Update iOS backup decryption for iphone_backup_decrypt 0.11.2

pyproject.toml

@@ -24,7 +24,7 @@ dependencies = [
     "simplejson==4.1.1",
     "packaging==26.3",
     "appdirs==1.4.4",
-    "iphone_backup_decrypt==0.10.0",
+    "iphone_backup_decrypt==0.11.2",
     "pycryptodome>=3.20.0",
     "cryptography==50.0.0",
     "PyYAML>=6.0.2",

src/mvt/ios/decrypt.py

@@ -8,10 +8,8 @@ import glob
 import logging
 import os
 import os.path
-import plistlib
 import shutil
 import sqlite3
-import tempfile
 from concurrent.futures import (
     ALL_COMPLETED,
     FIRST_COMPLETED,
@@ -22,100 +20,26 @@ from concurrent.futures import (
 from pathlib import Path
 from typing import Optional
 
-from iphone_backup_decrypt import EncryptedBackup
-from iphone_backup_decrypt import google_iphone_dataprotection
+from iphone_backup_decrypt import (
+    BackupNotEncryptedError,
+    EncryptedBackup,
+    IncorrectPassphraseError,
+    NotABackupFolderError,
+)
 from iphone_backup_decrypt.utils import FilePlist
 
 from .decrypt_config import DEFAULT_DECRYPT_WORKERS, MAX_DECRYPT_WORKERS
 
 log = logging.getLogger(__name__)
 
-# Import pbkdf2_hmac from the same source iphone_backup_decrypt uses internally,
-# so our key derivation is consistent with theirs.
-try:
-    from fastpbkdf2 import pbkdf2_hmac
-except ImportError:
-    import Crypto.Hash.SHA1
-    import Crypto.Hash.SHA256
-    import Crypto.Protocol.KDF
-
-    _HASH_FNS = {"sha1": Crypto.Hash.SHA1, "sha256": Crypto.Hash.SHA256}
-
-    def pbkdf2_hmac(hash_name, password, salt, iterations, dklen=None):
-        return Crypto.Protocol.KDF.PBKDF2(
-            password, salt, dklen, iterations, hmac_hash_module=_HASH_FNS[hash_name]
-        )
-
-
 class MVTEncryptedBackup(EncryptedBackup):
-    """Extends EncryptedBackup with derived key export/import.
-
-    NOTE: This subclass relies on internal APIs of iphone_backup_decrypt
-    (specifically _read_and_unlock_keybag, _keybag, and the Keybag class
-    internals). Pinned to iphone_backup_decrypt==0.10.0.
-    """
-
-    def __init__(self, *, backup_directory, passphrase=None, derived_key=None):
-        if passphrase:
-            super().__init__(backup_directory=backup_directory, passphrase=passphrase)
-            self._derived_key = None  # Will be set after keybag unlock
-        elif derived_key:
-            self._init_without_passphrase(backup_directory, derived_key)
-        else:
-            raise ValueError("Either passphrase or derived_key must be provided")
-
-    def _init_without_passphrase(self, backup_directory, derived_key):
-        """Replicate parent __init__ state without requiring a passphrase."""
-        self.decrypted = False
-        self._backup_directory = os.path.expandvars(backup_directory)
-        self._passphrase = None
-        self._manifest_plist_path = os.path.join(
-            self._backup_directory, "Manifest.plist"
-        )
-        self._manifest_plist = None
-        self._manifest_db_path = os.path.join(self._backup_directory, "Manifest.db")
-        self._keybag = None
-        self._unlocked = False
-        self._temporary_folder = tempfile.mkdtemp()
-        self._temp_decrypted_manifest_db_path = os.path.join(
-            self._temporary_folder, "Manifest.db"
-        )
-        self._temp_manifest_db_conn = None
-        self._derived_key = derived_key  # 32 raw bytes
-
-    def _read_and_unlock_keybag(self):
-        """Override to capture derived key on password unlock, or use
-        a pre-derived key to skip PBKDF2."""
-        if self._unlocked:
-            return self._unlocked
-
-        with open(self._manifest_plist_path, "rb") as infile:
-            self._manifest_plist = plistlib.load(infile)
-        self._keybag = google_iphone_dataprotection.Keybag(
-            self._manifest_plist["BackupKeyBag"]
-        )
-
-        if self._derived_key:
-            # Skip PBKDF2, unwrap class keys directly with pre-derived key
-            self._unlocked = _unlock_keybag_with_derived_key(
-                self._keybag, self._derived_key
-            )
-        else:
-            # Normal path: full PBKDF2 derivation, capturing the intermediate key
-            self._unlocked, self._derived_key = _unlock_keybag_and_capture_key(
-                self._keybag, self._passphrase
-            )
-            self._passphrase = None
-
-        if not self._unlocked:
-            raise ValueError("Failed to decrypt keys: incorrect passphrase?")
-        return True
+    """Extract backup files by ID while MVT processes them concurrently."""
 
