1 files changed, 85 insertions, 19 deletions

diff --git a/library/HTMLPurifier/AttrDef/URI/Host.php b/library/HTMLPurifier/AttrDef/URI/Host.php
index 2156c10c6..e7df800b1 100644
--- a/library/HTMLPurifier/AttrDef/URI/Host.php
+++ b/library/HTMLPurifier/AttrDef/URI/Host.php
@@ -7,56 +7,122 @@ class HTMLPurifier_AttrDef_URI_Host extends HTMLPurifier_AttrDef
 {
 
     /**
-     * Instance of HTMLPurifier_AttrDef_URI_IPv4 sub-validator
+     * IPv4 sub-validator.
+     * @type HTMLPurifier_AttrDef_URI_IPv4
      */
     protected $ipv4;
 
     /**
-     * Instance of HTMLPurifier_AttrDef_URI_IPv6 sub-validator
+     * IPv6 sub-validator.
+     * @type HTMLPurifier_AttrDef_URI_IPv6
      */
     protected $ipv6;
 
-    public function __construct() {
+    public function __construct()
+    {
         $this->ipv4 = new HTMLPurifier_AttrDef_URI_IPv4();
         $this->ipv6 = new HTMLPurifier_AttrDef_URI_IPv6();
     }
 
-    public function validate($string, $config, $context) {
+    /**
+     * @param string $string
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return bool|string
+     */
+    public function validate($string, $config, $context)
+    {
         $length = strlen($string);
-        if ($string === '') return '';
-        if ($length > 1 && $string[0] === '[' && $string[$length-1] === ']') {
+        // empty hostname is OK; it's usually semantically equivalent:
+        // the default host as defined by a URI scheme is used:
+        //
+        //      If the URI scheme defines a default for host, then that
+        //      default applies when the host subcomponent is undefined
+        //      or when the registered name is empty (zero length).
+        if ($string === '') {
+            return '';
+        }
+        if ($length > 1 && $string[0] === '[' && $string[$length - 1] === ']') {
             //IPv6
             $ip = substr($string, 1, $length - 2);
             $valid = $this->ipv6->validate($ip, $config, $context);
-            if ($valid === false) return false;
-            return '['. $valid . ']';
+            if ($valid === false) {
+                return false;
+            }
+            return '[' . $valid . ']';
         }
 
         // need to do checks on unusual encodings too
         $ipv4 = $this->ipv4->validate($string, $config, $context);
-        if ($ipv4 !== false) return $ipv4;
+        if ($ipv4 !== false) {
+            return $ipv4;
+        }
 
         // A regular domain name.
 
-        // This breaks I18N domain names, but we don't have proper IRI support,
-        // so force users to insert Punycode. If there's complaining we'll
-        // try to fix things into an international friendly form.
+        // This doesn't match I18N domain names, but we don't have proper IRI support,
+        // so force users to insert Punycode.
+
+        // There is not a good sense in which underscores should be
+        // allowed, since it's technically not! (And if you go as
+        // far to allow everything as specified by the DNS spec...
+        // well, that's literally everything, modulo some space limits
+        // for the components and the overall name (which, by the way,
+        // we are NOT checking!).  So we (arbitrarily) decide this:
+        // let's allow underscores wherever we would have allowed
+        // hyphens, if they are enabled.  This is a pretty good match
+        // for browser behavior, for example, a large number of browsers
+        // cannot handle foo_.example.com, but foo_bar.example.com is
+        // fairly well supported.
+        $underscore = $config->get('Core.AllowHostnameUnderscore') ? '_' : '';
 
         // The productions describing this are:
         $a   = '[a-z]';     // alpha
         $an  = '[a-z0-9]';  // alphanum
-        $and = '[a-z0-9-]'; // alphanum | "-"
+        $and = "[a-z0-9-$underscore]"; // alphanum | "-"
         // domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
-        $domainlabel   = "$an($and*$an)?";
+        $domainlabel = "$an($and*$an)?";
         // toplabel    = alpha | alpha *( alphanum | "-" ) alphanum
-        $toplabel      = "$a($and*$an)?";
+        $toplabel = "$a($and*$an)?";
         // hostname    = *( domainlabel "." ) toplabel [ "." ]
-        $match = preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string);
-        if (!$match) return false;
+        if (preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string)) {
+            return $string;
+        }
 
-        return $string;
-    }
+        // If we have Net_IDNA2 support, we can support IRIs by
+        // punycoding them. (This is the most portable thing to do,
+        // since otherwise we have to assume browsers support
 
+        if ($config->get('Core.EnableIDNA')) {
+            $idna = new Net_IDNA2(array('encoding' => 'utf8', 'overlong' => false, 'strict' => true));
+            // we need to encode each period separately
+            $parts = explode('.', $string);
+            try {
+                $new_parts = array();
+                foreach ($parts as $part) {
+                    $encodable = false;
+                    for ($i = 0, $c = strlen($part); $i < $c; $i++) {
+                        if (ord($part[$i]) > 0x7a) {
+                            $encodable = true;
+                            break;
+                        }
+                    }
+                    if (!$encodable) {
+                        $new_parts[] = $part;
+                    } else {
+                        $new_parts[] = $idna->encode($part);
+                    }
+                }
+                $string = implode('.', $new_parts);
+                if (preg_match("/^($domainlabel\.)*$toplabel\.?$/i", $string)) {
+                    return $string;
+                }
+            } catch (Exception $e) {
+                // XXX error reporting
+            }
+        }
+        return false;
+    }
 }
 
 // vim: et sw=4 sts=4