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rcube_washtml.php
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<?php
/**
+-----------------------------------------------------------------------+
| This file is part of the Roundcube Webmail client |
| Copyright (C) 2008-2012, The Roundcube Dev Team |
| |
| Licensed under the GNU General Public License version 3 or |
| any later version with exceptions for skins & plugins. |
| See the README file for a full license statement. |
| |
| PURPOSE: |
| Utility class providing HTML sanityzer (based on Washtml class) |
+-----------------------------------------------------------------------+
| Author: Thomas Bruederli <roundcube@gmail.com> |
| Author: Aleksander Machniak <alec@alec.pl> |
| Author: Frederic Motte <fmotte@ubixis.com> |
+-----------------------------------------------------------------------+
*/
/**
* Washtml, a HTML sanityzer.
*
* Copyright (c) 2007 Frederic Motte <fmotte@ubixis.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* OVERVIEW:
*
* Wahstml take an untrusted HTML and return a safe html string.
*
* SYNOPSIS:
*
* $washer = new washtml($config);
* $washer->wash($html);
* It return a sanityzed string of the $html parameter without html and head tags.
* $html is a string containing the html code to wash.
* $config is an array containing options:
* $config['allow_remote'] is a boolean to allow link to remote images.
* $config['blocked_src'] string with image-src to be used for blocked remote images
* $config['show_washed'] is a boolean to include washed out attributes as x-washed
* $config['cid_map'] is an array where cid urls index urls to replace them.
* $config['charset'] is a string containing the charset of the HTML document if it is not defined in it.
* $washer->extlinks is a reference to a boolean that is set to true if remote images were removed. (FE: show remote images link)
*
* INTERNALS:
*
* Only tags and attributes in the static lists $html_elements and $html_attributes
* are kept, inline styles are also filtered: all style identifiers matching
* /[a-z\-]/i are allowed. Values matching colors, sizes, /[a-z\-]/i and safe
* urls if allowed and cid urls if mapped are kept.
*
* Roundcube Changes:
* - added $block_elements
* - changed $ignore_elements behaviour
* - added RFC2397 support
* - base URL support
* - invalid HTML comments removal before parsing
* - "fixing" unitless CSS values for XHTML output
* - base url resolving
*/
/**
* Utility class providing HTML sanityzer
*
* @package Framework
* @subpackage Utils
*/
class rcube_washtml
{
/* Allowed HTML elements (default) */
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',
// form elements
'button', 'input', 'textarea', 'select', 'option', 'optgroup'
);
/* Ignore these HTML tags and their content */
static $ignore_elements = array('script', 'applet', 'embed', 'object', 'style');
/* Allowed HTML attributes */
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', 'usemap', 'shape', 'media',
// attributes of form elements
'type', 'rows', 'cols', 'disabled', 'readonly', 'checked', 'multiple', 'value'
);
/* Elements which could be empty and be returned in short form (<tag />) */
static $void_elements = array('area', 'base', 'br', 'col', 'command', 'embed', 'hr',
'img', 'input', 'keygen', 'link', 'meta', 'param', 'source', 'track', 'wbr'
);
/* State for linked objects in HTML */
public $extlinks = false;
/* Current settings */
private $config = array();
/* Registered callback functions for tags */
private $handlers = array();
/* Allowed HTML elements */
private $_html_elements = array();
/* Ignore these HTML tags but process their content */
private $_ignore_elements = array();
/* Elements which could be empty and be returned in short form (<tag />) */
private $_void_elements = array();
/* Allowed HTML attributes */
private $_html_attribs = array();
/* Max nesting level */
private $max_nesting_level;
/**
* Class constructor
*/
public function __construct($p = array())
{
$this->_html_elements = array_flip((array)$p['html_elements']) + array_flip(self::$html_elements) ;
$this->_html_attribs = array_flip((array)$p['html_attribs']) + array_flip(self::$html_attribs);
$this->_ignore_elements = array_flip((array)$p['ignore_elements']) + array_flip(self::$ignore_elements);
$this->_void_elements = array_flip((array)$p['void_elements']) + array_flip(self::$void_elements);
unset($p['html_elements'], $p['html_attribs'], $p['ignore_elements'], $p['void_elements']);
$this->config = $p + array('show_washed' => true, 'allow_remote' => false, 'cid_map' => array());
}
/**
* Register a callback function for a certain tag
*/
public function add_callback($tagName, $callback)
{
$this->handlers[$tagName] = $callback;
}
/**
* Check CSS style
*/
private function wash_style($style)
{
$s = '';
foreach (explode(';', $style) as $declaration) {
if (preg_match('/^\s*([a-z\-]+)\s*:\s*(.*)\s*$/i', $declaration, $match)) {
$cssid = $match[1];
$str = $match[2];
$value = '';
while (sizeof($str) > 0 &&
preg_match('/^(url\(\s*[\'"]?([^\'"\)]*)[\'"]?\s*\)'./*1,2*/
'|rgb\(\s*[0-9]+\s*,\s*[0-9]+\s*,\s*[0-9]+\s*\)'.
