diff --git a/core/authorize.php b/core/authorize.php
index f347ba5..fe39394 100644
--- a/core/authorize.php
+++ b/core/authorize.php
@@ -48,10 +48,12 @@ function authorize_access_denied_page() {
  * The killswitch in settings.php overrides all else, otherwise, the user must
  * have access to the 'administer software updates' permission.
  *
- * @return
+ * @return bool
  *   TRUE if the current user can run authorize.php, and FALSE if not.
  */
 function authorize_access_allowed() {
+  require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
+  drupal_session_initialize();
   return settings()->get('allow_authorize_operations', TRUE) && user_access('administer software updates');
 }
 
@@ -65,7 +67,7 @@ function authorize_access_allowed() {
 
 // We prepare only a minimal bootstrap. This includes the database and
 // variables, however, so we have access to the class autoloader.
-drupal_bootstrap(DRUPAL_BOOTSTRAP_SESSION);
+drupal_bootstrap(DRUPAL_BOOTSTRAP_VARIABLES);
 
 // This must go after drupal_bootstrap(), which unsets globals!
 global $conf;
diff --git a/core/core.services.yml b/core/core.services.yml
index 04e6ec0..e70cd10 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -282,6 +282,10 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@settings']
+  route_enhancer.authentication:
+    class: Drupal\Core\Routing\Enhancer\AuthenticationEnhancer
+    tags:
+      - { name: route_enhancer, priority: 1000 }
   route_enhancer.content_controller:
     class: Drupal\Core\Routing\Enhancer\ContentControllerEnhancer
     arguments: ['@content_negotiation']
@@ -519,3 +523,19 @@ services:
     class: Zend\Feed\Writer\Extension\Threading\Renderer\Entry
   feed.writer.wellformedwebrendererentry:
     class: Zend\Feed\Writer\Extension\WellFormedWeb\Renderer\Entry
+  authentication:
+    class: Drupal\Core\Authentication\AuthenticationManager
+  authentication.cookie:
+    class: Drupal\Core\Authentication\Provider\Cookie
+    tags:
+      - { name: authentication_provider, priority: 0 }
+  authentication.http_basic:
+    class: Drupal\Core\Authentication\Provider\HttpBasic
+    arguments: ['@config.factory']
+    tags:
+      - { name: authentication_provider, priority: 100 }
+  authentication_subscriber:
+    class: Drupal\Core\EventSubscriber\AuthenticationSubscriber
+    tags:
+      - { name: event_subscriber }
+    arguments: ['@authentication']
diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index cf0e3dd..5fae68d 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -158,11 +158,6 @@
 const DRUPAL_BOOTSTRAP_VARIABLES = 4;
 
 /**
- * Sixth bootstrap phase: initialize session handling.
- */
-const DRUPAL_BOOTSTRAP_SESSION = 5;
-
-/**
  * Eighth bootstrap phase: load code for subsystems and modules.
  */
 const DRUPAL_BOOTSTRAP_CODE = 6;
@@ -1770,7 +1765,6 @@ function drupal_anonymous_user() {
  *   - DRUPAL_BOOTSTRAP_PAGE_CACHE: Tries to serve a cached page.
  *   - DRUPAL_BOOTSTRAP_DATABASE: Initializes the database layer.
  *   - DRUPAL_BOOTSTRAP_VARIABLES: Initializes the variable system.
- *   - DRUPAL_BOOTSTRAP_SESSION: Initializes session handling.
  *   - DRUPAL_BOOTSTRAP_CODE: Loads code for subsystems and modules.
  *   - DRUPAL_BOOTSTRAP_FULL: Fully loads Drupal. Validates and fixes input
  *     data.
@@ -1789,7 +1783,6 @@ function drupal_bootstrap($phase = NULL, $new_phase = TRUE) {
     DRUPAL_BOOTSTRAP_PAGE_CACHE,
     DRUPAL_BOOTSTRAP_DATABASE,
     DRUPAL_BOOTSTRAP_VARIABLES,
-    DRUPAL_BOOTSTRAP_SESSION,
     DRUPAL_BOOTSTRAP_CODE,
     DRUPAL_BOOTSTRAP_FULL,
   );
@@ -1839,11 +1832,6 @@ function drupal_bootstrap($phase = NULL, $new_phase = TRUE) {
           _drupal_bootstrap_variables();
           break;
 
