/joomla/libraries/joomla/filter/filterinput.php

<?php
/**
 * @version		$Id: filterinput.php 20899 2011-03-07 20:56:09Z ian $
 * @package		Joomla.Framework
 * @subpackage	Filter
 * @copyright	Copyright (C) 2005 - 2011 Open Source Matters, Inc. All rights reserved.
 * @license		GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access
defined('JPATH_BASE') or die;

/**
 * JFilterInput is a class for filtering input from any data source
 *
 * Forked from the php input filter library by: Daniel Morris <dan@rootcube.com>
 * Original Contributors: Gianpaolo Racca, Ghislain Picard, Marco Wandschneider, Chris Tobin and Andrew Eddie.
 *
 * @package		Joomla.Framework
 * @subpackage	Filter
 * @since		1.5
 */
class JFilterInput extends JObject
{
	/**
	 * @var		array	An array of permitted tags.
	 * @since	1.5
	 */
	var $tagsArray;

	/**
	 * @var		array	An array of permitted tag attributes.
	 * @since	1.5
	 */
	var $attrArray;

	/**
	 * @var		int		WhiteList method = 0 (default), BlackList method = 1
	 * @since	1.5
	 */
	var $tagsMethod;

	/**
	 * @var		int		WhiteList method = 0 (default), BlackList method = 1
	 * @since	1.5
	 */
	var $attrMethod;

	/**
	 * @var		int		Only auto clean essentials = 0, Allow clean blacklisted tags/attr = 1
	 * @since	1.5
	 */
	var $xssAuto;

	/**
	 * @var		array	A list of the default blacklisted tags.
	 * @since	1.5
	 */
	var $tagBlacklist = array ('applet', 'body', 'bgsound', 'base', 'basefont', 'embed', 'frame', 'frameset', 'head', 'html', 'id', 'iframe', 'ilayer', 'layer', 'link', 'meta', 'name', 'object', 'script', 'style', 'title', 'xml');

	/**
	 * @var		array	A list of the default blacklisted tag attributes.
	 * @since	1.5
	 */
	var $attrBlacklist = array ('action', 'background', 'codebase', 'dynsrc', 'lowsrc'); // also will strip ALL event handlers

	/**
	 * Constructor for inputFilter class. Only first parameter is required.
	 *
	 * @access	protected
	 * @param	array	$tagsArray	List of user-defined tags
	 * @param	array	$attrArray	List of user-defined attributes
	 * @param	int		$tagsMethod	WhiteList method = 0, BlackList method = 1
	 * @param	int		$attrMethod	WhiteList method = 0, BlackList method = 1
	 * @param	int		$xssAuto	Only auto clean essentials = 0, Allow clean blacklisted tags/attr = 1
	 * @since	1.5
	 */
	public function __construct($tagsArray = array(), $attrArray = array(), $tagsMethod = 0, $attrMethod = 0, $xssAuto = 1)
	{
		// Make sure user defined arrays are in lowercase
		$tagsArray = array_map('strtolower', (array) $tagsArray);
		$attrArray = array_map('strtolower', (array) $attrArray);

		// Assign member variables
		$this->tagsArray	= $tagsArray;
		$this->attrArray	= $attrArray;
		$this->tagsMethod	= $tagsMethod;
		$this->attrMethod	= $attrMethod;
		$this->xssAuto		= $xssAuto;
	}

	/**
	 * Returns an input filter object, only creating it if it doesn't already exist.
	 *
	 * @param	array	$tagsArray	List of user-defined tags
	 * @param	array	$attrArray	List of user-defined attributes
	 * @param	int		$tagsMethod	WhiteList method = 0, BlackList method = 1
	 * @param	int		$attrMethod	WhiteList method = 0, BlackList method = 1
	 * @param	int		$xssAuto	Only auto clean essentials = 0, Allow clean blacklisted tags/attr = 1
	 * @return	object	The JFilterInput object.
	 * @since	1.5
	 */
	public static function &getInstance($tagsArray = array(), $attrArray = array(), $tagsMethod = 0, $attrMethod = 0, $xssAuto = 1)
	{
		static $instances;

