How to build Google sign-in with .NET Core (Blazor WebAssembly) and Logto

22 décembre 2024 · 2 minutes de lecture

The better identity infrastructure for developers

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 Google sign-in experience (user authentication) with .NET Core (Blazor WebAssembly) and Logto.

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of .NET Core (Blazor WebAssembly).
A usable Google account.

Create an application in Logto

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

Get Started

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

Framework List

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

Click the ".NET Core (Blazor WebAssembly)" 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

astuce:

The following demonstration is built on .NET Core 8.0 and Blorc.OpenIdConnect.
The .NET Core sample projects are available in the GitHub repository.

Installation

Add the NuGet package to your project:

dotnet add package Blorc.OpenIdConnect

Add script references

Include Blorc.Core/injector.js the index.html file:

index.html
<head>
  <!-- ... -->
  <script src="_content/Blorc.Core/injector.js"></script>
  <!-- ... -->
</head>

Register services

Add the following code to the Program.cs file:

Program.cs
using Blorc.OpenIdConnect;
using Blorc.Services;

builder.Services.AddBlorcCore();
builder.Services.AddAuthorizationCore();
builder.Services.AddBlorcOpenIdConnect(
    options =>
    {
        builder.Configuration.Bind("IdentityServer", options);
    });

var webAssemblyHost = builder.Build();

await webAssemblyHost
    .ConfigureDocumentAsync(async documentService =>
    {
        await documentService.InjectBlorcCoreJsAsync();
        await documentService.InjectOpenIdConnectAsync();
    });

await webAssemblyHost.RunAsync();

info:

There's no need to use the Microsoft.AspNetCore.Components.WebAssembly.Authentication package. The Blorc.OpenIdConnect package will take care of the authentication process.

Configure redirect URIs

Before we dive into the details, here's a quick overview of the end-user experience. The sign-in process can be simplified as follows:

Your app invokes the sign-in method.
The user is redirected to the Logto sign-in page. For native apps, the system browser is opened.
The user signs in and is redirected back to your app (configured as the redirect URI).

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.

remarque:

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

Configure redirect URIs

Switch to the application details page of Logto Console. Add a redirect URI http://localhost:3000/callback.

Just like signing in, users should be redirected to Logto for signing out of the shared session. Once finished, it would be great to redirect the user back to your website. For example, add http://localhost:3000/ as the post sign-out redirect URI section.

Then click "Save" to save the changes.

Configure application

Add the following code to the appsettings.json file:

appsettings.json
{
// ...
IdentityServer: {
  Authority: 'https://<your-logto-endpoint>/oidc',
  ClientId: '<your-logto-app-id>',
  PostLogoutRedirectUri: 'http://localhost:3000/',
  RedirectUri: 'http://localhost:3000/callback',
  ResponseType: 'code',
  Scope: 'openid profile', // Add more scopes if needed
},
}

Remember to add the RedirectUri and PostLogoutRedirectUri to the list of allowed redirect URIs in the Logto application settings. They are both the URL of your WASM application.

Add `AuthorizeView` component

In the Razor pages that require authentication, add the AuthorizeView component. Let's assume it's the Home.razor page:

Pages/Home.razor
@using Microsoft.AspNetCore.Components.Authorization
@page "/"

<AuthorizeView>
    <Authorized>
        @* Signed in view *@
        <button @onclick="OnLogoutButtonClickAsync">
            Sign out
        </button>
    </Authorized>
    <NotAuthorized>
        @* Unauthenticated view *@
        <button @onclick="OnLoginButtonClickAsync">
            Sign in
        </button>
    </NotAuthorized>
</AuthorizeView>

Set up authentication

In the Home.razor.cs file (create it if it doesn't exist), add the following code:

Pages/Home.razor.cs
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
using Blorc.OpenIdConnect;
using Microsoft.AspNetCore.Components.Authorization;

[Authorize]
public partial class Home : ComponentBase
{
    [Inject]
    public required IUserManager UserManager { get; set; }

    public User<Profile>? User { get; set; }

    [CascadingParameter]
    protected Task<AuthenticationState>? AuthenticationStateTask { get; set; }

    protected override async Task OnInitializedAsync()
    {
        User = await UserManager.GetUserAsync<User<Profile>>(AuthenticationStateTask!);
    }

    private async Task OnLoginButtonClickAsync(MouseEventArgs obj)
    {
        await UserManager.SignInRedirectAsync();
    }

    private async Task OnLogoutButtonClickAsync(MouseEventArgs obj)
    {
        await UserManager.SignOutRedirectAsync();
    }
}

Once the user is authenticated, the User property will be populated with the user information.

