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kses AUTHORS
============
* Ulf Harnhammar <metaur at users dot sourceforge dot net>
main coder, project leader
* Richard R. Vasquez, Jr. (contact him at http://www.chaos.org/contact/)
coder (object-oriented kses)
* Simon Cornelius P. Umacob <simoncpu at users dot sourceforge dot net>
tester
Thanks to a lot of people who posted to the Bugtraq and Webappsec mailing lists
about XSS or HTML filters. They gave us some valuable insights.

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kses ChangeLog
==============
* 0.2.1
0.2.1 was released on the 29th of September 2003.
It has the following changes:
- There is now an additional version of kses, using the object-oriented
paradigm. Thanks a lot to Richard R. Vasquez, Jr., who created it! Anyone
who wants to make functional programming, logical programming or spaghetti
programming versions of kses as well (or any other programming paradigm that
you like), go ahead! All the people who like old procedural programming for
web applications shouldn't despair, though, as both versions will be
maintained with each release.
- kses now has some new attribute value checks: minlen, minval and valueless.
See docs/attribute-value-checks for an explanation.
- For some reason, the Opera developers decided to make chr(173) a whitespace
character in URL protocols, both when it occurs raw and in an entity. kses
now handles this.
- The URL protocol whitelisting system now decodes entities before removing
NULLs and whitespaces.
* 0.2.0
0.2.0 was released on the 25th of July 2003.
It has the following changes:
- kses now supports checking of attribute values, and not just element names
and attribute names. The attribute value checks that exist so far are
'maxlen' (checks how long attribute values are, to avoid Buffer Overflows)
and 'maxval' (checks how big an integer value is, to avoid Denial of Service
attacks).
Buffer Overflows could both be a problem for WWW clients and different
servers on the Internet that an HTML document links to. One example is
<frame src="ftp://ftp.v1ct1m.com/AAAAAA..thousands_of_A's...">.
Denial of Service attacks can take the form of too big sizes of iframes or
other things. One example is <iframe src="http://some.web.server/"
width="20000" height="2000">, which makes some client machines completely
overloaded.
- kses' old feature of removing "javascript:" from attribute values has been
improved. It now has a whole system for white listing of URL protocols, so
you can specify that it's acceptable with http:, https:, ftp: and gopher:,
but no other protocols in attribute values. The system tries pretty hard to
do the right thing with whitespace, upper/lower case, HTML entities
("jav&#97;script:") and repeated entries ("javascript:javascript:alert(57)").
- kses now supports both HTML and XHTML code, by allowing " /" at the end of
tags.
- kses now removes Netscape 4's JavaScript entities, having the form
"&{alert(57)};". They don't even seem to work on all versions of Netscape 4,
but for completeness' sake it seemed like a good feature to add.
- A bug with NULLs in javascript: URLs was fixed.
(Reported by Simon Cornelius P. Umacob - thanks!)
- As a nice side effect of the white listing of URL protocols, kses now also
normalizes all HTML entities in documents. It will change HTML code with bad
entities to the right form, for example "AT&T" will be converted to
"AT&amp;T" and "<a href='lyrics.php?band=ladytron&lyrics=playgirl'>" will be
converted to "<a href='lyrics.php?band=ladytron&amp;lyrics=playgirl'>".
"&#000058;" will be converted to "&#58;", "&#XYZZY;" will be converted to
"&amp;#XYZZY;", "&auml!;" will be converted to "&amp;auml!;" and so on.
As shown above, it will process HTML entities that it doesn't understand.
It will also deal with too big numbers in numeric HTML entities, which is
helpful as many browsers seem to wrap them around at 2 ** 32, so the
characters 58, 58 + (2 ** 32), 58 + (2 ** 64) etcetera are all colons to the
web browser.
- You can now use upper case letters in your $allowed_html array, in element
names, attribute names and attribute value check names. Version 0.1.0
required everything in that array to be in lower case, but that's not
necessary any more. You can also use upper case letters in
$allowed_protocols.
