安全研究人员Jean-Baptiste Bédrune和Jean Sigwald在Hack-in-the-box Amsterdam 2011上展示了如何做到这一点。您可以参考此处。
自那时起，苹果公司发布了一份
iOS安全白皮书，其中包含有关密钥和算法的更多详细信息，Charlie Miller等人也发布了
iOS黑客手册，介绍了一些相同的内容。当iOS 10首次推出时，备份格式发生了变化，苹果一开始没有公开宣布这些变化，但是各种人
对格式进行了反向工程处理。
加密备份非常好
加密iPhone备份的好处在于，它们包含像WiFi密码之类的东西，而这些东西不在常规的未加密备份中。正如
iOS安全白皮书所讨论的那样，加密备份被认为更“安全”，因此苹果认为可以在其中包含更敏感的信息。
一个重要的警告：显然，解密您的iOS设备备份会取消其加密。为了保护您的隐私和安全，
您应该只在具有全盘加密的计算机上运行这些脚本。虽然安全专家可以编写保护内存中密钥的软件，例如使用
VirtualLock()和
SecureZeroMemory()等函数，但是这些Python脚本将在字符串中存储您的加密密钥和密码，以供Python进行垃圾回收。这意味着您的秘密密钥和密码将在RAM中存活一段时间，然后泄漏到交换文件和磁盘上，敌方可以恢复它们。这完全违背了拥有加密备份的目的。
如何解密备份：理论上
iOS安全白皮书比我更好地解释了每个文件的密钥、保护类、保护类密钥和密钥包的基本概念。如果您还不熟悉这些内容，请花几分钟阅读相关部分。
现在您知道iOS中的每个文件都使用自己的随机密钥进行加密，属于一种保护类，而每个文件的加密密钥存储在文件系统元数据中，并包装在保护类密钥中。
要解密：
解码存储在Manifest.plist的BackupKeyBag条目中的密钥包。whitepaper提供了此结构的高级概述。iPhone Wiki描述了二进制格式：4字节字符串类型字段、4字节大端长度字段，然后是值本身。
重要的值是PBKDF2 ITERations和SALT，双层保护盐DPSL和迭代次数DPIC，以及对于每个保护CLS，WPKY包装密钥。
使用备份密码使用正确的PBKDF2盐和迭代次数派生32字节密钥。首先使用带有DPSL和DPIC的SHA256轮，然后使用带有ITER和SALT的SHA1轮。
根据RFC 3394展开每个包装密钥。
通过从Manifest.plist的ManifestKey中获取4字节保护类和更长的密钥并展开它来解密清单数据库。现在您拥有一个包含所有文件元数据的SQLite数据库。
对于每个感兴趣的文件，通过查看Files.file数据库列中包含EncryptionKey和ProtectionClass条目的二进制plist来获取类加密的每个文件加密密钥和保护类代码。在使用之前，请从EncryptionKey中删除初始的四字节长度标记。
然后，通过使用使用备份密码展开的类密钥来展开它，派生出最终的解密密钥。然后使用CBC模式下的AES解密文件，IV为零。
如何实践解密备份
首先，您需要一些库依赖项。如果您正在使用homebrew安装的Python 2.7或3.7的Mac，则可以使用以下命令安装依赖项：
CFLAGS="-I$(brew --prefix)/opt/openssl/include" \
LDFLAGS="-L$(brew --prefix)/opt/openssl/lib" \
pip install biplist fastpbkdf2 pycrypto
在可运行的源代码形式中，以下是如何解密来自加密iPhone备份的单个首选项文件的方法：
from __future__ import print_function
from __future__ import division
import argparse
import getpass
import os.path
import pprint
import random
import shutil
import sqlite3
import string
import struct
import tempfile
from binascii import hexlify
import Crypto.Cipher.AES
import biplist
import fastpbkdf2
from biplist import InvalidPlistException
def main():
parser = argparse.ArgumentParser()
parser.add_argument('--backup-directory', dest='backup_directory',
default='testdata/encrypted')
parser.add_argument('--password-pipe', dest='password_pipe',
help="""\
Keeps password from being visible in system process list.
