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 SMTP sign-in experience (user authentication) with Chrome extension and Logto.

Prerequisites

• A running Logto instance. Check out the introduction page to get started.
• Basic knowledge of Chrome extension.
• A usable SMTP 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 Single page app application, simply follow these steps:

1. 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.
2. In the opening modal, click the "Single page app" section or filter all the available "Single page app" frameworks using the quick filter checkboxes on the left. Click the "Chrome extension" framework card to start creating your application.
3. 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 Chrome extension with Logto

tip:

• The following demonstration was tested on Chrome v123.0.6312.87 (arm64). Other versions should also work, as long as they support the chrome APIs used in the SDK.
• The sample project is available on our GitHub repository.

Installation

npm

npm i @logto/chrome-extension

Yarn

yarn add @logto/chrome-extension

pnpm

pnpm add @logto/chrome-extension

The authentication flow

Assuming you put a "Sign in" button in your Chrome extension's popup, the authentication flow will look like this:

For other interactive pages in your extension, you just need to replace the Extension popup participant with the page's name. In this tutorial, we will focus on the popup page.

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.

Update the manifest.json

Logto SDK requires the following permissions in the manifest.json:

manifest.json

{
  "permissions": ["identity", "storage"],
  "host_permissions": ["https://*.logto.app/*"]
}

• permissions.identity: Required for the Chrome Identity API, which is used to sign in and sign out.
• permissions.storage: Required for storing the user's session.
• host_permissions: Required for the Logto SDK to communicate with the Logto APIs.

note:

If you are using a custom domain on Logto Cloud, you need to update the host_permissions to match your domain.

Set up a background script (service worker)

In your Chrome extension's background script, initialize the Logto SDK:

service-worker.js

import LogtoClient from '@logto/chrome-extension';

export const logtoClient = new LogtoClient({
  endpoint: '<your-logto-endpoint>'
  appId: '<your-logto-app-id>',
});

Replace <your-logto-endpoint> and <your-logto-app-id> with the actual values. You can find these values in the application page you just created in the Logto Console.

If you don't have a background script, you can follow the official guide to create one.

info:

Why do we need a background script?

Normal extension pages like the popup or options page can't run in the background, and they have the possibility to be closed during the authentication process. A background script ensures the authentication process can be properly handled.

Then, we need to listen to the message from other extension pages and handle the authentication process:

service-worker.js

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  // In the below code, since we return `true` for each action, we need to call `sendResponse`
  // to notify the sender. You can also handle errors here, or use other ways to notify the sender.

  if (message.action === 'signIn') {
    const redirectUri = chrome.identity.getRedirectURL('/callback');
    logtoClient.signIn(redirectUri).finally(sendResponse);
    return true;
  }

  if (message.action === 'signOut') {
    const redirectUri = chrome.identity.getRedirectURL();
    logtoClient.signOut(redirectUri).finally(sendResponse);
    return true;
  }

  return false;
});

You may notice there are two redirect URIs used in the code above. They are both created by chrome.identity.getRedirectURL, which is a built-in Chrome API to generate a redirect URL for auth flows. The two URIs will be:

• https://<extension-id>.chromiumapp.org/callback for sign-in.
• https://<extension-id>.chromiumapp.org/ for sign-out.

Note that these URIs are not accessible, and they are only used for Chrome to trigger specific actions for the authentication process.

Update Logto application settings

Now we need to update the Logto application settings to allow the redirect URIs we just created.

1. Go to the application page in the Logto Console.
2. In the "Redirect URIs" section, add the URI: https://<extension-id>.chromiumapp.org/callback.
3. In the "Post sign-out redirect URIs" section, add the URI: https://<extension-id>.chromiumapp.org/.
4. In the "CORS allowed origins" section, add the URI: chrome-extension://<extension-id>. The SDK in Chrome extension will use this origin to communicate with the Logto APIs.
5. Click on Save changes.

Remember to replace <extension-id> with your actual extension ID. You can find the extension ID in the chrome://extensions page.

Add sign-in and sign-out buttons to the popup

We're almost there! Let's add the sign-in and sign-out buttons and other necessary logic to the popup page.

In the popup.html file:

popup.html

<button id="sign-in">Sign in</button> <button id="sign-out">Sign out</button>

In the popup.js file (assuming popup.js is included in the popup.html):

popup.js

document.getElementById('sign-in').addEventListener('click', async () => {
  await chrome.runtime.sendMessage({ action: 'signIn' });
  // Sign-in completed (or failed), you can update the UI here.
});

document.getElementById('sign-out').addEventListener('click', async () => {
  await chrome.runtime.sendMessage({ action: 'signOut' });
  // Sign-out completed (or failed), you can update the UI here.
});

Checkpoint: Test the authentication flow

Now you can test the authentication flow in your Chrome extension:

1. Open the extension popup.
2. Click on the "Sign in" button.
3. You will be redirected to the Logto sign-in page.
4. Sign in with your Logto account.
5. You will be redirected back to the Chrome.

Check authentication state

Since Chrome provide unified storage APIs, rather than the sign-in and sign-out flow, all other Logto SDK methods can be used in the popup page directly.

