<?php
/**
* htmlfilter.inc
* ---------------
* This set of functions allows you to filter html in order to remove
* any malicious tags from it. Useful in cases when you need to filter
* user input for any cross-site-scripting attempts.
*
* Copyright (C) 2002-2004 by Duke University
*
* This program is free 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.
*
* @Author Konstantin Riabitsev <icon@linux.duke.edu>
* @Version 1.1 ($Date: 2004/01/27 19:57:59 $)
*/
/**
* This is a debugging function used throughout the code. To enable
* debugging you have to specify a global variable called "debug" before
* calling sanitize() and set it to true.
*
* Note: Although insignificantly, debugging does slow you down even
* when $debug is set to false. If you wish to get rid of all
* debugging calls, run the following command:
*
* fgrep -v 'spew("' htmlfilter.inc > htmlfilter.inc.new
*
* htmlfilter.inc.new will contain no debugging calls.
*
* @param $message A string with the message to output.
* @return void.
*/
function spew($message) {
global $debug;
if ($debug == true) {
echo "$message";
}
}
/**
* This function returns the final tag out of the tag name, an array
* of attributes, and the type of the tag. This function is called by
* sanitize internally.
*
* @param $tagname the name of the tag.
* @param $attary the array of attributes and their values
* @param $tagtype The type of the tag (see in comments).
* @return a string with the final tag representation.
*/
function tagprint($tagname, $attary, $tagtype) {
$me = 'tagprint';
if ($tagtype == 2) {
$fulltag = '</' . $tagname . '>';
} else {
$fulltag = '<' . $tagname;
if (is_array($attary) && sizeof($attary)) {
$atts = Array();
while (list($attname, $attvalue) = each($attary)) {
array_push($atts, "$attname=$attvalue");
}
$fulltag .= ' ' . join(' ', $atts);
}
if ($tagtype == 3) {
$fulltag .= ' /';
}
$fulltag .= '>';
}
spew("$me: $fulltag\n");
return $fulltag;
}
/**
* A small helper function to use with array_walk. Modifies a by-ref
* value and makes it lowercase.
*
* @param $val a value passed by-ref.
* @return void since it modifies a by-ref value.
*/
function casenormalize(&$val) {
$val = strtolower($val);
}
/**
* This function skips any whitespace from the current position within
* a string and to the next non-whitespace value.
*
* @param $body the string
* @param $offset the offset within the string where we should start
* looking for the next non-whitespace character.
* @return the location within the $body where the next
* non-whitespace char is located.
*/
function skipspace($body, $offset) {
$me = 'skipspace';
preg_match('/^(\s*)/s', substr($body, $offset), $matches);
if (sizeof($matches{1})) {
$count = strlen($matches{1});
spew("$me: skipped $count chars\n");
$offset += $count;
}
return $offset;
}
/**
* This function looks for the next character within a string. It's
* really just a glorified "strpos", except it catches the failures
* nicely.
*
* @param $body The string to look for needle in.
* @param $offset Start looking from this position.
* @param $needle The character/string to look for.
* @return location of the next occurance of the needle, or
* strlen($body) if needle wasn't found.
*/
function findnxstr($body, $offset, $needle) {
$me = 'findnxstr';
$pos = strpos($body, $needle, $offset);
if ($pos === FALSE) {
$pos = strlen($body);
spew("$me: end of body reached\n");
}
spew("$me: '$needle' found at pos $pos\n");
return $pos;
}
/**
* This function takes a PCRE-style regexp and tries to match it
* within the string.
*
* @param $body The string to look for needle in.
* @param $offset Start looking from here.
* @param $reg A PCRE-style regex to match.
* @return Returns a false if no matches found, or an array
* with the following members:
* - integer with the location of the match within $body
* - string with whatever content between offset and the match
* - string with whatever it is we matched
*/
function findnxreg($body, $offset, $reg) {
$me = 'findnxreg';
$matches = Array();
$retarr = Array();
$preg_rule = '%^(.*?)(' . $reg . ')%s';
preg_match($preg_rule, substr($body, $offset), $matches);
if (!isset($matches{0})) {
spew("$me: No matches found.\n");
$retarr = false;
} else {
$retarr{0} = $offset + strlen($matches{1});
$retarr{1} = $matches{1};
$retarr{2} = $matches{2};
spew("$me: '$reg' found at pos $offset matching '".$matches{2}."'\n");
}
return $retarr;
}
/**
* This function looks for the next tag.
