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-<?php
-/* 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.
- */
-
-/* Please send me your comments about this code if you have some, thanks, Fred. */
-
-/* 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.
- *
- * BUGS: It MUST be safe !
- * - Check regexp
- * - urlencode URLs instead of htmlspecials
- * - Check is a 3 bytes utf8 first char can eat '">'
- * - Update PCRE: CVE-2007-1659 - CVE-2007-1660 - CVE-2007-1661 - CVE-2007-1662
- * CVE-2007-4766 - CVE-2007-4767 - CVE-2007-4768
- * http://lists.debian.org/debian-security-announce/debian-security-announce-2007/msg00177.html
- * - ...
- *
- * MISSING:
- * - relative links, can be implemented by prefixing an absolute path, ask me
- * if you need it...
- * - ...
- *
- * Dont be a fool:
- * - Dont alter data on a GET: '<img src="http://yourhost/mail?action=delete&uid=3267" />'
- * - ...
- *
- * 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
- */
-
-class 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'
- );
-
- /* Block elements which could be empty but cannot be returned in short form (<tag />) */
- static $block_elements = array('div', 'p', 'pre', 'blockquote', 'a', 'font', 'center',
- 'table', 'ul', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'ol', 'dl', 'strong', 'i', 'b', 'u', 'span');
-
- /* 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();
-
- /* Block elements which could be empty but cannot be returned in short form (<tag />) */
- private $_block_elements = array();
-
- /* Allowed HTML attributes */
- private $_html_attribs = array();
-
-
- /* Constructor */
- public function __construct($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);
- $this->_block_elements = array_flip((array)$p['block_elements']) + array_flip(self::$block_elements);
- unset($p['html_elements'], $p['html_attribs'], $p['ignore_elements'], $p['block_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' && !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($node)
- {
- if(!$node->hasChildNodes())
- return '';
-
- $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), $this);
- }
- else if (isset($this->_html_elements[$tagName])) {
- $content = $this->dumpHtml($node);
- $dump .= '<' . $tagName . $this->wash_attribs($node) .
- ($content != '' || isset($this->_block_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); // 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);
- 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;
-
- // 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'] = '';
-
- // Remove invalid HTML comments (#1487759)
- // Don't remove valid conditional comments
- $html = preg_replace('/<!--[^->[\n]*>/', '', $html);
-
- @$node->loadHTML($html);
- return $this->dumpHtml($node);
- }
-
- /**
- * Getter for config parameters
- */
- public function get_config($prop)
- {
- return $this->config[$prop];
- }
-
-}
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