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WordPress/wp-includes/kses.php
saxmatt 10792f3274 More filters and KSES cleanup. 
git-svn-id: http://svn.automattic.com/wordpress/trunk@2151 1a063a9b-81f0-0310-95a4-ce76da25c4cd
2005-01-26 22:29:18 +00:00

563 lines
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PHP
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<?php
// Added wp_ prefix to avoid conflicts with existing kses users
# kses 0.2.1 - HTML/XHTML filter that only allows some elements and attributes
# Copyright (C) 2002, 2003 Ulf Harnhammar
# *** CONTACT INFORMATION ***
#
# E-mail: metaur at users dot sourceforge dot net
# Web page: http://sourceforge.net/projects/kses
# Paper mail: (not at the moment)
#
# [kses strips evil scripts!]
if (!defined('CUSTOM_TAGS'))
define('CUSTOM_TAGS', false);
// You can override this in your my-hacks.php file
if (!CUSTOM_TAGS) {
$allowedtags = array(
'a' => array(
'href' => array(),
'title' => array()
),
'abbr' => array('title' => array()),
'acronym' => array('title' => array()),
'b' => array(),
'blockquote' => array('cite' => array()),
// 'br' => array(),
'code' => array(),
// 'del' => array('datetime' => array()),
// 'dd' => array(),
// 'dl' => array(),
// 'dt' => array(),
'em' => array(),
'i' => array(),
// 'ins' => array('datetime' => array(), 'cite' => array()),
// 'li' => array(),
// 'ol' => array(),
// 'p' => array(),
// 'q' => array(),
'strike' => array(),
'strong' => array(),
// 'sub' => array(),
// 'sup' => array(),
// 'u' => array(),
// 'ul' => array(),
);
}
function wp_kses($string, $allowed_html, $allowed_protocols =
array('http', 'https', 'ftp', 'news', 'nntp', 'feed', 'gopher', 'mailto'))
###############################################################################
# This function makes sure that only the allowed HTML element names, attribute
# names and attribute values plus only sane HTML entities will occur in
# $string. You have to remove any slashes from PHP's magic quotes before you
# call this function.
###############################################################################
{
$string = wp_kses_no_null($string);
$string = wp_kses_js_entities($string);
$string = wp_kses_normalize_entities($string);
$string = wp_kses_hook($string);
$allowed_html_fixed = wp_kses_array_lc($allowed_html);
return wp_kses_split($string, $allowed_html_fixed, $allowed_protocols);
} # function wp_kses
function wp_kses_hook($string)
###############################################################################
# You add any kses hooks here.
###############################################################################
{
return $string;
} # function wp_kses_hook
function wp_kses_version()
###############################################################################
# This function returns kses' version number.
###############################################################################
{
return '0.2.1';
} # function wp_kses_version
function wp_kses_split($string, $allowed_html, $allowed_protocols)
###############################################################################
# This function searches for HTML tags, no matter how malformed. It also
# matches stray ">" characters.
###############################################################################
{
return preg_replace('%(<'. # EITHER: <
'[^>]*'. # things that aren't >
'(>|$)'. # > or end of string
'|>)%e', # OR: just a >
"wp_kses_split2('\\1', \$allowed_html, ".
'$allowed_protocols)',
$string);
} # function wp_kses_split
function wp_kses_split2($string, $allowed_html, $allowed_protocols)
###############################################################################
# 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.
###############################################################################
{
$string = wp_kses_stripslashes($string);
if (substr($string, 0, 1) != '<')
return '&gt;';
# It matched a ">" character
if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches))
return '';
# It's seriously malformed
$slash = trim($matches[1]);
$elem = $matches[2];
$attrlist = $matches[3];
if (!is_array($allowed_html[strtolower($elem)]))
return '';
# They are using a not allowed HTML element
return wp_kses_attr("$slash$elem", $attrlist, $allowed_html,
$allowed_protocols);
} # function wp_kses_split2
function wp_kses_attr($element, $attr, $allowed_html, $allowed_protocols)
