istais/reflectshield

ReflectShield is a simple to use, shield against reflected XSS attacks

dev-master 2017-01-23 14:09 UTC

This package is not auto-updated.

Last update: 2020-01-24 16:23:34 UTC


README

#ReflectShield

ReflectShield migrates a part of Chrome XSS Protection on the server side. ReflectShield checks whether a script that’s about to run on a web page is also present in the request that fetched that web page. If the script is present in the request, that’s a strong indication that the web server might have been tricked into reflecting the script. Therefore, it blocks the reflected XSS attacks by translating all characters of this request parameter which have HTML character entity equivalents into these entities.

Furthermore, ReflectShield introduces a similar technique in order to mitigate SQL injection vulnerabilities. ReflectShield hooks common vulnerable MySQL API calls, and checks whether parameters from the request that fetched that web page are also present in the executing SQL queries. If the request parameters are present in the query, and these are not parts of atomic SQL tokens, that's a strong indication that the web server might have been tricked into executing malicious SQL statements.

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##The Chrome XSS Protection:

XSS Auditor is a built-in function of Chrome and Safari designed to mitigate Cross-site Scripting (XSS) attacks. It aims to identify if query parameters contain malicious JavaScript and block the response if it believes the payloads were injected into the server response. XSS Auditor takes a black list approach to identify dangerous characters and tags supplied in request parameters. It also attempts to match query parameters with content to identify injection points.

##The ReflectShield protects from:

  • Reflected Cross Site Scripting Attacks: Non-persistent XSS issues, which occur when the web application blindly echos parts of the HTTP request in the respective HTTP response’s HTML. In order to successfully exploit a reflected XSS vulnerability, the adversary has to trick the victim into sending a fabricated HTTP request. This can be done by, for instance, sending the victim a malicious link, or including a hidden Iframe into an attacker controlled page.

  • SQL Injection Attacks: Injection issues, in which SQL commands are injected into data-plane input in order to effect the execution of predefined SQL commands. Currently, ReflectShield is able to detect injections in "mysql_query" and "mysqli_query" functions.

##Installation:

  • ReflectShield uses PHP Patchwork in order to perform dynamic method redefinition. As a result, in order the patching to be successful, the recommended way is to import ReflectShield first in separated initialization file, as the redefinition will not work on any script compiled earlier than itself, and any used MySQL function at this step will remain unprotected. It is recommended to create an index file as the following, and include your " application.php", which has to verify that the variable "protect" is set.

     use ReflectShield\ReflectShield;
     $shield = new ReflectShield;
     
     define("protect",true);
     include __DIR__ . application.php

##Direct integration by circumventing the preprocessor:

  • you can use directly ReflectShield in your PHP scripts, by requesting a new object at the beggining of the script. Including the file agail, allows the preprocessor to implement the method redefinition correctly:

     use ReflectShield\ReflectShield;
     if(!isset($AVOIDPREPROCESS)){ 
     	$AVOIDPREPROCESS = true;
     	$shield = new ReflectShield;
     	include __FILE__;
     	return;
     }
  • Preprocessing is necessary for patching MySQL API calls in order to mitigate SQL injection vulnerabilities. If the protection for SQL injections is not necessary for your site, you can use the following simple object request:

     use ReflectShield\ReflectShield;
     $shield = new ReflectShield;
  • The .htaccess files are also an installation option. Paste the following into your .htaccess file and it will enable ReflectShield across all pages in the directory where the .htaccess file resides:

     php_value auto_prepend_file /var/www/html/reflectshield/examples/usinghtaccess/initReflectShield.php
    

    If .htaccess files are not enabled, check the following site https://help.ubuntu.com/community/EnablingUseOfApacheHtaccessFiles

##Limitations of ReflectShield:

  • Input Mutations: ReflectShield attempts to match query parameters with content to identify injection points. If the query parameter can’t be matched to content in the response, the ReflectShield will not be triggered. As a result, if the web application performs any kind of modification on the input parameters, will render the ReflectShield useless in preventing attacks.

  • Reflected JavaScript Injections: If a query parameter is matched to content in the response, the ReflectShield will translate all characters of this content which have HTML character entity equivalents into these entities. However, reflected JavaScript injections can occur even without characters that have entity equivalents.

  • DOM Based XSS: XSS vulnerabilities which are caused by insecure client-side code which handles inappropriate the data from its associated DOM. DOM consists of objects representing the document properties from the point of view of the browser. These issues come to light when untrusted DOM data is used in a security-critical context, such as a call to eval. ReflectShield does not protect from DOM based XSS, since the vulnerability resides in the script code from the website and the injection payloads are not reflected directly in the response or always transmitted to the server.

  • Persistent/Stored XSS: All XSS vulnerabilities, where the adversary is able to permanently inject the malicious script in the vulnerable application’s storage. This way every user that accesses the poisoned web page receives the injected script without further actions by the adversary. ReflectShield can only handle reflected injections.

  • Multiple Step XSS: These vulnerabilities require the user to perform several actions on the applications to execute the attack vector/injected malicious JavaScript code. The main characteristics of multiple step XSS vulnerabilities are that the attack vector is injected in one page and then echoed in another page or application later. ReflectShield can only handle reflected injections on the same request.