'|-?[0-9.]+\s*(em|ex|px|cm|mm|in|pt|pc|deg|rad|grad|ms|s|hz|khz|%)?'.
'|#[0-9a-f]{3,6}'.
'|[a-z0-9", -]+'.
')\s*/i', $str, $match)
) {
if ($match[2]) {
if (($src = $this->config['cid_map'][$match[2]])
|| ($src = $this->config['cid_map'][$this->config['base_url'].$match[2]])
) {
$value .= ' url('.htmlspecialchars($src, ENT_QUOTES) . ')';
}
else if (preg_match('!^(https?:)?//[a-z0-9/._+-]+$!i', $match[2], $url)) {
if ($this->config['allow_remote']) {
$value .= ' url('.htmlspecialchars($url[0], ENT_QUOTES).')';
}
else {
$this->extlinks = true;
}
}
else if (preg_match('/^data:.+/i', $match[2])) { // RFC2397
$value .= ' url('.htmlspecialchars($match[2], ENT_QUOTES).')';
}
}
else {
// whitelist ?
$value .= ' ' . $match[0];
// #1488535: Fix size units, so width:800 would be changed to width:800px
if (preg_match('/(left|right|top|bottom|width|height)/i', $cssid)
&& preg_match('/^[0-9]+$/', $match[0])
) {
$value .= 'px';
}
}
$str = substr($str, strlen($match[0]));
}
if (isset($value[0])) {
$s .= ($s?' ':'') . $cssid . ':' . $value . ';';
}
}
}
return $s;
}
/**
* Take a node and return allowed attributes and check values
*/
private function wash_attribs($node)
{
$t = '';
$washed = '';
foreach ($node->attributes as $key => $plop) {
$key = strtolower($key);
$value = $node->getAttribute($key);
if (isset($this->_html_attribs[$key]) ||
($key == 'href' && ($value = trim($value))
&& !preg_match('!^(javascript|vbscript|data:text)!i', $value)
&& preg_match('!^([a-z][a-z0-9.+-]+:|//|#).+!i', $value))
) {
$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
}
else if ($key == 'style' && ($style = $this->wash_style($value))) {
$quot = strpos($style, '"') !== false ? "'" : '"';
$t .= ' style=' . $quot . $style . $quot;
}
else if ($key == 'background' || ($key == 'src' && strtolower($node->tagName) == 'img')) { //check tagName anyway
if (($src = $this->config['cid_map'][$value])
|| ($src = $this->config['cid_map'][$this->config['base_url'].$value])
) {
$t .= ' ' . $key . '="' . htmlspecialchars($src, ENT_QUOTES) . '"';
}
else if (preg_match('/^(http|https|ftp):.+/i', $value)) {
if ($this->config['allow_remote']) {
$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
}
else {
$this->extlinks = true;
if ($this->config['blocked_src']) {
$t .= ' ' . $key . '="' . htmlspecialchars($this->config['blocked_src'], ENT_QUOTES) . '"';
}
}
}
else if (preg_match('/^data:.+/i', $value)) { // RFC2397
$t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
}
}
else {
$washed .= ($washed ? ' ' : '') . $key;
}
}
return $t . ($washed && $this->config['show_washed'] ? ' x-washed="'.$washed.'"' : '');
}
/**
* The main loop that recurse on a node tree.
* It output only allowed tags with allowed attributes
* and allowed inline styles
*/
private function dumpHtml($node, $level = 0)
{
if (!$node->hasChildNodes()) {
return '';
}
$level++;
if ($this->max_nesting_level > 0 && $level == $this->max_nesting_level - 1) {
// log error message once
if (!$this->max_nesting_level_error) {
$this->max_nesting_level_error = true;
rcube::raise_error(array('code' => 500, 'type' => 'php',
'line' => __LINE__, 'file' => __FILE__,
'message' => "Maximum nesting level exceeded (xdebug.max_nesting_level={$this->max_nesting_level})"),
true, false);
}
return '<!-- ignored -->';
}
$node = $node->firstChild;
$dump = '';
do {
switch($node->nodeType) {
case XML_ELEMENT_NODE: //Check element
$tagName = strtolower($node->tagName);
if ($callback = $this->handlers[$tagName]) {
$dump .= call_user_func($callback, $tagName,
$this->wash_attribs($node), $this->dumpHtml($node, $level), $this);
}
else if (isset($this->_html_elements[$tagName])) {
$content = $this->dumpHtml($node, $level);
$dump .= '<' . $tagName . $this->wash_attribs($node) .