- The "Really malformed thing" bug from the TODO file was fixed.
It used to convert this string:
x > 5 <a href="blah">
to:
x &gt; 5 &lt;a href=&quot;blah&quot;&gt;
and now it converts it to:
x &gt; 5 <a href="blah">
- The "Weird malformed thing" bug from the TODO file was fixed.
It used to convert this string:
<a href="5 href=6>
to:
<a href="6">
because of the way kses restarts after a parse error in kses_hair(). Now it
converts it to:
<a>
- A problem with slashes in HTML tags was fixed.
- examples/filter.php used to use $SCRIPT_NAME, which doesn't work on
Windows.
(Reported by Simon Cornelius P. Umacob - thanks!)
- kses now allows dashes in attribute names, for things like
<meta http-equiv=..>.
* 0.1.0, first public version
0.1.0 was released on the 9th of June 2003.
It was announced on three security related mailing lists on Friday the 13th
of June (nothing bad happened to it though).

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kses 0.2.1 README [kses strips evil scripts!]
=================
* INTRODUCTION *
Welcome to kses - an HTML/XHTML filter written in PHP. It removes all unwanted
HTML elements and attributes, no matter how malformed HTML input you give it.
It also does several checks on attribute values. kses can be used to avoid
Cross-Site Scripting (XSS), Buffer Overflows and Denial of Service attacks,
among other things.
The program is released under the terms of the GNU General Public License. You
should look into what that means, before using kses in your programs. You can
find the full text of the license in the file COPYING.
* FEATURES *
Some of kses' current features are:
* It will only allow the HTML elements and attributes that it was explicitly
told to allow.
* Element and attribute names are case-insensitive (a href vs A HREF).
* It will understand and process whitespace correctly.
* Attribute values can be surrounded with quotes, apostrophes or nothing.
* It will accept valueless attributes with just names and no values (selected).
* It will accept XHTML's closing " /" marks.
* Attribute values that are surrounded with nothing will get quotes to avoid
producing non-W3C conforming HTML
(<a href=http://sourceforge.net/projects/kses> works but isn't valid HTML).
* It handles lots of types of malformed HTML, by interpreting the existing
code the best it can and then rebuilding new code from it. That's a better
approach than trying to process existing code, as you're bound to forget about
some weird special case somewhere. It handles problems like never-ending
quotes and tags gracefully.
* It will remove additional "<" and ">" characters that people may try to
sneak in somewhere.
* It supports checking attribute values for minimum/maximum length and
minimum/maximum value, to protect against Buffer Overflows and Denial of
Service attacks against WWW clients and various servers. You can stop
<iframe src= width= height=> from having too high values for width and height,
for instance.
* It has got a system for whitelisting URL protocols. You can say that
attribute values may only start with http:, https:, ftp: and gopher:, but no
other URL protocols (javascript:, java:, about:, telnet:..). The functions that
do this work handle whitespace, upper/lower case, HTML entities
("jav&#97;script:") and repeated entries ("javascript:javascript:alert(57)").
It also normalizes HTML entities as a nice side effect.
* It removes Netscape 4's JavaScript entities ("&{alert(57)};").
* It handles NULL bytes and Opera's chr(173) whitespace characters.
* There is both a procedural version and an object-oriented version of kses.
* USE IT *
It's very easy to use kses in your own PHP web application! Basic usage looks
like this:
<?php
include 'kses.php';
$allowed = array('b' => array(),
'i' => array(),
'a' => array('href' => 1, 'title' => 1),
'p' => array('align' => 1),
'br' => array());
$val = $_POST['val'];
if (get_magic_quotes_gpc())
$val = stripslashes($val);
# You must strip slashes from magic quotes, or kses will get confused.
$val = kses($val, $allowed); # The filtering takes place here.
# Do something with $val.
?>
This definition of $allowed means that only the elements B, I, A, P and BR are
allowed (along with their closing tags /B, /I, /A, /P and /BR). B, I and BR
may not have any attributes. A may only have the attributes HREF and TITLE,
while P may only have the attribute ALIGN. You can list the elements and
attributes in the array in any mixture of upper and lower case. kses will also
recognize HTML code that uses both lower and upper case.
