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

Aug 9, 2024 • 7 minute read

Introduction

Hey there, fellow JavaScript aficionado! Ready to dive into the world of PowerBI integration? Buckle up, because we're about to embark on an exciting journey to build a robust auth flow for your user-facing PowerBI integration. Trust me, nailing this part is crucial, and I'm here to guide you through it with ease.

Prerequisites

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

A PowerBI account with an app registered (I know, I know, the boring stuff)
Node.js installed (you're a JS dev, so I'm sure you're covered)
Your favorite package manager ready to grab some libraries (express, axios - you know the drill)

Auth Flow Overview

We're dealing with OAuth 2.0 authorization code flow here. Don't let the fancy name intimidate you - it's just a dance between authorization endpoints, token endpoints, and those nifty refresh tokens. We'll waltz through this together!

Implementing the Auth Flow

Setting up the server

Let's kick things off with some Express.js magic:

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

const CLIENT_ID = process.env.CLIENT_ID;
const CLIENT_SECRET = process.env.CLIENT_SECRET;
const REDIRECT_URI = process.env.REDIRECT_URI;

// More awesomeness to come...

Initiating the auth flow

Time to construct that authorization URL and send your users on a mini-adventure:

app.get('/login', (req, res) => {
  const authUrl = `https://login.microsoftonline.com/common/oauth2/v2.0/authorize?
    client_id=${CLIENT_ID}&
    response_type=code&
    redirect_uri=${REDIRECT_URI}&
    response_mode=query&
    scope=https://analysis.windows.net/powerbi/api/.default`;
  
  res.redirect(authUrl);
});

Handling the callback

Your users are back! Let's grab that code and exchange it for some shiny tokens:

app.get('/callback', async (req, res) => {
  const { code } = req.query;
  
  try {
    const tokenResponse = await axios.post('https://login.microsoftonline.com/common/oauth2/v2.0/token', 
      new URLSearchParams({
        client_id: CLIENT_ID,
        client_secret: CLIENT_SECRET,
        code,
        redirect_uri: REDIRECT_URI,
        grant_type: 'authorization_code'
      })
    );

    const { access_token, refresh_token } = tokenResponse.data;
    // Store these securely - we'll get to that!
    
    res.send('Authentication successful!');
  } catch (error) {
    console.error('Error during token exchange:', error);
    res.status(500).send('Authentication failed');
  }
});

Token management

Now, let's talk about keeping those tokens safe and fresh:

// This is just a simple example - consider using a proper database in production!
const tokens = {};

function storeTokens(userId, accessToken, refreshToken) {
  tokens[userId] = { accessToken, refreshToken };
}

async function refreshAccessToken(userId) {
  const { refreshToken } = tokens[userId];
  
  try {
    const response = await axios.post('https://login.microsoftonline.com/common/oauth2/v2.0/token',
      new URLSearchParams({
        client_id: CLIENT_ID,
        client_secret: CLIENT_SECRET,
        refresh_token: refreshToken,
        grant_type: 'refresh_token'
      })
    );

    const { access_token, refresh_token } = response.data;
    storeTokens(userId, access_token, refresh_token);
    
    return access_token;
  } catch (error) {
    console.error('Error refreshing token:', error);
    throw error;
  }
}

Making authenticated requests

Let's put those tokens to work:

async function makeAuthenticatedRequest(userId, endpoint) {
  let { accessToken } = tokens[userId];
  
  try {
    const response = await axios.get(`https://api.powerbi.com/v1.0/myorg/${endpoint}`, {
      headers: { Authorization: `Bearer ${accessToken}` }
    });
    return response.data;
  } catch (error) {
    if (error.response && error.response.status === 401) {
      // Token expired, let's refresh it
      accessToken = await refreshAccessToken(userId);
      return makeAuthenticatedRequest(userId, endpoint);
    }
    throw error;
  }
}

Error Handling and Security Considerations

Always validate those tokens, my friend! And don't forget to protect against CSRF attacks. Here's a quick tip:

const csrf = require('csurf');
const csrfProtection = csrf({ cookie: true });

app.use(csrfProtection);

app.get('/login', csrfProtection, (req, res) => {
  // Include the CSRF token in your auth URL
  const authUrl = `...&state=${req.csrfToken()}`;
  res.redirect(authUrl);
});

app.get('/callback', csrfProtection, (req, res) => {
  if (req.query.state !== req.csrfToken()) {
    return res.status(403).send('Invalid CSRF token');
  }
  // Proceed with token exchange
});

Testing the Auth Flow

Give it a whirl! Try logging in, accessing some data, and see how it handles token refreshes. For the overachievers out there, consider setting up some automated tests with Jest or Mocha.

Conclusion

And there you have it! You've just built a rock-solid auth flow for your PowerBI integration. Pat yourself on the back - you've earned it! Remember, this is just the beginning. Keep exploring, keep building, and most importantly, keep being awesome!

Additional Resources

Now go forth and create some PowerBI magic! You've got this! 🚀✨