*
* @param $body String where to look for the next tag.
* @param $offset Start looking from here.
* @return false if no more tags exist in the body, or
* an array with the following members:
* - string with the name of the tag
* - array with attributes and their values
* - integer with tag type (1, 2, or 3)
* - integer where the tag starts (starting "<")
* - integer where the tag ends (ending ">")
* first three members will be false, if the tag is invalid.
*/
function getnxtag($body, $offset) {
$me = 'getnxtag';
if ($offset > strlen($body)) {
spew("$me: Past the end of body\n");
return false;
}
$lt = findnxstr($body, $offset, '<');
if ($lt == strlen($body)) {
spew("$me: No more tags found!\n");
return false;
}
/**
* We are here:
* blah blah <tag attribute="value">
* \---------^
*/
spew("$me: Found '<' at pos $lt\n");
$pos = skipspace($body, $lt + 1);
if ($pos >= strlen($body)) {
spew("$me: End of body reached.\n");
return Array(false, false, false, $lt, strlen($body));
}
/**
* There are 3 kinds of tags:
* 1. Opening tag, e.g.:
* <a href="blah">
* 2. Closing tag, e.g.:
* </a>
* 3. XHTML-style content-less tag, e.g.:
* <img src="blah"/>
*/
$tagtype = false;
switch (substr($body, $pos, 1)) {
case '/':
spew("$me: This is a closing tag (type 2)\n");
$tagtype = 2;
$pos++;
break;
case '!':
/**
* A comment or an SGML declaration.
*/
if (substr($body, $pos+1, 2) == '--') {
spew("$me: A comment found. Stripping.\n");
$gt = strpos($body, '-->', $pos);
if ($gt === false) {
$gt = strlen($body);
} else {
$gt += 2;
}
return Array(false, false, false, $lt, $gt);
} else {
spew("$me: An SGML declaration found. Stripping.\n");
$gt = findnxstr($body, $pos, '>');
return Array(false, false, false, $lt, $gt);
}
break;
default:
/**
* Assume tagtype 1 for now. If it's type 3, we'll switch values
* later.
*/
$tagtype = 1;
break;
}
$tag_start = $pos;
$tagname = '';
/**
* Look for next [\W-_], which will indicate the end of the tag name.
*/
$regary = findnxreg($body, $pos, '[^\w\-_]');
if ($regary == false){
spew("$me: End of body reached while analyzing tag name\n");
return Array(false, false, false, $lt, strlen($body));
}
list($pos, $tagname, $match) = $regary;
$tagname = strtolower($tagname);
/**
* $match can be either of these:
* '>' indicating the end of the tag entirely.
* '\s' indicating the end of the tag name.
* '/' indicating that this is type-3 xhtml tag.
*
* Whatever else we find there indicates an invalid tag.
*/
switch ($match) {
case '/':
/**
* This is an xhtml-style tag with a closing / at the
* end, like so: <img src="blah"/>. Check if it's followed
* by the closing bracket. If not, then this tag is invalid
*/
if (substr($body, $pos, 2) == '/>') {
spew("$me: XHTML-style tag found.\n");
$pos++;
spew("$me: Setting tagtype to 3\n");
$tagtype = 3;
} else {
spew("$me: Found invalid character '/'.\n");
$gt = findnxstr($body, $pos, '>');
spew("$me: Tag is invalid. Returning.\n");
$retary = Array(false, false, false, $lt, $gt);
return $retary;
}
case '>':
spew("$me: End of tag found at $pos\n");
spew("$me: Tagname is '$tagname'\n");
spew("$me: This tag has no attributes\n");
return Array($tagname, false, $tagtype, $lt, $pos);
break;
default:
/**
* Check if it's whitespace
*/
if (preg_match('/\s/', $match)){
spew("$me: Tagname is '$tagname'\n");
} else {
/**
* This is an invalid tag! Look for the next closing ">".
