisioned for authentication from the default Blazor WebAssembly project template for the version of ASP.NET Core that you intend to use. Inspect the LoginDisplay component in the generated app.
Inspect the LoginDisplay component in reference source.

Note

Documentation links to .NET reference source usually load the repository's default branch, which represents the current development for the next release of .NET. To select a tag for a specific release, use the Switch branches or tags dropdown list. For more information, see How to select a version tag of ASP.NET Core source code (dotnet/AspNetCore.Docs #26205).

Authentication component

The page produced by the Authentication component (Pages/Authentication.razor) defines the routes required for handling different authentication stages.

The RemoteAuthenticatorView component:

Is provided by the Microsoft.AspNetCore.Components.WebAssembly.Authentication package.
Manages performing the appropriate actions at each stage of authentication.

@page "/authentication/{action}"
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication

<RemoteAuthenticatorView Action="@Action" />

@code {
    [Parameter]
    public string Action { get; set; }
}

Custom user flows

The Microsoft Authentication Library (Microsoft.Authentication.WebAssembly.Msal, NuGet package) doesn't support AAD B2C user flows by default. Create custom user flows in developer code.

For more information on how to build a challenge for a custom user flow, see User flows in Azure Active Directory B2C.

Troubleshoot

Common errors

Misconfiguration of the app or Identity Provider (IP)

The most common errors are caused by incorrect configuration. The following are a few examples:
- Depending on the requirements of the scenario, a missing or incorrect Authority, Instance, Tenant ID, Tenant domain, Client ID, or Redirect URI prevents an app from authenticating clients.
- An incorrect access token scope prevents clients from accessing server web API endpoints.
- Incorrect or missing server API permissions prevent clients from accessing server web API endpoints.
- Running the app at a different port than is configured in the Redirect URI of the Identity Provider's app registration.
Configuration sections of this article's guidance show examples of the correct configuration. Carefully check each section of the article looking for app and IP misconfiguration.

If the configuration appears correct:
- Analyze application logs.
- Examine the network traffic between the client app and the IP or server app with the browser's developer tools. Often, an exact error message or a message with a clue to what's causing the problem is returned to the client by the IP or server app after making a request. Developer tools guidance is found in the following articles:
  - Google Chrome (Google documentation)
  - Microsoft Edge
  - Mozilla Firefox (Mozilla documentation)
- Decode the contents of a JSON Web Token (JWT) used for authenticating a client or accessing a server web API, depending on where the problem is occurring. For more information, see Inspect the content of a JSON Web Token (JWT).
The documentation team responds to document feedback and bugs in articles (open an issue from the This page feedback section) but is unable to provide product support. Several public support forums are available to assist with troubleshooting an app. We recommend the following:
The preceding forums are not owned or controlled by Microsoft.

For non-security, non-sensitive, and non-confidential reproducible framework bug reports, open an issue with the ASP.NET Core product unit. Don't open an issue with the product unit until you've thoroughly investigated the cause of a problem and can't resolve it on your own and with the help of the community on a public support forum. The product unit isn't able to troubleshoot individual apps that are broken due to simple misconfiguration or use cases involving third-party services. If a report is sensitive or confidential in nature or describes a potential security flaw in the product that attackers may exploit, see Reporting security issues and bugs (dotnet/aspnetcore GitHub repository).
Unauthorized client for AAD

info: Microsoft.AspNetCore.Authorization.DefaultAuthorizationService[2] Authorization failed. These requirements were not met: DenyAnonymousAuthorizationRequirement: Requires an authenticated user.

Login callback error from AAD:
- Error: unauthorized_client
- Description: AADB2C90058: The provided application is not configured to allow public clients.
To resolve the error:
1. In the Azure portal, access the app's manifest.
2. Set the allowPublicClient attribute to null or true.

Cookies and site data

User sign-in cookies
App cookies
Cached and stored site data

One approach to prevent lingering cookies and site data from interfering with testing and troubleshooting is to:

