Skip to content

enable-authentication-web-application-options.md

Latest commit

 

History

History
382 lines (286 loc) · 16.6 KB

enable-authentication-web-application-options.md

File metadata and controls

382 lines (286 loc) · 16.6 KB
title Enable web app authentication options using Azure Active Directory B2C
description This article discusses several ways to enable web app authentication options.
author kengaderdus
manager CelesteDG
ms.service azure-active-directory
ms.topic reference
ms.date 01/11/2024
ms.author kengaderdus
ms.subservice b2c
ms.custom b2c-support

Enable authentication options in a web app by using Azure AD B2C

[!INCLUDE active-directory-b2c-end-of-sale-notice-b]

This article describes how to enable, customize, and enhance the Azure Active Directory B2C (Azure AD B2C) authentication experience for your web application.

Before you start, it's important to familiarize yourself with the following articles:

[!INCLUDE active-directory-b2c-app-integration-custom-domain]

To use a custom domain and your tenant ID in the authentication URL, follow the guidance in Enable custom domains. Under the project root folder, open the appsettings.json file. This file contains information about your Azure AD B2C identity provider.

In the appsettings.json file, do the following:

  • Update the Instance entry with your custom domain.
  • Update the Domain entry with your tenant ID. For more information, see Use tenant ID.

The following JSON shows the app settings before the change:

"AzureAdB2C": {
  "Instance": "https://contoso.b2clogin.com",
  "Domain": "tenant-name.onmicrosoft.com",
  ...
}

The following JSON shows the app settings after the change:

"AzureAdB2C": {
  "Instance": "https://login.contoso.com",
  "Domain": "00000000-0000-0000-0000-000000000000",
  ...
}

Support advanced scenarios

The AddMicrosoftIdentityWebAppAuthentication method in the Microsoft identity platform API lets developers add code for advanced authentication scenarios or subscribe to OpenIdConnect events. For example, you can subscribe to OnRedirectToIdentityProvider, which allows you to customize the authentication request your app sends to Azure AD B2C.

To support advanced scenarios, open the Startup.cs file and, in the ConfigureServices function, replace AddMicrosoftIdentityWebAppAuthentication with the following code snippet:

// Configuration to sign-in users with Azure AD B2C

//services.AddMicrosoftIdentityWebAppAuthentication(Configuration, "AzureAdB2C");

services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
        .AddMicrosoftIdentityWebApp(options =>
{
    Configuration.Bind("AzureAdB2C", options);
    options.Events ??= new OpenIdConnectEvents();
    options.Events.OnRedirectToIdentityProvider += OnRedirectToIdentityProviderFunc;
});

The preceding code adds the OnRedirectToIdentityProvider event with a reference to the OnRedirectToIdentityProviderFunc method. Add the following code snippet to the Startup.cs class.

private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
    // Custom code here
    
    // Don't remove this line
    await Task.CompletedTask.ConfigureAwait(false);
}

You can pass parameters between your controller and the OnRedirectToIdentityProvider function by using context parameters.

[!INCLUDE active-directory-b2c-app-integration-login-hint]

  1. If you're using a custom policy, add the required input claim, as described in Set up direct sign-in.

  2. Complete the Support advanced scenarios procedure.

  3. Add the following line of code to the OnRedirectToIdentityProvider function:

    private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
  context.ProtocolMessage.LoginHint = "[email protected]";
  
  // More code
  await Task.CompletedTask.ConfigureAwait(false);
}

[!INCLUDE active-directory-b2c-app-integration-domain-hint]

  1. Check the domain name of your external identity provider. For more information, see Redirect sign-in to a social provider.

