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<?php
/**
* @package Habari
*
*/

/**
* Input filtering functions.
*
*/
class InputFilter
{
/**
* Allowed elements.
*/
private static $whitelist_elements = array(
// http://www.w3.org/TR/html4/struct/global.html#h-7.5.4
'div', 'span',
// http://www.w3.org/TR/html4/struct/links.html#h-12.2
'a',
// http://www.w3.org/TR/html4/struct/text.html#h-9.2.1
'strong', 'em', 'code', 'kbd', 'dfn', 'samp', 'var', 'cite', 'abbr', 'acronym',
// http://www.w3.org/TR/html4/struct/text.html#h-9.2.2
'blockquote', 'q',
// http://www.w3.org/TR/html4/struct/text.html#h-9.2.3
'sub', 'sup',
// http://www.w3.org/TR/html4/struct/text.html#h-9.3.1
'p',
// http://www.w3.org/TR/html4/struct/text.html#h-9.3.2.1
'br',
// http://www.w3.org/TR/html4/struct/text.html#h-9.3.4
'pre',
// http://www.w3.org/TR/html4/struct/text.html#h-9.4
'ins', 'del',
// http://www.w3.org/TR/html4/struct/lists.html#h-10.2
'ol', 'ul', 'li',
// http://www.w3.org/TR/html4/struct/lists.html#h-10.3
'dl', 'dt', 'dd',
// http://www.w3.org/TR/html4/present/graphics.html#h-15.2.1
'b', 'i', 'u', 's', 'tt',
// http://www.w3.org/TR/html4/struct/global.html#h-7.5.5
'h1', 'h2', 'h3', 'h4', 'h5', 'h6',
// http://www.w3.org/TR/html4/struct/global.html#h-7.5.6
'address',
// http://www.w3.org/TR/html4/struct/dirlang.html#h-8.2.4
'bdo',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.1
'table',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.2
'caption',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.3
'thead', 'tfoot', 'tbody',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.4
'colgroup', 'col',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.5
'tr',
// http://www.w3.org/TR/html4/struct/tables.html#h-11.2.6
'th', 'td',
// http://www.w3.org/TR/html4/struct/objects.html#h-13.2
'img',
// http://www.w3.org/TR/html4/struct/objects.html#h-13.6.1
'map', 'area',
// http://www.w3.org/TR/html4/present/graphics.html#h-15.2.1 (the non-deprecated ones)
'tt', 'i', 'b', 'big', 'small',
// http://www.w3.org/TR/html4/present/graphics.html#h-15.3
'hr',
// http://www.w3.org/TR/html4/present/frames.html#h-16.2.1
'frameset',
// http://www.w3.org/TR/html4/present/frames.html#h-16.2.2
'frame',
// http://www.w3.org/TR/html4/present/frames.html#h-16.4.1
'noframes',
// http://www.w3.org/TR/html4/present/frames.html#h-16.5
'iframe',

);

/**
* Allowed attributes and values.
*/
private static $whitelist_attributes = array(
// attributes that are valid for ALL elements (a subset of coreattrs)
// elements that only take coreattrs don't need to be listed separately
'*' => array(
'lang' => 'language-code',
'xml:lang' => 'language-code', // this is our xhtml support... all of it
'dir' => array( 'ltr', 'rtl', ),
'title' => 'text',
),
// http://www.w3.org/TR/html4/struct/links.html#h-12.2
'a' => array( 'href' => 'uri', ),
// http://www.w3.org/TR/html4/struct/text.html#h-9.4
'ins' => array( 'cite' => 'uri', 'datetime' => 'datetime', ),
'del' => array( 'cite' => 'uri', 'datetime' => 'datetime', ),
// http://www.w3.org/TR/html4/struct/text.html#h-9.2.2
'blockquote' => array( 'cite' => 'uri', ),
'q' => array( 'cite' => 'uri', ),
'img' => array( 'src' => 'uri', 'alt' => 'text' ),
);

