masquerade.module

<?php

/**
 * @file
 * The masquerade module allows administrators to masquerade as other user.
 */

/**
 * Implements hook_config_info().
 */
function masquerade_config_info() {
  $prefixes['masquerade.settings'] = array(
    'label' => t('Masquerade settings'),
    'group' => t('Configuration'),
  );
  return $prefixes;
}

/**
 * Implements hook_permission().
 *
 * @return array
 */
function masquerade_permission() {
  return array(
    'masquerade as user' => array(
      'title' => t('Masquerade as user'),
      'description' => t('Masquerade as another user.'),
    ),
    'masquerade as any user' => array(
      'title' => t('Masquerade as any user'),
      'description' => t('Masquerade as any user.'),
      'restrict access' => TRUE,
    ),
    'masquerade as admin' => array(
      'title' => t('Masquerade as admin'),
      'description' => t('Masquerade as the site admin (UID 1).'),
      'restrict access' => TRUE,
    ),
    'administer masquerade' => array(
      'title' => t('Administer Masquerade'),
      'description' => t('Perform administration tasks and configure the Masquerade module.'),
      'restrict access' => TRUE,
    ),
  );
}

/**
 * Implements hook_init().
 */
function masquerade_init() {
  global $user;

  // Try to load masqing uid from masquerade table.
  $uid = db_query("SELECT uid_from FROM {masquerade} WHERE sid = :sid AND uid_as = :uid_as", array(
    ':sid' => session_id(),
    ':uid_as' => $user->uid,
  ))->fetchField();

  // We are using identical operator (===) instead of equal (==) because if
  // $uid === 0 we want to store the session variable. If there's no record in
  // masquerade table we clear the session variable.
  if ($uid === FALSE) {
    if (isset($_SESSION)) {
      unset($_SESSION['masquerading']);
    }
  }
  else {
    $_SESSION['masquerading'] = $uid;
  }
}

/**
 * Implements hook_cron().
 *
 * Cleanup masquerade records where people didn't use the switch back link
 * that would have cleanly removed the user switch record.
 */
function masquerade_cron() {
  // see http://backdrop.org/node/268487 before modifying this query
  $subquery = db_select('sessions', 's');
  $subquery->addField('s', 'sid');

  $query = db_delete('masquerade');
  $query->condition('sid', $subquery, 'NOT IN');
  $query->execute();
}

/**
 * Implements hook_menu().
 */
function masquerade_menu() {
  $items = array();
  $config = config('masquerade.settings');

  $default_test_user = _masquerade_user_load($config->get('test_user'));
  if ($default_test_user && ($default_test_user->uid || $default_test_user->name == t(config_get('system.core', 'anonymous')))) {
    $items['masquerade/switch/' . $default_test_user->uid] = array(
      'title' => 'Masquerade as @testuser',
      'title arguments' => array('@testuser' => $default_test_user->name),
      'page callback' => 'masquerade_switch_user_page',
      'page arguments' => array(2),
      'access callback' => 'masquerade_menu_access',
      'access arguments' => array('switch'),
      'type' => MENU_NORMAL_ITEM,
    );
  }

  $items['masquerade/switch/%'] = array(
    'title' => 'Masquerading',
    'page callback' => 'masquerade_switch_user_page',
    'page arguments' => array(2),
    'access callback' => 'masquerade_menu_access',
    'access arguments' => array('switch', 2),
    'type' => MENU_NORMAL_ITEM,
  );
  $items['masquerade/unswitch'] = array(
    'title' => 'Switch back',
    'page callback' => 'masquerade_switch_back_page',
    'access callback' => 'masquerade_menu_access',
    'access arguments' => array('unswitch'),
    'type' => MENU_NORMAL_ITEM,
  );
  $items['masquerade/autocomplete'] = array(
    'title' => '',
    'page callback' => 'masquerade_autocomplete',
    'access callback' => 'masquerade_menu_access',
    'access arguments' => array('autocomplete'),
    'type' => MENU_CALLBACK,
  );
  $items['masquerade/autocomplete-users'] = array(
    'title' => '',
    'page callback' => 'masquerade_autocomplete_multiple',
    'access callback' => 'masquerade_menu_access',
    'access arguments' => array('autocomplete'),
    'type' => MENU_CALLBACK,
  );
  $items['masquerade/autocomplete-user'] = array(
    'title' => 'Masquerade autocomplete',
    'page callback' => 'masquerade_autocomplete_multiple',
    'page arguments' => array(2, FALSE),
    'access arguments' => array('access user profiles'),
    'type' => MENU_CALLBACK,
  );
  $items['admin/config/people/masquerade'] = array(
    'title' => 'Masquerade',
    'description' => 'Masquerade module allows administrators to masquerade as other users.',
    'page callback' => 'backdrop_get_form',
    'page arguments' => array('masquerade_admin_settings'),
    'access callback' => 'user_access',
    'access arguments' => array('administer masquerade'),
    'type' => MENU_NORMAL_ITEM,
  );