-        case DRUPAL_BOOTSTRAP_SESSION:
-          require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
-          drupal_session_initialize();
-          break;
-
         case DRUPAL_BOOTSTRAP_CODE:
           require_once __DIR__ . '/common.inc';
           _drupal_bootstrap_code();
@@ -1911,7 +1899,7 @@ function drupal_get_user_timezone() {
   global $user;
   $config = config('system.timezone');
 
-  if ($config->get('user.configurable') && $user->uid && $user->timezone) {
+  if ($user && $config->get('user.configurable') && $user->uid && $user->timezone) {
     return $user->timezone;
   }
   else {
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 1ecd819..5f2ccc7 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1746,6 +1746,8 @@ function install_load_profile(&$install_state) {
  */
 function install_bootstrap_full() {
   drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
+  require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
+  drupal_session_initialize();
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationManager.php b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
new file mode 100644
index 0000000..f458ffe
--- /dev/null
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationManager.php
@@ -0,0 +1,209 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Authentication\AuthenticationManager.
+ */
+
+namespace Drupal\Core\Authentication;
+
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Cmf\Component\Routing\RouteObjectInterface;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+
+/**
+ * Manager for authentication.
+ *
+ * On each request, let all authentication providers try to authenticate the
+ * user. The provider are iterated according to their priority and the first
+ * provider detecting credentials for his method will become the triggered
+ * provider. No further provider will get triggered.
+ *
+ * If no provider felt responsible the manager assumes that the least
+ * prioritized should have and therefore is the triggered provider and the user
+ * is set to anonymous.
+ */
+class AuthenticationManager implements AuthenticationProviderInterface {
+
+  /**
+   * Array of all registered authentication providers, keyed by ID.
+   *
+   * @var array
+   */
+  protected $providers;
+
+  /**
+   * Array of all providers and their priority.
+   *
+   * @var array
+   */
+  protected $providerOrders;
+
+  /**
+   * Sorted list of registered providers.
+   *
+   * @var array
+   */
+  protected $sortedProviders;
+
+  /**
+   * Id of the provider that authenticated the user.
+   *
+   * @var string
+   */
+  protected $triggeredProviderId = '';
+
+  /**
+   * Add provider to the array of registered providers.
+   *
+   * @param string $provider_id
+   *   Identifier of the provider.
+   * @param \Drupal\Core\Authentication\AuthenticationProviderInterface $provider
+   *   The provider object.
+   * @param int $priority
+   *   The providers priority.
+   */
+  public function addProvider($provider_id, AuthenticationProviderInterface $provider, $priority = 0) {
+    $provider_id = substr($provider_id, strlen('authentication.'));
+
+    $this->providers[$provider_id] = $provider;
+    $this->providerOrders[$priority][$provider_id] = $provider;
+    // Force the builders to be re-sorted.
+    $this->sortedProviders = NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(Request $request) {
+    return TRUE;
+  }
+
+  /**
+   * Authenticate user.
+   *
+   * Iterate the available providers according th their priority.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object.
+   *
+   * @return \Drupal\Core\Session\AccountInterface
+   *   The account interface of the authenticated user. Defaults to a anonymous.
+   */
+  public function authenticate(Request $request) {
+    global $user;
+
+    $account = NULL;
+
+    // Iterate the availlable providers.
+    foreach ($this->getSortedProviders() as $provider_id => $provider) {
+      if ($provider->applies($request)) {
+        // Provider felt responsible for this request – trigger authentication.
+        $account = $provider->authenticate($request);
+        $this->triggeredProviderId = $provider_id;
+        break;
+      }
+    }
+
+    // No provider returned a valid account - assume anonymous.
+    if (!$account) {
+      $account = drupal_anonymous_user();
+    }
+
+    // No provider felt responsible – assume the one with the least priority
+    // should have.
+    if (!$this->triggeredProviderId) {
+      $this->triggeredProviderId = $this->defaultProviderId();
+    }
+
+    // Save the authenticated account for later access. The global $user object
+    // is included for backward compatibility only and should be considered
+    // deprecated.
+    $user = $account;
+    $request->attributes->set('session', $account);
+
