lib/recaptchalib.php

   1 <?php
   2
   3 /**
   4  * This is a PHP library that handles calling reCAPTCHA.
   5  *    - Documentation and latest version
   6  *          {@link http://code.google.com/apis/recaptcha/docs/php.html}
   7  *    - Get a reCAPTCHA API Key
   8  *          {@link https://www.google.com/recaptcha/admin/create}
   9  *    - Discussion group
  10  *          {@link http://groups.google.com/group/recaptcha}
  11  *
  12  * Copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}
  13  * AUTHORS:
  14  *   Mike Crawford
  15  *   Ben Maurer
  16  *
  17  * Permission is hereby granted, free of charge, to any person obtaining a copy
  18  * of this software and associated documentation files (the "Software"), to deal
  19  * in the Software without restriction, including without limitation the rights
  20  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  21  * copies of the Software, and to permit persons to whom the Software is
  22  * furnished to do so, subject to the following conditions:
  23  *
  24  * The above copyright notice and this permission notice shall be included in
  25  * all copies or substantial portions of the Software.
  26  *
  27  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  28  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  29  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  30  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  31  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  32  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  33  * THE SOFTWARE.
  34  *
  35  * @package moodlecore
  36  * @copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}
  37  */
  38
  39 /**
  40  * The reCAPTCHA server URL's
  41  */
  42 define("RECAPTCHA_API_SERVER", "http://www.google.com/recaptcha/api");
  43 define("RECAPTCHA_API_SECURE_SERVER", "https://www.google.com/recaptcha/api");
  44 define("RECAPTCHA_VERIFY_SERVER", "www.google.com");
  45
  46 /**
  47  * Encodes the given data into a query string format
  48  * @param $data - array of string elements to be encoded
  49  * @return string - encoded request
  50  */
  51 function _recaptcha_qsencode ($data) {
  52         $req = "";
  53         foreach ( $data as $key => $value )
  54                 $req .= $key . '=' . urlencode( $value ) . '&';
  55
  56         // Cut the last '&'
  57         $req=substr($req,0,strlen($req)-1);
  58         return $req;
  59 }
  60
  61
  62
  63 /**
  64  * Submits an HTTP POST to a reCAPTCHA server
  65  *
  66  * @global object
  67  * @param string $host
  68  * @param string $path
  69  * @param array $data
  70  * @param int port
  71  * @return array response
  72  */
  73 function _recaptcha_http_post($host, $path, $data, $port = 80, $https=false) {
  74         global $CFG;
  75         $protocol = 'http';
  76         if ($https) {
  77             $protocol = 'https';
  78         }
  79
  80         require_once $CFG->libdir . '/filelib.php';
  81
  82         $req = _recaptcha_qsencode ($data);
  83
  84         $headers = array();
  85         $headers['Host'] = $host;
  86         $headers['Content-Type'] = 'application/x-www-form-urlencoded';
  87         $headers['Content-Length'] = strlen($req);
  88         $headers['User-Agent'] = 'reCAPTCHA/PHP';
  89
  90         $results = download_file_content("$protocol://" . $host . $path, $headers, $data, false, 300, 20, true);
  91
  92         if ($results) {
  93             return array(1 => $results);
  94         } else {
  95             return false;
  96         }
  97 }
  98
  99 /**
 100  * Return the recaptcha challenge and image and javascript urls
 101  *
 102  * @param  string $server    server url
 103  * @param  string $pubkey    public key
 104  * @param  string $errorpart error part to append
 105  * @return array the challenge hash, image and javascript url
 106  * @since  Moodle 3.2
 107  */
 108 function recaptcha_get_challenge_hash_and_urls($server, $pubkey, $errorpart = '') {
 109     global $CFG;
 110
 111     require_once($CFG->libdir . '/filelib.php');
 112     $html = download_file_content($server . '/noscript?k=' . $pubkey . $errorpart, null, null, false, 300, 20, true);
 113     preg_match('/image\?c\=([A-Za-z0-9\-\_]*)\"/', $html, $matches);
 114     $challengehash = $matches[1];
 115     $imageurl = $server . '/image?c=' . $challengehash;
 116
 117     $jsurl = $server . '/challenge?k=' . $pubkey . $errorpart;
 118
 119     return array($challengehash, $imageurl, $jsurl);
 120 }
 121
 122
 123 /**
 124  * Gets the challenge HTML (javascript and non-javascript version).
 125  * This is called from the browser, and the resulting reCAPTCHA HTML widget
 126  * is embedded within the HTML form it was called from.
