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root / drupal7 / sites / all / modules / captcha / captcha.module @ 76df55b7

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<?php
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/**
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 * @file
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 * This module enables basic CAPTCHA functionality:
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 * administrators can add a CAPTCHA to desired forms that users without
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 * the 'skip CAPTCHA' permission (typically anonymous visitors) have
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 * to solve.
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 */
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/**
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 * Constants for CAPTCHA persistence.
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 * TODO: change these integers to strings because the CAPTCHA settings form saves them as strings in the variables table anyway?
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 */
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// Always add a CAPTCHA (even on every page of a multipage workflow).
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define('CAPTCHA_PERSISTENCE_SHOW_ALWAYS', 0);
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// Only one CAPTCHA has to be solved per form instance/multi-step workflow.
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define('CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_INSTANCE', 1);
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// Once the user answered correctly for a CAPTCHA on a certain form type,
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// no more CAPTCHAs will be offered anymore for that form.
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define('CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_TYPE', 2);
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// Once the user answered correctly for a CAPTCHA on the site,
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// no more CAPTCHAs will be offered anymore.
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define('CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL', 3);
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define('CAPTCHA_STATUS_UNSOLVED', 0);
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define('CAPTCHA_STATUS_SOLVED', 1);
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define('CAPTCHA_STATUS_EXAMPLE', 2);
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define('CAPTCHA_DEFAULT_VALIDATION_CASE_SENSITIVE', 0);
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define('CAPTCHA_DEFAULT_VALIDATION_CASE_INSENSITIVE', 1);
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/**
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 * Implementation of hook_help().
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 */
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function captcha_help($path, $arg) {
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  switch ($path) {
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    case 'admin/help#captcha':
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      $output = '<p>' . t('"CAPTCHA" is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart". It is typically a challenge-response test to determine whether the user is human. The CAPTCHA module is a tool to fight automated submission by malicious users (spamming) of for example comments forms, user registration forms, guestbook forms, etc. You can extend the desired forms with an additional challenge, which should be easy for a human to solve correctly, but hard enough to keep automated scripts and spam bots out.') . '</p>';
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      $output .= '<p>' . t('Note that the CAPTCHA module interacts with page caching (see <a href="!performancesettings">performance settings</a>). Because the challenge should be unique for each generated form, the caching of the page it appears on is prevented. Make sure that these forms do not appear on too many pages or you will lose much caching efficiency. For example, if you put a CAPTCHA on the user login block, which typically appears on each page for anonymous visitors, caching will practically be disabled. The comment submission forms are another example. In this case you should set the <em>Location of comment submission form</em> to <em>Display on separate page</em> in the comment settings of the relevant <a href="!contenttypes">content types</a> for better caching efficiency.',
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        array(
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          '!performancesettings' => url('admin/config/development/performance'),
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          '!contenttypes' => url('admin/structure/types'),
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        )
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      ) . '</p>';
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      $output .= '<p>' . t('CAPTCHA is a trademark of Carnegie Mellon University.') . '</p>';
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      return $output;
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    case 'admin/config/people/captcha':
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    case 'admin/config/people/captcha/captcha':
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    case 'admin/config/people/captcha/captcha/settings':
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      $output = '<p>' . t('A CAPTCHA can be added to virtually each Drupal form. Some default forms are already provided in the form list, but arbitrary forms can be easily added and managed when the option <em>Add CAPTCHA administration links to forms</em> is enabled.') . '</p>';
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      $output .= '<p>' . t('Users with the <em>Skip CAPTCHA</em> <a href="@perm">permission</a> won\'t be offered a challenge. Be sure to grant this permission to the trusted users (e.g. site administrators). If you want to test a protected form, be sure to do it as a user without the <em>Skip CAPTCHA</em> permission (e.g. as anonymous user).', array('@perm' => url('admin/people/permissions'))) . '</p>';
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      return $output;
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  }
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}
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/**
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 * Implements of hook_menu().
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 */
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function captcha_menu() {
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  $items = array();
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  // Main configuration page of the basic CAPTCHA module.
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  $items['admin/config/people/captcha'] = array(
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    'title' => 'CAPTCHA',
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    'description' => 'Administer how and where CAPTCHAs are used.',
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    'file' => 'captcha.admin.inc',
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    'page callback' => 'drupal_get_form',
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    'page arguments' => array('captcha_admin_settings'),
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    'access arguments' => array('administer CAPTCHA settings'),
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    'type' => MENU_NORMAL_ITEM,
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  );
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  // The default local task (needed when other modules want to offer,
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  // alternative CAPTCHA types and their own configuration page as local task).