		$sig = md5(serialize(array($tagsArray,$attrArray,$tagsMethod,$attrMethod,$xssAuto)));

		if (!isset ($instances)) {
			$instances = array();
		}

		if (empty ($instances[$sig])) {
			$instances[$sig] = new JFilterInput($tagsArray, $attrArray, $tagsMethod, $attrMethod, $xssAuto);
		}

		return $instances[$sig];
	}

	/**
	 * Method to be called by another php script. Processes for XSS and
	 * specified bad code.
	 *
	 * @param	mixed	$source	Input string/array-of-string to be 'cleaned'
	 * @param	string	$type	Return type for the variable (INT, FLOAT, BOOLEAN, WORD, ALNUM, CMD, BASE64, STRING, ARRAY, PATH, NONE)
	 * @return	mixed	'Cleaned' version of input parameter
	 * @since	1.5
	 * @static
	 */
	public function clean($source, $type='string')
	{
		// Handle the type constraint
		switch (strtoupper($type))
		{
			case 'INT' :
			case 'INTEGER' :
				// Only use the first integer value
				preg_match('/-?[0-9]+/', (string) $source, $matches);
				$result = @ (int) $matches[0];
				break;

			case 'FLOAT' :
			case 'DOUBLE' :
				// Only use the first floating point value
				preg_match('/-?[0-9]+(\.[0-9]+)?/', (string) $source, $matches);
				$result = @ (float) $matches[0];
				break;

			case 'BOOL' :
			case 'BOOLEAN' :
				$result = (bool) $source;
				break;

			case 'WORD' :
				$result = (string) preg_replace('/[^A-Z_]/i', '', $source);
				break;

			case 'ALNUM' :
				$result = (string) preg_replace('/[^A-Z0-9]/i', '', $source);
				break;

			case 'CMD' :
				$result = (string) preg_replace('/[^A-Z0-9_\.-]/i', '', $source);
				$result = ltrim($result, '.');
				break;

			case 'BASE64' :
				$result = (string) preg_replace('/[^A-Z0-9\/+=]/i', '', $source);
				break;

			case 'STRING' :
				$result = (string) $this->_remove($this->_decode((string) $source));
				break;

			case 'HTML' :
				$result = (string) $this->_remove((string) $source);
				break;

			case 'ARRAY' :
				$result = (array) $source;
				break;

			case 'PATH' :
				$pattern = '/^[A-Za-z0-9_-]+[A-Za-z0-9_\.-]*([\\\\\/][A-Za-z0-9_-]+[A-Za-z0-9_\.-]*)*$/';
				preg_match($pattern, (string) $source, $matches);
				$result = @ (string) $matches[0];
				break;

			case 'USERNAME' :
				$result = (string) preg_replace('/[\x00-\x1F\x7F<>"\'%&]/', '', $source);
				break;

			default :
				// Are we dealing with an array?
				if (is_array($source))
				{
					foreach ($source as $key => $value)
					{
						// filter element for XSS and other 'bad' code etc.
						if (is_string($value)) {
							$source[$key] = $this->_remove($this->_decode($value));
						}
					}
					$result = $source;
				}
				else
				{
					// Or a string?
					if (is_string($source) && !empty ($source)) {
						// filter source for XSS and other 'bad' code etc.
						$result = $this->_remove($this->_decode($source));
					}
					else {
						// Not an array or string.. return the passed parameter
						$result = $source;
					}
				}
				break;
		}
		return $result;
	}

	/**
	 * Function to determine if contents of an attribute is safe
	 *
	 * @param	array	$attrSubSet	A 2 element array for attributes name,value
	 * @return	boolean True if bad code is detected
	 * @since	1.5
	 */
	public static function checkAttribute($attrSubSet)
	{
		$attrSubSet[0] = strtolower($attrSubSet[0]);
		$attrSubSet[1] = strtolower($attrSubSet[1]);
		return (((strpos($attrSubSet[1], 'expression') !== false) && ($attrSubSet[0]) == 'style') || (strpos($attrSubSet[1], 'javascript:') !== false) || (strpos($attrSubSet[1], 'behaviour:') !== false) || (strpos($attrSubSet[1], 'vbscript:') !== false) || (strpos($attrSubSet[1], 'mocha:') !== false) || (strpos($attrSubSet[1], 'livescript:') !== false));
	}

	/**
	 * Internal method to iteratively remove all unwanted tags and attributes
	 *
	 * @param	string	$source	Input string to be 'cleaned'
	 * @return	string	'Cleaned' version of input parameter
	 * @since	1.5
	 */
	protected function _remove($source)
	{
		$loopCounter = 0;