/**
* #EMPTY elements.
*/
private static $elements_empty = array(
'img',
);

/**
* Protocols that are ok for use in URIs.
*/
private static $whitelist_protocols = array(
'http', 'https', 'ftp', 'mailto', 'irc', 'news', 'nntp', 'callto', 'rtsp', 'mms', 'svn',
);

/**
* List of all defined named character entities in HTML 4.01 and XHTML.
*/
private static $character_entities = array(
'nbsp', 'iexcl', 'cent', 'pound', 'curren', 'yen', 'brvbar', 'sect', 'uml',
'copy', 'ordf', 'laquo', 'not', 'shy', 'reg', 'macr', 'deg', 'plusmn',
'sup2', 'sup3', 'acute', 'micro', 'para', 'middot', 'cedil', 'sup1', 'ordm',
'raquo', 'frac14', 'frac12', 'frac34', 'iquest', 'Agrave', 'Aacute', 'Acirc',
'Atilde', 'Auml', 'Aring', 'AElig', 'Ccedil', 'Egrave', 'Eacute', 'Ecirc',
'Euml', 'Igrave', 'Iacute', 'Icirc', 'Iuml', 'ETH', 'Ntilde', 'Ograve',
'Oacute', 'Ocirc', 'Otilde', 'Ouml', 'times', 'Oslash', 'Ugrave', 'Uacute',
'Ucirc', 'Uuml', 'Yacute', 'THORN', 'szlig', 'agrave', 'aacute', 'acirc',
'atilde', 'auml', 'aring', 'aelig', 'ccedil', 'egrave', 'eacute', 'ecirc',
'euml', 'igrave', 'iacute', 'icirc', 'iuml', 'eth', 'ntilde', 'ograve',
'oacute', 'ocirc', 'otilde', 'ouml', 'divide', 'oslash', 'ugrave', 'uacute',
'ucirc', 'uuml', 'yacute', 'thorn', 'yuml', 'fnof', 'Alpha', 'Beta', 'Gamma',
'Delta', 'Epsilon', 'Zeta', 'Eta', 'Theta', 'Iota', 'Kappa', 'Lambda', 'Mu',
'Nu', 'Xi', 'Omicron', 'Pi', 'Rho', 'Sigma', 'Tau', 'Upsilon', 'Phi', 'Chi',
'Psi', 'Omega', 'alpha', 'beta', 'gamma', 'delta', 'epsilon', 'zeta', 'eta',
'theta', 'iota', 'kappa', 'lambda', 'mu', 'nu', 'xi', 'omicron', 'pi', 'rho',
'sigmaf', 'sigma', 'tau', 'upsilon', 'phi', 'chi', 'psi', 'omega',
'thetasym', 'upsih', 'piv', 'bull', 'hellip', 'prime', 'Prime', 'oline',
'frasl', 'weierp', 'image', 'real', 'trade', 'alefsym', 'larr', 'uarr',
'rarr', 'darr', 'harr', 'crarr', 'lArr', 'uArr', 'rArr', 'dArr', 'hArr',
'forall', 'part', 'exist', 'empty', 'nabla', 'isin', 'notin', 'ni', 'prod',
'sum', 'minus', 'lowast', 'radic', 'prop', 'infin', 'ang', 'and', 'or',
'cap', 'cup', 'int', 'there4', 'sim', 'cong', 'asymp', 'ne', 'equiv', 'le',
'ge', 'sub', 'sup', 'nsub', 'sube', 'supe', 'oplus', 'otimes', 'perp',
'sdot', 'lceil', 'rceil', 'lfloor', 'rfloor', 'lang', 'rang', 'loz',
'spades', 'clubs', 'hearts', 'diams', 'quot', 'amp', 'lt', 'gt', 'OElig',
'oelig', 'Scaron', 'scaron', 'Yuml', 'circ', 'tilde', 'ensp', 'emsp',
'thinsp', 'zwnj', 'zwj', 'lrm', 'rlm', 'ndash', 'mdash', 'lsquo', 'rsquo',
'sbquo', 'ldquo', 'rdquo', 'bdquo', 'dagger', 'Dagger', 'permil', 'lsaquo',
'rsaquo', 'euro',
);

