* save each captcha's session data separately, so multiple tabs/windows work
authorBrion Vibber <brion@users.mediawiki.org>
Fri, 27 Jan 2006 08:00:32 +0000 (08:00 +0000)
committerBrion Vibber <brion@users.mediawiki.org>
Fri, 27 Jan 2006 08:00:32 +0000 (08:00 +0000)
ConfirmEdit.php
FancyCaptcha.php

index 772c65eb3461e33bcee665bb923ed3127b07862b..cd1e04e1410358510dbb3848c95b0b3aca018af3 100644 (file)
@@ -1,10 +1,31 @@
 <?php
-
-# Prelim in-progress code. Proof of concept for framework, not
-# intended as a real production captcha system!
-
-# Loader for simple captcha feature
-# Include this from LocalSettings.php
+/**
+ * Experimental captcha plugin framework.
+ * Not intended as a real production captcha system; derived classes
+ * can extend the base to produce their fancy images in place of the
+ * text-based test output here.
+ *
+ * Copyright (C) 2005, 2006 Brion Vibber <brion@pobox.com>
+ * http://www.mediawiki.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @package MediaWiki
+ * @subpackage Extensions
+ */
 
 if ( defined( 'MEDIAWIKI' ) ) {
 
@@ -12,6 +33,14 @@ global $wgExtensionFunctions, $wgGroupPermissions;
 
 $wgExtensionFunctions[] = 'ceSetup';
 
+/**
+ * The 'skipcaptcha' permission key can be given out to
+ * let known-good users perform triggering actions without
+ * having to go through the captcha.
+ *
+ * By default, sysops and registered bot accounts will be
+ * able to skip, while others have to go through it.
+ */
 $wgGroupPermissions['*'            ]['skipcaptcha'] = false;
 $wgGroupPermissions['user'         ]['skipcaptcha'] = false;
 $wgGroupPermissions['autoconfirmed']['skipcaptcha'] = false;
@@ -22,6 +51,17 @@ global $wgCaptcha, $wgCaptchaClass, $wgCaptchaTriggers;
 $wgCaptcha = null;
 $wgCaptchaClass = 'SimpleCaptcha';
 
+/**
+ * Currently the captcha works only for page edits.
+ *
+ * If the 'edit' trigger is on, *every* edit will trigger the captcha.
+ * This may be useful for protecting against vandalbot attacks.
+ *
+ * If using the default 'addurl' trigger, the captcha will trigger on
+ * edits that include URLs that aren't in the current version of the page.
+ * This should catch automated linkspammers without annoying people when
+ * they make more typical edits.
+ */
 $wgCaptchaTriggers = array();
 $wgCaptchaTriggers['edit']   = false; // Would check on every edit
 $wgCaptchaTriggers['addurl'] = true;  // Check on edits that add URLs
@@ -87,6 +127,55 @@ function wfSpecialCaptcha( $par = null ) {
 }
 
 class SimpleCaptcha {
+       /**
+        * Insert a captcha prompt into the edit form.
+        * This sample implementation generates a simple arithmetic operation;
+        * it would be easy to defeat by machine.
+        *
+        * Override this!
+        *
+        * @param OutputPage $out
+        */
+       function formCallback( &$out ) {
+               $a = mt_rand(0, 100);
+               $b = mt_rand(0, 10);
+               $op = mt_rand(0, 1) ? '+' : '-';
+               
+               $test = "$a $op $b";
+               $answer = ($op == '+') ? ($a + $b) : ($a - $b);
+               
+               $index = $this->storeCaptcha( array( 'answer' => $answer ) );
+               
+               $out->addWikiText( wfMsg( "captcha-short" ) );  
+               $out->addHTML( "<p><label for=\"wpCaptchaWord\">$test</label> = " .
+                       wfElement( 'input', array(
+                               'name' => 'wpCaptchaWord',
+                               'id'   => 'wpCaptchaWord',
+                               'tabindex' => 1 ) ) . // tab in before the edit textarea
+                       "</p>\n" .
+                       wfElement( 'input', array(
+                               'type'  => 'hidden',
+                               'name'  => 'wpCaptchaId',
+                               'id'    => 'wpCaptchaId',
+                               'value' => $index ) ) );
+       }
+       
+       /**
+        * Check if the submitted form matches the captcha session data provided
+        * by the plugin when the form was generated.
+        *
+        * Override this!
+        *
+        * @param WebRequest $request
+        * @param array $info
+        * @return bool
+        */
+       function keyMatch( $request, $info ) {
+               return $request->getVal( 'wpCaptchaWord' ) == $info['answer'];
+       }
+       
+       // ----------------------------------
+       
        /**
         * @param EditPage $editPage
         * @param string $newtext
@@ -96,21 +185,21 @@ class SimpleCaptcha {
        function shouldCheck( &$editPage, $newtext, $section ) {
                global $wgUser;
                if( $wgUser->isAllowed( 'skipcaptcha' ) ) {
-                       wfDebug( "SimpleCaptcha: user group allows skipping captcha\n" );
+                       wfDebug( "ConfirmEdit: user group allows skipping captcha\n" );
                        return false;
                }
        