  2. Complete the Support advanced scenarios procedure.

  3. In the OnRedirectToIdentityProviderFunc function, add the following line of code to the OnRedirectToIdentityProvider function:

    private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
  context.ProtocolMessage.DomainHint = "facebook.com";
  
  // More code
  await Task.CompletedTask.ConfigureAwait(false);
}

[!INCLUDE active-directory-b2c-app-integration-ui-locales]

  1. Configure language customization.

  2. Complete the Support advanced scenarios procedure.

  3. Add the following line of code to the OnRedirectToIdentityProvider function:

    private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
  context.ProtocolMessage.UiLocales = "es";

  // More code
  await Task.CompletedTask.ConfigureAwait(false);
}

[!INCLUDE active-directory-b2c-app-integration-custom-parameters]

  1. Configure the ContentDefinitionParameters element.

  2. Complete the Support advanced scenarios procedure.

  3. Add the following line of code to the OnRedirectToIdentityProvider function:

    private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
  context.ProtocolMessage.Parameters.Add("campaignId", "123");

  // More code
  await Task.CompletedTask.ConfigureAwait(false);
}

[!INCLUDE active-directory-b2c-app-integration-id-token-hint]

  1. Complete the Support advanced scenarios procedure.

  2. In your custom policy, define an ID token hint technical profile.

  3. Add the following line of code to the OnRedirectToIdentityProvider function:

    private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
  // The idTokenHint variable holds your ID token 
  context.ProtocolMessage.IdTokenHint = idTokenHint

  // More code
  await Task.CompletedTask.ConfigureAwait(false);
}

Account controller

If you want to customize the SignIn, SignUp, or SignOut actions, we encourage you to create your own controller. Having your own controller allows you to pass parameters between your controller and the authentication library. AccountController is part of Microsoft.Identity.Web.UI NuGet package, which handles the sign-in and sign-out actions. You can find its implementation in the Microsoft Identity Web library.

Add the Account controller

In your Visual Studio project, right-click the Controllers folder, and then add a new Controller. Select MVC - Empty Controller, and then provide the name MyAccountController.cs.

The following code snippet demonstrates a custom MyAccountController with the SignIn action.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;


namespace mywebapp.Controllers
{
    [AllowAnonymous]
    [Area("MicrosoftIdentity")]
    [Route("[area]/[controller]/[action]")]
    public class MyAccountController : Controller
    {

        [HttpGet("{scheme?}")]
        public IActionResult SignIn([FromRoute] string scheme)
        {
            scheme ??= OpenIdConnectDefaults.AuthenticationScheme;
            var redirectUrl = Url.Content("~/");
            var properties = new AuthenticationProperties { RedirectUri = redirectUrl };
            return Challenge(properties, scheme);
        }

    }
}

In the _LoginPartial.cshtml view, change the sign-in link to your controller.

<form method="get" asp-area="MicrosoftIdentity" asp-controller="MyAccount" asp-action="SignIn">

Pass the Azure AD B2C policy ID

The following code snippet demonstrates a custom MyAccountController with the SignIn and SignUp action. The action passes a parameter named policy to the authentication library. This allows you to provide the correct Azure AD B2C policy ID for the specific action.

public IActionResult SignIn([FromRoute] string scheme)
{
    scheme ??= OpenIdConnectDefaults.AuthenticationScheme;
    var redirectUrl = Url.Content("~/");
    var properties = new AuthenticationProperties { RedirectUri = redirectUrl };
    properties.Items["policy"] = "B2C_1_SignIn";
    return Challenge(properties, scheme);
}

public IActionResult SignUp([FromRoute] string scheme)
{
    scheme ??= OpenIdConnectDefaults.AuthenticationScheme;
    var redirectUrl = Url.Content("~/");
    var properties = new AuthenticationProperties { RedirectUri = redirectUrl };
    properties.Items["policy"] = "B2C_1_SignUp";
    return Challenge(properties, scheme);
}

In the _LoginPartial.cshtml view, change the asp-controller value to MyAccountController for any other authentication links, such as sign-up or edit profile.

Pass custom parameters

The following code snippet demonstrates a custom MyAccountController with the SignIn action. The action passes a parameter named campaign_id to the authentication library.

public IActionResult SignIn([FromRoute] string scheme)
{
    scheme ??= OpenIdConnectDefaults.AuthenticationScheme;
    var redirectUrl = Url.Content("~/");
    var properties = new AuthenticationProperties { RedirectUri = redirectUrl };
    properties.Items["policy"] = "B2C_1_SignIn";
    properties.Items["campaign_id"] = "1234";
    return Challenge(properties, scheme);
}

Complete the Support advanced scenarios procedure and then, in the OnRedirectToIdentityProvider method, read the custom parameter:

private async Task OnRedirectToIdentityProviderFunc(RedirectContext context)
{
    // Read the custom parameter
    var campaign_id = context.Properties.Items.FirstOrDefault(x => x.Key == "campaign_id").Value;