private static $character_entities_re = '';

public static function __static ( ) {
self::$whitelist_elements = Plugins::filter( 'inputfilter_whitelist_elements', self::$whitelist_elements );
self::$whitelist_attributes = Plugins::filter( 'inputfilter_whitelist_attributes', self::$whitelist_attributes );
self::$elements_empty = Plugins::filter( 'inputfilter_elements_empty', self::$elements_empty );
self::$whitelist_protocols = Plugins::filter( 'inputfilter_whitelist_protocols', self::$whitelist_protocols );
self::$character_entities = Plugins::filter( 'inputfilter_character_entities', self::$character_entities );
self::$character_entities_re = Plugins::filter( 'inputfilter_character_entities_re', self::$character_entities_re );
}

/**
* Perform all filtering, return new string.
* @param string $str Input string.
* @return string Filtered output string.
*/
public static function filter( $str )
{
if ( !MultiByte::valid_data( $str ) ) {
return '';
}
else {
do {
$_str = $str;
$str = self::strip_nulls( $str );
$str = self::strip_illegal_entities( $str );
$str = self::filter_html_elements( $str );
} while ( $str != $_str );

return $str;
}
}

/**
* Remove nulls, return new string.
* @param string $str Input string.
* @return string Filtered output string.
*/
public static function strip_nulls( $str )
{
$str = str_replace( '\0', '', $str );

return $str;
}

/**
* Callback function for strip_illegal_entities, do not use.
* @access private
* @param array $m matches
*/
public static function _validate_entity( $m )
{
$is_valid = false;

/**
* valid entity references have the form
* /&named([;<\n\r])/
* for named entities, or
* /&#(\d{1,5}|[xX][0-9a-fA-F]{1,4})([;<\n\r])/
* for numeric character references
*/

$e = trim( $m[1] );
$r = $m[2];
if ( $r == ';' ) {
$r = '';
}

if ( $e{0} == '#' ) {
$e = strtolower( $e );
if ( $e{1} == 'x' ) {
$e = hexdec( substr( $e, 2 ) );
}
else {
$e = substr( $e, 1 );
}

// numeric character references may only have values in the range 0-65535 (16 bit)
// we strip null, though, just for kicks
$is_valid = ( intval( $e ) > 0 && intval( $e ) <= 65535 );

if ( $is_valid ) {
// normalize to decimal form
$e = '#' . intval( $e ) . ';';
}
}
else {
if ( self::$character_entities_re == '' ) {
self::$character_entities_re = ';(' . implode( '|', self::$character_entities ) . ');';
}

// named entities must be known
$is_valid = preg_match( self::$character_entities_re, $e, $matches );

// XXX should we map named entities to their numeric equivalents?

if ( $is_valid ) {
// normalize to name and nothing but the name... eh.
$e = $matches[1] . ';';
}
}

return $is_valid ? '&' . $e . $r : '';
}

/**
* Remove illegal entities, return new string.
* @param string $str Input string.
* @return string Filtered output string.
*/
public static function strip_illegal_entities( $str )
{
$str = preg_replace_callback( "/&([^;<\n\r]+)([;<\n\r])/", array( __CLASS__, '_validate_entity' ), $str );

return $str;
}

/**
* This really doesn't belong here. It should also be done much better. This is a nasty, NASTY kludge.
*/
public static function parse_url( $url )
{
// result array
$r = array(
'scheme' => '',
'host' => '',
'port' => '',
'user' => '',
'pass' => '',
'path' => '',
'query' => '',
'fragment' => '',
//
'is_relative' => false,
'is_pseudo' => false,
'is_error' => false,
//
'pseudo_args' => '',
);

