File indexing completed on 2024-05-12 06:02:04

 <?php
 
 // why is this a top level function? Because PHP 5.2.0 doesn't seem to
 // understand how to interpret this filter if it's a static method.
 // It's all really silly, but if we go this route it might be reasonable
 // to coalesce all of these methods into one.
 function htmlpurifier_filter_extractstyleblocks_muteerrorhandler()
 {
 }
 
 /**
  * This filter extracts <style> blocks from input HTML, cleans them up
  * using CSSTidy, and then places them in $purifier->context->get('StyleBlocks')
  * so they can be used elsewhere in the document.
  *
  * @note
  *      See tests/HTMLPurifier/Filter/ExtractStyleBlocksTest.php for
  *      sample usage.
  *
  * @note
  *      This filter can also be used on stylesheets not included in the
  *      document--something purists would probably prefer. Just directly
  *      call HTMLPurifier_Filter_ExtractStyleBlocks->cleanCSS()
  */
 class HTMLPurifier_Filter_ExtractStyleBlocks extends HTMLPurifier_Filter
 {
     /**
      * @type string
      */
     public $name = 'ExtractStyleBlocks';
 
     /**
      * @type array
      */
     private $_styleMatches = array();
 
     /**
      * @type csstidy
      */
     private $_tidy;
 
     /**
      * @type HTMLPurifier_AttrDef_HTML_ID
      */
     private $_id_attrdef;
 
     /**
      * @type HTMLPurifier_AttrDef_CSS_Ident
      */
     private $_class_attrdef;
 
     /**
      * @type HTMLPurifier_AttrDef_Enum
      */
     private $_enum_attrdef;
 
     public function __construct()
     {
         $this->_tidy = new csstidy();
         $this->_tidy->set_cfg('lowercase_s', false);
         $this->_id_attrdef = new HTMLPurifier_AttrDef_HTML_ID(true);
         $this->_class_attrdef = new HTMLPurifier_AttrDef_CSS_Ident();
         $this->_enum_attrdef = new HTMLPurifier_AttrDef_Enum(
             array(
                 'first-child',
                 'link',
                 'visited',
                 'active',
                 'hover',
                 'focus'
             )
         );
     }
 
     /**
      * Save the contents of CSS blocks to style matches
      * @param array $matches preg_replace style $matches array
      */
     protected function styleCallback($matches)
     {
         $this->_styleMatches[] = $matches[1];
     }
 
     /**
      * Removes inline <style> tags from HTML, saves them for later use
      * @param string $html
      * @param HTMLPurifier_Config $config
      * @param HTMLPurifier_Context $context
      * @return string
      * @todo Extend to indicate non-text/css style blocks
      */
     public function preFilter($html, $config, $context)
     {
         $tidy = $config->get('Filter.ExtractStyleBlocks.TidyImpl');
         if ($tidy !== null) {
             $this->_tidy = $tidy;
         }
         // NB: this must be NON-greedy because if we have
         // <style>foo</style>  <style>bar</style>
         // we must not grab foo</style>  <style>bar
         $html = preg_replace_callback('#<style(?:\s.*)?>(.*)<\/style>#isU', array($this, 'styleCallback'), $html);
         $style_blocks = $this->_styleMatches;
         $this->_styleMatches = array(); // reset
         $context->register('StyleBlocks', $style_blocks); // $context must not be reused
         if ($this->_tidy) {
             foreach ($style_blocks as &$style) {
                 $style = $this->cleanCSS($style, $config, $context);
             }
         }
         return $html;
     }
 
