Adding upstream version 2.11.4.upstream/2.11.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

16 files changed, 4052 insertions, 0 deletions

diff --git a/library/Icinga/Authentication/AdmissionLoader.php b/library/Icinga/Authentication/AdmissionLoader.php
new file mode 100644
index 0000000..0c3fd3f
--- /dev/null
+++ b/library/Icinga/Authentication/AdmissionLoader.php
@@ -0,0 +1,249 @@
+<?php
+/* Icinga Web 2 | (c) 2014 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+use Generator;
+use Icinga\Application\Config;
+use Icinga\Application\Logger;
+use Icinga\Exception\ConfigurationError;
+use Icinga\Exception\NotReadableError;
+use Icinga\Data\ConfigObject;
+use Icinga\User;
+use Icinga\Util\StringHelper;
+
+/**
+ * Retrieve restrictions and permissions for users
+ */
+class AdmissionLoader
+{
+    const LEGACY_PERMISSIONS = [
+        'admin'                                 => 'application/announcements',
+        'application/stacktraces'               => 'user/application/stacktraces',
+        'application/share/navigation'          => 'user/share/navigation',
+        // Migrating config/application/* would include config/modules, so that's skipped
+        //'config/application/*'                  => 'config/*',
+        'config/application/general'            => 'config/general',
+        'config/application/resources'          => 'config/resources',
+        'config/application/navigation'         => 'config/navigation',
+        'config/application/userbackend'        => 'config/access-control/users',
+        'config/application/usergroupbackend'   => 'config/access-control/groups',
+        'config/authentication/*'               => 'config/access-control/*',
+        'config/authentication/users/*'         => 'config/access-control/users',
+        'config/authentication/users/show'      => 'config/access-control/users',
+        'config/authentication/users/add'       => 'config/access-control/users',
+        'config/authentication/users/edit'      => 'config/access-control/users',
+        'config/authentication/users/remove'    => 'config/access-control/users',
+        'config/authentication/groups/*'        => 'config/access-control/groups',
+        'config/authentication/groups/show'     => 'config/access-control/groups',
+        'config/authentication/groups/edit'     => 'config/access-control/groups',
+        'config/authentication/groups/add'      => 'config/access-control/groups',
+        'config/authentication/groups/remove'   => 'config/access-control/groups',
+        'config/authentication/roles/*'         => 'config/access-control/roles',
+        'config/authentication/roles/show'      => 'config/access-control/roles',
+        'config/authentication/roles/add'       => 'config/access-control/roles',
+        'config/authentication/roles/edit'      => 'config/access-control/roles',
+        'config/authentication/roles/remove'    => 'config/access-control/roles'
+    ];
+
+    /** @var Role[] */
+    protected $roles;
+
+    /** @var ConfigObject */
+    protected $roleConfig;
+
+    public function __construct()
+    {
+        try {
+            $this->roleConfig = Config::app('roles');
+        } catch (NotReadableError $e) {
+            Logger::error('Can\'t access roles configuration. An exception was thrown:', $e);
+        }
+    }
+
+    /**
+     * Whether the user or groups are a member of the role
+     *
+     * @param   string          $username
+     * @param   array           $userGroups
+     * @param   ConfigObject    $section
+     *
+     * @return  bool
+     */
+    protected function match($username, $userGroups, ConfigObject $section)
+    {
+        $username = strtolower($username);
+        if (! empty($section->users)) {
+            $users = array_map('strtolower', StringHelper::trimSplit($section->users));
+            if (in_array('*', $users)) {
+                return true;
+            }
+
+            if (in_array($username, $users)) {
+                return true;
+            }
+        }
+
+        if (! empty($section->groups)) {
+            $groups = array_map('strtolower', StringHelper::trimSplit($section->groups));
+            foreach ($userGroups as $userGroup) {
+                if (in_array(strtolower($userGroup), $groups)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Process role configuration and yield resulting roles
+     *
+     * This will also resolve any parent-child relationships.
+     *
+     * @param string $name
+     * @param ConfigObject $section
+     *
+     * @return Generator
+     * @throws ConfigurationError
+     */
+    protected function loadRole($name, ConfigObject $section)
+    {
+        if (! isset($this->roles[$name])) {
+            $permissions = $section->permissions ? StringHelper::trimSplit($section->permissions) : [];
+            $refusals = $section->refusals ? StringHelper::trimSplit($section->refusals) : [];
+
+            list($permissions, $newRefusals) = self::migrateLegacyPermissions($permissions);
+            if (! empty($newRefusals)) {
+                array_push($refusals, ...$newRefusals);
+            }
+
+            $restrictions = $section->toArray();
+            unset($restrictions['users'], $restrictions['groups']);
+            unset($restrictions['parent'], $restrictions['unrestricted']);
+            unset($restrictions['refusals'], $restrictions['permissions']);
+
+            $role = new Role();
+            $this->roles[$name] = $role
+                ->setName($name)
+                ->setRefusals($refusals)
+                ->setPermissions($permissions)
+                ->setRestrictions($restrictions)
+                ->setIsUnrestricted($section->get('unrestricted', false));
+
+            if (isset($section->parent)) {
+                $parentName = $section->parent;
+                if (! $this->roleConfig->hasSection($parentName)) {
+                    Logger::error(
+                        'Failed to parse authentication configuration: Missing parent role "%s" (required by "%s")',
+                        $parentName,
+                        $name
+                    );
+                    throw new ConfigurationError(
+                        t('Unable to parse authentication configuration. Check the log for more details.')
+                    );
+                }
+
+                foreach ($this->loadRole($parentName, $this->roleConfig->getSection($parentName)) as $parent) {
+                    if ($parent->getName() === $parentName) {
+                        $role->setParent($parent);
+                        $parent->addChild($role);
+
+                        // Only yield main role once fully assembled
+                        yield $role;
+                    }
+
+                    yield $parent;
+                }
+            } else {
+                yield $role;
+            }
+        } else {
+            yield $this->roles[$name];
+        }
+    }
+
+    /**
+     * Apply permissions, restrictions and roles to the given user
+     *
+     * @param   User    $user
+     */
+    public function applyRoles(User $user)
+    {
+        if ($this->roleConfig === null) {
+            return;
+        }
+
+        $username = $user->getUsername();
+        $userGroups = $user->getGroups();
+
+        $roles = [];
+        $permissions = [];
+        $restrictions = [];
+        $assignedRoles = [];
+        $isUnrestricted = false;
+        foreach ($this->roleConfig as $roleName => $roleConfig) {
+            $assigned = $this->match($username, $userGroups, $roleConfig);
+            if ($assigned) {
+                $assignedRoles[] = $roleName;
+            }
+
+            if (! isset($roles[$roleName]) && $assigned) {
+                foreach ($this->loadRole($roleName, $roleConfig) as $role) {
+                    /** @var Role $role */
+                    if (isset($roles[$role->getName()])) {
+                        continue;
+                    }
+
+                    $roles[$role->getName()] = $role;
+
+                    $permissions = array_merge(
+                        $permissions,
+                        array_diff($role->getPermissions(), $permissions)
+                    );
+
+                    $roleRestrictions = $role->getRestrictions();
+                    foreach ($roleRestrictions as $name => & $restriction) {
+                        $restriction = str_replace(
+                            '$user.local_name$',
+                            $user->getLocalUsername(),
+                            $restriction
+                        );
+                        $restrictions[$name][] = $restriction;
+                    }
+
+                    $role->setRestrictions($roleRestrictions);
+
+                    if (! $isUnrestricted) {
+                        $isUnrestricted = $role->isUnrestricted();
+                    }
+                }
+            }
+        }
+
+        $user->setAdditional('assigned_roles', $assignedRoles);
+
+        $user->setIsUnrestricted($isUnrestricted);
+        $user->setRestrictions($isUnrestricted ? [] : $restrictions);
+        $user->setPermissions($permissions);
+        $user->setRoles(array_values($roles));
+    }
+
+    public static function migrateLegacyPermissions(array $permissions)
+    {
+        $migratedGrants = [];
+        $refusals = [];
+
+        foreach ($permissions as $permission) {
+            if (array_key_exists($permission, self::LEGACY_PERMISSIONS)) {
+                $migratedGrants[] = self::LEGACY_PERMISSIONS[$permission];
+            } elseif ($permission === 'no-user/password-change') {
+                $refusals[] = 'user/password-change';
+            } else {
+                $migratedGrants[] = $permission;
+            }
+        }
+
+        return [$migratedGrants, $refusals];
+    }
+}
diff --git a/library/Icinga/Authentication/Auth.php b/library/Icinga/Authentication/Auth.php
new file mode 100644
index 0000000..f358eac
--- /dev/null
+++ b/library/Icinga/Authentication/Auth.php
@@ -0,0 +1,453 @@
+<?php
+/* Icinga Web 2 | (c) 2013 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+use Exception;
+use Icinga\Application\Config;
+use Icinga\Application\Hook\AuditHook;
+use Icinga\Application\Icinga;
+use Icinga\Application\Logger;
+use Icinga\Authentication\User\ExternalBackend;
+use Icinga\Authentication\UserGroup\UserGroupBackend;
+use Icinga\Data\ConfigObject;
+use Icinga\Exception\IcingaException;
+use Icinga\Exception\NotReadableError;
+use Icinga\User;
+use Icinga\User\Preferences;
+use Icinga\User\Preferences\PreferencesStore;
+use Icinga\Web\Session;
+use Icinga\Web\StyleSheet;
+
+class Auth
+{
+    /**
+     * Singleton instance
+     *
+     * @var self
+     */
+    private static $instance;
+
+    /**
+     * Request
+     *
+     * @var \Icinga\Web\Request
+     */
+    protected $request;
+
+    /**
+     * Response
+     *
+     * @var \Icinga\Web\Response
+     */
+    protected $response;
+
+    /**
+     * Authenticated user
+     *
+     * @var User|null
+     */
+    private $user;
+
+
+    /**
+     * @see getInstance()
+     */
+    private function __construct()
+    {
+    }
+
+    /**
+     * Get the authentication manager
+     *
+     * @return self
+     */
+    public static function getInstance()
+    {
+        if (self::$instance === null) {
+            self::$instance = new self();
+        }
+        return self::$instance;
+    }
+
+    /**
+     * Get the auth chain
+     *
+     * @return AuthChain
+     */
+    public function getAuthChain()
+    {
+        return new AuthChain();
+    }
+
+    /**
+     * Get whether the user is authenticated
+     *
+     * @return bool
+     */
+    public function isAuthenticated()
+    {
+        if ($this->user !== null) {
+            return true;
+        }
+        $this->authenticateFromSession();
+        if ($this->user === null && ! $this->authExternal()) {
+            return false;
+        }
+        return true;
+    }
+
+    public function setAuthenticated(User $user, $persist = true)
+    {
+        $this->setupUser($user);
+
+        // Reload CSS if the theme changed
+        $themingConfig = Icinga::app()->getConfig()->getSection('themes');
+        $userTheme = $user->getPreferences()->getValue('icingaweb', 'theme');
+        if (! (bool) $themingConfig->get('disabled', false) && $userTheme !== null) {
+            $defaultTheme = $themingConfig->get('default', StyleSheet::DEFAULT_THEME);
+            if ($userTheme !== $defaultTheme) {
+                $this->getResponse()->setReloadCss(true);
+            }
+        }
+
+        // Also reload CSS if the theme mode changed
+        $themeMode = $user->getPreferences()->getValue('icingaweb', 'theme_mode');
+        if ($themeMode && $themeMode !== StyleSheet::DEFAULT_MODE) {
+            $this->getResponse()->setReloadCss(true);
+        }
+
+        // Reload entire layout if the locale changed
+        if (($locale = $user->getPreferences()->getValue('icingaweb', 'language')) !== null) {
+            if (setlocale(LC_ALL, 0) !== $locale && $this->getRequest()->isXmlHttpRequest()) {
+                $this->getResponse()->setHeader('X-Icinga-Redirect-Http', 'yes');
+            }
+        }
+
+        $this->user = $user;
+        if ($persist) {
+            $this->persistCurrentUser();
+        }
+
+        AuditHook::logActivity('login', 'User logged in');
+    }
+
+    /**
+     * Getter for groups belonged to authenticated user
+     *
+     * @return  array
+     * @see     User::getGroups
+     */
+    public function getGroups()
+    {
+        return $this->user->getGroups();
+    }
+
+    /**
+     * Get the request
+     *
+     * @return \Icinga\Web\Request
+     */
+    public function getRequest()
+    {
+        if ($this->request === null) {
+            $this->request = Icinga::app()->getRequest();
+        }
+        return $this->request;
+    }
+
+    /**
+     * Get the response
+     *
+     * @return \Icinga\Web\Response
+     */
+    public function getResponse()
+    {
+        if ($this->response === null) {
+            $this->response = Icinga::app()->getResponse();
+        }
+        return $this->response;
+    }
+
+    /**
+     * Get applied restrictions matching a given restriction name
+     *
+     * Returns a list of applied restrictions, empty if no user is
+     * authenticated
+     *
+     * @param  string  $restriction  Restriction name
+     * @return array
+     */
+    public function getRestrictions($restriction)
+    {
+        if (! $this->isAuthenticated()) {
+            return array();
+        }
+        return $this->user->getRestrictions($restriction);
+    }
+
+    /**
+     * Returns the current user or null if no user is authenticated
+     *
+     * @return User|null
+     */
+    public function getUser()
+    {
+        return $this->user;
+    }
+
+    /**
+     * Set the authenticated user
+     *
+     * Note that this method just sets the authenticated user and thus bypasses our default authentication process in
+     * {@link setAuthenticated()}.
