From be511dcb515b74f0f6973852b811a052ccf9bdaa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Donncha=20=C3=93=20Cearbhaill?=
 <donncha.ocearbhaill@amnesty.org>
Date: Fri, 4 Mar 2022 17:06:10 +0100
Subject: [PATCH] Refactor SMS ADB code to use backup functions

---
 mvt/android/modules/adb/base.py | 28 ++++++++++++++++++++++++++++
 mvt/android/modules/adb/sms.py  | 25 +++----------------------
 mvt/android/parsers/backup.py   |  8 --------
 3 files changed, 31 insertions(+), 30 deletions(-)

diff --git a/mvt/android/modules/adb/base.py b/mvt/android/modules/adb/base.py
index 2ad9b87..6d4bfb8 100644
--- a/mvt/android/modules/adb/base.py
+++ b/mvt/android/modules/adb/base.py
@@ -19,6 +19,7 @@ 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
 
 log = logging.getLogger(__name__)
 
@@ -243,6 +244,33 @@ class AndroidExtraction(MVTModule):
         # Disconnect from the device.
         self._adb_disconnect()
 
+    def _generate_backup(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")
+
+        # Run ADB command to create a backup of SMS app
+        # TODO: Base64 encoding as temporary fix to avoid byte-mangling over the shell transport...
+        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
+
+        if header["encryption"] == "none":
+            return parse_backup_file(backup_output, password=None)
+
+        # Backup encrypted. Request password from user.
+        while 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)
+                return decrypted_backup_tar
+            except InvalidBackupPassword:
+                self.log.info("Invalid backup password")
+
+        self.log.warn("All attempts to decrypt backup with password failed!")
+
     def run(self):
         """Run the main procedure."""
         raise NotImplementedError
diff --git a/mvt/android/modules/adb/sms.py b/mvt/android/modules/adb/sms.py
index 10000db..d323cd1 100644
--- a/mvt/android/modules/adb/sms.py
+++ b/mvt/android/modules/adb/sms.py
@@ -10,7 +10,7 @@ import base64
 import getpass
 
 from mvt.common.utils import check_for_links, convert_timestamp_to_iso
-from mvt.android.parsers.backup import parse_ab_header, parse_sms_backup, InvalidBackupPassword, AndroidBackupParsingError
+from mvt.android.parsers.backup import parse_tar_for_sms, AndroidBackupParsingError
 from mvt.common.module import InsufficientPrivileges
 
 from .base import AndroidExtraction
@@ -116,28 +116,9 @@ class SMS(AndroidExtraction):
         It is crucial to use the under-documented "-nocompress" flag to disable the non-standard Java compression
         algorithim. This module only supports an unencrypted ADB backup.
         """
-        # Run ADB command to create a backup of SMS app
-        self.log.warning("Please check phone and accept Android backup prompt. Do not set an encryption password. \a")
-
-        # Run ADB command to create a backup of SMS app
-        # TODO: Base64 encoding as temporary fix to avoid byte-mangling over the shell transport...
-        backup_output_b64 = self._adb_command("/system/bin/bu backup -nocompress com.android.providers.telephony | base64")
-        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
-
-        pwd = None
-        if header["encryption"] != "none":
-            pwd = getpass.getpass(prompt="Backup Password: ", stream=None)
-
-
+        backup_tar = self._generate_backup("com.android.providers.telephony")
         try:
-            self.results = parse_sms_backup(backup_output, password=pwd)
-        except InvalidBackupPassword:
-            self.log.info("Invalid backup password")
-            return
+            self.results = parse_tar_for_sms(backup_tar)
         except AndroidBackupParsingError:
             self.log.info("Impossible to read SMS from the Android Backup, please extract the SMS and try extracting it with Android Backup Extractor")
             return
diff --git a/mvt/android/parsers/backup.py b/mvt/android/parsers/backup.py
index c9c2a1d..85b1865 100644
--- a/mvt/android/parsers/backup.py
+++ b/mvt/android/parsers/backup.py
@@ -42,14 +42,6 @@ def to_utf8_bytes(input_bytes):
     return bytes(output)
 
 
-def parse_sms_backup(data, password=None):
-    """
-    Parse a backup file and returns SMS in it
-    """
-    tardata = parse_backup_file(data, password=password)
-    return parse_tar_for_sms(tardata)
-
-
 def parse_ab_header(data):
     """
     Parse the header of an Android Backup file