It's important to select the right allowed attributes, so you won't open up
an XSS hole by mistake. Some important attributes that you mustn't allow
include but are not limited to: 1) style, and 2) all intrinsic events
attributes (onMouseOver and so on, on* really). I'll write more about this in
the documentation that will be distributed with future versions of kses.
It's also important to note that kses' HTML input must be cleaned of all
slashes coming from magic quotes. If the rest of your code requires these
slashes to be present, you can always add them again after calling kses with
a simple addslashes() call.
You should take a look at the documentation in the docs/ directory and the
examples in the examples/ directory, to get more information on how to use
kses. The object-oriented version of kses is also worth checking out, and it's
included in the oop/ directory.
* UPGRADING FROM 0.1.0 OR 0.2.0 TO 0.2.1 *
kses 0.2.1 is backwards compatible with 0.1.0 and 0.2.0, so upgrading should
just be a matter of using a new version of kses.php instead of an old one!
When you're ready to start using 0.2.1's new features, you can read about them
in the files in the docs/ directory. The ChangeLog also summarizes the new
features in this release.
* NEW VERSIONS, MAILING LISTS AND BUG REPORTS *
If you want to download new versions, subscribe to the kses-general mailing
list or even take part in the development of kses, we refer you to its
homepage at http://sourceforge.net/projects/kses . New developers and beta
testers are more than welcome!
If you have any bug reports, suggestions for improvement or simply want to tell
us that you use kses for some project, feel free to post to the kses-general
mailing list. If you have found any security problems (particularly XSS,
naturally) in kses, please contact Ulf privately at metaur at users dot
sourceforge dot net so he can correct it before you or someone else tells the
public about it.
(No, it's not a security problem in kses if some program that uses it allows a
bad attribute, silly. If kses is told to accept the element body with the
attributes style and onLoad, it will accept them, even if that's a really bad
idea, securitywise.)
* OTHER HTML FILTERS *
Here are the other stand-alone, open source HTML filters that we currently know
of:
* XSS filter for PHP4 - the filter from Squirrelmail
PHP
Konstantin Riabitsev
http://www.mricon.com/html/phpfilter.html
* HTML::StripScripts and related CPAN modules
Perl
Nick Cleaton
http://search.cpan.org/perldoc?HTML%3A%3AStripScripts
There are also a lot of HTML filters that were written specifically for some
program. Some of them are better than others.
Please write to the kses-general mailing list if you know of any other
stand-alone, open-source filters.
* DEDICATION *
kses 0.2.1 is dedicated to Mischa the cat.
* MISC *
The kses code is based on an HTML filter that Ulf wrote on his own back in 2002
for the open-source project Gnuheter ( http://savannah.nongnu.org/projects/
gnuheter ). Gnuheter is a fork from PHP-Nuke. The HTML filter has been
improved a lot since then.
To stop people from having sleepless nights, we feel the urgent need to state
that kses doesn't have anything to do with the KDE project, despite having a
name that starts with a K.
In case someone was wondering, Ulf is available for kses-related consulting.
Finally, the name kses comes from the terms XSS and access. It's also a
recursive acronym (every open-source project should have one!) for "kses
strips evil scripts".
// Ulf and the kses gang, September 2003

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kses TODO
=========
* remove stuff in between <script>..</script> and <style>..</style>
* more attribute value checks
* more types of hooks
* return array of removed elements and attributes
* give the option of turning unacceptable elements to entities instead of
removing them (and turn unacceptable attributes to their own tag, which is
then turned to entities?) .. perhaps turn to comments as well?
* XHTML tags of the style <br/> instead of <br />
This is related to a small bug with <a href="blah />
Solution: rewrite parser.
* ">" in HTML tags
<img src="blah.gif" alt="x > 5">
Not very important, but..
* lots of testing
* write better documentation
* feedback from users
* create a nice homepage (any volunteers?)