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  $items['admin/config/people/captcha/captcha'] = array(
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    'title' => 'CAPTCHA',
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    'access arguments' => array('administer CAPTCHA settings'),
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    'type' => MENU_DEFAULT_LOCAL_TASK,
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    'weight' => -20,
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  );
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  $items['admin/config/people/captcha/captcha/settings'] = array(
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    'title' => 'General settings',
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    'access arguments' => array('administer CAPTCHA settings'),
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    'type' => MENU_DEFAULT_LOCAL_TASK,
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    'weight' => 0,
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  );
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  $items['admin/config/people/captcha/captcha/examples'] = array(
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    'title' => 'Examples',
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    'description' => 'An overview of the available challenge types with examples.',
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    'file' => 'captcha.admin.inc',
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    'page callback' => 'drupal_get_form',
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    'page arguments' => array('captcha_examples', 6, 7),
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    'access arguments' => array('administer CAPTCHA settings'),
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    'type' => MENU_LOCAL_TASK,
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    'weight' => 5,
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  );
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  $items['admin/config/people/captcha/captcha/captcha_point'] = array(
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    'title' => 'CAPTCHA point administration',
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    'file' => 'captcha.admin.inc',
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    'page callback' => 'captcha_point_admin',
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    'page arguments' => array(6, 7),
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    'access arguments' => array('administer CAPTCHA settings'),
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    'type' => MENU_CALLBACK,
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  );
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  return $items;
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}
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/**
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 * Implements of hook_permission().
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 */
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function captcha_permission() {
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  return array(
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    'administer CAPTCHA settings' => array(
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      'title' => t('Administer CAPTCHA settings'),
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    ),
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    'skip CAPTCHA' => array(
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      'title' => t('Skip CAPTCHA'),
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      'description' => t('Users with this permission will not be offered a CAPTCHA.'),
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    ),
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  );
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}
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/**
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 * Implements of hook_theme().
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 */
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function captcha_theme() {
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  return array(
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    'captcha_admin_settings_captcha_points' => array(
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      'render element' => 'form',
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    ),
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    'captcha' => array(
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      'render element' => 'element',
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    ),
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  );
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}
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/**
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 * Implements of hook_cron().
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 *
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 * Remove old entries from captcha_sessions table.
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 */
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function captcha_cron() {
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  // Remove challenges older than 1 day.
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  db_delete('captcha_sessions')
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    ->condition('timestamp', REQUEST_TIME - 60 * 60 * 24, '<')
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    ->execute();
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}
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/**
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 * Implements of hook_element_info().
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 */
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function captcha_element_info() {
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  // Define the CAPTCHA form element with default properties.
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  $captcha_element = array(
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    '#input' => TRUE,
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    '#process' => array('captcha_element_process'),
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    // The type of challenge: e.g. 'default', 'none', 'captcha/Math', 'image_captcha/Image'.
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    '#captcha_type' => 'default',
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    '#default_value' => '',
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    // CAPTCHA in admin mode: presolve the CAPTCHA and always show it (despite previous successful responses).
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    '#captcha_admin_mode' => FALSE,
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    // The default CAPTCHA validation function.
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    // TODO: should this be a single string or an array of strings (combined in OR fashion)?
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    '#captcha_validate' => 'captcha_validate_strict_equality',
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  );
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  // Override the default CAPTCHA validation function for case insensitive validation.
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  // TODO: shouldn't this be done somewhere else, e.g. in form_alter?
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  if (CAPTCHA_DEFAULT_VALIDATION_CASE_INSENSITIVE == variable_get('captcha_default_validation', CAPTCHA_DEFAULT_VALIDATION_CASE_INSENSITIVE)) {
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    $captcha_element['#captcha_validate'] = 'captcha_validate_case_insensitive_equality';
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  }
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  return array('captcha' => $captcha_element);
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}
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/**
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 * Process callback for CAPTCHA form element.
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 */
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function captcha_element_process($element, &$form_state, $complete_form) {
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  module_load_include('inc', 'captcha');
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  // Add Javascript for general CAPTCHA functionality.
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  drupal_add_js(drupal_get_path('module', 'captcha') . '/captcha.js');
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  // Prevent caching of the page with CAPTCHA elements.
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  // This needs to be done even if the CAPTCHA will be ommitted later:
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  // other untrusted users should not get a cached page when
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  // the current untrusted user can skip the current CAPTCHA.
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  global $conf;
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  $conf['cache'] = FALSE;
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  // Get the form ID of the form we are currently processing (which is not
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  // necessary the same form that is submitted (if any).
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  $this_form_id = $complete_form['form_id']['#value'];
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  // Get the CAPTCHA session ID.
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  // If there is a submitted form: try to retrieve and reuse the
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  // CAPTCHA session ID from the posted data.
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  list($posted_form_id, $posted_captcha_sid) = _captcha_get_posted_captcha_info($element, $form_state, $this_form_id);
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  if ($this_form_id == $posted_form_id && isset($posted_captcha_sid)) {
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    $captcha_sid = $posted_captcha_sid;
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  }
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  else {
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    // Generate a new CAPTCHA session if we could not reuse one from a posted form.