		// Iteration provides nested tag protection
		while ($source != $this->_cleanTags($source)) {
			$source = $this->_cleanTags($source);
			$loopCounter ++;
		}
		return $source;
	}

	/**
	 * Internal method to strip a string of certain tags
	 *
	 * @param	string	Input string to be 'cleaned'
	 * @return	string	'Cleaned' version of input parameter
	 * @since	1.5
	 */
	protected function _cleanTags($source)
	{
		// First, pre-process this for illegal characters inside attribute values
		$source = $this->_escapeAttributeValues($source);
		// In the beginning we don't really have a tag, so everything is postTag
		$preTag		= null;
		$postTag	= $source;
		$currentSpace = false;
		$attr = '';	// moffats: setting to null due to issues in migration system - undefined variable errors

		// Is there a tag? If so it will certainly start with a '<'
		$tagOpen_start	= strpos($source, '<');

		while ($tagOpen_start !== false) {
			// Get some information about the tag we are processing
			$preTag			.= substr($postTag, 0, $tagOpen_start);
			$postTag		= substr($postTag, $tagOpen_start);
			$fromTagOpen	= substr($postTag, 1);
			$tagOpen_end	= strpos($fromTagOpen, '>');

			// Let's catch any non-terminated tags and skip over them
			if ($tagOpen_end === false) {
				$postTag		= substr($postTag, $tagOpen_start +1);
				$tagOpen_start	= strpos($postTag, '<');
				continue;
			}

			// Do we have a nested tag?
			$tagOpen_nested = strpos($fromTagOpen, '<');
			$tagOpen_nested_end	= strpos(substr($postTag, $tagOpen_end), '>');
			if (($tagOpen_nested !== false) && ($tagOpen_nested < $tagOpen_end)) {
				$preTag			.= substr($postTag, 0, ($tagOpen_nested +1));
				$postTag		= substr($postTag, ($tagOpen_nested +1));
				$tagOpen_start	= strpos($postTag, '<');
				continue;
			}

			// Lets get some information about our tag and setup attribute pairs
			$tagOpen_nested	= (strpos($fromTagOpen, '<') + $tagOpen_start +1);
			$currentTag		= substr($fromTagOpen, 0, $tagOpen_end);
			$tagLength		= strlen($currentTag);
			$tagLeft		= $currentTag;
			$attrSet		= array ();
			$currentSpace	= strpos($tagLeft, ' ');

			// Are we an open tag or a close tag?
			if (substr($currentTag, 0, 1) == '/') {
				// Close Tag
				$isCloseTag		= true;
				list ($tagName)	= explode(' ', $currentTag);
				$tagName		= substr($tagName, 1);
			} else {
				// Open Tag
				$isCloseTag		= false;
				list ($tagName)	= explode(' ', $currentTag);
			}

			/*
			 * Exclude all "non-regular" tagnames
			 * OR no tagname
			 * OR remove if xssauto is on and tag is blacklisted
			 */
			if ((!preg_match("/^[a-z][a-z0-9]*$/i", $tagName)) || (!$tagName) || ((in_array(strtolower($tagName), $this->tagBlacklist)) && ($this->xssAuto))) {
				$postTag		= substr($postTag, ($tagLength +2));
				$tagOpen_start	= strpos($postTag, '<');
				// Strip tag
				continue;
			}

			/*
			 * Time to grab any attributes from the tag... need this section in
			 * case attributes have spaces in the values.
			 */
			while ($currentSpace !== false) {
				$attr			= '';
				$fromSpace		= substr($tagLeft, ($currentSpace +1));
				$nextEqual		= strpos($fromSpace, '=');
				$nextSpace		= strpos($fromSpace, ' ');
				$openQuotes		= strpos($fromSpace, '"');
				$closeQuotes	= strpos(substr($fromSpace, ($openQuotes +1)), '"') + $openQuotes +1;
				
				$startAtt = '';
				$startAttPosition = 0;
				
				// Find position of equal and open quotes ignoring 
				if (preg_match('#\s*=\s*\"#', $fromSpace, $matches, PREG_OFFSET_CAPTURE)) {
					$startAtt = $matches[0][0];
					$startAttPosition = $matches[0][1];
					$closeQuotes = strpos(substr($fromSpace, ($startAttPosition + strlen($startAtt))), '"') + $startAttPosition + strlen($startAtt);
					$nextEqual = $startAttPosition + strpos($startAtt, '=');
					$openQuotes = $startAttPosition + strpos($startAtt, '"');
					$nextSpace = strpos(substr($fromSpace, $closeQuotes), ' ') + $closeQuotes;
				}

