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286 lines
12 KiB
PHP
286 lines
12 KiB
PHP
<?php
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/* Washtml, a HTML sanityzer.
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*
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* Copyright (c) 2007 Frederic Motte <fmotte@ubixis.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/* Please send me your comments about this code if you have some, thanks, Fred. */
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/* OVERVIEW:
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*
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* Wahstml take an untrusted HTML and return a safe html string.
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*
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* SYNOPSIS:
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*
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* $washer = new washtml($config);
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* $washer->wash($html);
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* It return a sanityzed string of the $html parameter without html and head tags.
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* $html is a string containing the html code to wash.
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* $config is an array containing options:
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* $config['allow_remote'] is a boolean to allow link to remote images.
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* $config['blocked_src'] string with image-src to be used for blocked remote images
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* $config['show_washed'] is a boolean to include washed out attributes as x-washed
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* $config['cid_map'] is an array where cid urls index urls to replace them.
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* $config['charset'] is a string containing the charset of the HTML document if it is not defined in it.
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* $washer->extlinks is a reference to a boolean that is set to true if remote images were removed. (FE: show remote images link)
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*
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* INTERNALS:
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*
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* Only tags and attributes in the static lists $html_elements and $html_attributes
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* are kept, inline styles are also filtered: all style identifiers matching
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* /[a-z\-]/i are allowed. Values matching colors, sizes, /[a-z\-]/i and safe
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* urls if allowed and cid urls if mapped are kept.
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*
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* BUGS: It MUST be safe !
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* - Check regexp
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* - urlencode URLs instead of htmlspecials
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* - Check is a 3 bytes utf8 first char can eat '">'
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* - Update PCRE: CVE-2007-1659 - CVE-2007-1660 - CVE-2007-1661 - CVE-2007-1662
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* CVE-2007-4766 - CVE-2007-4767 - CVE-2007-4768
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* http://lists.debian.org/debian-security-announce/debian-security-announce-2007/msg00177.html
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* - ...
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*
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* MISSING:
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* - relative links, can be implemented by prefixing an absolute path, ask me
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* if you need it...
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* - ...
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*
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* Dont be a fool:
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* - Dont alter data on a GET: '<img src="http://yourhost/mail?action=delete&uid=3267" />'
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* - ...
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*
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* Roundcube Changes:
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* - added $block_elements
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* - changed $ignore_elements behaviour
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* - added RFC2397 support
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* - base URL support
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* - invalid HTML comments removal before parsing
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*/
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class washtml
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{
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/* Allowed HTML elements (default) */
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static $html_elements = array('a', 'abbr', 'acronym', 'address', 'area', 'b', 'basefont', 'bdo', 'big', 'blockquote', 'br', 'caption', 'center', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'dir', 'div', 'dl', 'dt', 'em', 'fieldset', 'font', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'ins', 'label', 'legend', 'li', 'map', 'menu', 'nobr', 'ol', 'p', 'pre', 'q', 's', 'samp', 'small', 'span', 'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'tr', 'tt', 'u', 'ul', 'var', 'wbr', 'img');
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/* Ignore these HTML tags and their content */
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static $ignore_elements = array('script', 'applet', 'embed', 'object', 'style');
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/* Allowed HTML attributes */
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static $html_attribs = array('name', 'class', 'title', 'alt', 'width', 'height', 'align', 'nowrap', 'col', 'row', 'id', 'rowspan', 'colspan', 'cellspacing', 'cellpadding', 'valign', 'bgcolor', 'color', 'border', 'bordercolorlight', 'bordercolordark', 'face', 'marginwidth', 'marginheight', 'axis', 'border', 'abbr', 'char', 'charoff', 'clear', 'compact', 'coords', 'vspace', 'hspace', 'cellborder', 'size', 'lang', 'dir');
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/* Block elements which could be empty but cannot be returned in short form (<tag />) */
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static $block_elements = array('div', 'p', 'pre', 'blockquote', 'a', 'font', 'center', 'table', 'ul', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'ol', 'dl', 'strong', 'i', 'b');
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/* State for linked objects in HTML */
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public $extlinks = false;
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/* Current settings */
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private $config = array();
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/* Registered callback functions for tags */
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private $handlers = array();
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/* Allowed HTML elements */
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private $_html_elements = array();
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/* Ignore these HTML tags but process their content */
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private $_ignore_elements = array();
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/* Block elements which could be empty but cannot be returned in short form (<tag />) */
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private $_block_elements = array();
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/* Allowed HTML attributes */
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private $_html_attribs = array();
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/* Constructor */
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public function __construct($p = array()) {
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$this->_html_elements = array_flip((array)$p['html_elements']) + array_flip(self::$html_elements) ;
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$this->_html_attribs = array_flip((array)$p['html_attribs']) + array_flip(self::$html_attribs);
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$this->_ignore_elements = array_flip((array)$p['ignore_elements']) + array_flip(self::$ignore_elements);
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$this->_block_elements = array_flip((array)$p['block_elements']) + array_flip(self::$block_elements);
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unset($p['html_elements'], $p['html_attribs'], $p['ignore_elements'], $p['block_elements']);
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$this->config = $p + array('show_washed'=>true, 'allow_remote'=>false, 'cid_map'=>array());
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}
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/* Register a callback function for a certain tag */
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public function add_callback($tagName, $callback)
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{
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$this->handlers[$tagName] = $callback;
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}
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/* Check CSS style */
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private function wash_style($style) {
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$s = '';
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foreach (explode(';', $style) as $declaration) {
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if (preg_match('/^\s*([a-z\-]+)\s*:\s*(.*)\s*$/i', $declaration, $match)) {
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$cssid = $match[1];
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$str = $match[2];
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$value = '';
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while (sizeof($str) > 0 &&
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preg_match('/^(url\(\s*[\'"]?([^\'"\)]*)[\'"]?\s*\)'./*1,2*/
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'|rgb\(\s*[0-9]+\s*,\s*[0-9]+\s*,\s*[0-9]+\s*\)'.