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    $captcha_sid = _captcha_generate_captcha_session($this_form_id, CAPTCHA_STATUS_UNSOLVED);
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  }
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  // Store CAPTCHA session ID as hidden field.
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  // Strictly speaking, it is not necessary to send the CAPTCHA session id
210
  // with the form, as the one time CAPTCHA token (see lower) is enough.
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  // However, we still send it along, because it can help debugging
212
  // problems on live sites with only access to the markup.
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  $element['captcha_sid'] = array(
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    '#type' => 'hidden',
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    '#value' => $captcha_sid,
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  );
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  $captcha_token = db_select('captcha_sessions', 'c')
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    ->fields('c', array('token'))
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    ->condition('csid', $captcha_sid)
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    ->execute()
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    ->fetchField();
223
  if (!isset($captcha_token) && !$form_state['submitted']) {
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    // Additional one-time CAPTCHA token: store in database and send with form.
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    $captcha_token = md5(mt_rand());
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    db_update('captcha_sessions')
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      ->fields(array('token' => $captcha_token))
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      ->condition('csid', $captcha_sid)
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      ->execute();
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  }
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  $element['captcha_token'] = array(
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    '#type' => 'hidden',
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    '#value' => $captcha_token,
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  );
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  // Get implementing module and challenge for CAPTCHA.
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  list($captcha_type_module, $captcha_type_challenge) = _captcha_parse_captcha_type($element['#captcha_type']);
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  // Store CAPTCHA information for further processing in
241
  // - $form_state['captcha_info'], which survives a form rebuild (e.g. node
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  //   preview), useful in _captcha_get_posted_captcha_info().
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  // - $element['#captcha_info'], for post processing functions that do not
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  //   receive a $form_state argument (e.g. the pre_render callback).
245
  $form_state['captcha_info'] = array(
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    'this_form_id' => $this_form_id,
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    'posted_form_id' => $posted_form_id,
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    'captcha_sid' => $captcha_sid,
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    'module' => $captcha_type_module,
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    'captcha_type' => $captcha_type_challenge,
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  );
252
  $element['#captcha_info'] = array(
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    'form_id' => $this_form_id,
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    'captcha_sid' => $captcha_sid,
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  );
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257
  if (_captcha_required_for_user($captcha_sid, $this_form_id) || $element['#captcha_admin_mode']) {
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    // Generate a CAPTCHA and its solution
259
    // (note that the CAPTCHA session ID is given as third argument).
260
    $captcha = module_invoke($captcha_type_module, 'captcha', 'generate', $captcha_type_challenge, $captcha_sid);
261
    if (!isset($captcha['form']) || !isset($captcha['solution'])) {
262
      // The selected module did not return what we expected: log about it and quit.
263
      watchdog('CAPTCHA',
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        'CAPTCHA problem: unexpected result from hook_captcha() of module %module when trying to retrieve challenge type %type for form %form_id.',
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        array(
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          '%type' => $captcha_type_challenge,
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          '%module' => $captcha_type_module,
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          '%form_id' => $this_form_id,
269
        ),
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        WATCHDOG_ERROR);
271
      return $element;
272
    }
273
    // Add form elements from challenge as children to CAPTCHA form element.
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    $element['captcha_widgets'] = $captcha['form'];
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276
    // Add a validation callback for the CAPTCHA form element (when not in admin mode).
277
    if (!$element['#captcha_admin_mode']) {
278
      $element['#element_validate'] = array('captcha_validate');
279
    }
280
281
    // Set a custom CAPTCHA validate function if requested.
282
    if (isset($captcha['captcha_validate'])) {
283
      $element['#captcha_validate'] = $captcha['captcha_validate'];
284
    }
285
286
    // Set the theme function.
287
    $element['#theme'] = 'captcha';
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    // Add pre_render callback for additional CAPTCHA processing.
290
    if (!isset($element['#pre_render'])) {
291
      $element['#pre_render'] = array();
292
    }
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    $element['#pre_render'][] = 'captcha_pre_render_process';
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    // Store the solution in the #captcha_info array.
296
    $element['#captcha_info']['solution'] = $captcha['solution'];
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    // Make sure we can use a top level form value $form_state['values']['captcha_response'], even if the form has #tree=true.
299
    $element['#tree'] = FALSE;
300
301
  }
302
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  return $element;
304
}
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/**
307
 * Implementation of hook_captcha_default_points_alter().
308
 *
309
 * Provide some default captchas only if defaults are not already
310
 * provided by other modules.