Typical use: --password-pipe=<(echo -n foo)
""")
parser.add_argument('--no-anonymize-output', dest='anonymize',
action='store_false')
args = parser.parse_args()
global ANONYMIZE_OUTPUT
ANONYMIZE_OUTPUT = args.anonymize
if ANONYMIZE_OUTPUT:
print('Warning: All output keys are FAKE to protect your privacy')
manifest_file = os.path.join(args.backup_directory, 'Manifest.plist')
with open(manifest_file, 'rb') as infile:
manifest_plist = biplist.readPlist(infile)
keybag = Keybag(manifest_plist['BackupKeyBag'])
keybag.printClassKeys()
if args.password_pipe:
password = readpipe(args.password_pipe)
if password.endswith(b'\n'):
password = password[:-1]
else:
password = getpass.getpass('Backup password: ').encode('utf-8')
if not keybag.unlockWithPasscode(password):
raise Exception('Could not unlock keybag; bad password?')
keybag.printClassKeys()
manifest_key = manifest_plist['ManifestKey'][4:]
with open(os.path.join(args.backup_directory, 'Manifest.db'), 'rb') as db:
encrypted_db = db.read()
manifest_class = struct.unpack('<l', manifest_plist['ManifestKey'][:4])[0]
key = keybag.unwrapKeyForClass(manifest_class, manifest_key)
decrypted_data = AESdecryptCBC(encrypted_db, key)
temp_dir = tempfile.mkdtemp()
try:
db_filename = os.path.join(temp_dir, 'db.sqlite3')
with open(db_filename, 'wb') as db_file:
db_file.write(decrypted_data)
conn = sqlite3.connect(db_filename)
conn.row_factory = sqlite3.Row
c = conn.cursor()
c.execute("""
SELECT fileID, domain, relativePath, file
FROM Files
WHERE relativePath LIKE 'Media/PhotoData/MISC/DCIM_APPLE.plist'
ORDER BY domain, relativePath""")
results = c.fetchall()
finally:
shutil.rmtree(temp_dir)
for item in results:
fileID, domain, relativePath, file_bplist = item
plist = biplist.readPlistFromString(file_bplist)
file_data = plist['$objects'][plist['$top']['root'].integer]
size = file_data['Size']
protection_class = file_data['ProtectionClass']
encryption_key = plist['$objects'][
file_data['EncryptionKey'].integer]['NS.data'][4:]
backup_filename = os.path.join(args.backup_directory,
fileID[:2], fileID)
with open(backup_filename, 'rb') as infile:
data = infile.read()
key = keybag.unwrapKeyForClass(protection_class, encryption_key)
decrypted_data = AESdecryptCBC(data, key)[:size]
print('== decrypted data:')
print(wrap(decrypted_data))
print()
print('== pretty-printed plist')
pprint.pprint(biplist.readPlistFromString(decrypted_data))
CLASSKEY_TAGS = [b"CLAS",b"WRAP",b"WPKY", b"KTYP", b"PBKY"]
KEYBAG_TYPES = ["System", "Backup", "Escrow", "OTA (icloud)"]
KEY_TYPES = ["AES", "Curve25519"]
PROTECTION_CLASSES={
1:"NSFileProtectionComplete",
2:"NSFileProtectionCompleteUnlessOpen",
3:"NSFileProtectionCompleteUntilFirstUserAuthentication",
4:"NSFileProtectionNone",
5:"NSFileProtectionRecovery?",
6: "kSecAttrAccessibleWhenUnlocked",
7: "kSecAttrAccessibleAfterFirstUnlock",
8: "kSecAttrAccessibleAlways",
9: "kSecAttrAccessibleWhenUnlockedThisDeviceOnly",
10: "kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly",
11: "kSecAttrAccessibleAlwaysThisDeviceOnly"
}
WRAP_DEVICE = 1
WRAP_PASSCODE = 2
class Keybag(object):
def __init__(self, data):
self.type = None
self.uuid = None
