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995 lines
30 KiB
PHP
995 lines
30 KiB
PHP
<?php
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/**
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* htmlfilter.inc
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* ---------------
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* This set of functions allows you to filter html in order to remove
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* any malicious tags from it. Useful in cases when you need to filter
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* user input for any cross-site-scripting attempts.
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*
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* Copyright (c) 2002 by Duke University
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*
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* @Author Konstantin Riabitsev <icon@linux.duke.edu>
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* @Version 1.0.5 (Oct-16-2002)
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*/
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class htmlfilter
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{
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/**
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* See http://www.mricon.com/html/phpfilter.html
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*
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* This is a debugging function used throughout the code. To enable
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* debugging you have to specify a global variable called "debug" before
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* calling sanitize() and set it to true.
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*
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* Note: Although insignificantly, debugging does slow you down even
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* when $debug is set to false. If you wish to get rid of all
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* debugging calls, run the following command:
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*
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* fgrep -v 'spew("' htmlfilter.inc > htmlfilter.inc.new
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*
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* htmlfilter.inc.new will contain no debugging calls.
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*
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* @param $message A string with the message to output.
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* @return void.
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*/
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function spew($message){
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global $debug;
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#$debug = true;
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if ($debug == true){
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echo "$message<br>";
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}
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}
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/**
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* This function returns the final tag out of the tag name, an array
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* of attributes, and the type of the tag. This function is called by
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* sanitize internally.
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*
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* @param $tagname the name of the tag.
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* @param $attary the array of attributes and their values
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* @param $tagtype The type of the tag (see in comments).
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* @return a string with the final tag representation.
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*/
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function tagprint($tagname, $attary, $tagtype){
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$me = 'tagprint';
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if ($tagtype == 2){
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$fulltag = '</' . $tagname . '>';
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} else {
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$fulltag = '<' . $tagname;
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if (is_array($attary) && sizeof($attary)){
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$atts = Array();
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while (list($attname, $attvalue) = each($attary)){
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array_push($atts, "$attname=$attvalue");
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}
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$fulltag .= ' ' . join(' ', $atts);
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}
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if ($tagtype == 3){
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$fulltag .= ' /';
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}
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$fulltag .= '>';
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}
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$this->spew("$me: $fulltag\n");
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return $fulltag;
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}
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/**
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* A small helper function to use with array_walk. Modifies a by-ref
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* value and makes it lowercase.
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*
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* @param $val a value passed by-ref.
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* @return void since it modifies a by-ref value.
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*/
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function casenormalize(&$val){
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$val = strtolower($val);
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}
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/**
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* This function skips any whitespace from the current position within
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* a string and to the next non-whitespace value.
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*
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* @param $body the string
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* @param $offset the offset within the string where we should start
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* looking for the next non-whitespace character.
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* @return the location within the $body where the next
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* non-whitespace char is located.
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*/
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function skipspace($body, $offset){
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$me = 'skipspace';
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preg_match('/^(\s*)/s', substr($body, $offset), $matches);
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if (sizeof($matches{1})){
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$count = strlen($matches{1});
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$this->spew("$me: skipped $count chars\n");
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$offset += $count;
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}
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return $offset;
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}
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/**
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* This function looks for the next character within a string. It's
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* really just a glorified "strpos", except it catches the failures
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* nicely.
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*
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* @param $body The string to look for needle in.
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* @param $offset Start looking from this position.
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* @param $needle The character/string to look for.
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* @return location of the next occurance of the needle, or
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* strlen($body) if needle wasn't found.
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*/
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function findnxstr($body, $offset, $needle){
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$me = 'findnxstr';
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$pos = strpos($body, $needle, $offset);
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if ($pos === FALSE){
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$pos = strlen($body);
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$this->spew("$me: end of body reached\n");
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}
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$this->spew("$me: '$needle' found at pos $pos\n");
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return $pos;
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}
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/**
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* This function takes a PCRE-style regexp and tries to match it
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* within the string.
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*
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* @param $body The string to look for needle in.
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* @param $offset Start looking from here.
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* @param $reg A PCRE-style regex to match.