*/
spew("$me: Invalid characters found in tag name: $match\n");
$gt = findnxstr($body, $lt, '>');
return Array(false, false, false, $lt, $gt);
}
}
/**
* At this point we're here:
* <tagname attribute='blah'>
* \-------^
*
* At this point we loop in order to find all attributes.
*/
$attname = '';
$atttype = false;
$attary = Array();
while ($pos <= strlen($body)) {
$pos = skipspace($body, $pos);
if ($pos == strlen($body)) {
/**
* Non-closed tag.
*/
spew("$me: End of body reached before end of tag. Discarding.\n");
return Array(false, false, false, $lt, $pos);
}
/**
* See if we arrived at a ">" or "/>", which means that we reached
* the end of the tag.
*/
$matches = Array();
preg_match('%^(\s*)(>|/>)%s', substr($body, $pos), $matches);
if (isset($matches{0}) && $matches{0}) {
/**
* Yep. So we did.
*/
spew("$me: Arrived at the end of the tag.\n");
$pos += strlen($matches{1});
if ($matches{2} == '/>') {
$tagtype = 3;
$pos++;
}
return Array($tagname, $attary, $tagtype, $lt, $pos);
}
/**
* There are several types of attributes, with optional
* [:space:] between members.
* Type 1:
* attrname[:space:]=[:space:]'CDATA'
* Type 2:
* attrname[:space:]=[:space:]"CDATA"
* Type 3:
* attr[:space:]=[:space:]CDATA
* Type 4:
* attrname
*
* We leave types 1 and 2 the same, type 3 we check for
* '"' and convert to """ if needed, then wrap in
* double quotes. Type 4 we convert into:
* attrname="yes".
*/
$regary = findnxreg($body, $pos, '[^\w\-_]');
if ($regary == false) {
/**
* Looks like body ended before the end of tag.
*/
spew("$me: End of body found before end of tag.\n");
spew("$me: Invalid, returning\n");
return Array(false, false, false, $lt, strlen($body));
}
list($pos, $attname, $match) = $regary;
$attname = strtolower($attname);
spew("$me: Attribute '$attname' found\n");
/**
* We arrived at the end of attribute name. Several things possible
* here:
* '>' means the end of the tag and this is attribute type 4
* '/' if followed by '>' means the same thing as above
* '\s' means a lot of things -- look what it's followed by.
* anything else means the attribute is invalid.
*/
switch($match) {
case '/':
/**
* This is an xhtml-style tag with a closing / at the
* end, like so: <img src="blah"/>. Check if it's followed
* by the closing bracket. If not, then this tag is invalid
*/
if (substr($body, $pos, 2) == '/>') {
spew("$me: This is an xhtml-style tag.\n");
$pos++;
spew("$me: Setting tagtype to 3\n");
$tagtype = 3;
} else {
spew("$me: Found invalid character '/'.\n");
$gt = findnxstr($body, $pos, '>');
spew("$me: Tag is invalid. Returning.\n");
$retary = Array(false, false, false, $lt, $gt);
return $retary;
}
case '>':
spew("$me: found type 4 attribute.\n");
spew("$me: Additionally, end of tag found at $pos\n");
spew("$me: Attname is '$attname'\n");
spew("$me: Setting attvalue to 'yes'\n");
$attary{$attname} = '"yes"';
return Array($tagname, $attary, $tagtype, $lt, $pos);
break;
default:
/**
* Skip whitespace and see what we arrive at.
*/
$pos = skipspace($body, $pos);
$char = substr($body, $pos, 1);
/**
* Two things are valid here:
* '=' means this is attribute type 1 2 or 3.
* \w means this was attribute type 4.
* anything else we ignore and re-loop. End of tag and
* invalid stuff will be caught by our checks at the beginning
* of the loop.
