Merge branch '4.4' into 5.0

* 4.4:
  [Security] Allow switching to another user when already switched

Author: chalasr

Firewall/SwitchUserListener.php

@@ -144,7 +144,8 @@ private function attemptSwitchUser(Request $request, string $username): ?TokenIn
                 return $token;
             }
 
-            throw new \LogicException(sprintf('You are already switched to "%s" user.', $token->getUsername()));
+            // User already switched, exit before seamlessly switching to another user
+            $token = $this->attemptExitUser($request);
         }
 
         $currentUsername = $token->getUsername();

Tests/Firewall/SwitchUserListenerTest.php

@@ -223,6 +223,39 @@ public function testSwitchUser()
         $this->assertInstanceOf('Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken', $this->tokenStorage->getToken());
     }
 
+    public function testSwitchUserAlreadySwitched()
+    {
+        $originalToken = new UsernamePasswordToken('original', null, 'key', ['ROLE_FOO']);
+        $alreadySwitchedToken = new SwitchUserToken('switched_1', null, 'key', ['ROLE_BAR'], $originalToken);
+
+        $tokenStorage = new TokenStorage();
+        $tokenStorage->setToken($alreadySwitchedToken);
+
+        $targetUser = new User('kuba', 'password', ['ROLE_FOO', 'ROLE_BAR']);
+
+        $this->request->query->set('_switch_user', 'kuba');
+
+        $this->accessDecisionManager->expects($this->once())
+            ->method('decide')->with($originalToken, ['ROLE_ALLOWED_TO_SWITCH'], $targetUser)
+            ->willReturn(true);
+
+        $this->userProvider->expects($this->exactly(2))
+            ->method('loadUserByUsername')
+            ->withConsecutive(['kuba'])
+            ->will($this->onConsecutiveCalls($targetUser, $this->throwException(new UsernameNotFoundException())));
+        $this->userChecker->expects($this->once())
+            ->method('checkPostAuth')->with($targetUser);
+
+        $listener = new SwitchUserListener($tokenStorage, $this->userProvider, $this->userChecker, 'provider123', $this->accessDecisionManager, null, '_switch_user', 'ROLE_ALLOWED_TO_SWITCH', null, false);
+        $listener($this->event);
+
+        $this->assertSame([], $this->request->query->all());
+        $this->assertSame('', $this->request->server->get('QUERY_STRING'));
+        $this->assertInstanceOf(SwitchUserToken::class, $tokenStorage->getToken());
+        $this->assertSame('kuba', $tokenStorage->getToken()->getUsername());
+        $this->assertSame($originalToken, $tokenStorage->getToken()->getOriginalToken());
+    }
+
     public function testSwitchUserWorksWithFalsyUsernames()
     {
         $token = new UsernamePasswordToken('username', '', 'key', ['ROLE_FOO']);