Don't encrypt or decrypt unknown files in backup archives (#144495)

homeassistant/components/backup/http.py

@@ -22,7 +22,7 @@ from . import util
 from .agent import BackupAgent
 from .const import DATA_MANAGER
 from .manager import BackupManager
-from .models import BackupNotFound
+from .models import AgentBackup, BackupNotFound
 
 
 @callback
@@ -85,7 +85,15 @@ class DownloadBackupView(HomeAssistantView):
                     request, headers, backup_id, agent_id, agent, manager
                 )
             return await self._send_backup_with_password(
-                hass, request, headers, backup_id, agent_id, password, agent, manager
+                hass,
+                backup,
+                request,
+                headers,
+                backup_id,
+                agent_id,
+                password,
+                agent,
+                manager,
             )
         except BackupNotFound:
             return Response(status=HTTPStatus.NOT_FOUND)
@@ -116,6 +124,7 @@ class DownloadBackupView(HomeAssistantView):
     async def _send_backup_with_password(
         self,
         hass: HomeAssistant,
+        backup: AgentBackup,
         request: Request,
         headers: dict[istr, str],
         backup_id: str,
@@ -144,7 +153,8 @@ class DownloadBackupView(HomeAssistantView):
 
         stream = util.AsyncIteratorWriter(hass)
         worker = threading.Thread(
-            target=util.decrypt_backup, args=[reader, stream, password, on_done, 0, []]
+            target=util.decrypt_backup,
+            args=[backup, reader, stream, password, on_done, 0, []],
         )
         try:
             worker.start()

homeassistant/components/backup/util.py

@@ -295,13 +295,26 @@ def validate_password_stream(
     raise BackupEmpty
 
 
+def _get_expected_archives(backup: AgentBackup) -> set[str]:
+    """Get the expected archives in the backup."""
+    expected_archives = set()
+    if backup.homeassistant_included:
+        expected_archives.add("homeassistant")
+    for addon in backup.addons:
+        expected_archives.add(addon.slug)
+    for folder in backup.folders:
+        expected_archives.add(folder.value)
+    return expected_archives
+
+
 def decrypt_backup(
+    backup: AgentBackup,
     input_stream: IO[bytes],
     output_stream: IO[bytes],
     password: str | None,
     on_done: Callable[[Exception | None], None],
     minimum_size: int,
-    nonces: list[bytes],
+    nonces: NonceGenerator,
 ) -> None:
     """Decrypt a backup."""
     error: Exception | None = None
@@ -315,7 +328,7 @@ def decrypt_backup(
                     fileobj=output_stream, mode="w|", bufsize=BUF_SIZE
                 ) as output_tar,
             ):
-                _decrypt_backup(input_tar, output_tar, password)
+                _decrypt_backup(backup, input_tar, output_tar, password)
         except (DecryptError, SecureTarError, tarfile.TarError) as err:
             LOGGER.warning("Error decrypting backup: %s", err)
             error = err
@@ -333,15 +346,18 @@ def decrypt_backup(
 
 
 def _decrypt_backup(
+    backup: AgentBackup,
     input_tar: tarfile.TarFile,
     output_tar: tarfile.TarFile,
     password: str | None,
 ) -> None:
     """Decrypt a backup."""
+    expected_archives = _get_expected_archives(backup)
     for obj in input_tar:
         # We compare with PurePath to avoid issues with different path separators,
         # for example when backup.json is added as "./backup.json"
-        if PurePath(obj.name) == PurePath("backup.json"):
+        object_path = PurePath(obj.name)
+        if object_path == PurePath("backup.json"):
             # Rewrite the backup.json file to indicate that the backup is decrypted
             if not (reader := input_tar.extractfile(obj)):
                 raise DecryptError
@@ -352,7 +368,13 @@ def _decrypt_backup(
             metadata_obj.size = len(updated_metadata_b)
             output_tar.addfile(metadata_obj, BytesIO(updated_metadata_b))
             continue
-        if not obj.name.endswith((".tar", ".tgz", ".tar.gz")):
+        prefix, _, suffix = object_path.name.partition(".")
+        if suffix not in ("tar", "tgz", "tar.gz"):
+            LOGGER.debug("Unknown file %s will not be decrypted", obj.name)
+            output_tar.addfile(obj, input_tar.extractfile(obj))
+            continue
+        if prefix not in expected_archives:
+            LOGGER.debug("Unknown inner tar file %s will not be decrypted", obj.name)
             output_tar.addfile(obj, input_tar.extractfile(obj))
             continue
         istf = SecureTarFile(
@@ -371,12 +393,13 @@ def _decrypt_backup(
 
