GitLab OAuth2

GitLab login is optional and controlled by GITLAB_AUTH_ENABLED. When disabled, GitLab 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 other social providers.

• • Feature-flagged via environment
• • Custom passport-oauth2 strategy + GitlabAuthGuard
• • Profile fetched via GET https://gitlab.com/api/v4/user after token exchange
• • Scope read_user for basic profile and email
• • Redirect allowlist prevents open redirects
• • Same token response shape as POST /auth/login

Register a user-owned OAuth application in your GitLab profile. The Redirect URI must match GITLAB_CALLBACK_URL exactly. Enable the read_user scope so the API can load the signed-in profile and email.

1. Click your avatar (top-right) → Edit profile
2. In the left sidebar, open Access → Applications
3. Choose Add new application
4. Give it a Name and set the Redirect URI to your API callback (e.g. http://localhost:3000/api/v1/auth/gitlab/callback)
5. Under OAuth 2 scopes, enable read_user
6. Save the application, then copy Application ID and Secret into GITLAB_CLIENT_ID / GITLAB_CLIENT_SECRET
7. Keep GITLAB_CALLBACK_URL identical to the Redirect URI you registered (use Renew secret in GitLab if you need to rotate the secret later)

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

GITLAB_AUTH_ENABLED=true
GITLAB_CLIENT_ID=your-gitlab-application-id
GITLAB_CLIENT_SECRET=your-gitlab-secret
GITLAB_CALLBACK_URL=http://localhost:3000/api/v1/auth/gitlab/callback
GITLAB_REDIRECT_ALLOWLIST=myapp://success,http://localhost:5173/auth/callback
GITLAB_OAUTH_DEFAULT_ROLES=

New GitLab users receive roles: [] by default (same as password register). Set GITLAB_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/gitlab?redirect=<allowlisted URL>
2. User consents on GitLab; browser hits GET /api/v1/auth/gitlab/callback
3. API calls GET https://gitlab.com/api/v4/user, 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 → GitLab → back to SPA
window.location.href = `${API}/auth/gitlab?redirect=${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 GITLAB_REDIRECT_ALLOWLIST (e.g. http://localhost:5173/auth/callback)
• • GITLAB_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 GitLab, 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 signInWithGitLab() {
  const url = `${API}/auth/gitlab?redirect=${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 GITLAB_REDIRECT_ALLOWLIST prefixes
• • Exchange codes are single-use and expire in 60 seconds (Redis)
• • Existing local users are linked by verified GitLab email (gitlabId set; roles unchanged)
• • GitLab-only users have password null — password login / change-password will fail until a password is set
• • Email is required from gitlab.com/api/v4/user; login fails if GitLab does not return an email (scope read_user)

Postgres entity / interface fields used by GitLab login:

• • gitlabId — unique nullable GitLab user id (id from /api/v4/user)
• • password — nullable for OAuth-only accounts
• • isActive — set true for new GitLab users
• • roles — from GITLAB_OAUTH_DEFAULT_ROLES env (default [])

• Social Authentication hub
• Google OAuth2 guide
• Facebook 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
• Bitbucket OAuth2 guide
• Discord OAuth2 guide
• Twitch OAuth2 guide
• Steam OpenID 2.0 guide
• Reddit OAuth2 guide
• Auth & JWT