From 053fa43add5c8a7cf364958eab426a39a564a2be Mon Sep 17 00:00:00 2001
From: Chris Wilkinson <c.wilkinson@elifesciences.org>
Date: Wed, 3 Jan 2018 14:12:06 +0000
Subject: [PATCH] [Security] Fail gracefully if the security token cannot be
 unserialized from the session

---
 .../Http/Firewall/ContextListener.php         | 43 ++++++++++++++++++-
 .../Tests/Firewall/ContextListenerTest.php    |  2 +
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/Symfony/Component/Security/Http/Firewall/ContextListener.php b/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
index b446f57e4985..7a3483b2ecc8 100644
--- a/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
+++ b/src/Symfony/Component/Security/Http/Firewall/ContextListener.php
@@ -39,6 +39,8 @@ class ContextListener implements ListenerInterface
     private $dispatcher;
     private $registered;
 
+    private static $unserializeExceptionCode = 0x37313bc;
+
     public function __construct(TokenStorageInterface $tokenStorage, array $userProviders, $contextKey, LoggerInterface $logger = null, EventDispatcherInterface $dispatcher = null)
     {
         if (empty($contextKey)) {
@@ -77,7 +79,7 @@ public function handle(GetResponseEvent $event)
             return;
         }
 
-        $token = unserialize($token);
+        $token = $this->safelyUnserialize($token);
 
         if (null !== $this->logger) {
             $this->logger->debug('Read existing security token from the session.', array('key' => $this->sessionKey));
@@ -171,4 +173,43 @@ protected function refreshUser(TokenInterface $token)
 
         throw new \RuntimeException(sprintf('There is no user provider for user "%s".', get_class($user)));
     }
+
+    private function safelyUnserialize($serializedToken)
+    {
+        $e = $token = null;
+        $prevUnserializeHandler = ini_set('unserialize_callback_func', __CLASS__.'::handleUnserializeCallback');
+        $prevErrorHandler = set_error_handler(function ($type, $msg, $file, $line, $context = array()) use (&$prevErrorHandler) {
+            if (__FILE__ === $file) {
+                throw new \UnexpectedValueException($msg, self::$unserializeExceptionCode);
+            }
+
+            return $prevErrorHandler ? $prevErrorHandler($type, $msg, $file, $line, $context) : false;
+        });
+
+        try {
+            $token = unserialize($serializedToken);
+        } catch (\Error $e) {
+        } catch (\Exception $e) {
+        }
+        restore_error_handler();
+        ini_set('unserialize_callback_func', $prevUnserializeHandler);
+        if ($e) {
+            if (!$e instanceof \UnexpectedValueException || self::$unserializeExceptionCode !== $e->getCode()) {
+                throw $e;
+            }
+            if ($this->logger) {
+                $this->logger->warning('Failed to unserialize the security token from the session.', array('key' => $this->sessionKey, 'received' => $serializedToken, 'exception' => $e));
+            }
+        }
+
+        return $token;
+    }
+
+    /**
+     * @internal
+     */
+    public static function handleUnserializeCallback($class)
+    {
+        throw new \UnexpectedValueException('Class not found: '.$class, self::$unserializeExceptionCode);
+    }
 }
diff --git a/src/Symfony/Component/Security/Http/Tests/Firewall/ContextListenerTest.php b/src/Symfony/Component/Security/Http/Tests/Firewall/ContextListenerTest.php
index e3bb11caa9c8..2ecaa53c6929 100644
--- a/src/Symfony/Component/Security/Http/Tests/Firewall/ContextListenerTest.php
+++ b/src/Symfony/Component/Security/Http/Tests/Firewall/ContextListenerTest.php
@@ -169,6 +169,8 @@ public function testInvalidTokenInSession($token)
     public function provideInvalidToken()
     {
         return array(
+            array('foo'),
+            array('O:8:"NotFound":0:{}'),
             array(serialize(new \__PHP_Incomplete_Class())),
             array(serialize(null)),
             array(null),