Fix exception with bad password

mvt/android/modules/adb/base.py

@@ -10,6 +10,8 @@ import string
 import sys
 import tempfile
 import time
+import base64
+import getpass
 
 from adb_shell.adb_device import AdbDeviceTcp, AdbDeviceUsb
 from adb_shell.auth.keygen import keygen, write_public_keyfile
@@ -19,7 +21,7 @@ from adb_shell.exceptions import (AdbCommandFailureException, DeviceAuthError,
 from usb1 import USBErrorAccess, USBErrorBusy
 
 from mvt.common.module import InsufficientPrivileges, MVTModule
-from mvt.android.parsers.backup import parse_ab_header, parse_backup_file
+from mvt.android.parsers.backup import parse_ab_header, parse_backup_file, InvalidBackupPassword
 
 log = logging.getLogger(__name__)
 
@@ -244,7 +246,7 @@ class AndroidExtraction(MVTModule):
         # Disconnect from the device.
         self._adb_disconnect()
 
-    def _generate_backup(package_name):
+    def _generate_backup(self, package_name):
         # Run ADB command to create a backup of SMS app
         self.log.warning("Please check phone and accept Android backup prompt. You may need to set a backup password. \a")
 
@@ -253,6 +255,7 @@ class AndroidExtraction(MVTModule):
         backup_output_b64 = self._adb_command("/system/bin/bu backup -nocompress '{}' | base64".format(package_name))
         backup_output = base64.b64decode(backup_output_b64)
         header = parse_ab_header(backup_output)
+
         if not header["backup"]:
             self.log.error("Extracting SMS via Android backup failed. No valid backup data found.")
             return
@@ -261,7 +264,7 @@ class AndroidExtraction(MVTModule):
             return parse_backup_file(backup_output, password=None)
 
         # Backup encrypted. Request password from user.
-        while password_retry in range(0, 3):
+        for password_retry in range(0, 3):
             backup_password = getpass.getpass(prompt="Backup Password: ", stream=None)
             try:
                 decrypted_backup_tar = parse_backup_file(backup_output, backup_password)

mvt/android/modules/adb/sms.py

@@ -117,6 +117,9 @@ class SMS(AndroidExtraction):
         algorithim. This module only supports an unencrypted ADB backup.
         """
         backup_tar = self._generate_backup("com.android.providers.telephony")
+        if not backup_tar:
+            return
+
         try:
             self.results = parse_tar_for_sms(backup_tar)
         except AndroidBackupParsingError:

mvt/android/parsers/backup.py

@@ -78,20 +78,20 @@ def decrypt_master_key(password, user_salt, user_iv, pbkdf2_rounds, master_key_b
     decryptor = cipher.decryptor()
     try:
         decryted_master_key_blob = decryptor.update(master_key_blob) + decryptor.finalize()
+
+        # Extract key and IV from decrypted blob.
+        key_blob = io.BytesIO(decryted_master_key_blob)
+        master_iv_length = ord(key_blob.read(1))
+        master_iv = key_blob.read(master_iv_length)
+
+        master_key_length = ord(key_blob.read(1))
+        master_key = key_blob.read(master_key_length)
+
+        master_key_checksum_length = ord(key_blob.read(1))
+        master_key_checksum = key_blob.read(master_key_checksum_length)
     except TypeError:
         raise InvalidBackupPassword()
 
-    # Extract key and IV from decrypted blob.
-    key_blob = io.BytesIO(decryted_master_key_blob)
-    master_iv_length = ord(key_blob.read(1))
-    master_iv = key_blob.read(master_iv_length)
-
-    master_key_length = ord(key_blob.read(1))
-    master_key = key_blob.read(master_key_length)
-
-    master_key_checksum_length = ord(key_blob.read(1))
-    master_key_checksum = key_blob.read(master_key_checksum_length)
-
     # Handle quirky encoding of master key bytes in Android original Java crypto code
     if format_version > 1:
         hmac_mk = to_utf8_bytes(master_key)