    // Add your custom code here
    if (campaign_id != null)
    {
        // Send parameter to authentication request
        context.ProtocolMessage.SetParameter("campaign_id", campaign_id);
    }
    
    await Task.CompletedTask.ConfigureAwait(false);
}

Secure your logout redirect

After logout, the user is redirected to the URI specified in the post_logout_redirect_uri parameter, regardless of the reply URLs that have been specified for the application. However, if a valid id_token_hint is passed and the Require ID Token in logout requests is turned on, Azure AD B2C verifies that the value of post_logout_redirect_uri matches one of the application's configured redirect URIs before performing the redirect. If no matching reply URL was configured for the application, an error message is displayed and the user is not redirected.

To support a secured logout redirect in your application, first follow the steps in the Account controller and Support advanced scenarios sections. Then follow the steps below:

  1. In MyAccountController.cs controller, add a SignOut action using the following code snippet:

    [HttpGet("{scheme?}")]
public async Task<IActionResult> SignOutAsync([FromRoute] string scheme)
{
    scheme ??= OpenIdConnectDefaults.AuthenticationScheme;

    //obtain the id_token
    var idToken = await HttpContext.GetTokenAsync("id_token");
    //send the id_token value to the authentication middleware
    properties.Items["id_token_hint"] = idToken;            

    return SignOut(properties,CookieAuthenticationDefaults.AuthenticationScheme,scheme);
}

  2. In the Startup.cs class, parse the id_token_hint value and append the value to the authentication request. The following code snippet demonstrates how to pass the id_token_hint value to the authentication request:

    private async Task OnRedirectToIdentityProviderForSignOutFunc(RedirectContext context)
{
    var id_token_hint = context.Properties.Items.FirstOrDefault(x => x.Key == "id_token_hint").Value;
    if (id_token_hint != null)
    {
        // Send parameter to authentication request
        context.ProtocolMessage.SetParameter("id_token_hint", id_token_hint);
    }

    await Task.CompletedTask.ConfigureAwait(false);
}

  3. In the ConfigureServices function, add the SaveTokens option for Controllers have access to the id_token value:

    services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApp(options =>
    {
        Configuration.Bind("AzureAdB2C", options);
        options.Events ??= new OpenIdConnectEvents();        
        options.Events.OnRedirectToIdentityProviderForSignOut += OnRedirectToIdentityProviderForSignOutFunc;
        options.SaveTokens = true;
    });

  4. In the appsettings.json configuration file, add your logout redirect URI path to SignedOutCallbackPath key.

    "AzureAdB2C": {
  "Instance": "https://<your-tenant-name>.b2clogin.com",
  "ClientId": "<web-app-application-id>",
  "Domain": "<your-b2c-domain>",
  "SignedOutCallbackPath": "/signout/<your-sign-up-in-policy>",
  "SignUpSignInPolicyId": "<your-sign-up-in-policy>"
}

In the above example, the post_logout_redirect_uri passed into the logout request will be in the format: https://your-app.com/signout/<your-sign-up-in-policy>. This URL must be added to the Application Registration's reply URL's.

Role-based access control

With authorization in ASP.NET Core you can check to see whether users are authorized to access a protected resource by using one of the following methods:

In the ConfigureServices method, add the AddAuthorization method, which adds the authorization model. The following example creates a policy named EmployeeOnly. The policy checks to verify that a claim EmployeeNumber exists. The value of the claim must be one of the following IDs: 1, 2, 3, 4, or 5.

services.AddAuthorization(options =>
    {
        options.AddPolicy("EmployeeOnly", policy =>
              policy.RequireClaim("EmployeeNumber", "1", "2", "3", "4", "5"));
    });

You control authorization in ASP.NET Core by using AuthorizeAttribute and its various parameters. In its most basic form, applying the Authorize attribute to a controller, action, or Razor Page limits access to that component's authenticated users.

You apply policies to controllers by using the Authorize attribute with the policy name. The following code limits access to the Claims action to users who are authorized by the EmployeeOnly policy:

[Authorize(Policy = "EmployeeOnly")]
public IActionResult Claims()
{
    return View();
}

Next steps