htmlpurifier/library/HTMLPurifier/ChildDef.php

<?php

// HTMLPurifier_ChildDef and inheritance have three types of output:
// true = leave nodes as is
// false = delete parent node and all children
// array(...) = replace children nodes with these

HTMLPurifier_ConfigSchema::define(
    'Core', 'EscapeInvalidChildren', false, 'bool',
    'When true, a child is found that is not allowed in the context of the '.
    'parent element will be transformed into text as if it were ASCII. When '.
    'false, that element and all internal tags will be dropped, though text '.
    'will be preserved.  There is no option for dropping the element but '.
    'preserving child nodes.'
);

/**
 * Defines allowed child nodes and validates tokens against it.
 */
class HTMLPurifier_ChildDef
{
    /**
     * Type of child definition, usually right-most part of class name lowercase
     * 
     * Used occasionally in terms of context.  Possible values include
     * custom, required, optional and empty.
     */
    var $type;
    
    /**
     * Bool that indicates whether or not an empty array of children is okay
     * 
     * This is necessary for redundant checking when changes affecting
     * a child node may cause a parent node to now be disallowed.
     */
    var $allow_empty;
    
    /**
     * Validates nodes according to definition and returns modification.
     * 
     * @param $tokens_of_children Array of HTMLPurifier_Token
     * @param $config HTMLPurifier_Config object
     * @param $context HTMLPurifier_Context object
     * @return bool true to leave nodes as is
     * @return bool false to remove parent node
     * @return array of replacement child tokens
     */
    function validateChildren($tokens_of_children, $config, &$context) {
        trigger_error('Call to abstract function', E_USER_ERROR);
    }
}

/**
 * Custom validation class, accepts DTD child definitions
 * 
 * @warning Currently this class is an all or nothing proposition, that is,
 *          it will only give a bool return value.
 * @note This class is currently not used by any code, although it is unit
 *       tested.
 */
class HTMLPurifier_ChildDef_Custom extends HTMLPurifier_ChildDef
{
    var $type = 'custom';
    var $allow_empty = false;
    /**
     * Allowed child pattern as defined by the DTD
     */
    var $dtd_regex;
    /**
     * PCRE regex derived from $dtd_regex
     * @private
     */
    var $_pcre_regex;
    /**
     * @param $dtd_regex Allowed child pattern from the DTD
     */
    function HTMLPurifier_ChildDef_Custom($dtd_regex) {
        $this->dtd_regex = $dtd_regex;
        $this->_compileRegex();
    }
    /**
     * Compiles the PCRE regex from a DTD regex ($dtd_regex to $_pcre_regex)
     */
    function _compileRegex() {
        $raw = str_replace(' ', '', $this->dtd_regex);
        if ($raw{0} != '(') {
            $raw = "($raw)";
        }
        $reg = str_replace(',', ',?', $raw);
        $reg = preg_replace('/([#a-zA-Z0-9_.-]+)/', '(,?\\0)', $reg);
        $this->_pcre_regex = $reg;
    }
    function validateChildren($tokens_of_children, $config, &$context) {
        $list_of_children = '';
        $nesting = 0; // depth into the nest
        foreach ($tokens_of_children as $token) {
            if (!empty($token->is_whitespace)) continue;
            
            $is_child = ($nesting == 0); // direct
            
            if ($token->type == 'start') {
                $nesting++;
            } elseif ($token->type == 'end') {
                $nesting--;
            }
            
            if ($is_child) {
                $list_of_children .= $token->name . ',';
            }
        }
        $list_of_children = rtrim($list_of_children, ',');
        
        $okay =
            preg_match(
                '/^'.$this->_pcre_regex.'$/',
                $list_of_children
            );
        
        return (bool) $okay;
    }
}

/**
 * Definition that allows a set of elements, but disallows empty children.
 */
class HTMLPurifier_ChildDef_Required extends HTMLPurifier_ChildDef
{
    /**
     * Lookup table of allowed elements.
     */
    var $elements = array();
    /**
     * @param $elements List of allowed element names (lowercase).
     */
    function HTMLPurifier_ChildDef_Required($elements) {
        if (is_string($elements)) {
            $elements = str_replace(' ', '', $elements);
            $elements = explode('|', $elements);
        }
        $elements = array_flip($elements);
        foreach ($elements as $i => $x) $elements[$i] = true;
        $this->elements = $elements;
        $this->gen = new HTMLPurifier_Generator();
    }
    var $allow_empty = false;
    var $type = 'required';
    function validateChildren($tokens_of_children, $config, &$context) {
        // if there are no tokens, delete parent node
        if (empty($tokens_of_children)) return false;
        
