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Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
Belenko, sklyarov   dark and bright sides of i cloud (in)security
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Belenko, sklyarov dark and bright sides of i cloud (in)security

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  • 1. Dark and Bright Sides of the iCloud (In)Security Andrey Belenko Dmitry Sklyarov Sr. Security Engineer Lead Analyst viaForensics Positive TechnologiesTuesday, 20 November 12 1
  • 2. Disclaimer This work has been done in early 2012 while we have been still working for (and receiving paychecks from) Elcomsoft. Permission has been obtained prior to preparing this presentation and we are thankful to Elcomsoft for providing such permission. Elcomsoft also offers a commercial tool (based on this research) that can download iCloud backups.Tuesday, 20 November 12 2
  • 3. Motivation Mobile device forensicsTuesday, 20 November 12 3
  • 4. Motivation Devices are becoming increasingly interconnected but forensic tools are not ready for this (yet)Tuesday, 20 November 12 4
  • 5. Motivation iCloud is the natural target as it is quite big and popularTuesday, 20 November 12 5
  • 6. Motivation So it is about iOS forensics in the first placeTuesday, 20 November 12 6
  • 7. Forensics 101 Acquisition ➜ Analysis ➜ Reporting GOALS: 1. Assuming physical access to the device extract as much information as practical 2. Leave as little traces/artifacts as practicalTuesday, 20 November 12 7
  • 8. iOS: Why Even Bother? • More than 5 years on the market • 360+ million iOS devices sold worldwide • 7 iPhones, 5 iPods, 5 iPads • “Smart devices” – they do carry a lot of sensitive data • Corporate deployments are increasing There was, is, and will be a real need for iOS forensicsTuesday, 20 November 12 8
  • 9. iOS Forensics 101 • Passcode • Prevents unauthorized access to the device • Bypassing passcode is usually enough • Keychain • System-wide storage for sensitive data • Encrypted • Disk encryptionTuesday, 20 November 12 9
  • 10. iOS Forensics 101 • Logical: iPhone Backup • “Ask” device to produce backup • Device must be unlocked (by passcode or iTunes) • Device may produce encrypted backup • Limited amount of informationTuesday, 20 November 12 10
  • 11. iOS Forensics 101 • Physical: filesystem acquisition • Boot-time exploit to run unsigned code • Device lock state isn’t relevant, can bruteforce passcode • Can get all information from the device • Physical+: flash memory acquisition • Same requirements as for physical • Also allows recovery of deleted files!Tuesday, 20 November 12 11
  • 12. iOS 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 are no (publicly) known ways to extract GID or UID key from the deviceTuesday, 20 November 12 12
  • 13. iOS Data Protection • 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 restoreTuesday, 20 November 12 13
  • 14. iOS 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 passcodeTuesday, 20 November 12 14
  • 15. iOS 4+ Passcode • Passcode-to-Key transformation is slow • Offline bruteforce 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 complexityTuesday, 20 November 12 15
  • 16. iOS 4+ PasscodeTuesday, 20 November 12 16
  • 17. iOS 5 Keychain • SQLite3 DB, all columns are encrypted • Available protection classes: • kSecAttrAccessibleWhenUnlocked (+ ...ThisDeviceOnly) • kSecAttrAccessibleAfterFirstUnlock (+ ...ThisDeviceOnly) • kSecAttrAccessibleAlways (+ ...ThisDeviceOnly) • Random key for each item, AES-GCM • Item key is protected with corresponding protection class master key 2 Class Wrapped Key Length Wrapped Key Encrypted Data (+Integrity Tag) 0 4 8 12Tuesday, 20 November 12 17
  • 18. iOS 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 attribute com.apple.system.cprotect • No protection class – partition key is used • Filesystem metadata and unprotected files • Transparent encryption and decryption (same as pre-iOS 4)Tuesday, 20 November 12 18
  • 19. iCloud • Introduced in Oct 2011 • Introduced with iOS 5 • Successor to MobileMe, .Mac, iTools • 5 GB free storage • Up to 50 GB paid storageTuesday, 20 November 12 19
  • 20. iCloud ServicesTuesday, 20 November 12 20
  • 21. iCloud BackupTuesday, 20 November 12 21
  • 22. iCloud 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 • RingtonesTuesday, 20 November 12 22
  • 23. iCloud 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 NowTuesday, 20 November 12 23
  • 24. iCloud Backup : How? • Can be enabled/disabled per device, at any time • iCloud Control Panel shows list of backed up devices and space/quota used (no access to data though)Tuesday, 20 November 12 24
  • 25. iCloud Backup : How? • Restore can only be done on clean device (i.e. new one or after a firmware restore) • No other ways to access/ browse/download backups in iCloud • Challenge accepted! :)Tuesday, 20 November 12 25
  • 26. Master Plan • Capture traffic while device restores from the iCloud • Deduce protocol from traffic dump(s) and some RE, if needed • Create a tool that will speak iCloud backup/restore protocol and pull data from the cloudTuesday, 20 November 12 26
  • 27. Capturing Traffic • iCloud backup/restore happens over SSL • Need to plant CA certificate to do MITM • Trivial for backup (just install “profile”) • Not-so-trivial for restore: clean device, no usual apps (Safari, Settings) and limited UI • Yet, there are ways to do this • Tethered jailbreak and add certificate to TrustStore.sqlite3 • iPhone Configuration Utility may also help • Kiosk-mode hack/bypass on iOS anyone? :)Tuesday, 20 November 12 27