// sanitize the url
$sanitized = html_entity_decode( $url, null, 'UTF-8' ); // make double-sure we've converted all entities
$sanitized = filter_var( $sanitized, FILTER_SANITIZE_URL ); // strip everything but ascii, essentially

$sanitized_scheme = parse_url( $sanitized, PHP_URL_SCHEME );

// Use PHP's parse_url to get the basics
$parsed = parse_url( $url );
if ( $parsed == false ) {
$r['is_error'] = true;
return $r;
}
$r = array_merge( $r, $parsed );

// replace the scheme with the one we got from the fully-sanitized string
$r['scheme'] = $sanitized_scheme;

$r['is_pseudo'] = !in_array( $r['scheme'], array( 'http', 'https', '' ) );
$r['is_relative'] = ( $r['host'] == '' && !$r['is_pseudo'] );

if ( $r['is_pseudo'] ) {
$r['pseudo_args'] = $r['path'];
$r['path'] = '';
}

return $r;
}

/**
* Restore a URL separated by a parse_url() call.
* @param $parsed_url array An array as returned by parse_url()
*/
public static function glue_url( $parsed_url )
{
if ( ! is_array( $parsed_url ) ) {
return false;
}

$res = '';
$res .= $parsed_url['scheme'];
if ( $parsed_url['is_pseudo'] || in_array( strtolower( $parsed_url['scheme'] ), array( 'mailto', 'callto' ) ) ) {
$res .= ':';
}
else {
if ( ! $parsed_url['is_relative'] ) {
$res .= '://';
}
}
if ( $parsed_url['is_pseudo'] ) {
$res .= $parsed_url['pseudo_args'];
}
else {
// user[:pass]@
if ( $parsed_url['user'] ) {
$res .= $parsed_url['user'];
if ( $parsed_url['pass'] ) {
$res .= ':' . $parsed_url['pass'];
}
$res .= '@';
}
$res .= $parsed_url['host'];
if ( !empty( $parsed_url['port'] ) ) {
if ( array_key_exists( $parsed_url['scheme'], Utils::scheme_ports() ) && Utils::scheme_ports( $parsed_url['scheme'] ) == $parsed_url['port'] ) {
// default port for this scheme, do nothing
}
else {
$res .= ':' . $parsed_url['port'];
}
}
if ( !empty( $parsed_url['path'] ) ) {
$res .= $parsed_url['path'];
}
else {
$res .= '/';
}
if ( $parsed_url['query'] ) {
$res .= '?' . $parsed_url['query'];
}
if ( $parsed_url['fragment'] ) {
$res .= '#' . $parsed_url['fragment'];
}
}

return $res;
}

private static function check_attr_value( $k, $v, $type )
{
if ( is_array( $type ) ) {
// array of allowed values, exact matches only
return in_array( $v, $type, true );
}
else {
// data type
switch ( $type ) {
case 'uri':
// RfC 2396 <http://www.ietf.org/rfc/rfc2396.txt>
$bits = self::parse_url( $v );
return $bits['is_relative'] || in_array( $bits['scheme'], self::$whitelist_protocols );
break;
case 'language-code':
// RfC 1766 <http://www.ietf.org/rfc/rfc1766.txt>
// Language-Tag = Primary-tag *( "-" Subtag )
// Primary-tag = 1*8ALPHA
// Subtag = 1*8ALPHA
return preg_match( '/^[a-zA-Z]{1,8}(?:-[a-zA-Z]{1,8})*$/i', $v );
break;
case 'text':
// XXX is this sufficient?
return is_string( $v );
break;
case 'datetime':
// <http://www.w3.org/TR/1998/NOTE-datetime-19980827>
// <http://www.w3.org/TR/html4/types.html#h-6.11>
// YYYY-MM-DDThh:mm:ssTZD
return preg_match( '/^[0-9]{4}-[0-1][0-9]-[0-3][0-9]T[0-2][0-9]:[0-5][0-9]:[0-5][0-9](?:Z|[\+-][0-2][0-9]:[0-5][0-9])$/', $v );
break;
default:
Error::raise( _t( 'Unknown attribute type "%s" in %s', array( $type, __CLASS__ ) ) );
return false;
}
}
}