Configure a browser
- Use a browser for testing that you can configure to delete all cookie and site data each time the browser is closed.
- Make sure that the browser is closed manually or by the IDE for any change to the app, test user, or provider configuration.
Use a custom command to open a browser in incognito or private mode in Visual Studio:
- Open Browse With dialog box from Visual Studio's Run button.
- Select the Add button.
- Provide the path to your browser in the Program field. The following executable paths are typical installation locations for Windows 10. If your browser is installed in a different location or you aren't using Windows 10, provide the path to the browser's executable.
  - Microsoft Edge: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe
  - Google Chrome: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe
  - Mozilla Firefox: C:\Program Files\Mozilla Firefox\firefox.exe
- In the Arguments field, provide the command-line option that the browser uses to open in incognito or private mode. Some browsers require the URL of the app.
  - Microsoft Edge: Use -inprivate.
  - Google Chrome: Use --incognito --new-window {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
  - Mozilla Firefox: Use -private -url {URL}, where the placeholder {URL} is the URL to open (for example, https://localhost:5001).
- Provide a name in the Friendly name field. For example, Firefox Auth Testing.
- Select the OK button.
- To avoid having to select the browser profile for each iteration of testing with an app, set the profile as the default with the Set as Default button.
- Make sure that the browser is closed by the IDE for any change to the app, test user, or provider configuration.

App upgrades

Clear the local system's NuGet package caches by executing dotnet nuget locals all --clear from a command shell.
Delete the project's bin and obj folders.
Restore and rebuild the project.
Delete all of the files in the deployment folder on the server prior to redeploying the app.

Note

Use of package versions incompatible with the app's target framework isn't supported. For information on a package, use the NuGet Gallery or FuGet Package Explorer.

Run the Server app

Select the Run button.
Use Debug > Start Debugging from the menu.
Press F5.

Inspect the user

User test component in the dotnet/aspnetcore GitHub repository

Note

Inspect the content of a JSON Web Token (JWT)

To decode a JSON Web Token (JWT), use Microsoft's jwt.ms tool. Values in the UI never leave your browser.

Example encoded JWT (shortened for display):

eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ilg1ZVhrNHh5b2pORnVtMWtsMll0djhkbE5QNC1j ... bQdHBHGcQQRbW7Wmo6SWYG4V_bU55Ug_PW4pLPr20tTS8Ct7_uwy9DWrzCMzpD-EiwT5IjXwlGX3IXVjHIlX50IVIydBoPQtadvT7saKo1G5Jmutgq41o-dmz6-yBMKV2_nXA25Q

Example JWT decoded by the tool for an app that authenticates against Azure AAD B2C:

{
  "typ": "JWT",
  "alg": "RS256",
  "kid": "X5eXk4xyojNFum1kl2Ytv8dlNP4-c57dO6QGTVBwaNk"
}.{
  "exp": 1610059429,
  "nbf": 1610055829,
  "ver": "1.0",
  "iss": "https://mysiteb2c.b2clogin.com/5cc15ea8-a296-4aa3-97e4-226dcc9ad298/v2.0/",
  "sub": "5ee963fb-24d6-4d72-a1b6-889c6e2c7438",
  "aud": "70bde375-fce3-4b82-984a-b247d823a03f",
  "nonce": "b2641f54-8dc4-42ca-97ea-7f12ff4af871",
  "iat": 1610055829,
  "auth_time": 1610055822,
  "idp": "idp.com",
  "tfp": "B2C_1_signupsignin"
}.[Signature]

Secure an ASP.NET Core Blazor WebAssembly standalone app with Azure Active Directory B2C

Authentication package

Authentication service support

Access token scopes

Login mode

Imports file

Index page

App component

RedirectToLogin component

LoginDisplay component

Authentication component

Custom user flows

Troubleshoot

Logging

Common errors

Cookies and site data

App upgrades

Run the Server app

Inspect the user

Inspect the content of a JSON Web Token (JWT)

Additional resources

Authentication package

Authentication service support

Access token scopes

Login mode

Imports file

Index page

App component

RedirectToLogin component

LoginDisplay component

Authentication component

Custom user flows

Troubleshoot

Common errors

Cookies and site data

App upgrades

Run the Server app

Inspect the user

Inspect the content of a JSON Web Token (JWT)

Additional resources

Authentication package

Authentication service support

Access token scopes

Login mode

Imports file

Index page

App component

RedirectToLogin component

LoginDisplay component

Authentication component

Custom user flows

Troubleshoot

Common errors

Cookies and site data

App upgrades

Run the Server app

Inspect the user

Inspect the content of a JSON Web Token (JWT)

Additional resources

Authentication package

Authentication service support

Access token scopes

Imports file

Index page

App component

RedirectToLogin component

LoginDisplay component

Authentication component

Custom user flows

Troubleshoot

Common errors

Cookies and site data

App upgrades

Run the Server app

Inspect the user

Inspect the content of a JSON Web Token (JWT)

Additional resources

Feedback

Additional resources

Additional resources