  return $items;
}

/**
 * Implements hook_menu_alter().
 *
 * We need to add a token to the Masquerade paths to protect against CSRF
 * attacks. Since menu items in Backdrop do not support dynamic elements these
 * tokens need to be added during rendering via masquerade_translated_menu_link_alter().
 * Set the 'alter'-option to TRUE to make sure
 * the links get passed through masquerade_translated_menu_link_alter.
 */
function masquerade_menu_alter(&$items) {
  $config = config('masquerade.settings');
  $default_test_user = _masquerade_user_load($config->get('test_user'));
  if (isset($default_test_user->uid)) {
    $items['masquerade/switch/' . $default_test_user->uid]['options']['alter'] = TRUE;
  }
  $items['masquerade/switch/%']['options']['alter'] = TRUE;
  $items['masquerade/unswitch']['options']['alter'] = TRUE;
}

/**
 * Implements hook_translated_menu_link_alter().
 *
 * Dynamically add the CSRF protection token to the Masquerade menu items.
 */
function masquerade_translated_menu_link_alter(&$item, $map) {
  if (isset($item['page_callback'])) {
    if ($item['page_callback'] == 'masquerade_switch_user_page' && isset($map[2])) {
      $item['localized_options']['query']['token'] = backdrop_get_token('masquerade/switch/' . $map[2]);
    }
    elseif ($item['page_callback'] == 'masquerade_switch_back_page') {
      $item['localized_options']['query']['token'] = backdrop_get_token('masquerade/unswitch');
    }
  }
}

/**
 * Implements hook_user_operations().
 */
function masquerade_user_operations() {
  return array(
    'masquerade' => array(
      'label' => t('Masquerade as user'),
      'callback' => 'masquerade_user_operations_masquerade',
    ),
  );
}

/**
 * Callback for user operation.
 */
function masquerade_user_operations_masquerade(array $accounts) {
  // Only process the first account since switching to multiple makes no sense.
  if (($uid = current($accounts)) && masquerade_menu_access('switch', $uid)) {
    masquerade_switch_user($uid);
  }
}

/**
 * Determine if the current user has permission to switch users.
 *
 * @param string $type
 *   Either 'switch', 'unswitch', 'user', or 'autocomplete'.
 *
 * @param object $uid
 *   An optional parameter indicating a specific uid to switch to.
 *   Otherwise, return if the user can switch to any user account.
 *
 * @return
 *   TRUE, if the user can perform the requested action, FALSE otherwise.
 */

function masquerade_menu_access($type, $uid = NULL) {
  switch ($type) {
    case 'unswitch':
      return isset($_SESSION['masquerading']) || arg(2) == 'menu-customize' || arg(2) == 'menu';
    case 'autocomplete':
      return isset($_SESSION['masquerading']) || (user_access('masquerade as user') || user_access('masquerade as admin'));
      break;
    case 'user':
      global $user;
      return db_query("SELECT 1 FROM {masquerade_users} WHERE uid_from = :uid_from", array(':uid_from' => $user->uid))->fetchField();
      break;
    case 'switch':
      $switch_to_account = FALSE;
      global $user;
      if ($uid) {
        if (!is_numeric($uid)) {
          return FALSE;
        }
        if ($account = user_load($uid)) {
          $switch_to_account = db_query("SELECT 1 FROM {masquerade_users} WHERE uid_from = :uid_from AND uid_to = :uid_to", array(
            ':uid_from' => $user->uid,
            ':uid_to' => $account->uid
          ))->fetchField();
        }
      }
      return !isset($_SESSION['masquerading']) && (user_access('masquerade as user') || user_access('masquerade as admin') || $switch_to_account);
      break;
  }
}

