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

FileBinaryMimeTypeGuesser.php

@@ -31,7 +31,7 @@ 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;
     }
@@ -74,7 +74,7 @@ public function guessMimeType(string $path): ?string
         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/AbstractMimeTypeGuesserTest.php

@@ -27,6 +27,21 @@ public static function tearDownAfterClass(): void
 
     abstract protected function getGuesser(): MimeTypeGuesserInterface;
 
+    public function testGuessWithLeadingDash()
+    {
+        if (!$this->getGuesser()->isGuesserSupported()) {
+            $this->markTestSkipped('Guesser is not supported');
+        }
+
+        $cwd = getcwd();
+        chdir(__DIR__.'/Fixtures/mimetypes');
+        try {
+            $this->assertEquals('image/gif', $this->getGuesser()->guessMimeType('-test'));
+        } finally {
+            chdir($cwd);
+        }
+    }
+
     public function testGuessImageWithoutExtension()
     {
         if (!$this->getGuesser()->isGuesserSupported()) {