Commit a5f42fd0 authored by Dries's avatar Dries

- Patch #470632 by sun: move filter_xss*() into common.inc.

parent adf71134
......@@ -1256,6 +1256,12 @@ function check_file($filename) {
return is_uploaded_file($filename);
}
/**
* @defgroup sanitization Sanitization functions
* @{
* Functions to sanitize values.
*/
/**
* Prepare a URL for use in an HTML attribute. Strips harmful protocols.
*/
......@@ -1263,6 +1269,291 @@ function check_url($uri) {
return filter_xss_bad_protocol($uri, FALSE);
}
/**
* Very permissive XSS/HTML filter for admin-only use.
*
* Use only for fields where it is impractical to use the
* whole filter system, but where some (mainly inline) mark-up
* is desired (so check_plain() is not acceptable).
*
* Allows all tags that can be used inside an HTML body, save
* for scripts and styles.
*/
function filter_xss_admin($string) {
return filter_xss($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'));
}
/**
* Filter XSS.
*
* Based on kses by Ulf Harnhammar, see
* http://sourceforge.net/projects/kses
*
* For examples of various XSS attacks, see:
* http://ha.ckers.org/xss.html
*
* This code does four things:
* - Removes characters and constructs that can trick browsers
* - Makes sure all HTML entities are well-formed
* - Makes sure all HTML tags and attributes are well-formed
* - Makes sure no HTML tags contain URLs with a disallowed protocol (e.g. javascript:)
*
* @param $string
* The string with raw HTML in it. It will be stripped of everything that can cause
* an XSS attack.
* @param $allowed_tags
* An array of allowed tags.
*/
function filter_xss($string, $allowed_tags = array('a', 'em', 'strong', 'cite', 'blockquote', 'code', 'ul', 'ol', 'li', 'dl', 'dt', 'dd')) {
// Only operate on valid UTF-8 strings. This is necessary to prevent cross
// site scripting issues on Internet Explorer 6.
if (!drupal_validate_utf8($string)) {
return '';
}
// Store the text format
_filter_xss_split($allowed_tags, TRUE);
// Remove NULL characters (ignored by some browsers)
$string = str_replace(chr(0), '', $string);
// Remove Netscape 4 JS entities
$string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
// Defuse all HTML entities
$string = str_replace('&', '&', $string);
// Change back only well-formed entities in our whitelist
// Named entities
$string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
// Decimal numeric entities
$string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
// Hexadecimal numeric entities
$string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
return preg_replace_callback('%
(
<(?=[^a-zA-Z!/]) # a lone <
| # or
<[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string
| # or
> # just a >
)%x', '_filter_xss_split', $string);
}
/**
* Processes an HTML tag.
*
* @param $m
* An array with various meaning depending on the value of $store.
* If $store is TRUE then the array contains the allowed tags.
* If $store is FALSE then the array has one element, the HTML tag to process.
* @param $store
* Whether to store $m.
* @return
* If the element isn't allowed, an empty string. Otherwise, the cleaned up
* version of the HTML element.
*/
function _filter_xss_split($m, $store = FALSE) {
static $allowed_html;
if ($store) {
$allowed_html = array_flip($m);
return;
}
$string = $m[1];
if (substr($string, 0, 1) != '<') {
// We matched a lone ">" character
return '&gt;';
}
elseif (strlen($string) == 1) {
// We matched a lone "<" character
return '&lt;';
}
if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches)) {
// Seriously malformed
return '';
}
$slash = trim($matches[1]);
$elem = &$matches[2];
$attrlist = &$matches[3];
if (!isset($allowed_html[strtolower($elem)])) {
// Disallowed HTML element
return '';
}
if ($slash != '') {
return "</$elem>";
}
// Is there a closing XHTML slash at the end of the attributes?
$attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count);
$xhtml_slash = $count ? ' /' : '';
// Clean up attributes
$attr2 = implode(' ', _filter_xss_attributes($attrlist));
$attr2 = preg_replace('/[<>]/', '', $attr2);
$attr2 = strlen($attr2) ? ' ' . $attr2 : '';
return "<$elem$attr2$xhtml_slash>";
}
/**
* Processes a string of HTML attributes.
*
* @return
* Cleaned up version of the HTML attributes.
*/
function _filter_xss_attributes($attr) {
$attrarr = array();
$mode = 0;
$attrname = '';
while (strlen($attr) != 0) {
// Was the last operation successful?
$working = 0;
switch ($mode) {
case 0:
// Attribute name, href for instance
if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) {
$attrname = strtolower($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 "defgroup sanitization".