/**
 * Admin settings form.
 */
function masquerade_admin_settings() {
  $config = config('masquerade.settings');
  // create a list of roles; all selected roles are considered administrative.
  $roles = user_roles();
  $form['masquerade_admin_roles'] = array(
    '#type' => 'checkboxes',
    '#title' => t('Roles that are considered "administrators" for masquerading'),
    '#options' => $roles,
    '#default_value' => $config->get('admin_roles'),
    '#description' => t('Only the users with <strong>masquerade as admin</strong> permission, will be able to masquerade as the users who belong to the roles selected below. User #1 is automatically considered an administrator, regardless of roles.'),
  );

  $test_name = _masquerade_user_load($config->get('test_user'));

  $form['masquerade_test_user'] = array(
    '#type' => 'textfield',
    '#title' => t('Menu <em>Quick Switch</em> user'),
    '#autocomplete_path' => 'masquerade/autocomplete',
    '#default_value' => isset($test_name->name) ? check_plain($test_name->name) : '',
    '#description' => t('Enter the username of an account you wish to switch easily between via a menu item.'),
    '#maxlength' => NULL,
  );

  $quick_switch = user_load_multiple($config->get('quick_switches'));

  $quick_switch_users = array();
  foreach ($quick_switch as $uid => $account) {
    if ($uid == 0) {
      $account->name = t(config_get('system.core', 'anonymous'));
    }
    $quick_switch_users[] = $account->name;
  }

  $form['masquerade_quick_switches'] = array(
    '#type' => 'textfield',
    '#title' => t('Masquerade Block <em>Quick Switch</em> users'),
    '#autocomplete_path' => 'masquerade/autocomplete-users',
    '#default_value' => backdrop_implode_tags($quick_switch_users),
    '#description' => t('Enter the usernames, separated by commas, of accounts to show as quick switch links in the Masquerade block.'),
    '#maxlength' => NULL,
  );

  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save Configuration')
  );

  $form['#validate'][] = 'masquerade_admin_settings_validate';
  $form['#submit'][] = 'masquerade_admin_settings_submit';

  return $form;
}

function masquerade_admin_settings_validate($form, &$form_state) {
  $config = config('masquerade.settings');
  if (!empty($form_state['values']['masquerade_test_user'])) {
    $test_user = _masquerade_user_load($form_state['values']['masquerade_test_user']);
    if (!$test_user) {
      form_set_error('masquerade_test_user', t('%user does not exist. Please enter a valid username.', array('%user' => $form_state['values']['masquerade_test_user'])));
    }
  }
  // Needs to rebuild menu in masquerade_admin_settings_submit().
  $form_state['masquerade_rebuild_menu'] = ($config->get('test_user') != $form_state['values']['masquerade_test_user']);

  // A comma-separated list of users.
  $masquerade_switches = backdrop_explode_tags($form_state['values']['masquerade_quick_switches']);
  // Change user names to user ID's for system_settings_form_submit() to save.
  $masquerade_uids = array();
  foreach ($masquerade_switches as $switch_user) {
    $test_user = _masquerade_user_load($switch_user);
    if (!$test_user) {
      form_set_error('masquerade_quick_switches', t('%user does not exist. Please enter a valid username.', array('%user' => $switch_user)));
    }
    else {
      $masquerade_uids[] = $test_user->uid;
    }
  }
  $form_state['values']['masquerade_quick_switches'] = $masquerade_uids;
}

function masquerade_admin_settings_submit($form, &$form_state) {
  $config = config('masquerade.settings');

  $values = $form_state['values'];

  $config->set('admin_roles', $values['masquerade_admin_roles']);
  $config->set('test_user', $values['masquerade_test_user']);
  $config->set('quick_switches', $values['masquerade_quick_switches']);

  $config->save();

  // Rebuild the menu system so the menu "Quick Switch" user is updated.
  if ($form_state['masquerade_rebuild_menu']) {
    menu_rebuild();
  }

  backdrop_set_message(t('The configuration options have been saved.'));
}

/**
 * Wrapper around user_load() to allow the loading of anonymous users.
 *
 * @param $username
 *   The username of the user you wish to load (i.e. $user->name). To load the
 *   anonymous user, pass the value of the 'anonymous' variable.
 *
 * @return
 *   A fully-loaded $user object upon successful user load or FALSE if user
 *   cannot be loaded.
 */
function _masquerade_user_load($username) {
  $config = config('masquerade.settings');
  $account = FALSE;
  if (!empty($username)) {
    $anon = t(config_get('system.core', 'anonymous'));
    $account = user_load_by_name(($username == $anon ? '' : $username));
    if (isset($account->uid) && empty($account->uid)) {
      // Anonymous user should have a name.
      $account->name = $anon;
    }
  }
  return $account;
}