 127  *
 128  * @global object
 129  * @param string $pubkey A public key for reCAPTCHA
 130  * @param string $error The error given by reCAPTCHA (optional, default is null)
 131  * @param boolean $use_ssl Should the request be made over ssl? (optional, default is false)
 132
 133  * @return string - The HTML to be embedded in the user's form.
 134  */
 135 function recaptcha_get_html ($pubkey, $error = null, $use_ssl = false) {
 136     global $PAGE;
 137
 138     $recaptchatype = optional_param('recaptcha', 'image', PARAM_TEXT);
 139
 140     if ($pubkey == null || $pubkey == '') {
 141                 die ("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");
 142     }
 143
 144     if ($use_ssl) {
 145         $server = RECAPTCHA_API_SECURE_SERVER;
 146     } else {
 147         $server = RECAPTCHA_API_SERVER;
 148     }
 149
 150     $errorpart = "";
 151     if ($error) {
 152         $errorpart = "&amp;error=" . $error;
 153     }
 154
 155     list($challengehash, $imageurl, $jsurl) = recaptcha_get_challenge_hash_and_urls($server, $pubkey, $errorpart);
 156
 157     $strincorrectpleasetryagain = get_string('incorrectpleasetryagain', 'auth');
 158     $strenterthewordsabove = get_string('enterthewordsabove', 'auth');
 159     $strenterthenumbersyouhear = get_string('enterthenumbersyouhear', 'auth');
 160     $strgetanothercaptcha = get_string('getanothercaptcha', 'auth');
 161     $strgetanaudiocaptcha = get_string('getanaudiocaptcha', 'auth');
 162     $strgetanimagecaptcha = get_string('getanimagecaptcha', 'auth');
 163
 164     $return = html_writer::script('', $jsurl);
 165     $return .= '<noscript>
 166         <div id="recaptcha_widget_noscript">
 167         <div id="recaptcha_image_noscript"><img src="' . $imageurl . '" alt="reCAPTCHA"/></div>';
 168
 169     if ($error == 'incorrect-captcha-sol') {
 170         $return .= '<div class="recaptcha_only_if_incorrect_sol" style="color:red">' . $strincorrectpleasetryagain . '</div>';
 171     }
 172
 173     if ($recaptchatype == 'image') {
 174         $return .= '<span class="recaptcha_only_if_image">' . $strenterthewordsabove . '</span>';
 175     } elseif ($recaptchatype == 'audio') {
 176         $return .= '<span class="recaptcha_only_if_audio">' . $strenterthenumbersyouhear . '</span>';
 177     }
 178
 179     $return .= '<input type="text" id="recaptcha_response_field_noscript" name="recaptcha_response_field" />';
 180     $return .= '<input type="hidden" id="recaptcha_challenge_field_noscript" name="recaptcha_challenge_field" value="' . $challengehash . '" />';
 181     $return .= '<div><a href="signup.php">' . $strgetanothercaptcha . '</a></div>';
 182
 183     // Disabling audio recaptchas for now: not language-independent
 184     /*
 185     if ($recaptchatype == 'image') {
 186         $return .= '<div class="recaptcha_only_if_image"><a href="signup.php?recaptcha=audio">' . $strgetanaudiocaptcha . '</a></div>';
 187     } elseif ($recaptchatype == 'audio') {
 188         $return .= '<div class="recaptcha_only_if_audio"><a href="signup.php?recaptcha=image">' . $strgetanimagecaptcha . '</a></div>';
 189     }
 190     */
 191
 192     $return .= '
 193         </div>
 194     </noscript>';
 195
 196     return $return;
 197 }
 198
 199
 200
 201
 202 /**
 203  * A ReCaptchaResponse is returned from recaptcha_check_answer()
 204  *
 205  * @package moodlecore
 206  * @copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}
 207  */
 208 class ReCaptchaResponse {
 209         var $is_valid;
 210         var $error;
 211 }
 212
 213
 214 /**
 215   * Calls an HTTP POST function to verify if the user's guess was correct
 216   * @param string $privkey
 217   * @param string $remoteip
 218   * @param string $challenge
 219   * @param string $response
 220   * @return ReCaptchaResponse
 221   */
 222 function recaptcha_check_answer ($privkey, $remoteip, $challenge, $response, $https=false)
 223 {
 224     if ($privkey == null || $privkey == '') {
 225                 die ("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");
 226     }
 227
 228     if ($remoteip == null || $remoteip == '') {
 229         die ("For security reasons, you must pass the remote ip to reCAPTCHA");
 230     }
 231
 232         //discard spam submissions
 233         if ($challenge == null || strlen($challenge) == 0 || $response == null || strlen($response) == 0) {
 234                 $recaptcha_response = new ReCaptchaResponse();
 235                 $recaptcha_response->is_valid = false;
 236                 $recaptcha_response->error = 'incorrect-captcha-sol';
 237                 return $recaptcha_response;
 238         }
 239
 240         $response = _recaptcha_http_post(RECAPTCHA_VERIFY_SERVER, "/recaptcha/api/verify",
 241                                          array (
 242                                                 'privatekey' => $privkey,
 243                                                 'remoteip' => $remoteip,
 244                                                 'challenge' => $challenge,
 245                                                 'response' => $response
 246                                                 ),
 247                                          $https
 248                                         );
 249
 250         $answers = explode ("\n", $response [1]);
 251         $recaptcha_response = new ReCaptchaResponse();
 252
 253         if (trim ($answers [0]) == 'true') {
 254                 $recaptcha_response->is_valid = true;
 255         }
 256         else {
 257                 $recaptcha_response->is_valid = false;
 258                 $recaptcha_response->error = $answers [1];
 259         }
 260         return $recaptcha_response;
 261
 262 }
 263
 264 /**
 265  * gets a URL where the user can sign up for reCAPTCHA. If your application
 266  * has a configuration page where you enter a key, you should provide a link
 267  * using this function.
