Issue #287292 by almaudoh, mr.baileys, drewish, Berdir, znerol, boombatower, dawehner, jpetso, floretan: Add functionality to impersonate a user

core/core.services.yml

@@ -163,7 +163,7 @@ services:
     arguments: ['@typed_data_manager']
   cron:
     class: Drupal\Core\Cron
-    arguments: ['@module_handler', '@lock', '@queue', '@state', '@current_user', '@session_manager', '@logger.channel.cron', '@plugin.manager.queue_worker']
+    arguments: ['@module_handler', '@lock', '@queue', '@state', '@account_switcher', '@logger.channel.cron', '@plugin.manager.queue_worker']
   diff.formatter:
     class: Drupal\Core\Diff\DiffFormatter
     arguments: ['@config.factory']
@@ -1012,6 +1012,9 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@authentication']
+  account_switcher:
+    class: Drupal\Core\Session\AccountSwitcher
+    arguments: ['@current_user', '@session_manager']
   current_user:
     class: Drupal\Core\Session\AccountProxy
     arguments: ['@authentication', '@request_stack']

core/lib/Drupal/Core/Cron.php

@@ -12,9 +12,8 @@ use Drupal\Core\Queue\QueueWorkerManagerInterface;
 use Drupal\Core\State\StateInterface;
 use Drupal\Core\Lock\LockBackendInterface;
 use Drupal\Core\Queue\QueueFactory;
-use Drupal\Core\Session\AccountProxyInterface;
 use Drupal\Core\Session\AnonymousUserSession;
-use Drupal\Core\Session\SessionManagerInterface;
+use Drupal\Core\Session\AccountSwitcherInterface;
 use Drupal\Core\Queue\SuspendQueueException;
 use Psr\Log\LoggerInterface;
 
@@ -52,18 +51,11 @@ class Cron implements CronInterface {
   protected $state;
 
   /**
-   * The current user.
+   * The account switcher service.
    *
-   * @var \Drupal\Core\Session\AccountProxyInterface
+   * @var \Drupal\Core\Session\AccountSwitcherInterface
    */
-  protected $currentUser;
+  protected $accountSwitcher;
-
-  /**
-   * The session manager.
-   *
-   * @var \Drupal\Core\Session\SessionManagerInterface
-   */
-  protected $sessionManager;
 
   /**
    * A logger instance.
@@ -90,22 +82,19 @@ class Cron implements CronInterface {
    *   The queue service.
    * @param \Drupal\Core\State\StateInterface $state
    *   The state service.
-   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
+   * @param \Drupal\Core\Session\AccountSwitcherInterface $account_switcher
-   *    The current user.
+   *    The account switching service.
-   * @param \Drupal\Core\Session\SessionManagerInterface $session_manager
-   *   The session manager.
    * @param \Psr\Log\LoggerInterface $logger
    *   A logger instance.
    * @param \Drupal\Core\Queue\QueueWorkerManagerInterface
    *   The queue plugin manager.
    */
-  public function __construct(ModuleHandlerInterface $module_handler, LockBackendInterface $lock, QueueFactory $queue_factory, StateInterface $state, AccountProxyInterface $current_user, SessionManagerInterface $session_manager, LoggerInterface $logger, QueueWorkerManagerInterface $queue_manager) {
+  public function __construct(ModuleHandlerInterface $module_handler, LockBackendInterface $lock, QueueFactory $queue_factory, StateInterface $state, AccountSwitcherInterface $account_switcher, LoggerInterface $logger, QueueWorkerManagerInterface $queue_manager) {
     $this->moduleHandler = $module_handler;
     $this->lock = $lock;
     $this->queueFactory = $queue_factory;
     $this->state = $state;
-    $this->currentUser = $current_user;
+    $this->accountSwitcher = $account_switcher;
-    $this->sessionManager = $session_manager;
     $this->logger = $logger;
     $this->queueManager = $queue_manager;
   }
@@ -117,14 +106,9 @@ class Cron implements CronInterface {
     // Allow execution to continue even if the request gets cancelled.
     @ignore_user_abort(TRUE);
 
-    // Prevent session information from being saved while cron is running.
-    $original_session_saving = $this->sessionManager->isEnabled();
-    $this->sessionManager->disable();
-
     // Force the current user to anonymous to ensure consistent permissions on
     // cron runs.
-    $original_user = $this->currentUser->getAccount();
+    $this->accountSwitcher->switchTo(new AnonymousUserSession());
-    $this->currentUser->setAccount(new AnonymousUserSession());
 
     // Try to allocate enough time to run all the hook_cron implementations.
     drupal_set_time_limit(240);
@@ -151,10 +135,7 @@ class Cron implements CronInterface {
     $this->processQueues();
 
