For our new friends:

Every app needs authentication and authorization. Logto is an Auth0 alternative designed for modern apps and SaaS products.

In this article, we will go through the steps to quickly build the Twilio sign-in experience (user authentication) with .NET Core (MVC) and  Logto.

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of .NET Core (MVC).
• A usable Twilio account.

Create an application in Logto

In you browser, open a new tab and enter the link of Logto Admin Console.

Once the page is loaded, in the "Get Started" section click the View all link to open the application framework list page.

Choose your application type

In the opening modal, scroll to the "Traditional web" section or filter all the available " Traditional web" frameworks using the quick filter checkboxes on the left.

Click the ".NET Core (MVC)" framework card to start creating your application.

Enter application name

Enter the application name, e.g., "Bookstore," and click "Create application."

🎉 Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.

Integrate Logto SDK

tip:

• The following demonstration is built on .NET Core 8.0. The SDK is compatible with .NET 6.0 or higher.
• The .NET Core sample projects are available in the GitHub repository.

Installation

Add the NuGet package to your project:

dotnet add package Logto.AspNetCore.Authentication

Add Logto authentication

Open Startup.cs (or Program.cs) and add the following code to register Logto authentication services:

Program.cs

using Logto.AspNetCore.Authentication;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddLogtoAuthentication(options =>
{
  options.Endpoint = builder.Configuration["Logto:Endpoint"]!;
  options.AppId = builder.Configuration["Logto:AppId"]!;
  options.AppSecret = builder.Configuration["Logto:AppSecret"];
});

The AddLogtoAuthentication method will do the following things:

• Set the default authentication scheme to LogtoDefaults.CookieScheme.
• Set the default challenge scheme to LogtoDefaults.AuthenticationScheme.
• Set the default sign-out scheme to LogtoDefaults.AuthenticationScheme.
• Add cookie and OpenID Connect authentication handlers to the authentication scheme.

Sign-in and sign-out flows

Before we proceed, there are two confusing terms in the .NET Core authentication middleware that we need to clarify:

1. CallbackPath: The URI that Logto will redirect the user back to after the user has signed in (the "redirect URI" in Logto)
2. RedirectUri: The URI that will be redirected to after necessary actions have been taken in the Logto authentication middleware.

The sign-in process can be illustrated as follows:

Similarly, .NET Core also has SignedOutCallbackPath and RedirectUri for the sign-out flow.

For the sack of clarity, we'll refer them as follows:

Term we use	.NET Core term
Logto redirect URI	CallbackPath
Logto post sign-out redirect URI	SignedOutCallbackPath
Application redirect URI	RedirectUri

Regarding redirect-based sign-in

1. This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
2. If you have multiple apps, you can use the same identity provider (Logto). Once the user signs in to one app, Logto will automatically complete the sign-in process when the user accesses another app.

To learn more about the rationale and benefits of redirect-based sign-in, see Logto sign-in experience explained.

Configure redirect URIs

nota:

In the following code snippets, we assume your app is running on http://localhost:3000/.

First, let's configure the Logto redirect URI. Add the following URI to the "Redirect URIs" list in the Logto application details page:

http://http://localhost:3000//Callback

To configure the Logto post sign-out redirect URI, add the following URI to the "Post sign-out redirect URIs" list in the Logto application details page:

http://http://localhost:3000//SignedOutCallback

Change the default paths

The Logto redirect URI has a default path of /Callback, and the Logto post sign-out redirect URI has a default path of /SignedOutCallback.

You can leave them as are if there's no special requirement. If you want to change it, you can set the CallbackPath and SignedOutCallbackPath property for LogtoOptions:

Program.cs

builder.Services.AddLogtoAuthentication(options =>
{
  // Other configurations...
  options.CallbackPath = "/Foo";
  options.SignedOutCallbackPath = "/Bar";
});

Remember to update the value in the Logto application details page accordingly.

Implement sign-in/sign-out buttons

First, add actions methods to your Controller, for example:

Controllers/HomeController.cs

public class HomeController : Controller
{
  public IActionResult SignIn()
  {
    // This will redirect the user to the Logto sign-in page.
    return Challenge(new AuthenticationProperties { RedirectUri = "/" });
  }

  // Use the `new` keyword to avoid conflict with the `ControllerBase.SignOut` method
  new public IActionResult SignOut()
  {
    // This will clear the authentication cookie and redirect the user to the Logto sign-out page
    // to clear the Logto session as well.
    return SignOut(new AuthenticationProperties { RedirectUri = "/" });
  }
}

Then, add the links to your View:

Views/Home/Index.cshtml

<p>Is authenticated: @User.Identity?.IsAuthenticated</p>
@if (User.Identity?.IsAuthenticated == true) {
  <a asp-controller="Home" asp-action="SignOut">Sign out</a>
} else {
  <a asp-controller="Home" asp-action="SignIn">Sign in</a>
}

It will show the "Sign in" link if the user is not authenticated, and show the "Sign out" link if the user is authenticated.