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* @return Returns a false if no matches found, or an array
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* with the following members:
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* - integer with the location of the match within $body
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* - string with whatever content between offset and the match
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* - string with whatever it is we matched
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*/
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function findnxreg($body, $offset, $reg){
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$me = 'findnxreg';
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$matches = Array();
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$retarr = Array();
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$preg_rule = '%^(.*?)(' . $reg . ')%s';
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preg_match($preg_rule, substr($body, $offset), $matches);
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if (!$matches{0}){
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$this->spew("$me: No matches found.\n");
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$retarr = false;
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} else {
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$retarr{0} = $offset + strlen($matches{1});
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$retarr{1} = $matches{1};
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$retarr{2} = $matches{2};
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$this->spew("$me: '$reg' found at pos $offset matching '".$matches{2}."'\n");
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}
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return $retarr;
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}
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/**
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* This function looks for the next tag.
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*
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* @param $body String where to look for the next tag.
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* @param $offset Start looking from here.
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* @return false if no more tags exist in the body, or
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* an array with the following members:
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* - string with the name of the tag
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* - array with attributes and their values
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* - integer with tag type (1, 2, or 3)
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* - integer where the tag starts (starting "<")
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* - integer where the tag ends (ending ">")
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* first three members will be false, if the tag is invalid.
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*/
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function getnxtag($body, $offset){
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$me = 'getnxtag';
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if ($offset > strlen($body)){
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$this->spew("$me: Past the end of body\n");
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return false;
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}
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$lt = $this->findnxstr($body, $offset, '<');
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if ($lt == strlen($body)){
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$this->spew("$me: No more tags found!\n");
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return false;
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}
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/**
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* We are here:
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* blah blah <tag attribute="value">
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* \---------^
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*/
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$this->spew("$me: Found '<' at pos $lt\n");
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$pos = $this->skipspace($body, $lt + 1);
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if ($pos >= strlen($body)){
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$this->spew("$me: End of body reached.\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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/**
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* There are 3 kinds of tags:
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* 1. Opening tag, e.g.:
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* <a href="blah">
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* 2. Closing tag, e.g.:
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* </a>
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* 3. XHTML-style content-less tag, e.g.:
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* <img src="blah"/>
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*/
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$tagtype = false;
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switch (substr($body, $pos, 1)){
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case '/':
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$this->spew("$me: This is a closing tag (type 2)\n");
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$tagtype = 2;
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$pos++;
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break;
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case '!':
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/**
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* A comment or an SGML declaration.
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*/
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if (substr($body, $pos+1, 2) == '--'){
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$this->spew("$me: A comment found. Stripping.\n");
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$gt = strpos($body, '-->', $pos);
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if ($gt === false){
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$gt = strlen($body);
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} else {
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$gt += 2;
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}
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return Array(false, false, false, $lt, $gt);
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} else {
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$this->spew("$me: An SGML declaration found. Stripping.\n");
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$gt = $this->findnxstr($body, $pos, '>');
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return Array(false, false, false, $lt, $gt);
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}
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break;
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default:
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/**
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* Assume tagtype 1 for now. If it's type 3, we'll switch values
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* later.
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*/
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$tagtype = 1;
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break;
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}
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$tag_start = $pos;
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$tagname = '';
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/**
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* Look for next [\W-_], which will indicate the end of the tag name.
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*/
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$regary = $this->findnxreg($body, $pos, '[^\w\-_]');
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if ($regary == false){
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$this->spew("$me: End of body reached while analyzing tag name\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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list($pos, $tagname, $match) = $regary;
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$tagname = strtolower($tagname);
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/**
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* $match can be either of these:
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* '>' indicating the end of the tag entirely.
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* '\s' indicating the end of the tag name.
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* '/' indicating that this is type-3 xhtml tag.
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*
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* Whatever else we find there indicates an invalid tag.
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*/
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switch ($match){
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case '/':
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/**
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* This is an xhtml-style tag with a closing / at the
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* end, like so: <img src="blah"/>. Check if it's followed
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* by the closing bracket. If not, then this tag is invalid
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*/
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if (substr($body, $pos, 2) == '/>'){
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$this->spew("$me: XHTML-style tag found.\n");
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$pos++;
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$this->spew("$me: Setting tagtype to 3\n");
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$tagtype = 3;
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} else {
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$this->spew("$me: Found invalid character '/'.\n");
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$gt = $this->findnxstr($body, $pos, '>');
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$this->spew("$me: Tag is invalid. Returning.\n");
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$retary = Array(false, false, false, $lt, $gt);
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return $retary;
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}
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case '>':
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$this->spew("$me: End of tag found at $pos\n");
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$this->spew("$me: Tagname is '$tagname'\n");
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$this->spew("$me: This tag has no attributes\n");
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return Array($tagname, false, $tagtype, $lt, $pos);
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break;
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default:
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/**
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* Check if it's whitespace
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*/
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if (preg_match('/\s/', $match)){
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$this->spew("$me: Tagname is '$tagname'\n");
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} else {
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/**
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* This is an invalid tag! Look for the next closing ">".