###############################################################################
# This function removes all attributes, if none are allowed for this element.
# If some are allowed it calls wp_kses_hair() to split them further, and then it
# builds up new HTML code from the data that kses_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.
###############################################################################
{
# Is there a closing XHTML slash at the end of the attributes?
$xhtml_slash = '';
if (preg_match('%\s/\s*$%', $attr))
$xhtml_slash = ' /';
# Are any attributes allowed at all for this element?
if (count($allowed_html[strtolower($element)]) == 0)
return "<$element$xhtml_slash>";
# Split it
$attrarr = wp_kses_hair($attr, $allowed_protocols);
# Go through $attrarr, and save the allowed attributes for this element
# in $attr2
$attr2 = '';
foreach ($attrarr as $arreach)
{
$current = $allowed_html[strtolower($element)]
[strtolower($arreach['name'])];
if ($current == '')
continue; # the attribute is not allowed
if (!is_array($current))
$attr2 .= ' '.$arreach['whole'];
# there are no checks
else
{
# there are some checks
$ok = true;
foreach ($current as $currkey => $currval)
if (!wp_kses_check_attr_val($arreach['value'], $arreach['vless'],
$currkey, $currval))
{ $ok = false; break; }
if ($ok)
$attr2 .= ' '.$arreach['whole']; # it passed them
} # if !is_array($current)
} # foreach
# Remove any "<" or ">" characters
$attr2 = preg_replace('/[<>]/', '', $attr2);
return "<$element$attr2$xhtml_slash>";
} # function wp_kses_attr
function wp_kses_hair($attr, $allowed_protocols)
###############################################################################
# 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.
###############################################################################
{
$attrarr = array();
$mode = 0;
$attrname = '';
# Loop through the whole attribute list
while (strlen($attr) != 0)
{
$working = 0; # Was the last operation successful?
switch ($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"
{
$thisval = wp_kses_bad_protocol($match[1], $allowed_protocols);
$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'
{
$thisval = wp_kses_bad_protocol($match[1], $allowed_protocols);
$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
{
$thisval = wp_kses_bad_protocol($match[1], $allowed_protocols);
$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
{
$attr = wp_kses_html_error($attr);
$mode = 0;
}
} # while
if ($mode == 1)
# special case, for when the attribute list ends with a valueless
# attribute like "selected"
$attrarr[] = array
('name' => $attrname,
'value' => '',
'whole' => $attrname,
'vless' => 'y');
return $attrarr;
} # function wp_kses_hair
function wp_kses_check_attr_val($value, $vless, $checkname, $checkvalue)
###############################################################################
# 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.
###############################################################################
{
$ok = true;
switch (strtolower($checkname))
{
case 'maxlen':
# 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.
if (strlen($value) > $checkvalue)
$ok = false;
break;
case 'minlen':
# The minlen check makes sure that the attribute value has a length not
# smaller than the given value.
if (strlen($value) < $checkvalue)
$ok = false;
break;
case 'maxval':
# The maxval check does two things: it checks that the attribute value is
# an integer from 0 and up, without an excessive amount of zeroes or
# whitespace (to avoid Buffer Overflows). It also checks that the attribute
# value is not greater than the given value.
# This check can be used to avoid Denial of Service attacks.
if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
$ok = false;
if ($value > $checkvalue)
$ok = false;
break;
case 'minval':
# The minval check checks that the attribute value is a positive integer,
# and that it is not smaller than the given value.
if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
$ok = false;
if ($value < $checkvalue)
$ok = false;
break;
case 'valueless':
# The valueless check checks if the attribute has a value
# (like <a href="blah">) or not (<option selected>). If the given value
# is a "y" or a "Y", the attribute must not have a value.
# If the given value is an "n" or an "N", the attribute must have one.
if (strtolower($checkvalue) != $vless)
$ok = false;
break;
} # switch
return $ok;
} # function wp_kses_check_attr_val
function wp_kses_bad_protocol($string, $allowed_protocols)