				

				// Do we have an attribute to process? [check for equal sign]
				if ($fromSpace != '/' && (($nextEqual && $nextSpace && $nextSpace < $nextEqual ) || !$nextEqual))
				{
					if(!$nextEqual)
					{
						$attribEnd = strpos($fromSpace, '/') - 1;
					} else {
						$attribEnd = $nextSpace - 1;
					}
					// if there is an ending, use this, if not do not worry
					if($attribEnd > 0)
					{
						$fromSpace = substr($fromSpace, $attribEnd + 1);
					}
				}
				if (strpos($fromSpace, '=') !== false) {
					/*
					 * If the attribute value is wrapped in quotes we need to
					 * grab the substring from the closing quote, otherwise grab
					 * till the next space
					 */
					if (($openQuotes !== false) && (strpos(substr($fromSpace, ($openQuotes +1)), '"') !== false)) {
						$attr = substr($fromSpace, 0, ($closeQuotes +1));
					} else {
						$attr = substr($fromSpace, 0, $nextSpace);
					}
				} else {
					/*
					 * No more equal signs so add any extra text in the tag into
					 * the attribute array [eg. checked]
					 */
					if ($fromSpace != '/') {
						$attr = substr($fromSpace, 0, $nextSpace);
					}
				}

				// Last Attribute Pair
				if (!$attr && $fromSpace != '/') {
					$attr = $fromSpace;
				}

				// Add attribute pair to the attribute array
				$attrSet[] = $attr;

				// Move search point and continue iteration
				$tagLeft		= substr($fromSpace, strlen($attr));
				$currentSpace	= strpos($tagLeft, ' ');
			}

			// Is our tag in the user input array?
			$tagFound = in_array(strtolower($tagName), $this->tagsArray);

			// If the tag is allowed lets append it to the output string
			if ((!$tagFound && $this->tagsMethod) || ($tagFound && !$this->tagsMethod)) {
				// Reconstruct tag with allowed attributes
				if (!$isCloseTag) {
					// Open or Single tag
					$attrSet = $this->_cleanAttributes($attrSet);
					$preTag .= '<'.$tagName;
					for ($i = 0; $i < count($attrSet); $i ++) {
						$preTag .= ' '.$attrSet[$i];
					}

					// Reformat single tags to XHTML
					if (strpos($fromTagOpen, '</'.$tagName)) {
						$preTag .= '>';
					} else {
						$preTag .= ' />';
					}
				} else {
					// Closing Tag
					$preTag .= '</'.$tagName.'>';
				}
			}

			// Find next tag's start and continue iteration
			$postTag		= substr($postTag, ($tagLength +2));
			$tagOpen_start	= strpos($postTag, '<');
		}

		// Append any code after the end of tags and return
		if ($postTag != '<') {
			$preTag .= $postTag;
		}
		return $preTag;
	}

	/**
	 * Internal method to strip a tag of certain attributes
	 *
	 * @param	array	$attrSet	Array of attribute pairs to filter
	 * @return	array	Filtered array of attribute pairs
	 * @since	1.5
	 */
	protected function _cleanAttributes($attrSet)
	{
		// Initialise variables.
		$newSet = array();

		$count = count($attrSet);
		// Iterate through attribute pairs
		for ($i = 0; $i < $count; $i ++) {
			// Skip blank spaces
			if (!$attrSet[$i]) {
				continue;
			}

			// Split into name/value pairs
			$attrSubSet = explode('=', trim($attrSet[$i]), 2);
			// Take the last attribute in case there is an attribute with no value
			$attrSubSet[0] = array_pop(explode(' ', trim($attrSubSet[0])));

			/*
			 * Remove all "non-regular" attribute names
			 * AND blacklisted attributes
			 */
			if ((!preg_match('/[a-z]*$/i', $attrSubSet[0])) || (($this->xssAuto) && ((in_array(strtolower($attrSubSet[0]), $this->attrBlacklist)) || (substr($attrSubSet[0], 0, 2) == 'on')))) {
				continue;
			}

