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
 101 /**
 102  * Gets the challenge HTML (javascript and non-javascript version).
 103  * This is called from the browser, and the resulting reCAPTCHA HTML widget
 104  * is embedded within the HTML form it was called from.
 105  *
 106  * @global object
 107  * @param string $pubkey A public key for reCAPTCHA
 108  * @param string $error The error given by reCAPTCHA (optional, default is null)
 109  * @param boolean $use_ssl Should the request be made over ssl? (optional, default is false)
 110
 111  * @return string - The HTML to be embedded in the user's form.
 112  */
 113 function recaptcha_get_html ($pubkey, $error = null, $use_ssl = false) {
 114     global $CFG, $PAGE;
 115
 116     $recaptchatype = optional_param('recaptcha', 'image', PARAM_TEXT);
 117
 118     if ($pubkey == null || $pubkey == '') {
 119                 die ("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");
 120     }
 121
 122     if ($use_ssl) {
 123         $server = RECAPTCHA_API_SECURE_SERVER;
 124     } else {
 125         $server = RECAPTCHA_API_SERVER;
 126     }
 127
 128     $errorpart = "";
 129     if ($error) {
 130        $errorpart = "&amp;error=" . $error;
 131     }
 132
 133     require_once $CFG->libdir . '/filelib.php';
 134     $html = download_file_content($server . '/noscript?k=' . $pubkey . $errorpart, null, null, false, 300, 20, true);
 135     preg_match('/image\?c\=([A-Za-z0-9\-\_]*)\"/', $html, $matches);
 136     $challenge_hash = $matches[1];
 137     $image_url = $server . '/image?c=' . $challenge_hash;
 138
 139     $strincorrectpleasetryagain = get_string('incorrectpleasetryagain', 'auth');
 140     $strenterthewordsabove = get_string('enterthewordsabove', 'auth');
 141     $strenterthenumbersyouhear = get_string('enterthenumbersyouhear', 'auth');
 142     $strgetanothercaptcha = get_string('getanothercaptcha', 'auth');
 143     $strgetanaudiocaptcha = get_string('getanaudiocaptcha', 'auth');
 144     $strgetanimagecaptcha = get_string('getanimagecaptcha', 'auth');
 145
 146     $return = html_writer::script('', $server . '/challenge?k=' . $pubkey . $errorpart);
 147     $return .= '<noscript>
 148         <div id="recaptcha_widget_noscript">
 149         <div id="recaptcha_image_noscript"><img src="' . $image_url . '" alt="reCAPTCHA"/></div>';
 150
 151     if ($error == 'incorrect-captcha-sol') {
 152         $return .= '<div class="recaptcha_only_if_incorrect_sol" style="color:red">' . $strincorrectpleasetryagain . '</div>';
 153     }
 154
 155     if ($recaptchatype == 'image') {
 156         $return .= '<span class="recaptcha_only_if_image">' . $strenterthewordsabove . '</span>';
 157     } elseif ($recaptchatype == 'audio') {
 158         $return .= '<span class="recaptcha_only_if_audio">' . $strenterthenumbersyouhear . '</span>';
 159     }
 160
 161     $return .= '<input type="text" id="recaptcha_response_field_noscript" name="recaptcha_response_field" />';
 162     $return .= '<input type="hidden" id="recaptcha_challenge_field_noscript" name="recaptcha_challenge_field" value="' . $challenge_hash . '" />';
 163     $return .= '<div><a href="signup.php">' . $strgetanothercaptcha . '</a></div>';
 164
 165     // Disabling audio recaptchas for now: not language-independent
 166     /*
 167     if ($recaptchatype == 'image') {
 168         $return .= '<div class="recaptcha_only_if_image"><a href="signup.php?recaptcha=audio">' . $strgetanaudiocaptcha . '</a></div>';
 169     } elseif ($recaptchatype == 'audio') {
 170         $return .= '<div class="recaptcha_only_if_audio"><a href="signup.php?recaptcha=image">' . $strgetanimagecaptcha . '</a></div>';
 171     }
 172     */
 173
 174     $return .= '
 175         </div>
 176     </noscript>';
 177
 178     return $return;
 179 }
 180
 181
 182
 183
 184 /**
 185  * A ReCaptchaResponse is returned from recaptcha_check_answer()
 186  *
 187  * @package moodlecore
 188  * @copyright (c) 2007 reCAPTCHA -- {@link http://www.google.com/recaptcha}
 189  */
 190 class ReCaptchaResponse {
 191         var $is_valid;
 192         var $error;
 193 }
 194
 195
 196 /**
 197   * Calls an HTTP POST function to verify if the user's guess was correct
 198   * @param string $privkey
 199   * @param string $remoteip
 200   * @param string $challenge
 201   * @param string $response
 202   * @return ReCaptchaResponse
 203   */
 204 function recaptcha_check_answer ($privkey, $remoteip, $challenge, $response, $https=false)
 205 {
 206     if ($privkey == null || $privkey == '') {
 207                 die ("To use reCAPTCHA you must get an API key from <a href='https://www.google.com/recaptcha/admin/create'>https://www.google.com/recaptcha/admin/create</a>");
 208     }
 209
 210     if ($remoteip == null || $remoteip == '') {
 211         die ("For security reasons, you must pass the remote ip to reCAPTCHA");