+    // Save the ID of the triggered provider to the request.
+    $request->attributes->set('_authentication_provider', $this->triggeredProviderId);
+
+    return $account;
+  }
+
+  /**
+   * Returns the default provider ID.
+   *
+   * The default provider is the one with the lowest registered priority.
+   *
+   * @return string
+   *   The ID of the default provider.
+   */
+  protected function defaultProviderId() {
+    $providers = $this->getSortedProviders();
+    $provider_ids = array_keys($providers);
+    return end($provider_ids);
+  }
+
+  /**
+   * Returns the sorted array of authentication providers.
+   *
+   * @return array
+   *   An array of authentication provider objects.
+   */
+  protected function getSortedProviders() {
+    if (!isset($this->sortedProviders)) {
+      // Sort the builders according to priority.
+      krsort($this->providerOrders);
+      // Merge nested providers from $this->providers into $this->sortedProviders.
+      $this->sortedProviders = array();
+      foreach ($this->providerOrders as $providers) {
+        $this->sortedProviders = array_merge($this->sortedProviders, $providers);
+      }
+    }
+    return $this->sortedProviders;
+  }
+
+  /**
+   * Cleans up the authentication.
+   *
+   * Allow the triggered provider to clean up before the response is sent, e.g.
+   * trigger a session commit.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object.
+   *
+   * @see \Drupal\Core\Authentication\Provider\Cookie::cleanup()
+   */
+  public function cleanup(Request $request) {
+    if (empty($this->providers[$this->triggeredProviderId])) {
+      return;
+    }
+    $this->providers[$this->triggeredProviderId]->cleanup($request);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function handleException(GetResponseForExceptionEvent $event) {
+    $request = $event->getRequest();
+
+    // Legacy routes won't have a Route object; they have drupal_menu_item
+    // instead.  Assume those were authenticated by cookie, because the legacy
+    // router didn't support anything else.
+    // @todo Remove this check once the old router is fully removed.
+    if ($request->attributes->has('drupal_menu_item')) {
+      $auth_providers = array('cookie');
+    }
+    else {
+      $route = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT);
+      $auth_providers = ($route && $route->getOption('_auth')) ? $route->getOption('_auth') : array($this->defaultProviderId());
+    }
+
+    // While any provider may authenticate a request, only the first listed
+    // by a route may give a challenge for a failed request to allow the user
+    // to login.
+    $allowed_providers = array_intersect($auth_providers, array_keys($this->providers));
+
+    if ($allowed_providers) {
+      $this->providers[current($allowed_providers)]->handleException($event);
+    }
+  }
+}
diff --git a/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php b/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php
new file mode 100644
index 0000000..31aafe9
--- /dev/null
+++ b/core/lib/Drupal/Core/Authentication/AuthenticationProviderInterface.php
@@ -0,0 +1,67 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Authentication\AuthenticationProviderInterface.
+ */
+
+namespace Drupal\Core\Authentication;
+
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+
+/**
+ * Interface for authentication providers.
+ */
+interface AuthenticationProviderInterface {
+
+  /**
+   * Declares whether the provider applies to a specific request or not.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object.
+   *
+   * @return bool
+   *   TRUE if the provider applies to the passed request, FALSE otherwise.
+   */
+  public function applies(Request $request);
+
+  /**
+   * Authenticates the user.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object.
+   *
+   * @return \Drupal\Core\Session\AccountInterface|null
+   *   AccountInterface - in case of a successful authentication.
+   *   FALSE - in case where authentication failed.
+   */
+  public function authenticate(Request $request);
+
+  /**
+   * Do cleanup.
+   *
+   * Allow the authentication provider to clean up before the response is sent.
+   * This is uses for instance in \Drupal\Core\Authentication\Provider\Cookie to
+   * ensure the session gets committed.
+   *
+   * @param Request $request
+   *   The request object.
+   */
+  public function cleanup(Request $request);
+
+  /**
+   * Handle exception.
+   *
+   * In case exception has happened we allow authentication providers react.
+   * Used in \Drupal\Core\Authentication\Provider\HttpBasic to set up headers to
+   * prompt login.
+   *
+   * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
+   *
+   * @return bool
+   *   TRUE - exception handled. No need to run through other providers.
+   *   FALSE - no actions have been done. Run through other providers.
