Island: Implement DataStoreEncryptor as a class

This allows us to begin decoupling some implementation details from the
AuthenticationService.

monkey/monkey_island/cc/server_utils/encryption/data_store_encryptor.py

@@ -1,4 +1,5 @@
 import os
+from pathlib import Path
 from typing import Union
 
 from Crypto import Random  # noqa: DUO133  # nosec: B413
@@ -9,49 +10,62 @@ from .i_encryptor import IEncryptor
 from .key_based_encryptor import KeyBasedEncryptor
 from .password_based_bytes_encryptor import PasswordBasedBytesEncryptor
 
-_KEY_FILENAME = "mongo_key.bin"
-_BLOCK_SIZE = 32
-
 _encryptor: Union[None, IEncryptor] = None
 
 
-def _load_existing_key(key_file_path: str, secret: str) -> KeyBasedEncryptor:
-    with open(key_file_path, "rb") as f:
-        encrypted_key = f.read()
-    cipher_key = PasswordBasedBytesEncryptor(secret).decrypt(encrypted_key)
-    return KeyBasedEncryptor(cipher_key)
+class DataStoreEncryptor(IEncryptor):
+    _KEY_LENGTH_BYTES = 32
+
+    def __init__(self, secret: str, key_file_path: Path):
+        self._key_file_path = key_file_path
+        self._password_based_encryptor = PasswordBasedBytesEncryptor(secret)
+        self._key_based_encryptor = self._initialize_key_based_encryptor()
+
+    def _initialize_key_based_encryptor(self):
+        if os.path.exists(self._key_file_path):
+            return self._load_existing_key()
+
+        return self._create_new_key()
+
+    def _load_existing_key(self) -> KeyBasedEncryptor:
+        with open(self._key_file_path, "rb") as f:
+            encrypted_key = f.read()
+
+        plaintext_key = self._password_based_encryptor.decrypt(encrypted_key)
+        return KeyBasedEncryptor(plaintext_key)
+
+    def _create_new_key(self) -> KeyBasedEncryptor:
+        plaintext_key = Random.new().read(DataStoreEncryptor._KEY_LENGTH_BYTES)
+
+        encrypted_key = self._password_based_encryptor.encrypt(plaintext_key)
+        with open_new_securely_permissioned_file(self._key_file_path, "wb") as f:
+            f.write(encrypted_key)
+
+        return KeyBasedEncryptor(plaintext_key)
+
+    def encrypt(self, plaintext: str) -> str:
+        return self._key_based_encryptor.encrypt(plaintext)
+
+    def decrypt(self, ciphertext: str):
+        return self._key_based_encryptor.decrypt(ciphertext)
+
+    def erase_key(self):
+        if self._key_file_path.is_file():
+            self._key_file_path.unlink()
 
 
-def _create_new_key(key_file_path: str, secret: str) -> KeyBasedEncryptor:
-    cipher_key = _get_random_bytes()
-    encrypted_key = PasswordBasedBytesEncryptor(secret).encrypt(cipher_key)
-    with open_new_securely_permissioned_file(key_file_path, "wb") as f:
-        f.write(encrypted_key)
-    return KeyBasedEncryptor(cipher_key)
+def remove_old_datastore_key():
+    if _encryptor:
+        _encryptor.erase_key()
 
 
-def _get_random_bytes() -> bytes:
-    return Random.new().read(_BLOCK_SIZE)
-
-
-def remove_old_datastore_key(key_file_dir: str):
-    key_file_path = _get_key_file_path(key_file_dir)
-    if os.path.isfile(key_file_path):
-        os.remove(key_file_path)
-
-
-def initialize_datastore_encryptor(key_file_dir: str, secret: str):
+def initialize_datastore_encryptor(
+    key_file_dir: str, secret: str, key_file_name: str = "mongo_key.bin"
+):
     global _encryptor
 
-    key_file_path = _get_key_file_path(key_file_dir)
-    if os.path.exists(key_file_path):
-        _encryptor = _load_existing_key(key_file_path, secret)
-    else:
-        _encryptor = _create_new_key(key_file_path, secret)
-
-
-def _get_key_file_path(key_file_dir: str) -> str:
-    return os.path.join(key_file_dir, _KEY_FILENAME)
+    key_file_path = Path(key_file_dir) / key_file_name
+    _encryptor = DataStoreEncryptor(secret, key_file_path)
 
 
 def get_datastore_encryptor() -> IEncryptor:

monkey/monkey_island/cc/services/authentication.py

@@ -22,7 +22,7 @@ class AuthenticationService:
 