self.wrap = None
self.deviceKey = None
self.attrs = {}
self.classKeys = {}
self.KeyBagKeys = None
self.parseBinaryBlob(data)
def parseBinaryBlob(self, data):
currentClassKey = None
for tag, data in loopTLVBlocks(data):
if len(data) == 4:
data = struct.unpack(">L", data)[0]
if tag == b"TYPE":
self.type = data
if self.type > 3:
print("FAIL: keybag type > 3 : %d" % self.type)
elif tag == b"UUID" and self.uuid is None:
self.uuid = data
elif tag == b"WRAP" and self.wrap is None:
self.wrap = data
elif tag == b"UUID":
if currentClassKey:
self.classKeys[currentClassKey[b"CLAS"]] = currentClassKey
currentClassKey = {b"UUID": data}
elif tag in CLASSKEY_TAGS:
currentClassKey[tag] = data
else:
self.attrs[tag] = data
if currentClassKey:
self.classKeys[currentClassKey[b"CLAS"]] = currentClassKey
def unlockWithPasscode(self, passcode):
passcode1 = fastpbkdf2.pbkdf2_hmac('sha256', passcode,
self.attrs[b"DPSL"],
self.attrs[b"DPIC"], 32)
passcode_key = fastpbkdf2.pbkdf2_hmac('sha1', passcode1,
self.attrs[b"SALT"],
self.attrs[b"ITER"], 32)
print('== Passcode key')
print(anonymize(hexlify(passcode_key)))
for classkey in self.classKeys.values():
if b"WPKY" not in classkey:
continue
k = classkey[b"WPKY"]
if classkey[b"WRAP"] & WRAP_PASSCODE:
k = AESUnwrap(passcode_key, classkey[b"WPKY"])
if not k:
return False
classkey[b"KEY"] = k
return True
def unwrapKeyForClass(self, protection_class, persistent_key):
ck = self.classKeys[protection_class][b"KEY"]
if len(persistent_key) != 0x28:
raise Exception("Invalid key length")
return AESUnwrap(ck, persistent_key)
def printClassKeys(self):
print("== Keybag")
print("Keybag type: %s keybag (%d)" % (KEYBAG_TYPES[self.type], self.type))
print("Keybag version: %d" % self.attrs[b"VERS"])
print("Keybag UUID: %s" % anonymize(hexlify(self.uuid)))
print("-"*209)
print("".join(["Class".ljust(53),
"WRAP".ljust(5),
"Type".ljust(11),
"Key".ljust(65),
"WPKY".ljust(65),
"Public key"]))
print("-"*208)
for k, ck in self.classKeys.items():
if k == 6:print("")
print("".join(
[PROTECTION_CLASSES.get(k).ljust(53),
str(ck.get(b"WRAP","")).ljust(5),
KEY_TYPES[ck.get(b"KTYP",0)].ljust(11),
anonymize(hexlify(ck.get(b"KEY", b""))).ljust(65),
anonymize(hexlify(ck.get(b"WPKY", b""))).ljust(65),
]))
print()
def loopTLVBlocks(blob):
i = 0
while i + 8 <= len(blob):
tag = blob[i:i+4]
length = struct.unpack(">L",blob[i+4:i+8])[0]
data = blob[i+8:i+8+length]
yield (tag,data)
i += 8 + length
def unpack64bit(s):
return struct.unpack(">Q",s)[0]
def pack64bit(s):
return struct.pack(">Q",s)
def AESUnwrap(kek, wrapped):
C = []
for i in range(len(wrapped)//8):
C.append(unpack64bit(wrapped[i*8:i*8+8]))
n = len(C) - 1
R = [0] * (n+1)
A = C[0]
for i in range(1,n+1):
R[i] = C[i]
for j in reversed(range(0,6)):
for i in reversed(range(1,n+1)):
todec = pack64bit(A ^ (n*j+i))
todec += pack64bit(R[i])
B = Crypto.Cipher.AES.new(kek).decrypt(todec)
A = unpack64bit(B[:8])
R[i] = unpack64bit(B[8:])
if A != 0xa6a6a6a6a6a6a6a6:
return None
res = b"".join(map(pack64bit, R[1:]))
return res
ZEROIV = "\x00"*16
def AESdecryptCBC(data, key, iv=ZEROIV, padding=False):
if len(data) % 16:
print("AESdecryptCBC: data length not /16, truncating")
