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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',
'video', 'source',
// 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)
{
$result = array();
foreach (explode(';', $style) as $declaration) {
if (preg_match('/^\s*([a-z\-]+)\s*:\s*(.*)\s*$/i', $declaration, $match)) {
$cssid = $match[1];
$str = $match[2];
$value = '';
foreach ($this->explode_style($str) as $val) {
if (preg_match('/^url\(/i', $val)) {
if (preg_match('/^url\(\s*[\'"]?([^\'"\)]*)[\'"]?\s*\)/iu', $val, $match)) {
$url = $match[1];
if (($src = $this->config['cid_map'][$url])
|| ($src = $this->config['cid_map'][$this->config['base_url'].$url])
) {
$value .= ' url('.htmlspecialchars($src, ENT_QUOTES) . ')';
}
else if (preg_match('!^(https?:)?//[a-z0-9/._+-]+$!i', $url, $m)) {
if ($this->config['allow_remote']) {
$value .= ' url('.htmlspecialchars($m[0], ENT_QUOTES).')';
}
else {
$this->extlinks = true;
}
}
else if (preg_match('/^data:.+/i', $url)) { // RFC2397
$value .= ' url('.htmlspecialchars($url, ENT_QUOTES).')';
}
}
}
else if (!preg_match('/^(behavior|expression)/i', $val)) {
// whitelist ?
$value .= ' ' . $val;
// #1488535: Fix size units, so width:800 would be changed to width:800px
if (preg_match('/^(left|right|top|bottom|width|height)/i', $cssid)
&& preg_match('/^[0-9]+$/', $val)
) {
$value .= 'px';
}
}
}
if (isset($value[0])) {
$result[] = $cssid . ':' . $value;
}
}
}
return implode('; ', $result);
}
/**
* Take a node and return allowed attributes and check values
*/
private function wash_attribs($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))) {
// replace double quotes to prevent syntax error and XSS issues (#1490227)
$t .= ' style="' . str_replace('"', '&quot;', $style) . '"';
}
else if ($key == 'background'
|| ($key == 'src' && preg_match('/^(img|source)$/i', $node->tagName))
|| ($key == 'poster' && strtolower($node->tagName) == 'video')
) {
if (($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
*
* @param DOMNode $node HTML element
* @param int $level Recurrence level (safe initial value found empirically)
*/
private function dumpHtml($node, $level = 20)
{
if (!$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)
$this->max_nesting_level = (int) @ini_get('xdebug.max_nesting_level');
// Use optimizations if supported
if (PHP_VERSION_ID >= 50400) {
@$node->loadHTML($html, LIBXML_PARSEHUGE | LIBXML_COMPACT);
}
else {
@$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(
// space(s) between <NOBR>
'/(<\/nobr>)(\s+)(<nobr>)/i',
// PHP bug #32547 workaround: remove title tag
'/<title[^>]*>[^<]*<\/title>/i',
// remove <!doctype> before BOM (#1490291)
'/<\!doctype[^>]+>[^<]*/im',
// byte-order mark (only outlook?)
'/^(\0\0\xFE\xFF|\xFF\xFE\0\0|\xFE\xFF|\xFF\xFE|\xEF\xBB\xBF)/',
// washtml/DOMDocument cannot handle xml namespaces
'/<html\s[^>]+>/i',
);
$html_replace = array(
'\\1'.' &nbsp; '.'\\3',
'',
'',
'',
'<html>',
);
$html = preg_replace($html_search, $html_replace, trim($html));
//-> Replace all of those weird MS Word quotes and other high characters
$badwordchars = array(
"\xe2\x80\x98", // left single quote
"\xe2\x80\x99", // right single quote
"\xe2\x80\x9c", // left double quote
"\xe2\x80\x9d", // right double quote
"\xe2\x80\x94", // em dash
"\xe2\x80\xa6" // elipses
);
$fixedwordchars = array(
"'",
"'",
'"',
'"',
'&mdash;',
'...'
);
$html = str_replace($badwordchars, $fixedwordchars, $html);
// PCRE errors handling (#1486856), should we use something like for every preg_* use?
if ($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]+>/', '', $html);
// fix broken nested lists
self::fix_broken_lists($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
), '', $tagname);
// fix invalid closing tags - remove any attributes (#1489446)
if ($matches[1] == '</') {
$matches[3] = '';
}
return $matches[1] . $tagname . $matches[3];
}
/**
* Convert all relative URLs according to a <base> in HTML
*/
public static function resolve_base($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 $body;
}
/**
* Fix broken nested lists, they are not handled properly by DOMDocument (#1488768)
*/
public static function fix_broken_lists(&$html)
{
// do two rounds, one for <ol>, one for <ul>
foreach (array('ol', 'ul') as $tag) {
$pos = 0;
while (($pos = stripos($html, '<' . $tag, $pos)) !== false) {
$pos++;
// make sure this is an ol/ul tag
if (!in_array($html[$pos+2], array(' ', '>'))) {
continue;
}
$p = $pos;
$in_li = false;
$li_pos = 0;
while (($p = strpos($html, '<', $p)) !== false) {
$tt = strtolower(substr($html, $p, 4));
// li open tag
if ($tt == '<li>' || $tt == '<li ') {
$in_li = true;
$p += 4;
}
// li close tag
else if ($tt == '</li' && in_array($html[$p+4], array(' ', '>'))) {
$li_pos = $p;
$p += 4;
$in_li = false;
}
// ul/ol closing tag
else if ($tt == '</' . $tag && in_array($html[$p+4], array(' ', '>'))) {
break;
}
// nested ol/ul element out of li
else if (!$in_li && $li_pos && ($tt == '<ol>' || $tt == '<ol ' || $tt == '<ul>' || $tt == '<ul ')) {
// find closing tag of this ul/ol element
$element = substr($tt, 1, 2);
$cpos = $p;
do {
$tpos = stripos($html, '<' . $element, $cpos+1);
$cpos = stripos($html, '</' . $element, $cpos+1);
}
while ($tpos !== false && $cpos !== false && $cpos > $tpos);
// not found, this is invalid HTML, skip it
if ($cpos === false) {
break;
}
// get element content
$end = strpos($html, '>', $cpos);
$len = $end - $p + 1;
$element = substr($html, $p, $len);
// move element to the end of the last li
$html = substr_replace($html, '', $p, $len);
$html = substr_replace($html, $element, $li_pos, 0);
$p = $end;
}
else {
$p++;
}
}
}
}
}
/**
* Explode css style value
*/
protected function explode_style($style)
{
$style = trim($style);
// first remove comments
$pos = 0;
while (($pos = strpos($style, '/*', $pos)) !== false) {
$end = strpos($style, '*/', $pos+2);
if ($end === false) {
$style = substr($style, 0, $pos);
}
else {
$style = substr_replace($style, '', $pos, $end - $pos + 2);
}
}
$strlen = strlen($style);
$result = array();
// explode value
for ($p=$i=0; $i < $strlen; $i++) {
if (($style[$i] == "\"" || $style[$i] == "'") && $style[$i-1] != "\\") {
if ($q == $style[$i]) {
$q = false;
}
else if (!$q) {
$q = $style[$i];
}
}
if (!$q && $style[$i] == ' ' && !preg_match('/[,\(]/', $style[$i-1])) {
$result[] = substr($style, $p, $i - $p);
$p = $i + 1;
}
}
$result[] = (string) substr($style, $p);
return $result;
}
}

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