- Patch #470632 by sun: move filter_xss*() into common.inc.
Dries Buytaert
parent
adf7113451
commit
a5f42fd007
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@ -1256,6 +1256,12 @@ function check_file($filename) {
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return is_uploaded_file($filename);
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}
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/**
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* @defgroup sanitization Sanitization functions
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* @{
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* Functions to sanitize values.
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*/
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/**
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* Prepare a URL for use in an HTML attribute. Strips harmful protocols.
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*/
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@ -1263,6 +1269,291 @@ function check_url($uri) {
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return filter_xss_bad_protocol($uri, FALSE);
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}
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/**
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* Very permissive XSS/HTML filter for admin-only use.
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*
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* Use only for fields where it is impractical to use the
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* whole filter system, but where some (mainly inline) mark-up
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* is desired (so check_plain() is not acceptable).
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*
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* Allows all tags that can be used inside an HTML body, save
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* for scripts and styles.
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*/
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function filter_xss_admin($string) {
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return filter_xss($string, array('a', 'abbr', 'acronym', 'address', 'b', 'bdo', 'big', 'blockquote', 'br', 'caption', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'div', 'dl', 'dt', 'em', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'img', 'ins', 'kbd', 'li', 'ol', 'p', 'pre', 'q', 'samp', 'small', 'span', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'tr', 'tt', 'ul', 'var'));
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}
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/**
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* Filter XSS.
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*
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* Based on kses by Ulf Harnhammar, see
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* http://sourceforge.net/projects/kses
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*
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* For examples of various XSS attacks, see:
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* http://ha.ckers.org/xss.html
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*
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* This code does four things:
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* - Removes characters and constructs that can trick browsers
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* - Makes sure all HTML entities are well-formed
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* - Makes sure all HTML tags and attributes are well-formed
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* - Makes sure no HTML tags contain URLs with a disallowed protocol (e.g. javascript:)
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*
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* @param $string
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* The string with raw HTML in it. It will be stripped of everything that can cause
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* an XSS attack.
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* @param $allowed_tags
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* An array of allowed tags.
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*/
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function filter_xss($string, $allowed_tags = array('a', 'em', 'strong', 'cite', 'blockquote', 'code', 'ul', 'ol', 'li', 'dl', 'dt', 'dd')) {
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// Only operate on valid UTF-8 strings. This is necessary to prevent cross
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// site scripting issues on Internet Explorer 6.
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if (!drupal_validate_utf8($string)) {
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return '';
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}
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// Store the text format
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_filter_xss_split($allowed_tags, TRUE);
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// Remove NULL characters (ignored by some browsers)
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$string = str_replace(chr(0), '', $string);
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// Remove Netscape 4 JS entities
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$string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
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// Defuse all HTML entities
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$string = str_replace('&', '&', $string);
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// Change back only well-formed entities in our whitelist
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// Named entities
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$string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
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// Decimal numeric entities
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$string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
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// Hexadecimal numeric entities
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$string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
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return preg_replace_callback('%
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(
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<(?=[^a-zA-Z!/]) # a lone <
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| # or
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<[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string
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| # or
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> # just a >
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)%x', '_filter_xss_split', $string);
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}
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/**
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* Processes an HTML tag.
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*
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* @param $m
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* An array with various meaning depending on the value of $store.
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* If $store is TRUE then the array contains the allowed tags.
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* If $store is FALSE then the array has one element, the HTML tag to process.
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* @param $store
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* Whether to store $m.
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* @return
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* If the element isn't allowed, an empty string. Otherwise, the cleaned up
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* version of the HTML element.
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*/
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function _filter_xss_split($m, $store = FALSE) {
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static $allowed_html;
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if ($store) {
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$allowed_html = array_flip($m);
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return;
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}
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$string = $m[1];
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if (substr($string, 0, 1) != '<') {
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// We matched a lone ">" character
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return '>';
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}
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elseif (strlen($string) == 1) {
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// We matched a lone "<" character
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return '<';
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}
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if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches)) {
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// Seriously malformed
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return '';
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}
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$slash = trim($matches[1]);
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$elem = &$matches[2];
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$attrlist = &$matches[3];
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if (!isset($allowed_html[strtolower($elem)])) {
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// Disallowed HTML element
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return '';
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}
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if ($slash != '') {
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return "</$elem>";
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}
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// Is there a closing XHTML slash at the end of the attributes?
