Facebook OAuth2

Facebook login is optional and controlled by FACEBOOK_AUTH_ENABLED. When disabled, Facebook endpoints return 503 Service Unavailable. JWTs are never placed in the redirect URL; the API issues a one-time exchangeCode (Redis, 60 seconds). The same POST /auth/exchange endpoint is shared with Google.

• • Feature-flagged via environment
• • Passport Facebook strategy + FacebookAuthGuard
• • Redirect allowlist prevents open redirects
• • Same token response shape as POST /auth/login

Create a Facebook App with Facebook Login and set the Valid OAuth Redirect URI to match FACEBOOK_CALLBACK_URL.

1. Open Meta for Developers → My Apps → Create App
2. Add the Facebook Login product
3. Under Facebook Login → Settings, add Valid OAuth Redirect URI (e.g. http://localhost:3000/api/v1/auth/facebook/callback)
4. Copy App ID and App Secret into your .env
5. Request the email permission (required)

Loaded from .env via src/config/facebook-oauth.config.ts (namespace facebookOAuth on ConfigService). See .env.example.

FACEBOOK_AUTH_ENABLED=true
FACEBOOK_APP_ID=your-facebook-app-id
FACEBOOK_APP_SECRET=your-facebook-app-secret
FACEBOOK_CALLBACK_URL=http://localhost:3000/api/v1/auth/facebook/callback
FACEBOOK_REDIRECT_ALLOWLIST=myapp://success,http://localhost:5173/auth/callback
FACEBOOK_OAUTH_DEFAULT_ROLES=

New Facebook users receive roles: [] by default (same as password register). Set FACEBOOK_OAUTH_DEFAULT_ROLES in .env to a comma-separated list of Role values (e.g. user or user,manager). Existing users linked by email keep their current roles.

1. Client opens GET /api/v1/auth/facebook?redirect=<allowlisted URL>
2. User consents on Facebook; browser hits GET /api/v1/auth/facebook/callback
3. API upserts user, stores exchangeCode in Redis, redirects to redirect?code=...
4. Client POSTs { code } to /api/v1/auth/exchange and receives JWTs

Typical flow: button starts OAuth in the same window (or popup); a callback route on your frontend origin reads code from the query string and calls exchange.

const API = 'http://localhost:3000/api/v1';
const redirect = encodeURIComponent(
  'http://localhost:5173/auth/callback'
);

// Full-page redirect to Nest → Facebook → back to SPA
window.location.href = `${API}/auth/facebook?redirect=${redirect}`;

// /auth/callback on the SPA
const params = new URLSearchParams(window.location.search);
const code = params.get('code');
if (!code) throw new Error('Missing exchange code');

const res = await fetch('http://localhost:3000/api/v1/auth/exchange', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ code }),
});
if (!res.ok) throw new Error(await res.text());

const { user, accessToken, refreshToken } = await res.json();
// persist tokens as your app requires
sessionStorage.setItem('accessToken', accessToken);
console.log('signed in', user.email);

• • Add your frontend callback URL to FACEBOOK_REDIRECT_ALLOWLIST (e.g. http://localhost:5173/auth/callback)
• • FACEBOOK_CALLBACK_URL must point at the Nest API, not the SPA
• • Store accessToken / refreshToken securely (memory + httpOnly cookie patterns as you prefer)

Use a custom scheme (or universal link) in the allowlist. After Facebook, the API redirects to myapp://success?code=.... The app opens, parses the code, and calls exchange.

import * as Linking from 'expo-linking';
import * as WebBrowser from 'expo-web-browser';

const API = 'https://api.example.com/api/v1';
const redirect = encodeURIComponent('myapp://success');

async function signInWithFacebook() {
  const url = `${API}/auth/facebook?redirect=${redirect}`;
  await WebBrowser.openAuthSessionAsync(url, 'myapp://success');
}

import * as Linking from 'expo-linking';

async function exchangeFromUrl(url) {
  const { queryParams } = Linking.parse(url);
  const code = queryParams?.code;
  if (!code) return;

  const res = await fetch(`${API}/auth/exchange`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ code }),
  });
  const data = await res.json();
  // data.accessToken, data.refreshToken, data.user
  return data;
}

Linking.addEventListener('url', ({ url }) => {
  exchangeFromUrl(url);
});

• • Register the scheme in the OS / Expo app.json
• • Prefer Linking.addEventListener('url', ...) and getInitialURL()
• • Exchange over HTTPS against your API base URL

• • Redirect URLs must match FACEBOOK_REDIRECT_ALLOWLIST prefixes
• • Exchange codes are single-use and expire in 60 seconds (Redis)
• • Existing local users are linked by verified Facebook email (facebookId set; roles unchanged)
• • Facebook-only users have password null — password login / change-password will fail until a password is set
• • Email permission is required; login fails if Facebook does not return an email

Postgres entity / interface fields used by Facebook login:

• • facebookId — unique nullable Facebook subject ID
• • password — nullable for OAuth-only accounts
• • isActive — set true for new Facebook users
• • roles — from FACEBOOK_OAUTH_DEFAULT_ROLES env (default [])

• Social Authentication hub
• Google OAuth2 guide
• X / Twitter OAuth2 guide
• GitHub OAuth2 guide
• Figma OAuth2 guide
• LinkedIn OpenID Connect guide
• Slack OpenID Connect guide
• Atlassian OAuth 2.0 (3LO) guide
• GitLab OAuth2 guide
• Bitbucket OAuth2 guide
• Discord OAuth2 guide
• Twitch OAuth2 guide
• Steam OpenID 2.0 guide
• Reddit OAuth2 guide
• Auth & JWT