311
 */
312
function captcha_captcha_default_points_alter(&$items) {
313
  $modules = array(
314
    'comment' => array(
315
    ),
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    'contact' => array(
317
      'contact_site_form',
318
      'contact_personal_form'
319
    ),
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    'forum' => array(
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      'forum_node_form',
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    ),
323
    'user' => array(
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      'user_register_form',
325
      'user_pass',
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      'user_login',
327
      'user_login_block',
328
    ),
329
  );
330
  // Add comment form_ids of all currently known node types.
331
  foreach (node_type_get_names() as $type => $name) {
332
    $modules['comment'][] = 'comment_node_' . $type . '_form';
333
  }
334
335
  foreach ($modules as $module => $form_ids) {
336
    // Only give defaults if the module exists.
337
    if (module_exists($module)) {
338
      foreach ($form_ids as $form_id) {
339
        // Ensure a default has not been provided already.
340
        if (!isset($items[$form_id])) {
341
          $captcha = new stdClass;
342
          $captcha->disabled = FALSE;
343
          $captcha->api_version = 1;
344
          $captcha->form_id = $form_id;
345
          $captcha->module = '';
346
          $captcha->captcha_type = 'default';
347
          $items[$form_id] = $captcha;
348
        }
349
      }
350
    }
351
  }
352
}
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/**
355
 * Theme function for a CAPTCHA element.
356
 *
357
 * Render it in a fieldset if a description of the CAPTCHA
358
 * is available. Render it as is otherwise.
359
 */
360
function theme_captcha($variables) {
361
  $element = $variables['element'];
362
  if (!empty($element['#description']) && isset($element['captcha_widgets'])) {
363
    $fieldset = array(
364
      '#type' => 'fieldset',
365
      '#title' => t('CAPTCHA'),
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      '#description' => $element['#description'],
367
      '#children' => drupal_render_children($element),
368
      '#attributes' => array('class' => array('captcha')),
369
    );
370
    return theme('fieldset', array('element' => $fieldset));
371
  }
372
  else {
373
    return '<div class="captcha">' . drupal_render_children($element) . '</div>';
374
  }
375
}
376
377
/**
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 * Implements of hook_form_alter().
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 *
380
 * This function adds a CAPTCHA to forms for untrusted users if needed and adds
381
 * CAPTCHA administration links for site administrators if this option is enabled.
382
 */
383
function captcha_form_alter(&$form, &$form_state, $form_id) {
384
385
  if (!user_access('skip CAPTCHA')) {
386
    // Visitor does not have permission to skip CAPTCHAs.
387
    module_load_include('inc', 'captcha');
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    // Get CAPTCHA type and module for given form_id.
390
    $captcha_point = captcha_get_form_id_setting($form_id);
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    if ($captcha_point && !empty($captcha_point->captcha_type)) {
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      module_load_include('inc', 'captcha');
393
      // Build CAPTCHA form element.
394
      $captcha_element = array(
395
        '#type' => 'captcha',
396
        '#captcha_type' => $captcha_point->module . '/' . $captcha_point->captcha_type,
397
      );
398
      // Add a CAPTCHA description if required.
399
      if (variable_get('captcha_add_captcha_description', TRUE)) {
400
        $captcha_element['#description'] = _captcha_get_description();
401
      }
402
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      // Get placement in form and insert in form.
404
      $captcha_placement = _captcha_get_captcha_placement($form_id, $form);
405
      _captcha_insert_captcha_element($form, $captcha_placement, $captcha_element);
406
    }
407
  }
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  elseif (
409
    variable_get('captcha_administration_mode', FALSE)
410
    && user_access('administer CAPTCHA settings')
411
    && (arg(0) != 'admin' || variable_get('captcha_allow_on_admin_pages', FALSE))
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  ) {
413
    // Add CAPTCHA administration tools.
414
    module_load_include('inc', 'captcha');
415
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    $captcha_point = captcha_get_form_id_setting($form_id);
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    // For administrators: show CAPTCHA info and offer link to configure it.
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    $captcha_element = array(
419
      '#type' => 'fieldset',
420
      '#title' => t('CAPTCHA'),
421
      '#collapsible' => TRUE,
422
      '#collapsed' => TRUE,
423
      '#attributes' => array('class' => array('captcha-admin-links')),
424
    );
425
    if ($captcha_point !== NULL && $captcha_point->captcha_type) {
426
      $captcha_element['#title'] = t('CAPTCHA: challenge "@type" enabled', array('@type' => $captcha_point->captcha_type));
427
      $captcha_element['#description'] = t('Untrusted users will see a CAPTCHA here (<a href="@settings">general CAPTCHA settings</a>).',
428
        array('@settings' => url('admin/config/people/captcha'))
429
      );
430
      $captcha_element['challenge'] = array(
431
        '#type' => 'item',
432
        '#title' => t('Enabled challenge'),
433
        '#markup' => t('%type by module %module (<a href="@change">change</a>, <a href="@disable">disable</a>)', array(
434
          '%type' => $captcha_point->captcha_type,
435
          '%module' => $captcha_point->module,
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          '@change' => url("admin/config/people/captcha/captcha/captcha_point/$form_id", array('query' => drupal_get_destination())),
437
          '@disable' => url("admin/config/people/captcha/captcha/captcha_point/$form_id/disable", array('query' => drupal_get_destination())),
438
        )),
439
      );
440
      // Add an example challenge with solution.
