How to build a public Coinbase integration: Building the Auth Flow

Aug 7, 2024 • 7 minute read

Hey there, fellow JavaScript enthusiasts! Ready to dive into the world of Coinbase API integration? Today, we're going to focus on building a rock-solid authorization flow for your user-facing integration. Buckle up, because we're about to make your app Coinbase-friendly in no time!

Prerequisites

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

Coinbase API credentials (you're a pro, so I'm sure you've already got these)
A Node.js and Express.js setup (your bread and butter, right?)
A basic understanding of OAuth 2.0 (but don't worry, we'll refresh your memory)

Setting up the project

First things first, let's get our project ready:

npm init -y
npm install express axios dotenv

Now, create a .env file and add your Coinbase API credentials:

COINBASE_CLIENT_ID=your_client_id
COINBASE_CLIENT_SECRET=your_client_secret
COINBASE_REDIRECT_URI=http://localhost:3000/callback

Implementing the Authorization Flow

Alright, let's get to the meat of it! We'll create an Express app and set up our auth routes:

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

const authorizationUrl = `https://www.coinbase.com/oauth/authorize?response_type=code&client_id=${process.env.COINBASE_CLIENT_ID}&redirect_uri=${process.env.COINBASE_REDIRECT_URI}&scope=wallet:accounts:read`;

app.get('/auth', (req, res) => {
  res.redirect(authorizationUrl);
});

app.get('/callback', async (req, res) => {
  const { code } = req.query;
  try {
    const response = await axios.post('https://api.coinbase.com/oauth/token', {
      grant_type: 'authorization_code',
      code,
      client_id: process.env.COINBASE_CLIENT_ID,
      client_secret: process.env.COINBASE_CLIENT_SECRET,
      redirect_uri: process.env.COINBASE_REDIRECT_URI
    });
    const { access_token, refresh_token } = response.data;
    // Store these tokens securely (more on this later)
    res.send('Authorization successful!');
  } catch (error) {
    res.status(500).send('Authorization failed');
  }
});

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

Managing Access Tokens

Now that we've got our tokens, we need to keep them safe and sound. In a real-world scenario, you'd want to encrypt these and store them in a secure database. For now, let's keep it simple:

let tokens = {};

// After successful authorization
tokens = {
  access_token: response.data.access_token,
  refresh_token: response.data.refresh_token,
  expires_at: Date.now() + (response.data.expires_in * 1000)
};

// Function to refresh token when it expires
async function refreshAccessToken() {
  const response = await axios.post('https://api.coinbase.com/oauth/token', {
    grant_type: 'refresh_token',
    refresh_token: tokens.refresh_token,
    client_id: process.env.COINBASE_CLIENT_ID,
    client_secret: process.env.COINBASE_CLIENT_SECRET
  });
  tokens = {
    access_token: response.data.access_token,
    refresh_token: response.data.refresh_token,
    expires_at: Date.now() + (response.data.expires_in * 1000)
  };
}

Making Authenticated Requests

Time to put those tokens to work! Let's fetch the user's account info:

app.get('/account', async (req, res) => {
  if (Date.now() > tokens.expires_at) {
    await refreshAccessToken();
  }
  try {
    const response = await axios.get('https://api.coinbase.com/v2/accounts', {
      headers: { Authorization: `Bearer ${tokens.access_token}` }
    });
    res.json(response.data);
  } catch (error) {
    res.status(500).send('Failed to fetch account data');
  }
});

Error Handling and Edge Cases

Always be prepared for the unexpected! Here's a quick example of handling rate limits:

axios.interceptors.response.use(null, error => {
  if (error.response && error.response.status === 429) {
    // Handle rate limit, maybe implement exponential backoff
    console.log('Rate limited, retrying in 5 seconds');
    return new Promise(resolve => {
      setTimeout(() => resolve(axios(error.config)), 5000);
    });
  }
  return Promise.reject(error);
});

Security Considerations

Security is paramount! Consider implementing PKCE (Proof Key for Code Exchange) for added protection. Also, always use HTTPS in production and never expose your client secret.

Testing the Integration

Before you ship it, test it! Set up a mock Coinbase API for your test environment and simulate the entire auth flow. Trust me, your future self will thank you.

Wrapping Up

And there you have it! You've just built a solid foundation for your Coinbase integration. Remember, this is just the beginning. There's so much more you can do with the Coinbase API, from fetching transaction history to initiating trades.

Keep exploring, keep coding, and most importantly, keep securing those tokens! Happy integrating, folks!

Additional Resources

Now go forth and build something awesome! 🚀