library/HTMLPurifier/AttrDef/CSS/FontFamily.php

   1 <?php
   2
   3 /**
   4  * Validates a font family list according to CSS spec
   5  * @todo whitelisting allowed fonts would be nice
   6  */
   7 class HTMLPurifier_AttrDef_CSS_FontFamily extends HTMLPurifier_AttrDef
   8 {
   9
  10     public function validate($string, $config, $context) {
  11         static $generic_names = array(
  12             'serif' => true,
  13             'sans-serif' => true,
  14             'monospace' => true,
  15             'fantasy' => true,
  16             'cursive' => true
  17         );
  18
  19         // assume that no font names contain commas in them
  20         $fonts = explode(',', $string);
  21         $final = '';
  22         foreach($fonts as $font) {
  23             $font = trim($font);
  24             if ($font === '') continue;
  25             // match a generic name
  26             if (isset($generic_names[$font])) {
  27                 $final .= $font . ', ';
  28                 continue;
  29             }
  30             // match a quoted name
  31             if ($font[0] === '"' || $font[0] === "'") {
  32                 $length = strlen($font);
  33                 if ($length <= 2) continue;
  34                 $quote = $font[0];
  35                 if ($font[$length - 1] !== $quote) continue;
  36                 $font = substr($font, 1, $length - 2);
  37             }
  38
  39             $font = $this->expandCSSEscape($font);
  40
  41             // $font is a pure representation of the font name
  42
  43             if (ctype_alnum($font) && $font !== '') {
  44                 // very simple font, allow it in unharmed
  45                 $final .= $font . ', ';
  46                 continue;
  47             }
  48
  49             // bugger out on whitespace.  form feed (0C) really
  50             // shouldn't show up regardless
  51             $font = str_replace(array("\n", "\t", "\r", "\x0C"), ' ', $font);
  52
  53             // These ugly transforms don't pose a security
  54             // risk (as \\ and \" might).  We could try to be clever and
  55             // use single-quote wrapping when there is a double quote
  56             // present, but I have choosen not to implement that.
  57             // (warning: this code relies on the selection of quotation
  58             // mark below)
  59             $font = str_replace('\\', '\\5C ', $font);
  60             $font = str_replace('"',  '\\22 ', $font);
  61
  62             // complicated font, requires quoting
  63             $final .= "\"$font\", "; // note that this will later get turned into &quot;
  64         }
  65         $final = rtrim($final, ', ');
  66         if ($final === '') return false;
  67         return $final;
  68     }
  69
  70 }
  71
  72 // vim: et sw=4 sts=4