+     *
+     * @param User $user
+     *
+     * @return $this
+     */
+    public function setUser(User $user)
+    {
+        $this->user = $user;
+
+        return $this;
+    }
+
+    /**
+     * Try to authenticate the user with the current session
+     *
+     * Authentication for externally-authenticated users will be revoked if the username changed or external
+     * authentication is no longer in effect
+     */
+    public function authenticateFromSession()
+    {
+        $this->user = Session::getSession()->get('user');
+        if ($this->user !== null && $this->user->isExternalUser()) {
+            list($originUsername, $field) = $this->user->getExternalUserInformation();
+            $username = ExternalBackend::getRemoteUser($field);
+            if ($username === null || $username !== $originUsername) {
+                $this->removeAuthorization();
+            }
+        }
+    }
+
+    /**
+     * Attempt to authenticate a user from external user backends
+     *
+     * @return bool
+     */
+    protected function authExternal()
+    {
+        $user = new User('');
+        foreach ($this->getAuthChain() as $userBackend) {
+            if ($userBackend instanceof ExternalBackend) {
+                if ($userBackend->authenticate($user)) {
+                    if (! $user->hasDomain()) {
+                        $user->setDomain(Config::app()->get('authentication', 'default_domain'));
+                    }
+                    $this->setAuthenticated($user);
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Attempt to authenticate a user using HTTP authentication on API requests only
+     *
+     * Supports only the Basic HTTP authentication scheme. XHR will be ignored.
+     *
+     * @return bool
+     */
+    public function authHttp()
+    {
+        $request = $this->getRequest();
+        $header = $request->getHeader('Authorization');
+        if (empty($header)) {
+            return false;
+        }
+        list($scheme) = explode(' ', $header, 2);
+        if ($scheme !== 'Basic') {
+            return false;
+        }
+        $authorization = substr($header, strlen('Basic '));
+        $credentials = base64_decode($authorization);
+        $credentials = array_filter(explode(':', $credentials, 2));
+        if (count($credentials) !== 2) {
+            // Deny empty username and/or password
+            return false;
+        }
+        $user = new User($credentials[0]);
+        if (! $user->hasDomain()) {
+            $user->setDomain(Config::app()->get('authentication', 'default_domain'));
+        }
+        $password = $credentials[1];
+        if ($this->getAuthChain()->setSkipExternalBackends(true)->authenticate($user, $password)) {
+            $this->setAuthenticated($user, false);
+            $user->setIsHttpUser(true);
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /**
+     * Challenge client immediately for HTTP authentication
+     *
+     * Sends the response w/ the 401 Unauthorized status code and WWW-Authenticate header.
+     */
+    public function challengeHttp()
+    {
+        $response = $this->getResponse();
+        $response->setHttpResponseCode(401);
+        $response->setHeader('WWW-Authenticate', 'Basic realm="Icinga Web 2"');
+        $response->sendHeaders();
+        exit();
+    }
+
+    /**
+     * Whether an authenticated user has a given permission
+     *
+     * @param  string  $permission  Permission name
+     *
+     * @return bool                 True if the user owns the given permission, false if not or if not authenticated
+     */
+    public function hasPermission($permission)
+    {
+        if (! $this->isAuthenticated()) {
+            return false;
+        }
+        return $this->user->can($permission);
+    }
+
+    /**
+     * Writes the current user to the session
+     */
+    public function persistCurrentUser()
+    {
+        // @TODO(el): https://dev.icinga.com/issues/10646
+        $params = session_get_cookie_params();
+        setcookie(
+            'icingaweb2-session',
+            time(),
+            0,
+            $params['path'],
+            $params['domain'],
+            $params['secure'],
+            $params['httponly']
+        );
+        Session::getSession()->set('user', $this->user)->refreshId();
+    }
+
+    /**
+     * Purges the current authorization information and session
+     */
+    public function removeAuthorization()
+    {
+        AuditHook::logActivity('logout', 'User logged out');
+        $this->user = null;
+        Session::getSession()->purge();
+    }
+
+    /**
+     * Setup the given user
+     *
+     * This loads preferences, groups and roles.
+     *
+     * @param User $user
+     *
+     * @return void
+     */
+    public function setupUser(User $user)
+    {
+        // Load the user's preferences
+
+        try {
+            $config = Config::app();
+        } catch (NotReadableError $e) {
+            Logger::error(
+                new IcingaException(
+                    'Cannot load preferences for user "%s". An exception was thrown: %s',
+                    $user->getUsername(),
+                    $e
+                )
+            );
+            $config = new Config();
+        }
+
+        $preferencesConfig = new ConfigObject([
+            'resource'  => $config->get('global', 'config_resource')
+        ]);
+
+        try {
+            $preferencesStore = PreferencesStore::create($preferencesConfig, $user);
+            $preferences = new Preferences($preferencesStore->load());
+        } catch (Exception $e) {
+            Logger::error(
+                new IcingaException(
+                    'Cannot load preferences for user "%s". An exception was thrown: %s',
+                    $user->getUsername(),
+                    $e
+                )
+            );
+            $preferences = new Preferences();
+        }
+
+        $user->setPreferences($preferences);
+
+        // Load the user's groups
+        $groups = $user->getGroups();
+        $userBackendName = $user->getAdditional('backend_name');
+        foreach (Config::app('groups') as $name => $config) {
+            $groupsUserBackend = $config->user_backend;
+            if ($groupsUserBackend
+                && $groupsUserBackend !== 'none'
+                && $userBackendName !== null
+                && $groupsUserBackend !== $userBackendName
+            ) {
+                // Do not ask for Group membership if a specific User Backend
+                // has been assigned to that Group Backend, and the user has
+                // been authenticated by another User Backend
+                continue;
+            }
+
+            try {
+                $groupBackend = UserGroupBackend::create($name, $config);
+                $groupsFromBackend = $groupBackend->getMemberships($user);
+            } catch (Exception $e) {
+                Logger::error(
+                    'Can\'t get group memberships for user \'%s\' from backend \'%s\'. An exception was thrown: %s',
+                    $user->getUsername(),
+                    $name,
+                    $e
+                );
+                continue;
+            }
+
+            if (empty($groupsFromBackend)) {
+                Logger::debug(
+                    'No groups found in backend "%s" which the user "%s" is a member of.',
+                    $name,
+                    $user->getUsername()
+                );
+                continue;
+            }
+
+            $groupsFromBackend = array_values($groupsFromBackend);
+            Logger::debug(
+                'Groups found in backend "%s" for user "%s": %s',
+                $name,
+                $user->getUsername(),
+                join(', ', $groupsFromBackend)
+            );
+            $groups = array_merge($groups, array_combine($groupsFromBackend, $groupsFromBackend));
+        }
+
+        $user->setGroups($groups);
+
+        // Load the user's roles
+        $admissionLoader = new AdmissionLoader();
+        $admissionLoader->applyRoles($user);
+    }
+}
diff --git a/library/Icinga/Authentication/AuthChain.php b/library/Icinga/Authentication/AuthChain.php
new file mode 100644
index 0000000..39468e3
--- /dev/null
+++ b/library/Icinga/Authentication/AuthChain.php
@@ -0,0 +1,269 @@
+<?php
+/* Icinga Web 2 | (c) 2014 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+use Icinga\Application\Hook\AuditHook;
+use Iterator;
+use Icinga\Application\Config;
+use Icinga\Application\Logger;
+use Icinga\Authentication\User\ExternalBackend;
+use Icinga\Authentication\User\UserBackend;
+use Icinga\Authentication\User\UserBackendInterface;
+use Icinga\Data\ConfigObject;
+use Icinga\Exception\AuthenticationException;
+use Icinga\Exception\ConfigurationError;
+use Icinga\Exception\NotReadableError;
+use Icinga\User;
+
+/**
+ * Iterate user backends created from config
+ */
+class AuthChain implements Authenticatable, Iterator
+{
+    /**
+     * Authentication config file
+     *
+     * @var string
+     */
+    const AUTHENTICATION_CONFIG = 'authentication';
+
+    /**
+     * Error code if the authentication configuration was not readable
+     *
+     * @var int
+     */
+    const EPERM = 1;
+
+    /**
+     * Error code if the authentication configuration is empty
+     */
+    const EEMPTY = 2;
+
+    /**
+     * Error code if all authentication methods failed
+     *
+     * @var int
+     */
+    const EFAIL = 3;
+
+    /**
+     * Error code if not all authentication methods were available
+     *
+     * @var int
+     */
+    const ENOTALL = 4;
+
+    /**
+     * User backends configuration
+     *
+     * @var Config
+     */
+    protected $config;
+
+    /**
+     * The consecutive user backend while looping
+     *
+     * @var UserBackendInterface
+     */
+    protected $currentBackend;
+
+    /**
+     * Last error code
+     *
+     * @var int|null
+     */
+    protected $error;
+
+    /**
+     * Whether external user backends should be skipped on iteration
+     *
+     * @var bool
+     */
+    protected $skipExternalBackends = false;
+
+    /**
+     * Create a new authentication chain from config
+     *
+     * @param Config $config User backends configuration
+     */
+    public function __construct(Config $config = null)
+    {
+        if ($config === null) {
+            try {
+                $this->config = Config::app(static::AUTHENTICATION_CONFIG);
+            } catch (NotReadableError $e) {
+                $this->config = new Config();
+                $this->error = static::EPERM;
+            }
+        } else {
+            $this->config = $config;
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function authenticate(User $user, $password)
+    {
+        $this->error = null;
+        $backendsTried = 0;
+        $backendsWithError = 0;
+        foreach ($this as $backend) {
+            ++$backendsTried;
+            try {
+                $authenticated = $backend->authenticate($user, $password);
+            } catch (AuthenticationException $e) {
+                Logger::error($e);
+                ++$backendsWithError;
+                continue;
+            }
+            if ($authenticated) {
+                $user->setAdditional('backend_name', $backend->getName());
+                $user->setAdditional('backend_type', $this->config->current()->get('backend'));
+                return true;
+            }
+        }
+
+        if ($backendsTried === 0) {
+            $this->error = static::EEMPTY;
+        } elseif ($backendsTried === $backendsWithError) {
+            $this->error = static::EFAIL;
+        } elseif ($backendsWithError) {
+            $this->error = static::ENOTALL;
+        } else {
+            AuditHook::logActivity('login-failed', 'User failed to authenticate', null, $user->getUsername());
+        }
+
+        return false;
+    }
+
+    /**
+     * Get the last error code
+     *
+     * @return int|null
+     */
+    public function getError()
+    {
+        return $this->error;
+    }
+
+    /**
+     * Whether authentication had errors
+     *
+     * @return bool
+     */
+    public function hasError()
+    {
+        return $this->error !== null;
+    }
+
+    /**
+     * Get whether to skip external user backends on iteration
+     *
+     * @return bool
+     */
+    public function getSkipExternalBackends()
+    {
+        return $this->skipExternalBackends;
+    }
+
+    /**
+     * Set whether to skip external user backends on iteration
+     *
+     * @param   bool $skipExternalBackends
+     *
+     * @return  $this
+     */
+    public function setSkipExternalBackends($skipExternalBackends = true)
+    {
+        $this->skipExternalBackends = (bool) $skipExternalBackends;
+        return $this;
+    }
+
+    /**
+     * Rewind the chain
+     *
+     * @return void
+     */
+    public function rewind(): void
+    {
+        $this->currentBackend = null;
+        $this->config->rewind();
+    }
+
+    /**
+     * Get the current user backend
+     *
+     * @return UserBackendInterface
+     */
+    public function current(): UserBackendInterface
+    {
+        return $this->currentBackend;
+    }
+
+    /**
+     * Get the key of the current user backend config
+     *
+     * @return string
+     */
+    public function key(): string
+    {
+        return $this->config->key();
+    }
+
+    /**
+     * Move forward to the next user backend config
+     *
+     * @return void
+     */
+    public function next(): void
+    {
+        $this->config->next();
+    }
+
+    /**
+     * Check whether the current user backend is valid, i.e. it's enabled, not an external user backend and whether its
+     * config is valid
+     *
+     * @return bool
+     */
+    public function valid(): bool
+    {
+        if (! $this->config->valid()) {
+            // Stop when there are no more backends to check
+            return false;
+        }
+
+        $backendConfig = $this->config->current();
+        if ((bool) $backendConfig->get('disabled', false)) {
+            $this->next();
+            return $this->valid();
+        }
+
+        $name = $this->key();
+        try {
+            $backend = UserBackend::create($name, $backendConfig);
+        } catch (ConfigurationError $e) {
+            Logger::error(
+                new ConfigurationError(
+                    'Can\'t create authentication backend "%s". An exception was thrown:',
+                    $name,
+                    $e
+                )
+            );
+            $this->next();
+            return $this->valid();
+        }
+
+        if ($this->getSkipExternalBackends()
+            && $backend instanceof ExternalBackend
+        ) {
+            $this->next();
+            return $this->valid();
+        }
+
+        $this->currentBackend = $backend;
+        return true;
+    }
+}
diff --git a/library/Icinga/Authentication/Authenticatable.php b/library/Icinga/Authentication/Authenticatable.php
new file mode 100644
index 0000000..c10d6d3
--- /dev/null