     /**
      * Takes CSS (the stuff found in <style>) and cleans it.
      * @warning Requires CSSTidy <http://csstidy.sourceforge.net/>
      * @param string $css CSS styling to clean
      * @param HTMLPurifier_Config $config
      * @param HTMLPurifier_Context $context
      * @throws HTMLPurifier_Exception
      * @return string Cleaned CSS
      */
     public function cleanCSS($css, $config, $context)
     {
         // prepare scope
         $scope = $config->get('Filter.ExtractStyleBlocks.Scope');
         if ($scope !== null) {
             $scopes = array_map('trim', explode(',', $scope));
         } else {
             $scopes = array();
         }
         // remove comments from CSS
         $css = trim($css);
         if (strncmp('<!--', $css, 4) === 0) {
             $css = substr($css, 4);
         }
         if (strlen($css) > 3 && substr($css, -3) == '-->') {
             $css = substr($css, 0, -3);
         }
         $css = trim($css);
         set_error_handler('htmlpurifier_filter_extractstyleblocks_muteerrorhandler');
         $this->_tidy->parse($css);
         restore_error_handler();
         $css_definition = $config->getDefinition('CSS');
         $html_definition = $config->getDefinition('HTML');
         $new_css = array();
         foreach ($this->_tidy->css as $k => $decls) {
             // $decls are all CSS declarations inside an @ selector
             $new_decls = array();
             foreach ($decls as $selector => $style) {
                 $selector = trim($selector);
                 if ($selector === '') {
                     continue;
                 } // should not happen
                 // Parse the selector
                 // Here is the relevant part of the CSS grammar:
                 //
                 // ruleset
                 //   : selector [ ',' S* selector ]* '{' ...
                 // selector
                 //   : simple_selector [ combinator selector | S+ [ combinator? selector ]? ]?
                 // combinator
                 //   : '+' S*
                 //   : '>' S*
                 // simple_selector
                 //   : element_name [ HASH | class | attrib | pseudo ]*
                 //   | [ HASH | class | attrib | pseudo ]+
                 // element_name
                 //   : IDENT | '*'
                 //   ;
                 // class
                 //   : '.' IDENT
                 //   ;
                 // attrib
                 //   : '[' S* IDENT S* [ [ '=' | INCLUDES | DASHMATCH ] S*
                 //     [ IDENT | STRING ] S* ]? ']'
                 //   ;
                 // pseudo
                 //   : ':' [ IDENT | FUNCTION S* [IDENT S*]? ')' ]
                 //   ;
                 //
                 // For reference, here are the relevant tokens:
                 //
                 // HASH         #{name}
                 // IDENT        {ident}
                 // INCLUDES     ==
                 // DASHMATCH    |=
                 // STRING       {string}
                 // FUNCTION     {ident}\(
                 //
                 // And the lexical scanner tokens
                 //
                 // name         {nmchar}+
                 // nmchar       [_a-z0-9-]|{nonascii}|{escape}
                 // nonascii     [\240-\377]
                 // escape       {unicode}|\\[^\r\n\f0-9a-f]
                 // unicode      \\{h}}{1,6}(\r\n|[ \t\r\n\f])?
                 // ident        -?{nmstart}{nmchar*}
                 // nmstart      [_a-z]|{nonascii}|{escape}
                 // string       {string1}|{string2}
                 // string1      \"([^\n\r\f\\"]|\\{nl}|{escape})*\"
                 // string2      \'([^\n\r\f\\"]|\\{nl}|{escape})*\'
                 //
                 // We'll implement a subset (in order to reduce attack
                 // surface); in particular:
                 //
                 //      - No Unicode support
                 //      - No escapes support
                 //      - No string support (by proxy no attrib support)
                 //      - element_name is matched against allowed
                 //        elements (some people might find this
                 //        annoying...)
                 //      - Pseudo-elements one of :first-child, :link,
                 //        :visited, :active, :hover, :focus
 