     def get_decryption_key(self):
         """Return derived key as hex string (64 chars / 32 bytes)."""
-        if self._derived_key is None:
+        if self.keybag is None or self.keybag.passphrase_key is None:
             raise ValueError("No derived key available")
-        return self._derived_key.hex()
+        return self.keybag.passphrase_key.hex()
 
     def extract_file_by_id(self, *, file_id, file_bplist, output_filename):
         """Extract one manifest entry without loading the whole file into memory."""
@@ -129,8 +53,9 @@ class MVTEncryptedBackup(EncryptedBackup):
             shutil.copy2(source_filename, output_filename)
             return
 
-        inner_key = self._keybag.unwrapKeyForClass(
-            file_plist.protection_class, file_plist.encryption_key
+        inner_key = self.keybag.unwrap_key_for_class(
+            protection_class=file_plist.protection_class,
+            wrapped_file_key=file_plist.encryption_key,
         )
         self._decrypt_file_to_disk(
             file_id=file_id,
@@ -139,47 +64,6 @@ class MVTEncryptedBackup(EncryptedBackup):
             output_filepath=output_filename,
         )
 
-
-def _unlock_keybag_with_derived_key(keybag, passphrase_key):
-    """Unlock keybag class keys using a pre-derived passphrase_key,
-    skipping the expensive PBKDF2 rounds."""
-    WRAP_PASSPHRASE = 2
-    for classkey in keybag.classKeys.values():
-        if b"WPKY" not in classkey:
-            continue
-        if classkey[b"WRAP"] & WRAP_PASSPHRASE:
-            k = google_iphone_dataprotection._AESUnwrap(
-                passphrase_key, classkey[b"WPKY"]
-            )
-            if not k:
-                return False
-            classkey[b"KEY"] = k
-    return True
-
-
-def _unlock_keybag_and_capture_key(keybag, passphrase):
-    """Run full PBKDF2 key derivation and AES unwrap, returning
-    (success, passphrase_key) so the derived key can be exported."""
-    passphrase_round1 = pbkdf2_hmac(
-        "sha256", passphrase, keybag.attrs[b"DPSL"], keybag.attrs[b"DPIC"], 32
-    )
-    passphrase_key = pbkdf2_hmac(
-        "sha1", passphrase_round1, keybag.attrs[b"SALT"], keybag.attrs[b"ITER"], 32
-    )
-    WRAP_PASSPHRASE = 2
-    for classkey in keybag.classKeys.values():
-        if b"WPKY" not in classkey:
-            continue
-        if classkey[b"WRAP"] & WRAP_PASSPHRASE:
-            k = google_iphone_dataprotection._AESUnwrap(
-                passphrase_key, classkey[b"WPKY"]
-            )
-            if not k:
-                return False, None
-            classkey[b"KEY"] = k
-    return True, passphrase_key
-
-
 class DecryptBackup:
     """This class provides functions to decrypt an encrypted iTunes backup
     using either a password or a key file.
@@ -376,41 +260,36 @@ class DecryptBackup:
                 )
                 return
 