/**
 * Implements hook_user_logout().
 */
function masquerade_user_logout($account) {
  if (!empty($account->masquerading)) {
    global $user;
    cache_clear_all($user->uid, 'cache_menu', TRUE);
    $real_user = user_load($user->masquerading);
    watchdog('masquerade', "User %user no longer masquerading as %masq_as.", array('%user' => $real_user->name, '%masq_as' => $user->name), WATCHDOG_INFO);

    $query = db_delete('masquerade');
    $query->condition('sid', session_id());
    $query->condition('uid_as', $account->uid);
    $query->execute();
  }
}

/**
 * Implements hook_field_extra_fields().
 */
function masquerade_field_extra_fields() {
  $return['user']['user']  = array(
    'form' => array(
      'masquerade' => array(
        'label' => t('Masquerade'),
        'description' => t('User masquerade settings.'),
        'weight' => 50,
      ),
    ),
    'display' => array(
      'masquerade' => array(
        'label' => t('Masquerade'),
        'description' => t('Masquerade as user link.'),
        'weight' => 50,
      ),
    ),
  );

  return $return;
}

/**
 * Implements hook_user_view().
 */
function masquerade_user_view($account, $view_mode, $langcode) {
  $config = config('masquerade.settings');
  // Check if user qualifies as admin.
  $roles = !empty($config->get('admin_roles')) ? array_filter($config->get('admin_roles')) : array();
  $perm = $account->uid == 1 || array_intersect((array)$account->roles, $roles) ?
    'masquerade as admin' :
    'masquerade as user';

  global $user;

  // Query allowed uids so the "masquerade as <user>" link can be shown or
  // hidden.
  $allowed_uids = db_query("SELECT uid_to FROM {masquerade_users} WHERE uid_from = :uid_from", array(':uid_from' => $user->uid))
    ->fetchCol();
  $can_masquerade_as_user = in_array($account->uid, $allowed_uids) || user_access('masquerade as any user');

  if (user_access($perm) && empty($account->masquerading) && $user->uid != $account->uid && $can_masquerade_as_user) {
    $account->content['masquerade'] = array(
      '#markup' => l(t('Masquerade as !user', array('!user' => $account->name)),
        'masquerade/switch/' . $account->uid,
        array('query' => array(
          'token' => backdrop_get_token('masquerade/switch/' . $account->uid)),
          'destination' => $_GET['q'],
          'attributes' => array('class' => array('masquerade-switch')),
        )),
      '#weight' => 10,
    );
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function masquerade_form_user_profile_form_alter(&$form, &$form_state, $form_id) {
  $config = config('masquerade.settings');

  $form['masquerade'] = array(
    '#type' => 'fieldset',
    '#title' => t('Masquerade settings'),
    '#access' => user_access('administer masquerade'),
  );
  $edit_user = $form['#user'];
  $uids = db_query("SELECT uid_to FROM {masquerade_users} WHERE uid_from = :uid_from", array(':uid_from' => $edit_user->uid))
    ->fetchCol();
  $users = user_load_multiple($uids);
  $masquerade_users = array();
  foreach ($users as $uid => $account) {
    if ($uid == 0) {
      $masquerade_users[] = t(config_get('system.core', 'anonymous'));
    }
    else {
      $masquerade_users[] = $account->name;
    }
  }
  $form['masquerade']['masquerade_users'] = array(
    '#type' => 'textfield',
    '#title' => t('Enter the users this user is able to masquerade as'),
    '#description' => t('Enter a comma separated list of user names that this user can masquerade as.'),
    '#autocomplete_path' => 'masquerade/autocomplete-user',
    '#default_value' => backdrop_implode_tags($masquerade_users),
    '#maxlength' => NULL,
  );
  $form['#validate'][] = 'masquerade_user_validate';
  $form['#submit'][] = 'masquerade_user_submit';
}

/**
 * Validates user account form.
 */
function masquerade_user_validate(&$form, $form_state) {
  if (isset($form_state['values']['masquerade_users'])) {
    $users = backdrop_explode_tags($form_state['values']['masquerade_users']);
    foreach ($users as $username) {
      if (!_masquerade_user_load($username)) {
        form_set_error('masquerade_users', t('%user is not a valid user name.', array('%user' => $username)));
      }
    }
  }
}

