How to build Alipay (Web) sign-in with Capacitor JS

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 Alipay (Web) sign-in experience (user authentication) with Capacitor JS and Logto.

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of Capacitor JS.
A usable Alipay (Web) 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 Native app 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 "Native app" section or filter all the available "Native app" frameworks using the quick filter checkboxes on the left. Click the "Capacitor JS" 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 Capacitor JS with Logto

tip:

The following demonstration is built on Capacitor JS 5.0.6.

Installation

Install Logto SDK and peer dependencies via your favorite package manager:

npm
Yarn
pnpm

npm i @logto/capacitor
npm i @capacitor/browser @capacitor/app @capacitor/preferences

yarn add @logto/capacitor
yarn add @capacitor/browser @capacitor/app @capacitor/preferences

pnpm add @logto/capacitor
pnpm add @capacitor/browser @capacitor/app @capacitor/preferences

The @logto/capacitor package is the SDK for Logto. The remaining packages are its peer dependencies.

Init Logto client

Add the following code to your Capacitor project:

import LogtoClient, { type LogtoConfig } from '@logto/capacitor';

const logtoConfig: LogtoConfig = {
  endpoint: '<your-logto-endpoint>',
  appId: '<your-application-id>',
};

const logtoClient = new LogtoClient(config);

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.

Now, let's configure the redirect URI. The redirect URI is used to redirect the user back to your application after the authentication flow.

Ensure that the URI redirects to the Capacitor app, for example, com.example.app://callback. The value may vary depending on your Capacitor app configuration. For more details, see Capacitor Deep Links.

Then, add the following code to the onClick handler of the sign-in button:

const onClick = async () => {
  await logtoClient.signIn('com.example.app://callback');
  console.log(await logtoClient.isAuthenticated()); // true
  console.log(await logtoClient.getIdTokenClaims()); // { sub: '...', ... }
};

Implement sign-out

Since Capacitor leverages the Safari View Controller on iOS and Chrome Custom Tabs on Android, the authentication state can be persisted for a while. However, sometimes the user may want to sign out of the application immediately. In this case, we can use the signOut method to sign out the user:

const onClick = async () => {
  await logtoClient.signOut();
  console.log(await logtoClient.isAuthenticated()); // false
};

The signOut method has an optional parameter for the post sign-out redirect URI. If it's not provided, the user will be redirected to the Logto sign-out page.

The user needs to click "Done" to close the web view and return to the Capacitor app. If you want to automatically redirect the user back to the Capacitor app, you can provide the post sign-out redirect URI, for instance, com.example.app://callback/sign-out.

Ensure that the post sign-out redirect URI can redirect to the Capacitor app. Then add the following code to the onClick handler of the sign-out button:

const onClick = async () => {
  await logtoClient.signOut('com.example.app://callback/sign-out');
};

Checkpoint: Trigger the authentication flow

Run the Capacitor app and click the sign-in button. A browser window will open, redirecting to the Logto sign-in page.

If the user closes the browser window without completing the authentication flow, the Capacitor app will receive a LogtoClientError.

Add Alipay (Web) connector

To enable quick sign-in and improve user conversion, connect with Capacitor JS as an identity provider. The Logto social connector helps you establish this connection in minutes by allowing several parameter inputs.

To add a social connector, simply follow these steps:

Navigate to Console > Connectors > Social Connectors.
Click "Add social connector" and select "Alipay (Web)".
Follow the README guide and complete required fields and customize settings.

note:

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

Set up Alipay web app

Register Alipay developer account

Create and configure Alipay app

Sign in to the Alipay console with the account you have just registered.
Go to "Web & Mobile Apps" (网页&移动应用) tab in "My Application" (我的应用) panel.
Click "Create an App" (立即创建) button to start configuring your application.
Name your application in "Application Name" (应用名称) following the naming conventions and upload your "Application Icon" (应用图标), make sure you choose "web application" (网页应用) as "App type" (应用类型).
After finishing creating the application, we come to the Overview page, where we should click "add ability" (添加能力) to add "Third-party application authorization" (第三方应用授权), "Get member information" (获取会员信息) and "App Alipay login" (App 支付宝登录) before enabling Alipay sign-in.
Go to Alipay Customer Center, and sign in with the Alipay developer account. Click "Account Center" (账号中心) on the topbar and go to "APPID binding" (APPID 绑定), whose entrance can be found at the bottom of the sidebar. "Add binding" (添加绑定) by type in the APPID of the web application you just created in step 4.
Click on "Sign" button of "App Alipay login", and finish signing process following the guide. After finishing this step, you are expected to find abilities you have just added in step 5 kicks in.
Come back to Alipay open platform console page, and you can find "Interface signing method" (接口加签方式（密钥/证书）) in "development information" (开发信息) section. Click "set up" (设置) button, and you can find yourself on a page setting signing method. "Public Key" (公钥) is the preferred signing mode, and fill in contents from the public key file you have generated in the text input box.
Set up "Authorization Redirect URI" (授权回调地址) by clicking "set up" (设置) button on the bottom of the Alipay console page. ${your_logto_origin}/callback/${connector_id} is the default redirect URI used in Logto core. The connector_id can be found on the top bar of the Logto Admin Console connector details page.
After finishing all these steps, go back to the top right corner of Alipay console page, and click "Submit for review" (提交审核). Once the review is approved, you are good to go with a smooth Alipay sign-in flow.

note:

You can use openssl to generate key pairs on your local machine by executing following code snippet in terminal.

openssl genrsa -out private.pem 2048
openssl rsa -in private.pem -outform PEM -pubout -out public.pem

When filling in the public key on the Alipay app setup website, you need to remove the header and footer of public.pem, delete all newline characters, and paste the rest of the contents into the text input box for "public key".

Set up the Logto Alipay Web connector settings

In the Alipay console workspace go to "My application" (我的应用) panel and click "Web & Mobile Apps" (网页&移动应用) tab, you can find APPID of all applications.
In step 7 of the previous part, you have already generated a key pair including a private key and a public key.
Fill out the Logto connector settings:
- Fill out the appId field with APPID you've got from step 1.
- Fill out the privateKey field with contents from the private key file mentioned in step 2. Please MAKE SURE to use '\n' to replace all newline characters and do not remove header and footer in private key file.
- Fill out the signType field with 'RSA2' due to the Public key signing mode we chose in step 7 of "Create And Configure Alipay Apps".
- Fill out the charset field with either 'gbk' or 'utf8'. You can leave this field blank as it is OPTIONAL. The default value is set to be 'utf8'.
- Fill out the scope field with either 'auth_base' or 'auth_user'. You can leave this field blank as it is OPTIONAL. The default value is set to be 'auth_user'. You can check out the difference between different values.

Config types

Name	Type	Enum values
appId	string	N/A
privateKey	string	N/A
signType	enum string	'RSA' \| 'RSA2'
charset	enum string (OPTIONAL)	'gbk' \| 'utf8' \| undefined
scope	enum string (OPTIONAL)	'auth_user' \| 'auth_base'

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 Alipay (Web) connector should be available now.

Once you create a social connector successfully, you can enable it as a "Continue with Alipay (Web)" button in Sign-in Experience.

Navigate to Console > Sign-in experience > Sign-up and sign-in.
(Optional) Choose "Not applicable" for sign-up identifier if you need social login only.
Add configured Alipay (Web) connector to the "Social sign-in" section.

Testing and Validation

Return to your Capacitor JS app. You should now be able to sign in with Alipay (Web). Enjoy!

Create an application in Logto​

Integrate Capacitor JS with Logto​

Installation​

Init Logto client​

Implement sign-in​

Regarding redirect-based sign-in​

Implement sign-out​

Checkpoint: Trigger the authentication flow​

Add Alipay (Web) connector​

Set up Alipay web app​

Register Alipay developer account​

Create and configure Alipay app​

Set up the Logto Alipay Web connector settings​

Config types​

Save your configuration​

Enable Alipay (Web) connector in Sign-in Experience​

Testing and Validation​

Further readings​