Club Drupal

<?php

/**

 * @file

 * General CAPTCHA functionality and helper functions.

 */

/**

 * Helper function for adding/updating a CAPTCHA point.

 *

 * @param $form_id the form ID to configure.

 * @param captcha_type the setting for the given form_id, can be:

 *   - 'none' to disable CAPTCHA,

 *   - 'default' to use the default challenge type

 *   - NULL to remove the entry for the CAPTCHA type

 *   - something of the form 'image_captcha/Image'

 *   - an object with attributes $captcha_type->module and $captcha_type->captcha_type

 * @return nothing

 */

function captcha_set_form_id_setting($form_id, $captcha_type) {

  // Handle 'none'.

  if ($captcha_type == 'none') {

    db_merge('captcha_points')

      ->key(array('form_id' => $form_id))

      ->fields(array('module' => NULL, 'captcha_type' => NULL))

      ->execute();

  }

  // Handle 'default'.

  elseif ($captcha_type == 'default') {

    db_merge('captcha_points')

      ->key(array('form_id' => $form_id))

      ->fields(array('module' => NULL, 'captcha_type' => 'default'))

      ->execute();

  }

  // Handle NULL.

  elseif ($captcha_type == NULL) {

    db_delete('captcha_points')->condition('form_id', $form_id)->execute();

  }

  // Handle a captcha_type object.

  elseif (is_object($captcha_type) && isset($captcha_type->module) && isset($captcha_type->captcha_type)) {

    db_merge('captcha_points')

      ->key(array('form_id' => $form_id))

      ->fields(array('module' => $captcha_type->module, 'captcha_type' => $captcha_type->captcha_type))

      ->execute();

  }

  // Handle a captcha_type string.

  elseif (is_string($captcha_type) && substr_count($captcha_type, '/') == 1) {

    list($module, $type) = explode('/', $captcha_type);

    db_merge('captcha_points')

      ->key(array('form_id' => $form_id))

      ->fields(array('module' => $module, 'captcha_type' => $type))

      ->execute();

  }

  else {

    drupal_set_message(t('Failed to set a CAPTCHA type for form %form_id: could not interpret value "@captcha_type"',

      array('%form_id' => $form_id, '@captcha_type' => (string)$captcha_type)), 'warning');

  }

}

/**

 * Get the CAPTCHA setting for a given form_id.

 *

 * @param $form_id the form_id to query for

 * @param $symbolic flag to return as (symbolic) strings instead of object.

 *

 * @return NULL if no setting is known

 *   or a captcha_point object with fields 'module' and 'captcha_type'.

 *   If argument $symbolic is true, returns (symbolic) as 'none', 'default'

 *   or in the form 'captcha/Math'.

 */

function captcha_get_form_id_setting($form_id, $symbolic=FALSE) {

  $result = db_query("SELECT module, captcha_type FROM {captcha_points} WHERE form_id = :form_id",

    array(':form_id' =>  $form_id));

  $captcha_point = $result->fetchObject();

  if (!$captcha_point) {

    $captcha_point = NULL;

  }

  elseif ($captcha_point->captcha_type == 'default') {

    if (!$symbolic) {

      list($module, $type) = explode('/', variable_get('captcha_default_challenge', 'captcha/Math'));

      $captcha_point->module = $module;

      $captcha_point->captcha_type = $type;

    }

    else {

      $captcha_point = 'default';

    }

  }

  elseif ($captcha_point->module == NULL && $captcha_point->captcha_type == NULL && $symbolic) {

    $captcha_point = 'none';

  }

  elseif ($symbolic) {

    $captcha_point = $captcha_point->module . '/' . $captcha_point->captcha_type;

  }

  return $captcha_point;

}

/**

 * Helper function for generating a new CAPTCHA session.

 *

 * @param $form_id the form_id of the form to add a CAPTCHA to.

 * @param $status the initial status of the CAPTHCA session.

 * @return the session ID of the new CAPTCHA session.

 */

function _captcha_generate_captcha_session($form_id=NULL, $status=CAPTCHA_STATUS_UNSOLVED) {

  global $user;

  // Initialize solution with random data.

  $solution = md5(mt_rand());

  // Insert an entry and thankfully receive the value of the autoincrement field 'csid'.

  $captcha_sid = db_insert('captcha_sessions')

  ->fields(array(

    'uid' => $user->uid,

    'sid' => session_id(),

    'ip_address' => ip_address(),

    'timestamp' => REQUEST_TIME,

    'form_id' => $form_id,

    'solution' => $solution,

    'status' => $status,

    'attempts' => 0,

  ))

  ->execute();

  return $captcha_sid;

}

/**

 * Helper function for updating the solution in the CAPTCHA session table.

 *

 * @param $captcha_sid the CAPTCHA session ID to update.

