How to Build a Public bexio Integration: Building the Auth Flow

Aug 18, 2024 • 7 minute read

Hey there, fellow JavaScript developer! Ready to dive into the world of bexio integrations? Today, we're going to tackle one of the most crucial parts of any API integration: the authorization flow. Buckle up, because we're about to make your bexio integration dreams come true!

Introduction

If you're reading this, you're probably already familiar with bexio, the Swiss-made business software that's taking the world by storm. But here's the thing: no matter how awesome your integration idea is, it's not going anywhere without proper authentication. That's why we're focusing on building a rock-solid auth flow for your user-facing integration.

Prerequisites

Before we jump in, make sure you've got:

Your bexio API credentials (if you don't have them yet, hop over to the bexio developer portal and get 'em!)
Your favorite JavaScript development environment set up and ready to go

Got all that? Great! Let's get this show on the road.

Understanding OAuth 2.0 in bexio

bexio uses OAuth 2.0 for authentication, which is like the cool kid of auth protocols. It's secure, flexible, and widely adopted. In a nutshell, here's how it works:

Your app asks for permission
The user grants it
You get an access token
You use that token to make API requests

bexio has specific OAuth endpoints that we'll be using, so keep the API docs handy!

Implementing the Authorization Flow

Initiating the Authorization Request

First things first, we need to construct the authorization URL. It'll look something like this:

const authUrl = `https://idp.bexio.com/authorize?client_id=${YOUR_CLIENT_ID}&redirect_uri=${REDIRECT_URI}&state=${STATE}&response_type=code`;

Pro tip: Always use a state parameter. It's like a secret handshake between your requests and helps prevent nasty CSRF attacks.

Handling the Authorization Callback

Once the user approves your request, bexio will redirect them back to your specified redirect URI. Set up an endpoint to catch this callback and extract the authorization code:

app.get('/callback', (req, res) => {
  const { code, state } = req.query;
  // Verify state and handle the code
});

Exchanging the Code for Access Token

Now for the good stuff! Let's exchange that code for an access token:

const response = await fetch('https://idp.bexio.com/token', {
  method: 'POST',
  headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
  body: new URLSearchParams({
    grant_type: 'authorization_code',
    code,
    redirect_uri: REDIRECT_URI,
    client_id: CLIENT_ID,
    client_secret: CLIENT_SECRET,
  }),
});

const { access_token, refresh_token } = await response.json();

Remember to store these tokens securely. Your server's memory or a secure database are good options.

Refreshing the Access Token

Access tokens don't last forever, so let's implement a refresh mechanism:

const refreshToken = async (refresh_token) => {
  // Similar to the code exchange, but use grant_type: 'refresh_token'
};

Error Handling and Edge Cases

OAuth isn't always smooth sailing. Be prepared to handle errors like:

Invalid or expired tokens
User cancellation
Network timeouts

Always provide clear feedback to your users and graceful fallbacks in your code.

Security Considerations

Security isn't just a feature, it's a necessity. Here are some non-negotiables:

Always use HTTPS
Store tokens securely (not in local storage!)
Implement proper CSRF protection

Testing the Auth Flow

Before you pop the champagne, make sure to thoroughly test your auth flow. Try some manual tests:

Go through the full authorization process
Test with invalid credentials
Check token refresh functionality

For the overachievers, set up some automated tests to keep your auth flow in check as you develop.

Conclusion

And there you have it! You've just built a robust authorization flow for your bexio integration. Pat yourself on the back – you're well on your way to creating something awesome.

Next up, you'll want to start making those API calls and building out the rest of your integration. But that's a story for another day!

Additional Resources

Want to dive deeper? Check out these resources:

Now go forth and integrate! Your users (and your future self) will thank you for building such a solid foundation. Happy coding!