+   */
+  public function handleException(GetResponseForExceptionEvent $event);
+}
diff --git a/core/lib/Drupal/Core/Authentication/Provider/Cookie.php b/core/lib/Drupal/Core/Authentication/Provider/Cookie.php
new file mode 100644
index 0000000..ae108dc
--- /dev/null
+++ b/core/lib/Drupal/Core/Authentication/Provider/Cookie.php
@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Authentication\Provider\Cookie.
+ */
+
+namespace Drupal\Core\Authentication\Provider;
+
+use Drupal\Core\Authentication\AuthenticationProviderInterface;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+
+/**
+ * Cookie based authentication provider.
+ */
+class Cookie implements AuthenticationProviderInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(Request $request) {
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function authenticate(Request $request) {
+    // Global $user is deprecated, but the session system is still based on it.
+    global $user;
+    require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
+    drupal_session_initialize();
+    if (drupal_session_started()) {
+      return $user;
+    }
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function cleanup(Request $request) {
+    drupal_session_commit();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function handleException(GetResponseForExceptionEvent $event) {
+    return FALSE;
+  }
+}
diff --git a/core/lib/Drupal/Core/Authentication/Provider/HttpBasic.php b/core/lib/Drupal/Core/Authentication/Provider/HttpBasic.php
new file mode 100644
index 0000000..50ca04f
--- /dev/null
+++ b/core/lib/Drupal/Core/Authentication/Provider/HttpBasic.php
@@ -0,0 +1,86 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Authentication\Provider\HttpBasic.
+ */
+
+namespace Drupal\Core\Authentication\Provider;
+
+use \Drupal\Component\Utility\String;
+use Drupal\Core\Authentication\AuthenticationProviderInterface;
+use Drupal\Core\Config\Config;
+use Drupal\Core\Config\ConfigFactory;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+use Symfony\Component\HttpKernel\Exception\UnauthorizedHttpException;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+
+/**
+ * HTTP Basic authentication provider.
+ */
+class HttpBasic implements AuthenticationProviderInterface {
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory
+   */
+  protected $configFactory;
+
+  /**
+   * Constructs a HTTP basic authentication provider object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactory $config_factory
+   *   The config factory.
+   */
+  public function __construct(ConfigFactory $config_factory) {
+    $this->configFactory = $config_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(Request $request) {
+    $username = $request->headers->get('PHP_AUTH_USER');
+    $password = $request->headers->get('PHP_AUTH_PW');
+    return isset($username) && isset($password);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function authenticate(Request $request) {
+    $username = $request->headers->get('PHP_AUTH_USER');
+    $password = $request->headers->get('PHP_AUTH_PW');
+    $uid = user_authenticate($username, $password);
+    if ($uid) {
+      return user_load($uid);
+    }
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function cleanup(Request $request) {}
+
+  /**
+   * {@inheritdoc}
+   */
+  public function handleException(GetResponseForExceptionEvent $event) {
+    $exception = $event->getException();
+    if (user_is_anonymous() && $exception instanceof AccessDeniedHttpException) {
+      if (!$this->applies($event->getRequest())) {
+        $site_name = $this->configFactory->get('system.site')->get('name');
+        global $base_url;
+        $challenge = String::format('Basic realm="@realm"', array(
+          '@realm' => !empty($site_name) ? $site_name : $base_url,
+        ));
+        $event->setException(new UnauthorizedHttpException($challenge, 'No authentication credentials provided.', $exception));
+      }
+      return TRUE;;
+    }
+    return FALSE;
+  }
+}
diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index c9a661b..9e7d77e 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -42,12 +42,12 @@ public function __construct(ContentNegotiation $negotiation) {
   /**
    * Handles an exception on a request.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\HttpKernel\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request that generated the exception.
    *
-   * @return Symfony\Component\HttpFoundation\Response
+   * @return \Symfony\Component\HttpFoundation\Response
    *   A response object to be sent to the server.
    */
   public function execute(FlattenException $exception, Request $request) {
@@ -57,7 +57,7 @@ public function execute(FlattenException $exception, Request $request) {
       return $this->$method($exception, $request);
     }
 