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'|-?[0-9.]+\s*(em|ex|px|cm|mm|in|pt|pc|deg|rad|grad|ms|s|hz|khz|%)?'.
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'|#[0-9a-f]{3,6}|[a-z0-9\-]+'.
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')\s*/i', $str, $match)) {
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if ($match[2]) {
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if (($src = $this->config['cid_map'][$match[2]])
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|| ($src = $this->config['cid_map'][$this->config['base_url'].$match[2]])) {
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$value .= ' url('.htmlspecialchars($src, ENT_QUOTES) . ')';
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}
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else if (preg_match('/^(http|https|ftp):.*$/i', $match[2], $url)) {
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if ($this->config['allow_remote'])
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$value .= ' url('.htmlspecialchars($url[0], ENT_QUOTES).')';
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else
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$this->extlinks = true;
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}
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else if (preg_match('/^data:.+/i', $match[2])) { // RFC2397
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$value .= ' url('.htmlspecialchars($match[2], ENT_QUOTES).')';
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}
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}
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else if ($match[0] != 'url' && $match[0] != 'rbg') //whitelist ?
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$value .= ' ' . $match[0];
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$str = substr($str, strlen($match[0]));
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}
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if ($value)
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$s .= ($s?' ':'') . $cssid . ':' . $value . ';';
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}
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}
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return $s;
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}
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/* Take a node and return allowed attributes and check values */
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private function wash_attribs($node) {
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$t = '';
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$washed;
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foreach ($node->attributes as $key => $plop) {
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$key = strtolower($key);
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$value = $node->getAttribute($key);
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if (isset($this->_html_attribs[$key]) ||
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($key == 'href' && preg_match('/^(http:|https:|ftp:|mailto:|#).+/i', $value)))
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$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
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else if ($key == 'style' && ($style = $this->wash_style($value)))
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$t .= ' style="' . $style . '"';
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else if ($key == 'background' || ($key == 'src' && strtolower($node->tagName) == 'img')) { //check tagName anyway
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if (($src = $this->config['cid_map'][$value])
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|| ($src = $this->config['cid_map'][$this->config['base_url'].$value])) {
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$t .= ' ' . $key . '="' . htmlspecialchars($src, ENT_QUOTES) . '"';
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}
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else if (preg_match('/^(http|https|ftp):.+/i', $value)) {
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if ($this->config['allow_remote'])
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$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
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else {
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$this->extlinks = true;
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if ($this->config['blocked_src'])
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$t .= ' ' . $key . '="' . htmlspecialchars($this->config['blocked_src'], ENT_QUOTES) . '"';
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}
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}
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else if (preg_match('/^data:.+/i', $value)) { // RFC2397
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$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
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}
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} else
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$washed .= ($washed?' ':'') . $key;
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}
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return $t . ($washed && $this->config['show_washed']?' x-washed="'.$washed.'"':'');
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}
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/* The main loop that recurse on a node tree.
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* It output only allowed tags with allowed attributes
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* and allowed inline styles */
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private function dumpHtml($node) {
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if(!$node->hasChildNodes())
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return '';
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$node = $node->firstChild;
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$dump = '';
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do {
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switch($node->nodeType) {
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case XML_ELEMENT_NODE: //Check element
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$tagName = strtolower($node->tagName);
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if ($callback = $this->handlers[$tagName]) {
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$dump .= call_user_func($callback, $tagName, $this->wash_attribs($node), $this->dumpHtml($node));
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}
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else if (isset($this->_html_elements[$tagName])) {
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$content = $this->dumpHtml($node);
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$dump .= '<' . $tagName . $this->wash_attribs($node) .
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// create closing tag for block elements, but also for elements
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// with content or with some attributes (eg. style, class) (#1486812)
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($content != '' || $node->hasAttributes() || isset($this->_block_elements[$tagName]) ? ">$content</$tagName>" : ' />');
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}
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else if (isset($this->_ignore_elements[$tagName])) {
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$dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' not allowed -->';
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}
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else {
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$dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' ignored -->';
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$dump .= $this->dumpHtml($node); // ignore tags not its content
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}
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break;
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case XML_CDATA_SECTION_NODE:
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$dump .= $node->nodeValue;
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break;
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case XML_TEXT_NODE:
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$dump .= htmlspecialchars($node->nodeValue);
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break;
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case XML_HTML_DOCUMENT_NODE:
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$dump .= $this->dumpHtml($node);
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break;
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case XML_DOCUMENT_TYPE_NODE:
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break;
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default:
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$dump . '<!-- node type ' . $node->nodeType . ' -->';
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}
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} while($node = $node->nextSibling);
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return $dump;
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}
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/* Main function, give it untrusted HTML, tell it if you allow loading
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* remote images and give it a map to convert "cid:" urls. */
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public function wash($html)
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{
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// Charset seems to be ignored (probably if defined in the HTML document)
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$node = new DOMDocument('1.0', $this->config['charset']);
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$this->extlinks = false;
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// Find base URL for images
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if (preg_match('/<base\s+href=[\'"]*([^\'"]+)/is', $html, $matches))
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$this->config['base_url'] = $matches[1];
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else
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$this->config['base_url'] = '';
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// Remove invalid HTML comments (#1487759)
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// Don't remove valid conditional comments
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$html = preg_replace('/<!--[^->[\n]*>/', '', $html);
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@$node->loadHTML($html);
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return $this->dumpHtml($node);
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}
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}
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?>
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