Proxy Detector

<?
/**
* Proxy Detector v0.1
*  copyrights by: Daantje Eeltink (me@daantje.nl)
*      http://www.daantje.nl
*
*  first build: Mon Sep 18 21:43:48 CEST 2006
*  last build: Tue Sep 19 10:37:12 CEST 2006
*
* Description:
*  This class can detect if a visitor uses a proxy server by scanning the
*  headers returned by the user client. When the user uses a proxy server,
*  most of the proxy servers alter the header. The header is returned to
*  PHP in the array $_SERVER.
*
* License:
*  GPL v2 licence. (http://www.gnu.org/copyleft/gpl.txt)
*
* Support:
*  If you like this class and find it usefull, please donate one or two
*  coins to my PayPal account me@daantje.nl
*
* Todo:
*  Add open proxy black list scan.
*/

class proxy_detector {

 /**
 * CONSTRUCTOR
 * Set defaults...
 */
 function proxy_detector(){
  $this->config = array();
  $this->lastLog = "";

        //set default headers
  $this->scan_headers = array(
   'HTTP_VIA',
   'HTTP_X_FORWARDED_FOR',
   'HTTP_FORWARDED_FOR',
   'HTTP_X_FORWARDED',
   'HTTP_FORWARDED',
   'HTTP_CLIENT_IP',
   'HTTP_FORWARDED_FOR_IP',
   'VIA',
   'X_FORWARDED_FOR',
   'FORWARDED_FOR',
   'X_FORWARDED',
   'FORWARDED',
   'CLIENT_IP',
   'FORWARDED_FOR_IP',
   'HTTP_PROXY_CONNECTION'
  );
 }


 /**
 * VOID setHeader( STRING $trigger )
 * Set new header trigger...
 */
 function setHeader($trigger){
  $this->scan_headers[] = $trigger;
 }


 /**
 * ARRAY $triggers = getHeaders( VOID )
 * Get all triggers in one array
 */
 function getHeaders(){
     return $this->scan_headers;
 }


 /**
 * VOID setConfig( STRING $key,  STRING $value)
 * Set config line...
 */
 function setConfig($key,$value){
  $this->config[$key] = $value;
 }


 /**
 * MIXED $config = getConfig( [STRING $key] )
 * Get all config in one array, or only one config value as a string.
 */
 function getConfig($key=''){
     if($key)
      return $this->config[$key];
     else
      return $this->config;
 }


 /**
 * STRING $log = getLog( VOID )
 * Get last logged information. Only works AFTER calling detect()!
 */
 function getLog(){
  return $this->lastLog;
 }


 /**
 * BOOL $proxy = detect( VOID )
 * Start detection and return true if a proxy server is detected...
 */
 function detect(){
  $log = "";

  //scan all headers
  foreach($this->scan_headers as $i){
   //proxy detected? lets log...
   if($_SERVER[$i])
    $log.= "trigger $i: ".$_SERVER[$i]."\n";
  }

     //let's do something...
  if($log){
   $log = $this->lastLog = date("Y-m-d H:i:s")
."\nDetected proxy server: "
.gethostbyaddr($_SERVER['REMOTE_ADDR'])." ({$_SERVER['REMOTE_ADDR']})\n".$log;

   //mail message
            if($this->getConfig('MAIL_ALERT_TO'))
    mail($this->getConfig('MAIL_ALERT_TO'),"
    Proxy detected at {$_SERVER['REQUEST_URI']}",$log);

   //write to file
   $f = $this->getConfig('LOG_FILE');
            if($f){
    if(is_writable($f)){
     $fp = fopen($f,'a');
     fwrite($fp,"$log\n");
     fclose($fp);
             }else{
     die("<strong>Fatal Error:</strong> Couldn't write to file: 
'<strong>$f</strong>'<br>
Please check if the path exists and is writable for the webserver or php...");
             }
            }

   //done
   return true;
  }

  //nope, no proxy was logged...
  return false;
 }
}

?>

Browsing the code you will notice that it uses a log file to store the data so we will have to create one called "
proxy_detector.log". Don't forget to give it the proper permission on the server (CHMOD it to make it writable).



Ok so we already have 2 files. Let's go ahead and create a new one called "proxy_detector.inc.php"
.This one will initiate our class for our future use and do what we want it to do so I suggest you to edit it to suit your needs. Copy paste this code and save it:

<?
/**
* Proxy Detector v0.1
* Implementation example.
*
* Mon Sep 18 23:29:47 CEST 2006
* by: me@daantje.nl
*
* Documentation:
*  I use this file as an include at the top of some php files
*  to block proxy users from the scripts that included this file.
*
*  This file is only an example on how to implement the detector class.
*  But it could be usefull as is...
*
*  Check the remarks in the class for more documentation.
*/

//include detector class, assuming it's in the same directory as this file...
include_once(dirname(__FILE__)."/proxy_detector.class.php");

//init class
$proxy = new proxy_detector();

//set optional extra triggers, no need to... 
//I think I've got all of them covered in the class...
// $proxy->setTrigger('HTTP_SOME_HEADER_1');
// $proxy->setTrigger('HTTP_SOME_HEADER_2');

//set optional config
// $proxy->setConfig('MAIL_ALERT_TO','me@daantje.nl');
// $proxy->setConfig('LOG_FILE','/home/daantje/public_html/proxy/proxy_detector.log');

//start detect
if($proxy->detect()){

    //returned true, lets die...
 echo "<h1>Proxy detected</h1>";
 echo "
 Please disable your proxy server in your browser preferences or internet settings,
 and try again.<br><br>";

 //parse logged info
 echo nl2br($proxy->getLog());

    //some credits...
 echo "<hr><strong>proxy detector v0.1</strong> 
- &copy;2006 < a href=\"http://www.daantje.nl\" 
target=\"_blank\">daantje.nl</a>";

 //and do nothing anymore! (but not in my example)
 //exit();
}

//else, proceed as normal, put your code here...
?>