Add alternative session storage for captcha data using $wgMemc, if

wgCaptchaStorageClass is set to 'CaptchaCacheStore' (custom classes
are also possible).
Enables use of captchas by anons with cookies disabled, so long as
the object cache system is set up for general caching.

diff --git a/ConfirmEdit.php b/ConfirmEdit.php
index 81ba905d6aec5417ff99c57535b39615bedcbfb9..4798c0fcb2314fddcb3b87d7dfe032589bad0169 100644 (file)
--- a/ConfirmEdit.php
+++ b/ConfirmEdit.php
@@ -75,6 +75,27 @@ $wgCaptchaTriggers['edit']          = false; // Would check on every edit
 $wgCaptchaTriggers['addurl']        = true;  // Check on edits that add URLs
 $wgCaptchaTriggers['createaccount'] = true;  // Special:Userlogin&type=signup
 
+/**
+ * Indicate how to store per-session data required to match up the
+ * internal captcha data with the editor.
+ *
+ * 'CaptchaSessionStore' uses PHP's session storage, which is cookie-based
+ * and may fail for anons with cookies disabled.
+ *
+ * 'CaptchaCacheStore' uses $wgMemc, which avoids the cookie dependency
+ * but may be fragile depending on cache configuration.
+ */
+global $wgCaptchaStorageClass;
+$wgCaptchaStorageClass = 'CaptchaSessionStore';
+
+/**
+ * Number of sections a captcha session should last in the data cache
+ * before expiring when managing through CaptchaCacheStore class.
+ *
+ * Default is a half hour.
+ */
+global $wgCaptchaSessionExpiration;
+$wgCaptchaSessionExpiration = 30 * 60;
 
 /**
  * Allow users who have confirmed their e-mail addresses to post
@@ -139,6 +160,11 @@ function wfSpecialCaptcha( $par = null ) {
 }
 
 class SimpleCaptcha {
+       function __construct() {
+               global $wgCaptchaStorageClass;
+               $this->storage = new $wgCaptchaStorageClass;
+       }
+       
        /**
         * Insert a captcha prompt into the edit form.
         * This sample implementation generates a simple arithmetic operation;
@@ -412,7 +438,7 @@ class SimpleCaptcha {
                        // Assign random index if we're not udpating
                        $info['index'] = strval( mt_rand() );
                }
-               $_SESSION['captcha' . $info['index']] = $info;
+               $this->storage->store( $info['index'], $info );
                return $info['index'];
        }
 
@@ -423,11 +449,7 @@ class SimpleCaptcha {
        function retrieveCaptcha() {
                global $wgRequest;
                $index = $wgRequest->getVal( 'wpCaptchaId' );
-               if( isset( $_SESSION['captcha' . $index] ) ) {
-                       return $_SESSION['captcha' . $index];
-               } else {
-                       return false;
-               }
+               return $this->storage->retrieve( $index );
        }
 
        /**
@@ -435,7 +457,7 @@ class SimpleCaptcha {
         * it can't be reused.
         */
        function clearCaptcha( $info ) {
-               unset( $_SESSION['captcha' . $info['index']] );
+               $this->storage->clear( $info['index'] );
        }
 
        /**
@@ -485,6 +507,47 @@ class SimpleCaptcha {
 
 }
 
+class CaptchaSessionStore {
+       function store( $index, $info ) {
+               $_SESSION['captcha' . $info['index']] = $info;
+       }
+       
+       function retrieve( $index ) {
+               if( isset( $_SESSION['captcha' . $index] ) ) {
+                       return $_SESSION['captcha' . $index];
+               } else {
+                       return false;
+               }
+       }
+       
+       function clear( $index ) {
+               unset( $_SESSION['captcha' . $index] );
+       }
+}
+
+class CaptchaCacheStore {
+       function store( $index, $info ) {
+               global $wgMemc, $wgCaptchaSessionExpiration;
+               $wgMemc->set( wfMemcKey( 'captcha', $index ), $info,
+                       $wgCaptchaSessionExpiration );
+       }
+
+       function retrieve( $index ) {
+               global $wgMemc;
+               $info = $wgMemc->get( wfMemcKey( 'captcha', $index ) );
+               if( $info ) {
+                       return $info;
+               } else {
+                       return false;
+               }
+       }
+       
+       function clear( $index ) {
+               global $wgMemc;
+               $wgMemc->delete( wfMemcKey( 'captcha', $index ) );
+       }
+}
+
 } # End invocation guard
 
 ?>