+++ b/library/Icinga/Authentication/Authenticatable.php
@@ -0,0 +1,21 @@
+<?php
+/* Icinga Web 2 | (c) 2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+use Icinga\User;
+
+interface Authenticatable
+{
+    /**
+     * Authenticate a user
+     *
+     * @param   User    $user
+     * @param   string  $password
+     *
+     * @return  bool
+     *
+     * @throws  \Icinga\Exception\AuthenticationException If authentication errors
+     */
+    public function authenticate(User $user, $password);
+}
diff --git a/library/Icinga/Authentication/Role.php b/library/Icinga/Authentication/Role.php
new file mode 100644
index 0000000..c409ba4
--- /dev/null
+++ b/library/Icinga/Authentication/Role.php
@@ -0,0 +1,334 @@
+<?php
+/* Icinga Web 2 | (c) 2016 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+class Role
+{
+    /**
+     * Name of the role
+     *
+     * @var string
+     */
+    protected $name;
+
+    /**
+     * The role from which to inherit privileges
+     *
+     * @var Role
+     */
+    protected $parent;
+
+    /**
+     * The roles to which privileges are inherited
+     *
+     * @var Role[]
+     */
+    protected $children;
+
+    /**
+     * Whether restrictions should not apply to owners of the role
+     *
+     * @var bool
+     */
+    protected $unrestricted = false;
+
+    /**
+     * Permissions of the role
+     *
+     * @var string[]
+     */
+    protected $permissions = [];
+
+    /**
+     * Refusals of the role
+     *
+     * @var string[]
+     */
+    protected $refusals = [];
+
+    /**
+     * Restrictions of the role
+     *
+     * @var string[]
+     */
+    protected $restrictions = [];
+
+    /**
+     * Get the name of the role
+     *
+     * @return  string
+     */
+    public function getName()
+    {
+        return $this->name;
+    }
+
+    /**
+     * Set the name of the role
+     *
+     * @param   string  $name
+     *
+     * @return  $this
+     */
+    public function setName($name)
+    {
+        $this->name = $name;
+
+        return $this;
+    }
+
+    /**
+     * Get the role from which privileges are inherited
+     *
+     * @return Role
+     */
+    public function getParent()
+    {
+        return $this->parent;
+    }
+
+    /**
+     * Set the role from which to inherit privileges
+     *
+     * @param Role $parent
+     *
+     * @return $this
+     */
+    public function setParent(Role $parent)
+    {
+        $this->parent = $parent;
+
+        return $this;
+    }
+
+    /**
+     * Get the roles to which privileges are inherited
+     *
+     * @return Role[]
+     */
+    public function getChildren()
+    {
+        return $this->children;
+    }
+
+    /**
+     * Set the roles to which inherit privileges
+     *
+     * @param Role[] $children
+     *
+     * @return $this
+     */
+    public function setChildren(array $children)
+    {
+        $this->children = $children;
+
+        return $this;
+    }
+
+    /**
+     * Add a role to which inherit privileges
+     *
+     * @param Role $role
+     *
+     * @return $this
+     */
+    public function addChild(Role $role)
+    {
+        $this->children[] = $role;
+
+        return $this;
+    }
+
+    /**
+     * Get whether restrictions should not apply to owners of the role
+     *
+     * @return bool
+     */
+    public function isUnrestricted()
+    {
+        return $this->unrestricted;
+    }
+
+    /**
+     * Set whether restrictions should not apply to owners of the role
+     *
+     * @param bool $state
+     *
+     * @return $this
+     */
+    public function setIsUnrestricted($state)
+    {
+        $this->unrestricted = (bool) $state;
+
+        return $this;
+    }
+
+    /**
+     * Get the permissions of the role
+     *
+     * @return  string[]
+     */
+    public function getPermissions()
+    {
+        return $this->permissions;
+    }
+
+    /**
+     * Set the permissions of the role
+     *
+     * @param   string[]    $permissions
+     *
+     * @return  $this
+     */
+    public function setPermissions(array $permissions)
+    {
+        $this->permissions = $permissions;
+
+        return $this;
+    }
+
+    /**
+     * Get the refusals of the role
+     *
+     * @return string[]
+     */
+    public function getRefusals()
+    {
+        return $this->refusals;
+    }
+
+    /**
+     * Set the refusals of the role
+     *
+     * @param array $refusals
+     *
+     * @return $this
+     */
+    public function setRefusals(array $refusals)
+    {
+        $this->refusals = $refusals;
+
+        return $this;
+    }
+
+    /**
+     * Get the restrictions of the role
+     *
+     * @param   string  $name   Optional name of the restriction
+     *
+     * @return  string[]|null
+     */
+    public function getRestrictions($name = null)
+    {
+        $restrictions = $this->restrictions;
+
+        if ($name === null) {
+            return $restrictions;
+        }
+
+        if (isset($restrictions[$name])) {
+            return $restrictions[$name];
+        }
+
+        return null;
+    }
+
+    /**
+     * Set the restrictions of the role
+     *
+     * @param   string[]    $restrictions
+     *
+     * @return  $this
+     */
+    public function setRestrictions(array $restrictions)
+    {
+        $this->restrictions = $restrictions;
+
+        return $this;
+    }
+
+    /**
+     * Whether this role grants the given permission
+     *
+     * @param string $permission
+     * @param bool $ignoreParent    Only evaluate the role's own permissions
+     * @param bool $cascadeUpwards  `false` if `foo/bar/*` and `foo/bar/raboof` should not match `foo/*`
+     *
+     * @return bool
+     */
+    public function grants($permission, $ignoreParent = false, $cascadeUpwards = true)
+    {
+        foreach ($this->permissions as $grantedPermission) {
+            if ($this->match($grantedPermission, $permission, $cascadeUpwards)) {
+                return true;
+            }
+        }
+
+        if (! $ignoreParent && $this->getParent() !== null) {
+            return $this->getParent()->grants($permission, false, $cascadeUpwards);
+        }
+
+        return false;
+    }
+
+    /**
+     * Whether this role denies the given permission
+     *
+     * @param string $permission
+     * @param bool $ignoreParent    Only evaluate the role's own refusals
+     *
+     * @return bool
+     */
+    public function denies($permission, $ignoreParent = false)
+    {
+        foreach ($this->refusals as $refusedPermission) {
+            if ($this->match($refusedPermission, $permission, false)) {
+                return true;
+            }
+        }
+
+        if (! $ignoreParent && $this->getParent() !== null) {
+            return $this->getParent()->denies($permission);
+        }
+
+        return false;
+    }
+
+    /**
+     * Get whether the role expression matches the required permission
+     *
+     * @param string $roleExpression
+     * @param string $requiredPermission
+     * @param bool $cascadeUpwards `false` if `foo/bar/*` and `foo/bar/raboof` should not match `foo/*`
+     *
+     * @return bool
+     */
+    protected function match($roleExpression, $requiredPermission, $cascadeUpwards = true)
+    {
+        if ($roleExpression === '*' || $roleExpression === $requiredPermission) {
+            return true;
+        }
+
+        $requiredWildcard = strpos($requiredPermission, '*');
+        if ($requiredWildcard !== false) {
+            if (($grantedWildcard = strpos($roleExpression, '*')) !== false) {
+                $wildcard = $cascadeUpwards ? min($requiredWildcard, $grantedWildcard) : $grantedWildcard;
+            } else {
+                $wildcard = $cascadeUpwards ? $requiredWildcard : false;
+            }
+        } else {
+            $wildcard = strpos($roleExpression, '*');
+        }
+
+        if ($wildcard !== false && $wildcard > 0) {
+            if (substr($requiredPermission, 0, $wildcard) === substr($roleExpression, 0, $wildcard)) {
+                return true;
+            }
+        } elseif ($requiredPermission === $roleExpression) {
+            return true;
+        }
+
+        return false;
+    }
+}
diff --git a/library/Icinga/Authentication/RolesConfig.php b/library/Icinga/Authentication/RolesConfig.php
new file mode 100644
index 0000000..ac5695f
--- /dev/null
+++ b/library/Icinga/Authentication/RolesConfig.php
@@ -0,0 +1,43 @@
+<?php
+/* Icinga Web 2 | (c) 2019 Icinga GmbH | GPLv2+ */
+
+namespace Icinga\Authentication;
+
+use Icinga\Application\Icinga;
+use Icinga\Repository\IniRepository;
+
+class RolesConfig extends IniRepository
+{
+    protected $configs = [
+        'roles' => [
+            'name'      => 'roles',
+            'keyColumn' => 'name'
+        ]
+    ];
+
+    protected function initializeQueryColumns()
+    {
+        $columns = [
+            'roles' => [
+                'parent',
+                'name',
+                'users',
+                'groups',
+                'refusals',
+                'permissions',
+                'unrestricted',
+                'application/share/users',
+                'application/share/groups'
+            ]
+        ];
+
+        $moduleManager = Icinga::app()->getModuleManager();
+        foreach ($moduleManager->listInstalledModules() as $moduleName) {
+            foreach ($moduleManager->getModule($moduleName, false)->getProvidedRestrictions() as $restriction) {
+                $columns['roles'][] = $restriction->name;
+            }
+        }
+
+        return $columns;
+    }
+}
diff --git a/library/Icinga/Authentication/User/DbUserBackend.php b/library/Icinga/Authentication/User/DbUserBackend.php
new file mode 100644
index 0000000..0e8cc6a
--- /dev/null
+++ b/library/Icinga/Authentication/User/DbUserBackend.php
@@ -0,0 +1,256 @@
+<?php
+/* Icinga Web 2 | (c) 2013 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+use Exception;
+use Icinga\Data\Inspectable;
+use Icinga\Data\Inspection;
+use Icinga\Data\Filter\Filter;
+use Icinga\Exception\AuthenticationException;
+use Icinga\Repository\DbRepository;
+use Icinga\User;
+use PDO;
+
+class DbUserBackend extends DbRepository implements UserBackendInterface, Inspectable
+{
+    /**
+     * The query columns being provided
+     *
+     * @var array
+     */
+    protected $queryColumns = array(
+        'user' => array(
+            'user'          => 'name COLLATE utf8mb4_general_ci',
+            'user_name'     => 'name',
+            'is_active'     => 'active',
+            'created_at'    => 'UNIX_TIMESTAMP(ctime)',
+            'last_modified' => 'UNIX_TIMESTAMP(mtime)'
+        )
+    );
+
+    /**
+     * The statement columns being provided
+     *
+     * @var array
+     */
+    protected $statementColumns = array(
+        'user' => array(
+            'password'      => 'password_hash',
+            'created_at'    => 'ctime',
+            'last_modified' => 'mtime'
+        )
+    );
+
+    /**
+     * The columns which are not permitted to be queried
+     *
+     * @var array
+     */
+    protected $blacklistedQueryColumns = array('user');
+
+    /**
+     * The search columns being provided
+     *
+     * @var array
+     */
+    protected $searchColumns = array('user');
+
+    /**
+     * The default sort rules to be applied on a query
+     *
+     * @var array
+     */
+    protected $sortRules = array(
+        'user_name' => array(
+            'columns'   => array(
+                'is_active desc',
+                'user_name'
+            )
+        )
+    );
+
+    /**
+     * The value conversion rules to apply on a query or statement
+     *
+     * @var array
+     */
+    protected $conversionRules = array(
+        'user' => array(
+            'password'
+        )
+    );
+
+    /**
+     * Initialize this database user backend
+     */
+    protected function init()
+    {
+        if (! $this->ds->getTablePrefix()) {
+            $this->ds->setTablePrefix('icingaweb_');
+        }
+    }
+
+    /**
+     * Initialize this repository's filter columns
+     *
+     * @return  array
+     */
+    protected function initializeFilterColumns()
+    {
+        $userLabel = t('Username') . ' ' . t('(Case insensitive)');
+        return array(
+            $userLabel          => 'user',
+            t('Username')       => 'user_name',
+            t('Active')         => 'is_active',
+            t('Created at')     => 'created_at',
+            t('Last modified')  => 'last_modified'
+        );
+    }
+
+    /**
+     * Insert a table row with the given data
+     *
+     * @param   string $table
+     * @param   array  $bind
+     *
+     * @return void
+     */
+    public function insert($table, array $bind, array $types = array())
+    {
+        $this->requireTable($table);
+        $bind['created_at'] = date('Y-m-d H:i:s');
+        $this->ds->insert(
+            $this->prependTablePrefix($table),
+            $this->requireStatementColumns($table, $bind),
+            array(
+                'active'        => PDO::PARAM_INT,
+                'password_hash' => PDO::PARAM_LOB
+            )
+        );
+    }
+
+    /**
+     * Update table rows with the given data, optionally limited by using a filter
+     *
+     * @param   string  $table
+     * @param   array   $bind
+     * @param   Filter  $filter
+     */
+    public function update($table, array $bind, Filter $filter = null, array $types = array())
+    {
+        $this->requireTable($table);
+        $bind['last_modified'] = date('Y-m-d H:i:s');
+        if ($filter) {
+            $filter = $this->requireFilter($table, $filter);
+        }
+
+        $this->ds->update(
+            $this->prependTablePrefix($table),
+            $this->requireStatementColumns($table, $bind),
+            $filter,
+            array(
+                'active'        => PDO::PARAM_INT,
+                'password_hash' => PDO::PARAM_LOB
+            )
+        );
+    }
+
+    /**
+     * Hash and return the given password
+     *
+     * @param   string  $value
+     *
+     * @return  string
+     */
+    protected function persistPassword($value)
+    {
+        return password_hash($value, PASSWORD_DEFAULT);
+    }
+
+    /**
+     * Fetch the hashed password for the given user
+     *
+     * @param   string  $username   The name of the user
+     *
+     * @return  string
+     */
+    protected function getPasswordHash($username)
+    {
+        if ($this->ds->getDbType() === 'pgsql') {
+            // Since PostgreSQL version 9.0 the default value for bytea_output is 'hex' instead of 'escape'
+            $columns = array('password_hash' => 'ENCODE(password_hash, \'escape\')');
+        } else {
+            $columns = array('password_hash');
+        }
+
+        $nameColumn = 'name';
+        if ($this->ds->getDbType() === 'mysql') {
+            $username = strtolower($username);
+            $nameColumn = 'BINARY LOWER(name)';
+        }
+
+        $query = $this->ds->select()
+            ->from($this->prependTablePrefix('user'), $columns)
+            ->where($nameColumn, $username)
+            ->where('active', true);
