taint: PHP extension, used for detecting XSS codes

by do son · September 6, 2017

Taint

php extension used to detect XSS codes(tainted string), And also can be used to spot sql injection vulnerabilities, shell inject, etc.

The idea is from https://wiki.php.net/rfc/taint, I implemented it in a php extension which make the patch no-needed.

Please note that do not enable this extension in product env, since it will slowdown your app.

Install

Requirement:

PHP 5.2+



taint is an PECL extension, thus you can simply install it by:

pecl install taint



Compile taint in Linux

$/path/to/phpize

$./configure --with-php-config=/path/to/php-config/

$make && make install

Usage

When taint is enabled, if you pass a tainted string(comes from $_GET, $_POST or $_COOKIE) to some functions, taint will warn you about that.

<?php

$a = trim($_GET['a']);



$file_name = '/tmp' .  $a;

$output    = "Welcome, {$a} !!!";

$var       = "output";

$sql       = "Select *  from " . $a;

$sql      .= "ooxx";



echo $output;



print $$var;



include($file_name);



mysql_query($sql);

The above example will output something similar to:

Warning: main() [function.echo]: Attempt to echo a string that might be tainted



Warning: main() [function.echo]: Attempt to print a string that might be tainted



Warning: include() [function.include]: File path contains data that might be tainted



Warning: mysql_query() [function.mysql-query]: SQL statement contains data that might be tainted