FancyCaptcha.php

   1 <?php
   2
   3 if ( defined( 'MEDIAWIKI' ) ) {
   4
   5 global $wgCaptchaDirectory;
   6 $wgCaptchaDirectory = "$wgUploadDirectory/captcha"; // bad default :D
   7
   8 global $wgCaptchaSecret;
   9 $wgCaptchaSecret = "CHANGE_THIS_SECRET!";
  10
  11
  12 class FancyCaptcha extends SimpleCaptcha {
  13         function keyMatch() {
  14                 global $wgRequest, $wgCaptchaSecret;
  15
  16                 if( !isset( $_SESSION['ceAnswerVar'] ) ) {
  17                         wfDebug( "FancyCaptcha: no session captcha key set, this is new visitor.\n" );
  18                         return false;
  19                 }
  20
  21                 $var  = @$_SESSION['ceAnswerVar'];
  22                 $salt = @$_SESSION['captchaSalt'];
  23                 $hash = @$_SESSION['captchaHash'];
  24
  25                 $answer = $wgRequest->getVal( $var );
  26                 $digest = $wgCaptchaSecret . $salt . $answer . $wgCaptchaSecret . $salt;
  27                 $answerHash = substr( md5( $digest ), 0, 16 );
  28
  29                 if( $answerHash == $hash ) {
  30                         wfDebug( "FancyCaptcha: answer hash matches expected $hash\n" );
  31                         return true;
  32                 } else {
  33                         wfDebug( "FancyCaptcha: answer hashes to $answerHash, expected $hash\n" );
  34                         return false;
  35                 }
  36         }
  37
  38         /**
  39          * Insert the captcha prompt into the edit form.
  40          */
  41         function formCallback( &$out ) {
  42                 $dest = 'wpCaptchaWord' . mt_rand();
  43
  44                 $img = $this->pickImage();
  45                 if( !$img ) {
  46                         die( "out of captcha images; this shouldn't happen" );
  47                 }
  48
  49                 $_SESSION['ceAnswerVar'] = $dest;
  50                 $_SESSION['captchaHash'] = $img['hash'];
  51                 $_SESSION['captchaSalt'] = $img['salt'];
  52                 $_SESSION['captchaViewed'] = false;
  53                 wfDebug( "Picked captcha with hash ${img['hash']}, salt ${img['salt']}.\n" );
  54
  55                 $title = Title::makeTitle( NS_SPECIAL, 'Captcha/image' );
  56
  57                 $out->addWikiText( wfMsg( "captcha-short" ) );
  58                 $out->addHTML( "<p>" .
  59                         wfElement( 'img', array(
  60                                 'src'    => $title->getLocalUrl(),
  61                                 'width'  => $img['width'],
  62                                 'height' => $img['height'],
  63                                 'alt'    => '' ) ) .
  64                         "</p>\n" .
  65                         "<p><input name=\"$dest\" id=\"$dest\" tabindex=\"1\" /></p>" );
  66         }
  67
  68         /**
  69          * Select a previously generated captcha image from the queue.
  70          * @fixme subject to race conditions if lots of files vanish
  71          * @return mixed tuple of (salt key, text hash) or false if no image to find
  72          */
  73         function pickImage() {
  74                 global $wgCaptchaDirectory;
  75                 $pick = mt_rand( 0, $this->countFiles( $wgCaptchaDirectory ) );
  76                 $dir = opendir( $wgCaptchaDirectory );
  77
  78                 $n = mt_rand( 0, 16 );
  79                 $count = 0;
  80
  81                 $entry = readdir( $dir );
  82                 $pick = false;
  83                 while( false !== $entry ) {
  84                         $entry = readdir( $dir );
  85                         if( preg_match( '/^image_([0-9a-f]+)_([0-9a-f]+)\\.png$/', $entry, $matches ) ) {
  86                                 $size = getimagesize( "$wgCaptchaDirectory/$entry" );
  87                                 $pick = array(
  88                                         'salt' => $matches[1],
  89                                         'hash' => $matches[2],
  90                                         'width' => $size[0],
  91                                         'height' => $size[1]
  92                                 );
  93                                 if( $count++ == $n ) {
  94                                         break;
  95                                 }
  96                         }
  97                 }
  98                 closedir( $dir );
  99                 return $pick;
 100         }
 101
 102         /**
 103          * Count the number of files in a directory.
 104          * @return int
 105          */
 106         function countFiles( $dirname ) {
 107                 $dir = opendir( $dirname );
 108                 $count = 0;
 109                 while( false !== ($entry = readdir( $dir ) ) ) {
 110                         if( $dir != '.' && $dir != '..' ) {
 111                                 $count++;
 112                         }
 113                 }
 114                 closedir( $dir );
 115                 return $count;
 116         }
 117
 118         function showImage() {
 119                 global $wgOut;
 120                 $wgOut->disable();
 121                 if( !empty( $_SESSION['captchaViewed'] ) ) {
 122                         wfHttpError( 403, 'Access Forbidden', "Can't view captcha image a second time." );
 123                         return false;
 124                 }
 125                 $_SESSION['captchaViewed'] = wfTimestamp();
 126
 127                 if( isset( $_SESSION['captchaSalt'] ) ) {
 128                         $salt = $_SESSION['captchaSalt'];
 129                         if( isset( $_SESSION['captchaHash'] ) ) {
 130                                 $hash = $_SESSION['captchaHash'];
 131
 132                                 global $wgCaptchaDirectory;
 133                                 $file = $wgCaptchaDirectory . DIRECTORY_SEPARATOR . "image_{$salt}_{$hash}.png";
 134                                 if( file_exists( $file ) ) {
 135                                         header( 'Content-type: image/png' );
 136                                         readfile( $file );
 137                                 }
 138                         }
 139                 } else {
 140                         wfHttpError( 500, 'Internal Error', 'Requested bogus captcha image' );
 141                 }
 142         }
 143 }
 144
 145 } # End invocation guard
 146
 147 ?>