PHP CSRF Protection class: Prevent CSRF request security attacks

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Version License PHP version Categories
csrf-protector 2BSD License5.4HTML, PHP 5, Security
Description Author

This package can be used to prevent CSRF request security attacks.

It can register a PHP shutdown function that will capture the current page output so it can be captured to be processed by the class.

It can parse the HTML of the captured page and replace the URLs of the links and forms to add a token that can be verified later to prevent Cross-Site Request Forgery attacks by validating the token.

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Details

CSRFProtector

Protect against CSRF attack. PHP >= 5.4

Introduction

Cross-site request forgery, also known as a one-click attack or session riding and abbreviated as CSRF (sometimes pronounced sea-surf) or XSRF, is a type of malicious exploit of a website whereby unauthorized commands are transmitted from a user that the website trusts. Unlike cross-site scripting (XSS), which exploits the trust a user has for a particular site, CSRF exploits the trust that a site has in a user's browser. This class can be usefull to also avoid some sort of javascript scripts that attemps a human simulation or a DOS attack.

Why I should use this class?

Most of others PHP scripts require that you manually edit link and form one by one. In medium and big size application, this is not only stressful but also dangerous because as human you can do mistakes. CSRFProtector, instead, do the job automatically!

Just before the end of the scripts, it search in the output buffered each links and forms. Then, they are modified adding a speacial randomic token: tokens are then saved in sessions to create a white list. When a web request come to your server, CSFRProtector check if the associated token is in the permitted list: if yes then the script can continue, otherwise a error is shown. Not only: it also add a flag in session with the end time of script execution and you can choose when the next request is accepted.

So sum up:

  • CSRF protection
  • Bot scripts protection
  • Race conditions
  • No cookie or database used

To do:

  • Enable ajax
  • Enable javascript redirect

Installation

First off all, download and unzip all the contents in a folder in your server. Let's suppose is libs. At the begin of your main script, add this code

  
require ("libs/CSRFProtector-master/CSRFProtector.php");
$jsPath = "CSRFProtector"; // path where is native.history.js
$csrf = new CSRFProtector($jsPath);
$csrf->run();
  

That is all! Anyway it's more powerfull than what might seem.

Advanced configurations

The construct can take three optional arguments:

  1. A string path where is located native.history.js (browser will search for {yourpath}/native.history.js)
  2. A callable function that will be called when CSRF attack are discovered (standard action is to end the script and display "CSFR protection")
  3. A callable function that generate the token(by default is a composition of 3 randomic value)
  4. The maximum life time of tokens in seconds(default is 120 seconds)
  5. The minimum time requested between the current script end time and the next request(default is 1 second)

$error = function(){
  die("Nice try dude");  
};

$token = function(){
    return "_".mt_rand(1,200).md5(mt_rand(2,100));
};

$time = 30; //in seconds
$min = 0; // in seconds
$jsPath = "CSRFProtector"; // path where is native.history.js

$csrf = new CSRFProtector($jsPath,$error,$token,$time,$min);
$csrf->run();

It's also possible to manually protect GET and POST data using fews function:


$auto = false;
$jsPath = "CSRFProtector";
$csrf = new CSRFProtector($jsPath);
$csrf->run($auto);

<html>
  <body>
    <a href="<?php echo $csrf->protectUrl("index.php"); ?>">a link</a>
    
    <form action="form.php" method="post">
      <?php echo $csrf->getFormHiddenComponent(); ?>
    </form> 
  </body>
</html>


  Files  
File Role Description
core (3 files)
examples (1 file)
CSRFProtector.php Class Class source
native.history.js Data Auxiliary data
readme.html Doc. Documentation
README.md Doc. Documentation

  Files  /  core  
File Role Description
   CSRFBackEnd.php Class Class source
   CSRFFrontEnd.php Class Class source
   TokenManager.php Class Class source

  Files  /  examples  
File Role Description
   Sample.php Example Example script

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