 * @param $solution the new solution to associate with the given CAPTCHA session.

 */

function _captcha_update_captcha_session($captcha_sid, $solution) {

  db_update('captcha_sessions')

    ->condition('csid', $captcha_sid)

    ->fields(array(

      'timestamp' => REQUEST_TIME,

      'solution' => $solution,

    ))

    ->execute();

}

/**

 * Helper function for checking if CAPTCHA is required for user,

 * based on the CAPTCHA persistence setting, the CAPTCHA session ID and

 * user session info.

 */

function _captcha_required_for_user($captcha_sid, $form_id) {

  // Get the CAPTCHA persistence setting.

  $captcha_persistence = variable_get('captcha_persistence', CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_INSTANCE);

  // First check: should we always add a CAPTCHA?

  if ($captcha_persistence == CAPTCHA_PERSISTENCE_SHOW_ALWAYS) {

    return TRUE;

  }

  // Get the status of the current CAPTCHA session.

  $captcha_session_status = db_query('SELECT status FROM {captcha_sessions} WHERE csid = :csid', array(':csid' => $captcha_sid))->fetchField();

  // Second check: if the current session is already solved: omit further CAPTCHAs.

  if ($captcha_session_status == CAPTCHA_STATUS_SOLVED) {

    return FALSE;

  }

  // Third check: look at the persistence level (per form instance, per form or per user).

  if ($captcha_persistence == CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_INSTANCE) {

    return TRUE;

  }

  else {

    $captcha_success_form_ids = isset($_SESSION['captcha_success_form_ids']) ? (array)($_SESSION['captcha_success_form_ids']) : array();

    switch ($captcha_persistence) {

      case CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL:

        return (count($captcha_success_form_ids) == 0);

      case CAPTCHA_PERSISTENCE_SKIP_ONCE_SUCCESSFUL_PER_FORM_TYPE:

        return !isset($captcha_success_form_ids[$form_id]);

    }

  }

  // We should never get to this point, but to be sure, we return TRUE.

  return TRUE;

}

/**

 * Get the CAPTCHA description as configured on the general CAPTCHA

 * settings page.

 *

 * If the locale module is enabled, the description will be returned

 * for the current language the page is rendered for. This language

 * can optionally been overriden with the $lang_code argument.

 *

 * @param $lang_code an optional language code to get the descripion for.

 * @return a string with (localized) CAPTCHA description.

 */

function _captcha_get_description($lang_code=NULL) {

  // If no language code is given: use the language of the current page.

  global $language;

  $lang_code = isset($lang_code) ? $lang_code : $language->language;

  // The hardcoded but localizable default.

  $default = t('This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.', array(), array('langcode' => $lang_code));

  // Look up the configured CAPTCHA description or fall back on the (localized) default.

  if (module_exists('locale')) {

    $description = variable_get("captcha_description_$lang_code", $default);

  }

  else {

    $description = variable_get('captcha_description', $default);

  }

  return filter_xss_admin($description);

}

/**

 * Parse or interpret the given captcha_type.

 * @param $captcha_type string representation of the CAPTCHA type,

 *      e.g. 'default', 'none', 'captcha/Math', 'image_captcha/Image'

 * @return list($captcha_module, $captcha_type)

 */

function _captcha_parse_captcha_type($captcha_type) {

  if ($captcha_type == 'none') {

    return array(NULL, NULL);

  }

  if ($captcha_type == 'default') {

    $captcha_type = variable_get('captcha_default_challenge', 'captcha/Math');

  }

  return explode('/', $captcha_type);

}

/**

 * Helper function to get placement information for a given form_id.

 * @param $form_id the form_id to get the placement information for.

 * @param $form if a form corresponding to the given form_id, if there

 *   is no placement info for the given form_id, this form is examined to

 *   guess the placement.

 * @return placement info array (@see _captcha_insert_captcha_element() for more

 *   info about the fields 'path', 'key' and 'weight'.

 */

function _captcha_get_captcha_placement($form_id, $form) {

  // Get CAPTCHA placement map from cache. Two levels of cache:

  // static variable in this function and storage in the variables table.

  static $placement_map = NULL;

  // Try first level cache.

  if ($placement_map === NULL) {

    // If first level cache missed: try second level cache.

    $placement_map = variable_get('captcha_placement_map_cache', NULL);

    if ($placement_map === NULL) {

      // If second level cache missed: initialize the placement map

      // and let other modules hook into this with the hook_captcha_placement_map hook.

      // By default however, probably all Drupal core forms are already correctly

      // handled with the best effort guess based on the 'actions' element (see below).

