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
 */

/**
 * 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 (this behavior may change in the future).
 * 
 * @todo We need an easier way to inject strategies using the configuration
 *       object.
 */
class HTMLPurifier
{
    
    /** Version of HTML Purifier */
    public $version = '3.0.0';
    
    /** Global configuration object */
    public $config;
    
    /** Array of HTMLPurifier_Filter objects to run on HTML */
    public $filters = array();
    
    /** Single instance of HTML Purifier */
    private static $instance;
    
    protected $strategy, $generator;
    
    /**
     * Resultant HTMLPurifier_Context of last run purification. Is an array
     * of contexts if the last called method was purifyArray().
     */
    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) {
        if (!self::$instance || $prototype) {
            if ($prototype instanceof HTMLPurifier) {
                self::$instance = $prototype;
            } elseif ($prototype) {
                self::$instance = new HTMLPurifier($prototype);
            } else {
                self::$instance = new HTMLPurifier();
            }
        }
        return self::$instance;
    }
    
}