-    return new Response('A fatal error occurred: ' . $exception->getMessage(), $exception->getStatusCode());
+    return new Response('A fatal error occurred: ' . $exception->getMessage(), $exception->getStatusCode(), $exception->getHeaders());
   }
 
   /**
diff --git a/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
index 9af0c74..b5aaa93 100644
--- a/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -18,6 +18,7 @@
 use Drupal\Core\DependencyInjection\Compiler\RegisterServicesForDestructionPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterStringTranslatorsPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterBreadcrumbBuilderPass;
+use Drupal\Core\DependencyInjection\Compiler\RegisterAuthenticationPass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Reference;
@@ -67,6 +68,8 @@ public function build(ContainerBuilder $container) {
     // Add the compiler pass that will process the tagged breadcrumb builder
     // services.
     $container->addCompilerPass(new RegisterBreadcrumbBuilderPass());
+    // Add the compiler pass that will process tagged authentication services.
+    $container->addCompilerPass(new RegisterAuthenticationPass());
   }
 
   /**
diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAuthenticationPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAuthenticationPass.php
new file mode 100644
index 0000000..dd975a9
--- /dev/null
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterAuthenticationPass.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\DependencyInjection\Compiler\RegisterAuthenticationPass.
+ */
+
+namespace Drupal\Core\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+
+/**
+ * Adds services tagged 'authentication_provider'.
+ */
+class RegisterAuthenticationPass implements CompilerPassInterface {
+
+  /**
+   * Adds authentication providers to the authentication manager.
+   *
+   * Check for services tagged with 'authentication_provider' and add them to
+   * the authentication manager.
+   *
+   * @see \Drupal\Core\Authentication\AuthenticationManager
+   * @see \Drupal\Core\Authentication\AuthenticationProviderInterface
+   */
+  public function process(ContainerBuilder $container) {
+    if (!$container->hasDefinition('authentication')) {
+      return;
+    }
+    // Get the authentication manager.
+    $matcher = $container->getDefinition('authentication');
+    // Iterate all autentication providers and add them to the manager.
+    foreach ($container->findTaggedServiceIds('authentication_provider') as $id => $attributes) {
+      $priority = isset($attributes[0]['priority']) ? $attributes[0]['priority'] : 0;
+      $matcher->addMethodCall('addProvider', array(
+        $id,
+        new Reference($id),
+        $priority,
+      ));
+    }
+  }
+}
diff --git a/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php
new file mode 100644
index 0000000..f9cf972
--- /dev/null
+++ b/core/lib/Drupal/Core/EventSubscriber/AuthenticationSubscriber.php
@@ -0,0 +1,94 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\EventSubscriber\AuthenticationSubscriber.
+ */
+
+namespace Drupal\Core\EventSubscriber;
+
+use Drupal\Core\Authentication\AuthenticationProviderInterface;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+use Symfony\Component\HttpKernel\KernelEvents;
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Authentication subscriber.
+ *
+ * Trigger authentication and cleanup during the request.
+ */
+class AuthenticationSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Authentication manager.
+   *
+   * @var AuthenticationProviderInterface
+   */
+  protected $authenticationManager;
+
+  /**
+   * Keep authentication manager as private variable.
+   *
+   * @param AuthenticationProviderInterface $authentication_manager
+   *   The authentication manager.
+   */
+  public function __construct(AuthenticationProviderInterface $authentication_manager) {
+    $this->authenticationManager = $authentication_manager;
+  }
+
+  /**
+   * Authenticates user on request.
+   *
+   * @see \Drupal\Core\Authentication\AuthenticationProviderInterface::authenticate()
+   */
+  public function onKernelRequestAuthenticate(GetResponseEvent $event) {
+    if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST) {