In your popup.js, you can reuse the LogtoClient instance created in the background script, or create a new one with the same configuration:

popup.js

import LogtoClient from '@logto/chrome-extension';

const logtoClient = new LogtoClient({
  endpoint: '<your-logto-endpoint>'
  appId: '<your-logto-app-id>',
});

// Or reuse the logtoClient instance created in the background script
import { logtoClient } from './service-worker.js';

Then you can create a function to load the authentication state and user's profile:

popup.js

const loadAuthenticationState = async () => {
  const isAuthenticated = await logtoClient.isAuthenticated();
  // Update the UI based on the authentication state

  if (isAuthenticated) {
    const user = await logtoClient.getIdTokenClaims(); // { sub: '...', email: '...', ... }
    // Update the UI with the user's profile
  }
};

You can also combine the loadAuthenticationState function with the sign-in and sign-out logic:

popup.js

document.getElementById('sign-in').addEventListener('click', async () => {
  await chrome.runtime.sendMessage({ action: 'signIn' });
  await loadAuthenticationState();
});

document.getElementById('sign-out').addEventListener('click', async () => {
  await chrome.runtime.sendMessage({ action: 'signOut' });
  await loadAuthenticationState();
});

Here's an example of the popup page with the authentication state:

Other considerations

• Service worker bundling: If you use a bundler like Webpack or Rollup, you need to explicitly set the target to browser or similar to avoid unnecessary bundling of Node.js modules.
• Module resolution: Logto Chrome extension SDK is an ESM-only module.

See our sample project for a complete example with TypeScript, Rollup, and other configurations.

Add SMTP connector

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

To add a Email connector, simply follow these steps:

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

note:

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

Set up SMTP email connector

Set up SMTP connector

SMTP is a transmission protocol that is not exclusive to some specific email service providers but can work with all providers.

We are now offering guides on how to use the SMTP connector to send emails following providers for your better understanding:

• Gmail is the most popular email service vendor worldwide.
• Aliyun direct mail and SendGrid mail. Some of you might be familiar with these two email service providers because Logto Team provided corresponding connectors; you will likely have a general idea of them.

We hope you can figure out all other email vendors' setups with the following examples 🚀

Set up for Gmail use

You can get a new Gmail account at Gmail, or you can use an existing account if you have one.

A Gmail official post shows how to determine required properties' values to operate Gmail via an SMTP connector.

Integrate with SendGrid SMTP API

Initially, we assume that you already have a SendGrid account. If not, create a new account at the SendGrid website.

You can find a step-by-step guide on "Integrating with the SMTP API".

Developers can access sender details on the "Sender Management".

Configure with Aliyun direct mail account

Sign in to the Aliyun website. Register a new account if you don't have one.

Follow the Send emails using SMTP guide and finish those 'tasks' to get those required settings and information.

You can go to SMTP service address page to choose a proper SMTP service address host and port number.

To check "Sender Addresses", you can find the entrance on the left-side navigation pane on DirectMail console. You should see Sender address and SMTP Password here.

note:

Only one sample template is provided in the previous cases to keep things simple. You should add more templates for other use cases. You should change values wrapped with "<" and ">" according to your Gmail, SendGrid or Aliyun account settings and choose to keep other fields w/o "<" and ">". Add {{code}} as a placeholder in templates' content to show random verification code in sending emails.

Test SMTP connector

You can type in an email address 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
host	string
port	string
fromEmail	string
templates	Template[]

Template Properties	Type	Enum values
subject	string	N/A
content	string	N/A
usageType	enum string	'Register' | 'SignIn' | 'ForgotPassword' | 'Generic'
contentType	enum string	'text/plain' | 'text/html'

Username and password Auth Options

Name	Type	Enum values
user	string	N/A
pass	string	N/A
type	enum string (OPTIONAL)	'login'

You can also configure OAuth2 Auth Options and other advanced configurations. See here for more details.

We gave an example config with all configurable parameters in the text box to help you to set up own configuration. (You are responsible to the configuration, some values are for demonstration purpose and may not fit your use case.)

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 SMTP connector should be available now.

Enable SMTP connector in Sign-in Experience

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

1. Navigate to Console > Sign-in experience > Sign-up and sign-in.
2. Set up sign-up methods (Optional):
   1. Select "Email address" 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.
3. Set up sign-in methods:
   1. Select Email address 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.
4. 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 Email address to profile. See End-user flows for more details.

Testing and Validation

Return to your Chrome extension app. You should now be able to sign in with SMTP. Enjoy!

Further readings

End-user flows: Logto provides a out-of-the-box authentication flows including MFA and enterprise SSO, along with powerful APIs for flexible implementation of account settings, security verification, and multi-tenant experience.

Authorization: Authorization defines the actions a user can do or resources they can access after being authenticated. Explore how to protect your API for native and single-page applications and implement Role-based Access Control (RBAC).

Organizations: Particularly effective in multi-tenant SaaS and B2B apps, the organization feature enable tenant creation, member management, organization-level RBAC, and just-in-time-provisioning.

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