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*/
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$this->spew("$me: Invalid characters found in tag name: $match\n");
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$gt = $this->findnxstr($body, $offset, '>');
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return Array(false, false, false, $lt, $gt);
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}
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}
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/**
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* At this point we're here:
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* <tagname attribute='blah'>
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* \-------^
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*
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* At this point we loop in order to find all attributes.
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*/
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$attname = '';
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$atttype = false;
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$attary = Array();
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while ($pos <= strlen($body)){
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$pos = $this->skipspace($body, $pos);
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if ($pos == strlen($body)){
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/**
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* Non-closed tag.
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*/
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$this->spew("$me: End of body reached before end of tag. Discarding.\n");
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return Array(false, false, false, $lt, $pos);
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}
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/**
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* See if we arrived at a ">" or "/>", which means that we reached
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* the end of the tag.
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*/
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$matches = Array();
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preg_match('%^(\s*)(>|/>)%s', substr($body, $pos), $matches);
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if (isset($matches{0}) && $matches{0}){
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/**
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* Yep. So we did.
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*/
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$this->spew("$me: Arrived at the end of the tag.\n");
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$pos += strlen($matches{1});
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if ($matches{2} == '/>'){
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$tagtype = 3;
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$pos++;
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}
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return Array($tagname, $attary, $tagtype, $lt, $pos);
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}
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/**
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* There are several types of attributes, with optional
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* [:space:] between members.
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* Type 1:
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* attrname[:space:]=[:space:]'CDATA'
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* Type 2:
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* attrname[:space:]=[:space:]"CDATA"
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* Type 3:
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* attr[:space:]=[:space:]CDATA
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* Type 4:
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* attrname
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*
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* We leave types 1 and 2 the same, type 3 we check for
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* '"' and convert to """ if needed, then wrap in
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* double quotes. Type 4 we convert into:
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* attrname="yes".
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*/
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$regary = $this->findnxreg($body, $pos, '[^\w\-_]');
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if ($regary == false){
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/**
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* Looks like body ended before the end of tag.
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*/
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$this->spew("$me: End of body found before end of tag.\n");
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$this->spew("$me: Invalid, returning\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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list($pos, $attname, $match) = $regary;
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$attname = strtolower($attname);
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$this->spew("$me: Attribute '$attname' found\n");
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/**
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* We arrived at the end of attribute name. Several things possible
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* here:
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* '>' means the end of the tag and this is attribute type 4
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* '/' if followed by '>' means the same thing as above
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* '\s' means a lot of things -- look what it's followed by.
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* anything else means the attribute is invalid.
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*/
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switch($match){
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case '/':
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/**
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* This is an xhtml-style tag with a closing / at the
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* end, like so: <img src="blah"/>. Check if it's followed
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* by the closing bracket. If not, then this tag is invalid
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*/
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if (substr($body, $pos, 2) == '/>'){
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$this->spew("$me: This is an xhtml-style tag.\n");
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$pos++;
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$this->spew("$me: Setting tagtype to 3\n");
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$tagtype = 3;
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} else {
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$this->spew("$me: Found invalid character '/'.\n");
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$gt = $this->findnxstr($body, $pos, '>');
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$this->spew("$me: Tag is invalid. Returning.\n");
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$retary = Array(false, false, false, $lt, $gt);
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return $retary;
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}
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case '>':
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$this->spew("$me: found type 4 attribute.\n");
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$this->spew("$me: Additionally, end of tag found at $pos\n");
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$this->spew("$me: Attname is '$attname'\n");
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$this->spew("$me: Setting attvalue to 'yes'\n");
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$attary{$attname} = '"yes"';
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return Array($tagname, $attary, $tagtype, $lt, $pos);
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break;
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default:
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/**
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* Skip whitespace and see what we arrive at.