/**
* @todo TODO must build DOM to really properly remove offending elements
* @todo TODO properly filter URLs
*/
public static function filter_html_elements( $str )
{
$tokenizer = new HTMLTokenizer( $str );

// tokenize, baby
$tokens = $tokenizer->parse();

// filter token stream
$filtered = new HTMLTokenSet;
$stack = array();
foreach ( $tokens as $node ) {
switch ( $node['type'] ) {
case HTMLTokenizer::NODE_TYPE_TEXT:
$node['value'] = html_entity_decode( $node['value'], ENT_QUOTES, MultiByte::hab_encoding() );
break;
case HTMLTokenizer::NODE_TYPE_ELEMENT_OPEN:
case HTMLTokenizer::NODE_TYPE_ELEMENT_EMPTY:
// is this element allowed at all?
if ( ! in_array( strtolower( $node['name'] ), self::$whitelist_elements ) ) {
if ( ! in_array( strtolower( $node['name'] ), self::$elements_empty ) ) {
array_push( $stack, $node['name'] );
}
//$node = null; //remove the node completely
// convert the node to text
$node = array(
'type' => HTMLTokenizer::NODE_TYPE_TEXT,
'name' => '#text',
'value' => HTMLTokenSet::token_to_string( $node ),
'attrs' => array(),
);
}
else {
// check attributes
foreach ( $node['attrs'] as $k => $v ) {

$attr_ok = false;

// if the attribute is in the global whitelist and validates
if ( array_key_exists( strtolower( $k ), self::$whitelist_attributes['*'] ) && self::check_attr_value( strtolower( $k ), $v, self::$whitelist_attributes['*'][ strtolower( $k ) ] ) ) {
$attr_ok = true;
}

// if there is a whitelist for this node and this attribute is in that list and it validates
if ( array_key_exists( strtolower( $node['name'] ), self::$whitelist_attributes ) && array_key_exists( strtolower( $k ), self::$whitelist_attributes[ strtolower( $node['name'] ) ] ) && self::check_attr_value( strtolower( $k ), $v, self::$whitelist_attributes[ strtolower( $node['name'] ) ][ strtolower( $k ) ] ) ) {
$attr_ok = true;
}

// if it wasn't in one of the whitelists or failed its check, remove it
if ( $attr_ok != true ) {
unset( $node['attrs'][$k] );
}
}
}
break;
case HTMLTokenizer::NODE_TYPE_ELEMENT_CLOSE:
if ( ! in_array( strtolower( $node['name'] ), self::$whitelist_elements ) ) {
if ( strtolower( $temp = array_pop( $stack ) ) !== strtolower( $node['name'] ) ) {
// something weird happened (Luke, use the DOM!)
array_push( $stack, $temp );
}
//$node = null;
//convert the node to text
$node = array(
'type' => HTMLTokenizer::NODE_TYPE_TEXT,
'name' => '#text',
'value' => HTMLTokenSet::token_to_string( $node ),
'attrs' => array(),
);
}
break;
case HTMLTokenizer::NODE_TYPE_PI:
case HTMLTokenizer::NODE_TYPE_COMMENT:
case HTMLTokenizer::NODE_TYPE_CDATA_SECTION:
case HTMLTokenizer::NODE_TYPE_STATEMENT:
default:
$node = null;
break;
}

if ( $node != null ) {
$filtered[] = $node;
}
}

// rebuild our output string
return preg_replace( '#<([^>\s]+)(?:\s+[^>]+)?></\1>#u', '', (string) $filtered );
}
}

?>
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