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kses attribute value checks
===========================
As you've probably already read in the README file, an $allowed_html array
normally looks like this:
$allowed = array('b' => array(),
'i' => array(),
'a' => array('href' => 1,
'title' => 1),
'p' => array('align' => 1),
'br' => array());
This sets what elements and attributes are allowed.
From kses 0.2.0, you can also perform some checks on the attribute values. You
do it like this:
$allowed = array('b' => array(),
'i' => array(),
'a' => array('href' =>
array('maxlen' => 100),
'title' => 1),
'p' => array('align' => 1),
'font' => array('size' =>
array('maxval' => 20)),
'br' => array());
This means that kses should perform the maxlen check with the value 100 on the
<a href=> value, as well as the maxval check with the value 20 on the <font
size=> value.
The currently implemented checks (with more to come) are 'maxlen', 'maxval',
'minlen', 'minval' and 'valueless'.
'maxlen' checks that the length of the attribute value is not greater than the
given value. It is helpful against Buffer Overflows in WWW clients and various
servers on the Internet. In my example above, it would mean that
"<a href='ftp://ftp.v1ct1m.com/AAAA..thousands_of_A's...'>" wouldn't be
accepted.
Of course, this problem is even worse if you put that long URL in a <frame>
tag instead, so the WWW client will fetch it automatically without a user
having to click it.
'maxval' checks that the attribute value is an integer greater than or equal to
zero, that it doesn't have an unreasonable amount of zeroes or whitespace (to
avoid Buffer Overflows), and that it is not greater than the given value. In
my example above, it would mean that "<font size='20'>" is accepted but
"<font size='21'>" is not. This check helps against Denial of Service attacks
against WWW clients.
One example of this DoS problem is <iframe src="http://some.web.server/"
width="20000" height="2000">, which makes some client machines completely
overloaded.
'minlen' and 'minval' works the same as 'maxlen' and 'maxval', except that they
check for minimum lengths and values instead of maximum ones.
'valueless' checks if an attribute has a value (like <a href="blah">) or not
(<option selected>). If the given value is a "y" or a "Y", the attribute must
not have a value to be accepted. If the given value is an "n" or an "N", the
attribute must have a value. Note that <a href=""> is considered to have a
value, so there's a difference between valueless attributes and attribute
values with the length zero.
You can combine more than one check, by putting one after the other in the
inner array.

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kses hooks
==========
Sometimes you want to perform one more action on all data that kses will
filter. There is a special function for that purpose called kses_hook(). kses
calls it from its main function kses(), so if you insert some code in
kses_hook(), it will always be called to change all data that kses sees.

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kses whitelisted URL protocols
==============================
From kses 0.2.0, it has a function that checks all attribute values for URL
protocols and only allows the protocols given in a whitelist.
If you call kses the old way with two parameters - a string and an
$allowed_html array - it will take its own default array, which whitelists the
protocols http, https, ftp, news, nntp, telnet, gopher and mailto. Pretty
reasonable, but anyone who wants to change it just calls the kses() function
with a third parameter, like this:
$string = kses($string, $allowed_html, array('http', 'https'));
Note that you shouldn't include any colon after http or other protocol names.

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<?php
/*
* This is a fork of a slick piece of procedural code called 'kses' written by Ulf Harnhammar
* The entire set of functions was wrapped in a PHP object with some internal modifications
* by Richard Vasquez (http://www.chaos.org/) 7/25/2003
*
* The original (procedural) version of the code can be found at:
* http://sourceforge.net/projects/kses/
*
* [kses strips evil scripts!]
*
* ==========================================================================================
*
* class.kses.php 0.0.2 - PHP class that filters HTML/XHTML only allowing some elements and
* attributes to be passed through.
*
* Copyright (C) 2003 Richard R. Vasquez, Jr.