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*/
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$pos = $this->skipspace($body, $pos);
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$char = substr($body, $pos, 1);
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/**
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* Two things are valid here:
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* '=' means this is attribute type 1 2 or 3.
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* \w means this was attribute type 4.
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* anything else we ignore and re-loop. End of tag and
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* invalid stuff will be caught by our checks at the beginning
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* of the loop.
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*/
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if ($char == '='){
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$this->spew("$me: Attribute type 1, 2, or 3 found.\n");
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$pos++;
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$pos = $this->skipspace($body, $pos);
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/**
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* Here are 3 possibilities:
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* "'" attribute type 1
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* '"' attribute type 2
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* everything else is the content of tag type 3
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*/
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$quot = substr($body, $pos, 1);
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if ($quot == '\''){
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$this->spew("$me: In fact, this is attribute type 1\n");
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$this->spew("$me: looking for closing quote\n");
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$regary = $this->findnxreg($body, $pos+1, '\'');
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if ($regary == false){
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$this->spew("$me: end of body reached before end of val\n");
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$this->spew("$me: Returning\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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list($pos, $attval, $match) = $regary;
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$this->spew("$me: Attvalue is '$attval'\n");
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$pos++;
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$attary{$attname} = '\'' . $attval . '\'';
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} else if ($quot == '"'){
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$this->spew("$me: In fact, this is attribute type 2\n");
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$this->spew("$me: looking for closing quote\n");
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$regary = $this->findnxreg($body, $pos+1, '\"');
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if ($regary == false){
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$this->spew("$me: end of body reached before end of val\n");
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$this->spew("$me: Returning\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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list($pos, $attval, $match) = $regary;
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$this->spew("$me: Attvalue is \"$attval\"\n");
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$pos++;
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$attary{$attname} = '"' . $attval . '"';
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} else {
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$this->spew("$me: This looks like attribute type 3\n");
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/**
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* These are hateful. Look for \s, or >.
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*/
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$this->spew("$me: Looking for end of attval\n");
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$regary = $this->findnxreg($body, $pos, '[\s>]');
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if ($regary == false){
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$this->spew("$me: end of body reached before end of val\n");
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$this->spew("$me: Returning\n");
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return Array(false, false, false, $lt, strlen($body));
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}
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list($pos, $attval, $match) = $regary;
|
|
/**
|
|
* If it's ">" it will be caught at the top.
|
|
*/
|
|
$this->spew("$me: translating '\"' into "\n");
|
|
$attval = preg_replace('/\"/s', '"', $attval);
|
|
$this->spew("$me: wrapping in quotes\n");
|
|
$attary{$attname} = '"' . $attval . '"';
|
|
}
|
|
} else if (preg_match('|[\w/>]|', $char)) {
|
|
/**
|
|
* That was attribute type 4.
|
|
*/
|
|
$this->spew("$me: attribute type 4 found.\n");
|
|
$this->spew("$me: Setting value to 'yes'\n");
|
|
$attary{$attname} = '"yes"';
|
|
} else {
|
|
/**
|
|
* An illegal character. Find next '>' and return.
|
|
*/
|
|
$this->spew("$me: illegal character '$char' found.\n");
|
|
$this->spew("$me: returning\n");
|
|
$gt = $this->findnxstr($body, $pos, '>');
|
|
return Array(false, false, false, $lt, $gt);
|
|
}
|
|
}
|
|
}
|
|
/**
|
|
* The fact that we got here indicates that the tag end was never
|
|
* found. Return invalid tag indication so it gets stripped.
|
|
*/
|
|
$this->spew("$me: No tag end found\n");
|
|
return Array(false, false, false, $lt, strlen($body));
|
|
}
|
|
|
|
/**
|
|
* This function checks attribute values for entity-encoded values
|
|
* and returns them translated into 8-bit strings so we can run
|
|
* checks on them.
|
|
*
|
|
* @param $attvalue A string to run entity check against.
|
|
* @return Translated value.
|
|
*/
|
|
function deent($attvalue){
|
|
$me = 'deent';
|
|
/**
|
|
* See if we have to run the checks first. All entities must start
|
|
* with "&".
