<?php

/*

 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between

 * Copyright (C) 2006-2009 Dan Fuhry

 *

 * This program is Free Software; you can redistribute 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 details.

 *

 * This script contains code originally found in MediaWiki (http://www.mediawiki.org). MediaWiki is also licensed under

 * the GPLv2 or later; see the file GPL included with this package for details.

 */

$attrib = '[a-zA-Z0-9]';

$space = '[\x09\x0a\x0d\x20]';

define( 'MW_CHAR_REFS_REGEX',

'/&([A-Za-z0-9]+);

 |&\#([0-9]+);

 |&\#x([0-9A-Za-z]+);

 |&\#X([0-9A-Za-z]+);

 |(&)/x' );

define( 'MW_ATTRIBS_REGEX',

	"/(?:^|$space)($attrib+)

		($space*=$space*

		(?:

 		# The attribute value: quoted or alone

			\"([^<\"]*)\"

 		| '([^<']*)'

 		|  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)

 		|  (\#[0-9a-fA-F]+) # Technically wrong, but lots of

 							# colors are specified like this.

 							# We'll be normalizing it.

		)

 		)?(?=$space|\$)/sx" );

/**

 * Take a tag soup fragment listing an HTML element's attributes

 * and normalize it to well-formed XML, discarding unwanted attributes.

 * Output is safe for further wikitext processing, with escaping of

 * values that could trigger problems.

 *

 * - Normalizes attribute names to lowercase

 * - Discards attributes not on a whitelist for the given element

 * - Turns broken or invalid entities into plaintext

 * - Double-quotes all attribute values

 * - Attributes without values are given the name as attribute

 * - Double attributes are discarded

 * - Unsafe style attributes are discarded

 * - Prepends space if there are attributes.

 *

 * @param string $text

 * @param string $element

 * @return string

 */

function fixTagAttributes( $text, $element ) {

	if( trim( $text ) == '' ) {

		return '';

	}

	$stripped = validateTagAttributes(

		decodeTagAttributes( $text ), $element );

	$attribs = array();

	foreach( $stripped as $attribute => $value ) {

		$encAttribute = htmlspecialchars( $attribute );

		$encValue = safeEncodeAttribute( $value );

		$attribs[] = "$encAttribute=".'"'."$encValue".'"'.""; // "

	}

	return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';

}

/**

 * Encode an attribute value for HTML tags, with extra armoring

 * against further wiki processing.

 * @param $text

 * @return HTML-encoded text fragment

 */

function safeEncodeAttribute( $text ) {

	$encValue= encodeAttribute( $text );

	# Templates and links may be expanded in later parsing,

	# creating invalid or dangerous output. Suppress this.

	$encValue = strtr( $encValue, array(

		'<'    => '&lt;',   // This should never happen,

		'>'    => '>',   // we've received invalid input

		'"'    => '"', // which should have been escaped.

		'{'    => '{',

		'['    => '[',

		"''"   => '''',

		'ISBN' => 'ISBN',

		'RFC'  => 'RFC',

		'PMID' => 'PMID',

		'|'    => '|',

		'__'   => '__',

	) );

	return $encValue;

}

/**

 * Encode an attribute value for HTML output.

 * @param $text

 * @return HTML-encoded text fragment

 */

function encodeAttribute( $text ) {

	// In Enano 1.0.3, added this cheapo hack to keep ampersands

	// from being double-sanitized. Thanks to markybob from #deluge.

	// htmlspecialchars() the "manual" way

	$encValue = strtr( $text, array(

		'&'  => '&',

		'"' => '"',

		'&lt;'   => '<',

		'>'   => '>',

		''' => "'"

	) );

	$encValue = strtr( $text, array(

		'&' => '&',

		'"' => '"',

		'<' => '&lt;',

		'>' => '>',

		"'" => '''

	) );

	// Whitespace is normalized during attribute decoding,

	// so if we've been passed non-spaces we must encode them

	// ahead of time or they won't be preserved.

	$encValue = strtr( $encValue, array(

		"\n" => '
',

		"\r" => '
',

		"\t" => '	',

	) );

	return $encValue;

}

function unstripForHTML( $text ) {

	global $mStripState;

	$text = unstrip( $text, $mStripState );

	$text = unstripNoWiki( $text, $mStripState );

	return $text;

}

/**

 * Always call this after unstrip() to preserve the order

 *

 * @private

 */

function unstripNoWiki( $text, &$state ) {

	if ( !isset( $state['nowiki'] ) ) {

		return $text;

	}

	# TODO: good candidate for FSS

	$text = strtr( $text, $state['nowiki'] );

	return $text;

}

/**

 * Take an array of attribute names and values and normalize or discard

 * illegal values for the given element type.