                global $wgEmailAuthentication, $ceAllowConfirmedEmail;
                if( $wgEmailAuthentication && $ceAllowConfirmedEmail &&
                        $wgUser->isEmailConfirmed() ) {
-                       wfDebug( "SimpleCaptcha: user has confirmed mail, skipping captcha\n" );
+                       wfDebug( "ConfirmEdit: user has confirmed mail, skipping captcha\n" );
                        return false;
                }
                
                global $wgCaptchaTriggers;
                if( !empty( $wgCaptchaTriggers['edit'] ) ) {
                        // Check on all edits
-                       wfDebug( "SimpleCaptcha: checking all edits...\n" );
+                       wfDebug( "ConfirmEdit: checking all edits...\n" );
                        return true;
                }
                
@@ -138,52 +227,77 @@ class SimpleCaptcha {
                return false;
        }
        
+       /**
+        * The main callback run on edit attempts.
+        * @param EditPage $editPage
+        * @param string $newtext
+        * @param string $section
+        * @param bool true to continue saving, false to abort and show a captcha form
+        */
        function confirmEdit( &$editPage, $newtext, $section ) {
                if( $this->shouldCheck( $editPage, $newtext, $section ) ) {
-                       if( $this->keyMatch() ) {
-                               wfDebug( "ConfirmEdit given proper key from form, passing.\n" );
-                               return true;
+                       $info = $this->retrieveCaptcha();
+                       if( $info ) {
+                               global $wgRequest;
+                               if( $this->keyMatch( $wgRequest, $info ) ) {
+                                       wfDebug( "ConfirmEdit given proper key from form, passing.\n" );
+                                       return true;
+                               } else {
+                                       wfDebug( "ConfirmEdit missing form key, prompting.\n" );
+                               }
                        } else {
-                               wfDebug( "ConfirmEdit missing form key, prompting.\n" );
-                               $editPage->showEditForm( array( &$this, 'formCallback' ) );
-                               return false;
+                               wfDebug( "ConfirmEdit: no session captcha key set, this is new visitor.\n" );
                        }
+                       $editPage->showEditForm( array( &$this, 'formCallback' ) );
+                       return false;
                } else {
                        wfDebug( "ConfirmEdit: no new links.\n" );
                        return true;
                }
        }
        
-       function keyMatch() {
-               if( !isset( $_SESSION['ceAnswerVar'] ) ) {
-                       wfDebug( "ConfirmEdit no session captcha key set, this is new visitor.\n" );
-                       return false;
+       /**
+        * Generate a captcha session ID and save the info in PHP's session storage.
+        * (Requires the user to have cookies enabled to get through the captcha.)
+        *
+        * A random ID is used so legit users can make edits in multiple tabs or
+        * windows without being unnecessarily hobbled by a serial order requirement.
+        * Pass the returned id value into the edit form as wpCaptchaId.
+        *
+        * @param array $info data to store
+        * @param string $index optional, to overwrite used session
+        * @return string captcha ID key
+        */
+       function storeCaptcha( $info, $index=null ) {
+               if( is_null( $index ) ) {
+                       $index = strval( mt_rand() );
+                       $info['index'] = $index;
                }
-               global $wgRequest;
-               return $wgRequest->getVal( $_SESSION['ceAnswerVar'] ) == $_SESSION['ceAnswer'];
+               $_SESSION['captcha' . $index] = $info;
+               return $index;
        }
        