|
|
*/
|
|
if (strpos($attvalue, '&') === false){
|
|
return $attvalue;
|
|
}
|
|
/**
|
|
* Check named entities first.
|
|
*/
|
|
$this->spew("$me: translating named entities\n");
|
|
$trans = get_html_translation_table(HTML_ENTITIES);
|
|
/**
|
|
* Leave " in, as it can mess us up.
|
|
*/
|
|
$trans = array_flip($trans);
|
|
unset($trans{'"'});
|
|
while (list($ent, $val) = each($trans)){
|
|
$attvalue = preg_replace('/' . $ent . '*/si', $val, $attvalue);
|
|
}
|
|
/**
|
|
* Now translate numbered entities from 1 to 255 if needed.
|
|
*/
|
|
if (strpos($attvalue, '#') !== false){
|
|
$this->spew("$me: translating numbered entities\n");
|
|
$omit = Array(34, 39);
|
|
for ($asc = 256; $asc >= 0; $asc--){
|
|
if (!in_array($asc, $omit)){
|
|
$chr = chr($asc);
|
|
$octrule = '/\�*' . $asc . ';*/si';
|
|
$hexrule = '/\�*' . dechex($asc) . ';*/si';
|
|
$attvalue = preg_replace($octrule, $chr, $attvalue);
|
|
$attvalue = preg_replace($hexrule, $chr, $attvalue);
|
|
}
|
|
}
|
|
}
|
|
$this->spew("$me: translated into: $attvalue\n");
|
|
return $attvalue;
|
|
}
|
|
|
|
/**
|
|
* This function runs various checks against the attributes.
|
|
*
|
|
* @param $tagname String with the name of the tag.
|
|
* @param $attary Array with all tag attributes.
|
|
* @param $rm_attnames See description for sanitize
|
|
* @param $bad_attvals See description for sanitize
|
|
* @param $add_attr_to_tag See description for sanitize
|
|
* @return Array with modified attributes.
|
|
*/
|
|
function fixatts($tagname,
|
|
$attary,
|
|
$rm_attnames,
|
|
$bad_attvals,
|
|
$add_attr_to_tag
|
|
){
|
|
$me = 'fixatts';
|
|
$this->spew("$me: Fixing attributes\n");
|
|
while (list($attname, $attvalue) = each($attary)){
|
|
/**
|
|
* See if this attribute should be removed.
|
|
*/
|
|
foreach ($rm_attnames as $matchtag=>$matchattrs){
|
|
if (preg_match($matchtag, $tagname)){
|
|
foreach ($matchattrs as $matchattr){
|
|
if (preg_match($matchattr, $attname)){
|
|
$this->spew("$me: Attribute '$attname' defined as bad.\n");
|
|
$this->spew("$me: Removing.\n");
|
|
unset($attary{$attname});
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
/**
|
|
* Remove any entities.
|
|
*/
|
|
$attvalue = $this->deent($attvalue);
|
|
|
|
/**
|
|
* Now let's run checks on the attvalues.
|
|
* I don't expect anyone to comprehend this. If you do,
|
|
* get in touch with me so I can drive to where you live and
|
|
* shake your hand personally. :)
|
|
*/
|
|
foreach ($bad_attvals as $matchtag=>$matchattrs){
|
|
if (preg_match($matchtag, $tagname)){
|
|
foreach ($matchattrs as $matchattr=>$valary){
|
|
if (preg_match($matchattr, $attname)){
|
|
/**
|
|
* There are two arrays in valary.
|
|
* First is matches.
|
|
* Second one is replacements
|
|
*/
|
|
list($valmatch, $valrepl) = $valary;
|
|
$newvalue = preg_replace($valmatch, $valrepl, $attvalue);
|
|
if ($newvalue != $attvalue){
|
|
$this->spew("$me: attvalue is now $newvalue\n");
|
|
$attary{$attname} = $newvalue;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
/**
|
|
* See if we need to append any attributes to this tag.
|
|
*/
|
|
foreach ($add_attr_to_tag as $matchtag=>$addattary){
|
|
if (preg_match($matchtag, $tagname)){
|
|
$attary = array_merge($attary, $addattary);
|
|
$this->spew("$me: Added attributes to this tag\n");
|
|
}
|
|
}
|
|
return $attary;
|
|
}
|
|
|
|
/**
|
|
* This is the main function and the one you should actually be calling.
