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recaptcha.class.php

<?php
/*
* This is a PHP library that handles calling reCAPTCHA.
*    - Documentation and latest version
*          http://recaptcha.net/plugins/php/
*    - Get a reCAPTCHA API Key
*          https://www.google.com/recaptcha/admin/create
*    - Discussion group
*          http://groups.google.com/group/recaptcha
*
* Copyright (c) 2007 reCAPTCHA -- http://recaptcha.net
* AUTHORS:
*   Mike Crawford
*   Ben Maurer
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

class recaptcha
{
  const RECAPTCHA_API_SERVER = 'http://www.google.com/recaptcha/api';
  const RECAPTCHA_API_SECURE_SERVER = 'https://www.google.com/recaptcha/api';

  const RECAPTCHA_VERIFY_SERVER = 'www.google.com';

  public $publickey;
  public $privatekey;

  private $error;

  /**
  * Encodes the given data into a query string format
  * @param $data - array of string elements to be encoded
  * @return string - encoded request
  */
  private function _recaptcha_qsencode($data)
  {
    $req = "";
    foreach ($data as $key => $value)
      $req .= $key . '=' . urlencode(stripslashes($value)) . '&';

    // Cut the last '&'
    $req = substr($req, 0, strlen($req) - 1);
    return $req;
  }

  /**
  * Submits an HTTP POST to a reCAPTCHA server
  * @param string $host
  * @param string $path
  * @param array $data
  * @param int port
  * @return array response
  */
  private function _recaptcha_http_post($host, $path, $data, $port = 80)
  {
    $req = $this -> _recaptcha_qsencode($data);

    $http_request = "POST $path HTTP/1.0\r\n";
    $http_request .= "Host: $host\r\n";
    $http_request .= "Content-Type: application/x-www-form-urlencoded;\r\n";
    $http_request .= "Content-Length: " . strlen($req) . "\r\n";
    $http_request .= "User-Agent: reCAPTCHA/PHP\r\n";
    $http_request .= "\r\n";
    $http_request .= $req;

    $response = '';
    if (false == ($fs = @fsockopen($host, $port, $errno, $errstr, 10)))
      die('Could not open socket');

    fwrite($fs, $http_request);

    while (!feof($fs))
      $response .= fgets($fs, 1160);

    // One TCP-IP packet
    fclose($fs);
    $response = explode("\r\n\r\n", $response, 2);

    return $response;
  }

  /**
  * Gets the challenge HTML (javascript and non-javascript version).
  * This is called from the browser, and the resulting reCAPTCHA HTML widget
  * is embedded within the HTML form it was called from.
  * @param string $pubkey A public key for reCAPTCHA
  * @param string $error The error given by reCAPTCHA (optional, default is null)
  * @param boolean $use_ssl Should the request be made over ssl? (optional, default is false)

  * @return string - The HTML to be embedded in the user's form.
  */
  public function get_html($use_ssl = false)
  {
    $pubkey = $this -> publickey;

    if ($pubkey == null || $pubkey == '')
      die("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");

    if ($use_ssl)
      $server = self::RECAPTCHA_API_SECURE_SERVER;
    else
      $server = self::RECAPTCHA_API_SERVER;

    $errorpart = "";
    if ($this -> error)
      $errorpart = "&amp;error=" . $this -> error;

    return '<script type="text/javascript" src="' . $server . '/challenge?k=' . $pubkey . $errorpart . '"></script>
    <noscript>
    <iframe src="' . $server . '/noscript?k=' . $pubkey . $errorpart . '" height="300" width="500" frameborder="0"></iframe><br/>
    <textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea>
    <input type="hidden" name="recaptcha_response_field" value="manual_challenge"/>
    </noscript>';
  }

  /**
  * Calls an HTTP POST function to verify if the user's guess was correct
  * @param string $privkey
  * @param string $remoteip
  * @param string $challenge
  * @param string $response
  * @param array $extra_params an array of extra variables to post to the server
  * @return ReCaptchaResponse
  */
  public function check_answer($remoteip, $challenge, $response, $extra_params = array())
  {
    $this -> resetError();
    $privkey = $this -> privatekey;

    if ($privkey == null || $privkey == '')
      die("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");

    if ($remoteip == null || $remoteip == '')
      die("For security reasons, you must pass the remote ip to reCAPTCHA");

    //discard spam submissions
    if ($challenge == null || strlen($challenge) == 0 || $response == null || strlen($response) == 0)
    {
      $this -> error = 'incorrect-captcha-sol';
      return false;
    }

    $response = $this -> _recaptcha_http_post(self::RECAPTCHA_VERIFY_SERVER, "/recaptcha/api/verify", array('privatekey' => $privkey, 'remoteip' => $remoteip, 'challenge' => $challenge, 'response' => $response) + $extra_params);

