ssh/terminal: use duplicate handle in ReadPassword

os.NewFile assigns finalizer to close file handle
passed into ReadPassword. But that is not expected.
Make a duplicate of original file handle, and pass
copy handle into ReadPassword instead.

Fixes golang/go#23525

Change-Id: I4d6725e9a1cc20defd1b58afc383e35a7f9ee4e9
Reviewed-on: https://go-review.googlesource.com/89395
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ssh/terminal/util_windows.go

@@ -93,5 +93,13 @@ func ReadPassword(fd int) ([]byte, error) {
 		windows.SetConsoleMode(windows.Handle(fd), old)
 	}()
 
-	return readPasswordLine(os.NewFile(uintptr(fd), "stdin"))
+	var h windows.Handle
+	p, _ := windows.GetCurrentProcess()
+	if err := windows.DuplicateHandle(p, windows.Handle(fd), p, &h, 0, false, windows.DUPLICATE_SAME_ACCESS); err != nil {
+		return nil, err
+	}
+
+	f := os.NewFile(uintptr(h), "stdin")
+	defer f.Close()
+	return readPasswordLine(f)
 }