|
|
* There are several variables you should be aware of an which need
|
|
* special description.
|
|
*
|
|
* $tag_list
|
|
* ----------
|
|
* This is a simple one-dimentional array of strings, except for the
|
|
* very first one. The first member should be einter false or true.
|
|
* In case it's FALSE, the following list will be considered a list of
|
|
* tags that should be explicitly REMOVED from the body, and all
|
|
* others that did not match the list will be allowed. If the first
|
|
* member is TRUE, then the list is the list of tags that should be
|
|
* explicitly ALLOWED -- any tag not matching this list will be
|
|
* discarded.
|
|
*
|
|
* Examples:
|
|
* $tag_list = Array(
|
|
* false,
|
|
* "blink",
|
|
* "link",
|
|
* "object",
|
|
* "meta",
|
|
* "marquee",
|
|
* "html"
|
|
* );
|
|
*
|
|
* This will allow all tags except for blink, link, object, meta, marquee,
|
|
* and html.
|
|
*
|
|
* $tag_list = Array(
|
|
* true,
|
|
* "b",
|
|
* "a",
|
|
* "i",
|
|
* "img",
|
|
* "strong",
|
|
* "em",
|
|
* "p"
|
|
* );
|
|
*
|
|
* This will remove all tags from the body except b, a, i, img, strong, em and
|
|
* p.
|
|
*
|
|
* $rm_tags_with_content
|
|
* ---------------------
|
|
* This is a simple one-dimentional array of strings, which specifies the
|
|
* tags to be removed with any and all content between the beginning and
|
|
* the end of the tag.
|
|
* Example:
|
|
* $rm_tags_with_content = Array(
|
|
* "script",
|
|
* "style",
|
|
* "applet",
|
|
* "embed"
|
|
* );
|
|
*
|
|
* This will remove the following structure:
|
|
* <script>
|
|
* window.alert("Isn't cross-site-scripting fun?!");
|
|
* </script>
|
|
*
|
|
* $self_closing_tags
|
|
* ------------------
|
|
* This is a simple one-dimentional array of strings, which specifies which
|
|
* tags contain no content and should not be forcefully closed if this option
|
|
* is turned on (see further).
|
|
* Example:
|
|
* $self_closing_tags = Array(
|
|
* "img",
|
|
* "br",
|
|
* "hr",
|
|
* "input"
|
|
* );
|
|
*
|
|
* $force_tag_closing
|
|
* ------------------
|
|
* Set it to true to forcefully close any tags opened within the document.
|
|
* This is good if you want to take care of people who like to screw up
|
|
* the pages by leaving unclosed tags like <a>, <b>, <i>, etc.
|
|
*
|
|
* $rm_attnames
|
|
* -------------
|
|
* Now we come to parameters that are more obscure. This parameter is
|
|
* a nested array which is used to specify which attributes should be
|
|
* removed. It goes like so:
|
|
*
|
|
* $rm_attnames = Array(
|
|
* "PCRE regex to match tag name" =>
|
|
* Array(
|
|
* "PCRE regex to match attribute name"
|
|
* )
|
|
* );
|
|
*
|
|
* Example:
|
|
* $rm_attnames = Array(
|
|
* "|.*|" =>
|
|
* Array(
|
|
* "|target|i",
|
|
* "|^on.*|i"
|
|
* )
|
|
* );
|
|
*
|
|
* This will match all attributes (.*), and specify that all attributes
|
|
* named "target" and starting with "on" should be removed. This will take
|
|
* care of the following problem:
|
|
* <em onmouseover="window.alert('muahahahaha')">
|
|
* The "onmouseover" will be removed.
|
|
*
|
|
* $bad_attvals
|
|
* ------------
|
|
* This is where it gets ugly. This is a nested array with many levels.
