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See Release Notes
Long Term Support Release

  • Bug fixes for general core bugs in 4.1.x will end 13 November 2023 (12 months).
  • Bug fixes for security issues in 4.1.x will end 10 November 2025 (36 months).
  • PHP version: minimum PHP 7.4.0 Note: minimum PHP version has increased since Moodle 4.0. PHP 8.0.x is supported too.
   1  <?php
   2  
   3  /**
   4   * Parser that uses PHP 5's DOM extension (part of the core).
   5   *
   6   * In PHP 5, the DOM XML extension was revamped into DOM and added to the core.
   7   * It gives us a forgiving HTML parser, which we use to transform the HTML
   8   * into a DOM, and then into the tokens.  It is blazingly fast (for large
   9   * documents, it performs twenty times faster than
  10   * HTMLPurifier_Lexer_DirectLex,and is the default choice for PHP 5.
  11   *
  12   * @note Any empty elements will have empty tokens associated with them, even if
  13   * this is prohibited by the spec. This is cannot be fixed until the spec
  14   * comes into play.
  15   *
  16   * @note PHP's DOM extension does not actually parse any entities, we use
  17   *       our own function to do that.
  18   *
  19   * @warning DOM tends to drop whitespace, which may wreak havoc on indenting.
  20   *          If this is a huge problem, due to the fact that HTML is hand
  21   *          edited and you are unable to get a parser cache that caches the
  22   *          the output of HTML Purifier while keeping the original HTML lying
  23   *          around, you may want to run Tidy on the resulting output or use
  24   *          HTMLPurifier_DirectLex
  25   */
  26  
  27  class HTMLPurifier_Lexer_DOMLex extends HTMLPurifier_Lexer
  28  {
  29  
  30      /**
  31       * @type HTMLPurifier_TokenFactory
  32       */
  33      private $factory;
  34  
  35      public function __construct()
  36      {
  37          // setup the factory
  38          parent::__construct();
  39          $this->factory = new HTMLPurifier_TokenFactory();
  40      }
  41  
  42      /**
  43       * @param string $html
  44       * @param HTMLPurifier_Config $config
  45       * @param HTMLPurifier_Context $context
  46       * @return HTMLPurifier_Token[]
  47       */
  48      public function tokenizeHTML($html, $config, $context)
  49      {
  50          $html = $this->normalize($html, $config, $context);
  51  
  52          // attempt to armor stray angled brackets that cannot possibly
  53          // form tags and thus are probably being used as emoticons
  54          if ($config->get('Core.AggressivelyFixLt')) {
  55              $char = '[^a-z!\/]';
  56              $comment = "/<!--(.*?)(-->|\z)/is";
  57              $html = preg_replace_callback($comment, array($this, 'callbackArmorCommentEntities'), $html);
  58              do {
  59                  $old = $html;
  60                  $html = preg_replace("/<($char)/i", '&lt;\\1', $html);
  61              } while ($html !== $old);
  62              $html = preg_replace_callback($comment, array($this, 'callbackUndoCommentSubst'), $html); // fix comments
  63          }
  64  
  65          // preprocess html, essential for UTF-8
  66          $html = $this->wrapHTML($html, $config, $context);
  67  
  68          $doc = new DOMDocument();
  69          $doc->encoding = 'UTF-8'; // theoretically, the above has this covered
  70  
  71          $options = 0;
  72          if ($config->get('Core.AllowParseManyTags') && defined('LIBXML_PARSEHUGE')) {
  73              $options |= LIBXML_PARSEHUGE;
  74          }
  75  
  76          set_error_handler(array($this, 'muteErrorHandler'));
  77          // loadHTML() fails on PHP 5.3 when second parameter is given
  78          if ($options) {
  79              $doc->loadHTML($html, $options);
  80          } else {
  81              $doc->loadHTML($html);
  82          }
  83          restore_error_handler();
  84  
  85          $body = $doc->getElementsByTagName('html')->item(0)-> // <html>
  86                        getElementsByTagName('body')->item(0);  // <body>
  87  
  88          $div = $body->getElementsByTagName('div')->item(0); // <div>
  89          $tokens = array();
  90          $this->tokenizeDOM($div, $tokens, $config);
  91          // If the div has a sibling, that means we tripped across
  92          // a premature </div> tag.  So remove the div we parsed,
  93          // and then tokenize the rest of body.  We can't tokenize
  94          // the sibling directly as we'll lose the tags in that case.