-        # Before proceeding, we check whether the backup is indeed encrypted.
-        if not self.is_encrypted(self.backup_path):
-            return
-
         try:
             self._backup = MVTEncryptedBackup(
                 backup_directory=self.backup_path,
                 passphrase=password,
             )
+            # Manifest.db is a more reliable indication of encryption than
+            # the IsEncrypted field in Manifest.plist.
+            if not self.is_encrypted(self.backup_path):
+                self._backup = None
+                return
             # Eagerly trigger keybag unlock so wrong-password errors
             # surface here rather than later during process_backup().
             self._backup.test_decryption()
+        except IncorrectPassphraseError:
+            self._backup = None
+            log.critical("Failed to decrypt backup. Password is probably wrong.")
+        except (NotABackupFolderError, FileNotFoundError):
+            self._backup = None
+            log.critical(
+                "Failed to find a valid backup at %s. "
+                "Did you point to the right backup path?",
+                self.backup_path,
+            )
+        except BackupNotEncryptedError:
+            self._backup = None
+            log.critical("The backup does not seem encrypted!")
         except Exception as exc:
             self._backup = None
-            if (
-                isinstance(exc, ValueError)
-                and "passphrase" in str(exc).lower()
-            ):
-                log.critical("Failed to decrypt backup. Password is probably wrong.")
-            elif (
-                isinstance(exc, FileNotFoundError)
-                and hasattr(exc, "filename")
-                and os.path.basename(exc.filename) == "Manifest.plist"
-            ):
-                log.critical(
-                    "Failed to find a valid backup at %s. "
-                    "Did you point to the right backup path?",
-                    self.backup_path,
-                )
-            else:
-                log.exception(exc)
-                log.critical(
-                    "Failed to decrypt backup. Did you provide the correct password? "
-                    "Did you point to the right backup path?"
-                )
+            log.exception(exc)
+            log.critical("Failed to decrypt backup.")
 
     def decrypt_with_key_file(self, key_file: str) -> None:
         """Decrypts an encrypted iOS backup using a key file.
@@ -424,10 +303,6 @@ class DecryptBackup:
             key_file,
         )
 
-        # Before proceeding, we check whether the backup is indeed encrypted.
-        if not self.is_encrypted(self.backup_path):
-            return
-
         with open(key_file, "rb") as handle:
             key_bytes = handle.read()
 
@@ -442,16 +317,30 @@ class DecryptBackup:
             key_bytes_raw = binascii.unhexlify(key_bytes)
             self._backup = MVTEncryptedBackup(
                 backup_directory=self.backup_path,
-                derived_key=key_bytes_raw,
+                passphrase_key=key_bytes_raw,
             )
+            if not self.is_encrypted(self.backup_path):
+                self._backup = None
+                return
             # Eagerly trigger keybag unlock so wrong-key errors surface here.
             self._backup.test_decryption()
+        except (binascii.Error, IncorrectPassphraseError):
+            self._backup = None
+            log.critical("Failed to decrypt backup. Key file is probably wrong.")
+        except (NotABackupFolderError, FileNotFoundError):
+            self._backup = None
+            log.critical(
+                "Failed to find a valid backup at %s. "
+                "Did you point to the right backup path?",
+                self.backup_path,
+            )
+        except BackupNotEncryptedError:
+            self._backup = None
+            log.critical("The backup does not seem encrypted!")
         except Exception as exc:
             self._backup = None
             log.exception(exc)
-            log.critical(
-                "Failed to decrypt backup. Did you provide the correct key file?"
-            )
+            log.critical("Failed to decrypt backup.")
 
     def get_key(self) -> None:
         """Retrieve and prints the encryption key."""

tests/ios_backup/test_decrypt.py

@@ -3,12 +3,15 @@
 # Use of this software is governed by the MVT License 1.1 that can be found at
 #   https://license.mvt.re/1.1/
 
+import hashlib
 import logging
+import plistlib
 import threading
 from pathlib import Path
 
 import pytest
 from Crypto.Cipher import AES
+from iphone_backup_decrypt import IncorrectPassphraseError
 
 from mvt.ios.decrypt import DecryptBackup, MVTEncryptedBackup
 
@@ -24,6 +27,89 @@ def _encrypted_file(backup_path, file_id, key, plaintext):
     source_path.write_bytes(encrypted)
 