441
      // This does not work with the reCAPTCHA and Egglue challenges as
442
      // discussed in http://drupal.org/node/487032 and
443
      // http://drupal.org/node/525586. As a temporary workaround, we
444
      // blacklist the reCAPTCHA and Egglue challenges and do not show
445
      // an example challenge.
446
      // TODO: Once the issues mentioned above are fixed, this workaround
447
      // should be removed.
448
      if ($captcha_point->module != 'recaptcha' && $captcha_point->module != 'egglue_captcha') {
449
        $captcha_element['example'] = array(
450
          '#type' => 'fieldset',
451
          '#title' => t('Example'),
452
          '#description' => t('This is a pre-solved, non-blocking example of this challenge.'),
453
        );
454
        $captcha_element['example']['example_captcha'] = array(
455
          '#type' => 'captcha',
456
          '#captcha_type' => $captcha_point->module . '/' . $captcha_point->captcha_type,
457
          '#captcha_admin_mode' => TRUE,
458
        );
459
      }
460
    }
461
    else {
462
      $captcha_element['#title'] = t('CAPTCHA: no challenge enabled');
463
      $captcha_element['add_captcha'] = array(
464
        '#markup' => l(t('Place a CAPTCHA here for untrusted users.'), "admin/config/people/captcha/captcha/captcha_point/$form_id", array('query' => drupal_get_destination()))
465
      );
466
467
    }
468
    // Get placement in form and insert in form.
469
    $captcha_placement = _captcha_get_captcha_placement($form_id, $form);
470
    _captcha_insert_captcha_element($form, $captcha_placement, $captcha_element);
471
472
  }
473
474
  // Add a warning about caching on the Perfomance settings page.
475
  if ($form_id == 'system_performance_settings') {
476 ac1bc5de Assos Assos
    $icon = theme(
477
      'image',
478
      array(
479
        'path' => 'misc/watchdog-warning.png',
480
        'width' => 18,
481
        'height' => 18,
482
        'alt' => t('warning'),
483
        'title' => t('warning'),
484
      )
485
    );
486 85ad3d82 Assos Assos
    $form['caching']['captcha'] = array(
487
      '#type' => 'item',
488
      '#title' => t('CAPTCHA'),
489 00c2605a Assos Assos
      '#markup' => t(
490
        '!icon The CAPTCHA module will disable the caching of pages that contain a CAPTCHA element.',
491
        array(
492
          '!icon' => '<span class="icon">' . $icon . '</span>'
493
        )
494 85ad3d82 Assos Assos
      ),
495
      '#attributes' => array('class' => array('warning')),
496
    );
497
  }
498
499
}
500
501
/**
502
 * CAPTCHA validation function to tests strict equality.
503 ac1bc5de Assos Assos
 *
504
 * @param string $solution
505
 *   the solution of the test.
506
 *
507
 * @param string $response
508
 *   the response to the test.
509
 *
510
 * @return bool
511
 *   TRUE when equal (ignoring spaces), FALSE otherwise.
512 85ad3d82 Assos Assos
 */
513
function captcha_validate_strict_equality($solution, $response) {
514
  return $solution === $response;
515
}
516
517
/**
518
 * CAPTCHA validation function to tests case insensitive equality.
519 ac1bc5de Assos Assos
 *
520
 * @param string $solution
521
 *   the solution of the test.
522
 *
523
 * @param string $response
524
 *   the response to the test.
525
 *
526
 * @return bool
527
 *   TRUE when equal (ignoring spaces), FALSE otherwise.
528 85ad3d82 Assos Assos
 */
529
function captcha_validate_case_insensitive_equality($solution, $response) {
530
  return drupal_strtolower($solution) === drupal_strtolower($response);
531
}
532
533
/**
534
 * CAPTCHA validation function to tests equality while ignoring spaces.
535 ac1bc5de Assos Assos
 *
536
 * @param string $solution
537
 *   the solution of the test.
538
 *
539
 * @param string $response
540
 *   the response to the test.
541
 *
542
 * @return bool
543
 *   TRUE when equal (ignoring spaces), FALSE otherwise.
544 85ad3d82 Assos Assos
 */
545
function captcha_validate_ignore_spaces($solution, $response) {
546
  return preg_replace('/\s/', '', $solution) === preg_replace('/\s/', '', $response);
547
}
548
549
/**
550
 * CAPTCHA validation function to tests case insensitive equality while ignoring spaces.