 212     }
 213
 214         //discard spam submissions
 215         if ($challenge == null || strlen($challenge) == 0 || $response == null || strlen($response) == 0) {
 216                 $recaptcha_response = new ReCaptchaResponse();
 217                 $recaptcha_response->is_valid = false;
 218                 $recaptcha_response->error = 'incorrect-captcha-sol';
 219                 return $recaptcha_response;
 220         }
 221
 222         $response = _recaptcha_http_post(RECAPTCHA_VERIFY_SERVER, "/recaptcha/api/verify",
 223                                          array (
 224                                                 'privatekey' => $privkey,
 225                                                 'remoteip' => $remoteip,
 226                                                 'challenge' => $challenge,
 227                                                 'response' => $response
 228                                                 ),
 229                                          $https
 230                                         );
 231
 232         $answers = explode ("\n", $response [1]);
 233         $recaptcha_response = new ReCaptchaResponse();
 234
 235         if (trim ($answers [0]) == 'true') {
 236                 $recaptcha_response->is_valid = true;
 237         }
 238         else {
 239                 $recaptcha_response->is_valid = false;
 240                 $recaptcha_response->error = $answers [1];
 241         }
 242         return $recaptcha_response;
 243
 244 }
 245
 246 /**
 247  * gets a URL where the user can sign up for reCAPTCHA. If your application
 248  * has a configuration page where you enter a key, you should provide a link
 249  * using this function.
 250  * @param string $domain The domain where the page is hosted
 251  * @param string $appname The name of your application
 252  */
 253 function recaptcha_get_signup_url ($domain = null, $appname = null) {
 254         return "https://www.google.com/recaptcha/admin/create?" .  _recaptcha_qsencode (array ('domains' => $domain, 'app' => $appname));
 255 }
 256
 257 function _recaptcha_aes_pad($val) {
 258     $block_size = 16;
 259     $numpad = $block_size - (strlen ($val) % $block_size);
 260     return str_pad($val, strlen ($val) + $numpad, chr($numpad));
 261 }
 262
 263 /* Mailhide related code */
 264
 265 function _recaptcha_aes_encrypt($val,$ky) {
 266     if (! function_exists ("mcrypt_encrypt")) {
 267         die ("To use reCAPTCHA Mailhide, you need to have the mcrypt php module installed.");
 268     }
 269     $mode=MCRYPT_MODE_CBC;
 270     $enc=MCRYPT_RIJNDAEL_128;
 271     $val=_recaptcha_aes_pad($val);
 272     return mcrypt_encrypt($enc, $ky, $val, $mode, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
 273 }
 274
 275
 276 function _recaptcha_mailhide_urlbase64 ($x) {
 277     return strtr(base64_encode ($x), '+/', '-_');
 278 }
 279
 280 /* gets the reCAPTCHA Mailhide url for a given email, public key and private key */
 281 function recaptcha_mailhide_url($pubkey, $privkey, $email) {
 282     if ($pubkey == '' || $pubkey == null || $privkey == "" || $privkey == null) {
 283         die ("To use reCAPTCHA Mailhide, you have to sign up for a public and private key, " .
 284                      "you can do so at <a href='http://www.google.com/recaptcha/mailhide/apikey'>http://www.google.com/recaptcha/mailhide/apikey</a>");
 285     }
 286
 287
 288     $ky = pack('H*', $privkey);
 289     $cryptmail = _recaptcha_aes_encrypt ($email, $ky);
 290
 291         return "http://www.google.com/recaptcha/mailhide/d?k=" . $pubkey . "&c=" . _recaptcha_mailhide_urlbase64 ($cryptmail);
 292 }
 293
 294 /**
 295  * gets the parts of the email to expose to the user.
 296  * eg, given johndoe@example,com return ["john", "example.com"].
 297  * the email is then displayed as john...@example.com
 298  */
 299 function _recaptcha_mailhide_email_parts ($email) {
 300     $arr = preg_split("/@/", $email );
 301
 302     if (strlen ($arr[0]) <= 4) {
 303         $arr[0] = substr ($arr[0], 0, 1);
 304     } else if (strlen ($arr[0]) <= 6) {
 305         $arr[0] = substr ($arr[0], 0, 3);
 306     } else {
 307         $arr[0] = substr ($arr[0], 0, 4);
 308     }
 309     return $arr;
 310 }
 311
 312 /**
 313  * Gets html to display an email address given a public an private key.
 314  * to get a key, go to:
 315  *
 316  * http://www.google.com/recaptcha/mailhide/apikey
 317  */
 318 function recaptcha_mailhide_html($pubkey, $privkey, $email) {
 319     $emailparts = _recaptcha_mailhide_email_parts ($email);
 320     $url = recaptcha_mailhide_url ($pubkey, $privkey, $email);
 321
 322     return htmlentities($emailparts[0]) . "<a href='" . htmlentities ($url) .
 323         "' onclick=\"window.open('" . htmlentities ($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]);
 324
 325 }