+
+        $statement = $this->ds->getDbAdapter()->prepare($query->getSelectQuery());
+        $statement->execute();
+        $statement->bindColumn(1, $lob, PDO::PARAM_LOB);
+        $statement->fetch(PDO::FETCH_BOUND);
+        if (is_resource($lob)) {
+            $lob = stream_get_contents($lob);
+        }
+
+        if ($lob === null) {
+            return '';
+        }
+
+        return $this->ds->getDbType() === 'pgsql' ? pg_unescape_bytea($lob) : $lob;
+    }
+
+    /**
+     * Authenticate the given user
+     *
+     * @param   User        $user
+     * @param   string      $password
+     *
+     * @return  bool                        True on success, false on failure
+     *
+     * @throws  AuthenticationException     In case authentication is not possible due to an error
+     */
+    public function authenticate(User $user, $password)
+    {
+        try {
+            return password_verify(
+                $password,
+                $this->getPasswordHash($user->getUsername())
+            );
+        } catch (Exception $e) {
+            throw new AuthenticationException(
+                'Failed to authenticate user "%s" against backend "%s". An exception was thrown:',
+                $user->getUsername(),
+                $this->getName(),
+                $e
+            );
+        }
+    }
+
+    /**
+     * Inspect this object to gain extended information about its health
+     *
+     * @return Inspection           The inspection result
+     */
+    public function inspect()
+    {
+        $insp = new Inspection('Db User Backend');
+        $insp->write($this->ds->inspect());
+        try {
+            $insp->write(sprintf('%s active users', $this->select()->where('is_active', true)->count()));
+        } catch (Exception $e) {
+            $insp->error(sprintf('Query failed: %s', $e->getMessage()));
+        }
+        return $insp;
+    }
+}
diff --git a/library/Icinga/Authentication/User/DomainAwareInterface.php b/library/Icinga/Authentication/User/DomainAwareInterface.php
new file mode 100644
index 0000000..3ff9c31
--- /dev/null
+++ b/library/Icinga/Authentication/User/DomainAwareInterface.php
@@ -0,0 +1,17 @@
+<?php
+/* Icinga Web 2 | (c) 2017 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+/**
+ * Interface for user backends that are responsible for a specific domain
+ */
+interface DomainAwareInterface
+{
+    /**
+     * Get the domain the backend is responsible for
+     *
+     * @return  string
+     */
+    public function getDomain();
+}
diff --git a/library/Icinga/Authentication/User/ExternalBackend.php b/library/Icinga/Authentication/User/ExternalBackend.php
new file mode 100644
index 0000000..6e79928
--- /dev/null
+++ b/library/Icinga/Authentication/User/ExternalBackend.php
@@ -0,0 +1,124 @@
+<?php
+/* Icinga Web 2 | (c) 2014 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+use Icinga\Application\Logger;
+use Icinga\Data\ConfigObject;
+use Icinga\User;
+
+/**
+ * Test login with external authentication mechanism, e.g. Apache
+ */
+class ExternalBackend implements UserBackendInterface
+{
+    /**
+     * Possible variables where to read the user from
+     *
+     * @var string[]
+     */
+    public static $remoteUserEnvvars = array('REMOTE_USER', 'REDIRECT_REMOTE_USER');
+
+    /**
+     * The name of this backend
+     *
+     * @var string
+     */
+    protected $name;
+
+    /**
+     * Regexp expression to strip values from a username
+     *
+     * @var string
+     */
+    protected $stripUsernameRegexp;
+
+    /**
+     * Create new authentication backend of type "external"
+     *
+     * @param ConfigObject $config
+     */
+    public function __construct(ConfigObject $config)
+    {
+        $this->stripUsernameRegexp = $config->get('strip_username_regexp');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getName()
+    {
+        return $this->name;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setName($name)
+    {
+        $this->name = $name;
+        return $this;
+    }
+
+    /**
+     * Get the remote user from environment or $_SERVER, if any
+     *
+     * @param   string  $variable   The name of the variable where to read the user from
+     *
+     * @return  string|null
+     */
+    public static function getRemoteUser($variable = 'REMOTE_USER')
+    {
+        $username = getenv($variable);
+        if (! empty($username)) {
+            return $username;
+        }
+
+        if (array_key_exists($variable, $_SERVER) && ! empty($_SERVER[$variable])) {
+            return $_SERVER[$variable];
+        }
+    }
+
+    /**
+     * Get the remote user information from environment or $_SERVER, if any
+     *
+     * @return  array   Contains always two entries, the username and origin which may both set to null.
+     */
+    public static function getRemoteUserInformation()
+    {
+        foreach (static::$remoteUserEnvvars as $envVar) {
+            $username = static::getRemoteUser($envVar);
+            if ($username !== null) {
+                return array($username, $envVar);
+            }
+        }
+
+        return array(null, null);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function authenticate(User $user, $password = null)
+    {
+        list($username, $field) = static::getRemoteUserInformation();
+        if ($username !== null) {
+            $user->setExternalUserInformation($username, $field);
+
+            if ($this->stripUsernameRegexp) {
+                $stripped = @preg_replace($this->stripUsernameRegexp, '', $username);
+                if ($stripped === false) {
+                    Logger::error('Failed to strip external username. The configured regular expression is invalid.');
+                    return false;
+                }
+
+                $username = $stripped;
+            }
+
+            $user->setUsername($username);
+            return true;
+        }
+
+        return false;
+    }
+}
diff --git a/library/Icinga/Authentication/User/LdapUserBackend.php b/library/Icinga/Authentication/User/LdapUserBackend.php
new file mode 100644
index 0000000..8c8a230
--- /dev/null
+++ b/library/Icinga/Authentication/User/LdapUserBackend.php
@@ -0,0 +1,477 @@
+<?php
+/* Icinga Web 2 | (c) 2013 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+use DateTime;
+use Icinga\Data\ConfigObject;
+use Icinga\Data\Inspectable;
+use Icinga\Data\Inspection;
+use Icinga\Exception\AuthenticationException;
+use Icinga\Exception\ProgrammingError;
+use Icinga\Repository\LdapRepository;
+use Icinga\Repository\RepositoryQuery;
+use Icinga\Protocol\Ldap\LdapException;
+use Icinga\User;
+
+class LdapUserBackend extends LdapRepository implements UserBackendInterface, DomainAwareInterface, Inspectable
+{
+    /**
+     * The base DN to use for a query
+     *
+     * @var string
+     */
+    protected $baseDn;
+
+    /**
+     * The objectClass where look for users
+     *
+     * @var string
+     */
+    protected $userClass;
+
+    /**
+     * The attribute name where to find a user's name
+     *
+     * @var string
+     */
+    protected $userNameAttribute;
+
+    /**
+     * The custom LDAP filter to apply on search queries
+     *
+     * @var string
+     */
+    protected $filter;
+
+    /**
+     * The domain the backend is responsible for
+     *
+     * @var string
+     */
+    protected $domain;
+
+    /**
+     * The columns which are not permitted to be queried
+     *
+     * @var array
+     */
+    protected $blacklistedQueryColumns = array('user');
+
+    /**
+     * The search columns being provided
+     *
+     * @var array
+     */
+    protected $searchColumns = array('user');
+
+    /**
+     * The default sort rules to be applied on a query
+     *
+     * @var array
+     */
+    protected $sortRules = array(
+        'user_name' => array(
+            'columns'   => array(
+                'is_active desc',
+                'user_name'
+            )
+        )
+    );
+
+    /**
+     * Set the base DN to use for a query
+     *
+     * @param   string  $baseDn
+     *
+     * @return  $this
+     */
+    public function setBaseDn($baseDn)
+    {
+        if ($baseDn && ($baseDn = trim($baseDn))) {
+            $this->baseDn = $baseDn;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the base DN to use for a query
+     *
+     * @return  string
+     */
+    public function getBaseDn()
+    {
+        return $this->baseDn;
+    }
+
+    /**
+     * Set the objectClass where to look for users
+     *
+     * @param   string  $userClass
+     *
+     * @return  $this
+     */
+    public function setUserClass($userClass)
+    {
+        $this->userClass = $this->getNormedAttribute($userClass);
+        return $this;
+    }
+
+    /**
+     * Return the objectClass where to look for users
+     *
+     * @return string
+     */
+    public function getUserClass()
+    {
+        return $this->userClass;
+    }
+
+    /**
+     * Set the attribute name where to find a user's name
+     *
+     * @param   string  $userNameAttribute
+     *
+     * @return  $this
+     */
+    public function setUserNameAttribute($userNameAttribute)
+    {
+        $this->userNameAttribute = $this->getNormedAttribute($userNameAttribute);
+        return $this;
+    }
+
+    /**
+     * Return the attribute name where to find a user's name
+     *
+     * @return  string
+     */
+    public function getUserNameAttribute()
+    {
+        return $this->userNameAttribute;
+    }
+
+    /**
+     * Set the custom LDAP filter to apply on search queries
+     *
+     * @param   string  $filter
+     *
+     * @return  $this
+     */
+    public function setFilter($filter)
+    {
+        if ($filter && ($filter = trim($filter))) {
+            if ($filter[0] === '(') {
+                $filter = substr($filter, 1, -1);
+            }
+
+            $this->filter = $filter;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the custom LDAP filter to apply on search queries
+     *
+     * @return  string
+     */
+    public function getFilter()
+    {
+        return $this->filter;
+    }
+
+    public function getDomain()
+    {
+        return $this->domain;
+    }
+
+    /**
+     * Set the domain the backend is responsible for
+     *
+     * @param   string  $domain
+     *
+     * @return  $this
+     */
+    public function setDomain($domain)
+    {
+        if ($domain && ($domain = trim($domain))) {
+            $this->domain = $domain;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Initialize this repository's virtual tables
+     *
+     * @return  array
+     *
+     * @throws  ProgrammingError    In case $this->userClass has not been set yet
+     */
+    protected function initializeVirtualTables()
+    {
+        if ($this->userClass === null) {
+            throw new ProgrammingError('It is required to set the object class where to find users first');
+        }
+
+        return array(
+            'user' => $this->userClass
+        );
+    }
+
+    /**
+     * Initialize this repository's query columns
+     *
+     * @return  array
+     *
+     * @throws  ProgrammingError    In case $this->userNameAttribute has not been set yet
+     */
+    protected function initializeQueryColumns()
+    {
+        if ($this->userNameAttribute === null) {
+            throw new ProgrammingError('It is required to set a attribute name where to find a user\'s name first');
+        }
+
+        if ($this->ds->getCapabilities()->isActiveDirectory()) {
+            $isActiveAttribute = 'userAccountControl';
+            $createdAtAttribute = 'whenCreated';
+            $lastModifiedAttribute = 'whenChanged';
+        } else {
+            // TODO(jom): Elaborate whether it is possible to add dynamic support for the ppolicy
+            $isActiveAttribute = 'shadowExpire';
+
+            $createdAtAttribute = 'createTimestamp';
+            $lastModifiedAttribute = 'modifyTimestamp';
+        }
+
+        return array(
+            'user' => array(
+                'user'          => $this->userNameAttribute,
+                'user_name'     => $this->userNameAttribute,
+                'is_active'     => $isActiveAttribute,
+                'created_at'    => $createdAtAttribute,
+                'last_modified' => $lastModifiedAttribute
+            )
+        );
+    }
+
+    /**
+     * Initialize this repository's filter columns
+     *
+     * @return  array
+     */
+    protected function initializeFilterColumns()
+    {
+        return array(
+            t('Username')       => 'user_name',
+            t('Active')         => 'is_active',
+            t('Created At')     => 'created_at',
+            t('Last modified')  => 'last_modified'
+        );
+    }
+
+    /**
+     * Initialize this repository's conversion rules
+     *
+     * @return  array
+     */
+    protected function initializeConversionRules()
+    {
+        if ($this->ds->getCapabilities()->isActiveDirectory()) {
+            $stateConverter = 'user_account_control';
+        } else {
+            $stateConverter = 'shadow_expire';
+        }
+
+        return array(
+            'user' => array(
+                'is_active'     => $stateConverter,
+                'created_at'    => 'generalized_time',
+                'last_modified' => 'generalized_time'
+            )
+        );
+    }
+
+    /**
+     * Return whether the given userAccountControl value defines that a user is permitted to login
+     *
+     * @param   string|null     $value
+     *
+     * @return  bool
+     */
+    protected function retrieveUserAccountControl($value)
+    {
+        if ($value === null) {
+            return $value;
+        }
+
+        $ADS_UF_ACCOUNTDISABLE = 2;
+        return ((int) $value & $ADS_UF_ACCOUNTDISABLE) === 0;
+    }
+
+    /**
+     * Return whether the given shadowExpire value defines that a user is permitted to login
+     *
+     * @param   string|null     $value
+     *
+     * @return  bool
+     */
+    protected function retrieveShadowExpire($value)
+    {
+        if ($value === null) {
+            return $value;
+        }
+
+        $now = new DateTime();
+        $bigBang = clone $now;
+        $bigBang->setTimestamp(0);
+        return ((int) $value) >= $bigBang->diff($now)->days;
+    }
+
+    /**
+     * Validate that the requested table exists
+     *
+     * @param   string              $table      The table to validate
+     * @param   RepositoryQuery     $query      An optional query to pass as context
+     *
+     * @return  string
+     *
+     * @throws  ProgrammingError                In case the given table does not exist
+     */
+    public function requireTable($table, RepositoryQuery $query = null)
+    {
+        if ($query !== null) {
+            $query->getQuery()->setBase($this->baseDn);
+            if ($this->filter) {
+                $query->getQuery()->setNativeFilter($this->filter);
+            }
+        }
+
+        return parent::requireTable($table, $query);
+    }
+
+    /**
+     * Validate that the given column is a valid query target and return it or the actual name if it's an alias