data = data[0:(len(data)/16) * 16]
data = Crypto.Cipher.AES.new(key, Crypto.Cipher.AES.MODE_CBC, iv).decrypt(data)
if padding:
return removePadding(16, data)
return data
anon_random = random.Random(0)
memo = {}
def anonymize(s):
if type(s) == str:
s = s.encode('utf-8')
global anon_random, memo
if ANONYMIZE_OUTPUT:
if s in memo:
return memo[s]
possible_alphabets = [
string.digits,
string.digits + 'abcdef',
string.ascii_letters,
"".join(chr(x) for x in range(0, 256)),
]
for a in possible_alphabets:
if all((chr(c) if type(c) == int else c) in a for c in s):
alphabet = a
break
ret = "".join([anon_random.choice(alphabet) for i in range(len(s))])
memo[s] = ret
return ret
else:
return s
def wrap(s, width=78):
"Return a width-wrapped repr(s)-like string without breaking on \’s"
s = repr(s)
quote = s[0]
s = s[1:-1]
ret = []
while len(s):
i = s.rfind('\\', 0, width)
if i <= width - 4:
i = width
ret.append(s[:i])
s = s[i:]
return '\n'.join("%s%s%s" % (quote, line ,quote) for line in ret)
def readpipe(path):
if stat.S_ISFIFO(os.stat(path).st_mode):
with open(path, 'rb') as pipe:
return pipe.read()
else:
raise Exception("Not a pipe: {!r}".format(path))
if __name__ == '__main__':
main()
然后打印出这个输出：
Warning: All output keys are FAKE to protect your privacy
== Keybag
Keybag type: Backup keybag (1)
Keybag version: 3
Keybag UUID: dc6486c479e84c94efce4bea7169ef7d
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Class WRAP Type Key WPKY Public key
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NSFileProtectionComplete 2 AES 4c80b6da07d35d393fc7158e18b8d8f9979694329a71ceedee86b4cde9f97afec197ad3b13c5d12b
NSFileProtectionCompleteUnlessOpen 2 AES 09e8a0a9965f00f213ce06143a52801f35bde2af0ad54972769845d480b5043f545fa9b66a0353a6
NSFileProtectionCompleteUntilFirstUserAuthentication 2 AES e966b6a0742878ce747cec3fa1bf6a53b0d811ad4f1d6147cd28a5d400a8ffe0bbabea5839025cb5
NSFileProtectionNone 2 AES 902f46847302816561e7df57b64beea6fa11b0068779a65f4c651dbe7a1630f323682ff26ae7e577
NSFileProtectionRecovery? 3 AES a3935fed024cd9bc11d0300d522af8e89accfbe389d7c69dca02841df46c0a24d0067dba2f696072
kSecAttrAccessibleWhenUnlocked 2 AES 09a1856c7e97a51a9c2ecedac8c3c7c7c10e7efa931decb64169ee61cb07a0efb115050fd1e33af1
kSecAttrAccessibleAfterFirstUnlock 2 AES 0509d215f2f574efa2f192efc53c460201168b26a175f066b5347fc48bc76c637e27a730b904ca82
kSecAttrAccessibleAlways 2 AES b7ac3c4f1e04896144ce90c4583e26489a86a6cc45a2b692a5767b5a04b0907e081daba009fdbb3c
kSecAttrAccessibleWhenUnlockedThisDeviceOnly 3 AES 417526e67b82e7c6c633f9063120a299b84e57a8ffee97b34020a2caf6e751ec5750053833ab4d45
kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly 3 AES b0e17b0cf7111c6e716cd0272de5684834798431c1b34bab8d1a1b5aba3d38a3a42c859026f81ccc
kSecAttrAccessibleAlwaysThisDeviceOnly 3 AES 9b3bdc59ae1d85703aa7f75d49bdc600bf57ba4a458b20a003a10f6e36525fb6648ba70e6602d8b2
== Passcode key
ee34f5bb635830d698074b1e3e268059c590973b0f1138f1954a2a4e1069e612
== Keybag
Keybag type: Backup keybag (1)
Keybag version: 3
Keybag UUID: dc6486c479e84c94efce4bea7169ef7d
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Class WRAP Type Key WPKY Public key
