Add lock in MockFileSession to provide atomic writes

jderusse · jderusse · commit 97bab3989f15 · 2021-01-12T22:10:18.000+01:00
diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php b/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php
@@ -11,6 +11,9 @@
 
 namespace Symfony\Component\HttpFoundation\Session\Storage;
 
+use Symfony\Component\Lock\Exception\LockConflictedException;
+use Symfony\Component\Lock\Exception\LockStorageException;
+
 /**
  * MockFileSessionStorage is used to mock sessions for
  * functional testing when done in a single PHP process.
@@ -25,6 +28,7 @@
 class MockFileSessionStorage extends MockArraySessionStorage
 {
     private $savePath;
+    private $handle;
 
     /**
      * @param string $savePath Path of directory to save session files
@@ -103,7 +107,11 @@ public function save()
 
         try {
             if ($data) {
-                file_put_contents($this->getFilePath(), serialize($data));
+                rewind($this->handle);
+                fwrite($this->handle, serialize($data));
+                flock($this->handle, \LOCK_UN | \LOCK_NB);
+                fclose($this->handle);
+                $this->handle = null;
             } else {
                 $this->destroy();
             }
@@ -123,9 +131,12 @@ public function save()
      */
     private function destroy(): void
     {
-        if (is_file($this->getFilePath())) {
-            unlink($this->getFilePath());
-        }
+        $this->lock();
+        ftruncate($this->handle, 0);
+
+        flock($this->handle, \LOCK_UN | \LOCK_NB);
+        fclose($this->handle);
+        $this->handle = null;
     }
 
     /**
@@ -141,9 +152,38 @@ private function getFilePath(): string
      */
     private function read(): void
     {
-        $filePath = $this->getFilePath();
-        $this->data = is_readable($filePath) && is_file($filePath) ? unserialize(file_get_contents($filePath)) : [];
+        $this->lock();
+        rewind($this->handle);
+        $this->data = unserialize(stream_get_contents($this->handle)) ?: [];
 
         $this->loadSession();
     }
+
+    private function lock(): void
+    {
+        if (null !== $this->handle) {
+            return;
+        }
+
+        $filePath = $this->getFilePath();
+        // Silence error reporting
+        set_error_handler(function ($type, $msg) use (&$error) { $error = $msg; });
+        if (!$this->handle = fopen($filePath, 'r+')) {
+            if ($this->handle = fopen($filePath, 'x+')) {
+                chmod($filePath, 0666);
+            } elseif (!$this->handle = fopen($filePath, 'r+')) {
+                usleep(100); // Give some time for chmod() to complete
+                $this->handle = fopen($filePath, 'r+');
+            }
+        }
+        restore_error_handler();
+        if (!$this->handle) {
+            throw new \RuntimeException('Unable to read session file');
+        }
+        if (!flock($this->handle, \LOCK_EX|\LOCK_NB)) {
+            fclose($this->handle);
+            $this->handle = null;
+            throw new \RuntimeException('Unable to read session file');
+        }
+    }
 }