 
 def encrypt_backup(
+    backup: AgentBackup,
     input_stream: IO[bytes],
     output_stream: IO[bytes],
     password: str | None,
     on_done: Callable[[Exception | None], None],
     minimum_size: int,
-    nonces: list[bytes],
+    nonces: NonceGenerator,
 ) -> None:
     """Encrypt a backup."""
     error: Exception | None = None
@@ -390,7 +413,7 @@ def encrypt_backup(
                     fileobj=output_stream, mode="w|", bufsize=BUF_SIZE
                 ) as output_tar,
             ):
-                _encrypt_backup(input_tar, output_tar, password, nonces)
+                _encrypt_backup(backup, input_tar, output_tar, password, nonces)
         except (EncryptError, SecureTarError, tarfile.TarError) as err:
             LOGGER.warning("Error encrypting backup: %s", err)
             error = err
@@ -408,17 +431,20 @@ def encrypt_backup(
 
 
 def _encrypt_backup(
+    backup: AgentBackup,
     input_tar: tarfile.TarFile,
     output_tar: tarfile.TarFile,
     password: str | None,
-    nonces: list[bytes],
+    nonces: NonceGenerator,
 ) -> None:
     """Encrypt a backup."""
     inner_tar_idx = 0
+    expected_archives = _get_expected_archives(backup)
     for obj in input_tar:
         # We compare with PurePath to avoid issues with different path separators,
         # for example when backup.json is added as "./backup.json"
-        if PurePath(obj.name) == PurePath("backup.json"):
+        object_path = PurePath(obj.name)
+        if object_path == PurePath("backup.json"):
             # Rewrite the backup.json file to indicate that the backup is encrypted
             if not (reader := input_tar.extractfile(obj)):
                 raise EncryptError
@@ -429,16 +455,21 @@ def _encrypt_backup(
             metadata_obj.size = len(updated_metadata_b)
             output_tar.addfile(metadata_obj, BytesIO(updated_metadata_b))
             continue
-        if not obj.name.endswith((".tar", ".tgz", ".tar.gz")):
+        prefix, _, suffix = object_path.name.partition(".")
+        if suffix not in ("tar", "tgz", "tar.gz"):
+            LOGGER.debug("Unknown file %s will not be encrypted", obj.name)
             output_tar.addfile(obj, input_tar.extractfile(obj))
             continue
+        if prefix not in expected_archives:
+            LOGGER.debug("Unknown inner tar file %s will not be encrypted", obj.name)
+            continue
         istf = SecureTarFile(
             None,  # Not used
             gzip=False,
             key=password_to_key(password) if password is not None else None,
             mode="r",
             fileobj=input_tar.extractfile(obj),
-            nonce=nonces[inner_tar_idx],
+            nonce=nonces.get(inner_tar_idx),
         )
         inner_tar_idx += 1
         with istf.encrypt(obj) as encrypted:
@@ -456,17 +487,33 @@ class _CipherWorkerStatus:
     writer: AsyncIteratorWriter
 
 
+class NonceGenerator:
+    """Generate nonces for encryption."""
+
+    def __init__(self) -> None:
+        """Initialize the generator."""
+        self._nonces: dict[int, bytes] = {}
+
+    def get(self, index: int) -> bytes:
+        """Get a nonce for the given index."""
+        if index not in self._nonces:
+            # Generate a new nonce for the given index
+            self._nonces[index] = os.urandom(16)
+        return self._nonces[index]
+
+
 class _CipherBackupStreamer:
     """Encrypt or decrypt a backup."""
 
     _cipher_func: Callable[
         [
+            AgentBackup,
             IO[bytes],
             IO[bytes],
             str | None,
             Callable[[Exception | None], None],
             int,
-            list[bytes],
+            NonceGenerator,
         ],
         None,
     ]
@@ -484,7 +531,7 @@ class _CipherBackupStreamer:
         self._hass = hass
         self._open_stream = open_stream
         self._password = password
-        self._nonces: list[bytes] = []
+        self._nonces = NonceGenerator()
 
     def size(self) -> int:
         """Return the maximum size of the decrypted or encrypted backup."""
@@ -508,7 +555,15 @@ class _CipherBackupStreamer:
         writer = AsyncIteratorWriter(self._hass)
         worker = threading.Thread(
             target=self._cipher_func,
-            args=[reader, writer, self._password, on_done, self.size(), self._nonces],
+            args=[
+                self._backup,
+                reader,
+                writer,
+                self._password,
+                on_done,
+                self.size(),
+                self._nonces,
+            ],
         )
         worker_status = _CipherWorkerStatus(
             done=asyncio.Event(), reader=reader, thread=worker, writer=writer
@@ -538,17 +593,6 @@ class DecryptedBackupStreamer(_CipherBackupStreamer):
 class EncryptedBackupStreamer(_CipherBackupStreamer):
     """Encrypt a backup."""
 