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$attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count);
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$xhtml_slash = $count ? ' /' : '';
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// Clean up attributes
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$attr2 = implode(' ', _filter_xss_attributes($attrlist));
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$attr2 = preg_replace('/[<>]/', '', $attr2);
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$attr2 = strlen($attr2) ? ' ' . $attr2 : '';
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return "<$elem$attr2$xhtml_slash>";
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}
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/**
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* Processes a string of HTML attributes.
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*
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* @return
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* Cleaned up version of the HTML attributes.
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*/
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function _filter_xss_attributes($attr) {
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$attrarr = array();
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$mode = 0;
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$attrname = '';
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while (strlen($attr) != 0) {
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// Was the last operation successful?
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$working = 0;
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switch ($mode) {
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case 0:
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// Attribute name, href for instance
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if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) {
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$attrname = strtolower($match[1]);
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$skip = ($attrname == 'style' || substr($attrname, 0, 2) == 'on');
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$working = $mode = 1;
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$attr = preg_replace('/^[-a-zA-Z]+/', '', $attr);
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}
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break;
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case 1:
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// Equals sign or valueless ("selected")
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if (preg_match('/^\s*=\s*/', $attr)) {
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$working = 1; $mode = 2;
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$attr = preg_replace('/^\s*=\s*/', '', $attr);
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break;
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}
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if (preg_match('/^\s+/', $attr)) {
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$working = 1; $mode = 0;
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if (!$skip) {
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$attrarr[] = $attrname;
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}
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$attr = preg_replace('/^\s+/', '', $attr);
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}
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break;
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case 2:
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// Attribute value, a URL after href= for instance
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if (preg_match('/^"([^"]*)"(\s+|$)/', $attr, $match)) {
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$thisval = filter_xss_bad_protocol($match[1]);
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if (!$skip) {
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$attrarr[] = "$attrname=\"$thisval\"";
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}
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$working = 1;
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$mode = 0;
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$attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr);
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break;
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}
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if (preg_match("/^'([^']*)'(\s+|$)/", $attr, $match)) {
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$thisval = filter_xss_bad_protocol($match[1]);
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if (!$skip) {
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$attrarr[] = "$attrname='$thisval'";
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}
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$working = 1; $mode = 0;
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$attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr);
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break;
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}
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if (preg_match("%^([^\s\"']+)(\s+|$)%", $attr, $match)) {
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$thisval = filter_xss_bad_protocol($match[1]);
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if (!$skip) {
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$attrarr[] = "$attrname=\"$thisval\"";
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}
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$working = 1; $mode = 0;
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$attr = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attr);
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}
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break;
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}
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if ($working == 0) {
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// not well formed, remove and try again
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$attr = preg_replace('/
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^
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(
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"[^"]*("|$) # - a string that starts with a double quote, up until the next double quote or the end of the string
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| # or
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\'[^\']*(\'|$)| # - a string that starts with a quote, up until the next quote or the end of the string
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| # or
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\S # - a non-whitespace character
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)* # any number of the above three
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\s* # any number of whitespaces
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/x', '', $attr);
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$mode = 0;
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}
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}
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// the attribute list ends with a valueless attribute like "selected"
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if ($mode == 1) {
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$attrarr[] = $attrname;
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}
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return $attrarr;
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}
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/**
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* Processes an HTML attribute value and ensures it does not contain an URL with a disallowed protocol (e.g. javascript:).
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*
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* @param $string
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* The string with the attribute value.
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* @param $decode
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* Whether to decode entities in the $string. Set to FALSE if the $string
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* is in plain text, TRUE otherwise. Defaults to TRUE.
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* @return
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* Cleaned up and HTML-escaped version of $string.