551 ac1bc5de Assos Assos
 *
552
 * @param string $solution
553
 *   the solution of the test.
554
 *
555
 * @param string $response
556
 *   the response to the test.
557
 *
558
 * @return bool
559
 *   TRUE when equal (ignoring spaces), FALSE otherwise.
560 85ad3d82 Assos Assos
 */
561
function captcha_validate_case_insensitive_ignore_spaces($solution, $response) {
562
  return preg_replace('/\s/', '', drupal_strtolower($solution)) === preg_replace('/\s/', '', drupal_strtolower($response));
563
}
564
565
/**
566 00c2605a Assos Assos
 * Helper function for getting the posted CAPTCHA info (posted form_id and
567
 * CAPTCHA sessions ID) from a form in case it is posted.
568 85ad3d82 Assos Assos
 *
569
 * This function hides the form processing mess for several use cases an
570
 * browser bug workarounds.
571
 * For example: $element['#post'] can typically be used to get the posted
572
 * form_id and captcha_sid, but in the case of node preview situations
573
 * (with correct CAPTCHA response) that does not work and we can get them from
574
 * $form_state['clicked_button']['#post'].
575
 * However with Internet Explorer 7, the latter does not work either when
576
 * submitting the forms (with only one text field) with the enter key
577
 * (see http://drupal.org/node/534168), in which case we also have to check
578
 * $form_state['buttons']['button']['0']['#post'].
579
 *
580
 * @todo for Drupal 7 version: is this IE7 workaround still needed?
581
 *
582 ac1bc5de Assos Assos
 * @param array $element
583
 *   the CAPTCHA element.
584
 *
585
 * @param array $form_state
586
 *   the form state structure to extract the info from.
587
 *
588
 * @param string $this_form_id
589
 *   the form ID of the form we are currently processing
590 85ad3d82 Assos Assos
 *     (which is not necessarily the form that was posted).
591
 *
592 ac1bc5de Assos Assos
 * @return array
593
 *   an array with $posted_form_id and $post_captcha_sid (with NULL values
594 85ad3d82 Assos Assos
 *     if the values could not be found, e.g. for a fresh form).
595
 */
596
function _captcha_get_posted_captcha_info($element, $form_state, $this_form_id) {
597
  if ($form_state['submitted'] && isset($form_state['captcha_info'])) {
598
    // We are handling (or rebuilding) an already submitted form,
599
    // so we already determined the posted form ID and CAPTCHA session ID
600
    // for this form (from before submitting). Reuse this info.
601
    $posted_form_id = $form_state['captcha_info']['posted_form_id'];
602
    $posted_captcha_sid = $form_state['captcha_info']['captcha_sid'];
603
  }
604
  else {
605
    // We have to determine the posted form ID and CAPTCHA session ID
606
    // from the post data.
607
    // Because we possibly use raw post data here,
608
    // we should be extra cautious and filter this data.
609 ac1bc5de Assos Assos
    $posted_form_id = isset($form_state['input']['form_id']) ? preg_replace("/[^a-z0-9_]/", "", (string) $form_state['input']['form_id']) : NULL;
610
    $posted_captcha_sid = isset($form_state['input']['captcha_sid']) ? (int) $form_state['input']['captcha_sid'] : NULL;
611 00c2605a Assos Assos
    $posted_captcha_token = !empty($form_state['input']['captcha_token']) ? preg_replace("/[^a-zA-Z0-9]/", "", (string) $form_state['input']['captcha_token']) : NULL;
612 85ad3d82 Assos Assos
613
    if ($posted_form_id == $this_form_id) {
614
      // Check if the posted CAPTCHA token is valid for the posted CAPTCHA
615
      // session ID. Note that we could just check the validity of the CAPTCHA
616
      // token and extract the CAPTCHA session ID from that (without looking at
617
      // the actual posted CAPTCHA session ID). However, here we check both
618
      // the posted CAPTCHA token and session ID: it is a bit more stringent
619
      // and the database query should also be more efficient (because there is
620
      // an index on the CAPTCHA session ID).
621
      if ($posted_captcha_sid != NULL) {
622
        $expected_captcha_token = db_query(
623
          "SELECT token FROM {captcha_sessions} WHERE csid = :csid",
624
          array(':csid' => $posted_captcha_sid)
625
        )->fetchField();
626 00c2605a Assos Assos
627 85ad3d82 Assos Assos
        if ($expected_captcha_token !== $posted_captcha_token) {
628
          drupal_set_message(t('CAPTCHA session reuse attack detected.'), 'error');
629
          // Invalidate the CAPTCHA session.
630
          $posted_captcha_sid = NULL;
631
        }
632 00c2605a Assos Assos
633 85ad3d82 Assos Assos
        // Invalidate CAPTCHA token to avoid reuse.