                 // handle ruleset
                 $selectors = array_map('trim', explode(',', $selector));
                 $new_selectors = array();
                 foreach ($selectors as $sel) {
                     // split on +, > and spaces
                     $basic_selectors = preg_split('/\s*([+> ])\s*/', $sel, -1, PREG_SPLIT_DELIM_CAPTURE);
                     // even indices are chunks, odd indices are
                     // delimiters
                     $nsel = null;
                     $delim = null; // guaranteed to be non-null after
                     // two loop iterations
                     for ($i = 0, $c = count($basic_selectors); $i < $c; $i++) {
                         $x = $basic_selectors[$i];
                         if ($i % 2) {
                             // delimiter
                             if ($x === ' ') {
                                 $delim = ' ';
                             } else {
                                 $delim = ' ' . $x . ' ';
                             }
                         } else {
                             // simple selector
                             $components = preg_split('/([#.:])/', $x, -1, PREG_SPLIT_DELIM_CAPTURE);
                             $sdelim = null;
                             $nx = null;
                             for ($j = 0, $cc = count($components); $j < $cc; $j++) {
                                 $y = $components[$j];
                                 if ($j === 0) {
                                     if ($y === '*' || isset($html_definition->info[$y = strtolower($y)])) {
                                         $nx = $y;
                                     } else {
                                         // $nx stays null; this matters
                                         // if we don't manage to find
                                         // any valid selector content,
                                         // in which case we ignore the
                                         // outer $delim
                                     }
                                 } elseif ($j % 2) {
                                     // set delimiter
                                     $sdelim = $y;
                                 } else {
                                     $attrdef = null;
                                     if ($sdelim === '#') {
                                         $attrdef = $this->_id_attrdef;
                                     } elseif ($sdelim === '.') {
                                         $attrdef = $this->_class_attrdef;
                                     } elseif ($sdelim === ':') {
                                         $attrdef = $this->_enum_attrdef;
                                     } else {
                                         throw new HTMLPurifier_Exception('broken invariant sdelim and preg_split');
                                     }
                                     $r = $attrdef->validate($y, $config, $context);
                                     if ($r !== false) {
                                         if ($r !== true) {
                                             $y = $r;
                                         }
                                         if ($nx === null) {
                                             $nx = '';
                                         }
                                         $nx .= $sdelim . $y;
                                     }
                                 }
                             }
                             if ($nx !== null) {
                                 if ($nsel === null) {
                                     $nsel = $nx;
                                 } else {
                                     $nsel .= $delim . $nx;
                                 }
                             } else {
                                 // delimiters to the left of invalid
                                 // basic selector ignored
                             }
                         }
                     }
                     if ($nsel !== null) {
                         if (!empty($scopes)) {
                             foreach ($scopes as $s) {
                                 $new_selectors[] = "$s $nsel";
                             }
                         } else {
                             $new_selectors[] = $nsel;
                         }
                     }
                 }
                 if (empty($new_selectors)) {
                     continue;
                 }
                 $selector = implode(', ', $new_selectors);
                 foreach ($style as $name => $value) {
                     if (!isset($css_definition->info[$name])) {
                         unset($style[$name]);
                         continue;
                     }
                     $def = $css_definition->info[$name];
                     $ret = $def->validate($value, $config, $context);
                     if ($ret === false) {
                         unset($style[$name]);
                     } else {
                         $style[$name] = $ret;
                     }
                 }
                 $new_decls[$selector] = $style;
             }
             $new_css[$k] = $new_decls;
         }
         // remove stuff that shouldn't be used, could be reenabled
         // after security risks are analyzed
         $this->_tidy->css = $new_css;
         $this->_tidy->import = array();
         $this->_tidy->charset = null;
         $this->_tidy->namespace = null;
         $css = $this->_tidy->print->plain();
         // we are going to escape any special characters <>& to ensure
         // that no funny business occurs (i.e. </style> in a font-family prop).
         if ($config->get('Filter.ExtractStyleBlocks.Escaping')) {
             $css = str_replace(
                 array('<', '>', '&'),
                 array('\3C ', '\3E ', '\26 '),
                 $css
             );
         }
         return $css;
     }
 }
 
 // vim: et sw=4 sts=4