  95          if ($div->nextSibling) {
  96              $body->removeChild($div);
  97              $this->tokenizeDOM($body, $tokens, $config);
  98          }
  99          return $tokens;
 100      }
 101  
 102      /**
 103       * Iterative function that tokenizes a node, putting it into an accumulator.
 104       * To iterate is human, to recurse divine - L. Peter Deutsch
 105       * @param DOMNode $node DOMNode to be tokenized.
 106       * @param HTMLPurifier_Token[] $tokens   Array-list of already tokenized tokens.
 107       * @return HTMLPurifier_Token of node appended to previously passed tokens.
 108       */
 109      protected function tokenizeDOM($node, &$tokens, $config)
 110      {
 111          $level = 0;
 112          $nodes = array($level => new HTMLPurifier_Queue(array($node)));
 113          $closingNodes = array();
 114          do {
 115              while (!$nodes[$level]->isEmpty()) {
 116                  $node = $nodes[$level]->shift(); // FIFO
 117                  $collect = $level > 0 ? true : false;
 118                  $needEndingTag = $this->createStartNode($node, $tokens, $collect, $config);
 119                  if ($needEndingTag) {
 120                      $closingNodes[$level][] = $node;
 121                  }
 122                  if ($node->childNodes && $node->childNodes->length) {
 123                      $level++;
 124                      $nodes[$level] = new HTMLPurifier_Queue();
 125                      foreach ($node->childNodes as $childNode) {
 126                          $nodes[$level]->push($childNode);
 127                      }
 128                  }
 129              }
 130              $level--;
 131              if ($level && isset($closingNodes[$level])) {
 132                  while ($node = array_pop($closingNodes[$level])) {
 133                      $this->createEndNode($node, $tokens);
 134                  }
 135              }
 136          } while ($level > 0);
 137      }
 138  
 139      /**
 140       * Portably retrieve the tag name of a node; deals with older versions
 141       * of libxml like 2.7.6
 142       * @param DOMNode $node
 143       */
 144      protected function getTagName($node)
 145      {
 146          if (isset($node->tagName)) {
 147              return $node->tagName;
 148          } else if (isset($node->nodeName)) {
 149              return $node->nodeName;
 150          } else if (isset($node->localName)) {
 151              return $node->localName;
 152          }
 153          return null;
 154      }
 155  
 156      /**
 157       * Portably retrieve the data of a node; deals with older versions
 158       * of libxml like 2.7.6
 159       * @param DOMNode $node
 160       */
 161      protected function getData($node)
 162      {
 163          if (isset($node->data)) {
 164              return $node->data;
 165          } else if (isset($node->nodeValue)) {
 166              return $node->nodeValue;
 167          } else if (isset($node->textContent)) {
 168              return $node->textContent;
 169          }
 170          return null;
 171      }
 172  
 173  
 174      /**
 175       * @param DOMNode $node DOMNode to be tokenized.
 176       * @param HTMLPurifier_Token[] $tokens   Array-list of already tokenized tokens.
 177       * @param bool $collect  Says whether or start and close are collected, set to
 178       *                    false at first recursion because it's the implicit DIV
 179       *                    tag you're dealing with.
 180       * @return bool if the token needs an endtoken
 181       * @todo data and tagName properties don't seem to exist in DOMNode?
 182       */
 183      protected function createStartNode($node, &$tokens, $collect, $config)
 184      {
 185          // intercept non element nodes. WE MUST catch all of them,
 186          // but we're not getting the character reference nodes because
 187          // those should have been preprocessed
 188          if ($node->nodeType === XML_TEXT_NODE) {
 189              $data = $this->getData($node); // Handle variable data property
 190              if ($data !== null) {
 191                $tokens[] = $this->factory->createText($data);
 192              }
 193              return false;
 194          } elseif ($node->nodeType === XML_CDATA_SECTION_NODE) {
 195              // undo libxml's special treatment of <script> and <style> tags
 196              $last = end($tokens);
 197              $data = $node->data;
 198              // (note $node->tagname is already normalized)
 199              if ($last instanceof HTMLPurifier_Token_Start && ($last->name == 'script' || $last->name == 'style')) {
 200                  $new_data = trim($data);
 201                  if (substr($new_data, 0, 4) === '<!--') {
 202                      $data = substr($new_data, 4);
 203                      if (substr($data, -3) === '-->') {
 204                          $data = substr($data, 0, -3);
 205                      } else {
 206                          // Highly suspicious! Not sure what to do...
