Cracking and Analyzing Apple iCloud презентация

Содержание

The need for iOS forensics More than 5 years on the market 7 iPhones, 5 iPods, 5 iPads 320+ million iPhones, 280+ million iPods, 120+ million iPads sold worldwide “Smart

Слайд 1Cracking and Analyzing Apple iCloud backups, Find My iPhone, Document Storage
CanSecWest

2013
Vladimir Katalov, ElcomSoft Co. Ltd.

Слайд 2The need for iOS forensics

More than 5 years on the market
7

iPhones, 5 iPods, 5 iPads
320+ million iPhones, 280+ million iPods, 120+ million iPads sold worldwide
“Smart devices” – they do carry a lot of sensitive data
Corporate deployments are increasing

Слайд 3iOS data protection

Device passcode
Protect unauthorized access to the device
Bypassing is not

enough (used in encryption)
Disk encryption
Keychain
System-wide storage for sensitive data (keys, passwords etc)
Data is encrypted

Слайд 4iOS forensics
Logical acquisition (iTunes backups)
Physical acquisition
iCloud backups and storage


Слайд 5iOS forensics
- logical acquisition

“Ask” device to produce backup
Device must be unlocked

(by passcode or iTunes)
Device may produce encrypted backup
Limited amount of information

Слайд 6iOS forensics
- physical acquisition
Boot-time exploit to run unsigned code
or
Jailbreak

Device lock state

isn’t relevant, can bruteforce passcode
Can get all information from the device

Слайд 7iOS Data Protection
Every iOS device contains secure AES engine with two

embedded keys:
GID – shared by all devices of same “family”
UID – unique per device
Newer devices have additional UID+ key
There is no known way to extract GID or UID

Слайд 8iOS data protection (cont-d)
Content grouped by accessibility requirements:
Available only when device

is unlocked
Available after first device unlock (and until power off)
Always available
Each protection class has a master key
Master keys are protected by device key and passcode
Protected master keys form system keybag
New keys created during device restore

Слайд 9iOS 4+ passcode
Passcode is used to compute passcode key
Computation is tied

to hardware key (UID/UID+)
Same passcode will yield different passcode keys on different devices!
Passcode key is required to unlock most keys from the system keybag
Most files are protected with NSProtectionNone and don’t require a passcode
Most keychain items are protected with ...WhenUnlocked or ...AfterFirstUnlock and require a passcode

Слайд 10iOS 4+ passcode (cont-d)

Passcode-to-Key transformation is slow
Offline brute-force currently is not

possible
Requires extracting UID/UID+ key
On-device bruteforce is slow
2 p/s on iPhone 3G, 7 p/s on iPad
System keybag contains hint on password complexity

Слайд 11iOS 4+ passcode (cont-d)


Слайд 12iOS 5 Keychain

SQLite3 DB, all columns are encrypted Available protection classes
kSecAttrAccessibleWhenUnlocked

(+ ...ThisDeviceOnly)
kSecAttrAccessibleAfterFirstUnlock (+ ...ThisDeviceOnly)
kSecAttrAccessibleAlways (+ ...ThisDeviceOnly)
Random key for each item (AES)
Item key is protected with corresponding protection class master key

Слайд 13iOS 5 Storage

Only User partition is encrypted
Available protection classes:
NSProtectionNone
NSProtectionComplete
NSFileProtectionCompleteUntilFirstUserAuthentication
NSFileProtectionCompleteUnlessOpen
Per-file random encryption

key
File key protected with master key is stored in extended attributes (pretty much like Microsoft EFS)
No protection class - partition key is used
File system metadata and unprotected files
Transparent encryption and decryption (same as pre-iOS 4)

Слайд 14iCloud

Introduced in Oct 2011
Introduced with iOS 5
Successor to MobileMe, .Mac, iTools
5

GB free storage
Up to 50 GB paid storage
Over 125 million users in April 2012

Слайд 15iCloud services


Слайд 16iCloud Control Panel


Слайд 17iPhone backup - why?