*/
if ($char == '=') {
spew("$me: Attribute type 1, 2, or 3 found.\n");
$pos++;
$pos = skipspace($body, $pos);
/**
* Here are 3 possibilities:
* "'" attribute type 1
* '"' attribute type 2
* everything else is the content of tag type 3
*/
$quot = substr($body, $pos, 1);
if ($quot == '\'') {
spew("$me: In fact, this is attribute type 1\n");
spew("$me: looking for closing quote\n");
$regary = findnxreg($body, $pos+1, '\'');
if ($regary == false) {
spew("$me: end of body reached before end of val\n");
spew("$me: Returning\n");
return Array(false, false, false, $lt, strlen($body));
}
list($pos, $attval, $match) = $regary;
spew("$me: Attvalue is '$attval'\n");
$pos++;
$attary{$attname} = '\'' . $attval . '\'';
} else if ($quot == '"') {
spew("$me: In fact, this is attribute type 2\n");
spew("$me: looking for closing quote\n");
$regary = findnxreg($body, $pos+1, '\"');
if ($regary == false) {
spew("$me: end of body reached before end of val\n");
spew("$me: Returning\n");
return Array(false, false, false, $lt, strlen($body));
}
list($pos, $attval, $match) = $regary;
spew("$me: Attvalue is \"$attval\"\n");
$pos++;
$attary{$attname} = '"' . $attval . '"';
} else {
spew("$me: This looks like attribute type 3\n");
/**
* These are hateful. Look for \s, or >.
*/
spew("$me: Looking for end of attval\n");
$regary = findnxreg($body, $pos, '[\s>]');
if ($regary == false) {
spew("$me: end of body reached before end of val\n");
spew("$me: Returning\n");
return Array(false, false, false, $lt, strlen($body));
}
list($pos, $attval, $match) = $regary;
/**
* If it's ">" it will be caught at the top.
*/
spew("$me: translating '\"' into "\n");
$attval = preg_replace('/\"/s', '"', $attval);
spew("$me: wrapping in quotes\n");
$attary{$attname} = '"' . $attval . '"';
}
} else if (preg_match('|[\w/>]|', $char)) {
/**
* That was attribute type 4.
*/
spew("$me: attribute type 4 found.\n");
spew("$me: Setting value to 'yes'\n");
$attary{$attname} = '"yes"';
} else {
/**
* An illegal character. Find next '>' and return.
*/
spew("$me: illegal character '$char' found.\n");
spew("$me: returning\n");
$gt = findnxstr($body, $pos, '>');
return Array(false, false, false, $lt, $gt);
}
}
}
/**
* The fact that we got here indicates that the tag end was never
* found. Return invalid tag indication so it gets stripped.
*/
spew("$me: No tag end found\n");
return Array(false, false, false, $lt, strlen($body));
}
/**
* Translates entities into literal values so they can be checked.
*
* @param $attvalue the by-ref value to check.
* @param $regex the regular expression to check against.
* @param $hex whether the entites are hexadecimal.
* @return True or False depending on whether there were matches.
*/
function deent(&$attvalue, $regex, $hex=false) {
$me = 'deent';
spew("$me: matching '$regex' against: $attvalue\n");
$ret_match = false;
preg_match_all($regex, $attvalue, $matches);
if (is_array($matches) && sizeof($matches[0]) > 0) {
spew("$me: found " . sizeof($matches[0]) . " matches\n");
$repl = Array();
for ($i = 0; $i < sizeof($matches[0]); $i++) {
$numval = $matches[1][$i];
spew("$me: numval is $numval\n");
if ($hex) {
$numval = hexdec($numval);
spew("$me: hex! Numval is now $numval\n");
}
$repl{$matches[0][$i]} = chr($numval);
}
$attvalue = strtr($attvalue, $repl);
spew("$me: attvalue after translation: $attvalue\n");
return true;
} else {
spew("$me: no matches! Returning false.\n");
return false;
}
}
/**
* 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 $attvalue A string to run entity check against.
* @return Nothing, modifies a reference value.
*/
function defang(&$attvalue) {
$me = 'defang';
/**
* Skip this if there aren't ampersands or backslashes.