 207                      }
 208                  }
 209              }
 210              $tokens[] = $this->factory->createText($this->parseText($data, $config));
 211              return false;
 212          } elseif ($node->nodeType === XML_COMMENT_NODE) {
 213              // this is code is only invoked for comments in script/style in versions
 214              // of libxml pre-2.6.28 (regular comments, of course, are still
 215              // handled regularly)
 216              $tokens[] = $this->factory->createComment($node->data);
 217              return false;
 218          } elseif ($node->nodeType !== XML_ELEMENT_NODE) {
 219              // not-well tested: there may be other nodes we have to grab
 220              return false;
 221          }
 222          $attr = $node->hasAttributes() ? $this->transformAttrToAssoc($node->attributes) : array();
 223          $tag_name = $this->getTagName($node); // Handle variable tagName property
 224          if (empty($tag_name)) {
 225              return (bool) $node->childNodes->length;
 226          }
 227          // We still have to make sure that the element actually IS empty
 228          if (!$node->childNodes->length) {
 229              if ($collect) {
 230                  $tokens[] = $this->factory->createEmpty($tag_name, $attr);
 231              }
 232              return false;
 233          } else {
 234              if ($collect) {
 235                  $tokens[] = $this->factory->createStart($tag_name, $attr);
 236              }
 237              return true;
 238          }
 239      }
 240  
 241      /**
 242       * @param DOMNode $node
 243       * @param HTMLPurifier_Token[] $tokens
 244       */
 245      protected function createEndNode($node, &$tokens)
 246      {
 247          $tag_name = $this->getTagName($node); // Handle variable tagName property
 248          $tokens[] = $this->factory->createEnd($tag_name);
 249      }
 250  
 251      /**
 252       * Converts a DOMNamedNodeMap of DOMAttr objects into an assoc array.
 253       *
 254       * @param DOMNamedNodeMap $node_map DOMNamedNodeMap of DOMAttr objects.
 255       * @return array Associative array of attributes.
 256       */
 257      protected function transformAttrToAssoc($node_map)
 258      {
 259          // NamedNodeMap is documented very well, so we're using undocumented
 260          // features, namely, the fact that it implements Iterator and
 261          // has a ->length attribute
 262          if ($node_map->length === 0) {
 263              return array();
 264          }
 265          $array = array();
 266          foreach ($node_map as $attr) {
 267              $array[$attr->name] = $attr->value;
 268          }
 269          return $array;
 270      }
 271  
 272      /**
 273       * An error handler that mutes all errors
 274       * @param int $errno
 275       * @param string $errstr
 276       */
 277      public function muteErrorHandler($errno, $errstr)
 278      {
 279      }
 280  
 281      /**
 282       * Callback function for undoing escaping of stray angled brackets
 283       * in comments
 284       * @param array $matches
 285       * @return string
 286       */
 287      public function callbackUndoCommentSubst($matches)
 288      {
 289          return '<!--' . strtr($matches[1], array('&amp;' => '&', '&lt;' => '<')) . $matches[2];
 290      }
 291  
 292      /**
 293       * Callback function that entity-izes ampersands in comments so that
 294       * callbackUndoCommentSubst doesn't clobber them
 295       * @param array $matches
 296       * @return string
 297       */
 298      public function callbackArmorCommentEntities($matches)
 299      {
 300          return '<!--' . str_replace('&', '&amp;', $matches[1]) . $matches[2];
 301      }
 302  
 303      /**
 304       * Wraps an HTML fragment in the necessary HTML
 305       * @param string $html
 306       * @param HTMLPurifier_Config $config
 307       * @param HTMLPurifier_Context $context
 308       * @return string
 309       */
 310      protected function wrapHTML($html, $config, $context, $use_div = true)
 311      {
 312          $def = $config->getDefinition('HTML');
 313          $ret = '';
 314  
 315          if (!empty($def->doctype->dtdPublic) || !empty($def->doctype->dtdSystem)) {
 316              $ret .= '<!DOCTYPE html ';
 317              if (!empty($def->doctype->dtdPublic)) {
 318                  $ret .= 'PUBLIC "' . $def->doctype->dtdPublic . '" ';
 319              }
 320              if (!empty($def->doctype->dtdSystem)) {
 321                  $ret .= '"' . $def->doctype->dtdSystem . '" ';
 322              }
 323              $ret .= '>';
 324          }
 325  
 326          $ret .= '<html><head>';
 327          $ret .= '<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />';
 328          // No protection if $html contains a stray </div>!
 329          $ret .= '</head><body>';
 330          if ($use_div) $ret .= '<div>';
 331          $ret .= $html;
 332          if ($use_div) $ret .= '</div>';
 333          $ret .= '</body></html>';
 334          return $ret;
 335      }
 336  }
 337  
 338  // vim: et sw=4 sts=4