How to build OIDC enterprise SSO with .NET Core (Razor Pages)

For our new friends:

Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.

We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.

In this article, we will go through the steps to quickly build the OIDC enterprise SSO sign-in experience (user authentication) with .NET Core (Razor Pages) and Logto.

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of .NET Core (Razor Pages).
A usable OIDC enterprise SSO account.

Create an application in Logto

Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).

To create your Traditional web application, simply follow these steps:

Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
In the opening modal, click the "Traditional web" section or filter all the available "Traditional web" frameworks using the quick filter checkboxes on the left. Click the ".NET Core (Razor Pages)" framework card to start creating your application.
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 .NET Core (Razor Pages) 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.

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

CallbackPath: The URI that Logto will redirect the user back to after the user has signed in (the "redirect URI" in Logto)
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

This authentication process follows the OpenID Connect (OIDC) protocol, and Logto enforces strict security measures to protect user sign-in.
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

note:

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://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://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 the handler methods to your PageModel, for example:

Pages/Index.cshtml.cs
public class IndexModel : PageModel
{
  public async Task OnPostSignInAsync()
  {
    await HttpContext.ChallengeAsync(new AuthenticationProperties
    {
      RedirectUri = "/"
    });
  }

  public async Task OnPostSignOutAsync()
  {
    await HttpContext.SignOutAsync(new AuthenticationProperties
    {
      RedirectUri = "/"
    });
  }
}

Then, add the buttons to your Razor page:

Pages/Index.cshtml
<p>Is authenticated: @User.Identity?.IsAuthenticated</p>
<form method="post">
  @if (User.Identity?.IsAuthenticated == true) {
    <button type="submit" asp-page-handler="SignOut">Sign out</button>
  } else {
    <button type="submit" asp-page-handler="SignIn">Sign in</button>
  }
</form>

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

Checkpoint: Test your application

Now, you can test your application:

Run your application, you will see the sign-in button.
Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
After you signed in, you will be redirected back to your application and see the sign-out button.
Click the sign-out button to clear token storage and sign out.

Add OIDC enterprise SSO connector

To simplify access management and gain enterprise-level safeguards for your big clients, connect with .NET Core (Razor Pages) as a federated identity provider. The Logto enterprise SSO connector helps you establish this connection in minutes by allowing several parameter inputs.

To add an enterprise SSO connector, simply follow these steps:

Navigate to Logto console > Enterprise SSO.

SSO page

Click "Add enterprise connector" button and choose your SSO provider type. Choose from prebuilt connectors for Microsoft Entra ID (Azure AD), Google Workspace, and Okta, or create a custom SSO connection using the standard OpenID Connect (OIDC) or SAML protocol.
Provide a unique name (e.g., SSO sign-in for Acme Company).

Select your SSO provider

Configure the connection with your IdP in the "Connection" tab. Check the guides above for each connector types.

SSO connection

Customize the SSO experience and enterprise’s email domain in the "Experience" tab. Users sign in with the SSO-enabled email domain will be redirected to SSO authentication.

SSO experience

Save changes.

Set up OIDC application on your IdP

Step 1: Create an OIDC application on your IdP

Initiate the OIDC SSO integration by creating an application on the IdP side. You will need to provide the following configurations from the Logto server.

Callback URI: The Logto Callback URI, also known as the Redirect URI or Reply URL, is a specific endpoint or URL that the IdP uses to redirect the user's browser after successful authentication. After a user successfully authenticates with the IdP, the IdP redirects the user's browser back to this designated URI along with an authorization code. Logto will complete the authentication process based on authorization code received from this URI.

Fill in the Logto Callback URI in your IdP OIDC application settings form and continue to create the application. (Most of the OIDC IdPs provide a wide range of application types to choose from. To create a web-based SSO connector on Logto, please choose the Web Application type.)

Step 2: Configure OIDC SSO on Logto

After successfully creating an OIDC application on the IdP side, you will need to provide the IdP configurations back to Logto. Navigate to the Connection tab, and fill in the following configurations:

Client ID: A unique identifier assigned to your OIDC application by the IdP. This identifier is used by Logto to identify and authenticate the application during the OIDC flow.
Client Secret: A confidential secret shared between Logto and the IdP. This secret is used to authenticate the OIDC application and secure the communication between Logto and the IdP.
Issuer: The issuer URL, a unique identifier for the IdP, specifying the location where the OIDC identity provider can be found. It is a crucial part of the OIDC configuration as it helps Logto discover the necessary endpoints. To make the configuration process easier. Logto will automatically fetch the required OIDC endpoints and configurations. This is done by utilizing the issuer you provided and making a call to the IdP's OIDC discover endpoints. It is imperative to ensure that the issuer endpoint is valid and accurately configured to enable Logto to retrieve the required information correctly. After a successful fetch request, you should be able to see the parsed IdP configurations under the issuers section.
Scope: A space-separated list of strings defining the desired permissions or access levels requested by Logto during the OIDC authentication process. The scope parameter allows you to specify what information and access Logto is requesting from the IdP. The scope parameter is optional. Regardless of the custom scope settings, Logto will always send the openid, profile and email scopes to the IdP. This is to ensure that Logto can retrieve the user's identity information and email address properly from the IdP. You may add additional scopes to the scope parameter to request for more information from the IdP.

Step 3: Set email domains and enable the SSO connector

Provide the email domains of your organization on Logto’s connector SSO experience tab. This will enable the SSO connector as an authentication method for those users.

Users with email addresses in the specified domains will be redirected to use your SSO connector as their only authentication method.

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 OIDC enterprise SSO connector should be available now.

You don’t need to configure enterprise connectors individually, Logto simplifies SSO integration into your applications with just one click.

Navigate to: Console > Sign-in experience > Sign-up and sign-in.
Enable the "Enterprise SSO" toggle.
Save changes.

Once enabled, a "Single Sign-On" button will appear on your sign-in page. Enterprise users with SSO-enabled email domains can access your services using their enterprise identity providers (IdPs).

Auto detect SSO sign-in via email domain

To learn more about the SSO user experience, including SP-initiated SSO and IdP-initiated SSO, refer to User flows: Enterprise SSO.

Testing and Validation

Return to your .NET Core (Razor Pages) app. You should now be able to sign in with OIDC enterprise SSO. Enjoy!

Create an application in Logto​

Integrate .NET Core (Razor Pages) SDK​

Installation​

Add Logto authentication​

Sign-in and sign-out flows​

Regarding redirect-based sign-in​

Configure redirect URIs​

Change the default paths​

Implement sign-in/sign-out buttons​

Checkpoint: Test your application​

Add OIDC enterprise SSO connector​

Set up OIDC application on your IdP​

Step 1: Create an OIDC application on your IdP​

Step 2: Configure OIDC SSO on Logto​

Step 3: Set email domains and enable the SSO connector​

Save your configuration​

Enable OIDC enterprise SSO connector in Sign-in Experience​

Testing and Validation​

Further readings​