inputfilter.php

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<?php
/**
 *  @class: InputFilter (PHP4 & PHP5, with comments)
 * @project: PHP Input Filter
 * @date: 10-05-2005
 * @version: 1.2.2_php4/php5
 * @author: Daniel Morris
 * @contributors: Gianpaolo Racca, Ghislain Picard, Marco Wandschneider, Chris
 * Tobin and Andrew Eddie.
 *
 * Modification by Louis Landry
 *
 * @copyright: Daniel Morris
 * @email: [e-mail]
 * @license: GNU General Public License (GPL)
 */
class InputFilter
{
	var $tagsArray; // default = empty array
	var $attrArray; // default = empty array

	var $tagsMethod; // default = 0
	var $attrMethod; // default = 0

	var $xssAuto; // default = 1
	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 $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		$xssAuto	Only auto clean essentials = 0, Allow clean
	 * blacklisted tags/attr = 1
	 */
	function inputFilter($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;
	}

	/**
	 * Method to be called by another php script. Processes for XSS and
	 * specified bad code.
	 *
	 * @access	public
	 * @param	mixed	$source	Input string/array-of-string to be 'cleaned'
	 * @return mixed	$source	'cleaned' version of input parameter
	 */
	function process($source)
	{
		/*
		 * 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));
				}
			}
			return $source;
		} else
			/*
			 * Or a string?
			 */
			if (is_string($source) && !empty ($source))
			{
				// filter source for XSS and other 'bad' code etc.
				return $this->remove($this->decode($source));
			} else
			{
				/*
				 * Not an array or string.. return the passed parameter
				 */
				return $source;
			}
	}

	/**
	 * Internal method to iteratively remove all unwanted tags and attributes
	 *
	 * @access	protected
	 * @param	string	$source	Input string to be 'cleaned'
	 * @return	string	$source	'cleaned' version of input parameter
	 */
	function remove($source)
	{
		$loopCounter = 0;
		/*
		 * Iteration provides nested tag protection
		 */
		while ($source != $this->filterTags($source))
		{
			$source = $this->filterTags($source);
			$loopCounter ++;
		}
		return $source;
	}

	/**
	 * Internal method to strip a string of certain tags
	 *
	 * @access	protected
	 * @param	string	$source	Input string to be 'cleaned'
	 * @return	string	$source	'cleaned' version of input parameter
	 */
	function filterTags($source)
	{
		/*
		 * In the beginning we don't really have a tag, so everything is
		 * postTag
		 */
		$preTag		= null;
		$postTag	= $source;

		/*
		 * 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)
			{
				$fromSpace		= substr($tagLeft, ($currentSpace +1));
				$nextSpace		= strpos($fromSpace, ' ');
				$openQuotes		= strpos($fromSpace, '"');
				$closeQuotes	= strpos(substr($fromSpace, ($openQuotes +1)), '"') + $openQuotes +1;

				/*
				 * Do we have an attribute to process? [check for equal sign]
				 */
				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]
					 */
					$attr = substr($fromSpace, 0, $nextSpace);
				}

				// Last Attribute Pair
				if (!$attr)
				{
					$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 = $this->filterAttr($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
	 *
	 * @access	protected
	 * @param	array	$attrSet	Array of attribute pairs to filter
	 * @return	array	$newSet		Filtered array of attribute pairs
	 */
	function filterAttr($attrSet)
	{
		/*
		 * Initialize variables
		 */
		$newSet = array ();

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

			/*
			 * Split into name/value pairs
			 */
			$attrSubSet = explode('=', trim($attrSet[$i]), 2);
			list ($attrSubSet[0]) = explode(' ', $attrSubSet[0]);