|
|
* It goes like so:
|
|
*
|
|
* $bad_attvals = Array(
|
|
* "pcre regex to match tag name" =>
|
|
* Array(
|
|
* "pcre regex to match attribute name" =>
|
|
* Array(
|
|
* "pcre regex to match attribute value"
|
|
* )
|
|
* Array(
|
|
* "pcre regex replace a match from above with"
|
|
* )
|
|
* )
|
|
* );
|
|
*
|
|
* An extensive example:
|
|
*
|
|
* $bad_attvals = Array(
|
|
* "|.*|" =>
|
|
* Array(
|
|
* "/^src|background|href|action/i" =>
|
|
* Array(
|
|
* Array(
|
|
* "/^([\'\"])\s*\S+script\s*:.*([\'\"])/si"
|
|
* ),
|
|
* Array(
|
|
* "\\1http://veryfunny.com/\\2"
|
|
* )
|
|
* ),
|
|
* "/^style/i" =>
|
|
* Array(
|
|
* Array(
|
|
* "/expression/si",
|
|
* "/url\(([\'\"])\s*https*:.*([\'\"])\)/si",
|
|
* "/url\(([\'\"])\s*\S+script:.*([\'\"])\)/si"
|
|
* ),
|
|
* Array(
|
|
* "idiocy",
|
|
* "url(\\1http://veryfunny.com/\\2)",
|
|
* "url(\\1http://veryfynny.com/\\2)"
|
|
* )
|
|
* )
|
|
* )
|
|
* );
|
|
*
|
|
* This will take care of nearly all known cross-site scripting exploits,
|
|
* plus some (see my filter sample at
|
|
* http://www.mricon.com/html/phpfilter.html for a working version).
|
|
*
|
|
* $add_attr_to_tag
|
|
* ----------------
|
|
* This is a useful little feature which lets you add attributes to
|
|
* certain tags. It is a nested array as well, but not at all like
|
|
* the previous one. It goes like so:
|
|
*
|
|
* $add_attr_to_tag = Array(
|
|
* "PCRE regex to match tag name" =>
|
|
* Array(
|
|
* "attribute name"=>'"attribute value"'
|
|
* )
|
|
* );
|
|
*
|
|
* Note: don't forget quotes around attribute value.
|
|
*
|
|
* Example:
|
|
*
|
|
* $add_attr_to_tag = Array(
|
|
* "/^a$/si" =>
|
|
* Array(
|
|
* 'target'=>'"_new"'
|
|
* )
|
|
* );
|
|
*
|
|
* This will change all <a> tags and add target="_new" to them so all links
|
|
* open in a new window.
|
|
*
|
|
*
|
|
*
|
|
* @param $body the string with HTML you wish to filter
|
|
* @param $tag_list see description above
|
|
* @param $rm_tags_with_content see description above
|
|
* @param $self_closing_tags see description above
|
|
* @param $force_tag_closing see description above
|
|
* @param $rm_attnames see description above
|
|
* @param $bad_attvals see description above
|
|
* @param $add_attr_to_tag see description above
|
|
* @return sanitized html safe to show on your pages.
|
|
*/
|
|
function sanitize($body,
|
|
$tag_list,
|
|
$rm_tags_with_content,
|
|
$self_closing_tags,
|
|
$force_tag_closing,
|
|
$rm_attnames,
|
|
$bad_attvals,
|
|
$add_attr_to_tag
|
|
){
|
|
$me = 'sanitize';
|
|
/**
|
|
* Normalize rm_tags and rm_tags_with_content.
|
|
*/
|
|
@array_walk($rm_tags, 'casenormalize');
|
|
@array_walk($rm_tags_with_content, 'casenormalize');
|
|
@array_walk($self_closing_tags, 'casenormalize');
|
|
/**
|
|
* See if tag_list is of tags to remove or tags to allow.
|
|
* false means remove these tags
|
|
* true means allow these tags
|
|
*/
|
|
$rm_tags = array_shift($tag_list);
|
|
$curpos = 0;
|
|
$open_tags = Array();
|
|
#$trusted = "<!-- begin sanitized html -->\n";
|
|
$trusted = "";
|
|
$skip_content = false;
|
|
/**
|
|
* Take care of netscape's stupid javascript entities like
|
|
* &{alert('boo')};
|
|
*/
|
|
$body = preg_replace('/&(\{.*?\};)/si', '&\\1', $body);
|
|
$this->spew("$me: invoking the loop\n");
|
|
while (($curtag = $this->getnxtag($body, $curpos)) != FALSE){
|
|
list($tagname, $attary, $tagtype, $lt, $gt) = $curtag;
|
|
$this->spew("$me: grabbing free-standing content\n");
|
|
$free_content = substr($body, $curpos, $lt - $curpos);
|
|
$this->spew("$me: " . strlen($free_content) . " chars grabbed\n");
|
|
if ($skip_content == false){
|
|
$this->spew("$me: appending free content to trusted.\n");
|
|
$trusted .= $free_content;
|
|
} else {
|
|
$this->spew("$me: Skipping free content.\n");
|
|
}
|
|
if ($tagname != FALSE){
|
|
$this->spew("$me: tagname is '$tagname'\n");
|
|
if ($tagtype == 2){
|
|
$this->spew("$me: This is a closing tag\n");
|
|
if ($skip_content == $tagname){
|
|
/**
|
|
* Got to the end of tag we needed to remove.