+     *
+     * @param   string              $table  The table where to look for the column or alias
+     * @param   string              $name   The name or alias of the column to validate
+     * @param   RepositoryQuery     $query  An optional query to pass as context
+     *
+     * @return  string                      The given column's name
+     *
+     * @throws  QueryException              In case the given column is not a valid query column
+     */
+    public function requireQueryColumn($table, $name, RepositoryQuery $query = null)
+    {
+        $column = parent::requireQueryColumn($table, $name, $query);
+        if ($name === 'user_name' && $query !== null) {
+            $query->getQuery()->setUnfoldAttribute('user_name');
+        }
+
+        return $column;
+    }
+
+    /**
+     * Authenticate the given user
+     *
+     * @param   User        $user
+     * @param   string      $password
+     *
+     * @return  bool                        True on success, false on failure
+     *
+     * @throws  AuthenticationException     In case authentication is not possible due to an error
+     */
+    public function authenticate(User $user, $password)
+    {
+        if ($this->domain !== null) {
+            if (! $user->hasDomain() || strtolower($user->getDomain()) !== strtolower($this->domain)) {
+                return false;
+            }
+
+            $username = $user->getLocalUsername();
+        } else {
+            $username = $user->getUsername();
+        }
+
+        try {
+            $userDn = $this
+                ->select()
+                ->where('user_name', str_replace('*', '', $username))
+                ->getQuery()
+                ->setUsePagedResults(false)
+                ->fetchDn();
+            if ($userDn === null) {
+                return false;
+            }
+
+            $validCredentials = $this->ds->testCredentials($userDn, $password);
+            if ($validCredentials) {
+                $user->setAdditional('ldap_dn', $userDn);
+            }
+
+            return $validCredentials;
+        } catch (LdapException $e) {
+            throw new AuthenticationException(
+                'Failed to authenticate user "%s" against backend "%s". An exception was thrown:',
+                $username,
+                $this->getName(),
+                $e
+            );
+        }
+    }
+
+    /**
+     * Inspect if this LDAP User Backend is working as expected by probing the backend
+     * and testing if thea uthentication is possible
+     *
+     * Try to bind to the backend and fetch a single user to check if:
+     * <ul>
+     *  <li>Connection credentials are correct and the bind is possible</li>
+     *  <li>At least one user exists</li>
+     *  <li>The specified userClass has the property specified by userNameAttribute</li>
+     * </ul>
+     *
+     * @return  Inspection  Inspection result
+     */
+    public function inspect()
+    {
+        $result = new Inspection('Ldap User Backend');
+
+        // inspect the used connection to get more diagnostic info in case the connection is not working
+        $result->write($this->ds->inspect());
+        try {
+            try {
+                $res = $this->select()->fetchRow();
+            } catch (LdapException $e) {
+                throw new AuthenticationException('Connection not possible', $e);
+            }
+            $result->write('Searching for: ' . sprintf(
+                'objectClass "%s" in DN "%s" (Filter: %s)',
+                $this->userClass,
+                $this->baseDn ?: $this->ds->getDn(),
+                $this->filter ?: 'None'
+            ));
+            if ($res === false) {
+                throw new AuthenticationException('Error, no users found in backend');
+            }
+            $result->write(sprintf('%d users found in backend', $this->select()->count()));
+            if (! isset($res->user_name)) {
+                throw new AuthenticationException(
+                    'UserNameAttribute "%s" not existing in objectClass "%s"',
+                    $this->userNameAttribute,
+                    $this->userClass
+                );
+            }
+        } catch (AuthenticationException $e) {
+            if (($previous = $e->getPrevious()) !== null) {
+                $result->error($previous->getMessage());
+            } else {
+                $result->error($e->getMessage());
+            }
+        } catch (Exception $e) {
+            $result->error(sprintf('Unable to validate authentication: %s', $e->getMessage()));
+        }
+        return $result;
+    }
+}
diff --git a/library/Icinga/Authentication/User/UserBackend.php b/library/Icinga/Authentication/User/UserBackend.php
new file mode 100644
index 0000000..f2059ed
--- /dev/null
+++ b/library/Icinga/Authentication/User/UserBackend.php
@@ -0,0 +1,257 @@
+<?php
+/* Icinga Web 2 | (c) 2013 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+use Icinga\Application\Config;
+use Icinga\Application\Logger;
+use Icinga\Application\Icinga;
+use Icinga\Data\ConfigObject;
+use Icinga\Data\ResourceFactory;
+use Icinga\Exception\ConfigurationError;
+use Icinga\Util\ConfigAwareFactory;
+
+/**
+ * Factory for user backends
+ */
+class UserBackend implements ConfigAwareFactory
+{
+    /**
+     * The default user backend types provided by Icinga Web 2
+     *
+     * @var array
+     */
+    protected static $defaultBackends = array(
+        'external',
+        'db',
+        'ldap',
+        'msldap'
+    );
+
+    /**
+     * The registered custom user backends with their identifier as key and class name as value
+     *
+     * @var array
+     */
+    protected static $customBackends;
+
+    /**
+     * User backend configuration
+     *
+     * @var Config
+     */
+    private static $backends;
+
+    /**
+     * Set user backend configuration
+     *
+     * @param   Config  $config
+     */
+    public static function setConfig($config)
+    {
+        self::$backends = $config;
+    }
+
+    /**
+     * Return the configuration of all existing user backends
+     *
+     * @return  Config
+     */
+    public static function getBackendConfigs()
+    {
+        self::assertBackendsExist();
+        return self::$backends;
+    }
+
+    /**
+     * Check if any user backends exist. If not, throw an error.
+     *
+     * @throws  ConfigurationError
+     */
+    private static function assertBackendsExist()
+    {
+        if (self::$backends === null) {
+            throw new ConfigurationError(
+                'User backends not set up. Please contact your Icinga Web administrator'
+            );
+        }
+    }
+
+    /**
+     * Register all custom user backends from all loaded modules
+     */
+    protected static function registerCustomUserBackends()
+    {
+        if (static::$customBackends !== null) {
+            return;
+        }
+
+        static::$customBackends = array();
+        $providedBy = array();
+        foreach (Icinga::app()->getModuleManager()->getLoadedModules() as $module) {
+            foreach ($module->getUserBackends() as $identifier => $className) {
+                if (array_key_exists($identifier, $providedBy)) {
+                    Logger::warning(
+                        'Cannot register user backend of type "%s" provided by module "%s".'
+                        . ' The type is already provided by module "%s"',
+                        $identifier,
+                        $module->getName(),
+                        $providedBy[$identifier]
+                    );
+                } elseif (in_array($identifier, static::$defaultBackends)) {
+                    Logger::warning(
+                        'Cannot register user backend of type "%s" provided by module "%s".'
+                        . ' The type is a default type provided by Icinga Web 2',
+                        $identifier,
+                        $module->getName()
+                    );
+                } else {
+                    $providedBy[$identifier] = $module->getName();
+                    static::$customBackends[$identifier] = $className;
+                }
+            }
+        }
+    }
+
+    /**
+     * Get config forms of all custom user backends
+     */
+    public static function getCustomBackendConfigForms()
+    {
+        $customBackendConfigForms = [];
+        static::registerCustomUserBackends();
+        foreach (self::$customBackends as $customBackendType => $customBackendClass) {
+            if (method_exists($customBackendClass, 'getConfigurationFormClass')) {
+                $customBackendConfigForms[$customBackendType] = $customBackendClass::getConfigurationFormClass();
+            }
+        }
+
+        return $customBackendConfigForms;
+    }
+
+    /**
+     * Return the class for the given custom user backend
+     *
+     * @param   string  $identifier     The identifier of the custom user backend
+     *
+     * @return  string|null             The name of the class or null in case there was no
+     *                                   backend found with the given identifier
+     *
+     * @throws  ConfigurationError      In case the class associated to the given identifier does not exist
+     */
+    protected static function getCustomUserBackend($identifier)
+    {
+        static::registerCustomUserBackends();
+        if (array_key_exists($identifier, static::$customBackends)) {
+            $className = static::$customBackends[$identifier];
+            if (! class_exists($className)) {
+                throw new ConfigurationError(
+                    'Cannot utilize user backend of type "%s". Class "%s" does not exist',
+                    $identifier,
+                    $className
+                );
+            }
+
+            return $className;
+        }
+    }
+
+    /**
+     * Create and return a user backend with the given name and given configuration applied to it
+     *
+     * @param   string          $name
+     * @param   ConfigObject    $backendConfig
+     *
+     * @return  UserBackendInterface
+     *
+     * @throws  ConfigurationError
+     */
+    public static function create($name, ConfigObject $backendConfig = null)
+    {
+        if ($backendConfig === null) {
+            self::assertBackendsExist();
+            if (self::$backends->hasSection($name)) {
+                $backendConfig = self::$backends->getSection($name);
+            } else {
+                throw new ConfigurationError('User backend "%s" does not exist', $name);
+            }
+        }
+
+        if ($backendConfig->name !== null) {
+            $name = $backendConfig->name;
+        }
+
+        if (! ($backendType = strtolower($backendConfig->backend))) {
+            throw new ConfigurationError(
+                'Authentication configuration for user backend "%s" is missing the \'backend\' directive',
+                $name
+            );
+        }
+        if ($backendType === 'external') {
+            $backend = new ExternalBackend($backendConfig);
+            $backend->setName($name);
+            return $backend;
+        }
+        if (in_array($backendType, static::$defaultBackends)) {
+            // The default backend check is the first one because of performance reasons:
+            // Do not attempt to load a custom user backend unless it's actually required
+        } elseif (($customClass = static::getCustomUserBackend($backendType)) !== null) {
+            $backend = new $customClass($backendConfig);
+            if (! is_a($backend, 'Icinga\Authentication\User\UserBackendInterface')) {
+                throw new ConfigurationError(
+                    'Cannot utilize user backend of type "%s". Class "%s" does not implement UserBackendInterface',
+                    $backendType,
+                    $customClass
+                );
+            }
+
+            $backend->setName($name);
+            return $backend;
+        } else {
+            throw new ConfigurationError(
+                'Authentication configuration for user backend "%s" defines an invalid backend type.'
+                . ' Backend type "%s" is not supported',
+                $name,
+                $backendType
+            );
+        }
+
+        if ($backendConfig->resource === null) {
+            throw new ConfigurationError(
+                'Authentication configuration for user backend "%s" is missing the \'resource\' directive',
+                $name
+            );
+        }
+
+        $resourceConfig = ResourceFactory::getResourceConfig($backendConfig->resource);
+        if ($backendType === 'db' && $resourceConfig->db === 'mysql') {
+            $resourceConfig->charset = 'utf8mb4';
+        }
+
+        $resource = ResourceFactory::createResource($resourceConfig);
+        switch ($backendType) {
+            case 'db':
+                $backend = new DbUserBackend($resource);
+                break;
+            case 'msldap':
+                $backend = new LdapUserBackend($resource);
+                $backend->setBaseDn($backendConfig->base_dn);
+                $backend->setUserClass($backendConfig->get('user_class', 'user'));
+                $backend->setUserNameAttribute($backendConfig->get('user_name_attribute', 'sAMAccountName'));
+                $backend->setFilter($backendConfig->filter);
+                $backend->setDomain($backendConfig->domain);
+                break;
+            case 'ldap':
+                $backend = new LdapUserBackend($resource);
+                $backend->setBaseDn($backendConfig->base_dn);
+                $backend->setUserClass($backendConfig->get('user_class', 'inetOrgPerson'));
+                $backend->setUserNameAttribute($backendConfig->get('user_name_attribute', 'uid'));
+                $backend->setFilter($backendConfig->filter);
+                $backend->setDomain($backendConfig->domain);
+                break;
+        }
+
+        $backend->setName($name);
+        return $backend;
+    }
+}
diff --git a/library/Icinga/Authentication/User/UserBackendInterface.php b/library/Icinga/Authentication/User/UserBackendInterface.php
new file mode 100644
index 0000000..4660eb0
--- /dev/null
+++ b/library/Icinga/Authentication/User/UserBackendInterface.php
@@ -0,0 +1,39 @@
+<?php
+/* Icinga Web 2 | (c) 2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\User;
+
+use Icinga\Authentication\Authenticatable;
+use Icinga\User;
+
+/**
+ * Interface for user backends
+ */
+interface UserBackendInterface extends Authenticatable
+{
+    /**
+     * Set this backend's name
+     *
+     * @param   string  $name
+     *
+     * @return  $this
+     */
+    public function setName($name);
+
+    /**
+     * Return this backend's name
+     *
+     * @return  string
+     */
+    public function getName();
+
+    /**
+     * Return this backend's configuration form class path
+     *
+     * This is not part of the interface to not break existing implementations.
+     * If you need a custom backend form, implement this method.