-       function formCallback( &$out ) {
-               $source = 'ceSource' . mt_rand();
-               $dest = 'ceConfirm' . mt_rand();
-               
-               $a = mt_rand(0, 100);
-               $b = mt_rand(0, 10);
-               $op = mt_rand(0, 1) ? '+' : '-';
-               
-               $test = "$a $op $b";
-               $answer = ($op == '+') ? ($a + $b) : ($a - $b);
-               $_SESSION['ceAnswer'] = $answer;
-               $_SESSION['ceAnswerVar'] = $dest;
-               
-               
-               $out->addWikiText( wfMsg( "captcha-short" ) );  
-               $out->addHTML( <<<END
-                       <p><span id="$source"><label for="$dest">$test</label></span> = <input name="$dest" id="$dest" /></p>
-END
-                       );
+       /**
+        * Fetch this session's captcha info.
+        * @return mixed array of info, or false if missing
+        */
+       function retrieveCaptcha() {
+               global $wgRequest;
+               $index = $wgRequest->getVal( 'wpCaptchaId' );
+               if( isset( $_SESSION['captcha' . $index] ) ) {
+                       return $_SESSION['captcha' . $index];
+               } else {
+                       return false;
+               }
        }
        
+       /**
+        * Retrieve the current version of the page or section being edited...
+        * @param EditPage $editPage
+        * @param string $section
+        * @return string
+        * @access private
+        */
        function loadText( $editPage, $section ) {
                $rev = Revision::newFromTitle( $editPage->mTitle );
                if( is_null( $rev ) ) {
@@ -198,6 +312,11 @@ END
                }
        }
        
+       /**
+        * Extract a list of all recognized HTTP links in the text.
+        * @param string $text
+        * @return array of strings
+        */
        function findLinks( $text ) {
                $regex = '/((?:' . HTTP_PROTOCOLS . ')' . EXT_LINK_URL_CLASS . '+)/';
                
@@ -208,6 +327,9 @@ END
                }
        }
        
+       /**
+        * Show a page explaining what this wacky thing is.
+        */
        function showHelp() {
                global $wgOut, $ceAllowConfirmedEmail;
                $wgOut->setPageTitle( wfMsg( 'captchahelp-title' ) );
index ec867e8739d57b850b80b71d1898306e3bc1aaa9..4a6b438e4ce3ced0161fb1915ec40ec0317f69a1 100644 (file)
@@ -1,4 +1,29 @@
 <?php
+/**
+ * Experimental image-based captcha plugin, using images generated by an
+ * external tool.
+ *
+ * Copyright (C) 2005, 2006 Brion Vibber <brion@pobox.com>
+ * http://www.mediawiki.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @package MediaWiki
+ * @subpackage Extensions
+ */
 
 if ( defined( 'MEDIAWIKI' ) ) {
 
@@ -10,27 +35,26 @@ $wgCaptchaSecret = "CHANGE_THIS_SECRET!";
 
 
 class FancyCaptcha extends SimpleCaptcha {
-       function keyMatch() {
-               global $wgRequest, $wgCaptchaSecret;
-               
-               if( !isset( $_SESSION['ceAnswerVar'] ) ) {
-                       wfDebug( "FancyCaptcha: no session captcha key set, this is new visitor.\n" );
-                       return false;
-               }
-               
-               $var  = @$_SESSION['ceAnswerVar'];
-               $salt = @$_SESSION['captchaSalt'];
-               $hash = @$_SESSION['captchaHash'];
+       /**
+        * Check if the submitted form matches the captcha session data provided
+        * by the plugin when the form was generated.
+        *
+        * @param WebRequest $request
+        * @param array $info
+        * @return bool
+        */
+       function keyMatch( $request, $info ) {
+               global $wgCaptchaSecret;
                
-               $answer = $wgRequest->getVal( $var );
-               $digest = $wgCaptchaSecret . $salt . $answer . $wgCaptchaSecret . $salt;
+               $answer = $request->getVal( 'wpCaptchaWord' );
+               $digest = $wgCaptchaSecret . $info['salt'] . $answer . $wgCaptchaSecret . $info['salt'];
                $answerHash = substr( md5( $digest ), 0, 16 );
                
-               if( $answerHash == $hash ) {
+               if( $answerHash == $info['hash'] ) {
                        wfDebug( "FancyCaptcha: answer hash matches expected $hash\n" );
                        return true;
                } else {
-                       wfDebug( "FancyCaptcha: answer hashes to $answerHash, expected $hash\n" );
+                       wfDebug( "FancyCaptcha: answer hashes to $answerHash, expected {$info['hash']}\n" );
                        return false;
                }
        }
@@ -39,30 +63,40 @@ class FancyCaptcha extends SimpleCaptcha {
         * Insert the captcha prompt into the edit form.
         */
        function formCallback( &$out ) {
-               $dest = 'wpCaptchaWord' . mt_rand();
-               
-               $img = $this->pickImage();
-               if( !$img ) {
+               $info = $this->pickImage();
+               if( !$info ) {
                        die( "out of captcha images; this shouldn't happen" );
                }
                