  • 28. Traffic Flow • Authenticate: send Apple ID and password, receive authentication token • Get list of devices/backups • Get OTA backup keybag • Build list of files to download • iCloud backups are incremental and 3 most recent snapshots are maintained • Download file data (encrypted and chunked, from Amazon/Microsoft clouds!)Tuesday, 20 November 12 28
  • 29. Protocol • 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?)Tuesday, 20 November 12 29
  • 30. Protocol Flow /mbs/<personId> List of backups /mbs/<personId>/<backupUDID>/getKeys OTA backup keybag /mbs/<personId>/<backupUDID>/<snapshotId>/listFiles iCloud File manifest /mbs/<personId>/<backupUDID>/<snapshotId>/getFiles File auth tokens /mbs/<personId>/authorizeGet Info about containers of chunks for files (FileGroups) Request containers of chunks (FileGroups) Containers of chunksTuesday, 20 November 12 30
  • 31. Message Definitions message  FileGroups  {    repeated  FileChecksumStorageHostChunkLists  file_groups            =  1;    repeated  FileError                                                  file_error              =  2;    repeated  FileChunkError                                        file_chunk_error  =  3;    optional  uint32                                                        verbosity_level    =  4; } message  FileChecksumStorageHostChunkLists  {    repeated  StorageHostChunkList                storage_host_chunk_list            =  1;    repeated  FileChecksumChunkReferences  file_checksum_chunk_ref_list  =  2; } message  FileChecksumChunkReferences  {    required  bytes                    file_checksum        =  1;    repeated  ChunkReference  chunk_references  =  2; } message  ChunkReference  {    required  uint64  container_index  =  1;    required  uint64  chunk_index          =  2;   }Tuesday, 20 November 12 31
  • 32. Message Definitions message  FileChecksumStorageHostChunkLists  {    repeated  StorageHostChunkList                storage_host_chunk_list            =  1;    repeated  FileChecksumChunkReferences  file_checksum_chunk_ref_list  =  2; } message  StorageHostChunkList  {    required  HostInfo    host_info                                                          =  1;    repeated  ChunkInfo  chunk_info                                                        =  2;    required  string        storage_container_key                                  =  3;    required  string        storage_container_authorization_token  =  4; } message  HostInfo  {    required  string                hostname                                      =  1;    required  uint32                port                                              =  2;    required  string                method                                          =  3;    required  string                uri                                                =  4;    required  string                transport_protocol                  =  5;    required  string                transport_protocol_version  =  6;    required  string                scheme                                          =  7;    repeated  NameValuePair  headers                                        =  8; }Tuesday, 20 November 12 32
  • 33. Message Definitions message  FileChecksumStorageHostChunkLists  {    repeated  StorageHostChunkList                storage_host_chunk_list            =  1;    repeated  FileChecksumChunkReferences  file_checksum_chunk_ref_list  =  2; } message  StorageHostChunkList  {    required  HostInfo    host_info                                                          =  1;    repeated  ChunkInfo  chunk_info                                                        =  2;    required  string        storage_container_key                                  =  3;    required  string        storage_container_authorization_token  =  4; } message  ChunkInfo  {    required  bytes    chunk_checksum              =  1;    optional  bytes    chunk_encryption_key  =  2;    required  uint32  chunk_length                  =  3; }Tuesday, 20 November 12 33
  • 34. 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 • Probably files encrypted by Data Protection • Keychain items are encrypted using keys from OTA backup keybag • Need key 0x835 (securityd) to decrypt most keys from OTA backup keybagTuesday, 20 November 12 34
  • 35. Encryption Apple ID + Password or Key 0x835 AuthToken Files + – Files encrypted by + + Data Protection Keychain Records + +Tuesday, 20 November 12 35
  • 36. Key 0x835 • Device-specific key, computed from unique hardware-embedded key (UID) at startup • Apple can have a list of those keys • Apple claims not to store UID key but it’s not clear whether they store keys derived from it • Few things that are encrypted in iCloud backups are encrypted using key 0x835Tuesday, 20 November 12 36
  • 37. Summary • There is no user-configurable 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 (LE, USG, etc)Tuesday, 20 November 12 37
  • 38. Conclusions There is no privacy or confidentiality (not exactly news, go ask ex-CIA director if you don’t believe us)Tuesday, 20 November 12 38
  • 39. Thank You! Questions?Tuesday, 20 November 12 39
  • 40. Dark and Bright Sides of the iCloud (In)Security Andrey Belenko Dmitry Sklyarov Sr. Security Engineer Lead Analyst viaForensics Positive TechnologiesTuesday, 20 November 12 40

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