shelf_session

The shelf_session is the implementation of cookiesMiddleware and sessionMiddleware for shelf.

Version: 0.1.0

About

Adds two middleware for shelf:

• cookiesMiddleware
• sessionMiddleware

The cookiesMiddleware can be used independently.
The sessionMiddleware depends on cookiesMiddleware and must be used after it.

final pipeline = const Pipeline()
    .addMiddleware(cookiesMiddleware())
    .addMiddleware(sessionMiddleware())
    .addHandler(handler);

A small workable example:

import 'dart:io' show Cookie;

import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf_router/shelf_router.dart';
import 'package:shelf_session/cookies_middleware.dart';
import 'package:shelf_session/session_middleware.dart';
import 'package:shelf_static/shelf_static.dart';

void main(List<String> args) async {
  final router = Router();
  router.get('/', _handleHome);
  router.get('/login', _handleLogin);
  router.get('/login/', _handleLogin);
  router.post('/login', _handleLogin);
  router.post('/login/', _handleLogin);
  router.get('/logout', _handleLogout);
  router.get('/logout/', _handleLogout);
  final staticHandler =
      createStaticHandler('web', defaultDocument: 'index.html');
  final handler = Cascade().add(staticHandler).add(router).handler;
  final pipeline = const Pipeline()
      .addMiddleware(logRequests())
      .addMiddleware(cookiesMiddleware())
      .addMiddleware(sessionMiddleware())
      .addHandler(handler);
  const address = 'localhost';
  const port = 8080;
  final server = await io.serve(pipeline, address, port);
  print('Serving at http://${server.address.host}:${server.port}');
}

const _menu = '''
<a href="/">Home</a><br />
<a href="/login">Log in</a><br />
<a href="/logout">Log out</a><br />''';

Future<Response> _handleHome(Request request) async {
  final userManager = UserManager();
  final user = userManager.getUser(request);
  var body = '$_menu{{message}}<br />{{cookies}}';
  if (user == null) {
    body = body.replaceAll('{{message}}', 'You are not logged in');
  } else {
    body = body.replaceAll('{{message}}', 'You are logged in as ${user.name}');
  }

  final cookies = request.getCookies();
  body = body.replaceAll('{{cookies}}',
      cookies.entries.map((e) => '${e.key}: ${e.value}').join('<br />'));
  request.addCookie(Cookie('foo', 'Foo'));
  if (!cookies.containsKey('baz')) {
    request.addCookie(Cookie('baz', 'Baz'));
  } else {
    request.removeCookie(Cookie('baz', ''));
  }

  return _render(body);
}

Future<Response> _handleLogin(Request request) async {
  const html = '''
<form action="" method="post">
<label>Login</label><br />
<input name="login" type="text" /><br />
<label>Password</label><br />
<input name="password" type="password" /><br /><br />
<button>Log in</button>
</form>
''';

  if (request.method == 'GET') {
    return _render(_menu + html);
  }

  final body = await request.readAsString();
  final queryParameters = Uri(query: body).queryParameters;
  final login = queryParameters['login'] ?? ''
    ..trim();
  final password = queryParameters['password'] ?? ''
    ..trim();
  if (login.isEmpty || password.isEmpty) {
    return _render(_menu + html);
  }

  final user = User(login);
  final userManager = UserManager();
  userManager.setUser(request, user);
  return Response.found('/');
}

Future<Response> _handleLogout(Request request) async {
  Session.deleteSession(request);
  return Response.found('/');
}

Response _render(String body) {
  return Response.ok(body, headers: {
    'Content-type': 'text/html; charset=UTF-8',
  });
}

class User {
  final String name;

  User(this.name);
}

class UserManager {
  User? getUser(Request request) {
    final session = Session.getSession(request);
    if (session == null) {
      return null;
    }

    final user = session.data['user'];
    if (user is User) {
      return user;
    }

    return null;
  }

  User setUser(Request request, User user) {
    var session = Session.getSession(request);
    session ??= Session.createSession(request);
    session.data['user'] = user;
    return user;
  }
}

Session data is stored in a hash map at runtime.
This implementation implies that session data should only be created for authorized users.
This approach eliminates memory overflow in the case of various types of attacks.
After the expiration of the lifetime, the session data is deleted automatically (which causes the memory to be freed).
Timers are not used for these purposes. This happens during the creation of new sessions.