*
* Derived from kses 0.2.1 - HTML/XHTML filter that only allows some elements and attributes
* Copyright (C) 2002, 2003 Ulf Harnhammar
*
* ==========================================================================================
*
* This program is free software and open source software; you can redistribute
* it and/or modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the License,
* or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA or visit
* http://www.gnu.org/licenses/gpl.html
*
* ==========================================================================================
* CONTACT INFORMATION:
*
* Email: View current valid email address at http://www.chaos.org/contact/
*/
class kses
{
var $allowed_protocols = array('http', 'https', 'ftp', 'news', 'nntp', 'telnet', 'gopher', 'mailto');
var $allowed_html = array();
function kses()
{
}
function Parse($string = "")
{
if (get_magic_quotes_gpc())
{
$string = stripslashes($string);
}
$string = $this->_no_null($string);
$string = $this->_js_entities($string);
$string = $this->_normalize_entities($string);
$string = $this->_hook($string);
return $this->_split($string);
}
function Protocols()
{
$c_args = func_num_args();
if($c_args != 1)
{
return false;
}
$protocol_data = func_get_arg(0);
if(is_array($protocol_data))
{
foreach($protocol_data as $protocol)
{
$this->AddProtocol($protocol);
}
}
elseif(is_string($protocol_data))
{
$this->AddProtocol($protocol_data);
return true;
}
else
{
trigger_error("kses::Protocols() did not receive a string or an array.", E_USER_WARNING);
return false;
}
}
function AddProtocol($protocol = "")
{
if(!is_string($protocol))
{
trigger_error("kses::AddProtocol() requires a string.", E_USER_WARNING);
return false;
}
$protocol = strtolower(trim($protocol));
if($protocol == "")
{
trigger_error("kses::AddProtocol() tried to add an empty/NULL protocol.", E_USER_WARNING);
return false;
}
// Remove any inadvertent ':' at the end of the protocol.
if(substr($protocol, strlen($protocol) - 1, 1) == ":")
{
$protocol = substr($protocol, 0, strlen($protocol) - 1);
}
if(!in_array($protocol, $this->allowed_protocols))
{
array_push($this->allowed_protocols, $protocol);
sort($this->allowed_protocols);
}
return true;
}
function AddHTML($tag = "", $attribs = array())
{
if(!is_string($tag))
{
trigger_error("kses::AddHTML() requires the tag to be a string", E_USER_WARNING);
return false;
}
$tag = strtolower(trim($tag));
if($tag == "")
{
trigger_error("kses::AddHTML() tried to add an empty/NULL tag", E_USER_WARNING);
return false;
}
if(!is_array($attribs))
{
trigger_error("kses::AddHTML() requires an array (even an empty one) of attributes for '$tag'", E_USER_WARNING);
return false;
}
$new_attribs = array();
foreach($attribs as $idx1 => $val1)
{
$new_idx1 = strtolower($idx1);
$new_val1 = $attribs[$idx1];
if(is_array($new_val1))
{
$tmp_val = array();
foreach($new_val1 as $idx2 => $val2)
{
$new_idx2 = strtolower($idx2);
$tmp_val[$new_idx2] = $val2;
}
$new_val1 = $tmp_val;
}
$new_attribs[$new_idx1] = $new_val1;
}
$this->allowed_html[$tag] = $new_attribs;
return true;
}
###############################################################################
# This function removes any NULL or chr(173) characters in $string.
###############################################################################
function _no_null($string)
{
$string = preg_replace('/\0+/', '', $string);
$string = preg_replace('/(\\\\0)+/', '', $string);
$string = preg_replace('/\xad+/', '', $string); # deals with Opera "feature"
return $string;
} # function _no_null
###############################################################################
# This function removes the HTML JavaScript entities found in early versions of
# Netscape 4.
###############################################################################
function _js_entities($string)