     // Restore the user.
-    $this->currentUser->setAccount($original_user);
+    $this->accountSwitcher->switchBack();
-    if ($original_session_saving) {
-      $this->sessionManager->enable();
-    }
 
     return $return;
   }

core/lib/Drupal/Core/Session/AccountSwitcher.php

@@ -0,0 +1,96 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Session\AccountSwitcher.
+ */
+
+namespace Drupal\Core\Session;
+
+/**
+ * An implementation of AccountSwitcherInterface.
+ *
+ * This allows for safe switching of user accounts by ensuring that session
+ * data for one user is not leaked in to others. It also provides a stack that
+ * allows reverting to a previous user after switching.
+ */
+class AccountSwitcher implements AccountSwitcherInterface {
+
+  /**
+   * A stack of previous overridden accounts.
+   *
+   * @var \Drupal\Core\Session\AccountInterface[]
+   */
+  protected $accountStack = array();
+
+  /**
+   * The current user service.
+   *
+   * @var \Drupal\Core\Session\AccountProxyInterface
+   */
+  protected $currentUser = array();
+
+  /**
+   * The session manager.
+   *
+   * @var \Drupal\Core\Session\SessionManagerInterface
+   */
+  protected $sessionManager;
+
+  /**
+   * The original state of session saving prior to account switching.
+   *
+   * @var bool
+   */
+  protected $originalSessionSaving;
+
+  /**
+   * Constructs a new AccountSwitcher.
+   *
+   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
+   *   The current user service.
+   * @param \Drupal\Core\Session\SessionManagerInterface $session_manager
+   *   The session manager.
+   */
+  public function __construct(AccountProxyInterface $current_user, SessionManagerInterface $session_manager) {
+    $this->currentUser = $current_user;
+    $this->sessionManager = $session_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function switchTo(AccountInterface $account) {
+    // Prevent session information from being saved and push previous account.
+    if (!isset($this->originalSessionSaving)) {
+      // Ensure that only the first session saving status is saved.
+      $this->originalSessionSaving = $this->sessionManager->isEnabled();
+    }
+    $this->sessionManager->disable();
+    array_push($this->accountStack, $this->currentUser->getAccount());
+    $this->currentUser->setAccount($account);
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function switchBack() {
+    // Restore the previous account from the stack.
+    if (!empty($this->accountStack)) {
+      $this->currentUser->setAccount(array_pop($this->accountStack));
+    }
+    else {
+      throw new \RuntimeException('No more accounts to revert to.');
+    }
+    // Restore original session saving status if all account switches are
+    // reverted.
+    if (empty($this->accountStack)) {
+      if ($this->originalSessionSaving) {
+        $this->sessionManager->enable();
+      }
+    }
+    return $this;
+  }
+
+}

core/lib/Drupal/Core/Session/AccountSwitcherInterface.php

@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Session\AccountSwitcherInterface.
+ */
+
+namespace Drupal\Core\Session;
+
+/**
+ * Defines an interface for a service for safe account switching.
+ *
+ * @ingroup user_api
+ */
+interface AccountSwitcherInterface {
+
+  /**
+   * Safely switches to another account.
+   *
+   * Each invocation of AccountSwitcherInterface::switchTo() must be
+   * matched by a corresponding invocation of
+   * AccountSwitcherInterface::switchBack() in the same function.
+   *
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The account to switch to.
+   *
+   * @return \Drupal\Core\Session\AccountSwitcherInterface
+   *   $this.
+   */
+  public function switchTo(AccountInterface $account);
+
+  /**
+   * Reverts back to a previous account after switching.
+   *
+   * @return \Drupal\Core\Session\AccountSwitcherInterface
+   *   $this.
+   *
+   * @throws \RuntimeException
+   *   When there are no more account switches to revert.
+   */
+  public function switchBack();
+
+}

core/modules/system/src/Tests/Session/AccountSwitcherTest.php

@@ -0,0 +1,72 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\system\Tests\Session\AccountSwitcherTest.
+ */
+
+namespace Drupal\system\Tests\Session;
+
+use Drupal\Core\Session\UserSession;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Test case for account switching.
+ *
+ * @group Session
+ */
+class AccountSwitcherTest extends KernelTestBase {
+
+  public function testAccountSwitching() {
+    $session_manager = $this->container->get('session_manager');
+    $user = $this->container->get('current_user');
+    $switcher = $this->container->get('account_switcher');
+    $original_user = $user->getAccount();
+    $original_session_saving = $session_manager->isEnabled();
+
+    // Switch to user with uid 2.
+    $switcher->switchTo(new UserSession(array('uid' => 2)));
+
+    // Verify that the active user has changed, and that session saving is
+    // disabled.
+    $this->assertEqual($user->id(), 2, 'Switched to user 2.');
+    $this->assertFalse($session_manager->isEnabled(), 'Session saving is disabled.');
+
+    // Perform a second (nested) user account switch.
+    $switcher->switchTo(new UserSession(array('uid' => 3)));
+    $this->assertEqual($user->id(), 3, 'Switched to user 3.');
+
+    // Revert to the user session that was active between the first and second
+    // switch.
+    $switcher->switchBack();
+
+    // Since we are still in the account from the first switch, session handling
+    // still needs to be disabled.
+    $this->assertEqual($user->id(), 2, 'Reverted back to user 2.');
+    $this->assertFalse($session_manager->isEnabled(), 'Session saving still disabled.');
+
+    // Revert to the original account which was active before the first switch.
+    $switcher->switchBack();
+
+    // Assert that the original account is active again, and that session saving
+    // has been re-enabled.
+    $this->assertEqual($user->id(), $original_user->id(), 'Original user correctly restored.');
+    $this->assertEqual($session_manager->isEnabled(), $original_session_saving, 'Original session saving correctly restored.');
+
+    // Verify that AccountSwitcherInterface::switchBack() will throw
+    // an exception if there are no accounts left in the stack.
+    try {
+      $switcher->switchBack();
+      $this->fail('::switchBack() throws exception if called without previous switch.');
+    }
+    catch (\RuntimeException $e) {
+      if ($e->getMessage() == 'No more accounts to revert to.') {
+        $this->pass('::switchBack() throws exception if called without previous switch.');
+      }
+      else {
+        $this->fail($e->getMessage());
+      }
+    }
+  }
+
+}