+     *
+     * @return  string
+     */
+    //public static function getConfigurationFormClass();
+}
diff --git a/library/Icinga/Authentication/UserGroup/DbUserGroupBackend.php b/library/Icinga/Authentication/UserGroup/DbUserGroupBackend.php
new file mode 100644
index 0000000..66db97f
--- /dev/null
+++ b/library/Icinga/Authentication/UserGroup/DbUserGroupBackend.php
@@ -0,0 +1,325 @@
+<?php
+/* Icinga Web 2 | (c) 2014 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\UserGroup;
+
+use Exception;
+use Icinga\Data\Filter\Filter;
+use Icinga\Data\Inspectable;
+use Icinga\Data\Inspection;
+use Icinga\Exception\NotFoundError;
+use Icinga\Repository\DbRepository;
+use Icinga\Repository\RepositoryQuery;
+use Icinga\User;
+
+class DbUserGroupBackend extends DbRepository implements Inspectable, UserGroupBackendInterface
+{
+    /**
+     * The query columns being provided
+     *
+     * @var array
+     */
+    protected $queryColumns = array(
+        'group' => array(
+            'group_id'      => 'g.id',
+            'group'         => 'g.name COLLATE utf8mb4_general_ci',
+            'group_name'    => 'g.name',
+            'parent'        => 'g.parent',
+            'created_at'    => 'UNIX_TIMESTAMP(g.ctime)',
+            'last_modified' => 'UNIX_TIMESTAMP(g.mtime)'
+        ),
+        'group_membership' => array(
+            'group_id'      => 'gm.group_id',
+            'user'          => 'gm.username COLLATE utf8mb4_general_ci',
+            'user_name'     => 'gm.username',
+            'created_at'    => 'UNIX_TIMESTAMP(gm.ctime)',
+            'last_modified' => 'UNIX_TIMESTAMP(gm.mtime)'
+        )
+    );
+
+    /**
+     * The table aliases being applied
+     *
+     * @var array
+     */
+    protected $tableAliases = array(
+        'group'             => 'g',
+        'group_membership'  => 'gm'
+    );
+
+    /**
+     * The statement columns being provided
+     *
+     * @var array
+     */
+    protected $statementColumns = array(
+        'group' => array(
+            'group_id'      => 'id',
+            'group_name'    => 'name',
+            'parent'        => 'parent',
+            'created_at'    => 'ctime',
+            'last_modified' => 'mtime'
+        ),
+        'group_membership' => array(
+            'group_id'      => 'group_id',
+            'group_name'    => 'group_id',
+            'user_name'     => 'username',
+            'created_at'    => 'ctime',
+            'last_modified' => 'mtime'
+        )
+    );
+
+    /**
+     * The columns which are not permitted to be queried
+     *
+     * @var array
+     */
+    protected $blacklistedQueryColumns = array('group', 'user');
+
+    /**
+     * The search columns being provided
+     *
+     * @var array
+     */
+    protected $searchColumns = array('group', 'user');
+
+    /**
+     * The value conversion rules to apply on a query or statement
+     *
+     * @var array
+     */
+    protected $conversionRules = array(
+        'group'             => array(
+            'parent'        => 'group_id'
+        ),
+        'group_membership'  => array(
+            'group_name'    => 'group_id'
+        )
+    );
+
+    /**
+     * Initialize this database user group backend
+     */
+    protected function init()
+    {
+        if (! $this->ds->getTablePrefix()) {
+            $this->ds->setTablePrefix('icingaweb_');
+        }
+    }
+
+    /**
+     * Initialize this repository's filter columns
+     *
+     * @return  array
+     */
+    protected function initializeFilterColumns()
+    {
+        $userLabel = t('Username') . ' ' . t('(Case insensitive)');
+        $groupLabel = t('User Group') . ' ' . t('(Case insensitive)');
+        return array(
+            $userLabel          => 'user',
+            t('Username')       => 'user_name',
+            $groupLabel         => 'group',
+            t('User Group')     => 'group_name',
+            t('Parent')         => 'parent',
+            t('Created At')     => 'created_at',
+            t('Last modified')  => 'last_modified'
+        );
+    }
+
+    /**
+     * Insert a table row with the given data
+     *
+     * @param   string  $table
+     * @param   array   $bind
+     */
+    public function insert($table, array $bind, array $types = array())
+    {
+        $bind['created_at'] = date('Y-m-d H:i:s');
+        parent::insert($table, $bind);
+    }
+
+    /**
+     * Update table rows with the given data, optionally limited by using a filter
+     *
+     * @param   string  $table
+     * @param   array   $bind
+     * @param   Filter  $filter
+     */
+    public function update($table, array $bind, Filter $filter = null, array $types = array())
+    {
+        $bind['last_modified'] = date('Y-m-d H:i:s');
+        parent::update($table, $bind, $filter);
+    }
+
+    /**
+     * Delete table rows, optionally limited by using a filter
+     *
+     * @param   string  $table
+     * @param   Filter  $filter
+     */
+    public function delete($table, Filter $filter = null)
+    {
+        if ($table === 'group') {
+            parent::delete('group_membership', $filter);
+            $idQuery = $this->select(array('group_id'));
+            if ($filter !== null) {
+                $idQuery->applyFilter($filter);
+            }
+
+            $this->update('group', array('parent' => null), Filter::where('parent', $idQuery->fetchColumn()));
+        }
+
+        parent::delete($table, $filter);
+    }
+
+    /**
+     * Return the groups the given user is a member of
+     *
+     * @param   User    $user
+     *
+     * @return  array
+     */
+    public function getMemberships(User $user)
+    {
+        $groupQuery = $this->ds
+            ->select()
+            ->from(
+                array('g' => $this->prependTablePrefix('group')),
+                array(
+                    'group_name'    => 'g.name',
+                    'parent_name'   => 'gg.name'
+                )
+            )->joinLeft(
+                array('gg' => $this->prependTablePrefix('group')),
+                'g.parent = gg.id',
+                array()
+            );
+
+        $groups = array();
+        foreach ($groupQuery as $group) {
+            $groups[$group->group_name] = $group->parent_name;
+        }
+
+        $membershipQuery = $this
+            ->select()
+            ->from('group_membership', array('group_name'))
+            ->where('user_name', $user->getUsername());
+
+        $memberships = array();
+        foreach ($membershipQuery as $membership) {
+            $memberships[] = $membership->group_name;
+            $parent = $groups[$membership->group_name];
+            while ($parent !== null) {
+                $memberships[] = $parent;
+                // Usually a parent is an existing group, but since we do not have a constraint on our table..
+                $parent = isset($groups[$parent]) ? $groups[$parent] : null;
+            }
+        }
+
+        return $memberships;
+    }
+
+    /**
+     * Return the name of the backend that is providing the given user
+     *
+     * @param   string  $username   Currently unused
+     *
+     * @return  null|string     The name of the backend or null in case this information is not available
+     */
+    public function getUserBackendName($username)
+    {
+        return null; // TODO(10373): Store this to the database when inserting and fetch it here
+    }
+
+    /**
+     * Join group into group_membership
+     *
+     * @param   RepositoryQuery     $query
+     */
+    protected function joinGroup(RepositoryQuery $query)
+    {
+        $query->getQuery()->join(
+            $this->requireTable('group'),
+            'gm.group_id = g.id',
+            array()
+        );
+    }
+
+    /**
+     * Join group_membership into group
+     *
+     * @param   RepositoryQuery     $query
+     */
+    protected function joinGroupMembership(RepositoryQuery $query)
+    {
+        $query->getQuery()->joinLeft(
+            $this->requireTable('group_membership'),
+            'g.id = gm.group_id',
+            array()
+        )->group('g.id');
+    }
+
+    /**
+     * Fetch and return the corresponding id for the given group's name
+     *
+     * @param   string|array    $groupName
+     *
+     * @return  int
+     *
+     * @throws  NotFoundError
+     */
+    protected function persistGroupId($groupName)
+    {
+        if (! $groupName || empty($groupName) || is_numeric($groupName)) {
+            return $groupName;
+        }
+
+        if (is_array($groupName)) {
+            if (is_numeric($groupName[0])) {
+                return $groupName; // In case the array contains mixed types...
+            }
+
+            $groupIds = $this->ds
+                ->select()
+                ->from($this->prependTablePrefix('group'), array('id'))
+                ->where('name', $groupName)
+                ->fetchColumn();
+            if (empty($groupIds)) {
+                throw new NotFoundError('No groups found matching one of: %s', implode(', ', $groupName));
+            }
+
+            return $groupIds;
+        }
+
+        $groupId = $this->ds
+            ->select()
+            ->from($this->prependTablePrefix('group'), array('id'))
+            ->where('name', $groupName)
+            ->fetchOne();
+        if ($groupId === false) {
+            throw new NotFoundError('Group "%s" does not exist', $groupName);
+        }
+
+        return $groupId;
+    }
+
+    /**
+     * Inspect this object to gain extended information about its health
+     *
+     * @return Inspection           The inspection result
+     */
+    public function inspect()
+    {
+        $insp = new Inspection('Db User Group Backend');
+        $insp->write($this->ds->inspect());
+
+        try {
+            $insp->write(sprintf('%s group(s)', $this->select()->count()));
+        } catch (Exception $e) {
+            $insp->error(sprintf('Query failed: %s', $e->getMessage()));
+        }
+
+        return $insp;
+    }
+}
diff --git a/library/Icinga/Authentication/UserGroup/LdapUserGroupBackend.php b/library/Icinga/Authentication/UserGroup/LdapUserGroupBackend.php
new file mode 100644
index 0000000..54ccaa9
--- /dev/null
+++ b/library/Icinga/Authentication/UserGroup/LdapUserGroupBackend.php
@@ -0,0 +1,944 @@
+<?php
+/* Icinga Web 2 | (c) 2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\UserGroup;
+
+use Exception;
+use Icinga\Authentication\User\UserBackend;
+use Icinga\Authentication\User\LdapUserBackend;
+use Icinga\Application\Logger;
+use Icinga\Data\ConfigObject;
+use Icinga\Data\Inspectable;
+use Icinga\Data\Inspection;
+use Icinga\Exception\AuthenticationException;
+use Icinga\Exception\ConfigurationError;
+use Icinga\Exception\ProgrammingError;
+use Icinga\Protocol\Ldap\LdapException;
+use Icinga\Protocol\Ldap\LdapUtils;
+use Icinga\Repository\LdapRepository;
+use Icinga\Repository\RepositoryQuery;
+use Icinga\User;
+
+class LdapUserGroupBackend extends LdapRepository implements Inspectable, UserGroupBackendInterface
+{
+    /**
+     * The user backend being associated with this user group backend
+     *
+     * @var LdapUserBackend
+     */
+    protected $userBackend;
+
+    /**
+     * The base DN to use for a user query
+     *
+     * @var string
+     */
+    protected $userBaseDn;
+
+    /**
+     * The base DN to use for a group query
+     *
+     * @var string
+     */
+    protected $groupBaseDn;
+
+    /**
+     * The objectClass where look for users
+     *
+     * @var string
+     */
+    protected $userClass;
+
+    /**
+     * The objectClass where look for groups
+     *
+     * @var string
+     */
+    protected $groupClass;
+
+    /**
+     * The attribute name where to find a user's name
+     *
+     * @var string
+     */
+    protected $userNameAttribute;
+
+    /**
+     * The attribute name where to find a group's name
+     *
+     * @var string
+     */
+    protected $groupNameAttribute;
+
+    /**
+     * The attribute name where to find a group's member
+     *
+     * @var string
+     */
+    protected $groupMemberAttribute;
+
+    /**
+     * Whether the attribute name where to find a group's member holds ambiguous values
+     *
+     * @var bool
+     */
+    protected $ambiguousMemberAttribute;
+
+    /**
+     * The custom LDAP filter to apply on a user query
+     *
+     * @var string
+     */
+    protected $userFilter;
+
+    /**
+     * The custom LDAP filter to apply on a group query
+     *
+     * @var string
+     */
+    protected $groupFilter;
+
+    /**
+     * ActiveDirectory nested group on the user?
+     *
+     * @var bool
+     */
+    protected $nestedGroupSearch;
+
+    /**
+     * The domain the backend is responsible for
+     *
+     * @var string
+     */
+    protected $domain;
+
+    /**
+     * The columns which are not permitted to be queried
+     *
+     * @var array
+     */
+    protected $blacklistedQueryColumns = array('group', 'user');
+
+    /**
+     * The search columns being provided
+     *
+     * @var array
+     */
+    protected $searchColumns = array('group', 'user');
+
+    /**
+     * The default sort rules to be applied on a query
+     *
+     * @var array
+     */
+    protected $sortRules = array(
+        'group_name' => array(
+            'order' => 'asc'
+        )
+    );
+
+    /**
+     * Set the user backend to be associated with this user group backend
+     *
+     * @param   LdapUserBackend     $backend
+     *
+     * @return  $this
+     */
+    public function setUserBackend(LdapUserBackend $backend)
+    {
+        $this->userBackend = $backend;
+        return $this;
+    }
+
+    /**
+     * Return the user backend being associated with this user group backend
+     *
+     * @return  LdapUserBackend
+     */
+    public function getUserBackend()
+    {
+        return $this->userBackend;
+    }
+
+    /**
+     * Set the base DN to use for a user query
+     *
+     * @param   string  $baseDn
+     *
+     * @return  $this
+     */
+    public function setUserBaseDn($baseDn)
+    {
+        if ($baseDn && ($baseDn = trim($baseDn))) {
+            $this->userBaseDn = $baseDn;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the base DN to use for a user query
+     *
+     * @return  string
+     */
+    public function getUserBaseDn()
+    {
+        return $this->userBaseDn;
+    }
+
+    /**
+     * Set the base DN to use for a group query
+     *
+     * @param   string  $baseDn
+     *
+     * @return  $this
+     */
+    public function setGroupBaseDn($baseDn)
+    {
+        if ($baseDn && ($baseDn = trim($baseDn))) {
+            $this->groupBaseDn = $baseDn;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the base DN to use for a group query
+     *
+     * @return  string
+     */
+    public function getGroupBaseDn()
+    {
+        return $this->groupBaseDn;
+    }
+
+    /**
+     * Set the objectClass where to look for users
+     *
+     * @param   string  $userClass
+     *
+     * @return  $this
+     */
+    public function setUserClass($userClass)
+    {
+        $this->userClass = $this->getNormedAttribute($userClass);
+        return $this;
+    }
+
+    /**
+     * Return the objectClass where to look for users
+     *
+     * @return string
+     */
+    public function getUserClass()
+    {
+        return $this->userClass;
+    }
+
+    /**
+     * Set the objectClass where to look for groups
+     *
+     * @param   string  $groupClass
+     *
+     * @return  $this
+     */
+    public function setGroupClass($groupClass)
+    {
+        $this->groupClass = $this->getNormedAttribute($groupClass);
+        return $this;
+    }
+
+    /**
+     * Return the objectClass where to look for groups
+     *
+     * @return string
+     */
+    public function getGroupClass()
+    {
+        return $this->groupClass;
+    }
+
+    /**
+     * Set the attribute name where to find a user's name
+     *
+     * @param   string  $userNameAttribute
+     *
+     * @return  $this
+     */
+    public function setUserNameAttribute($userNameAttribute)
+    {
+        $this->userNameAttribute = $this->getNormedAttribute($userNameAttribute);
+        return $this;
+    }
+
+    /**
+     * Return the attribute name where to find a user's name
+     *
+     * @return  string
+     */
+    public function getUserNameAttribute()
+    {
+        return $this->userNameAttribute;
+    }
+
+    /**
+     * Set the attribute name where to find a group's name
+     *
+     * @param   string  $groupNameAttribute
+     *
+     * @return  $this
+     */
+    public function setGroupNameAttribute($groupNameAttribute)
+    {
+        $this->groupNameAttribute = $this->getNormedAttribute($groupNameAttribute);
+        return $this;
+    }
+
+    /**
+     * Return the attribute name where to find a group's name
+     *
+     * @return  string
+     */
+    public function getGroupNameAttribute()
+    {
+        return $this->groupNameAttribute;
+    }
+
+    /**
+     * Set the attribute name where to find a group's member
+     *
+     * @param   string  $groupMemberAttribute
+     *
+     * @return  $this
+     */
+    public function setGroupMemberAttribute($groupMemberAttribute)
+    {
+        $this->groupMemberAttribute = $this->getNormedAttribute($groupMemberAttribute);
+        return $this;
+    }
+
+    /**
+     * Return the attribute name where to find a group's member
+     *
+     * @return  string
+     */
+    public function getGroupMemberAttribute()
+    {
+        return $this->groupMemberAttribute;
+    }
+
+    /**
+     * Set the custom LDAP filter to apply on a user query
+     *
+     * @param   string  $filter
+     *
+     * @return  $this
+     */
+    public function setUserFilter($filter)
+    {
+        if ($filter && ($filter = trim($filter))) {
+            if ($filter[0] === '(') {
+                $filter = substr($filter, 1, -1);
+            }
+
+            $this->userFilter = $filter;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the custom LDAP filter to apply on a user query
+     *
+     * @return  string
+     */
+    public function getUserFilter()
+    {
+        return $this->userFilter;
+    }
+
+    /**
+     * Set the custom LDAP filter to apply on a group query
+     *
+     * @param   string  $filter
+     *
+     * @return  $this
+     */
+    public function setGroupFilter($filter)
+    {
+        if ($filter && ($filter = trim($filter))) {
+            $this->groupFilter = $filter;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return the custom LDAP filter to apply on a group query
+     *
+     * @return  string
+     */
+    public function getGroupFilter()
+    {
+        return $this->groupFilter;
+    }
+
+    /**
+     * Set nestedGroupSearch for the group query
+     *
+     * @param   bool    $enable
+     *
+     * @return  $this
+     */
+    public function setNestedGroupSearch($enable = true)
+    {
+        $this->nestedGroupSearch = $enable;
+        return $this;
+    }
+
+    /**
+     * Get nestedGroupSearch for the group query
+     *
+     * @return bool
+     */
+    public function getNestedGroupSearch()
+    {
+        return $this->nestedGroupSearch;
+    }
+
+    /**
+     * Get the domain the backend is responsible for
+     *
+     * If the LDAP group backend is linked with a LDAP user backend,
+     * the domain of the user backend will be returned.