634
        db_update('captcha_sessions')
635
          ->fields(array('token' => NULL))
636 00c2605a Assos Assos
          ->condition('csid', $posted_captcha_sid)
637
          ->execute();
638 85ad3d82 Assos Assos
      }
639
    }
640
    else {
641
      // The CAPTCHA session ID is specific to the posted form.
642
      // Return NULL, so a new session will be generated for this other form.
643
      $posted_captcha_sid = NULL;
644
    }
645
  }
646
  return array($posted_form_id, $posted_captcha_sid);
647
}
648
649
/**
650
 * CAPTCHA validation handler.
651
 *
652
 * This function is placed in the main captcha.module file to make sure that
653
 * it is available (even for cached forms, which don't fire
654
 * captcha_form_alter(), and subsequently don't include additional include
655
 * files).
656
 */
657
function captcha_validate($element, &$form_state) {
658 00c2605a Assos Assos
  // If disable captcha mode is enabled, bypass captcha validation.
659
  if (variable_get('disable_captcha', FALSE)) {
660
    return;
661
  }
662 85ad3d82 Assos Assos
663
  $captcha_info = $form_state['captcha_info'];
664
  $form_id = $captcha_info['this_form_id'];
665
666
  // Get CAPTCHA response.
667
  $captcha_response = $form_state['values']['captcha_response'];
668
669
  // Get CAPTCHA session from CAPTCHA info
670
  // TODO: is this correct in all cases: see comment and code in previous revisions?
671
  $csid = $captcha_info['captcha_sid'];
672
673
  $solution = db_query(
674
    'SELECT solution FROM {captcha_sessions} WHERE csid = :csid',
675
    array(':csid' => $csid)
676
    )
677
    ->fetchField();
678
679
  // @todo: what is the result when there is no entry for the captcha_session? in D6 it was FALSE, what in D7?
680
  if ($solution === FALSE) {
681
    // Unknown challenge_id.
682
    // TODO: this probably never happens anymore now that there is detection
683
    // for CAPTCHA session reuse attacks in _captcha_get_posted_captcha_info().
684
    form_set_error('captcha', t('CAPTCHA validation error: unknown CAPTCHA session ID. Contact the site administrator if this problem persists.'));
685
    watchdog('CAPTCHA',
686
      'CAPTCHA validation error: unknown CAPTCHA session ID (%csid).',
687
      array('%csid' => var_export($csid, TRUE)),
688
      WATCHDOG_ERROR);
689
  }
690
  else {
691
    // Get CAPTCHA validate function or fall back on strict equality.
692
    $captcha_validate = $element['#captcha_validate'];
693
    if (!function_exists($captcha_validate)) {
694 ac1bc5de Assos Assos
      $captcha_validate = 'captcha_validate_strict_equality';
695 85ad3d82 Assos Assos
    }
696
    // Check the response with the CAPTCHA validation function.
697
    // Apart from the traditional expected $solution and received $response,
698
    // we also provide the CAPTCHA $element and $form_state arrays for more advanced use cases.
699
    if ($captcha_validate($solution, $captcha_response, $element, $form_state)) {
700
      // Correct answer.
701
702
      // Store form_id in session (but only if it is useful to do so, avoid setting stuff in session unnecessarily).
703
      $captcha_persistence = variable_get('captcha_persistence', CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_INSTANCE);
704
      if ($captcha_persistence == CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL || $captcha_persistence == CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_TYPE) {
705
        $_SESSION['captcha_success_form_ids'][$form_id] = $form_id;
706
      }
707
708
      // Record success.
709
      db_update('captcha_sessions')
710
        ->condition('csid', $csid)
711
        ->fields(array('status' => CAPTCHA_STATUS_SOLVED))
712
        ->expression('attempts', 'attempts + 1')
713
        ->execute();
714
    }
715
    else {
716
      // Wrong answer.
717
      db_update('captcha_sessions')
718
        ->condition('csid', $csid)
719
        ->expression('attempts', 'attempts + 1')
720
        ->execute();
721 ac1bc5de Assos Assos
      // Set form error.
722 85ad3d82 Assos Assos
      form_set_error('captcha_response', t('The answer you entered for the CAPTCHA was not correct.'));
723 ac1bc5de Assos Assos
      // Update wrong response counter.
724 85ad3d82 Assos Assos
      if (variable_get('captcha_enable_stats', FALSE)) {
725
        variable_set('captcha_wrong_response_counter', variable_get('captcha_wrong_response_counter', 0) + 1);
726
      }
727 ac1bc5de Assos Assos
      // Log to watchdog if needed.