/**
 * Submit handler for masquerade users form element.
 */
function masquerade_user_submit(&$form, $form_state) {
  global $_masquerade_old_session_id;
  $_masquerade_old_session_id = session_id();
}

/**
 * Implements hook_user_update().
 *
 */
function masquerade_user_update($account) {

  global $_masquerade_old_session_id;
  if (isset($account->masquerade_users)) {
    $query = db_delete('masquerade_users');
    $query->condition('uid_from', $account->uid);
    $query->execute();
    // Save users from settings form.
    $masquerade_users = backdrop_explode_tags($account->masquerade_users);
    $query = db_insert('masquerade_users')->fields(array('uid_from', 'uid_to'));
    foreach ($masquerade_users as $username) {
      if ($to_user = _masquerade_user_load($username)) {
        $query->values(array(
          'uid_from' => $account->uid,
          'uid_to' => $to_user->uid,
        ));
      }
    }
    $query->execute();
    $account->masquerade_users = NULL;

    // Update user session...
    // @TODO check other way of session API.
    if (!empty($_masquerade_old_session_id)) {
      $query = db_update('masquerade');
      $query->fields(array(
        'sid' => session_id(),
      ));
      $query->condition('sid', $_masquerade_old_session_id);
      $query->execute();
    }
  }
}

/**
 * Implements hook_user_delete().
 */
function masquerade_user_delete($account) {
  $config = config('masquerade.settings');
  // Cleanup tables.
  $query = db_delete('masquerade_users');
  $conditions = db_or();
  $conditions->condition('uid_from', $account->uid);
  $conditions->condition('uid_to', $account->uid);
  $query->condition($conditions);
  $query->execute();
  // Cleanup variables.
  $switches = $config->get('quick_switches');
  $switches_new = array_diff($switches, array($account->uid));
  if ($switches != $switches_new) {
    $config->set('quick_switches', $switches_new);
    $config->save();
    // @TODO Implement block cache cleaning.
    menu_rebuild();
  }
}

/**
 * Implements hook_block_info().
 */
function masquerade_block_info() {
  $blocks = array();
  $blocks['masquerade'] = array(
    'info' => t('Masquerade'),
    'cache' => BACKDROP_NO_CACHE,
  );
  return $blocks;
}

/**
 * Implements hook_block_view().
 */
function masquerade_block_view($delta = '') {
  $block = array();
  switch ($delta) {
    case 'masquerade':
      if (isset($_SESSION['masquerading']) || (user_access('masquerade as user') || user_access('masquerade as admin'))) {
        $block['subject'] = t('Masquerade');
        $block['content'] = backdrop_get_form('masquerade_block_1');
      }
      break;
  }
  return $block;
}

/**
 * Masquerade block form.
 */
function masquerade_block_1() {
  $config = config('masquerade.settings');
  global $user;
  $quick_switch_links = array();
  $markup_value = '';
  if (isset($_SESSION['masquerading'])) {
    $quick_switch_links[] = l(t('Switch back'), 'masquerade/unswitch', array('query' => array('token' => backdrop_get_token('masquerade/unswitch'))));
    if ($user->uid > 0) {
      $markup_value = t('You are masquerading as <a href="@user-url">%masq_as</a>.', array('@user-url' => url('user/' . $user->uid), '%masq_as' => $user->name));
    }
    else {
      $markup_value = t('You are masquerading as %anonymous.', array('%anonymous' => t(config_get('system.core', 'anonymous'))));
    }
  }
  else {
    $quick_switches = $config->get('quick_switches');
    $admin_roles = array_filter($config->get('admin_roles'));