+     *
+     * @return string
+     */
+    public function getDomain()
+    {
+        return $this->userBackend !== null ? $this->userBackend->getDomain() : $this->domain;
+    }
+
+    /**
+     * Set the domain the backend is responsible for
+     *
+     * If the LDAP group backend is linked with a LDAP user backend,
+     * the domain of the user backend will be used nonetheless.
+     *
+     * @param   string  $domain
+     *
+     * @return  $this
+     */
+    public function setDomain($domain)
+    {
+        if ($domain && ($domain = trim($domain))) {
+            $this->domain = $domain;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Return whether the attribute name where to find a group's member holds ambiguous values
+     *
+     * This tries to detect if the member attribute of groups contain:
+     *
+     *  full DN -> distinguished name of another object
+     *  other   -> ambiguous field referencing the member by userNameAttribute
+     *
+     * @return  bool
+     *
+     * @throws  ProgrammingError    In case either $this->groupClass or $this->groupMemberAttribute
+     *                              has not been set yet
+     */
+    protected function isMemberAttributeAmbiguous()
+    {
+        if ($this->ambiguousMemberAttribute === null) {
+            if ($this->groupClass === null) {
+                throw new ProgrammingError(
+                    'It is required to set the objectClass where to look for groups first'
+                );
+            } elseif ($this->groupMemberAttribute === null) {
+                throw new ProgrammingError(
+                    'It is required to set a attribute name where to find a group\'s members first'
+                );
+            }
+
+            $sampleValues = $this->ds
+                ->select()
+                ->from($this->groupClass, array($this->groupMemberAttribute))
+                ->where($this->groupMemberAttribute, '*')
+                ->limit(Logger::getInstance()->getLevel() === Logger::DEBUG ? 3 : 1)
+                ->setUnfoldAttribute($this->groupMemberAttribute)
+                ->setBase($this->groupBaseDn)
+                ->fetchAll();
+
+            Logger::debug('Ambiguity query returned %d results', count($sampleValues));
+
+            $i = 0;
+            $sampleValue = null;
+            foreach ($sampleValues as $key => $value) {
+                if ($sampleValue === null) {
+                    $sampleValue = $value;
+                }
+
+                Logger::debug('Result %d: %s (%s)', ++$i, $value, $key);
+            }
+
+            if (is_object($sampleValue) && isset($sampleValue->{$this->groupMemberAttribute})) {
+                $this->ambiguousMemberAttribute = ! LdapUtils::isDn($sampleValue->{$this->groupMemberAttribute});
+
+                Logger::debug(
+                    'Ambiguity check came to the conclusion that the member attribute %s ambiguous. Tested sample: %s',
+                    $this->ambiguousMemberAttribute ? 'is' : 'is not',
+                    $sampleValue->{$this->groupMemberAttribute}
+                );
+            } else {
+                Logger::warning(
+                    'Ambiguity query returned zero or invalid results. Sample value is `%s`',
+                    print_r($sampleValue, true)
+                );
+            }
+        }
+
+        return $this->ambiguousMemberAttribute;
+    }
+
+    /**
+     * Initialize this repository's virtual tables
+     *
+     * @return  array
+     *
+     * @throws  ProgrammingError    In case $this->groupClass has not been set yet
+     */
+    protected function initializeVirtualTables()
+    {
+        if ($this->groupClass === null) {
+            throw new ProgrammingError('It is required to set the object class where to find groups first');
+        }
+
+        return array(
+            'group'             => $this->groupClass,
+            'group_membership'  => $this->groupClass
+        );
+    }
+
+    /**
+     * Initialize this repository's query columns
+     *
+     * @return  array
+     *
+     * @throws  ProgrammingError    In case either $this->groupNameAttribute or
+     *                              $this->groupMemberAttribute has not been set yet
+     */
+    protected function initializeQueryColumns()
+    {
+        if ($this->groupNameAttribute === null) {
+            throw new ProgrammingError('It is required to set a attribute name where to find a group\'s name first');
+        }
+        if ($this->groupMemberAttribute === null) {
+            throw new ProgrammingError('It is required to set a attribute name where to find a group\'s members first');
+        }
+
+        if ($this->ds->getCapabilities()->isActiveDirectory()) {
+            $createdAtAttribute = 'whenCreated';
+            $lastModifiedAttribute = 'whenChanged';
+        } else {
+            $createdAtAttribute = 'createTimestamp';
+            $lastModifiedAttribute = 'modifyTimestamp';
+        }
+
+        $columns = array(
+            'group'         => $this->groupNameAttribute,
+            'group_name'    => $this->groupNameAttribute,
+            'user'          => $this->groupMemberAttribute,
+            'user_name'     => $this->groupMemberAttribute,
+            'created_at'    => $createdAtAttribute,
+            'last_modified' => $lastModifiedAttribute
+        );
+        return array('group' => $columns, 'group_membership' => $columns);
+    }
+
+    /**
+     * Initialize this repository's filter columns
+     *
+     * @return  array
+     */
+    protected function initializeFilterColumns()
+    {
+        return array(
+            t('Username')       => 'user_name',
+            t('User Group')     => 'group_name',
+            t('Created At')     => 'created_at',
+            t('Last modified')  => 'last_modified'
+        );
+    }
+
+    /**
+     * Initialize this repository's conversion rules
+     *
+     * @return  array
+     */
+    protected function initializeConversionRules()
+    {
+        $rules = array(
+            'group' => array(
+                'created_at'    => 'generalized_time',
+                'last_modified' => 'generalized_time'
+            ),
+            'group_membership' => array(
+                'created_at'    => 'generalized_time',
+                'last_modified' => 'generalized_time'
+            )
+        );
+        if (! $this->isMemberAttributeAmbiguous()) {
+            $rules['group_membership']['user_name'] = 'user_name';
+            $rules['group_membership']['user'] = 'user_name';
+            $rules['group']['user_name'] = 'user_name';
+            $rules['group']['user'] = 'user_name';
+        }
+
+        return $rules;
+    }
+
+    /**
+     * Return the distinguished name for the given uid or gid
+     *
+     * @param   string  $name
+     *
+     * @return  string
+     */
+    protected function persistUserName($name)
+    {
+        try {
+            $userDn = $this->ds
+                ->select()
+                ->from($this->userClass, array())
+                ->where($this->userNameAttribute, $name)
+                ->setBase($this->userBaseDn)
+                ->setUsePagedResults(false)
+                ->fetchDn();
+            if ($userDn) {
+                return $userDn;
+            }
+
+            $groupDn = $this->ds
+                ->select()
+                ->from($this->groupClass, array())
+                ->where($this->groupNameAttribute, $name)
+                ->setBase($this->groupBaseDn)
+                ->setUsePagedResults(false)
+                ->fetchDn();
+            if ($groupDn) {
+                return $groupDn;
+            }
+        } catch (LdapException $_) {
+            // pass
+        }
+
+        Logger::debug('Unable to persist uid or gid "%s" in repository "%s". No DN found.', $name, $this->getName());
+        return $name;
+    }
+
+    /**
+     * Return the uid for the given distinguished name
+     *
+     * @param   string  $username
+     *
+     * @param   string
+     */
+    protected function retrieveUserName($dn)
+    {
+        return $this->ds
+            ->select()
+            ->from('*', array($this->userNameAttribute))
+            ->setUnfoldAttribute($this->userNameAttribute)
+            ->setBase($dn)
+            ->fetchOne();
+    }
+
+    /**
+     * Validate that the requested table exists
+     *
+     * @param   string              $table      The table to validate
+     * @param   RepositoryQuery     $query      An optional query to pass as context
+     *
+     * @return  string
+     *
+     * @throws  ProgrammingError                In case the given table does not exist
+     */
+    public function requireTable($table, RepositoryQuery $query = null)
+    {
+        if ($query !== null) {
+            $query->getQuery()->setBase($this->groupBaseDn);
+            if ($table === 'group' && $this->groupFilter) {
+                $query->getQuery()->setNativeFilter($this->groupFilter);
+            }
+        }
+
+        return parent::requireTable($table, $query);
+    }
+
+    /**
+     * Validate that the given column is a valid query target and return it or the actual name if it's an alias
+     *
+     * @param   string              $table  The table where to look for the column or alias
+     * @param   string              $name   The name or alias of the column to validate
+     * @param   RepositoryQuery     $query  An optional query to pass as context
+     *
+     * @return  string                      The given column's name
+     *
+     * @throws  QueryException              In case the given column is not a valid query column
+     */
+    public function requireQueryColumn($table, $name, RepositoryQuery $query = null)
+    {
+        $column = parent::requireQueryColumn($table, $name, $query);
+        if (($name === 'user_name' || $name === 'group_name') && $query !== null) {
+            $query->getQuery()->setUnfoldAttribute($name);
+        }
+
+        return $column;
+    }
+
+    /**
+     * Return the groups the given user is a member of
+     *
+     * @param   User    $user
+     *
+     * @return  array
+     */
+    public function getMemberships(User $user)
+    {
+        $domain = $this->getDomain();
+
+        if ($domain !== null) {
+            if (! $user->hasDomain() || strtolower($user->getDomain()) !== strtolower($domain)) {
+                return array();
+            }
+
+            $username = $user->getLocalUsername();
+        } else {
+            $username = $user->getUsername();
+        }
+
+        if ($this->isMemberAttributeAmbiguous()) {
+            $queryValue = $username;
+        } elseif (($queryValue = $user->getAdditional('ldap_dn')) === null) {
+            $userQuery = $this->ds
+                ->select()
+                ->from($this->userClass)
+                ->where($this->userNameAttribute, $username)
+                ->setBase($this->userBaseDn)
+                ->setUsePagedResults(false);
+            if ($this->userFilter) {
+                $userQuery->setNativeFilter($this->userFilter);
+            }
+
+            if (($queryValue = $userQuery->fetchDn()) === null) {
+                return array();
+            }
+        }
+
+        if ($this->nestedGroupSearch) {
+            $groupMemberAttribute = $this->groupMemberAttribute . ':1.2.840.113556.1.4.1941:';
+        } else {
+            $groupMemberAttribute = $this->groupMemberAttribute;
+        }
+
+        $groupQuery = $this->ds
+            ->select()
+            ->from($this->groupClass, array($this->groupNameAttribute))
+            ->setUnfoldAttribute($this->groupNameAttribute)
+            ->where($groupMemberAttribute, $queryValue)
+            ->setBase($this->groupBaseDn);
+        if ($this->groupFilter) {
+            $groupQuery->setNativeFilter($this->groupFilter);
+        }
+
+        $groups = array();
+        foreach ($groupQuery as $row) {
+            $groups[] = $row->{$this->groupNameAttribute};
+            if ($domain !== null) {
+                $groups[] = $row->{$this->groupNameAttribute} . "@$domain";
+            }
+        }
+
+        return $groups;
+    }
+
+    /**
+     * Return the name of the backend that is providing the given user
+     *
+     * @param   string  $username   Unused
+     *
+     * @return  null|string     The name of the backend or null in case this information is not available
+     */
+    public function getUserBackendName($username)
+    {
+        $userBackend = $this->getUserBackend();
+        if ($userBackend !== null) {
+            return $userBackend->getName();
+        }
+    }
+
+    /**
+     * Apply the given configuration on this backend
+     *
+     * @param   ConfigObject    $config
+     *
+     * @return  $this
+     *
+     * @throws  ConfigurationError      In case a linked user backend does not exist or is invalid
+     */
+    public function setConfig(ConfigObject $config)
+    {
+        if ($config->backend === 'ldap') {
+            $defaults = $this->getOpenLdapDefaults();
+        } elseif ($config->backend === 'msldap') {
+            $defaults = $this->getActiveDirectoryDefaults();
+        } else {
+            $defaults = new ConfigObject();
+        }
+
+        if ($config->user_backend && $config->user_backend !== 'none') {
+            $userBackend = UserBackend::create($config->user_backend);
+            if (! $userBackend instanceof LdapUserBackend) {
+                throw new ConfigurationError('User backend "%s" is not of type LDAP', $config->user_backend);
+            }
+
+            if ($this->ds->getHostname() !== $userBackend->getDataSource()->getHostname()
+                || $this->ds->getPort() !== $userBackend->getDataSource()->getPort()
+            ) {
+                // TODO(jom): Elaborate whether it makes sense to link directories on different hosts
+                throw new ConfigurationError(
+                    'It is required that a linked user backend refers to the '
