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

Aug 1, 2024 • 7 minute read

Hey there, fellow JavaScript enthusiast! Ready to dive into the world of DocuSign integration? Today, we're focusing on the crucial part of any integration: the authorization flow. Let's get your app talking to DocuSign securely and smoothly.

Introduction

DocuSign integration can be a game-changer for your app, allowing users to sign documents digitally with ease. The key to making this work? A rock-solid authorization flow. It's the gatekeeper that ensures only the right people get access to the right stuff. Let's build it!

Prerequisites

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

A DocuSign Developer account (if you don't have one, go grab it!)
An application registered in DocuSign (this is where you'll get your client ID and secret)
Node.js and npm installed on your machine

Got all that? Great! Let's roll.

Setting Up the Project

First things first, let's get our project set up:

mkdir docusign-integration
cd docusign-integration
npm init -y
npm install express axios dotenv

Configuring Environment Variables

Security first! Create a .env file in your project root:

DOCUSIGN_CLIENT_ID=your_client_id
DOCUSIGN_CLIENT_SECRET=your_client_secret
DOCUSIGN_AUTH_SERVER=account-d.docusign.com
REDIRECT_URI=http://localhost:3000/callback

Replace those placeholders with your actual DocuSign credentials. Keep this file safe and out of version control!

Implementing the Authorization Flow

Creating the Authorization URL

Let's start by setting up a route to kick off the auth process:

const express = require('express');
const app = express();
require('dotenv').config();

app.get('/auth', (req, res) => {
  const authUrl = `https://${process.env.DOCUSIGN_AUTH_SERVER}/oauth/auth?response_type=code&scope=signature&client_id=${process.env.DOCUSIGN_CLIENT_ID}&redirect_uri=${process.env.REDIRECT_URI}`;
  res.redirect(authUrl);
});

app.listen(3000, () => console.log('Server running on port 3000'));

When a user hits this route, they'll be whisked away to DocuSign's login page.

Handling the Callback

After the user logs in, DocuSign will redirect them back to your app with an authorization code. Let's catch that:

app.get('/callback', async (req, res) => {
  const { code } = req.query;
  // We'll use this code in the next step
  // For now, let's just acknowledge it
  res.send('Authorization successful! Check the console.');
  console.log('Authorization Code:', code);
});

Exchanging Code for Access Token

Now for the good stuff. Let's trade that code for an access token:

const axios = require('axios');

async function getAccessToken(code) {
  try {
    const response = await axios.post(`https://${process.env.DOCUSIGN_AUTH_SERVER}/oauth/token`, {
      grant_type: 'authorization_code',
      code,
      client_id: process.env.DOCUSIGN_CLIENT_ID,
      client_secret: process.env.DOCUSIGN_CLIENT_SECRET
    });
    return response.data;
  } catch (error) {
    console.error('Error getting access token:', error.response.data);
    throw error;
  }
}

// Update your callback route
app.get('/callback', async (req, res) => {
  const { code } = req.query;
  try {
    const tokenData = await getAccessToken(code);
    // Store this token securely!
    console.log('Access Token:', tokenData.access_token);
    res.send('Authorization successful!');
  } catch (error) {
    res.status(500).send('Error during authorization');
  }
});

Refreshing the Access Token

Access tokens don't last forever. Let's add a function to refresh them:

async function refreshAccessToken(refresh_token) {
  try {
    const response = await axios.post(`https://${process.env.DOCUSIGN_AUTH_SERVER}/oauth/token`, {
      grant_type: 'refresh_token',
      refresh_token,
      client_id: process.env.DOCUSIGN_CLIENT_ID,
      client_secret: process.env.DOCUSIGN_CLIENT_SECRET
    });
    return response.data;
  } catch (error) {
    console.error('Error refreshing token:', error.response.data);
    throw error;
  }
}

Error Handling and Security Considerations

Always handle errors gracefully and never expose sensitive information. Use HTTPS in production and consider using a secure session store for tokens.

Testing the Authorization Flow

Fire up your server and navigate to http://localhost:3000/auth. You should be redirected to DocuSign, and after logging in, you'll be sent back to your app with an access token. Magic!

Conclusion

And there you have it! You've just built a solid authorization flow for your DocuSign integration. With this foundation, you're ready to start making API calls and integrating DocuSign's awesome features into your app.

Additional Resources

Remember, the world of API integration is vast and exciting. Keep exploring, keep building, and most importantly, keep having fun with it! Happy coding!