mirror of https://github.com/mvt-project/mvt.git
212 lines
7.0 KiB
Python
212 lines
7.0 KiB
Python
# Mobile Verification Toolkit (MVT)
|
||
# Copyright (c) 2021-2022 Claudio Guarnieri.
|
||
# Use of this software is governed by the MVT License 1.1 that can be found at
|
||
# https://license.mvt.re/1.1/
|
||
|
||
import datetime
|
||
import io
|
||
import json
|
||
import tarfile
|
||
import zlib
|
||
|
||
from cryptography.hazmat.primitives import hashes, padding
|
||
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
|
||
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
|
||
|
||
from mvt.common.utils import check_for_links, convert_timestamp_to_iso
|
||
|
||
PBKDF2_KEY_SIZE = 32
|
||
|
||
|
||
class AndroidBackupParsingError(Exception):
|
||
"""Exception raised file parsing an android backup file"""
|
||
|
||
|
||
class AndroidBackupNotImplemented(AndroidBackupParsingError):
|
||
pass
|
||
|
||
|
||
class InvalidBackupPassword(AndroidBackupParsingError):
|
||
pass
|
||
|
||
|
||
def to_utf8_bytes(input_bytes):
|
||
output = []
|
||
for byte in input_bytes:
|
||
if byte < ord(b'\x80'):
|
||
output.append(byte)
|
||
else:
|
||
output.append(ord('\xef') | (byte >> 12))
|
||
output.append(ord('\xbc') | ((byte >> 6) & ord('\x3f')))
|
||
output.append(ord('\x80') | (byte & ord('\x3f')))
|
||
return bytes(output)
|
||
|
||
|
||
def parse_ab_header(data):
|
||
"""
|
||
Parse the header of an Android Backup file
|
||
Returns a dict {'backup': True, 'compression': False,
|
||
'encryption': "none", 'version': 4}
|
||
"""
|
||
if data.startswith(b"ANDROID BACKUP"):
|
||
[magic_header, version, is_compressed, encryption, tar_data] = data.split(b"\n", 4)
|
||
return {
|
||
"backup": True,
|
||
"compression": (is_compressed == b"1"),
|
||
"version": int(version),
|
||
"encryption": encryption.decode("utf-8")
|
||
}
|
||
|
||
return {
|
||
"backup": False,
|
||
"compression": None,
|
||
"version": None,
|
||
"encryption": None
|
||
}
|
||
|
||
|
||
def decrypt_master_key(password, user_salt, user_iv, pbkdf2_rounds, master_key_blob, format_version, checksum_salt):
|
||
"""Generate AES key from user password uisng PBKDF2
|
||
|
||
The backup master key is extracted from the master key blog after decryption.
|
||
"""
|
||
# Derive key from password using PBKDF2.
|
||
kdf = PBKDF2HMAC(algorithm=hashes.SHA1(), length=32, salt=user_salt, iterations=pbkdf2_rounds)
|
||
key = kdf.derive(password.encode("utf-8"))
|
||
|
||
# Decrypt master key blob.
|
||
cipher = Cipher(algorithms.AES(key), modes.CBC(user_iv))
|
||
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()
|
||
|
||
# Handle quirky encoding of master key bytes in Android original Java crypto code.
|
||
if format_version > 1:
|
||
hmac_mk = to_utf8_bytes(master_key)
|
||
else:
|
||
hmac_mk = master_key
|
||
|
||
# Derive checksum to confirm successful backup decryption.
|
||
kdf = PBKDF2HMAC(algorithm=hashes.SHA1(), length=32, salt=checksum_salt, iterations=pbkdf2_rounds)
|
||
calculated_checksum = kdf.derive(hmac_mk)
|
||
|
||
if master_key_checksum != calculated_checksum:
|
||
raise InvalidBackupPassword()
|
||
|
||
return master_key, master_iv
|
||
|
||
|
||
def decrypt_backup_data(encrypted_backup, password, encryption_algo, format_version):
|
||
"""
|
||
Generate encryption keyffrom password and do decryption
|
||
|
||
"""
|
||
if encryption_algo != b"AES-256":
|
||
raise AndroidBackupNotImplemented("Encryption Algorithm not implemented")
|
||
|
||
if password is None:
|
||
raise InvalidBackupPassword()
|
||
|
||
[user_salt, checksum_salt, pbkdf2_rounds, user_iv, master_key_blob, encrypted_data] = encrypted_backup.split(b"\n", 5)
|
||
user_salt = bytes.fromhex(user_salt.decode("utf-8"))
|
||
checksum_salt = bytes.fromhex(checksum_salt.decode("utf-8"))
|
||
pbkdf2_rounds = int(pbkdf2_rounds)
|
||
user_iv = bytes.fromhex(user_iv.decode("utf-8"))
|
||
master_key_blob = bytes.fromhex(master_key_blob.decode("utf-8"))
|
||
|
||
# Derive decryption master key from password.
|
||
master_key, master_iv = decrypt_master_key(password=password, user_salt=user_salt, user_iv=user_iv,
|
||
pbkdf2_rounds=pbkdf2_rounds, master_key_blob=master_key_blob,
|
||
format_version=format_version, checksum_salt=checksum_salt)
|
||
|
||
# Decrypt and unpad backup data using derivied key.
|
||
cipher = Cipher(algorithms.AES(master_key), modes.CBC(master_iv))
|
||
decryptor = cipher.decryptor()
|
||
decrypted_tar = decryptor.update(encrypted_data) + decryptor.finalize()
|
||
|
||
unpadder = padding.PKCS7(128).unpadder()
|
||
return unpadder.update(decrypted_tar)
|
||
|
||
|
||
def parse_backup_file(data, password=None):
|
||
"""
|
||
Parse an ab file, returns a tar file
|
||
|
||
"""
|
||
if not data.startswith(b"ANDROID BACKUP"):
|
||
raise AndroidBackupParsingError("Invalid file header")
|
||
|
||
[magic_header, version, is_compressed, encryption_algo, tar_data] = data.split(b"\n", 4)
|
||
version = int(version)
|
||
is_compressed = int(is_compressed)
|
||
|
||
if encryption_algo != b"none":
|
||
tar_data = decrypt_backup_data(tar_data, password, encryption_algo, format_version=version)
|
||
|
||
if is_compressed:
|
||
try:
|
||
tar_data = zlib.decompress(tar_data)
|
||
except zlib.error:
|
||
raise AndroidBackupParsingError("Impossible to decompress the backup file")
|
||
|
||
return tar_data
|
||
|
||
|
||
def parse_tar_for_sms(data):
|
||
"""
|
||
Extract SMS from a tar backup archive
|
||
Returns an array of SMS
|
||
"""
|
||
dbytes = io.BytesIO(data)
|
||
tar = tarfile.open(fileobj=dbytes)
|
||
res = []
|
||
for member in tar.getmembers():
|
||
if member.name.startswith("apps/com.android.providers.telephony/d_f/") and \
|
||
(member.name.endswith("_sms_backup") or member.name.endswith("_mms_backup")):
|
||
dhandler = tar.extractfile(member)
|
||
res.extend(parse_sms_file(dhandler.read()))
|
||
|
||
return res
|
||
|
||
|
||
def parse_sms_file(data):
|
||
"""
|
||
Parse an SMS or MMS file extracted from a backup
|
||
Returns a list of SMS or MMS entries
|
||
"""
|
||
res = []
|
||
data = zlib.decompress(data)
|
||
json_data = json.loads(data)
|
||
|
||
for entry in json_data:
|
||
# Adapt MMS format to SMS format
|
||
if "mms_body" in entry:
|
||
entry["body"] = entry["mms_body"]
|
||
entry.pop("mms_body")
|
||
|
||
message_links = check_for_links(entry["body"])
|
||
|
||
utc_timestamp = datetime.datetime.utcfromtimestamp(int(entry["date"]) / 1000)
|
||
entry["isodate"] = convert_timestamp_to_iso(utc_timestamp)
|
||
entry["direction"] = ("sent" if int(entry["date_sent"]) else "received")
|
||
|
||
# If we find links in the messages or if they are empty we add them to the list.
|
||
if message_links or entry["body"].strip() == "":
|
||
entry["links"] = message_links
|
||
res.append(entry)
|
||
|
||
return res
|