{
return preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
} # function _js_entities
###############################################################################
# This function normalizes HTML entities. It will convert "AT&T" to the correct
# "AT&amp;T", "&#00058;" to "&#58;", "&#XYZZY;" to "&amp;#XYZZY;" and so on.
###############################################################################
function _normalize_entities($string)
{
# Disarm all entities by converting & to &amp;
$string = str_replace('&', '&amp;', $string);
# Change back the allowed entities in our entity white list
$string = preg_replace('/&amp;([A-Za-z][A-Za-z0-9]{0,19});/', '&\\1;', $string);
$string = preg_replace('/&amp;#0*([0-9]{1,5});/e', '\$this->_normalize_entities2("\\1")', $string);
$string = preg_replace('/&amp;#([Xx])0*(([0-9A-Fa-f]{2}){1,2});/', '&#\\1\\2;', $string);
return $string;
} # function _normalize_entities
###############################################################################
# This function helps _normalize_entities() to only accept 16 bit values
# and nothing more for &#number; entities.
###############################################################################
function _normalize_entities2($i)
{
return (($i > 65535) ? "&amp;#$i;" : "&#$i;");
} # function _normalize_entities2
###############################################################################
# You add any kses hooks here.
###############################################################################
function _hook($string)
{
return $string;
} # function _hook
###############################################################################
# This function goes through an array, and changes the keys to all lower case.
###############################################################################
function _array_lc($inarray)
{
$outarray = array();
foreach ($inarray as $inkey => $inval)
{
$outkey = strtolower($inkey);
$outarray[$outkey] = array();
foreach ($inval as $inkey2 => $inval2)
{
$outkey2 = strtolower($inkey2);
$outarray[$outkey][$outkey2] = $inval2;
} # foreach $inval
} # foreach $inarray
return $outarray;
} # function _array_lc
###############################################################################
# This function searches for HTML tags, no matter how malformed. It also
# matches stray ">" characters.
###############################################################################
function _split($string)
{
return preg_replace(
'%(<'. # EITHER: <
'[^>]*'. # things that aren't >
'(>|$)'. # > or end of string
'|>)%e', # OR: just a >
"\$this->_split2('\\1')",
$string);
} # function _split
function _split2($string)
###############################################################################
# This function does a lot of work. It rejects some very malformed things
# like <:::>. It returns an empty string, if the element isn't allowed (look
# ma, no strip_tags()!). Otherwise it splits the tag into an element and an
# attribute list.
###############################################################################
{
$string = $this->_stripslashes($string);
if (substr($string, 0, 1) != '<')
{
# It matched a ">" character
return '&gt;';
}
if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches))
{
# It's seriously malformed
return '';
}
$slash = trim($matches[1]);
$elem = $matches[2];
$attrlist = $matches[3];
if (!is_array($this->allowed_html[strtolower($elem)]))
{
# They are using a not allowed HTML element
return '';
}
return $this->_attr("$slash$elem", $attrlist);
} # function _split2
###############################################################################
# This function removes all attributes, if none are allowed for this element.
# If some are allowed it calls s_hair() to split them further, and then it
# builds up new HTML code from the data that _hair() returns. It also
# removes "<" and ">" characters, if there are any left. One more thing it
# does is to check if the tag has a closing XHTML slash, and if it does,
# it puts one in the returned code as well.
###############################################################################
function _attr($element, $attr)
{
# Is there a closing XHTML slash at the end of the attributes?
$xhtml_slash = '';
if (preg_match('%\s/\s*$%', $attr))
{
$xhtml_slash = ' /';
