/lib/recaptchalib.php

<?php

/*

 * This is a PHP library that handles calling reCAPTCHA.

 *    - Documentation and latest version

 *          {@link http://code.google.com/apis/recaptcha/docs/php.html}

 *    - Get a reCAPTCHA API Key

 *          {@link https://www.google.com/recaptcha/admin/create}

 *    - Discussion group

 *          http://groups.google.com/group/recaptcha

 *

 * Copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}

 * 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.

 *

 * @package moodlecore

 * @copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}

 */



/**

 * The reCAPTCHA server URL's

 */

define("RECAPTCHA_API_SERVER", "http://www.google.com/recaptcha/api");

define("RECAPTCHA_API_SECURE_SERVER", "https://www.google.com/recaptcha/api");

define("RECAPTCHA_VERIFY_SERVER", "www.google.com");



/**

 * Encodes the given data into a query string format

 * @param $data - array of string elements to be encoded

 * @return string - encoded request

 */

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

 */

function _recaptcha_http_post($host, $path, $data, $port = 80, $https=false) {

        global $CFG;

        $protocol = 'http';

        if ($https) {

            $protocol = 'https';

        }



        require_once $CFG->libdir . '/filelib.php';



        $req = _recaptcha_qsencode ($data);



        $headers = array();

        $headers['Host'] = $host;

        $headers['Content-Type'] = 'application/x-www-form-urlencoded';

        $headers['Content-Length'] = strlen($req);

        $headers['User-Agent'] = 'reCAPTCHA/PHP';

        

        $results = download_file_content("$protocol://" . $host . $path, $headers, $data, false, 300, 20, true);



        if ($results) {

            return array(1 => $results);

        } else {

            return false;

        }

}







/**

 * 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.

 */

function recaptcha_get_html ($pubkey, $error = null, $use_ssl = false) {

    global $CFG;



    $recaptchatype = optional_param('recaptcha', 'image', PARAM_TEXT);



    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 = RECAPTCHA_API_SECURE_SERVER;

    } else {

        $server = RECAPTCHA_API_SERVER;

    }



        $errorpart = "";

        if ($error) {

           $errorpart = "&amp;error=" . $error;

        }



    require_once $CFG->libdir . '/filelib.php';

    $html = download_file_content($server . '/noscript?k=' . $pubkey . $errorpart, null, null, false, 300, 20, true);

    preg_match('/image\?c\=([A-Za-z0-9\-\_]*)\"/', $html, $matches);

    $challenge_hash = $matches[1];

    $image_url = $server . '/image?c=' . $challenge_hash;

    

    $strincorrectpleasetryagain = get_string('incorrectpleasetryagain', 'auth');

    $strenterthewordsabove = get_string('enterthewordsabove', 'auth');

    $strenterthenumbersyouhear = get_string('enterthenumbersyouhear', 'auth');

    $strgetanothercaptcha = get_string('getanothercaptcha', 'auth');

    $strgetanaudiocaptcha = get_string('getanaudiocaptcha', 'auth');

    $strgetanimagecaptcha = get_string('getanimagecaptcha', 'auth');

    

    $return = '<script type="text/javascript" src="'. $server . '/challenge?k=' . $pubkey . $errorpart . '"></script> 

	<noscript>

        <div id="recaptcha_widget_noscript">

        <div id="recaptcha_image_noscript"><img src="' . $image_url . '" alt="reCAPTCHA"/></div>';

    

    if ($error == 'incorrect-captcha-sol') {

        $return .= '<div class="recaptcha_only_if_incorrect_sol" style="color:red">' . $strincorrectpleasetryagain . '</div>';

    }



    if ($recaptchatype == 'image') {

        $return .= '<span class="recaptcha_only_if_image">' . $strenterthewordsabove . '</span>';

    } elseif ($recaptchatype == 'audio') {

        $return .= '<span class="recaptcha_only_if_audio">' . $strenterthenumbersyouhear . '</span>'; 

    }

    

    $return .= '<input type="text" id="recaptcha_response_field_noscript" name="recaptcha_response_field" />';

    $return .= '<input type="hidden" id="recaptcha_challenge_field_noscript" name="recaptcha_challenge_field" value="' . $challenge_hash . '" />';

    $return .= '<div><a href="signup.php">' . $strgetanothercaptcha . '</a></div>';

    

    // Disabling audio recaptchas for now: not language-independent

    /*

    if ($recaptchatype == 'image') {

        $return .= '<div class="recaptcha_only_if_image"><a href="signup.php?recaptcha=audio">' . $strgetanaudiocaptcha . '</a></div>';

    } elseif ($recaptchatype == 'audio') {

        $return .= '<div class="recaptcha_only_if_audio"><a href="signup.php?recaptcha=image">' . $strgetanimagecaptcha . '</a></div>';

    }

    */



    $return .= '

        </div>

	</noscript>';



    return $return;

}









/**

 * A ReCaptchaResponse is returned from recaptcha_check_answer()

 *

 * @package moodlecore

 * @copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}

 */

class ReCaptchaResponse {

        var $is_valid;

        var $error;

}





/**

  * 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

  * @return ReCaptchaResponse

  */

function recaptcha_check_answer ($privkey, $remoteip, $challenge, $response, $https=false)

{

    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) {

                $recaptcha_response = new ReCaptchaResponse();

                $recaptcha_response->is_valid = false;

                $recaptcha_response->error = 'incorrect-captcha-sol';

                return $recaptcha_response;

        }



        $response = _recaptcha_http_post(RECAPTCHA_VERIFY_SERVER, "/recaptcha/api/verify",

                                         array (

                                                'privatekey' => $privkey,

                                                'remoteip' => $remoteip,

                                                'challenge' => $challenge,

                                                'response' => $response

                                                ),

                                         $https        

                                          );



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

        $recaptcha_response = new ReCaptchaResponse();



        if (trim ($answers [0]) == 'true') {

                $recaptcha_response->is_valid = true;

        }

        else {

                $recaptcha_response->is_valid = false;

                $recaptcha_response->error = $answers [1];

        }

        return $recaptcha_response;



}



/**

 * 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

 */

function recaptcha_get_signup_url ($domain = null, $appname = null) {

	return "https://www.google.com/recaptcha/admin/create?" .  _recaptcha_qsencode (array ('domains' => $domain, 'app' => $appname));

}



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 */



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;

	$val=_recaptcha_aes_pad($val);

	return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");

}





function _recaptcha_mailhide_urlbase64 ($x) {

	return strtr(base64_encode ($x), '+/', '-_');

}



/* gets the reCAPTCHA Mailhide url for a given email, public key and private key */

function recaptcha_mailhide_url($pubkey, $privkey, $email) {

    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);

    $cryptmail = _recaptcha_aes_encrypt ($email, $ky);



	return "http://www.google.com/recaptcha/mailhide/d?k=" . $pubkey . "&c=" . _recaptcha_mailhide_urlbase64 ($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

 */

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

 */

function recaptcha_mailhide_html($pubkey, $privkey, $email) {

	$emailparts = _recaptcha_mailhide_email_parts ($email);

	$url = recaptcha_mailhide_url ($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]);



}





?>