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<?php
/**
* Zend Framework (http://framework.zend.com/)
*
* @link http://github.com/zendframework/zf2 for the canonical source repository
* @copyright Copyright (c) 2005-2014 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
*/
namespace ZendXml;
use DOMDocument;
use SimpleXMLElement;
class Security
{
const ENTITY_DETECT = 'Detected use of ENTITY in XML, disabled to prevent XXE/XEE attacks';
/**
* Heuristic scan to detect entity in XML
*
* @param string $xml
* @throws Exception\RuntimeException
*/
protected static function heuristicScan($xml)
{
if (strpos($xml, '<!ENTITY') !== false) {
throw new Exception\RuntimeException(self::ENTITY_DETECT);
}
}
/**
* Scan XML string for potential XXE and XEE attacks
*
* @param string $xml
* @param DomDocument $dom
* @param int $libXmlConstants additional libxml constants to pass in
* @param Callable $callback the callback to use to create the dom element
* @throws Exception\RuntimeException
* @return SimpleXMLElement|DomDocument|boolean
*/
private static function scanString($xml, $dom, $libXmlConstants, $callback)
{
// If running with PHP-FPM we perform an heuristic scan
// We cannot use libxml_disable_entity_loader because of this bug
// @see https://bugs.php.net/bug.php?id=64938
if (self::isPhpFpm()) {
self::heuristicScan($xml);
}
if (null === $dom) {
$simpleXml = true;
$dom = new DOMDocument();
}
if (!self::isPhpFpm()) {
$loadEntities = libxml_disable_entity_loader(true);
$useInternalXmlErrors = libxml_use_internal_errors(true);
}
// Load XML with network access disabled (LIBXML_NONET)
// error disabled with @ for PHP-FPM scenario
set_error_handler(function ($errno, $errstr) {
if (substr_count($errstr, 'DOMDocument::loadXML()') > 0) {
return true;
}
return false;
}, E_WARNING);
$result = $callback($xml, $dom, LIBXML_NONET | $libXmlConstants);
restore_error_handler();
// Entity load to previous setting
if (!self::isPhpFpm()) {
libxml_disable_entity_loader($loadEntities);
libxml_use_internal_errors($useInternalXmlErrors);
}
if (!$result) {
return false;
}
// Scan for potential XEE attacks using ENTITY, if not PHP-FPM
if (!self::isPhpFpm()) {
foreach ($dom->childNodes as $child) {
if ($child->nodeType === XML_DOCUMENT_TYPE_NODE) {
if ($child->entities->length > 0) {
throw new Exception\RuntimeException(self::ENTITY_DETECT);
}
}
}
}
if (isset($simpleXml)) {
$result = simplexml_import_dom($dom);
if (!$result instanceof SimpleXMLElement) {
return false;
}
return $result;
}
return $dom;
}
/**
* Scan HTML string for potential XXE and XEE attacks
*
* @param string $xml
* @param DomDocument $dom
* @param int $libXmlConstants additional libxml constants to pass in
* @throws Exception\RuntimeException
* @return SimpleXMLElement|DomDocument|boolean
*/
public static function scanHtml($html, DOMDocument $dom = null, $libXmlConstants = 0)
{
$callback = function ($html, $dom, $constants) {
return $dom->loadHtml($html, $constants);
};
return self::scanString($html, $dom, $libXmlConstants, $callback);
}
/**
* Scan XML string for potential XXE and XEE attacks
*
* @param string $xml
* @param DomDocument $dom
* @param int $libXmlConstants additional libxml constants to pass in
* @throws Exception\RuntimeException
* @return SimpleXMLElement|DomDocument|boolean
*/
public static function scan($xml, DOMDocument $dom = null, $libXmlConstants = 0)
{
$callback = function ($xml, $dom, $constants) {
return $dom->loadXml($xml, $constants);
};
return self::scanString($xml, $dom, $libXmlConstants, $callback);
}
/**
* Scan XML file for potential XXE/XEE attacks
*
* @param string $file
* @param DOMDocument $dom
* @throws Exception\InvalidArgumentException
* @return SimpleXMLElement|DomDocument
*/
public static function scanFile($file, DOMDocument $dom = null)
{
if (!file_exists($file)) {
throw new Exception\InvalidArgumentException(
"The file $file specified doesn't exist"
);
}
return self::scan(file_get_contents($file), $dom);
}
/**
* Return true if PHP is running with PHP-FPM
*
* @return boolean
*/
public static function isPhpFpm()
{
if (substr(php_sapi_name(), 0, 3) === 'fpm') {
return true;
}
return false;
}
}
|