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*/
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function filter_xss_bad_protocol($string, $decode = TRUE) {
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static $allowed_protocols;
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if (!isset($allowed_protocols)) {
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$allowed_protocols = array_flip(variable_get('filter_allowed_protocols', array('ftp', 'http', 'https', 'irc', 'mailto', 'news', 'nntp', 'rtsp', 'sftp', 'ssh', 'telnet', 'webcal')));
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}
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// Get the plain text representation of the attribute value (i.e. its meaning).
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if ($decode) {
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$string = decode_entities($string);
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}
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// Iteratively remove any invalid protocol found.
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do {
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$before = $string;
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$colonpos = strpos($string, ':');
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if ($colonpos > 0) {
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// We found a colon, possibly a protocol. Verify.
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$protocol = substr($string, 0, $colonpos);
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// If a colon is preceded by a slash, question mark or hash, it cannot
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// possibly be part of the URL scheme. This must be a relative URL,
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// which inherits the (safe) protocol of the base document.
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if (preg_match('![/?#]!', $protocol)) {
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break;
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}
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// Per RFC2616, section 3.2.3 (URI Comparison) scheme comparison must be case-insensitive
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// Check if this is a disallowed protocol.
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if (!isset($allowed_protocols[strtolower($protocol)])) {
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$string = substr($string, $colonpos + 1);
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}
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}
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} while ($before != $string);
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return check_plain($string);
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}
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/**
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* @} End of "defgroup sanitization".
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*/
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/**
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* @defgroup format Formatting
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* @{
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@ -911,288 +911,6 @@ function _filter_autop($text) {
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return $output;
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}
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/**
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* Very permissive XSS/HTML filter for admin-only use.
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*
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* Use only for fields where it is impractical to use the
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* whole filter system, but where some (mainly inline) mark-up
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* is desired (so check_plain() is not acceptable).
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*
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* Allows all tags that can be used inside an HTML body, save
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* for scripts and styles.
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*/
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function filter_xss_admin($string) {
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return filter_xss($string, array('a', 'abbr', 'acronym', 'address', 'b', 'bdo', 'big', 'blockquote', 'br', 'caption', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'div', 'dl', 'dt', 'em', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'img', 'ins', 'kbd', 'li', 'ol', 'p', 'pre', 'q', 'samp', 'small', 'span', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'tr', 'tt', 'ul', 'var'));
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}
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/**
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* Filters XSS. Based on kses by Ulf Harnhammar, see
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* http://sourceforge.net/projects/kses
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*
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* For examples of various XSS attacks, see:
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* http://ha.ckers.org/xss.html
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*
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* This code does four things:
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* - Removes characters and constructs that can trick browsers
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* - Makes sure all HTML entities are well-formed
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* - Makes sure all HTML tags and attributes are well-formed
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* - Makes sure no HTML tags contain URLs with a disallowed protocol (e.g. javascript:)
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*
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* @param $string
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* The string with raw HTML in it. It will be stripped of everything that can cause
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* an XSS attack.
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* @param $allowed_tags
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* An array of allowed tags.
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*/
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function filter_xss($string, $allowed_tags = array('a', 'em', 'strong', 'cite', 'blockquote', 'code', 'ul', 'ol', 'li', 'dl', 'dt', 'dd')) {
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// Only operate on valid UTF-8 strings. This is necessary to prevent cross
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// site scripting issues on Internet Explorer 6.
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if (!drupal_validate_utf8($string)) {
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return '';
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}
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// Store the text format
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_filter_xss_split($allowed_tags, TRUE);
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// Remove NULL characters (ignored by some browsers)
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$string = str_replace(chr(0), '', $string);
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// Remove Netscape 4 JS entities
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$string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
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// Defuse all HTML entities
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$string = str_replace('&', '&', $string);
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// Change back only well-formed entities in our whitelist
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// Named entities
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$string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
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// Decimal numeric entities
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$string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
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// Hexadecimal numeric entities
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$string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
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return preg_replace_callback('%
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(
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<(?=[^a-zA-Z!/]) # a lone <
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| # or
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<[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string
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| # or
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> # just a >
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)%x', '_filter_xss_split', $string);
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}
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/**
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* Processes an HTML tag.