 *

 * - Discards attributes not on a whitelist for the given element

 * - Unsafe style attributes are discarded

 *

 * @param array $attribs

 * @param string $element

 * @return array

 *

 * @todo Check for legal values where the DTD limits things.

 * @todo Check for unique id attribute :P

 */

function validateTagAttributes( $attribs, $element ) {

	$whitelist = array_flip( attributeWhitelist( $element ) );

	$out = array();

	foreach( $attribs as $attribute => $value ) {

		if( !isset( $whitelist[$attribute] ) ) {

			continue;

		}

		# Strip javascript "expression" from stylesheets.

		# http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp

		if( $attribute == 'style' ) {

			$value = checkCss( $value );

			if( $value === false ) {

				# haxx0r

				continue;

			}

		}

		if ( $attribute === 'id' )

			$value = escapeId( $value );

		// If this attribute was previously set, override it.

		// Output should only have one attribute of each name.

		$out[$attribute] = $value;

	}

	return $out;

}

/**

 * Pick apart some CSS and check it for forbidden or unsafe structures.

 * Returns a sanitized string, or false if it was just too evil.

 *

 * Currently URL references, 'expression', 'tps' are forbidden.

 *

 * @param string $value

 * @return mixed

 */

function checkCss( $value ) {

	$stripped = decodeCharReferences( $value );

	// Remove any comments; IE gets token splitting wrong

	$stripped = preg_replace( '!/\\*.*?\\*/!S', '', $stripped );

	$value = $stripped;

	// ... and continue checks

	$stripped = preg_replace( '!\\\\([0-9A-Fa-f]{1,6})[ \\n\\r\\t\\f]?!e',

		'codepointToUtf8(hexdec("$1"))', $stripped );

	$stripped = str_replace( '\\', '', $stripped );

	if( preg_match( '/(expression|tps*:\/\/|url\\s*\().*/is',

			$stripped ) ) {

		# haxx0r

		return false;

	}

	return $value;

}

/**

 * Decode any character references, numeric or named entities,

 * in the text and return a UTF-8 string.

 *

 * @param string $text

 * @return string

 * @access public

 * @static

 */

function decodeCharReferences( $text ) {

	return preg_replace_callback(

		MW_CHAR_REFS_REGEX,

		'decodeCharReferencesCallback',

		$text );

}

/**

 * Fetch the whitelist of acceptable attributes for a given

 * element name.

 *

 * @param string $element

 * @return array

 */

function attributeWhitelist( $element ) {

	static $list;

	if( !isset( $list ) ) {

		$list = setupAttributeWhitelist();

	}

	return isset( $list[$element] )

		? $list[$element]

		: array();

}

/**

 * @todo Document it a bit

 * @return array

 */

function setupAttributeWhitelist() {

	global $db, $session, $paths, $template, $plugins;

	$common = array( 'id', 'class', 'lang', 'dir', 'title', 'style' );

	$block = array_merge( $common, array( 'align' ) );

	$tablealign = array( 'align', 'char', 'charoff', 'valign' );

	$tablecell = array( 'abbr',

											'axis',

											'headers',

											'scope',

											'rowspan',

											'colspan',

											'nowrap', # deprecated

											'width',  # deprecated

											'height', # deprecated

											'bgcolor' # deprecated

											);

	# Numbers refer to sections in HTML 4.01 standard describing the element.

	# See: http://www.w3.org/TR/html4/

	$whitelist = array (

		# 7.5.4

		'div'        => $block,

		'center'     => $common, # deprecated

		'span'       => $block, # ??