}
# Are any attributes allowed at all for this element?
if (count($this->allowed_html[strtolower($element)]) == 0)
{
return "<$element$xhtml_slash>";
}
# Split it
$attrarr = $this->_hair($attr);
# Go through $attrarr, and save the allowed attributes for this element
# in $attr2
$attr2 = '';
foreach ($attrarr as $arreach)
{
$current = $this->allowed_html[strtolower($element)][strtolower($arreach['name'])];
if ($current == '')
{
# the attribute is not allowed
continue;
}
if (!is_array($current))
{
# there are no checks
$attr2 .= ' '.$arreach['whole'];
}
else
{
# there are some checks
$ok = true;
foreach ($current as $currkey => $currval)
{
if (!$this->_check_attr_val($arreach['value'], $arreach['vless'], $currkey, $currval))
{
$ok = false;
break;
}
}
if ($ok)
{
# it passed them
$attr2 .= ' '.$arreach['whole'];
}
} # if !is_array($current)
} # foreach
# Remove any "<" or ">" characters
$attr2 = preg_replace('/[<>]/', '', $attr2);
return "<$element$attr2$xhtml_slash>";
} # function _attr
###############################################################################
# This function does a lot of work. It parses an attribute list into an array
# with attribute data, and tries to do the right thing even if it gets weird
# input. It will add quotes around attribute values that don't have any quotes
# or apostrophes around them, to make it easier to produce HTML code that will
# conform to W3C's HTML specification. It will also remove bad URL protocols
# from attribute values.
###############################################################################
function _hair($attr)
{
$attrarr = array();
$mode = 0;
$attrname = '';
# Loop through the whole attribute list
while (strlen($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 = $match[1];
$working = $mode = 1;
$attr = preg_replace('/^[-a-zA-Z]+/', '', $attr);
}
break;
case 1: # equals sign or valueless ("selected")
if (preg_match('/^\s*=\s*/', $attr)) # equals sign
{
$working = 1;
$mode = 2;
$attr = preg_replace('/^\s*=\s*/', '', $attr);
break;
}
if (preg_match('/^\s+/', $attr)) # valueless
{
$working = 1;
$mode = 0;
$attrarr[] = array(
'name' => $attrname,
'value' => '',
'whole' => $attrname,
'vless' => 'y'
);
$attr = preg_replace('/^\s+/', '', $attr);
}
break;
case 2: # attribute value, a URL after href= for instance
if (preg_match('/^"([^"]*)"(\s+|$)/', $attr, $match)) # "value"
{
$thisval = $this->_bad_protocol($match[1]);
$attrarr[] = array(
'name' => $attrname,
'value' => $thisval,
'whole' => "$attrname=\"$thisval\"",
'vless' => 'n'
);
$working = 1;
$mode = 0;
$attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr);
break;
}
if (preg_match("/^'([^']*)'(\s+|$)/", $attr, $match)) # 'value'
{
$thisval = $this->_bad_protocol($match[1]);
$attrarr[] = array(
'name' => $attrname,
'value' => $thisval,
'whole' => "$attrname='$thisval'",
'vless' => 'n'
);
$working = 1;
$mode = 0;
$attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr);
break;
}
if (preg_match("%^([^\s\"']+)(\s+|$)%", $attr, $match)) # value
{
$thisval = $this->_bad_protocol($match[1]);
$attrarr[] = array(
'name' => $attrname,
'value' => $thisval,
'whole' => "$attrname=\"$thisval\"",
'vless' => 'n'
);
# We add quotes to conform to W3C's HTML spec.
$working = 1;
$mode = 0;
$attr = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attr);
}
break;
} # switch
if ($working == 0) # not well formed, remove and try again
{
$attr = $this->_html_error($attr);
$mode = 0;
}
} # while
# special case, for when the attribute list ends with a valueless
# attribute like "selected"
if ($mode == 1)
{
$attrarr[] = array(
'name' => $attrname,
'value' => '',
'whole' => $attrname,
'vless' => 'y'
);
}
return $attrarr;
} # function _hair
###############################################################################
# This function removes all non-allowed protocols from the beginning of
# $string. It ignores whitespace and the case of the letters, and it does
# understand HTML entities. It does its work in a while loop, so it won't be
# fooled by a string like "javascript:javascript:alert(57)".
###############################################################################
function _bad_protocol($string)
{
$string = $this->_no_null($string);
$string2 = $string.'a';
while ($string != $string2)
{
$string2 = $string;
$string = $this->_bad_protocol_once($string);
} # while
return $string;
} # function _bad_protocol
###############################################################################
# This function searches for URL protocols at the beginning of $string, while
# handling whitespace and HTML entities.
###############################################################################
function _bad_protocol_once($string)
{
return preg_replace(
'/^((&[^;]*;|[\sA-Za-z0-9])*)'.