+      $request = $event->getRequest();
+      $this->authenticationManager->authenticate($request);
+    }
+  }
+
+  /**
+   * Triggers authentication clean up on response.
+   *
+   * @see \Drupal\Core\Authentication\AuthenticationProviderInterface::cleanup()
+   */
+  public function onRespond(FilterResponseEvent $event) {
+    if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST) {
+      $request = $event->getRequest();
+
+      $this->authenticationManager->cleanup($request);
+    }
+  }
+
+  /**
+   * Pass exception handling to authentication manager.
+   *
+   * @param GetResponseForExceptionEvent $event
+   */
+  public function onException(GetResponseForExceptionEvent $event) {
+    if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST) {
+      $this->authenticationManager->handleException($event);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * The priority for request must be higher than the highest event subscriber
+   * accessing the global $user.
+   * The priority for the response must be as low as possible allowing e.g the
+   * Cookie provider to send all relevant session data to the user.
+   */
+  public static function getSubscribedEvents() {
+    // Priority must be higher than LanguageRequestSubscriber as LanguageManager
+    // access global $user in case language module enabled.
+    $events[KernelEvents::REQUEST][] = array('onKernelRequestAuthenticate', 300);
+    $events[KernelEvents::RESPONSE][] = array('onRespond', 0);
+    $events[KernelEvents::EXCEPTION][] = array('onException', 0);
+    return $events;
+  }
+}
diff --git a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
index 0b9bbad..98eef05 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
@@ -91,8 +91,6 @@ public function onRespond(FilterResponseEvent $event) {
     // @todo Revisit whether or not this is still appropriate now that the
     //   Response object does its own cache control processing and we intend to
     //   use partial page caching more extensively.
-    // Commit the user session, if needed.
-    drupal_session_commit();
 
     // Attach globally-declared headers to the response object so that Symfony
     // can send them for us correctly.
diff --git a/core/lib/Drupal/Core/Routing/Enhancer/AuthenticationEnhancer.php b/core/lib/Drupal/Core/Routing/Enhancer/AuthenticationEnhancer.php
new file mode 100644
index 0000000..9a342fc
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/Enhancer/AuthenticationEnhancer.php
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Routing\Enhancer\AuthenticationEnhancer.
+ */
+
+namespace Drupal\Core\Routing\Enhancer;
+
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Cmf\Component\Routing\Enhancer\RouteEnhancerInterface;
+use Drupal\Core\ContentNegotiation;
+use Symfony\Cmf\Component\Routing\RouteObjectInterface;
+
+/**
+ * Authentication cleanup for incoming routes.
+ *
+ * The authentication system happens before routing, so all authentication
+ * providers will attempt to authorize a user. However, not all routes allow
+ * all authentication mechanisms.  Instead, we check if the used provider is
+ * valid for the matched route and if not, force the user to anonymous.
+ */
+class AuthenticationEnhancer implements RouteEnhancerInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function enhance(array $defaults, Request $request) {
+    $auth_provider_triggered = $request->attributes->get('_authentication_provider');
+    if (!empty($auth_provider_triggered)) {
+      $route = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT);
+      $auth_providers = ($route && $route->getOption('_auth')) ? $route->getOption('_auth') : array();
+      if (!empty($auth_providers)) {
+        // If the request was authenticated with a non-permitted provider,
+        // force the user back to anonymous.
+        if (!in_array($auth_provider_triggered, $auth_providers)) {
+          $request->attributes->set('session', drupal_anonymous_user());
+        }
+      }
+    }
+    return $defaults;
+  }
+
+}
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index d3ba7b3..975788a 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -876,6 +876,7 @@ protected function prepareEnvironment() {
     $this->originalUser = isset($user) ? clone $user : NULL;
 
