Express

Follow these simple steps to set up Civic Auth with an Express backend (a working example is available in our github examples repo).

1. Install dependencies

npm install @civic/auth cookies-parser

2. Configure your App

Your app will need the following configuration:

const config = {
  clientId: // Client ID from auth.civic.com
  redirectUrl: 'http://localhost:3000/auth/callback' // change to your domain when deploying,
  postLogoutRedirectUrl: 'http://localhost:3000/' // The postLogoutRedirectUrl is the URL where the user will be redirected after successfully logging out from Civic's auth server.
};

Note: redirectUrl and postLogoutRedirectUrl must be absolute URLs.

3. Set up Cookies

Civic Auth uses cookies for storing the login state by default

import express, { Request, Response } from 'express';
import { CookieStorage } from '@civic/auth/server';
import cookieParser from 'cookie-parser';

app.use(cookieParser());

// Tell Civic how to get cookies from your node server
class ExpressCookieStorage extends CookieStorage {
  constructor(private req: Request, private res: Response) {
    super({
      secure: false
    })
  }

  async get(key: string): Promise<string | null> {
    return Promise.resolve(this.req.cookies[key] ?? null);
  }

  async set(key: string, value: string): Promise<void> {
    await this.res.cookie(key, value, this.settings);
  }
}

app.use((req, res, next) => {
  // add an instance of the cookie storage to each request
  req.storage = new ExpressCookieStorage(req, res);
  next();
});

4. Create a Login Endpoint

This endpoint will handle login requests, build the Civic login URL and redirect the user to it.

import { buildLoginUrl } from '@civic/auth/server';

app.get('/', async (req: Request, res: Response) => {
  const url = await buildLoginUrl(config, req.storage);

  res.redirect(url.toString());
});

5. Create a Logout Endpoint

This endpoint will handle logout requests, build the Civic logout URL and redirect the user to it.

import { buildLogoutRedirectUrl } from '@civic/auth/server';

app.get('/auth/logout', async (req: Request, res: Response) => {
  const url = await buildLogoutRedirectUrl(config, req.storage);
  res.redirect(url.toString());
});

6. Create the Callback Endpoint

This endpoint handles successful logins and creates the session

import { resolveOAuthAccessCode } from '@civic/auth/server';

app.get('/auth/callback', async (req: Request, res: Response) => {
  const { code, state } = req.query as { code: string; state: string };

  await resolveOAuthAccessCode(code, state, req.storage, config);
  res.redirect('/admin/hello');
});

7. Add Middleware

Middleware protects routes that require login.

import { isLoggedIn } from '@civic/auth/server';

const authMiddleware = async (req: Request, res: Response, next: NextFunction) => {
  if (!(await isLoggedIn(req.storage))) return res.status(401).send('Unauthorized');
  next();
};

// Apply authentication middleware to any routes that need it
app.use('/admin', authMiddleware);

8. Use the Session

If needed, get the logged-in user information.

import { user } from '@civic/auth/server';

app.get('/admin/hello', async (req: Request, res: Response) => {
  const user = await getUser(req.storage);
  res.send(`Hello, ${user?.name}!`);
});

PKCE and Client Secrets

Civic Auth uses PKCE (Proof Key for Code Exchange), to protect users and clients from unauthorized access to user information. This, alongside domain registration for apps in production environments, mean that you don't need to provide a client secret in your backend.

When using the Civic Auth SDK, PKCE is handled entirely by the library.

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