($content === '' && isset($this->_void_elements[$tagName]) ? ' />' : ">$content</$tagName>");
}
else if (isset($this->_ignore_elements[$tagName])) {
$dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' not allowed -->';
}
else {
$dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' ignored -->';
$dump .= $this->dumpHtml($node, $level); // ignore tags not its content
}
break;
case XML_CDATA_SECTION_NODE:
$dump .= $node->nodeValue;
break;
case XML_TEXT_NODE:
$dump .= htmlspecialchars($node->nodeValue);
break;
case XML_HTML_DOCUMENT_NODE:
$dump .= $this->dumpHtml($node, $level);
break;
case XML_DOCUMENT_TYPE_NODE:
break;
default:
$dump .= '<!-- node type ' . $node->nodeType . ' -->';
}
} while($node = $node->nextSibling);
return $dump;
}
/**
* Main function, give it untrusted HTML, tell it if you allow loading
* remote images and give it a map to convert "cid:" urls.
*/
public function wash($html)
{
// Charset seems to be ignored (probably if defined in the HTML document)
$node = new DOMDocument('1.0', $this->config['charset']);
$this->extlinks = false;
$html = $this->cleanup($html);
// Find base URL for images
if (preg_match('/<base\s+href=[\'"]*([^\'"]+)/is', $html, $matches)) {
$this->config['base_url'] = $matches[1];
}
else {
$this->config['base_url'] = '';
}
// Detect max nesting level (for dumpHTML) (#1489110)
$this->max_nesting_level = (int) @ini_get('xdebug.max_nesting_level');
@$node->loadHTML($html);
return $this->dumpHtml($node);
}
/**
* Getter for config parameters
*/
public function get_config($prop)
{
return $this->config[$prop];
}
/**
* Clean HTML input
*/
private function cleanup($html)
{
// special replacements (not properly handled by washtml class)
$html_search = array(
'/(<\/nobr>)(\s+)(<nobr>)/i', // space(s) between <NOBR>
'/<title[^>]*>[^<]*<\/title>/i', // PHP bug #32547 workaround: remove title tag
'/^(\0\0\xFE\xFF|\xFF\xFE\0\0|\xFE\xFF|\xFF\xFE|\xEF\xBB\xBF)/', // byte-order mark (only outlook?)
'/<html\s[^>]+>/i', // washtml/DOMDocument cannot handle xml namespaces
);
$html_replace = array(
'\\1'.' &nbsp; '.'\\3',
'',
'',
'<html>',
);
$html = preg_replace($html_search, $html_replace, trim($html));
// PCRE errors handling (#1486856), should we use something like for every preg_* use?
if ($html === null && ($preg_error = preg_last_error()) != PREG_NO_ERROR) {
$errstr = "Could not clean up HTML message! PCRE Error: $preg_error.";
if ($preg_error == PREG_BACKTRACK_LIMIT_ERROR) {
$errstr .= " Consider raising pcre.backtrack_limit!";
}
if ($preg_error == PREG_RECURSION_LIMIT_ERROR) {
$errstr .= " Consider raising pcre.recursion_limit!";
}
rcube::raise_error(array('code' => 620, 'type' => 'php',
'line' => __LINE__, 'file' => __FILE__,
'message' => $errstr), true, false);
return '';
}
// fix (unknown/malformed) HTML tags before "wash"
$html = preg_replace_callback('/(<[\/]*)([^\s>]+)/', array($this, 'html_tag_callback'), $html);
// Remove invalid HTML comments (#1487759)
// Don't remove valid conditional comments
// Don't remove MSOutlook (<!-->) conditional comments (#1489004)
$html = preg_replace('/<!--[^->\[\n]+>/', '', $html);
// turn relative into absolute urls
$html = self::resolve_base($html);
return $html;
}
/**
* Callback function for HTML tags fixing
*/
public static function html_tag_callback($matches)
{
$tagname = $matches[2];
$tagname = preg_replace(array(
'/:.*$/', // Microsoft's Smart Tags <st1:xxxx>
'/[^a-z0-9_\[\]\!-]/i', // forbidden characters
), '', $tagname);
return $matches[1] . $tagname;
}
/**
* Convert all relative URLs according to a <base> in HTML
*/
public static function resolve_base($body)
{
// check for <base href=...>
if (preg_match('!(<base.*href=["\']?)([hftps]{3,5}://[a-z0-9/.%-]+)!i', $body, $regs)) {
$replacer = new rcube_base_replacer($regs[2]);
$body = $replacer->replace($body);
}
return $body;
}
}

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