 268  * @param string $domain The domain where the page is hosted
 269  * @param string $appname The name of your application
 270  */
 271 function recaptcha_get_signup_url ($domain = null, $appname = null) {
 272         return "https://www.google.com/recaptcha/admin/create?" .  _recaptcha_qsencode (array ('domains' => $domain, 'app' => $appname));
 273 }
 274
 275 function _recaptcha_aes_pad($val) {
 276     $block_size = 16;
 277     $numpad = $block_size - (strlen ($val) % $block_size);
 278     return str_pad($val, strlen ($val) + $numpad, chr($numpad));
 279 }
 280
 281 /* Mailhide related code */
 282
 283 function _recaptcha_aes_encrypt($val,$ky) {
 284     if (! function_exists ("mcrypt_encrypt")) {
 285         die ("To use reCAPTCHA Mailhide, you need to have the mcrypt php module installed.");
 286     }
 287     $mode=MCRYPT_MODE_CBC;
 288     $enc=MCRYPT_RIJNDAEL_128;
 289     $val=_recaptcha_aes_pad($val);
 290     return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
 291 }
 292
 293
 294 function _recaptcha_mailhide_urlbase64 ($x) {
 295     return strtr(base64_encode ($x), '+/', '-_');
 296 }
 297
 298 /* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
 299 function recaptcha_mailhide_url($pubkey, $privkey, $email) {
 300     if ($pubkey == '' || $pubkey == null || $privkey == "" || $privkey == null) {
 301         die ("To use reCAPTCHA Mailhide, you have to sign up for a public and private key, " .
 302                      "you can do so at <a href='http://www.google.com/recaptcha/mailhide/apikey'>http://www.google.com/recaptcha/mailhide/apikey</a>");
 303     }
 304
 305
 306     $ky = pack('H*', $privkey);
 307     $cryptmail = _recaptcha_aes_encrypt ($email, $ky);
 308
 309         return "http://www.google.com/recaptcha/mailhide/d?k=" . $pubkey . "&c=" . _recaptcha_mailhide_urlbase64 ($cryptmail);
 310 }
 311
 312 /**
 313  * gets the parts of the email to expose to the user.
 314  * eg, given johndoe@example,com return ["john", "example.com"].
 315  * the email is then displayed as john...@example.com
 316  */
 317 function _recaptcha_mailhide_email_parts ($email) {
 318     $arr = preg_split("/@/", $email );
 319
 320     if (strlen ($arr[0]) <= 4) {
 321         $arr[0] = substr ($arr[0], 0, 1);
 322     } else if (strlen ($arr[0]) <= 6) {
 323         $arr[0] = substr ($arr[0], 0, 3);
 324     } else {
 325         $arr[0] = substr ($arr[0], 0, 4);
 326     }
 327     return $arr;
 328 }
 329
 330 /**
 331  * Gets html to display an email address given a public an private key.
 332  * to get a key, go to:
 333  *
 334  * http://www.google.com/recaptcha/mailhide/apikey
 335  */
 336 function recaptcha_mailhide_html($pubkey, $privkey, $email) {
 337     $emailparts = _recaptcha_mailhide_email_parts ($email);
 338     $url = recaptcha_mailhide_url ($pubkey, $privkey, $email);
 339
 340     return htmlentities($emailparts[0]) . "<a href='" . htmlentities ($url) .
 341         "' onclick=\"window.open('" . htmlentities ($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]);
 342
 343 }