'(:|&#58;|&#[Xx]3[Aa];)\s*/e',
'\$this->_bad_protocol_once2("\\1")',
$string
);
return $string;
} # function _bad_protocol_once
###############################################################################
# This function processes URL protocols, checks to see if they're in the white-
# list or not, and returns different data depending on the answer.
###############################################################################
function _bad_protocol_once2($string)
{
$string2 = $this->_decode_entities($string2);
$string2 = preg_replace('/\s/', '', $string);
$string2 = $this->_no_null($string2);
$string2 = strtolower($string2);
$allowed = false;
foreach ($this->allowed_protocols as $one_protocol)
{
if (strtolower($one_protocol) == $string2)
{
$allowed = true;
break;
}
}
if ($allowed)
{
return "$string2:";
}
else
{
return '';
}
} # function _bad_protocol_once2
###############################################################################
# This function performs different checks for attribute values. The currently
# implemented checks are "maxlen", "minlen", "maxval", "minval" and "valueless"
# with even more checks to come soon.
###############################################################################
function _check_attr_val($value, $vless, $checkname, $checkvalue)
{
$ok = true;
switch (strtolower($checkname))
{
# The maxlen check makes sure that the attribute value has a length not
# greater than the given value. This can be used to avoid Buffer Overflows
# in WWW clients and various Internet servers.
case 'maxlen':
if (strlen($value) > $checkvalue)
{
$ok = false;
}
break;
# The minlen check makes sure that the attribute value has a length not
# smaller than the given value.
case 'minlen':
if (strlen($value) < $checkvalue)
{
$ok = false;
}
break;
# The maxval check does two things: it checks that the attribute value is
# an integer from 0 and up, without an excessive amount of zeroes or
# whitespace (to avoid Buffer Overflows). It also checks that the attribute
# value is not greater than the given value.
# This check can be used to avoid Denial of Service attacks.
case 'maxval':
if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
{
$ok = false;
}
if ($value > $checkvalue)
{
$ok = false;
}
break;
# The minval check checks that the attribute value is a positive integer,
# and that it is not smaller than the given value.
case 'minval':
if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
{
$ok = false;
}
if ($value < $checkvalue)
{
$ok = false;
}
break;
# The valueless check checks if the attribute has a value
# (like <a href="blah">) or not (<option selected>). If the given value
# is a "y" or a "Y", the attribute must not have a value.
# If the given value is an "n" or an "N", the attribute must have one.
case 'valueless':
if (strtolower($checkvalue) != $vless)
{
$ok = false;
}
break;
} # switch
return $ok;
} # function _check_attr_val
###############################################################################
# This function changes the character sequence \" to just "
# It leaves all other slashes alone. It's really weird, but the quoting from
# preg_replace(//e) seems to require this.
###############################################################################
function _stripslashes($string)
{
return preg_replace('%\\\\"%', '"', $string);
} # function _stripslashes
###############################################################################
# This function deals with parsing errors in _hair(). The general plan is
# to remove everything to and including some whitespace, but it deals with
# quotes and apostrophes as well.
###############################################################################
function _html_error($string)
{
return preg_replace('/^("[^"]*("|$)|\'[^\']*(\'|$)|\S)*\s*/', '', $string);
} # function _html_error
###############################################################################
# This function decodes numeric HTML entities (&#65; and &#x41;). It doesn't
# do anything with other entities like &auml;, but we don't need them in the
# URL protocol white listing system anyway.
###############################################################################
function _decode_entities($string)
{
$string = preg_replace('/&#([0-9]+);/e', 'chr("\\1")', $string);
$string = preg_replace('/&#[Xx]([0-9A-Fa-f]+);/e', 'chr(hexdec("\\1"))', $string);
return $string;
} # function _decode_entities
###############################################################################
# This function returns kses' version number.
###############################################################################
function _version()
{
return '0.0.2 (OOP fork of kses 0.2.1)';
} # function _version
}
?>