-               $_SESSION['ceAnswerVar'] = $dest;
-               $_SESSION['captchaHash'] = $img['hash'];
-               $_SESSION['captchaSalt'] = $img['salt'];
-               $_SESSION['captchaViewed'] = false;
-               wfDebug( "Picked captcha with hash ${img['hash']}, salt ${img['salt']}.\n" );
+               // Generate a random key for use of this captcha image in this session.
+               // This is needed so multiple edits in separate tabs or windows can
+               // go through without extra pain.
+               $index = $this->storeCaptcha( $info );
+               
+               wfDebug( "Captcha id $index using hash ${info['hash']}, salt ${info['salt']}.\n" );
                
                $title = Title::makeTitle( NS_SPECIAL, 'Captcha/image' );
                
-               $out->addWikiText( wfMsg( "captcha-short" ) );  
+               $out->addWikiText( wfMsg( "captcha-short" ) );
+               
                $out->addHTML( "<p>" . 
                        wfElement( 'img', array(
-                               'src'    => $title->getLocalUrl(),
-                               'width'  => $img['width'],
-                               'height' => $img['height'],
+                               'src'    => $title->getLocalUrl( 'wpCaptchaId=' . urlencode( $index ) ),
+                               'width'  => $info['width'],
+                               'height' => $info['height'],
                                'alt'    => '' ) ) .
                        "</p>\n" .
-                       "<p><input name=\"$dest\" id=\"$dest\" tabindex=\"1\" /></p>" );
+                       wfElement( 'input', array(
+                               'type'  => 'hidden',
+                               'name'  => 'wpCaptchaId',
+                               'id'    => 'wpCaptchaId',
+                               'value' => $index ) ) .
+                       "<p>" .
+                       wfElement( 'input', array(
+                               'name' => 'wpCaptchaWord',
+                               'id'   => 'wpCaptchaWord',
+                               'tabindex' => 1 ) ) . // tab in before the edit textarea
+                       "</p>\n" );
        }
        
        /**
@@ -88,7 +122,8 @@ class FancyCaptcha extends SimpleCaptcha {
                                        'salt' => $matches[1],
                                        'hash' => $matches[2],
                                        'width' => $size[0],
-                                       'height' => $size[1]
+                                       'height' => $size[1],
+                                       'viewed' => false,
                                );
                                if( $count++ == $n ) {
                                        break;
@@ -116,29 +151,33 @@ class FancyCaptcha extends SimpleCaptcha {
        }
        
        function showImage() {
-               global $wgOut;
+               global $wgOut, $wgRequest;
+               global $wgCaptchaDirectory;
+               
                $wgOut->disable();
-               if( !empty( $_SESSION['captchaViewed'] ) ) {
-                       wfHttpError( 403, 'Access Forbidden', "Can't view captcha image a second time." );
-                       return false;
-               }
-               $_SESSION['captchaViewed'] = wfTimestamp();
                
-               if( isset( $_SESSION['captchaSalt'] ) ) {
-                       $salt = $_SESSION['captchaSalt'];
-                       if( isset( $_SESSION['captchaHash'] ) ) {
-                               $hash = $_SESSION['captchaHash'];
-                               
-                               global $wgCaptchaDirectory;
-                               $file = $wgCaptchaDirectory . DIRECTORY_SEPARATOR . "image_{$salt}_{$hash}.png";
-                               if( file_exists( $file ) ) {
-                                       header( 'Content-type: image/png' );
-                                       readfile( $file );
-                               }
+               $info = $this->retrieveCaptcha();
+               if( $info ) {
+                       if( $info['viewed'] ) {
+                               wfHttpError( 403, 'Access Forbidden', "Can't view captcha image a second time." );
+                               return false;
+                       }
+                       
+                       $info['viewed'] = wfTimestamp();
+                       $this->storeCaptcha( $info, $info['index'] );
+                       
+                       $salt = $info['salt'];
+                       $hash = $info['hash'];
+                       $file = $wgCaptchaDirectory . DIRECTORY_SEPARATOR . "image_{$salt}_{$hash}.png";
+                       
+                       if( file_exists( $file ) ) {
+                               header( 'Content-type: image/png' );
+                               readfile( $file );
+                               return true;
                        }
-               } else {
-                       wfHttpError( 500, 'Internal Error', 'Requested bogus captcha image' );
                }
+               wfHttpError( 500, 'Internal Error', 'Requested bogus captcha image' );
+               return false;
        }
 }