			// XSS attribute value filtering
			if (isset($attrSubSet[1])) {
				// trim leading and trailing spaces
				$attrSubSet[1] = trim($attrSubSet[1]);
				// strips unicode, hex, etc
				$attrSubSet[1] = str_replace('&#', '', $attrSubSet[1]);
				// strip normal newline within attr value
				$attrSubSet[1] = preg_replace('/[\n\r]/', '', $attrSubSet[1]);
				// strip double quotes
				$attrSubSet[1] = str_replace('"', '', $attrSubSet[1]);
				// convert single quotes from either side to doubles (Single quotes shouldn't be used to pad attr value)
				if ((substr($attrSubSet[1], 0, 1) == "'") && (substr($attrSubSet[1], (strlen($attrSubSet[1]) - 1), 1) == "'")) {
					$attrSubSet[1] = substr($attrSubSet[1], 1, (strlen($attrSubSet[1]) - 2));
				}
				// strip slashes
				$attrSubSet[1] = stripslashes($attrSubSet[1]);
			} else {
				continue;
			}

			// Autostrip script tags
			if (self::checkAttribute($attrSubSet)) {
				continue;
			}

			// Is our attribute in the user input array?
			$attrFound = in_array(strtolower($attrSubSet[0]), $this->attrArray);

			// If the tag is allowed lets keep it
			if ((!$attrFound && $this->attrMethod) || ($attrFound && !$this->attrMethod)) {
				// Does the attribute have a value?
				if (empty($attrSubSet[1]) === false) {
					$newSet[] = $attrSubSet[0].'="'.$attrSubSet[1].'"';
				} else if ($attrSubSet[1] === "0") {
					/*
					 * Special Case
					 * Is the value 0?
					 */
					$newSet[] = $attrSubSet[0].'="0"';
				} else {
					// Leave empty attributes alone
					$newSet[] = $attrSubSet[0].'=""';
				}
			}
		}
		return $newSet;
	}

	/**
	 * Try to convert to plaintext
	 *
	 * @param	string	$source The source string.
	 * @return	string	Plaintext string
	 * @since	1.5
	 */
	protected function _decode($source)
	{
		static $ttr;

		if(!is_array($ttr))
		{
			// entity decode
			$trans_tbl = get_html_translation_table(HTML_ENTITIES);
			foreach($trans_tbl as $k => $v) {
				$ttr[$v] = utf8_encode($k);
			}
		}
		$source = strtr($source, $ttr);
		// convert decimal
		$source = preg_replace('/&#(\d+);/me', "utf8_encode(chr(\\1))", $source); // decimal notation
		// convert hex
		$source = preg_replace('/&#x([a-f0-9]+);/mei', "utf8_encode(chr(0x\\1))", $source); // hex notation
		return $source;
	}
	
	/**
	 * Escape < > and " inside attribute values
	 *
	 * @param	string	$source The source string.
	 * @return	string	Filtered string
	 * @since	1.6
	 */
	protected function _escapeAttributeValues($source)
	{
		$alreadyFiltered = '';
		$remainder = $source;
		$badChars = array ('<', '"', '>');
		$escapedChars = array ('&lt;', '&quot;', '&gt;');
		// Process each portion based on presence of =" and "<space>, "/>, or ">
		// See if there are any more attributes to process
		while (preg_match('#\s*=\s*\"#', $remainder, $matches, PREG_OFFSET_CAPTURE))
		{
			// get the portion before the attribute value
			$quotePosition = $matches[0][1];
			$nextBefore = $quotePosition + strlen($matches[0][0]);
			// get the portion after attribute value
			if (preg_match('#(\"\s*/\s*>|\"\s*>|\"\s+|\"$)#', substr($remainder, $nextBefore), $matches, PREG_OFFSET_CAPTURE)) {
				// We have a closing quote
				$nextAfter = $nextBefore + $matches[0][1];
			} else {
				// No closing quote
				$nextAfter = strlen($remainder);
			}
			// Get the actual attribute value
			$attributeValue = substr($remainder, $nextBefore, $nextAfter - $nextBefore);
			// Escape bad chars
			$attributeValue = str_replace($badChars, $escapedChars, $attributeValue);
			$alreadyFiltered .= substr($remainder, 0, $nextBefore) . $attributeValue . '"';
			$remainder = substr($remainder, $nextAfter + 1);
		}
		
		// At this point, we just have to return the $alreadyFiltered and the $remainder
		return $alreadyFiltered . $remainder;
	}	
}