-    def __init__(
-        self,
-        hass: HomeAssistant,
-        backup: AgentBackup,
-        open_stream: Callable[[], Coroutine[Any, Any, AsyncIterator[bytes]]],
-        password: str | None,
-    ) -> None:
-        """Initialize."""
-        super().__init__(hass, backup, open_stream, password)
-        self._nonces = [os.urandom(16) for _ in range(self._num_tar_files())]
-
     _cipher_func = staticmethod(encrypt_backup)
 
     def backup(self) -> AgentBackup:

tests/components/backup/test_http.py

@@ -177,7 +177,7 @@ async def _test_downloading_encrypted_backup(
         enc_metadata = json.loads(outer_tar.extractfile("./backup.json").read())
         assert enc_metadata["protected"] is True
         with (
-            outer_tar.extractfile("core.tar.gz") as inner_tar_file,
+            outer_tar.extractfile("homeassistant.tar.gz") as inner_tar_file,
             pytest.raises(tarfile.ReadError, match="file could not be opened"),
         ):
             # pylint: disable-next=consider-using-with
@@ -209,7 +209,7 @@ async def _test_downloading_encrypted_backup(
         dec_metadata = json.loads(outer_tar.extractfile("./backup.json").read())
         assert dec_metadata == enc_metadata | {"protected": False}
         with (
-            outer_tar.extractfile("core.tar.gz") as inner_tar_file,
+            outer_tar.extractfile("homeassistant.tar.gz") as inner_tar_file,
             tarfile.open(fileobj=inner_tar_file, mode="r") as inner_tar,
         ):
             assert inner_tar.getnames() == [

tests/components/backup/test_util.py

@@ -174,7 +174,10 @@ async def test_decrypted_backup_streamer(hass: HomeAssistant) -> None:
     )
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -218,7 +221,10 @@ async def test_decrypted_backup_streamer_interrupt_stuck_reader(
     """Test the decrypted backup streamer."""
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -253,7 +259,10 @@ async def test_decrypted_backup_streamer_interrupt_stuck_writer(
     """Test the decrypted backup streamer."""
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -283,7 +292,10 @@ async def test_decrypted_backup_streamer_wrong_password(hass: HomeAssistant) ->
     """Test the decrypted backup streamer with wrong password."""
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -320,7 +332,10 @@ async def test_encrypted_backup_streamer(hass: HomeAssistant) -> None:
     )
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -353,15 +368,16 @@ async def test_encrypted_backup_streamer(hass: HomeAssistant) -> None:
             bytes.fromhex("00000000000000000000000000000000"),
         )
         encryptor = EncryptedBackupStreamer(hass, backup, open_backup, "hunter2")
-    assert encryptor.backup() == dataclasses.replace(
-        backup, protected=True, size=backup.size + len(expected_padding)
-    )
 
-    encrypted_stream = await encryptor.open_stream()
-    encrypted_output = b""
-    async for chunk in encrypted_stream:
-        encrypted_output += chunk
-    await encryptor.wait()
+        assert encryptor.backup() == dataclasses.replace(
+            backup, protected=True, size=backup.size + len(expected_padding)
+        )
+
+        encrypted_stream = await encryptor.open_stream()
+        encrypted_output = b""
+        async for chunk in encrypted_stream:
+            encrypted_output += chunk
+        await encryptor.wait()
 
     # Expect the output to match the stored encrypted backup file, with additional
     # padding.
@@ -377,7 +393,10 @@ async def test_encrypted_backup_streamer_interrupt_stuck_reader(
         "test_backups/c0cb53bd.tar.decrypted", DOMAIN
     )
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -414,7 +433,10 @@ async def test_encrypted_backup_streamer_interrupt_stuck_writer(
         "test_backups/c0cb53bd.tar.decrypted", DOMAIN
     )
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -447,7 +469,10 @@ async def test_encrypted_backup_streamer_random_nonce(hass: HomeAssistant) -> No
     )
     encrypted_backup_path = get_fixture_path("test_backups/c0cb53bd.tar", DOMAIN)
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,
@@ -490,7 +515,7 @@ async def test_encrypted_backup_streamer_random_nonce(hass: HomeAssistant) -> No
     await encryptor1.wait()
     await encryptor2.wait()
 
-    # Output from the two streames should differ but have the same length.
+    # Output from the two streams should differ but have the same length.
     assert encrypted_output1 != encrypted_output3
     assert len(encrypted_output1) == len(encrypted_output3)
 
@@ -508,7 +533,10 @@ async def test_encrypted_backup_streamer_error(hass: HomeAssistant) -> None:
         "test_backups/c0cb53bd.tar.decrypted", DOMAIN
     )
     backup = AgentBackup(
-        addons=["addon_1", "addon_2"],
+        addons=[
+            AddonInfo(name="Core 1", slug="core1", version="1.0.0"),
+            AddonInfo(name="Core 2", slug="core2", version="1.0.0"),
+        ],
         backup_id="1234",
         date="2024-12-02T07:23:58.261875-05:00",
         database_included=False,