<?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)+/', '', $string); # commented out, because it breaks chinese chars #$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*;?|$)%', '', $string); } # function _js_entities ############################################################################### # This function normalizes HTML entities. It will convert "AT&T" to the correct # "AT&T", ":" to ":", "&#XYZZY;" to "&#XYZZY;" and so on. ############################################################################### function _normalize_entities($string) { # Disarm all entities by converting & to & $string = str_replace('&', '&', $string); # Change back the allowed entities in our entity white list $string = preg_replace('/&([A-Za-z][A-Za-z0-9]{0,19});/', '&\\1;', $string); $string = preg_replace('/&#0*([0-9]{1,5});/e', '\$this->_normalize_entities2("\\1")', $string); $string = preg_replace('/&#([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 (($i > 65535) ? "&#$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($string, 0, 1) != '<') { # It matched a ">" character return '>'; } if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $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$xhtml_slash>"; } # Split it //_debug_array($attr); $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) { //echo __METHOD__.'called<br>'; $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, $match)) { //echo 'mode 0:'.$match[0].'<br>'; $attrname = $match[1]; //echo 'mode 0 -> attrname:'.$attrname.'<br>'; $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*/', '', $attr); //echo 'mode 1:'.$attr.'<br>'; break; } if (preg_match('/^\s+/', $attr)) # valueless { $working = 1; $mode = 0; $attrarr[] = array( 'name' => $attrname, 'value' => '', 'whole' => $attrname, 'vless' => 'y' ); $attr = preg_replace('/^\s+/', '', $attr); } break; case 2: # attribute value, a URL after href= for instance //echo 'mode 2 Attrname:'.$attrname.'<br>'; if (preg_match('/^"([^"]*)"(\s+|$)/', $attr, $match)) # "value" { $thisval = ($attrname == 'name' ? $match[1] : $this->_bad_protocol($match[1])); $attrarr[] = array( 'name' => $attrname, 'value' => $thisval, 'whole' => "$attrname=\"$thisval\"", 'vless' => 'n' ); $working = 1; $mode = 0; $attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr); //echo 'mode 2:'.$attr.'<br>'; break; } if (preg_match("/^'([^']*)'(\s+|$)/", $attr, $match)) # 'value' { $thisval = ($attrname == 'name' ? $match[1] : $this->_bad_protocol($match[1])); $attrarr[] = array( 'name' => $attrname, 'value' => $thisval, 'whole' => "$attrname='$thisval'", 'vless' => 'n' ); $working = 1; $mode = 0; $attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr); //echo 'mode 2:'.$attr.'<br>'; break; } if (preg_match("%^([^\s\"']+)(\s+|$)%", $attr, $match)) # value { $thisval = ($attrname == 'name' ? $match[1] : $this->_bad_protocol($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) { if ($string[0]=='#') return $string; // its an anchor, dont check for protocol any further $string2 = preg_split('/:|:|:/i', $string, 2); if(isset($string2[1]) && !preg_match('%/\?%',$string2[0])) { return $this->_bad_protocol_once2($string2[0]).trim($string2[1]); } else { if (!isset($string2[1])) { return $string2[0]; } else { return ''; } } return ''; } # function _bad_protocol_once ############################################################################### # This function processes URL protocols, checks to see if they're in the white- # list or not, and returns different data depending on the answer. ############################################################################### function _bad_protocol_once2($string) { $string2 = $this->_decode_entities($string); $string2 = preg_replace('/\s/', '', $string2); $string2 = $this->_no_null($string2); $string2 = preg_replace('/\xad+/', '', $string2); # deals with Opera "feature" $string2 = strtolower($string2); $allowed = false; if(is_array($this->allowed_protocols) && count($this->allowed_protocols) > 0) { foreach ($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) { $ok = false; } break; # The minval check checks that the attribute value is a positive integer, # and that it is not smaller than the given value. case 'match': if (!preg_match($checkvalue, $value)) { $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*/', '', $string); } # function _html_error ############################################################################### # This function decodes numeric HTML entities (A and A). It doesn't # do anything with other entities like ä, but we don't need them in the # URL protocol white listing system anyway. ############################################################################### function _decode_entities($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 } ?>