        // the new set of children
        $result = array();
        
        // current depth into the nest
        $nesting = 0;
        
        // whether or not we're deleting a node
        $is_deleting = false;
        
        // whether or not parsed character data is allowed
        // this controls whether or not we silently drop a tag
        // or generate escaped HTML from it
        $pcdata_allowed = isset($this->elements['#PCDATA']);
        
        // a little sanity check to make sure it's not ALL whitespace
        $all_whitespace = true;
        
        // some configuration
        $escape_invalid_children = $config->get('Core', 'EscapeInvalidChildren');
        
        foreach ($tokens_of_children as $token) {
            if (!empty($token->is_whitespace)) {
                $result[] = $token;
                continue;
            }
            $all_whitespace = false; // phew, we're not talking about whitespace
            
            $is_child = ($nesting == 0);
            
            if ($token->type == 'start') {
                $nesting++;
            } elseif ($token->type == 'end') {
                $nesting--;
            }
            
            if ($is_child) {
                $is_deleting = false;
                if (!isset($this->elements[$token->name])) {
                    $is_deleting = true;
                    if ($pcdata_allowed && $token->type == 'text') {
                        $result[] = $token;
                    } elseif ($pcdata_allowed && $escape_invalid_children) {
                        $result[] = new HTMLPurifier_Token_Text(
                            $this->gen->generateFromToken($token, $config)
                        );
                    }
                    continue;
                }
            }
            if (!$is_deleting || ($pcdata_allowed && $token->type == 'text')) {
                $result[] = $token;
            } elseif ($pcdata_allowed && $escape_invalid_children) {
                $result[] =
                    new HTMLPurifier_Token_Text(
                        $this->gen->generateFromToken( $token, $config )
                    );
            } else {
                // drop silently
            }
        }
        if (empty($result)) return false;
        if ($all_whitespace) return false;
        if ($tokens_of_children == $result) return true;
        return $result;
    }
}

/**
 * Definition that allows a set of elements, and allows no children.
 * @note This is a hack to reuse code from HTMLPurifier_ChildDef_Required,
 *       really, one shouldn't inherit from the other.  Only altered behavior
 *       is to overload a returned false with an array.  Thus, it will never
 *       return false.
 */
class HTMLPurifier_ChildDef_Optional extends HTMLPurifier_ChildDef_Required
{
    var $allow_empty = true;
    var $type = 'optional';
    function validateChildren($tokens_of_children, $config, &$context) {
        $result = parent::validateChildren($tokens_of_children, $config, $context);
        if ($result === false) return array();
        return $result;
    }
}

/**
 * Definition that disallows all elements.
 * @warning validateChildren() in this class is actually never called, because
 *          empty elements are corrected in HTMLPurifier_Strategy_MakeWellFormed
 *          before child definitions are parsed in earnest by
 *          HTMLPurifier_Strategy_FixNesting.
 */
class HTMLPurifier_ChildDef_Empty extends HTMLPurifier_ChildDef
{
    var $allow_empty = true;
    var $type = 'empty';
    function HTMLPurifier_ChildDef_Empty() {}
    function validateChildren($tokens_of_children, $config, &$context) {
        return array();
    }
}

/**
 * Definition that uses different definitions depending on context.
 * 
 * The del and ins tags are notable because they allow different types of
 * elements depending on whether or not they're in a block or inline context.
 * Chameleon allows this behavior to happen by using two different
 * definitions depending on context.  While this somewhat generalized,
 * it is specifically intended for those two tags.
 */
class HTMLPurifier_ChildDef_Chameleon extends HTMLPurifier_ChildDef
{
    
    /**
     * Instance of the definition object to use when inline. Usually stricter.
     */
    var $inline;
    /**
     * Instance of the definition object to use when block.
     */
    var $block;
    