 
+def _keybag_tlv(tag, value):
+    return tag + len(value).to_bytes(4, "big") + value
+
+
+def test_derived_key_can_unlock_keybag(mocker, tmp_path, caplog):
+    password = b"backup password"
+    salt = b"salt" * 4
+    dpsl = b"dpsl" * 4
+    round1 = hashlib.pbkdf2_hmac("sha256", password, dpsl, 1, 32)
+    derived_key = hashlib.pbkdf2_hmac("sha1", round1, salt, 1, 32)
+    wrapped_class_key = AES.new(derived_key, AES.MODE_KW).seal(b"k" * 32)
+    keybag_data = b"".join(
+        [
+            _keybag_tlv(b"TYPE", (1).to_bytes(4, "big")),
+            _keybag_tlv(b"DPSL", dpsl),
+            _keybag_tlv(b"DPIC", (1).to_bytes(4, "big")),
+            _keybag_tlv(b"SALT", salt),
+            _keybag_tlv(b"ITER", (1).to_bytes(4, "big")),
+            _keybag_tlv(b"UUID", b"g" * 16),
+            _keybag_tlv(b"WRAP", (2).to_bytes(4, "big")),
+            _keybag_tlv(b"UUID", b"c" * 16),
+            _keybag_tlv(b"CLAS", (1).to_bytes(4, "big")),
+            _keybag_tlv(b"WRAP", (2).to_bytes(4, "big")),
+            _keybag_tlv(b"WPKY", wrapped_class_key),
+        ]
+    )
+    (tmp_path / "Manifest.plist").write_bytes(
+        plistlib.dumps({"IsEncrypted": True, "BackupKeyBag": keybag_data})
+    )
+    (tmp_path / "Manifest.db").touch()
+
+    with pytest.raises(IncorrectPassphraseError):
+        MVTEncryptedBackup(
+            backup_directory=str(tmp_path), passphrase="wrong"
+        )._read_and_unlock_keybag()
+
+    password_backup = MVTEncryptedBackup(
+        backup_directory=str(tmp_path), passphrase=password
+    )
+    password_backup._read_and_unlock_keybag()
+    assert password_backup.get_decryption_key() == derived_key.hex()
+
+    key_backup = MVTEncryptedBackup(
+        backup_directory=str(tmp_path), passphrase_key=derived_key
+    )
+    key_backup._read_and_unlock_keybag()
+    assert key_backup.get_decryption_key() == derived_key.hex()
+
+    # Exercise MVT's password and key-file entry points with the native unlock.
+    mocker.patch.object(DecryptBackup, "is_encrypted", return_value=True)
+    mocker.patch.object(
+        MVTEncryptedBackup,
+        "test_decryption",
+        MVTEncryptedBackup._read_and_unlock_keybag,
+    )
+    password_decryptor = DecryptBackup(str(tmp_path))
+    password_decryptor.decrypt_with_password(password)
+    password_decryptor.get_key()
+    assert password_decryptor._decryption_key == derived_key.hex()
+
+    key_file = tmp_path / "key.txt"
+    key_file.write_text(derived_key.hex())
+    key_decryptor = DecryptBackup(str(tmp_path))
+    key_decryptor.decrypt_with_key_file(str(key_file))
+    assert key_decryptor.can_process()
+    assert key_decryptor._backup.get_decryption_key() == derived_key.hex()
+
+    with caplog.at_level(logging.CRITICAL, logger="mvt.ios.decrypt"):
+        wrong_password = DecryptBackup(str(tmp_path))
+        wrong_password.decrypt_with_password("wrong")
+    assert not wrong_password.can_process()
+    assert "Password is probably wrong" in caplog.text
+
+
+def test_invalid_backup_folder_uses_specific_error(tmp_path, caplog):
+    decryptor = DecryptBackup(str(tmp_path))
+    with caplog.at_level(logging.CRITICAL, logger="mvt.ios.decrypt"):
+        decryptor.decrypt_with_password("password")
+
+    assert not decryptor.can_process()
+    assert "Failed to find a valid backup" in caplog.text
+
+
 def test_extract_file_by_id_preserves_bytes_with_wrong_manifest_size(
     mocker, tmp_path
 ):
@@ -39,13 +125,15 @@ def test_extract_file_by_id_preserves_bytes_with_wrong_manifest_size(
         mtime=None,
     )
     mocker.patch("mvt.ios.decrypt.FilePlist", return_value=file_plist)
+    (tmp_path / "Manifest.plist").touch()
+    (tmp_path / "Manifest.db").touch()
 
     backup = MVTEncryptedBackup(
-        backup_directory=str(tmp_path), derived_key=b"d" * 32
+        backup_directory=str(tmp_path), passphrase_key=b"d" * 32
     )
     mocker.patch.object(backup, "_read_and_unlock_keybag", return_value=True)
-    backup._keybag = mocker.Mock()
-    backup._keybag.unwrapKeyForClass.return_value = inner_key
+    backup.keybag = mocker.Mock()
+    backup.keybag.unwrap_key_for_class.return_value = inner_key
     streaming_decrypt = mocker.spy(backup, "_decrypt_file_to_disk")
     output_path = tmp_path / "output"
 