		# 7.5.5

		'h1'         => $block,

		'h2'         => $block,

		'h3'         => $block,

		'h4'         => $block,

		'h5'         => $block,

		'h6'         => $block,

		# 7.5.6

		# address

		# 8.2.4

		# bdo

		# 9.2.1

		'em'         => $common,

		'strong'     => $common,

		'cite'       => $common,

		# dfn

		'code'       => $common,

		# samp

		# kbd

		'var'        => $common,

		# abbr

		# acronym

		# 9.2.2

		'blockquote' => array_merge( $common, array( 'cite' ) ),

		# q

		# 9.2.3

		'sub'        => $common,

		'sup'        => $common,

		# 9.3.1

		'p'          => $block,

		# 9.3.2

		'br'         => array( 'id', 'class', 'title', 'style', 'clear' ),

		# 9.3.4

		'pre'        => array_merge( $common, array( 'width' ) ),

		# 9.4

		'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),

		'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),

		# 10.2

		'ul'         => array_merge( $common, array( 'type' ) ),

		'ol'         => array_merge( $common, array( 'type', 'start' ) ),

		'li'         => array_merge( $common, array( 'type', 'value' ) ),

		# 10.3

		'dl'         => $common,

		'dd'         => $common,

		'dt'         => $common,

		# 11.2.1

		'table'      => array_merge( $common,

							array( 'summary', 'width', 'border', 'frame',

									'rules', 'cellspacing', 'cellpadding',

									'align', 'bgcolor',

							) ),

		# 11.2.2

		'caption'    => array_merge( $common, array( 'align' ) ),

		# 11.2.3

		'thead'      => array_merge( $common, $tablealign ),

		'tfoot'      => array_merge( $common, $tablealign ),

		'tbody'      => array_merge( $common, $tablealign ),

		# 11.2.4

		'colgroup'   => array_merge( $common, array( 'span', 'width' ), $tablealign ),

		'col'        => array_merge( $common, array( 'span', 'width' ), $tablealign ),

		# 11.2.5

		'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),

		# 11.2.6

		'td'         => array_merge( $common, $tablecell, $tablealign ),

		'th'         => array_merge( $common, $tablecell, $tablealign ),

		# 12.2

		# added by dan

		'a'          => array_merge( $common, array( 'href', 'name' ) ),

		# 13.2

		# added by dan

		'img'        => array_merge( $common, array( 'src', 'width', 'height', 'alt' ) ),

		# 15.2.1

		'tt'         => $common,

		'b'          => $common,

		'i'          => $common,

		'big'        => $common,

		'small'      => $common,

		'strike'     => $common,

		's'          => $common,

		'u'          => $common,

		# 15.2.2

		'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),

		# basefont

		# 15.3

		'hr'         => array_merge( $common, array( 'noshade', 'size', 'width' ) ),

		# XHTML Ruby annotation text module, simple ruby only.

		# http://www.w3c.org/TR/ruby/

		'ruby'       => $common,

		# rbc

		# rtc

		'rb'         => $common,

		'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),

		'rp'         => $common,

		# For compatibility with the XHTML parser.

		'nowiki'     => array(),

		'noinclude'  => array(),

		'nodisplay'  => array(),

		'lang'       => array('code'),

		# XHTML stuff

		'acronym'    => $common

		);

	// custom tags can be added by plugins

	$code = $plugins->setHook('html_attribute_whitelist');

	foreach ( $code as $cmd )

	{

		eval($cmd);

	}

	return $whitelist;

}

/**

 * Given a value escape it so that it can be used in an id attribute and

 * return it, this does not validate the value however (see first link)

 *

 * @link http://www.w3.org/TR/html401/types.html#type-name Valid characters

 *                                                          in the id and

 *                                                          name attributes

 * @link http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with the id attribute

 *

 * @bug 4461

 *

 * @static

 *

 * @param string $id

 * @return string

 */

function escapeId( $id ) {

	static $replace = array(

		'%3A' => ':',

		'%' => '.'

	);

	$id = urlencode( decodeCharReferences( strtr( $id, ' ', '_' ) ) );

	return str_replace( array_keys( $replace ), array_values( $replace ), $id );

}

/**

 * More or less "markup-safe" explode()

 * Ignores any instances of the separator inside <...>

 * @param string $separator

 * @param string $text

 * @return array

 */

function wfExplodeMarkup( $separator, $text ) {

	$placeholder = "\x00";

	// Just in case...

	$text = str_replace( $placeholder, '', $text );

	// Trim stuff

	$replacer = new ReplacerCallback( $separator, $placeholder );

	$cleaned = preg_replace_callback( '/(<.*?>)/', array( $replacer, 'go' ), $text );

	$items = explode( $separator, $cleaned );

	foreach( $items as $i => $str ) {

		$items[$i] = str_replace( $placeholder, $separator, $str );

	}

	return $items;

}

class ReplacerCallback {

	function ReplacerCallback( $from, $to ) {

		$this->from = $from;

		$this->to = $to;

	}

	function go( $matches ) {

		return str_replace( $this->from, $this->to, $matches[1] );

	}

}

/**

 * Return an associative array of attribute names and values from