How to build Vonage SMS passwordless sign-in with SvelteKit

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 Vonage sign-in experience (user authentication) with SvelteKit and Logto.

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of SvelteKit.
A usable Vonage 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 "SvelteKit" 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 SvelteKit with Logto

tip:

The following demonstration is built on SvelteKit 2.0.0.
The sample project is available in the GitHub repository.

Installation

Install Logto SDK via your favorite package manager:

npm
pnpm
yarn

npm i @logto/sveltekit

pnpm add @logto/sveltekit

yarn add @logto/sveltekit

Add Logto hook

In your hooks.server.ts file, add the following code to inject the Logto hook into your server:

hooks.server.ts
import { handleLogto } from '@logto/sveltekit';

export const handle = handleLogto(
  {
    endpoint: '<your-logto-endpoint>',
    appId: '<your-logto-app-id>',
    appSecret: '<your-logto-app-secret>',
  },
  {
    encryptionKey: '<a-random-string>',
  }
);

Since these information are sensitive, it's recommended to use environment variables:

hooks.server.ts
import { handleLogto } from '@logto/sveltekit';
import { env } from '$env/dynamic/private';

export const handle = handleLogto(
  {
    endpoint: env.LOGTO_ENDPOINT,
    appId: env.LOGTO_APP_ID,
    appSecret: env.LOGTO_APP_SECRET,
  },
  {
    encryptionKey: env.LOGTO_COOKIE_ENCRYPTION_KEY,
  }
);

If you have multiple hooks, you can use the sequence() helper function to chain them:

hooks.server.ts
import { sequence } from '@sveltejs/kit/hooks';

export const handle = sequence(handleLogto, handleOtherHook);

Now you can access the Logto client in the locals object. For TypeScript, you can add the type to app.d.ts:

import type { LogtoClient, UserInfoResponse } from '@logto/sveltekit';

declare global {
  namespace App {
    interface Locals {
      logtoClient: LogtoClient;
      user?: UserInfoResponse;
    }
  }
}

We'll discuss the user object later.

note:

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

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.

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.

In the page where you want to implement sign-in and sign-out, define the following actions:

+page.server.ts
import type { Actions } from './$types';

export const actions: Actions = {
  signIn: async ({ locals }) => {
    await locals.logtoClient.signIn('http://localhost:3000/callback');
  },
  signOut: async ({ locals }) => {
    await locals.logtoClient.signOut('http://localhost:3000/');
  },
};

Then use these actions in your Svelte component:

+page.svelte
<form method="POST" action="?/{data.user ? 'signOut' : 'signIn'}">
  <button type="submit">Sign {data.user ? 'out' : 'in'}</button>
</form>

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 Vonage connector

SMS connector is a method used to send one-time passwords (OTPs) for authentication. It enables Phone number verification to support passwordless authentication, including SMS-based registration, sign-in, two-factor authentication (2FA), and account recovery. You can easily connect Vonage as your SMS provider. With the Logto SMS connector, you can set this up in just a few minutes.

To add a SMS connector, simply follow these steps:

Navigate to Console > Connector > Email and SMS connectors.
To add a new SMS connector, click the "Set up" button and select "Vonage".
Review the README documentation for your selected provider.
Complete the configuration fields in the "Parameter Configuration" section.
Customize the SMS template using the JSON editor.
Test your configuration by sending a verification code to your Phone number.

note:

If you are following the in-place Connector guide, you can skip the next section.

Set up Vonage SMS connector

Set up in Vonage

tip:

You can skip this step if you have already completed them.

To work with this connector, you will need to sign up for an account in Vonage. This will give you an API key and secret that you can use to access the APIs through this connector.

Once you have an account, you can find your API key and API secret at the top of the Vonage API Dashboard.

And you may need to rant a virtual number to send SMS messages.

See the Vonage SMS API for more information.

Set up in Logto

API Key: Your Vonage API key.
API Secret: Your Vonage API secret.
Brand Name: The brand name you want to use to send the SMS, this is also called the from field, see the Sender Identity for more information.
Templates: The templates you want to use to send the SMS, you can use the default templates or modify them as needed.

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 Vonage connector should be available now.

Once you create a connector successfully, you can enable phone number-based passwordless login and registration.

Navigate to Console > Sign-in experience > Sign-up and sign-in.
Set up sign-up methods (Optional):
1. Select "Phone number" or "Email or phone number" as the sign-up identifier.
2. "Verify at sign-up" is forced to be enabled. You can also enable "Create a password" on registration.
Set up sign-in methods:
1. Select Phone number as one of sign-in identifiers. You can provide multiple available identifiers (email, phone number, and username).
2. Select "Verification code" and / or "Password" as the authentication factor.
Click "Save changes" and test it in "Live preview".

In addition to registration and login via OTPs, you can also have password recovery and -based security verification enabled, as well as linking Phone number to profile. See End-user flows for more details.

Testing and Validation

Return to your SvelteKit app. You should now be able to sign in with Vonage. Enjoy!

Create an application in Logto​

Integrate SvelteKit with Logto​

Installation​

Add Logto hook​

Implement sign-in and sign-out​

Regarding redirect-based sign-in​

Configure redirect URIs​

Checkpoint: Test your application​

Add Vonage connector​

Set up Vonage SMS connector​

Set up in Vonage​

Set up in Logto​

Save your configuration​

Enable Vonage connector in Sign-in Experience​

Testing and Validation​

Further readings​