      $placement_map = module_invoke_all('captcha_placement_map');

    }

  }

  // Query the placement map.

  if (array_key_exists($form_id, $placement_map)) {

    $placement = $placement_map[$form_id];

  }

  // If no placement info is available in placement map: make a best effort guess.

  else {

    // If there is an "actions" button group, a good placement is just before that.

    if (isset($form['actions']) && isset($form['actions']['#type']) && $form['actions']['#type'] === 'actions') {

      $placement = array(

        'path' => array(),

        'key' => 'actions',

        // #type 'actions' defaults to 100.

        'weight' => (isset($form['actions']['#weight']) ? $form['actions']['#weight'] - 1 : 99),

      );

    }

    else {

      // Search the form for buttons and guess placement from it.

      $buttons = _captcha_search_buttons($form);

      if (count($buttons)) {

        // Pick first button.

        // TODO: make this more sofisticated? Use cases needed.

        $placement = $buttons[0];

      }

      else {

        // Use NULL when no buttons were found.

        $placement = NULL;

      }

    }

    // Store calculated placement in cache.

    $placement_map[$form_id] = $placement;

    variable_set('captcha_placement_map_cache', $placement_map);

  }

  return $placement;

}

/**

 * Helper function for searching the buttons in a form.

 *

 * @param $form the form to search button elements in

 * @return an array of paths to the buttons.

 *   A path is an array of keys leading to the button, the last

 *   item in the path is the weight of the button element

 *   (or NULL if undefined).

 */

function _captcha_search_buttons($form) {

  $buttons = array();

  foreach (element_children($form) as $key) {

    // Look for submit or button type elements.

    if (isset($form[$key]['#type']) && ($form[$key]['#type'] == 'submit' || $form[$key]['#type'] == 'button')) {

      $weight = isset($form[$key]['#weight']) ? $form[$key]['#weight'] : NULL;

      $buttons[] = array(

        'path' => array(),

        'key' => $key,

        'weight' => $weight,

      );

    }

    // Process children recurively.

    $children_buttons = _captcha_search_buttons($form[$key]);

    foreach ($children_buttons as $b) {

      $b['path'] = array_merge(array($key), $b['path']);

      $buttons[] = $b;

    }

  }

  return $buttons;

}

/**

 * Helper function to insert a CAPTCHA element in a form before a given form element.

 * @param $form the form to add the CAPTCHA element to.

 * @param $placement information where the CAPTCHA element should be inserted.

 *   $placement should be an associative array with fields:

 *     - 'path': path (array of path items) of the container in the form where the

 *       CAPTCHA element should be inserted.

 *     - 'key': the key of the element before which the CAPTCHA element

 *       should be inserted. If the field 'key' is undefined or NULL, the CAPTCHA will

 *       just be appended in the container.

 *     - 'weight': if 'key' is not NULL: should be the weight of the element defined by 'key'.

 *       If 'key' is NULL and weight is not NULL: set the weight property of the CAPTCHA element

 *       to this value.

 * @param $captcha_element the CAPTCHA element to insert.

 */

function _captcha_insert_captcha_element(&$form, $placement, $captcha_element) {

  // Get path, target and target weight or use defaults if not available.

  $target_key = isset($placement['key']) ? $placement['key'] : NULL;

  $target_weight = isset($placement['weight']) ? $placement['weight'] : NULL;

  $path = isset($placement['path']) ? $placement['path'] : array();

  // Walk through the form along the path.

  $form_stepper = &$form;

  foreach ($path as $step) {

    if (isset($form_stepper[$step])) {

      $form_stepper = & $form_stepper[$step];

    }

    else {

      // Given path is invalid: stop stepping and

      // continue in best effort (append instead of insert).

      $target_key = NULL;

      break;

    }

  }

  // If no target is available: just append the CAPTCHA element to the container.

  if ($target_key == NULL || !array_key_exists($target_key, $form_stepper)) {

    // Optionally, set weight of CAPTCHA element.

    if ($target_weight != NULL) {

      $captcha_element['#weight'] = $target_weight;

    }

    $form_stepper['captcha'] =  $captcha_element;

  }

  // If there is a target available: make sure the CAPTCHA element comes right before it.

  else {

    // If target has a weight: set weight of CAPTCHA element a bit smaller

    // and just append the CAPTCHA: sorting will fix the ordering anyway.

    if ($target_weight != NULL) {

      $captcha_element['#weight'] = $target_weight - .1;

      $form_stepper['captcha'] =  $captcha_element;

    }

    else {

      // If we can't play with weights: insert the CAPTCHA element at the right position.

      // Because PHP lacks a function for this (array_splice() comes close,

      // but it does not preserve the key of the inserted element), we do it by hand:

      // chop of the end, append the CAPTCHA element and put the end back.

      $offset = array_search($target_key, array_keys($form_stepper));

      $end = array_splice($form_stepper, $offset);

      $form_stepper['captcha'] =  $captcha_element;

      foreach ($end as $k => $v) {

        $form_stepper[$k] = $v;

      }

    }

  }

}