Merge branch '4.3' into 4.4

* 4.3:
  [Console] Constant STDOUT might be undefined.
  Allow returning null from NormalizerInterface::normalize
  [Security\Core] throw AccessDeniedException when switch user fails
  [Mime] fix guessing mime-types of files with leading dash
  [HttpFoundation] fix guessing mime-types of files with leading dash
  [VarExporter] fix exporting some strings
  [Cache] forbid serializing AbstractAdapter and TagAwareAdapter instances
  Use constant time comparison in UriSigner

Author: nicolas-grekas

File/MimeType/FileBinaryMimeTypeGuesser.php

@@ -36,7 +36,7 @@ class FileBinaryMimeTypeGuesser implements MimeTypeGuesserInterface
      *
      * @param string $cmd The command to run to get the mime type of a file
      */
-    public function __construct(string $cmd = 'file -b --mime %s 2>/dev/null')
+    public function __construct(string $cmd = 'file -b --mime -- %s 2>/dev/null')
     {
         $this->cmd = $cmd;
     }
@@ -85,7 +85,7 @@ public function guess($path)
         ob_start();
 
         // need to use --mime instead of -i. see #6641
-        passthru(sprintf($this->cmd, escapeshellarg($path)), $return);
+        passthru(sprintf($this->cmd, escapeshellarg((0 === strpos($path, '-') ? './' : '').$path)), $return);
         if ($return > 0) {
             ob_end_clean();
 

Tests/File/Fixtures/-test

@@ -21,6 +21,17 @@
  */
 class MimeTypeTest extends TestCase
 {
+    public function testGuessWithLeadingDash()
+    {
+        $cwd = getcwd();
+        chdir(__DIR__.'/../Fixtures');
+        try {
+            $this->assertEquals('image/gif', MimeTypeGuesser::getInstance()->guess('-test'));
+        } finally {
+            chdir($cwd);
+        }
+    }
+
     public function testGuessImageWithoutExtension()
     {
         $this->assertEquals('image/gif', MimeTypeGuesser::getInstance()->guess(__DIR__.'/../Fixtures/test'));