Insecure functionality - Session management - Dart

Need

Secure session management

Context

1. Usage of Dart 2.0 for building scalable and efficient web applications
2. Usage of Shelf for managing and organizing data in a Node.js application

Description

Insecure Code Example

import 'package:shelf/shelf.dart' as shelf;

class Session {
  String id;
  DateTime expirationTime;

  Session(this.id, this.expirationTime);
}

final sessionMap = <String, Session>{};

shelf.Response handleRequest(shelf.Request request) {
  final sessionId = request.headers['sessionId'];
  final session = sessionMap[sessionId];
  
  if (session != null && DateTime.now().isBefore(session.expirationTime)) {
    // Handle authenticated request
    return shelf.Response.ok('Authenticated request');
  } else {
    // Handle unauthenticated request
    return shelf.Response.forbidden('Unauthenticated request');
  }
}

void main() {
  var handler = const shelf.Pipeline().addMiddleware(shelf.logRequests()).addHandler(handleRequest);
  shelf.serve(handler, 'localhost', 8080);
}

The above code is a simple Dart server using the Shelf framework. It uses a basic session management mechanism where sessions are stored in a map and retrieved using a session ID from the request headers. The vulnerability lies in the session validation within the `handleRequest` function. The function checks if the session exists and if it hasn't expired yet. If both conditions are met, it handles the request as an authenticated request. However, the `expirationTime` of a session is stored in the session object itself, which is stored in a map on the server. This means that if an attacker can somehow gain access to the server's memory or the session map, they can modify the `expirationTime` of an expired session to a future time, thus making the session valid again. This is an insecure session management vulnerability because it allows an attacker to prolong a session indefinitely by simply modifying the session's expiration time.

Steps

1. Ensure that the session expiration time is managed server-side and cannot be modified by the client.
2. Implement a mechanism to invalidate the session token once it has expired, and do not allow it to be reactivated.
3. Consider using a secure session management library that handles these issues automatically.
4. Regularly rotate session tokens to limit the potential damage if a token is compromised.
5. Consider implementing additional security measures, such as re-authentication for sensitive operations.

Secure Code Example

import 'package:shelf/shelf.dart' as shelf;

class Session {
  final String id;
  final DateTime expirationTime;

  Session(this.id, this.expirationTime);
}

final sessionMap = <String, Session>{};

shelf.Response handleRequest(shelf.Request request) {
  final sessionId = request.headers['sessionId'];
  final session = sessionMap[sessionId];
  
  if (session != null && DateTime.now().isBefore(session.expirationTime)) {
    // Handle authenticated request
    return shelf.Response.ok('Authenticated request');
  } else {
    // Handle unauthenticated request
    // Remove the expired session from the sessionMap
    sessionMap.remove(sessionId);
    return shelf.Response.forbidden('Unauthenticated request');
  }
}

void main() {
  var handler = const shelf.Pipeline().addMiddleware(shelf.logRequests()).addHandler(handleRequest);
  shelf.serve(handler, 'localhost', 8080);
}

The updated code includes a mechanism to invalidate the session token once it has expired. This is done by removing the expired session from the `sessionMap` in the `handleRequest` function. This ensures that once a session has expired, it cannot be reactivated by modifying the expiration time. The `Session` class has also been updated to make the `id` and `expirationTime` fields final. This means that once a `Session` object has been created, its `id` and `expirationTime` cannot be changed. This helps to ensure that the session expiration time is managed server-side and cannot be modified by the client. These changes help to mitigate the risk of session token manipulation by ensuring that expired session tokens cannot be reactivated and that the session expiration time cannot be modified after the session has been created. For further security, consider using a secure session management library that handles these issues automatically, regularly rotating session tokens to limit the potential damage if a token is compromised, and implementing additional security measures such as re-authentication for sensitive operations.

References

Last updated

2023/09/18