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*
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* @param $m
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* An array with various meaning depending on the value of $store.
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* If $store is TRUE then the array contains the allowed tags.
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* If $store is FALSE then the array has one element, the HTML tag to process.
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* @param $store
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* Whether to store $m.
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* @return
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* If the element isn't allowed, an empty string. Otherwise, the cleaned up
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* version of the HTML element.
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*/
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function _filter_xss_split($m, $store = FALSE) {
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static $allowed_html;
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if ($store) {
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$allowed_html = array_flip($m);
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return;
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}
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$string = $m[1];
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if (substr($string, 0, 1) != '<') {
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// We matched a lone ">" character
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return '>';
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}
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elseif (strlen($string) == 1) {
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// We matched a lone "<" character
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return '<';
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}
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if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches)) {
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// Seriously malformed
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return '';
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}
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$slash = trim($matches[1]);
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$elem = &$matches[2];
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$attrlist = &$matches[3];
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if (!isset($allowed_html[strtolower($elem)])) {
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// Disallowed HTML element
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return '';
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}
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if ($slash != '') {
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return "</$elem>";
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}
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// Is there a closing XHTML slash at the end of the attributes?
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$attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count);
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$xhtml_slash = $count ? ' /' : '';
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// Clean up attributes
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$attr2 = implode(' ', _filter_xss_attributes($attrlist));
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$attr2 = preg_replace('/[<>]/', '', $attr2);
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$attr2 = strlen($attr2) ? ' ' . $attr2 : '';
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return "<$elem$attr2$xhtml_slash>";
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}
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/**
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* Processes a string of HTML attributes.
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*
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* @return
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* Cleaned up version of the HTML attributes.
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*/
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function _filter_xss_attributes($attr) {
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$attrarr = array();
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$mode = 0;
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$attrname = '';
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while (strlen($attr) != 0) {
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// Was the last operation successful?
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$working = 0;
