Introduction to koa-passport

koa-passport is a Koa-specific middleware for authentication using Passport.js. It provides a painless and clean way to implement authentication in Koa-based applications.

Getting Started

First, let’s install koa-passport and its dependencies:

  npm install koa-passport passport

Setting up Koa and Koa-passport

After installing the dependencies, we need to set up Koa and integrate koa-passport with it:

  const Koa = require('koa');
  const session = require('koa-session');
  const koaPassport = require('koa-passport');
  const app = new Koa();

  app.keys = ['your-session-secret'];
  app.use(session({}, app));
  app.use(koaPassport.initialize());
  app.use(koaPassport.session());

Passport Strategies

Passport.js has a wide range of strategies for different authentication mechanisms. Here is an example of configuring a local authentication strategy:

  const LocalStrategy = require('passport-local').Strategy;

  koaPassport.use(new LocalStrategy((username, password, done) => {
    // Your verification logic
    const user = { id: 1, username: 'test' }; // Example user
    if (username === 'test' && password === 'password') {
      return done(null, user);
    } else {
      return done(null, false);
    }
  }));

Serialization and Deserialization

Passport requires serialization and deserialization of users for session management:

  koaPassport.serializeUser((user, done) => {
    done(null, user.id); 
  });

  koaPassport.deserializeUser((id, done) => {
    const user = { id: 1, username: 'test' }; // Example user matching id
    done(null, user);
  });

Authentication Middleware

We then create authentication routes using the authenticate method:

  const Router = require('koa-router');
  const router = new Router();

  router.post('/login', koaPassport.authenticate('local', {
    successRedirect: '/',
    failureRedirect: '/login'
  }));

You can also protect routes using koa-passport:

  router.get('/profile', (ctx, next) => {
    if (ctx.isAuthenticated()) {
      ctx.body = 'Profile page';
    } else {
      ctx.redirect('/login');
    }
  });

Complete Example App

Below is a complete example integrating all the above pieces:

  const Koa = require('koa');
  const session = require('koa-session');
  const koaPassport = require('koa-passport');
  const LocalStrategy = require('passport-local').Strategy;
  const Router = require('koa-router');

  const app = new Koa();
  app.keys = ['your-session-secret'];
  app.use(session({}, app));
  app.use(koaPassport.initialize());
  app.use(koaPassport.session());

  koaPassport.serializeUser((user, done) => {
    done(null, user.id); 
  });

  koaPassport.deserializeUser((id, done) => {
    const user = { id: 1, username: 'test' }; 
    done(null, user);
  });

  koaPassport.use(new LocalStrategy((username, password, done) => {
    const user = { id: 1, username: 'test' };
    if (username === 'test' && password === 'password') {
      return done(null, user);
    } else {
      return done(null, false);
    }
  }));

  const router = new Router();

  router.post('/login', koaPassport.authenticate('local', {
    successRedirect: '/',
    failureRedirect: '/login'
  }));

  router.get('/profile', (ctx, next) => {
    if (ctx.isAuthenticated()) {
      ctx.body = 'Profile page';
    } else {
      ctx.redirect('/login');
    }
  });

  app.use(router.routes()).use(router.allowedMethods());

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

With this setup, you can easily build a Koa application with authentication using koa-passport.

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