<?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.
 */

/**
 * 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)
{
    $req = _recaptcha_qsencode($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 $use_ssl Should the request be made over ssl? (optional, default is false)
 * @return string - The HTML to be embedded in the user's form.
 */
function recaptcha_get_html($pubkey, $error = null, $use_ssl = false)
{
    if ($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>");
    }

    $server = RECAPTCHA_API_SERVER;
    if ($use_ssl) {
        $server = RECAPTCHA_API_SECURE_SERVER;
    }

    $errorpart = '';
    if ($error) {
        $errorpart = '&amp;error=' . $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>';
}

/**
 * A ReCaptchaResponse is returned from recaptcha_check_answer()
 */
class ReCaptchaResponse
{
    public $is_valid;
    public $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
 * @param array  $extra_params an array of extra variables to post to the server
 * @return ReCaptchaResponse
 */
function recaptcha_check_answer($privkey, $remoteip, $challenge, $response, $extra_params = array())
{
    if ($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 || ('' === $challenge)  || $response == null || ('' === $response)) {
        $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) + $extra_params);

    $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 $appname The name of your application
 *
 * @return string
 */
function recaptcha_get_signup_url($domain = null, $appname = null)
{
    return 'https://www.google.com/recaptcha/admin/create?' . _recaptcha_qsencode(array('domains' => $domain, 'app' => $appname));
}

/**
 * @param $val
 *
 * @return string
 */
function _recaptcha_aes_pad($val)
{
    $block_size = 16;
    $numpad     = $block_size - (strlen($val) % $block_size);

    return str_pad($val, strlen($val) + $numpad, chr($numpad));
}

/* Mailhide related code */

/**
 * @param $val
 * @param $ky
 *
 * @return string
 */
function _recaptcha_aes_encrypt($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");
}

/**
 * @param $x
 *
 * @return string
 */
function _recaptcha_mailhide_urlbase64($x)
{
    return strtr(base64_encode($x), '+/', '-_');
}

/* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
/**
 * @param $pubkey
 * @param $privkey
 * @param $email
 *
 * @return string
 */
function recaptcha_mailhide_url($pubkey, $privkey, $email)
{
    if ($pubkey == '' || $pubkey == null || $privkey == '' || $privkey == null) {
        exit('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
 * @param $email
 * @return array
 */
function _recaptcha_mailhide_email_parts($email)
{
    $arr = preg_split('/@/', $email);

    if (strlen($arr[0]) <= 4) {
        $arr[0] = substr($arr[0], 0, 1);
    } elseif (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
 * @param $pubkey
 * @param $privkey
 * @param $email
 * @return string
 */
function recaptcha_mailhide_html($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]);
}
