<?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' ); /* 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 $_html_attribs = array(); /** * Class constructor */ public function __construct($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); $this->_block_elements = array_flip((array)$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]) || ($key == 'href' && ($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($node) { if (!$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; $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 { $this->config['base_url'] = ''; } @$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'.' '.'\\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 $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; } }