     // Ensure that the current session is not changed by the new environment.
+    require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
     drupal_save_session(FALSE);
     // Run all tests as a anonymous user by default, web tests will replace that
     // during the test set up.
diff --git a/core/modules/system/lib/Drupal/system/Tests/Authentication/HttpBasicTest.php b/core/modules/system/lib/Drupal/system/Tests/Authentication/HttpBasicTest.php
new file mode 100644
index 0000000..dea9359
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/Authentication/HttpBasicTest.php
@@ -0,0 +1,86 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Authentication\HttpBasicTest.
+ */
+
+namespace Drupal\system\Tests\Authentication;
+
+use Drupal\Core\Authentication\Provider\HttpBasic;
+use Drupal\simpletest\WebTestBase;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Test for http basic authentication.
+ */
+class HttpBasicTest extends WebTestBase {
+
+  /**
+   * Modules enabled for all tests.
+   *
+   * @var array
+   */
+  public static $modules = array('router_test');
+
+  public static function getInfo() {
+    return array(
+      'name' => 'HttpBasic authentication',
+      'description' => 'Tests for HttpBasic authentication provider.',
+      'group' => 'Authentication',
+    );
+  }
+
+  /**
+   * Test http basic authentication.
+   */
+  public function testHttpBasic() {
+    $account = $this->drupalCreateUser();
+
+    $this->basicAuthGet('router_test/test11', $account->name, $account->pass_raw);
+    $this->assertText($account->name, 'Account name is displayed.');
+    $this->assertResponse('200', 'HTTP response is OK');
+    $this->curlClose();
+
+    $this->basicAuthGet('router_test/test11', $account->name, $this->randomName());
+    $this->assertNoText($account->name, 'Bad basic auth credentials do not authenticate the user.');
+    $this->assertResponse('200', 'HTTP response is OK');
+    $this->curlClose();
+
+    $this->drupalGet('router_test/test11');
+    $this->assertResponse('401', 'Not authenticated on the route that allows only http_basic. Prompt to authenticate received.');
+  }
+
+  /**
+   * Does HTTP basic auth request.
+   *
+   * We do not use \Drupal\simpletest\WebTestBase::drupalGet because we need to
+   * set curl settings for basic authentication.
+   *
+   * @param string $path
+   *   The request path.
+   * @param string $username
+   *   The user name to authenticate with.
+   * @param string $password
+   *   The password.
+   *
+   * @return string
+   *   Curl output.
+   */
+  protected function basicAuthGet($path, $username, $password) {
+    $out = $this->curlExec(
+      array(
+        CURLOPT_HTTPGET => TRUE,
+        CURLOPT_URL => url($path, array('absolute' => TRUE)),
+        CURLOPT_NOBODY => FALSE,
+        CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
+        CURLOPT_USERPWD => $username . ':' . $password,
+      )
+    );
+
+    $this->verbose('GET request to: ' . $path .
+      '<hr />' . $out);
+
+    return $out;
+  }
+}
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
index b613121..9de96b0 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
@@ -93,6 +93,10 @@ protected function setUp() {
     // Load the Update API.
     require_once DRUPAL_ROOT . '/core/includes/update.inc';
 
+    // Load Session API.
+    require_once DRUPAL_ROOT . '/core/includes/session.inc';
+    drupal_session_initialize();
+
     // Reset flags.
     $this->upgradedSite = FALSE;
     $this->upgradeErrors = array();
diff --git a/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestContent.php b/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestContent.php
index 56d567b..22a07cf 100644
--- a/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestContent.php
+++ b/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestContent.php
@@ -19,4 +19,15 @@ public function test1() {
     return 'abcde';
   }
 
