island: Return file descriptor when creating secure file

monkey/monkey_island/cc/server_utils/encryptor.py

@@ -6,7 +6,7 @@ import os
 from Crypto import Random  # noqa: DUO133  # nosec: B413
 from Crypto.Cipher import AES  # noqa: DUO133  # nosec: B413
 
-from monkey_island.cc.server_utils.file_utils import create_secure_file
+from monkey_island.cc.server_utils.file_utils import get_file_descriptor_for_new_secure_file
 
 __author__ = "itay.mizeretz"
 
@@ -23,12 +23,11 @@ class Encryptor:
         if os.path.exists(password_file):
             self._load_existing_key(password_file)
         else:
-            create_secure_file(path=password_file)
             self._init_key(password_file)
 
     def _init_key(self, password_file):
         self._cipher_key = Random.new().read(self._BLOCK_SIZE)
-        with open(password_file, "wb") as f:
+        with open(get_file_descriptor_for_new_secure_file(path=password_file)) as f:
             f.write(self._cipher_key)
 
     def _load_existing_key(self, password_file):

monkey/monkey_island/cc/server_utils/file_utils.py

@@ -2,7 +2,6 @@ import logging
 import os
 import platform
 import stat
-from pathlib import Path
 
 LOG = logging.getLogger(__name__)
 
@@ -55,25 +54,30 @@ def _create_secure_directory_windows(path: str):
         raise ex
 
 
-def create_secure_file(path: str):
+def get_file_descriptor_for_new_secure_file(path: str):
     if not os.path.isfile(path):
         if is_windows_os():
-            _create_secure_file_windows(path)
+            return _get_file_descriptor_for_new_secure_file_windows(path)
         else:
-            _create_secure_file_linux(path)
+            return _get_file_descriptor_for_new_secure_file_linux(path)
 
 
-def _create_secure_file_linux(path: str):
+def _get_file_descriptor_for_new_secure_file_linux(path: str):
     try:
         mode = stat.S_IRUSR | stat.S_IWUSR
-        Path(path).touch(mode=mode, exist_ok=False)
+        flags = (
+            os.O_RDWR | os.O_CREAT | os.O_EXCL
+        )  # read/write, create new, throw error if file exists
+        fd = os.open(path, flags, mode)
+
+        return fd
 
     except Exception as ex:
         LOG.error(f'Could not create a file at "{path}": {str(ex)}')
         raise ex
 
 
-def _create_secure_file_windows(path: str):
+def _get_file_descriptor_for_new_secure_file_windows(path: str):
     try:
         file_access = win32file.GENERIC_READ | win32file.GENERIC_WRITE
         file_sharing = (
@@ -86,8 +90,7 @@ def _create_secure_file_windows(path: str):
         file_creation = win32file.CREATE_NEW  # fails if file exists
         file_attributes = win32file.FILE_FLAG_BACKUP_SEMANTICS
 
-        win32file.CloseHandle(
+        fd = win32file.CreateFile(
-            win32file.CreateFile(
             path,
             file_access,
             file_sharing,
@@ -98,7 +101,8 @@ def _create_secure_file_windows(path: str):
                 None, ""
             ),  # https://stackoverflow.com/questions/46800142/in-python-with-pywin32-win32job-the-createjobobject-function-how-do-i-pass-nu  # noqa: E501
         )
-        )
+
+        return fd
 
     except Exception as ex:
         LOG.error(f'Could not create a file at "{path}": {str(ex)}')