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NSFileProtectionComplete 2 AES 64e8fc94a7b670b0a9c4a385ff395fe9ba5ee5b0d9f5a5c9f0202ef7fdcb386f 4c80b6da07d35d393fc7158e18b8d8f9979694329a71ceedee86b4cde9f97afec197ad3b13c5d12b
NSFileProtectionCompleteUnlessOpen 2 AES 22a218c9c446fbf88f3ccdc2ae95f869c308faaa7b3e4fe17b78cbf2eeaf4ec9 09e8a0a9965f00f213ce06143a52801f35bde2af0ad54972769845d480b5043f545fa9b66a0353a6
NSFileProtectionCompleteUntilFirstUserAuthentication 2 AES 1004c6ca6e07d2b507809503180edf5efc4a9640227ac0d08baf5918d34b44ef e966b6a0742878ce747cec3fa1bf6a53b0d811ad4f1d6147cd28a5d400a8ffe0bbabea5839025cb5
NSFileProtectionNone 2 AES 2e809a0cd1a73725a788d5d1657d8fd150b0e360460cb5d105eca9c60c365152 902f46847302816561e7df57b64beea6fa11b0068779a65f4c651dbe7a1630f323682ff26ae7e577
NSFileProtectionRecovery? 3 AES 9a078d710dcd4a1d5f70ea4062822ea3e9f7ea034233e7e290e06cf0d80c19ca a3935fed024cd9bc11d0300d522af8e89accfbe389d7c69dca02841df46c0a24d0067dba2f696072
kSecAttrAccessibleWhenUnlocked 2 AES 606e5328816af66736a69dfe5097305cf1e0b06d6eb92569f48e5acac3f294a4 09a1856c7e97a51a9c2ecedac8c3c7c7c10e7efa931decb64169ee61cb07a0efb115050fd1e33af1
kSecAttrAccessibleAfterFirstUnlock 2 AES 6a4b5292661bac882338d5ebb51fd6de585befb4ef5f8ffda209be8ba3af1b96 0509d215f2f574efa2f192efc53c460201168b26a175f066b5347fc48bc76c637e27a730b904ca82
kSecAttrAccessibleAlways 2 AES c0ed717947ce8d1de2dde893b6026e9ee1958771d7a7282dd2116f84312c2dd2 b7ac3c4f1e04896144ce90c4583e26489a86a6cc45a2b692a5767b5a04b0907e081daba009fdbb3c
kSecAttrAccessibleWhenUnlockedThisDeviceOnly 3 AES 80d8c7be8d5103d437f8519356c3eb7e562c687a5e656cfd747532f71668ff99 417526e67b82e7c6c633f9063120a299b84e57a8ffee97b34020a2caf6e751ec5750053833ab4d45
kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly 3 AES a875a15e3ff901351c5306019e3b30ed123e6c66c949bdaa91fb4b9a69a3811e b0e17b0cf7111c6e716cd0272de5684834798431c1b34bab8d1a1b5aba3d38a3a42c859026f81ccc
kSecAttrAccessibleAlwaysThisDeviceOnly 3 AES 1e7756695d337e0b06c764734a9ef8148af20dcc7a636ccfea8b2eb96a9e9373 9b3bdc59ae1d85703aa7f75d49bdc600bf57ba4a458b20a003a10f6e36525fb6648ba70e6602d8b2
== decrypted data:
'<?xml version="1.0" encoding="UTF-8"?>\n<!DOCTYPE plist PUBLIC "-//Apple//DTD '
'PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">\n<plist versi'
'on="1.0">\n<dict>\n\t<key>DCIMLastDirectoryNumber</key>\n\t<integer>100</integ'
'er>\n\t<key>DCIMLastFileNumber</key>\n\t<integer>3</integer>\n</dict>\n</plist'
'>\n'
== pretty-printed plist
{'DCIMLastDirectoryNumber': 100, 'DCIMLastFileNumber': 3}
额外加分项
Bédrune和Sigwald发布的iphone-dataprotection code可以解密备份中的关键链，包括保存的wifi和网站密码等有趣内容：
$ python iphone-dataprotection/python_scripts/keychain_tool.py ...
--------------------------------------------------------------------------------------
| Passwords |
--------------------------------------------------------------------------------------
|Service |Account |Data |Access group |Protection class|
--------------------------------------------------------------------------------------
|AirPort |Ed’s Coffee Shop |<3FrenchRoast |apple |AfterFirstUnlock|
...
那段代码已经无法在使用最新iOS的手机备份上运行，但是有一些golang 端口已经得到更新，可以访问钥匙串。