     @staticmethod
     def reset_datastore_encryptor(username: str, password: str):
-        remove_old_datastore_key(AuthenticationService.KEY_FILE_DIRECTORY)
+        remove_old_datastore_key()
         AuthenticationService._init_encryptor_from_credentials(username, password)
 
     @staticmethod

monkey/tests/unit_tests/monkey_island/cc/server_utils/encryption/test_data_store_encryptor.py

@@ -10,10 +10,24 @@ from monkey_island.cc.server_utils.encryption import (
 PLAINTEXT = "Hello, Monkey!"
 MOCK_SECRET = "53CR31"
 
+KEY_FILENAME = "test_key.bin"
+
+
+@pytest.fixture(autouse=True)
+def cleanup_encryptor():
+    yield
+    data_store_encryptor._encryptor = None
+
+
+@pytest.fixture
+def key_file(tmp_path):
+    return tmp_path / KEY_FILENAME
+
 
 @pytest.mark.slow
-@pytest.mark.usefixtures("uses_encryptor")
-def test_encryption(data_for_tests_dir):
+def test_encryption(tmp_path):
+    initialize_datastore_encryptor(tmp_path, MOCK_SECRET, KEY_FILENAME)
+
     encrypted_data = get_datastore_encryptor().encrypt(PLAINTEXT)
     assert encrypted_data != PLAINTEXT
 
@@ -21,45 +35,35 @@ def test_encryption(data_for_tests_dir):
     assert decrypted_data == PLAINTEXT
 
 
-@pytest.fixture
-def cleanup_encryptor():
-    yield
-    data_store_encryptor._encryptor = None
-
-
-@pytest.mark.usefixtures("cleanup_encryptor")
-@pytest.fixture
-def initialized_encryptor_dir(tmpdir):
-    initialize_datastore_encryptor(tmpdir, MOCK_SECRET)
-    return tmpdir
+@pytest.mark.slow
+def test_key_creation(key_file, tmp_path):
+    assert not key_file.is_file()
+    initialize_datastore_encryptor(tmp_path, MOCK_SECRET, KEY_FILENAME)
+    assert key_file.is_file()
 
 
 @pytest.mark.slow
-def test_key_creation(initialized_encryptor_dir):
-    assert (initialized_encryptor_dir / data_store_encryptor._KEY_FILENAME).isfile()
+def test_key_removal(key_file, tmp_path):
+    initialize_datastore_encryptor(tmp_path, MOCK_SECRET, KEY_FILENAME)
+    assert key_file.is_file()
+
+    remove_old_datastore_key()
+    assert not key_file.is_file()
 
 
-@pytest.mark.slow
-def test_key_removal(initialized_encryptor_dir):
-    remove_old_datastore_key(initialized_encryptor_dir)
-    assert not (initialized_encryptor_dir / data_store_encryptor._KEY_FILENAME).isfile()
-
-
-def test_key_removal__no_key(tmpdir):
-    assert not (tmpdir / data_store_encryptor._KEY_FILENAME).isfile()
+def test_key_removal__no_key(key_file):
+    assert not key_file.is_file()
     # Make sure no error thrown when we try to remove an non-existing key
-    remove_old_datastore_key(tmpdir)
-    data_store_encryptor._factory = None
+    remove_old_datastore_key()
 
 
-@pytest.mark.slow
-@pytest.mark.usefixtures("cleanup_encryptor")
-def test_key_file_encryption(tmpdir, monkeypatch):
-    monkeypatch.setattr(data_store_encryptor, "_get_random_bytes", lambda: PLAINTEXT.encode())
-    initialize_datastore_encryptor(tmpdir, MOCK_SECRET)
-    key_file_path = data_store_encryptor._get_key_file_path(tmpdir)
-    key_file_contents = open(key_file_path, "rb").read()
-    assert not key_file_contents == PLAINTEXT.encode()
+def test_key_removal__no_key_2(key_file, tmp_path):
+    assert not key_file.is_file()
+    initialize_datastore_encryptor(tmp_path, MOCK_SECRET, KEY_FILENAME)
+    assert key_file.is_file()
 
-    key_based_encryptor = data_store_encryptor._load_existing_key(key_file_path, MOCK_SECRET)
-    assert key_based_encryptor._key == PLAINTEXT.encode()
+    key_file.unlink()
+    assert not key_file.is_file()
+
+    # Make sure no error thrown when we try to remove an non-existing key
+    get_datastore_encryptor().erase_key()