    /**
     * @param $inline List of elements to allow when inline.
     * @param $block List of elements to allow when block.
     */
    function HTMLPurifier_ChildDef_Chameleon($inline, $block) {
        $this->inline = new HTMLPurifier_ChildDef_Optional($inline);
        $this->block  = new HTMLPurifier_ChildDef_Optional($block);
    }
    
    function validateChildren($tokens_of_children, $config, &$context) {
        $parent_type = $context->get('ParentType');
        switch ($parent_type) {
            case 'unknown':
            case 'inline':
                $result = $this->inline->validateChildren(
                    $tokens_of_children, $config, $context);
                break;
            case 'block':
                $result = $this->block->validateChildren(
                    $tokens_of_children, $config, $context);
                break;
            default:
                trigger_error('Invalid context', E_USER_ERROR);
                return false;
        }
        return $result;
    }
}

/**
 * Definition for tables
 */
class HTMLPurifier_ChildDef_Table extends HTMLPurifier_ChildDef
{
    var $allow_empty = false;
    var $type = 'table';
    function HTMLPurifier_ChildDef_Table() {}
    function validateChildren($tokens_of_children, $config, &$context) {
        if (empty($tokens_of_children)) return false;
        
        // this ensures that the loop gets run one last time before closing
        // up. It's a little bit of a hack, but it works! Just make sure you
        // get rid of the token later.
        $tokens_of_children[] = false;
        
        // only one of these elements is allowed in a table
        $caption = false;
        $thead   = false;
        $tfoot   = false;
        
        // as many of these as you want
        $cols    = array();
        $content = array();
        
        $nesting = 0; // current depth so we can determine nodes
        $is_collecting = false; // are we globbing together tokens to package
                                // into one of the collectors?
        $collection = array(); // collected nodes
        $tag_index = 0; // the first node might be whitespace,
                            // so this tells us where the start tag is
        
        foreach ($tokens_of_children as $token) {
            $is_child = ($nesting == 0);
            
            if ($token === false) {
                // terminating sequence started
            } elseif ($token->type == 'start') {
                $nesting++;
            } elseif ($token->type == 'end') {
                $nesting--;
            }
            
            // handle node collection
            if ($is_collecting) {
                if ($is_child) {
                    // okay, let's stash the tokens away
                    // first token tells us the type of the collection
                    switch ($collection[$tag_index]->name) {
                        case 'tr':
                        case 'tbody':
                            $content[] = $collection;
                            break;
                        case 'caption':
                            if ($caption !== false) break;
                            $caption = $collection;
                            break;
                        case 'thead':
                        case 'tfoot':
                            // access the appropriate variable, $thead or $tfoot
                            $var = $collection[$tag_index]->name;
                            if ($$var === false) {
                                $$var = $collection;
                            } else {
                                // transmutate the first and less entries into
                                // tbody tags, and then put into content
                                $collection[$tag_index]->name = 'tbody';
                                $collection[count($collection)-1]->name = 'tbody';
                                $content[] = $collection;
                            }
                            break;
                         case 'colgroup':
                            $cols[] = $collection;
                            break;
                    }
                    $collection = array();
                    $is_collecting = false;
                    $tag_index = 0;
                } else {
                    // add the node to the collection
                    $collection[] = $token;
                }
            }
            
            // terminate
            if ($token === false) break;
            
            if ($is_child) {
                // determine what we're dealing with
                if ($token->name == 'col') {
                    // the only empty tag in the possie, we can handle it
                    // immediately
                    $cols[] = array_merge($collection, array($token));
                    $collection = array();
                    $tag_index = 0;
                    continue;
                }
                switch($token->name) {
                    case 'caption':
                    case 'colgroup':
                    case 'thead':
                    case 'tfoot':
                    case 'tbody':
                    case 'tr':
                        $is_collecting = true;
                        $collection[] = $token;
                        continue;
                    default:
                        if ($token->type == 'text' && $token->is_whitespace) {
                            $collection[] = $token;
                            $tag_index++;
                        }
                        continue;
                }
            }
        }
        
        if (empty($content)) return false;
        
        $ret = array();
        if ($caption !== false) $ret = array_merge($ret, $caption);
        if ($cols !== false)    foreach ($cols as $token_array) $ret = array_merge($ret, $token_array);
        if ($thead !== false)   $ret = array_merge($ret, $thead);
        if ($tfoot !== false)   $ret = array_merge($ret, $tfoot);
        foreach ($content as $token_array) $ret = array_merge($ret, $token_array);
        if (!empty($collection) && $is_collecting == false){
            // grab the trailing space
            $ret = array_merge($ret, $collection);
        }
        
        array_pop($tokens_of_children); // remove phantom token
        
        return ($ret === $tokens_of_children) ? true : $ret;
        
    }
}

?>