Слайд 18Mission: impossible :)


Слайд 19iCloud backup - what
Messages (including iMessages)
Application data
Device settings
Camera roll (photos and

videos)
Visual voicemails
Purchases (music, movies, TV, apps, books)
Home screen arrangement
Ringtones

Слайд 20iCloud backup - when

Backup runs daily when device is:
Connected to the

Internet over Wi-Fi
Connected to a power source
Locked
Can force backup
[Settings] | [iCloud] | [Storage & Backup] | [Back Up Now]

Слайд 21iCloud backup - how


Слайд 22iCloud CP: backups


Слайд 23iCloud backup protocol flow

Dynamic: endpoints depend on Apple ID
Built on Google

Protocol Buffers (mostly)
Files are split into chunks
Apple provides file-to-chunks mapping, chunk encryption keys, and full request info to 3rd-party storage provider (Amazon/Microsoft)
Encryption key depends on chunk data (deduplication?)

Слайд 24iCloud backup protocol flow (cont-d)
/mbs/

List of backups

/mbs///getKeys

OTA backup keybag

/mbs////listFiles

File manifest

/mbs////getFiles

File auth

tokens

/mbs//authorizeGet

Info about containers of chunks for "les (FileGroups)

Request containers of chunks (FileGroups)

Containers of chunks

Слайд 25iCloud encryption
Data stored at 3rd-party storage providers is encrypted
Apple has encryption

keys to that data
Few files are further encrypted using keys from OTA backup keybag
Keychain items are encrypted using keys from OTA backup keybag
Need key 0x835 (securityd) to decrypt most keys from OTA backup keybag

Слайд 26iCloud backups - summary

There is no user-con"gurable encryption for iCloud backups
iCloud

backups are stored in Microsoft and Amazon clouds in encrypted form
Apple holds encryption keys and thus have access to data in iCloud backups
If Apple stores 0x835 keys then it can also have access to Keychain data (i.e. passwords)
Apple may have legal obligations to do this (e.g. LE)

Слайд 27Find My Phone


Слайд 28FindMyPhone protocol


Слайд 29FindMyPhone - demo output


Слайд 30iCloud documents


Слайд 31iCloud CP: documents


Слайд 32Get files from iCloud
To get list of files

Authentication request (with given

AppleID & password). Client gets mmeAuthToken in return; which, in order, is used to create authentication token (together with dsid). dsid (Destination Signaling IDentifier) is an unique ID assigned to the user when registering at iCloud.com.

Request to get AccountSettings. Client gets an URL (ubiquityUrl) with an address to get UUID (unique user identifier), file list, info on file tokens and for authorization.

Request to get file list (POST). Output (for every file):

file name
file id
parent folder id
last change time
checksum
access rights

To download given file

Request to get file token (using file id, checksum and aliasMap).

Authorization request. Returns information on file chunks and containers. Output: container list (with URLs) and chunk information.

Слайд 33Files in iCloud


Слайд 35iCloud docs: demo output


Слайд 36Possible usage
Backups in iCloud
near-realtime acquisition (SMS, iMessage, mail, call logs)
browse backup

data without actual device
download only data of specific type (need further work)
Find My Phone
keep track
using Google Maps (or whatever)
enter/leave some are
2+ devices
Documents in iCloud
open from 3rd party apps
track changes
download unsupported document data

Forensics!

Слайд 37Conclusion
Balance between security, privacy and convenience
iCloud security risks
Use additional encryption
Need further

work (contacts, calendar, mode documents, converting documents, partial backup download, decrypting keychain, photo stream, 3rd party apps data: 1Password etc)

Слайд 38Thank you!

Cracking and Analyzing Apple iCloud backups, Find My iPhone, Document

Storage

CanSecWest 2013
Vladimir Katalov, ElcomSoft Co. Ltd.

http://www.elcomsoft.com
http://blog.crackpassword.com
Facebook: ElcomSoft
Twitter: @elcomsoft


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