@@ -57,6 +145,9 @@ def test_extract_file_by_id_preserves_bytes_with_wrong_manifest_size(
 
     assert output_path.read_bytes() == plaintext
     streaming_decrypt.assert_called_once()
+    backup.keybag.unwrap_key_for_class.assert_called_once_with(
+        protection_class=1, wrapped_file_key=b"wrapped-key"
+    )
 
 
 def test_extract_file_by_id_copies_unencrypted_files(mocker, tmp_path):
@@ -67,8 +158,10 @@ def test_extract_file_by_id_copies_unencrypted_files(mocker, tmp_path):
 
     file_plist = mocker.Mock(encryption_key=None)
     mocker.patch("mvt.ios.decrypt.FilePlist", return_value=file_plist)
+    (tmp_path / "Manifest.plist").touch()
+    (tmp_path / "Manifest.db").touch()
     backup = MVTEncryptedBackup(
-        backup_directory=str(tmp_path), derived_key=b"d" * 32
+        backup_directory=str(tmp_path), passphrase_key=b"d" * 32
     )
     mocker.patch.object(backup, "_read_and_unlock_keybag", return_value=True)
     output_path = tmp_path / "output"
@@ -82,6 +175,19 @@ def test_extract_file_by_id_copies_unencrypted_files(mocker, tmp_path):
     assert output_path.read_bytes() == b"plain content"
 
 
+def test_get_decryption_key_uses_unlocked_keybag(tmp_path):
+    (tmp_path / "Manifest.plist").touch()
+    (tmp_path / "Manifest.db").touch()
+    backup = MVTEncryptedBackup(
+        backup_directory=str(tmp_path), passphrase_key=b"d" * 32
+    )
+    with pytest.raises(ValueError, match="No derived key available"):
+        backup.get_decryption_key()
+
+    backup.keybag = type("Keybag", (), {"passphrase_key": b"d" * 32})()
+    assert backup.get_decryption_key() == "64" * 32
+
+
 @pytest.mark.parametrize("with_symlink", [False, True], ids=["file-id", "symlink"])
 def test_process_backup_rejects_unsafe_file_ids_and_destinations(
     mocker, tmp_path, with_symlink

uv.lock

@@ -609,14 +609,14 @@ wheels = [
 
 [[package]]
 name = "iphone-backup-decrypt"
-version = "0.10.0"
+version = "0.11.2"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "pycryptodome" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/01/b8/a2ec2b10d792403d36bb6661fea6357179c31ece1ed3285c442e636d6335/iphone_backup_decrypt-0.10.0.tar.gz", hash = "sha256:5f2799e58f908cce28d7929dd82231abc8acd57c25b37bce6a2d6a82e018d343", size = 20000, upload-time = "2026-09-17T21:46:44Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/ee/f4/a2c3e8bfd937346d87753dd2e7e51efff14744ec268ebafe8e7be0269b9e/iphone_backup_decrypt-0.11.2.tar.gz", hash = "sha256:5f631927419e670e461bc0b9e299fae396445a3c84e0afe747a3464ccbb23ed1", size = 23923, upload-time = "2026-09-24T21:02:17.219Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/89/10/349b2a720e012921d1457e1d1c2b921b16300a5f3570c4c64d0d3787539f/iphone_backup_decrypt-0.10.0-py3-none-any.whl", hash = "sha256:1ac4345a07b104a3eacab20932b8621cd1e0164e0f03d913e66eed6ea5ee173e", size = 17400, upload-time = "2026-09-17T21:46:42Z" },
+    { url = "https://files.pythonhosted.org/packages/7b/33/72414c56bc507b0c104605e16fab2c86465b55567e1aaead8371a4c5884d/iphone_backup_decrypt-0.11.2-py3-none-any.whl", hash = "sha256:f18281997a94313c174aa3839d42db292d198e879fa570799c151ac36ac9c9d7", size = 21779, upload-time = "2026-09-24T21:02:15.878Z" },
 ]
 
 [[package]]
@@ -1038,7 +1038,7 @@ requires-dist = [
     { name = "betterproto2", specifier = "==0.10.0" },
     { name = "click", specifier = "==8.4.2" },
     { name = "cryptography", specifier = "==50.0.0" },
-    { name = "iphone-backup-decrypt", specifier = "==0.10.0" },
+    { name = "iphone-backup-decrypt", specifier = "==0.11.2" },
     { name = "nskeyedunarchiver", specifier = "==1.5.2" },
     { name = "packaging", specifier = "==26.3" },
     { name = "pyahocorasick", specifier = "==2.3.1" },