    // Add in user-specific switches, and prevent duplicates.
    $user_switches = db_query("SELECT uid_to FROM {masquerade_users} WHERE uid_from = :uid_from", array(':uid_from' => $user->uid))->fetchCol();
    $masquerade_switches = array_unique(array_merge($quick_switches, $user_switches));

    foreach ($masquerade_switches as $switch_user) {
      if (!isset($_SESSION['user']->uid) || $switch_user != $_SESSION['user']->uid) {
        $account = user_load($switch_user);
        if (isset($account->uid)) {
          $switch_link = 'masquerade/switch/' . $account->uid;
          $perm = $user->uid == 1 || array_intersect((array) $account->roles, $admin_roles) ?
            'masquerade as admin' :
            'masquerade as user';
          if ($account->uid && user_access($perm)) {
            $quick_switch_links[] = l($account->name, $switch_link, array('query' => array('token' => backdrop_get_token($switch_link))));
          }
          if ($switch_user == 0) {
            $account->name = t(config_get('system.core', 'anonymous'));
            $quick_switch_links[] = l($account->name, $switch_link, array('query' => array('token' => backdrop_get_token($switch_link))));
          }
        }
      }
    }

    if (masquerade_menu_access('autocomplete')) {
      $markup_value .= t('Enter the username to masquerade as.');
      $form['masquerade_user_field'] = array(
        '#prefix' => '<div class="container-inline">',
        '#type' => 'textfield',
        '#size' => '18',
        '#default_value' => '',
        '#autocomplete_path' => 'masquerade/autocomplete',
        '#required' => TRUE,
      );
      $form['submit'] = array(
        '#type' => 'submit',
        '#value' => t('Go'),
        '#suffix' => '</div>',
      );
    }

  }
  if ($quick_switch_links) {
    $markup_value .= '<div id="quick_switch_links">' . t('Quick switches:') . theme('item_list', array('items' => $quick_switch_links)) . '</div>';
  }
  $form['masquerade_desc'] = array(
    '#prefix' => '<div class="form-item"><div class="description">',
    '#markup' => $markup_value,
    '#suffix' => '</div></div>',
  );
  return $form;
}

/**
 * Masquerade block form validation.
 */
function masquerade_block_1_validate($form, &$form_state) {
  $config = config('masquerade.settings');
  global $user;
  //unset($form);
  $name = $form_state['values']['masquerade_user_field'];
  $allowed = FALSE;
  $to_uid = db_select('users', 'u')
    ->fields('u', array('uid'))
    ->condition('u.name', $name, '=')
    ->execute()
    ->fetchField();
  if ($to_uid !== FALSE) {
    $allowed = user_access('masquerade as any user') ||
               db_select('masquerade_users', 'm')
                  ->fields('m', array('uid_to'))
                  ->condition('m.uid_to', $to_uid, '=')
                  ->condition('m.uid_from', $user->uid, '=')
                  ->execute()
                  ->fetchField();
  }
  if (isset($_SESSION['masquerading'])) {
    form_set_error('masquerade_user_field', t('You are already masquerading. Please <a href="@unswitch">switch back</a> to your account to masquerade as another user.', array('@unswitch' => url('masquerade/unswitch', array('query' => array('token' => backdrop_get_token('masquerade/unswitch')))))));
  }
  if ($allowed === FALSE) {
    form_set_error('masquerade_user_field', t('You are not allowed to masquerade as the selected user.'));
  }

  if ($name != t(config_get('system.core', 'anonymous')) && module_exists('alt_login')) {
    $alt_login = db_query("SELECT u.name FROM {users} u INNER JOIN {alt_login} al ON u.uid = al.uid WHERE al.alt_login = :alt_login", array(
      ':alt_login' => $name
    ))->fetchObject();
    if (isset($alt_login->name)) {
      $name = $alt_login->name;
    }
  }
  $masq_user = _masquerade_user_load($name);
  if (!$masq_user) {
    form_set_error('masquerade_user_field', t('User %masq_as does not exist. Please enter a valid username.', array('%masq_as' => $form_state['values']['masquerade_user_field'])));
  }
  elseif ($masq_user->uid == $user->uid) {
    form_set_error('masquerade_user_field', t('You cannot masquerade as yourself. Please choose a different user to masquerade as.'));
  }
  elseif (state_get('maintenance_mode') && !user_access('access site in maintenance mode', $masq_user)) {
    form_set_error('masquerade_user_field', t('It is not possible to masquerade in off-line mode as !user does not have the %config-perm permission. Please <a href="@site-maintenance">set the site status</a> to "online" to masquerade as !user.', array('!user' => theme('username', array('account' => $masq_user)), '%config-perm' => 'use the site in maintenance mode', '@site-maintenance' => url('admin/settings/site-maintenance'))));
  }
  else {
    $form_state['values']['masquerade_user_field'] = $name;
  }
}

