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   1  <?php
   2  
   3  /**
   4   * Validates a host according to the IPv4, IPv6 and DNS (future) specifications.
   5   */
   6  class HTMLPurifier_AttrDef_URI_Host extends HTMLPurifier_AttrDef
   7  {
   8  
   9      /**
  10       * IPv4 sub-validator.
  11       * @type HTMLPurifier_AttrDef_URI_IPv4
  12       */
  13      protected $ipv4;
  14  
  15      /**
  16       * IPv6 sub-validator.
  17       * @type HTMLPurifier_AttrDef_URI_IPv6
  18       */
  19      protected $ipv6;
  20  
  21      public function __construct()
  22      {
  23          $this->ipv4 = new HTMLPurifier_AttrDef_URI_IPv4();
  24          $this->ipv6 = new HTMLPurifier_AttrDef_URI_IPv6();
  25      }
  26  
  27      /**
  28       * @param string $string
  29       * @param HTMLPurifier_Config $config
  30       * @param HTMLPurifier_Context $context
  31       * @return bool|string
  32       */
  33      public function validate($string, $config, $context)
  34      {
  35          $length = strlen($string);
  36          // empty hostname is OK; it's usually semantically equivalent:
  37          // the default host as defined by a URI scheme is used:
  38          //
  39          //      If the URI scheme defines a default for host, then that
  40          //      default applies when the host subcomponent is undefined
  41          //      or when the registered name is empty (zero length).
  42          if ($string === '') {
  43              return '';
  44          }
  45          if ($length > 1 && $string[0] === '[' && $string[$length - 1] === ']') {
  46              //IPv6
  47              $ip = substr($string, 1, $length - 2);
  48              $valid = $this->ipv6->validate($ip, $config, $context);
  49              if ($valid === false) {
  50                  return false;
  51              }
  52              return '[' . $valid . ']';
  53          }
  54  
  55          // need to do checks on unusual encodings too
  56          $ipv4 = $this->ipv4->validate($string, $config, $context);
  57          if ($ipv4 !== false) {
  58              return $ipv4;
  59          }
  60  
  61          // A regular domain name.
  62  
  63          // This doesn't match I18N domain names, but we don't have proper IRI support,
  64          // so force users to insert Punycode.
  65  
  66          // There is not a good sense in which underscores should be
  67          // allowed, since it's technically not! (And if you go as
  68          // far to allow everything as specified by the DNS spec...
  69          // well, that's literally everything, modulo some space limits
  70          // for the components and the overall name (which, by the way,
  71          // we are NOT checking!).  So we (arbitrarily) decide this:
  72          // let's allow underscores wherever we would have allowed
  73          // hyphens, if they are enabled.  This is a pretty good match
  74          // for browser behavior, for example, a large number of browsers
  75          // cannot handle foo_.example.com, but foo_bar.example.com is
  76          // fairly well supported.
  77          $underscore = $config->get('Core.AllowHostnameUnderscore') ? '_' : '';
  78  
  79          // The productions describing this are:
  80          $a   = '[a-z]';     // alpha
  81          $an  = '[a-z0-9]';  // alphanum
  82          $and = "[a-z0-9-$underscore]"; // alphanum | "-"
  83          // domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
  84          $domainlabel = "$an($and*$an)?";
  85          // toplabel    = alpha | alpha *( alphanum | "-" ) alphanum
  86          $toplabel = "$a($and*$an)?";
  87          // hostname    = *( domainlabel "." ) toplabel [ "." ]
  88          if (preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string)) {
  89              return $string;
  90          }
  91  
  92          // If we have Net_IDNA2 support, we can support IRIs by
  93          // punycoding them. (This is the most portable thing to do,
  94          // since otherwise we have to assume browsers support
  95  
  96          if ($config->get('Core.EnableIDNA')) {
  97              $idna = new Net_IDNA2(array('encoding' => 'utf8', 'overlong' => false, 'strict' => true));
  98              // we need to encode each period separately
  99              $parts = explode('.', $string);
 100              try {
 101                  $new_parts = array();
 102                  foreach ($parts as $part) {
 103                      $encodable = false;
 104                      for ($i = 0, $c = strlen($part); $i < $c; $i++) {
 105                          if (ord($part[$i]) > 0x7a) {
 106                              $encodable = true;
 107                              break;
 108                          }
 109                      }
 110                      if (!$encodable) {
 111                          $new_parts[] = $part;
 112                      } else {
 113                          $new_parts[] = $idna->encode($part);
 114                      }
 115                  }
 116                  $string = implode('.', $new_parts);
 117                  if (preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string)) {
 118                      return $string;
 119                  }
 120              } catch (Exception $e) {
 121                  // XXX error reporting
 122              }
 123          }
 124          return false;
 125      }
 126  }
 127  
 128  // vim: et sw=4 sts=4