token-handler-js-assistant

A helper library to help SPAs interact with the OAuth Agent in the Token Handler pattern.

Add to project

Add to your project using npm

npm install @curity/token-handler-js-assistant

How to use in your project

Import the Assistant into your project and initialize it using Configuration object.

import {OAuthAgentClient} from "@curity/token-handler-js-assistant";
const client = new OAuthAgentClient({oauthAgentBaseUrl: 'https://api.example.com/oauthagent/example'})

The Configuration object contains the following options:

• oauthAgentBaseUrl - a URL with path to the token handler application created in the Curity Identity Server (this URL ends with a token handler application ID as defined in the Curity Identity Server configuration).

Using the initialized client

1. Starting the user login

   const response = await this.oauthAgentClient.startLogin({
     extraAuthorizationParameters: {
       scope: "openid profile", 
       login_hint: "username",
       ui_locales: "en"
     }
   })
   location.href = response.authorizationUrl

2. Finishing the user login

   const url = new URL(location.href)
   const response = await client.endLogin({ searchParams: url.searchParams })
   if (response.isLoggedIn) {
     // use id token claims to get username, e.g. response.idTokenClaims?.sub
   }

Note: The endLogin function should only be called with authorization response parameters (when the authorization server redirected user to the SPA after a successful user login). It's recommended to call onPageLoad() instead on every load of the SPA. This function makes a decision based the query string and either calls endLogin() or session().

3. Handling page load

   const sessionResponse = await client.onPageLoad(location.href)
   if (sessionResponse.isLoggedIn) {
     // user is logged in
   } else {
     const response = await client.startLogin()
     // redirect the user to the authorization server
     location.href = response.authorizationUrl
   }

4. Refreshing tokens

   await client.refresh()

5. Retrieving ID token claims

   const sessionResponse = await client.session()
   // use session data
   if (session.isLoggedIn === true) {
     session.idTokenClaims?.sub
   }

6. Logging out

   const logoutResponse = await client.logout()
   if (logoutResponse.logoutUrl) {
     // redirect user to the single logout url
     location.href = logoutResponse.logoutUrl;
   }

7. Implementing preemptive refresh. session(), refresh(), endLogin() and onPageLoad() functions return accessTokenExpiresIn if the Authorization Server includes expires_in in token responses. This field contains number of seconds until an
   access token that is in the proxy cookie expires. This value can be used to preemptively refresh the access token. After calling onPageLoad() and refresh():

   // const response = await client.onPageLoad(location.href)
   // const response = await client.refresh()
   if (response.accessTokenExpiresIn != null) {
     const delay = Math.max(response.accessTokenExpiresIn - 2, 1)
     setTimeout(
       () => { client.refresh(); },
       delay * 1000
     );
   }

   Note: This is just a simplified example. The timeout has to be cleared properly (before every refresh, or before logout).

Cookie Security

• SameSite=Strict cookies are sent to APIs, which cannot be sent from malicious sites
• to ensure that only precise whitelisted origins can send cookies to APIs, a token-handler-version: 1 header is sent by this library on every request to the OAuth Agent. In cross-origin deployments this ensures that a CORS pre-flight request authorizes access. SPA developers may be required to send this header to token handler proxies as well (refer to the token handler proxy documentation for details).