    $answers = explode("\n", $response[1]);

    if (trim($answers[0]) == 'true')
      return true;
    else
      $this -> error = $answers[1];
    return false;
  }

  /**
  * gets a URL where the user can sign up for reCAPTCHA. If your application
  * has a configuration page where you enter a key, you should provide a link
  * using this function.
  * @param string $domain The domain where the page is hosted
  * @param string $appname The name of your application
  */
  private function recaptcha_get_signup_url($domain = null, $appname = null)
  {
    return "https://www.google.com/recaptcha/admin/create?" . $this -> _recaptcha_qsencode(array('domains' => $domain, 'app' => $appname));
  }

  private function _recaptcha_aes_pad($val)
  {
    $block_size = 16;
    $numpad = $block_size - (strlen($val) % $block_size);
    return str_pad($val, strlen($val) + $numpad, chr($numpad));
  }

  /* Mailhide related code */

  private function _recaptcha_aes_encrypt($val, $ky)
  {
    if (!function_exists("mcrypt_encrypt"))
      die("To use reCAPTCHA Mailhide, you need to have the mcrypt php module installed.");

    $mode = MCRYPT_MODE_CBC;
    $enc = MCRYPT_RIJNDAEL_128;
    $val = $this -> _recaptcha_aes_pad($val);
    return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
  }

  private function _recaptcha_mailhide_urlbase64($x)
  {
    return strtr(base64_encode($x), '+/', '-_');
  }

  /* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
  public function mailhide_url($email)
  {
    $pubkey = $this -> publickey;
    $privkey = $this -> privatekey;

    if ($pubkey == '' || $pubkey == null || $privkey == "" || $privkey == null)
      die("To use reCAPTCHA Mailhide, you have to sign up for a public and private key, " . "you can do so at <a href='http://www.google.com/recaptcha/mailhide/apikey'>http://www.google.com/recaptcha/mailhide/apikey</a>");

    $ky = pack('H*', $privkey);
    $cryptmail = $this -> _recaptcha_aes_encrypt($email, $ky);

    return "http://www.google.com/recaptcha/mailhide/d?k=" . $pubkey . "&c=" . $this -> _recaptcha_mailhide_urlbase64($cryptmail);
  }

  /**
  * gets the parts of the email to expose to the user.
  * eg, given johndoe@example,com return ["john", "example.com"].
  * the email is then displayed as john...@example.com
  */
  private function _recaptcha_mailhide_email_parts($email)
  {
    $arr = preg_split("/@/", $email);

    if (strlen($arr[0]) <= 4)
      $arr[0] = substr($arr[0], 0, 1);
    else if (strlen($arr[0]) <= 6)
      $arr[0] = substr($arr[0], 0, 3);
    else
      $arr[0] = substr($arr[0], 0, 4);

    return $arr;
  }

  /**
  * Gets html to display an email address given a public an private key.
  * to get a key, go to:
  *
  * http://www.google.com/recaptcha/mailhide/apikey
  */
  public function mailhide_html($email)
  {
    $pubkey = $this -> publickey;
    $privkey = $this -> privatekey;

    $emailparts = $this -> _recaptcha_mailhide_email_parts($email);
    $url = $this -> mailhide_url($pubkey, $privkey, $email);

    return htmlentities($emailparts[0]) . "<a href='" . htmlentities($url) . "' onclick=\"window.open('" . htmlentities($url) . "', '', 'toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width=500,height=300'); return false;\" title=\"Reveal this e-mail address\">...</a>@" . htmlentities($emailparts[1]);
  }

  private function resetError()
  {
    $this -> error = NULL;
  }

  public function getError()
  {
    if ($this -> error)
      return $this -> error;
    return false;
  }
}
?>

probateko:
recaptcha.example.php

<?php
require_once('recaptcha.class.php');

$captcha = new recaptcha();
$captcha->privatekey = 'PRIVATEKEY';
$captcha->publickey = 'PUBLICKEY';

if ($_POST["recaptcha_response_field"])
{
  $resp = $captcha->check_answer
  (
    $_SERVER["REMOTE_ADDR"],
    $_POST["recaptcha_challenge_field"],
    $_POST["recaptcha_response_field"]
  );

  if ($resp)
    echo "You got it!";
  else
    echo $captcha->getError();
}
?>
<html>
<body>
<form action="" method="post">
<br/>
<?php
echo $captcha->get_html();
?>
<input type="submit" value="submit" />
</form>
</body>
</html>

mailhide:
recaptcha.mailhide.php

<?php
require_once ("recaptcha.class.php");
$captcha = new recaptcha();
$captcha->privatekey = 'PRIVATEKEY';
$captcha->publickey = 'PUBLICKEY';
?>
<html><body>
The Mailhide version of example@example.com is
<? echo $captcha->mailhide_html("example@example.com"); ?>. <br>

The url for the email is:
<? echo $captcha->mailhide_url ("example@example.com"); ?> <br>

</body></html>