###############################################################################
# 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)".
###############################################################################
{
$string = wp_kses_no_null($string);
$string2 = $string.'a';
while ($string != $string2)
{
$string2 = $string;
$string = wp_kses_bad_protocol_once($string, $allowed_protocols);
} # while
return $string;
} # function wp_kses_bad_protocol
function wp_kses_no_null($string)
###############################################################################
# This function removes any NULL or chr(173) characters in $string.
###############################################################################
{
$string = preg_replace('/\0+/', '', $string);
$string = preg_replace('/(\\\\0)+/', '', $string);
return $string;
} # function wp_kses_no_null
function wp_kses_stripslashes($string)
###############################################################################
# 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.
###############################################################################
{
return preg_replace('%\\\\"%', '"', $string);
} # function wp_kses_stripslashes
function wp_kses_array_lc($inarray)
###############################################################################
# This function goes through an array, and changes the keys to all lower case.
###############################################################################
{
$outarray = array();
foreach ($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 $outarray;
} # function wp_kses_array_lc
function wp_kses_js_entities($string)
###############################################################################
# This function removes the HTML JavaScript entities found in early versions of
# Netscape 4.
###############################################################################
{
return preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
} # function wp_kses_js_entities
function wp_kses_html_error($string)
###############################################################################
# This function deals with parsing errors in wp_kses_hair(). The general plan is
# to remove everything to and including some whitespace, but it deals with
# quotes and apostrophes as well.
###############################################################################
{
return preg_replace('/^("[^"]*("|$)|\'[^\']*(\'|$)|\S)*\s*/', '', $string);
} # function wp_kses_html_error
function wp_kses_bad_protocol_once($string, $allowed_protocols)
###############################################################################
# This function searches for URL protocols at the beginning of $string, while
# handling whitespace and HTML entities.
###############################################################################
{
return preg_replace('/^((&[^;]*;|[\sA-Za-z0-9])*)'.
'(:|&#58;|&#[Xx]3[Aa];)\s*/e',
'wp_kses_bad_protocol_once2("\\1", $allowed_protocols)',
$string);
} # function wp_kses_bad_protocol_once
function wp_kses_bad_protocol_once2($string, $allowed_protocols)
###############################################################################
# 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.
###############################################################################
{
$string2 = wp_kses_decode_entities($string);
$string2 = preg_replace('/\s/', '', $string2);
$string2 = wp_kses_no_null($string2);
$string2 = strtolower($string2);
$allowed = false;
foreach ($allowed_protocols as $one_protocol)
if (strtolower($one_protocol) == $string2)
{
$allowed = true;
break;
}
if ($allowed)
return "$string2:";
else
return '';
} # function wp_kses_bad_protocol_once2
function wp_kses_normalize_entities($string)
###############################################################################
# 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.
###############################################################################
{
# Disarm all entities by converting & to &amp;
$string = str_replace('&', '&amp;', $string);
# Change back the allowed entities in our entity whitelist
$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',
'wp_kses_normalize_entities2("\\1")', $string);
$string = preg_replace('/&amp;#([Xx])0*(([0-9A-Fa-f]{2}){1,2});/',
'&#\\1\\2;', $string);
return $string;
} # function wp_kses_normalize_entities
function wp_kses_normalize_entities2($i)
###############################################################################
# This function helps wp_kses_normalize_entities() to only accept 16 bit values
# and nothing more for &#number; entities.
###############################################################################
{
return (($i > 65535) ? "&amp;#$i;" : "&#$i;");
} # function wp_kses_normalize_entities2
function wp_kses_decode_entities($string)
###############################################################################
# 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 whitelisting system anyway.
###############################################################################
{
$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 wp_kses_decode_entities
function wp_filter_kses( $string ) {
global $allowedtags;
return wp_kses($string, $allowedtags);
}
?>
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