htmlpurifier/library/HTMLPurifier.php

<?php

/*! @mainpage
 * 
 * HTML Purifier is an HTML filter that will take an arbitrary snippet of
 * HTML and rigorously test, validate and filter it into a version that
 * is safe for output onto webpages. It achieves this by:
 * 
 *  -# Lexing (parsing into tokens) the document,
 *  -# Executing various strategies on the tokens:
 *      -# Removing all elements not in the whitelist,
 *      -# Making the tokens well-formed,
 *      -# Fixing the nesting of the nodes, and
 *      -# Validating attributes of the nodes; and
 *  -# Generating HTML from the purified tokens.
 * 
 * However, most users will only need to interface with the HTMLPurifier
 * class, so this massive amount of infrastructure is usually concealed.
 * If you plan on working with the internals, be sure to include
 * HTMLPurifier_ConfigSchema and HTMLPurifier_Config.
 */

/*
    HTML Purifier 3.0.0 - Standards Compliant HTML Filtering
    Copyright (C) 2006-2008 Edward Z. Yang

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

// constants are slow, but we'll make one exception
define('HTMLPURIFIER_PREFIX', dirname(__FILE__));

// every class has an undocumented dependency to these, must be included!
HTMLPurifier_ConfigSchema::define(
    'Core', 'CollectErrors', false, 'bool', '
Whether or not to collect errors found while filtering the document. This
is a useful way to give feedback to your users. <strong>Warning:</strong>
Currently this feature is very patchy and experimental, with lots of
possible error messages not yet implemented. It will not cause any problems,
but it may not help your users either. This directive has been available
since 2.0.0.
');

/**
 * Facade that coordinates HTML Purifier's subsystems in order to purify HTML.
 * 
 * @note There are several points in which configuration can be specified 
 *       for HTML Purifier.  The precedence of these (from lowest to
 *       highest) is as follows:
 *          -# Instance: new HTMLPurifier($config)
 *          -# Invocation: purify($html, $config)
 *       These configurations are entirely independent of each other and
 *       are *not* merged.
 * 
 * @todo We need an easier way to inject strategies, it'll probably end
 *       up getting done through config though.
 */
class HTMLPurifier
{
    
    public $version = '3.0.0';
    
    public $config;
    public $filters = array();
    
    protected $strategy, $generator;
    
    /**
     * Resultant HTMLPurifier_Context of last run purification. Is an array
     * of contexts if the last called method was purifyArray().
     * @public
     */
    public $context;
    
    /**
     * Initializes the purifier.
     * @param $config Optional HTMLPurifier_Config object for all instances of
     *                the purifier, if omitted, a default configuration is
     *                supplied (which can be overridden on a per-use basis).
     *                The parameter can also be any type that
     *                HTMLPurifier_Config::create() supports.
     */
    public function __construct($config = null) {
        
        $this->config = HTMLPurifier_Config::create($config);
        
        $this->strategy     = new HTMLPurifier_Strategy_Core();
        $this->generator    = new HTMLPurifier_Generator();
        
    }
    
    /**
     * Adds a filter to process the output. First come first serve
     * @param $filter HTMLPurifier_Filter object
     */
    public function addFilter($filter) {
        $this->filters[] = $filter;
    }
    
    /**
     * Filters an HTML snippet/document to be XSS-free and standards-compliant.
     * 
     * @param $html String of HTML to purify
     * @param $config HTMLPurifier_Config object for this operation, if omitted,
     *                defaults to the config object specified during this
     *                object's construction. The parameter can also be any type
     *                that HTMLPurifier_Config::create() supports.
     * @return Purified HTML
     */
    public function purify($html, $config = null) {
        
        // todo: make the config merge in, instead of replace
        $config = $config ? HTMLPurifier_Config::create($config) : $this->config;
        
        // implementation is partially environment dependant, partially
        // configuration dependant
        $lexer = HTMLPurifier_Lexer::create($config);
        
        $context = new HTMLPurifier_Context();
        
        // our friendly neighborhood generator, all primed with configuration too!
        $this->generator->generateFromTokens(array(), $config, $context);
        $context->register('Generator', $this->generator);
        
        // set up global context variables
        if ($config->get('Core', 'CollectErrors')) {
            // may get moved out if other facilities use it
            $language_factory = HTMLPurifier_LanguageFactory::instance();
            $language = $language_factory->create($config, $context);
            $context->register('Locale', $language);
            
            $error_collector = new HTMLPurifier_ErrorCollector($context);
            $context->register('ErrorCollector', $error_collector);
        }
        
        // setup id_accumulator context, necessary due to the fact that
        // AttrValidator can be called from many places
        $id_accumulator = HTMLPurifier_IDAccumulator::build($config, $context);
        $context->register('IDAccumulator', $id_accumulator);
        
        $html = HTMLPurifier_Encoder::convertToUTF8($html, $config, $context);
        
        for ($i = 0, $size = count($this->filters); $i < $size; $i++) {
            $html = $this->filters[$i]->preFilter($html, $config, $context);
        }
        
        // purified HTML
        $html = 
            $this->generator->generateFromTokens(
                // list of tokens
                $this->strategy->execute(
                    // list of un-purified tokens
                    $lexer->tokenizeHTML(
                        // un-purified HTML
                        $html, $config, $context
                    ),
                    $config, $context
                ),
                $config, $context
            );
        
        for ($i = $size - 1; $i >= 0; $i--) {
            $html = $this->filters[$i]->postFilter($html, $config, $context);
        }
        
        $html = HTMLPurifier_Encoder::convertFromUTF8($html, $config, $context);
        $this->context =& $context;
        return $html;
    }
    
    /**
     * Filters an array of HTML snippets
     * @param $config Optional HTMLPurifier_Config object for this operation.
     *                See HTMLPurifier::purify() for more details.
     * @return Array of purified HTML
     */
    public function purifyArray($array_of_html, $config = null) {
        $context_array = array();
        foreach ($array_of_html as $key => $html) {
            $array_of_html[$key] = $this->purify($html, $config);
            $context_array[$key] = $this->context;
        }
        $this->context = $context_array;
        return $array_of_html;
    }
    
    /**
     * Singleton for enforcing just one HTML Purifier in your system
     * @param $prototype Optional prototype HTMLPurifier instance to
     *                   overload singleton with.
     */
    public static function &getInstance($prototype = null) {
        static $htmlpurifier;
        if (!$htmlpurifier || $prototype) {
            if ($prototype instanceof HTMLPurifier) {
                $htmlpurifier = $prototype;
            } elseif ($prototype) {
                $htmlpurifier = new HTMLPurifier($prototype);
            } else {
                $htmlpurifier = new HTMLPurifier();
            }
        }
        return $htmlpurifier;
    }
    
}