*/
spew("$me: Checking '$attvalue' for suspicious content\n");
if (strpos($attvalue, '&') === false
&& strpos($attvalue, '\\') === false)
{
spew("$me: no suspicious content found, returning.\n");
return;
}
$m = false;
do {
$m = false;
$m = $m || deent($attvalue, '/\�*(\d+);*/s');
$m = $m || deent($attvalue, '/\�*((\d|[a-f])+);*/si', true);
$m = $m || deent($attvalue, '/\\\\(\d+)/s', true);
spew("$me: m=$m\n");
} while ($m == true);
$attvalue = stripslashes($attvalue);
spew("$me: translated into: $attvalue\n");
}
/**
* Kill any tabs, newlines, or carriage returns. Our friends the
* makers of the browser with 95% market value decided that it'd
* be funny to make "java[tab]script" be just as good as "javascript".
*
* @param attvalue The attribute value before extraneous spaces removed.
* @return attvalue Nothing, modifies a reference value.
*/
function unspace(&$attvalue){
$me = 'unspace';
if (strcspn($attvalue, "\t\r\n\0 ") != strlen($attvalue)) {
spew("$me: Killing whitespace.\n");
$attvalue = str_replace(Array("\t", "\r", "\n", "\0", " "),
Array('', '', ''), $attvalue);
}
spew("$me: after unspace: $attvalue\n");
}
/**
* 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) {
$me = 'fixatts';
spew("$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, $attname)) {
spew("$me: Attribute '$attname' defined as bad.\n");
spew("$me: Removing.\n");
unset($attary{$attname});
continue;
}
}
}
}
/**
* Remove any backslashes, entities, or extraneous whitespace.
*/
defang($attvalue);
unspace($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 != $attvalue) {
spew("$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, $addattary);
spew("$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) {
$me = 'sanitize';
/**
* Normalize rm_tags and rm_tags_with_content.
*/
@array_walk($tag_list, '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";
$skip_content = false;
/**
* Take care of netscape's stupid javascript entities like
* &{alert('boo')};
*/
$body = preg_replace('/&(\{.*?\};)/si', '&\\1', $body);
spew("$me: invoking the loop\n");
while (($curtag = getnxtag($body, $curpos)) != FALSE) {
list($tagname, $attary, $tagtype, $lt, $gt) = $curtag;
spew("$me: grabbing free-standing content\n");
$free_content = substr($body, $curpos, $lt - $curpos);
spew("$me: " . strlen($free_content) . " chars grabbed\n");
if ($skip_content == false) {
spew("$me: appending free content to trusted.\n");
$trusted .= $free_content;
} else {
spew("$me: Skipping free content.\n");
}
if ($tagname != FALSE) {
spew("$me: tagname is '$tagname'\n");
if ($tagtype == 2) {
spew("$me: This is a closing tag\n");
if ($skip_content == $tagname) {
/**
* Got to the end of tag we needed to remove.
*/
spew("$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) {
spew("$me: popping '$tagname' from open_tags\n");
$open_tags{$tagname}--;
} else {
spew("$me: '$tagname' was never opened\n");
spew("$me: removing\n");
$tagname = false;
}
} else {
spew("$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, $self_closing_tags)) {
spew("$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, $rm_tags_with_content)) {
spew("$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, $tag_list)))
{
spew("$me: Removing this tag.\n");
$tagname = false;
} else {
if ($tagtype == 1) {
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) {
$attary = fixatts($tagname, $attary, $rm_attnames, $bad_attvals, $add_attr_to_tag);
}
}
}
} else {
spew("$me: Skipping this tag\n");
}
}
if ($tagname != false && $skip_content == false) {
spew("$me: Appending tag to trusted.\n");
$trusted .= tagprint($tagname, $attary, $tagtype);
}
} else {
spew("$me: Removing invalid tag\n");
}
$curpos = $gt + 1;
}
spew("$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 ($opentimes > 0) {
spew("$me: '$tagname' left open. Closing by force.\n");
$trusted .= '</' . $tagname . '>';
$opentimes--;
}
}
$trusted .= "\n";
}
$trusted .= "<!-- end sanitized html -->\n";
return $trusted;
}
?>