/**
 * Masquerade block form submission.
 */
function masquerade_block_1_submit($form, &$form_state) {
  //unset($form);
  $masq_user = _masquerade_user_load($form_state['values']['masquerade_user_field']);
  if (!masquerade_switch_user($masq_user->uid)) {
    backdrop_access_denied();
  }
  else {
    backdrop_goto($_SERVER['HTTP_REFERER']);
  }
}

/**
 * Returns JS array for Masquerade autocomplete fields.
 */
function masquerade_autocomplete($string) {
  $config = config('masquerade.settings');

  // Check if user qualifies as admin.
  $admin_roles = array_filter($config->get('admin_roles'));
  global $user;

  $matches = array();
  // Anonymous user goes first to be visible for user.
  $anonymous = t(config_get('system.core', 'anonymous'));
  if (stripos($anonymous, $string) === 0) {
    $matches[$anonymous] = $anonymous;
  }
  // Other suggestions.
  $result = db_query_range("SELECT uid, name FROM {users} WHERE LOWER(name) LIKE LOWER(:string)", 0, 10, array(
    ':string' => $string . '%',
  ));
  foreach ($result as $switch_user) {
    $account = user_load($switch_user->uid);
    $perm = $user->uid == 1 || array_intersect((array) $account->roles, $admin_roles) ?
      'masquerade as admin' :
      'masquerade as user';
    if (user_access($perm)) {
      $matches[$account->name] = check_plain($account->name);
    }
  }
  if (module_exists('devel')) {
    $GLOBALS['devel_shutdown'] = FALSE;
  }
  backdrop_json_output($matches);
}

/**
 * Returns JS array for Masquerade autocomplete fields.
 *
 * Supports multiple entries separated by a comma.
 *
 * @param $string
 *   The string of autocmplete value submitted by the user.
 * @param $add_anonymous
 *   Flag to include Anonymous user into result.
 */
function masquerade_autocomplete_multiple($string, $add_anonymous = TRUE) {
  $config = config('masquerade.settings');
  $matches = array();
  // The user enters a comma-separated list of users. We only autocomplete the last user.
  $users_typed = backdrop_explode_tags($string);
  // Fetch last string.
  $last_string = backdrop_strtolower(array_pop($users_typed));
  if ($last_string) {
    $prefix = count($users_typed) ? implode(', ', $users_typed) . ', ' : '';
    if ($add_anonymous) {
      // Anonymous user goes first to be visible for user.
      $anonymous = t(config_get('system.core', 'anonymous'));
      if (stripos($anonymous, $last_string) === 0) {
        $matches[$prefix . $anonymous] = $anonymous;
      }
    }
    // Other suggestions.
    $result = db_query_range("SELECT name FROM {users} WHERE LOWER(name) LIKE :string", 0, 10, array(
      ':string' => $last_string . '%',
    ));
    foreach ($result as $user) {
      $matches[$prefix . $user->name] = check_plain($user->name);
    }

    // Remove existing tags.
    $matches = array_diff($matches, $users_typed);

    // @todo Check compatibility for D7.
    if (module_exists('alt_login')) {
      $result = db_query_range("SELECT u.alt_login AS alt_login FROM {alt_login} u WHERE LOWER(u.alt_login) LIKE LOWER(:string)", 0, 10, array(
        ':string' => $last_string . '%',
      ));
      foreach ($result as $user) {
        $matches[$user->alt_login] = check_plain($user->alt_login);
      }
    }
  }
  if (module_exists('devel')) {
    $GLOBALS['devel_shutdown'] = FALSE;
  }
  backdrop_json_output($matches);
}

/**
 * Page callback to switch users.
 */
function masquerade_switch_user_page($uid) {
  if (isset($_GET['token']) && backdrop_valid_token($_GET['token'], 'masquerade/switch/' . $uid) && masquerade_switch_user($uid)) {
    backdrop_goto($_SERVER['HTTP_REFERER']);
  }
  else {
    backdrop_access_denied();
  }
}

/**
 * Allows a user with the right permissions to become the selected user.
 *
 * @param $uid
 *   The user ID to switch to.
 *
 * @return
 *   TRUE if the user was sucessfully switched, or FALSE if there was an error.
 */
function masquerade_switch_user($uid) {
  $config = config('masquerade.settings');
  global $user;
  if (!is_numeric($uid)) {
    backdrop_set_message(t('A user id was not correctly passed to the switching function.'));
    watchdog('masquerade', 'The user id provided to switch users was not numeric.', NULL, WATCHDOG_ERROR);
    return backdrop_goto($_SERVER['HTTP_REFERER']);
  }