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switch ($mode) {
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case 0:
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// Attribute name, href for instance
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if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) {
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$attrname = strtolower($match[1]);
|
||||
$skip = ($attrname == 'style' || substr($attrname, 0, 2) == 'on');
|
||||
$working = $mode = 1;
|
||||
$attr = preg_replace('/^[-a-zA-Z]+/', '', $attr);
|
||||
}
|
||||
|
||||
break;
|
||||
|
||||
case 1:
|
||||
// Equals sign or valueless ("selected")
|
||||
if (preg_match('/^\s*=\s*/', $attr)) {
|
||||
$working = 1; $mode = 2;
|
||||
$attr = preg_replace('/^\s*=\s*/', '', $attr);
|
||||
break;
|
||||
}
|
||||
|
||||
if (preg_match('/^\s+/', $attr)) {
|
||||
$working = 1; $mode = 0;
|
||||
if (!$skip) {
|
||||
$attrarr[] = $attrname;
|
||||
}
|
||||
$attr = preg_replace('/^\s+/', '', $attr);
|
||||
}
|
||||
|
||||
break;
|
||||
|
||||
case 2:
|
||||
// Attribute value, a URL after href= for instance
|
||||
if (preg_match('/^"([^"]*)"(\s+|$)/', $attr, $match)) {
|
||||
$thisval = filter_xss_bad_protocol($match[1]);
|
||||
|
||||
if (!$skip) {
|
||||
$attrarr[] = "$attrname=\"$thisval\"";
|
||||
}
|
||||
$working = 1;
|
||||
$mode = 0;
|
||||
$attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr);
|
||||
break;
|
||||
}
|
||||
|
||||
if (preg_match("/^'([^']*)'(\s+|$)/", $attr, $match)) {
|
||||
$thisval = filter_xss_bad_protocol($match[1]);
|
||||
|
||||
if (!$skip) {
|
||||
$attrarr[] = "$attrname='$thisval'";
|
||||
}
|
||||
$working = 1; $mode = 0;
|
||||
$attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr);
|
||||
break;
|
||||
}
|
||||
|
||||
if (preg_match("%^([^\s\"']+)(\s+|$)%", $attr, $match)) {
|
||||
$thisval = filter_xss_bad_protocol($match[1]);
|
||||
|
||||
if (!$skip) {
|
||||
$attrarr[] = "$attrname=\"$thisval\"";
|
||||
}
|
||||
$working = 1; $mode = 0;
|
||||
$attr = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attr);
|
||||
}
|
||||
|
||||
break;
|
||||
}
|
||||
|
||||
if ($working == 0) {
|
||||
// not well formed, remove and try again
|
||||
$attr = preg_replace('/
|
||||
^
|
||||
(
|
||||
"[^"]*("|$) # - a string that starts with a double quote, up until the next double quote or the end of the string
|
||||
| # or
|
||||
\'[^\']*(\'|$)| # - a string that starts with a quote, up until the next quote or the end of the string
|
||||
| # or
|
||||
\S # - a non-whitespace character
|
||||
)* # any number of the above three
|
||||
\s* # any number of whitespaces
|
||||
/x', '', $attr);
|
||||
$mode = 0;
|
||||
}
|
||||
}
|
||||
|
||||
// the attribute list ends with a valueless attribute like "selected"
|
||||
if ($mode == 1) {
|
||||
$attrarr[] = $attrname;
|
||||
}
|
||||
return $attrarr;
|
||||
}
|
||||
|
||||
/**
|
||||
* Processes an HTML attribute value and ensures it does not contain an URL
|
||||
* with a disallowed protocol (e.g. javascript:)
|
||||
*
|
||||
* @param $string
|
||||
* The string with the attribute value.
|
||||
* @param $decode
|
||||
* Whether to decode entities in the $string. Set to FALSE if the $string
|
||||
* is in plain text, TRUE otherwise. Defaults to TRUE.
|
||||
* @return
|
||||
* Cleaned up and HTML-escaped version of $string.
|
||||
*/
|
||||
function filter_xss_bad_protocol($string, $decode = TRUE) {
|
||||
static $allowed_protocols;
|
||||
if (!isset($allowed_protocols)) {
|
||||
$allowed_protocols = array_flip(variable_get('filter_allowed_protocols', array('ftp', 'http', 'https', 'irc', 'mailto', 'news', 'nntp', 'rtsp', 'sftp', 'ssh', 'telnet', 'webcal')));
|
||||
}
|
||||
|
||||
// Get the plain text representation of the attribute value (i.e. its meaning).
|
||||
if ($decode) {
|
||||
$string = decode_entities($string);
|
||||
}
|
||||
|
||||
// Iteratively remove any invalid protocol found.
|
||||
|
||||
do {
|
||||
$before = $string;
|
||||
$colonpos = strpos($string, ':');
|
||||
if ($colonpos > 0) {
|
||||
// We found a colon, possibly a protocol. Verify.
|
||||
$protocol = substr($string, 0, $colonpos);
|
||||
// If a colon is preceded by a slash, question mark or hash, it cannot
|
||||
// possibly be part of the URL scheme. This must be a relative URL,
|
||||
// which inherits the (safe) protocol of the base document.
|
||||
if (preg_match('![/?#]!', $protocol)) {
|
||||
break;
|
||||
}
|
||||
// Per RFC2616, section 3.2.3 (URI Comparison) scheme comparison must be case-insensitive
|
||||
// Check if this is a disallowed protocol.
|
||||
if (!isset($allowed_protocols[strtolower($protocol)])) {
|
||||
$string = substr($string, $colonpos + 1);
|
||||
}
|
||||
}
|
||||
} while ($before != $string);
|
||||
return check_plain($string);
|
||||
}
|
||||
|
||||
/**
|
||||
* @} End of "Standard filters".
|
||||
*/
|
||||
|
|
|
|||
Loading…
Reference in New Issue