Test your integration:

Open your .NET Core (MVC) app to test if the integration works. When you click the "Sign In" button, the page should be redirected to a Logto sign-in page, and you should be able to create a new account by entering username and password and complete the sign-in process.

Add Twilio connector

To add or change SMS connector, go to the "Connector" tab in the Admin Console, then click on "Email and SMS connectors". From there, click "Set up" or go to detail page and click "Change SMS connector".

In the openning modal, select "Twilio" and click "Next".

On the next page, you will see a two-column layout with the README content on the left and configuration on the right.

Feel free to follow the README file in place or read the following section to complete the configuration process. If you follow the in-place guide, you can skip the next section.

Set up Twilio SMS connector

Register Twilio account

Create a new account on Twilio. (Jump to the next step if you already have one.)

Set up senders' phone numbers

Go to the Twilio console page and sign in with your Twilio account.

Purchase a phone number under "Phone Numbers" -> "Manage" -> "Buy a number".

ℹ️ Tip

Sometimes you may encounter the situation that SMS service is not supported in specific countries or areas. Pick a number from other regions to bypass.

Once we have a valid number claimed, navigate to the "Messaging" -> "Services". Create a new Message Service by clicking on the button.

Give a friendly service name and choose Notify my users as our service purpose. Following the next step, choose Phone Number as Sender Type, and add the phone number we just claimed to this service as a sender.

ℹ️ Note

Each phone number can only be linked with one messaging service.

Get account credentials

We will need the API credentials to make the connector work. Let's begin with the Twilio console page.

Click on the "Account" menu in the top-right corner, then go to the "API keys & tokens" page to get your Account SID and Auth token.

Back to "Messaging" -> "Services" settings page starting from the sidebar, and find the Sid of your service.

Compose the connector JSON

Fill out the accountSID, authToken and fromMessagingServiceSID fields with Account SID, Auth token and Sid of the corresponding messaging service.

You can add multiple SMS connector templates for different cases. Here is an example of adding a single template:

• Fill out the content field with arbitrary string-typed contents. Do not forget to leave {{code}} placeholder for random verification code.
• Fill out the usageType field with either Register, SignIn, ForgotPassword, Generic for different use cases. In order to enable full user flows, templates with usageType Register, SignIn, ForgotPassword and Generic are required.

Test Twilio SMS connector

You can enter a phone number and click on "Send" to see whether the settings can work before "Save and Done".

That's it. Don't forget to enable connector in sign-in experience.

Config types

Name	Type
accountSID	string
authToken	string
fromMessagingServiceSID	string
templates	Templates[]

Template Properties	Type	Enum values
content	string	N/A
usageType	enum string	'Register' | 'SignIn' | 'ForgotPassword' | 'Generic'

Reference

• Twilio - Error and Warning Dictionary

Save your configuration

Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save changes") and the Twilio connector should be available now.

Enable Twilio connector in Sign-in Experience

Switch to the "Sign-in experience" tab, then click the "Sign-up and sign-in" tab.

nota:

If it's the first time you enter the tab, you will see a quick introduction about Sign-in Experience and its basic configuration.

Select "Phone number" or "Email address or phone number" for the "Sign-up identifier" to provide sign-up for SMS passwordless sign-in, which may increase your conversion rate.

Finally, click "Save changes" on the bottom right corner.

Testing and Validation

Return to your .NET Core (MVC) app. You should now be able to sign in with Twilio. Enjoy!

Further readings

Protect your API For native and single page apps, you'll need to call one or more API endpoints to retrieve and update data.
Learn more about identifying who's who and keeping your API secure.

User management We know you care about user management and activities, as we also do.
Learn more about how to know your users and see the figures like DAU and MAU graphically.

Localization From one regional business to a global corporate, the willingness to offer the best user experience won't change.
You can change current language phrases or add a new language without friction.

Customer IAM series Our serial blog posts about Customer (or Consumer) Identity and Access Management, from 101 to advanced topics and beyond.