Implement %HTML.TargetBlank

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

library/HTMLPurifier/AttrTransform/TargetBlank.php

@@ -0,0 +1,38 @@
+<?php
+
+// must be called POST validation
+
+/**
+ * Adds target="blank" to all outbound links.  This transform is
+ * only attached if Attr.TargetBlank is TRUE.  This works regardless
+ * of whether or not Attr.AllowedFrameTargets
+ */
+class HTMLPurifier_AttrTransform_TargetBlank extends HTMLPurifier_AttrTransform
+{
+    private $parser;
+
+    public function __construct() {
+        $this->parser = new HTMLPurifier_URIParser();
+    }
+
+    public function transform($attr, $config, $context) {
+
+        if (!isset($attr['href'])) {
+            return $attr;
+        }
+
+        // XXX Kind of inefficient
+        $url = $this->parser->parse($attr['href']);
+        $scheme = $url->getSchemeObj($config, $context);
+
+        if ($scheme->browsable && !$url->isBenign($config, $context)) {
+            $attr['target'] = 'blank';
+        }
+
+        return $attr;
+
+    }
+
+}
+
+// vim: et sw=4 sts=4

library/HTMLPurifier/ConfigSchema/schema/HTML.TargetBlank.txt

@@ -0,0 +1,8 @@
+HTML.TargetBlank
+TYPE: bool
+VERSION: 4.3.1
+DEFAULT: FALSE
+--DESCRIPTION--
+If enabled, <code>target=blank</code> attributes are added to all outgoing links.
+(This includes links from an HTTPS version of a page to an HTTP version.)
+--# vim: et sw=4 sts=4

library/HTMLPurifier/HTMLModule/TargetBlank.php

@@ -0,0 +1,19 @@
+<?php
+
+/**
+ * Module adds the target=blank attribute transformation to a tags.  It
+ * is enabled by HTML.TargetBlank
+ */
+class HTMLPurifier_HTMLModule_TargetBlank extends HTMLPurifier_HTMLModule
+{
+
+    public $name = 'TargetBlank';
+
+    public function setup($config) {
+        $a = $this->addBlankElement('a');
+        $a->attr_transform_post[] = new HTMLPurifier_AttrTransform_TargetBlank();
+    }
+
+}
+
+// vim: et sw=4 sts=4

library/HTMLPurifier/HTMLModuleManager.php

@@ -229,6 +229,9 @@ class HTMLPurifier_HTMLModuleManager
         if ($config->get('HTML.Nofollow')) {
             $modules[] = 'Nofollow';
         }
+        if ($config->get('HTML.TargetBlank')) {
+            $modules[] = 'TargetBlank';
+        }
 
         // merge in custom modules
         $modules = array_merge($modules, $this->userModules);