*/
/**
* @defgroup format Formatting
* @{
......
......@@ -911,288 +911,6 @@ function _filter_autop($text) {
return $output;
}
/**
* Very permissive XSS/HTML filter for admin-only use.
*
* Use only for fields where it is impractical to use the
* whole filter system, but where some (mainly inline) mark-up
* is desired (so check_plain() is not acceptable).
*
* Allows all tags that can be used inside an HTML body, save
* for scripts and styles.
*/
function filter_xss_admin($string) {
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'));
}
/**
* Filters XSS. Based on kses by Ulf Harnhammar, see
* http://sourceforge.net/projects/kses
*
* For examples of various XSS attacks, see:
* http://ha.ckers.org/xss.html
*
* This code does four things:
* - Removes characters and constructs that can trick browsers
* - Makes sure all HTML entities are well-formed
* - Makes sure all HTML tags and attributes are well-formed
* - Makes sure no HTML tags contain URLs with a disallowed protocol (e.g. javascript:)
*
* @param $string
* The string with raw HTML in it. It will be stripped of everything that can cause
* an XSS attack.
* @param $allowed_tags
* An array of allowed tags.
*/
function filter_xss($string, $allowed_tags = array('a', 'em', 'strong', 'cite', 'blockquote', 'code', 'ul', 'ol', 'li', 'dl', 'dt', 'dd')) {
// Only operate on valid UTF-8 strings. This is necessary to prevent cross
// site scripting issues on Internet Explorer 6.
if (!drupal_validate_utf8($string)) {
return '';
}
// Store the text format
_filter_xss_split($allowed_tags, TRUE);
// Remove NULL characters (ignored by some browsers)
$string = str_replace(chr(0), '', $string);
// Remove Netscape 4 JS entities
$string = preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
// Defuse all HTML entities
$string = str_replace('&', '&amp;', $string);
// Change back only well-formed entities in our whitelist
// Named entities
$string = preg_replace('/&amp;([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
// Decimal numeric entities
$string = preg_replace('/&amp;#([0-9]+;)/', '&#\1', $string);
// Hexadecimal numeric entities
$string = preg_replace('/&amp;#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
return preg_replace_callback('%
(
<(?=[^a-zA-Z!/]) # a lone <
| # or
<[^>]*(>|$) # a string that starts with a <, up until the > or the end of the string
| # or
> # just a >
)%x', '_filter_xss_split', $string);
}
/**
* Processes an HTML tag.
*
* @param $m
* An array with various meaning depending on the value of $store.
* If $store is TRUE then the array contains the allowed tags.
* If $store is FALSE then the array has one element, the HTML tag to process.
* @param $store
* Whether to store $m.
* @return
* If the element isn't allowed, an empty string. Otherwise, the cleaned up
* version of the HTML element.
*/
function _filter_xss_split($m, $store = FALSE) {
static $allowed_html;
if ($store) {
$allowed_html = array_flip($m);
return;
}
$string = $m[1];
if (substr($string, 0, 1) != '<') {
// We matched a lone ">" character
return '&gt;';
}
elseif (strlen($string) == 1) {
// We matched a lone "<" character
return '&lt;';
}
if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches)) {
// Seriously malformed
return '';
}
$slash = trim($matches[1]);
$elem = &$matches[2];
$attrlist = &$matches[3];
if (!isset($allowed_html[strtolower($elem)])) {
// Disallowed HTML element
return '';
}
if ($slash != '') {
return "</$elem>";
}
// Is there a closing XHTML slash at the end of the attributes?
$attrlist = preg_replace('%(\s?)/\s*$%', '\1', $attrlist, -1, $count);
$xhtml_slash = $count ? ' /' : '';
// Clean up attributes
$attr2 = implode(' ', _filter_xss_attributes($attrlist));
$attr2 = preg_replace('/[<>]/', '', $attr2);
$attr2 = strlen($attr2) ? ' ' . $attr2 : '';
return "<$elem$attr2$xhtml_slash>";
}
/**
* Processes a string of HTML attributes.
*
* @return
* Cleaned up version of the HTML attributes.
*/
function _filter_xss_attributes($attr) {
$attrarr = array();
$mode = 0;
$attrname = '';
while (strlen($attr) != 0) {
// Was the last operation successful?
$working = 0;
switch ($mode) {
case 0:
// Attribute name, href for instance
if (preg_match('/^([-a-zA-Z]+)/', $attr, $match)) {
$attrname = strtolower($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".
*/
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