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

			/*
			 * XSS attribute value filtering
			 */
			if ($attrSubSet[1])
			{
				// strips unicode, hex, etc
				$attrSubSet[1] = str_replace('&#', '', $attrSubSet[1]);
				// strip normal newline within attr value
				$attrSubSet[1] = preg_replace('/\s+/', '', $attrSubSet[1]);
				// strip double quotes
				$attrSubSet[1] = str_replace('"', '', $attrSubSet[1]);
				// [requested feature] convert single quotes from either side to doubles (Single quotes shouldn't be used to pad attr value)
				if ((substr($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]);
			}

			/*
			 * Autostrip script tags
			 */
			if (InputFilter::badAttributeValue($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 && !$this->attrMethod))
			{
				/*
				 * Does the attribute have a value?
				 */
				if ($attrSubSet[1])
				{
					$newSet[] = $attrSubSet[0].'="'.$attrSubSet[1].'"';
				}
				elseif ($attrSubSet[1] == "0")
				{
					/*
					 * Special Case
					 * Is the value 0?
					 */
					$newSet[] = $attrSubSet[0].'="0"';
				} else
				{
					$newSet[] = $attrSubSet[0].'="'.$attrSubSet[0].'"';
				}
			}
		}
		return $newSet;
	}

	/**
	 * Function to determine if contents of an attribute is safe
	 *
	 * @access	protected
	 * @param	array	$attrSubSet	A 2 element array for attributes name,value
	 * @return	boolean True if bad code is detected
	 */
	function badAttributeValue($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));
	}

	/**
	 * Try to convert to plaintext
	 *
	 * @access	protected
	 * @param	string	$source
	 * @return	string	Plaintext string
	 */
	function decode($source)
	{
		// url decode
		$source = html_entity_decode($source, ENT_QUOTES, "ISO-8859-1");
		// convert decimal
		$source = preg_replace('/&#(\d+);/me', "chr(\\1)", $source); // decimal notation
		// convert hex
		$source = preg_replace('/&#x([a-f0-9]+);/mei', "chr(0x\\1)", $source); // hex notation
		return $source;
	}

	/**
	 * Method to be called by another php script. Processes for SQL injection
	 *
	 * @access	public
	 * @param	mixed		$source	input string/array-of-string to be 'cleaned'
	 * @param	resource	$connection - An open MySQL connection
	 * @return	string		'cleaned' version of input parameter
	 */
	function safeSQL($source, & $connection)
	{
		// clean all elements in this array
		if (is_array($source))
		{
			foreach ($source as $key => $value)
			{
				// filter element for SQL injection
				if (is_string($value))
				{
					$source[$key] = $this->quoteSmart($this->decode($value), $connection);
				}
			}
			return $source;
			// clean this string
		} else
			if (is_string($source))
			{
				// filter source for SQL injection
				if (is_string($source))
				{
					return $this->quoteSmart($this->decode($source), $connection);
				}
				// return parameter as given
			} else
			{
				return $source;
			}
	}

	/**
	 * Method to escape a string
	 *
	 * @author	Chris Tobin
	 * @author	Daniel Morris
	 *
	 * @access	protected
	 * @param	string		$source
	 * @param	resource	$connection		An open MySQL connection
	 * @return	string		Escaped string
	 */
	function quoteSmart($source, & $connection)
	{
		/*
		 * Strip escaping slashes if necessary
		 */
		if (get_magic_quotes_gpc())
		{
			$source = stripslashes($source);
		}

		/*
		 * Escape numeric and text values
		 */
		$source = $this->escapeString($source, $connection);
		return $source;
	}

	/**
	 * @author	Chris Tobin
	 * @author	Daniel Morris
	 *
	 * @access	protected
	 * @param	string		$source
	 * @param	resource	$connection		An open MySQL connection
	 * @return	string		Escaped string
	 */
	function escapeString($string, & $connection) {
		/*
		* Use the appropriate escape string depending upon which version of php
		* you are running
		*/
		if (version_compare(phpversion(), '4.3.0', '<')) {
			$string = mysql_escape_string($string);
		} else 	{
			$string = mysql_real_escape_string($string);
		}

		return $string;
	}
}
?>