<?php
// (c) Copyright 2002-2016 by authors of the Tiki Wiki CMS Groupware Project
//
// All Rights Reserved. See copyright.txt for details and a complete list of authors.
// Licensed under the GNU LESSER GENERAL PUBLIC LICENSE. See license.txt for details.
// $Id: PreventXss.php 57949 2016-03-17 19:30:36Z jyhem $

class TikiFilter_PreventXss implements Zend\Filter\FilterInterface
{
	function filter( $value )
	{
		// No need to filter really simple values
		if ( ctype_alnum($value) || empty($value) )
			return $value;
		else
			return $this->RemoveXSS($value);
	}

	/* RemoveXSS initially developped by kallahar - quickwired.com, modified for Tiki
	 * Original code could be found here:
	 * http://quickwired.com/smallprojects/php_xss_filter_function.php
	 */
	function RemoveXSS($val)
	{
		static $ra_as_tag_only = NULL;
		static $ra_as_attribute = NULL;
		static $ra_as_content = NULL;
		static $ra_javascript = NULL;

		// now the only remaining whitespace attacks are \t, \n, and \r
		if ( $ra_as_tag_only == NULL ) {
			$ra_as_tag_only = array(
					'style',
					'script',
					'embed',
					'object',
					'applet',
					'meta',
					'iframe',
					'frame',
					'frameset',
					'ilayer',
					'layer',
					'bgsound',
					'base',
					'xml',
					'import',
					'link'
			);

			$ra_as_attribute = array(
					'onabort',
					'onactivate',
					'onafterprint',
					'onafterupdate',
					'onbeforeactivate',
					'onbeforecopy',
					'onbeforecut',
					'onbeforedeactivate',
					'onbeforeeditfocus',
					'onbeforepaste',
					'onbeforeprint',
					'onbeforeunload',
					'onbeforeupdate',
					'onblur',
					'onbounce',
					'oncellchange',
					'onchange',
					'onclick',
					'oncontextmenu',
					'oncontrolselect',
					'oncopy',
					'oncut',
					'ondataavailable',
					'ondatasetchanged',
					'ondatasetcomplete',
					'ondblclick',
					'ondeactivate',
					'ondrag',
					'ondragend',
					'ondragenter',
					'ondragleave',
					'ondragover',
					'ondragstart',
					'ondrop',
					'onerror',
					'onerrorupdate',
					'onfilterchange',
					'onfinish',
					'onfocus',
					'onfocusin',
					'onfocusout',
					'onhelp',
					'oninput',
					'onkeydown',
					'onkeypress',
					'onkeyup',
					'onlayoutcomplete',
					'onload',
					'onlosecapture',
					'onmousedown',
					'onmouseenter',
					'onmouseleave',
					'onmousemove',
					'onmouseout',
					'onmouseover',
					'onmouseup',
					'onmousewheel',
					'onmove',
					'onmoveend',
					'onmovestart',
					'onpaste',
					'onpropertychange',
					'onreadystatechange',
					'onreset',
					'onresize',
					'onresizeend',
					'onresizestart',
					'onrowenter',
					'onrowexit',
					'onrowsdelete',
					'onrowsinserted',
					'onscroll',
					'onselect',
					'onselectionchange',
					'onselectstart',
					'onstart',
					'onstop',
					'onsubmit',
					'onunload',
					'ondragdrop',
					'dynsrc',
					'lowsrc',
					'codebase',
					'xmlns'
			);

			$ra_as_content = array('vbscript', 'expression', 'blink', 'mocha', 'livescript', 'url', 'alert');
			$ra_javascript = array('javascript');
	///		$ra_style = array('style'); // Commented as it has been considered as a bit too aggressive
		}