+                    . 'same directory as it\'s user group backend counterpart'
+                );
+            }
+
+            $this->setUserBackend($userBackend);
+            $defaults->merge(array(
+                'user_base_dn'          => $userBackend->getBaseDn(),
+                'user_class'            => $userBackend->getUserClass(),
+                'user_name_attribute'   => $userBackend->getUserNameAttribute(),
+                'user_filter'           => $userBackend->getFilter(),
+                'domain'                => $userBackend->getDomain()
+            ));
+        }
+
+        return $this
+            ->setGroupBaseDn($config->base_dn)
+            ->setUserBaseDn($config->get('user_base_dn', $defaults->get('user_base_dn', $this->getGroupBaseDn())))
+            ->setGroupClass($config->get('group_class', $defaults->group_class))
+            ->setUserClass($config->get('user_class', $defaults->user_class))
+            ->setGroupNameAttribute($config->get('group_name_attribute', $defaults->group_name_attribute))
+            ->setUserNameAttribute($config->get('user_name_attribute', $defaults->user_name_attribute))
+            ->setGroupMemberAttribute($config->get('group_member_attribute', $defaults->group_member_attribute))
+            ->setGroupFilter($config->group_filter)
+            ->setUserFilter($config->user_filter)
+            ->setNestedGroupSearch((bool) $config->get('nested_group_search', $defaults->nested_group_search))
+            ->setDomain($defaults->get('domain', $config->domain));
+    }
+
+    /**
+     * Return the configuration defaults for an OpenLDAP environment
+     *
+     * @return  ConfigObject
+     */
+    public function getOpenLdapDefaults()
+    {
+        return new ConfigObject(array(
+            'group_class'               => 'group',
+            'user_class'                => 'inetOrgPerson',
+            'group_name_attribute'      => 'gid',
+            'user_name_attribute'       => 'uid',
+            'group_member_attribute'    => 'member',
+            'nested_group_search'       => '0'
+        ));
+    }
+
+    /**
+     * Return the configuration defaults for an ActiveDirectory environment
+     *
+     * @return  ConfigObject
+     */
+    public function getActiveDirectoryDefaults()
+    {
+        return new ConfigObject(array(
+            'group_class'               => 'group',
+            'user_class'                => 'user',
+            'group_name_attribute'      => 'sAMAccountName',
+            'user_name_attribute'       => 'sAMAccountName',
+            'group_member_attribute'    => 'member',
+            'nested_group_search'       => '0'
+        ));
+    }
+
+    /**
+     * Inspect if this LDAP User Group Backend is working as expected by probing the backend
+     *
+     * Try to bind to the backend and fetch a single group to check if:
+     * <ul>
+     *  <li>Connection credentials are correct and the bind is possible</li>
+     *  <li>At least one group exists</li>
+     *  <li>The specified groupClass has the property specified by groupNameAttribute</li>
+     * </ul>
+     *
+     * @return  Inspection  Inspection result
+     */
+    public function inspect()
+    {
+        $result = new Inspection('Ldap User Group Backend');
+
+        // inspect the used connection to get more diagnostic info in case the connection is not working
+        $result->write($this->ds->inspect());
+
+        try {
+            try {
+                $groupQuery = $this->ds
+                    ->select()
+                    ->from($this->groupClass, array($this->groupNameAttribute))
+                    ->setBase($this->groupBaseDn);
+
+                if ($this->groupFilter) {
+                    $groupQuery->setNativeFilter($this->groupFilter);
+                }
+
+                $res = $groupQuery->fetchRow();
+            } catch (LdapException $e) {
+                throw new AuthenticationException('Connection not possible', $e);
+            }
+
+            $result->write('Searching for: ' . sprintf(
+                'objectClass "%s" in DN "%s" (Filter: %s)',
+                $this->groupClass,
+                $this->groupBaseDn ?: $this->ds->getDn(),
+                $this->groupFilter ?: 'None'
+            ));
+
+            if ($res === false) {
+                throw new AuthenticationException('Error, no groups found in backend');
+            }
+
+            $result->write(sprintf('%d groups found in backend', $groupQuery->count()));
+
+            if (! isset($res->{$this->groupNameAttribute})) {
+                throw new AuthenticationException(
+                    'GroupNameAttribute "%s" not existing in objectClass "%s"',
+                    $this->groupNameAttribute,
+                    $this->groupClass
+                );
+            }
+        } catch (AuthenticationException $e) {
+            if (($previous = $e->getPrevious()) !== null) {
+                $result->error($previous->getMessage());
+            } else {
+                $result->error($e->getMessage());
+            }
+        } catch (Exception $e) {
+            $result->error(sprintf('Unable to validate backend: %s', $e->getMessage()));
+        }
+
+        return $result;
+    }
+}
diff --git a/library/Icinga/Authentication/UserGroup/UserGroupBackend.php b/library/Icinga/Authentication/UserGroup/UserGroupBackend.php
new file mode 100644
index 0000000..76fa2d0
--- /dev/null
+++ b/library/Icinga/Authentication/UserGroup/UserGroupBackend.php
@@ -0,0 +1,188 @@
+<?php
+/* Icinga Web 2 | (c) 2014 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\UserGroup;
+
+use Icinga\Application\Logger;
+use Icinga\Application\Icinga;
+use Icinga\Data\ConfigObject;
+use Icinga\Data\ResourceFactory;
+use Icinga\Exception\ConfigurationError;
+
+/**
+ * Factory for user group backends
+ */
+class UserGroupBackend
+{
+    /**
+     * The default user group backend types provided by Icinga Web 2
+     *
+     * @var array
+     */
+    protected static $defaultBackends = array(
+        'db',
+        'ldap',
+        'msldap'
+    );
+
+    /**
+     * The registered custom user group backends with their identifier as key and class name as value
+     *
+     * @var array
+     */
+    protected static $customBackends;
+
+    /**
+     * Register all custom user group backends from all loaded modules
+     */
+    public static function registerCustomUserGroupBackends()
+    {
+        if (static::$customBackends !== null) {
+            return;
+        }
+
+        static::$customBackends = array();
+        $providedBy = array();
+        foreach (Icinga::app()->getModuleManager()->getLoadedModules() as $module) {
+            foreach ($module->getUserGroupBackends() as $identifier => $className) {
+                if (array_key_exists($identifier, $providedBy)) {
+                    Logger::warning(
+                        'Cannot register user group backend of type "%s" provided by module "%s".'
+                        . ' The type is already provided by module "%s"',
+                        $identifier,
+                        $module->getName(),
+                        $providedBy[$identifier]
+                    );
+                } elseif (in_array($identifier, static::$defaultBackends)) {
+                    Logger::warning(
+                        'Cannot register user group backend of type "%s" provided by module "%s".'
+                        . ' The type is a default type provided by Icinga Web 2',
+                        $identifier,
+                        $module->getName()
+                    );
+                } else {
+                    $providedBy[$identifier] = $module->getName();
+                    static::$customBackends[$identifier] = $className;
+                }
+            }
+        }
+    }
+
+    /**
+     * Get config forms of all custom user group backends
+     */
+    public static function getCustomBackendConfigForms()
+    {
+        $customBackendConfigForms = [];
+        static::registerCustomUserGroupBackends();
+        foreach (self::$customBackends as $customBackendType => $customBackendClass) {
+            if (method_exists($customBackendClass, 'getConfigurationFormClass')) {
+                $customBackendConfigForms[$customBackendType] = $customBackendClass::getConfigurationFormClass();
+            }
+        }
+
+        return $customBackendConfigForms;
+    }
+
+    /**
+     * Return the class for the given custom user group backend
+     *
+     * @param   string  $identifier     The identifier of the custom user group backend
+     *
+     * @return  string|null             The name of the class or null in case there was no
+     *                                   backend found with the given identifier
+     *
+     * @throws  ConfigurationError      In case the class associated to the given identifier does not exist
+     */
+    protected static function getCustomUserGroupBackend($identifier)
+    {
+        static::registerCustomUserGroupBackends();
+        if (array_key_exists($identifier, static::$customBackends)) {
+            $className = static::$customBackends[$identifier];
+            if (! class_exists($className)) {
+                throw new ConfigurationError(
+                    'Cannot utilize user group backend of type "%s". Class "%s" does not exist',
+                    $identifier,
+                    $className
+                );
+            }
+
+            return $className;
+        }
+    }
+
+    /**
+     * Create and return a user group backend with the given name and given configuration applied to it
+     *
+     * @param   string          $name
+     * @param   ConfigObject    $backendConfig
+     *
+     * @return  UserGroupBackendInterface
+     *
+     * @throws  ConfigurationError
+     */
+    public static function create($name, ConfigObject $backendConfig)
+    {
+        if ($backendConfig->name !== null) {
+            $name = $backendConfig->name;
+        }
+
+        if (! ($backendType = strtolower($backendConfig->backend))) {
+            throw new ConfigurationError(
+                'Configuration for user group backend "%s" is missing the \'backend\' directive',
+                $name
+            );
+        }
+        if (in_array($backendType, static::$defaultBackends)) {
+            // The default backend check is the first one because of performance reasons:
+            // Do not attempt to load a custom user group backend unless it's actually required
+        } elseif (($customClass = static::getCustomUserGroupBackend($backendType)) !== null) {
+            $backend = new $customClass($backendConfig);
+            if (! is_a($backend, 'Icinga\Authentication\UserGroup\UserGroupBackendInterface')) {
+                throw new ConfigurationError(
+                    'Cannot utilize user group backend of type "%s".'
+                    . ' Class "%s" does not implement UserGroupBackendInterface',
+                    $backendType,
+                    $customClass
+                );
+            }
+
+            $backend->setName($name);
+            return $backend;
+        } else {
+            throw new ConfigurationError(
+                'Configuration for user group backend "%s" defines an invalid backend type.'
+                . ' Backend type "%s" is not supported',
+                $name,
+                $backendType
+            );
+        }
+
+        if ($backendConfig->resource === null) {
+            throw new ConfigurationError(
+                'Configuration for user group backend "%s" is missing the \'resource\' directive',
+                $name
+            );
+        }
+
+        $resourceConfig = ResourceFactory::getResourceConfig($backendConfig->resource);
+        if ($backendType === 'db' && $resourceConfig->db === 'mysql') {
+            $resourceConfig->charset = 'utf8mb4';
+        }
+
+        $resource = ResourceFactory::createResource($resourceConfig);
+        switch ($backendType) {
+            case 'db':
+                $backend = new DbUserGroupBackend($resource);
+                break;
+            case 'ldap':
+            case 'msldap':
+                $backend = new LdapUserGroupBackend($resource);
+                $backend->setConfig($backendConfig);
+                break;
+        }
+
+        $backend->setName($name);
+        return $backend;
+    }
+}
diff --git a/library/Icinga/Authentication/UserGroup/UserGroupBackendInterface.php b/library/Icinga/Authentication/UserGroup/UserGroupBackendInterface.php
new file mode 100644
index 0000000..cc9438f
--- /dev/null
+++ b/library/Icinga/Authentication/UserGroup/UserGroupBackendInterface.php
@@ -0,0 +1,56 @@
+<?php
+/* Icinga Web 2 | (c) 2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Authentication\UserGroup;
+
+use Icinga\User;
+
+/**
+ * Interface for user group backends
+ */
+interface UserGroupBackendInterface
+{
+    /**
+     * Set this backend's name
+     *
+     * @param   string  $name
+     *
+     * @return  $this
+     */
+    public function setName($name);
+
+    /**
+     * Return this backend's name
+     *
+     * @return  string
+     */
+    public function getName();
+
+    /**
+     * Return the groups the given user is a member of
+     *
+     * @param   User    $user
+     *
+     * @return  array
+     */
+    public function getMemberships(User $user);
+
+    /**
+     * Return the name of the backend that is providing the given user
+     *
+     * @param   string  $username
+     *
+     * @return  null|string     The name of the backend or null in case this information is not available
+     */
+    public function getUserBackendName($username);
+
+    /**
+     * Return this backend's configuration form class path
+     *
+     * This is not part of the interface to not break existing implementations.
+     * If you need a custom backend form, implement this method.
+     *
+     * @return string
+     */
+    //public static function getConfigurationFormClass();
+}