diff options
Diffstat (limited to 'program/lib')
| -rw-r--r-- | program/lib/washtml.php | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/program/lib/washtml.php b/program/lib/washtml.php new file mode 100644 index 000000000..82ccc0cd5 --- /dev/null +++ b/program/lib/washtml.php @@ -0,0 +1,196 @@ +<?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: + * + * washtml::wash($html, $config, $full); + * 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. + * $full is a reference to a boolean that is set to true if no remote images are removed. (FE: show remote images link) + * + * INTERNALS: + * + * Only tags and attributes in the globals $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" />' + * - ... + */ + +class washtml +{ + + /* Allowed HTML elements */ + 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', 'ol', 'p', 'pre', 'q', 's', 'samp', 'small', 'span', 'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'title', 'tr', 'tt', 'u', 'ul', 'var', 'img'); + + /* Allowed HTML attributes */ + static $html_attribs = array('name', 'class', 'title', 'alt', 'width', 'height', 'align', 'nowrap', 'col', 'row', 'id', 'rowspan', 'colspan', 'cellspacing', 'cellpadding', 'valign', 'bgcolor', 'color', 'border', 'bordercolorlight', 'bordercolordark', 'face', 'marginwidth', 'marginheight', 'axis', 'border', 'abbr', 'char', 'charoff', 'clear', 'compact', 'coords', 'vspace', 'hspace', 'cellborder', 'size', 'lang', 'dir'); + + /* Check CSS style */ + static function wash_style($style, $config, &$full) { + $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(preg_match('/^(http|https|ftp):.*$/i', $match[2], $url)) { + if($config['allow_remote']) + $value .= ' url(\''.htmlspecialchars($url[0], ENT_QUOTES).'\')'; + else + $full = false; + } else if(preg_match('/^cid:(.*)$/i', $match[2], $cid)) + $value .= ' url(\''.htmlspecialchars($config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '\')'; + } else if($match[0] != 'url' && $match[0] != 'rbg')//whitelist ? + $value .= ' ' . $match[0]; + $str = substr($str, strlen($match[0])); + } + if($value) + $s .= ($s?' ':'') . $cssid . ':' . $value . ';'; + } + } + return $s; + } + + /* Take a node and return allowed attributes and check values */ + static function wash_attribs($node, $config, &$full) { + $t = ''; + $washed; + + foreach($node->attributes as $key => $plop) { + $key = strtolower($key); + $value = $node->getAttribute($key); + if((in_array($key, self::$html_attribs)) || + ($key == 'href' && preg_match('/^(http|https|ftp|mailto):.*/i', $value))) + $t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"'; + else if($key == 'style' && ($style = self::wash_style($value, $config, $full))) + $t .= ' style="' . $style . '"'; + else if($key == 'src' && strtolower($node->tagName) == 'img') { //check tagName anyway + if(preg_match('/^(http|https|ftp):.*/i', $value)) { + if($config['allow_remote']) + $t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"'; + else { + $full = false; + if ($config['blocked_src']) + $t .= ' src="' . htmlspecialchars($config['blocked_src'], ENT_QUOTES) . '"'; + } + } else if(preg_match('/^cid:(.*)$/i', $value, $cid)) + $t .= ' ' . $key . '="' . htmlspecialchars($config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '"'; + } else + $washed .= ($washed?' ':'') . $key; + } + return $t . ($washed && $config['show_washed']?' x-washed="'.$washed.'"':''); + } + + /* The main loop that recurse on a node tree. + * It output only allowed tags with allowed attributes + * and allowed inline styles */ + static function dumpHtml($node, $config, &$full) { + if(!$node->hasChildNodes()) + return ''; + + $node = $node->firstChild; + $dump = ''; + + do { + switch($node->nodeType) { + case XML_ELEMENT_NODE: //Check element + $tagName = strtolower($node->tagName); + if(in_array($tagName, self::$html_elements)) { + $content = self::dumpHtml($node, $config, $full); + $dump .= '<' . $tagName . self::wash_attribs($node, $config, $full) . + ($content?">$content</$tagName>":' />'); + } else if($tagName == 'html' || $tagName == 'body') { + $dump .= self::dumpHtml($node, $config, $full); //Just ignored + } else + $dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' not allowed -->'; + break; + case XML_TEXT_NODE: + $dump .= htmlspecialchars($node->nodeValue); + break; + case XML_HTML_DOCUMENT_NODE: + $dump .= self::dumpHtml($node, $config, $full); + break; + case XML_DOCUMENT_TYPE_NODE: break; + default: + } + } while($node = $node->nextSibling); + + return $dump; + } + + /* Main function, give it untrusted HTML, tell it if you allow loading + * remote images and give it a map to convert "cid:" urls. */ + static function wash($html, $config=array(), &$full=true) { + $config += array('show_washed'=>true, 'allow_remote'=>false, 'cid_map'=>array()); + //Charset seems to be ignored (probably if defined in the HTML document) + $node = new DOMDocument('1.0', $config['charset']); + $full = true; + @$node->loadHTML($html); + return self::dumpHtml($node, $config, $full); + } + +} + +?>
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