|
|
*/
|
|
$this->spew("$me: Finished removing tag with content\n");
|
|
$tagname = false;
|
|
$skip_content = false;
|
|
} else {
|
|
if ($skip_content == false){
|
|
if (isset($open_tags{$tagname}) &&
|
|
$open_tags{$tagname} > 0){
|
|
$this->spew("$me: popping '$tagname' from open_tags\n");
|
|
$open_tags{$tagname}--;
|
|
} else {
|
|
$this->spew("$me: '$tagname' was never opened\n");
|
|
$this->spew("$me: removing\n");
|
|
$tagname = false;
|
|
}
|
|
} else {
|
|
$this->spew("$me: Skipping this tag\n");
|
|
}
|
|
}
|
|
} else {
|
|
/**
|
|
* $rm_tags_with_content
|
|
*/
|
|
if ($skip_content == false){
|
|
/**
|
|
* See if this is a self-closing type and change
|
|
* tagtype appropriately.
|
|
*/
|
|
if ($tagtype == 1
|
|
&& in_array($tagname, $self_closing_tags)){
|
|
$this->spew("$me: Self-closing tag. Changing tagtype.\n");
|
|
$tagtype = 3;
|
|
}
|
|
/**
|
|
* See if we should skip this tag and any content
|
|
* inside it.
|
|
*/
|
|
if ($tagtype == 1 && in_array($tagname, $rm_tags_with_content)){
|
|
$this->spew("$me: removing this tag with content\n");
|
|
$skip_content = $tagname;
|
|
} else {
|
|
if (($rm_tags == false && in_array($tagname, $tag_list)) ||
|
|
($rm_tags == true && !in_array($tagname, $tag_list))){
|
|
$this->spew("$me: Removing this tag.\n");
|
|
$tagname = false;
|
|
} else {
|
|
if ($tagtype == 1){
|
|
$this->spew("$me: adding '$tagname' to open_tags\n");
|
|
if (isset($open_tags{$tagname})){
|
|
$open_tags{$tagname}++;
|
|
} else {
|
|
$open_tags{$tagname} = 1;
|
|
}
|
|
}
|
|
/**
|
|
* This is where we run other checks.
|
|
*/
|
|
if (is_array($attary) && sizeof($attary) > 0){
|
|
$attary = $this->fixatts($tagname,
|
|
$attary,
|
|
$rm_attnames,
|
|
$bad_attvals,
|
|
$add_attr_to_tag);
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
$this->spew("$me: Skipping this tag\n");
|
|
}
|
|
}
|
|
if ($tagname != false && $skip_content == false){
|
|
$this->spew("$me: Appending tag to trusted.\n");
|
|
$trusted .= $this->tagprint($tagname, $attary, $tagtype);
|
|
}
|
|
} else {
|
|
$this->spew("$me: Removing invalid tag\n");
|
|
}
|
|
$curpos = $gt + 1;
|
|
}
|
|
$this->spew("$me: Appending any leftover content\n");
|
|
$trusted .= substr($body, $curpos, strlen($body) - $curpos);
|
|
if ($force_tag_closing == true){
|
|
foreach ($open_tags as $tagname=>$opentimes){
|
|
while ($opentimes > 0){
|
|
$this->spew("$me: '$tagname' left open. Closing by force.\n");
|
|
$trusted .= '</' . $tagname . '>';
|
|
$opentimes--;
|
|
}
|
|
}
|
|
$trusted .= "\n";
|
|
}
|
|
# $trusted .= "<!-- end sanitized html -->\n";
|
|
$trusted .= "";
|
|
return $trusted;
|
|
}
|
|
// class end
|
|
}
|
|
?>
|