+  /**
+   * Provides example content for route specific authentication.
+   *
+   * @returns string
+   *   The user name of the current logged in user.
+   */
+  public function test11() {
+    global $user;
+    return isset($user->name) ? $user->name : '';
+  }
+
 }
diff --git a/core/modules/system/tests/modules/router_test/router_test.routing.yml b/core/modules/system/tests/modules/router_test/router_test.routing.yml
index 2a989df..9e481de 100644
--- a/core/modules/system/tests/modules/router_test/router_test.routing.yml
+++ b/core/modules/system/tests/modules/router_test/router_test.routing.yml
@@ -60,3 +60,10 @@ router_test_10:
     _content: '\Drupal\router_test\TestContent::test1'
   requirements:
     _access: 'TRUE'
+
+router_test_11:
+  pattern: '/router_test/test11'
+  options:
+    _auth: [ 'http_basic' ]
+  defaults:
+    _content: '\Drupal\router_test\TestContent::test11'
diff --git a/core/modules/system/tests/modules/session_test/lib/Drupal/session_test/EventSubscriber/SessionTestSubscriber.php b/core/modules/system/tests/modules/session_test/lib/Drupal/session_test/EventSubscriber/SessionTestSubscriber.php
index 45234a8..44e2882 100644
--- a/core/modules/system/tests/modules/session_test/lib/Drupal/session_test/EventSubscriber/SessionTestSubscriber.php
+++ b/core/modules/system/tests/modules/session_test/lib/Drupal/session_test/EventSubscriber/SessionTestSubscriber.php
@@ -65,7 +65,7 @@ public function onKernelResponseSessionTest(FilterResponseEvent $event) {
    */
   static function getSubscribedEvents() {
     $events[KernelEvents::RESPONSE][] = array('onKernelResponseSessionTest', 300);
-    $events[KernelEvents::REQUEST][] = array('onKernelRequestSessionTest', 300);
+    $events[KernelEvents::REQUEST][] = array('onKernelRequestSessionTest', 100);
     return $events;
   }
 
diff --git a/core/modules/user/lib/Drupal/user/Access/RoleAccessCheck.php b/core/modules/user/lib/Drupal/user/Access/RoleAccessCheck.php
index 7940bf3..928af4d 100644
--- a/core/modules/user/lib/Drupal/user/Access/RoleAccessCheck.php
+++ b/core/modules/user/lib/Drupal/user/Access/RoleAccessCheck.php
@@ -34,9 +34,7 @@ public function access(Route $route, Request $request) {
     // Requirements just allow strings, so this might be a comma separated list.
     $rid_string = $route->getRequirement('_role');
 
-    // @todo Replace the role check with a correctly injected and session-using
-    //   alternative.
-    $account = $GLOBALS['user'];
+    $account = $request->attributes->get('session');
 
     $explode_and = array_filter(array_map('trim', explode('+', $rid_string)));
     if (count($explode_and) > 1) {
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index e7ee37a..e9785f6 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -470,7 +470,9 @@ function user_access($string, AccountInterface $account = NULL) {
   global $user;
 
   if (!isset($account)) {
-    $account = $user;
+    // In the installer request session is not set, so we have to fall back
+    // to the global $user. In all other cases the session key is preferred.
+    $account = Drupal::request()->attributes->get('session') ?: $user;
   }
 
   // Make sure we are working with the BC decorator.
diff --git a/core/update.php b/core/update.php
index b73e3ce..f97a973 100644
--- a/core/update.php
+++ b/core/update.php
@@ -427,7 +427,9 @@ function update_check_requirements($skip_warnings = FALSE) {
 update_prepare_d8_bootstrap();
 
 // Determine if the current user has access to run update.php.
-drupal_bootstrap(DRUPAL_BOOTSTRAP_SESSION);
+drupal_bootstrap(DRUPAL_BOOTSTRAP_VARIABLES);
+require_once DRUPAL_ROOT . '/' . settings()->get('session_inc', 'core/includes/session.inc');
+drupal_session_initialize();
 
 // A request object from the HTTPFoundation to tell us about the request.
 // @todo These two lines were copied from index.php which has its own todo about