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 local storage and sign out.

Test your integration:

Open your .NET Core (Blazor WASM) 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 Google connector

To add a social connector, go to the "Connector" tab in the Admin Console, then click on "Social connectors". From there, click "Add social connector".

In the openning modal, select "Google" 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 Google OAuth app

Set up a project in the Google API Console

Visit the Google API Console and sign in with your Google account.
Click the Select a project button on the top menu bar, and click the New Project button to create a project.
In your newly created project, click the APIs & Services to enter the APIs & Services menu.

On the left APIs & Services menu, click the OAuth consent screen button.
Choose the User Type you want, and click the Create button. (Note: If you select External as your User Type, you will need to add test users later.)

Now you will be on the Edit app registration page.

Follow the instructions to fill out the OAuth consent screen form.
Click SAVE AND CONTINUE to continue.

Config scopes

Click ADD OR REMOVE SCOPES and select ../auth/userinfo.email, ../auth/userinfo.profile and openid in the popup drawer, and click UPDATE to finish.
Fill out the form as you need.
Click SAVE AND CONTINUE to continue.

Add test users (External user type only)

Click ADD USERS and add test users to allow these users to access your application while testing.
Click SAVE AND CONTINUE to continue.

Now you should have the Google OAuth 2.0 consent screen configured.

Obtain OAuth 2.0 credentials

On the left APIs & Services menu, click the Credentials button.
On the Credentials page, click the + CREATE CREDENTIALS button on the top menu bar, and select OAuth client ID.
On the Create OAuth client ID page, select Web application as the application type.
Fill out the basic information for your application.
Click + Add URI to add an authorized domain to the Authorized JavaScript origins section. This is the domain that your logto authorization page will be served from. In our case, this will be ${your_logto_origin}. e.g.https://logto.dev.
Click + Add URI in the **Authorized redirect URIs** section to set up the **Authorized redirect URIs**, which redirect the user to the application after logging in. In our case, this will be ${your_logto_endpoint}/callback/${connector_id}. e.g. https://logto.dev/callback/${connector_id}. The connector_id can be found on the top bar of the Logto Admin Console connector details page.
Click Create to finish and then you will get the Client ID and Client Secret.

References

Config types

Name	Type
clientId	string
clientSecret	string

Google developer docs

Google Identity: Setting up OAuth 2.0

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 Google connector should be available now.

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

remarque:

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

Sign-in Experience tab

Select "None" for the "Sign-up identifier" to provide minimum sign-up effort for Google sign-in, which may increase your conversion rate.

In the "Social sign-in" section, add "Add Social Connector" and choose "Google". Then you should be able to see a button with text "Continue with Google" in the preview section.

Save changes

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

Testing and Validation

Return to your .NET Core (Blazor WebAssembly) app. You should now be able to sign in with Google. Enjoy!

Create an application in Logto​

Choose your application type​

Enter application name​

Integrate Logto SDK​

Installation​

Add script references​

Register services​

Configure redirect URIs​

Regarding redirect-based sign-in​

Configure redirect URIs​

Configure application​

Add AuthorizeView component​

Set up authentication​

Checkpoint: Test your application​

Add Google connector​

Set up Google OAuth app​

Set up a project in the Google API Console​

Configure your consent screen​

Config OAuth consent screen​

Config scopes​

Add test users (External user type only)​

Obtain OAuth 2.0 credentials​

References​

Config types​

Google developer docs​

Save your configuration​

Enable Google connector in Sign-in Experience​

Testing and Validation​

Further readings​

Create an application in Logto

Choose your application type

Enter application name

Integrate Logto SDK

Installation

Add script references

Register services

Configure redirect URIs

Regarding redirect-based sign-in

Configure redirect URIs

Configure application

Add `AuthorizeView` component

Set up authentication

Checkpoint: Test your application

Add Google connector

Set up Google OAuth app

Set up a project in the Google API Console

Configure your consent screen

Config OAuth consent screen

Config scopes

Add test users (External user type only)

Obtain OAuth 2.0 credentials

References

Config types

Google developer docs

Save your configuration

Enable Google connector in Sign-in Experience

Testing and Validation

Further readings