  $new_user = user_load($uid);

  $roles = array_keys(array_filter($config->get('admin_roles')));
  $perm = $uid == 1 || array_intersect($new_user->roles, $roles) ?
    'masquerade as admin' :
    'masquerade as user';

  // Check to see if we need admin permission.
  $results = db_query_range('SELECT 1 FROM {masquerade_users} WHERE uid_from = :uid_from AND uid_to = :uid_to', 0, 1, array(
    ':uid_from' => $user->uid,
    ':uid_to' => $new_user->uid,
  ));
  if (!user_access($perm) && !isset($_SESSION['masquerading']) && !$results->fetchField()) {
    watchdog('masquerade', 'This user requires administrative permissions to switch to the user %user.', array('%user' => $new_user->name), WATCHDOG_ERROR);
    return FALSE;
  }

  if ($user->uid == $uid || isset($user->masquerading)) {
    watchdog('masquerade', 'This user is already %user.', array('%user' => $new_user->name), WATCHDOG_ERROR);
    return FALSE;
  }

  if (state_get('maintenance_mode') && !user_access('access site in maintenance mode', $new_user)) {
    backdrop_set_message(t('It is not possible to masquerade in off-line mode as %user does not have the %config-perm permission. Please <a href="@site-maintenance">set the site status</a> to "online" to masquerade as %user.', array('%user' => $new_user->name, '%config-perm' => 'use the site in maintenance mode', '@site-maintenance' => url('admin/settings/site-maintenance'))));
    return FALSE;
  }

  // Call logout hooks when switching from original user.
  module_invoke_all('user_logout', $user);
  backdrop_session_regenerate();

  $query = db_insert('masquerade');
  $query->fields(array(
    'uid_from' => $user->uid,
    'uid_as' => $new_user->uid,
    'sid' => session_id(),
  ));
  $query->execute();
  // switch user

  watchdog('masquerade', 'User %user now masquerading as %masq_as.', array('%user' => $user->name, '%masq_as' => $new_user->name ? $new_user->name : t(config_get('system.core', 'anonymous'))), WATCHDOG_INFO);
  backdrop_set_message(t('You are now masquerading as !masq_as.', array('!masq_as' => theme('username', array('account' => $new_user)))));
  $user->masquerading = $new_user->uid;
  $user = $new_user;

  // Call all login hooks when switching to masquerading user.
  $edit = array(); // Passed by reference.
  user_module_invoke('login', $edit, $user);

  return TRUE;
}

/**
 * Allows a user who is currently masquerading to become a new user.
 */
function masquerade_switch_back_page() {
  if (isset($_GET['token']) && backdrop_valid_token($_GET['token'], 'masquerade/unswitch')) {
    global $user;
    $olduser = $user;
    masquerade_switch_back();
    backdrop_set_message(t('You are no longer masquerading as !masq_as and are now logged in as !user.', array('!user' => theme('username', array('account' => $user)), '!masq_as' => theme('username', array('account' => $olduser)))));
    backdrop_goto($_SERVER['HTTP_REFERER']);
  }
  else {
    backdrop_access_denied();
  }
}

/**
 * Function for a masquerading user to switch back to the previous user.
 */
function masquerade_switch_back() {
  $config = config('masquerade.settings');
  // switch user
  global $user;
  cache_clear_all($user->uid, 'cache_menu', TRUE);
  $uid = db_query("SELECT m.uid_from FROM {masquerade} m WHERE m.sid = :sid AND m.uid_as = :uid_as ", array(
    ':sid' => session_id(),
    ':uid_as' => $user->uid,
  ))->fetchField();
  // erase record
  db_delete('masquerade')
    ->condition('sid', session_id())
    ->condition('uid_as', $user->uid)
    ->execute();

  $oldname = ($user->uid == 0 ? t(config_get('system.core', 'anonymous')) : $user->name);

  // Call logout hooks when switching from masquerading user.
  module_invoke_all('user_logout', $user);
  backdrop_session_regenerate();

  $user = user_load($uid);

  // Call all login hooks when switching back to original user.
  $edit = array(); // Passed by reference.
  user_module_invoke('login', $edit, $user);

  watchdog('masquerade', 'User %user no longer masquerading as %masq_as.', array('%user' => $user->name, '%masq_as' => $oldname), WATCHDOG_INFO);
}