728 85ad3d82 Assos Assos
      if (variable_get('captcha_log_wrong_responses', FALSE)) {
729
        watchdog('CAPTCHA',
730
          '%form_id post blocked by CAPTCHA module: challenge %challenge (by module %module), user answered "@response", but the solution was "@solution".',
731 ac1bc5de Assos Assos
          array(
732
            '%form_id' => $form_id,
733 85ad3d82 Assos Assos
            '@response' => $captcha_response, '@solution' => $solution,
734
            '%challenge' => $captcha_info['captcha_type'], '%module' => $captcha_info['module'],
735
          ),
736
          WATCHDOG_NOTICE);
737
      }
738
    }
739
  }
740
}
741
742
/**
743
 * Pre-render callback for additional processing of a CAPTCHA form element.
744
 *
745
 * This encompasses tasks that should happen after the general FAPI processing
746
 * (building, submission and validation) but before rendering (e.g. storing the solution).
747
 *
748 ac1bc5de Assos Assos
 * @param array $element
749
 *   the CAPTCHA form element
750
 *
751
 * @return array
752
 *   the manipulated element
753 85ad3d82 Assos Assos
 */
754
function captcha_pre_render_process($element) {
755
  module_load_include('inc', 'captcha');
756
757
  // Get form and CAPTCHA information.
758
  $captcha_info = $element['#captcha_info'];
759
  $form_id = $captcha_info['form_id'];
760 ac1bc5de Assos Assos
  $captcha_sid = (int) ($captcha_info['captcha_sid']);
761 85ad3d82 Assos Assos
  // Check if CAPTCHA is still required.
762
  // This check is done in a first phase during the element processing
763
  // (@see captcha_process), but it is also done here for better support
764
  // of multi-page forms. Take previewing a node submission for example:
765
  // when the challenge is solved correctely on preview, the form is still
766
  // not completely submitted, but the CAPTCHA can be skipped.
767
  if (_captcha_required_for_user($captcha_sid, $form_id) || $element['#captcha_admin_mode']) {
768
    // Update captcha_sessions table: store the solution of the generated CAPTCHA.
769
    _captcha_update_captcha_session($captcha_sid, $captcha_info['solution']);
770
771
    // Handle the response field if it is available and if it is a textfield.
772
    if (isset($element['captcha_widgets']['captcha_response']['#type']) && $element['captcha_widgets']['captcha_response']['#type'] == 'textfield') {
773
      // Before rendering: presolve an admin mode challenge or
774
      // empty the value of the captcha_response form item.
775
      $value = $element['#captcha_admin_mode'] ? $captcha_info['solution'] : '';
776
      $element['captcha_widgets']['captcha_response']['#value'] = $value;
777
    }
778
  }
779
  else {
780
    // Remove CAPTCHA widgets from form.
781
    unset($element['captcha_widgets']);
782
  }
783
784
  return $element;
785
}
786
787
/**
788
 * Default implementation of hook_captcha().
789
 */
790
function captcha_captcha($op, $captcha_type = '') {
791
  switch ($op) {
792
    case 'list':
793
      return array('Math');
794
795
    case 'generate':
796
      if ($captcha_type == 'Math') {
797
        $result = array();
798
        $answer = mt_rand(1, 20);
799
        $x = mt_rand(1, $answer);
800
        $y = $answer - $x;
801
        $result['solution'] = "$answer";
802
        // Build challenge widget.
803
        // Note that we also use t() for the math challenge itself. This makes
804
        // it possible to 'rephrase' the challenge a bit through localization
805
        // or string overrides.
806
        $result['form']['captcha_response'] = array(
807
          '#type' => 'textfield',
808
          '#title' => t('Math question'),
809
          '#description' => t('Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.'),
810
          '#field_prefix' => t('@x + @y = ', array('@x' => $x, '@y' => $y)),
811
          '#size' => 4,
812
          '#maxlength' => 2,
813
          '#required' => TRUE,
814
        );
815
        return $result;
816
      }
817
      elseif ($captcha_type == 'Test') {
818
        // This challenge is not visible through the administrative interface
819
        // as it is not listed in captcha_captcha('list'),
820
        // but it is meant for debugging and testing purposes.
821
        // TODO for Drupal 7 version: This should be done with a mock module,
822
        // but Drupal 6 does not support this (mock modules can not be hidden).
823
        $result = array(
824
          'solution' => 'Test 123',
825
          'form' => array(),
826
        );
827
        $result['form']['captcha_response'] = array(
828
          '#type' => 'textfield',
829
          '#title' => t('Test one two three'),
830
          '#required' => TRUE,
831
        );
832
        return $result;
833
      }
834
      break;
835
  }
836
}
837
838
/**
839 ac1bc5de Assos Assos
 * Implements hook_modules_enabled().
840 85ad3d82 Assos Assos
 */
841
function captcha_modules_enabled() {
842
  // When new modules are enabled: clear the CAPTCHA placement cache, so that
843
  // new hook_captcha_placement_map hooks can be triggered.
844
  variable_del('captcha_placement_map_cache');
845
}