		// keep replacing as long as the previous round replaced something
		while ( $this->RemoveXSSchars($val)
			|| $this->RemoveXSSregexp($ra_as_tag_only, $val, '(\<|\[\\\\xC0\]\[\\\\xBC\])\??')
			|| $this->RemoveXSSregexp($ra_as_attribute, $val)
			|| $this->RemoveXSSregexp($ra_as_content, $val, '[\.\\\\+\*\?\[\^\]\$\(\)\{\}\=\!\<\|\:;\-\/`#"\']', '(?!\s*[a-z0-9])', true)
			|| $this->RemoveXSSregexp($ra_javascript, $val, '', ':', true)
	///		|| RemoveXSSregexp($ra_style, $val, '[^a-z0-9]', '=') // Commented as it has been considered as a bit too aggressive
		);

		return $val;
	}

	function RemoveXSSchars(&$val)
	{
		static $patterns = NULL;
		static $replacements = NULL;
		$val_before = $val;
		$found = true;

		if ( $patterns == NULL ) {
			$patterns = array();
			$replacements = array();

			// remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are
			// allowed this prevents some character re-spacing such as <java\0script>
			// note that you have to handle splits with \n, \r, and \t later since they
			// *are* allowed in some inputs
			$patterns[] = '/([\x00-\x08\x0b-\x0c\x0e-\x19])/';
			$replacements[] = '';

			// straight replacements, the user should never need these since they're
			// normal characters this prevents like
			// <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&#X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
			// Calculate the search and replace patterns only once
			$search = 'abcdefghijklmnopqrstuvwxyz';
			$search .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
			$search .= '1234567890!@#$%^&*()';
			$search .= '~`";:?+/={}[]-_|\'\\';
			for ($i = 0, $istrlen_search = strlen($search); $i < $istrlen_search; $i++) {
				// ;? matches the ;, which is optional
				// 0{0,8} matches any padded zeros,
				// which are optional and go up to 8 chars
				// &#x0040 @ search for the hex values
				$patterns[] = '/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i';
				$replacements[] = $search[$i];
				// &#00064 @ 0{0,8} matches '0' zero to eight times
				// with a ;
				$patterns[] = '/(&#0{0,8}'.ord($search[$i]).';?)/';
				$replacements[] = $search[$i];
			}
		}
		$val = preg_replace($patterns, $replacements, $val);
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}
		return $found;
	}

	function RemoveXSSregexp(&$ra, &$val, $prefix = '', $suffix = '', $allow_spaces = false)
	{
		$val_before = $val;
		$found = true;
		$patterns = array();
		$replacements = array();

		$pattern_sep = '('
			.'&#[xX]0{0,8}[9ab];?'
			.'|&#0{0,8}(9|10|13);?'
			.'|(?ms)(\/\*.*?\*\/|\<\!\-\-.*?\-\-\>)'
			.'|(\<\!\[CDATA\[|\]\]\>)'
			.'|\\\\?'
			.( $allow_spaces ? '|\s' : '' )
		.')*';

		$pattern_start = '/';
		if ( $prefix != '' ) {
			$pattern_start .= '(' . $prefix . '\s*' . $pattern_sep . ')';
		}

		$pattern_end = '/i';
		if ( $suffix != '' ) {
			if ( $suffix == '=' || $suffix == ':' ) {
				$replacement_end = $suffix;
				$pattern_end = '(' . $pattern_sep . '\s*' . $suffix . ')' . $pattern_end;
			} else {
				$replacement_end = '';
				$pattern_end = $suffix . $pattern_end;
			}
		} else {
			$replacement_end = '';
		}

		for ($i = 0, $isizeof_ra = count($ra); $i < $isizeof_ra; $i++) {
			$pattern = $pattern_start;
			for ($j = 0, $jstrlen_rai = strlen($ra[$i]); $j < $jstrlen_rai; $j++) {
				if ($j > 0) {
					$pattern .= $pattern_sep;
				}
				$pattern .= $ra[$i][$j];
			}
			$pattern .= $pattern_end;
			$replacement = ( $prefix != '' ) ? '\\1' : '';
			// add in <> to nerf the tag
			$replacement .= substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2);
			$patterns[] = $pattern;
			$replacements[] = $replacement.$replacement_end;
		}
		// filter out the hex tags
		$val = preg_replace($patterns, $replacements, $val);

		if ($val === null) {
			TikiLib::lib('errorreport')->report(tr('Filter error: "%0"', array_flip(get_defined_constants(true)['pcre'])[preg_last_error()]));
		}
		if ($val_before == $val) {
			// no replacements were made, so exit the loop
			$found = false;
		}

		return $found;
	}
}
