Dropbox Forensics

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1 Cloud Storage Forensics Part I : Dropbox forensic.n0fate.com

2 Dropbox Forensics

3 Dropbox Forensics Dropbox 웹기반파일공유서비스 총 12 개의클라이언트지원 Desktop : Windows, Mac OS X, Linux Mobile : ios, Android, Symbian, Win Mobile, Blackberry 한계정당무료로 2GB 까지지원 자동동기화및사용자간자료공유

4 Dropbox Feature Previous Version 각파일에대한버전기록을유지함 변경한사용자, 호스트명, 시간, 용량정보

5 Dropbox Feature Recovery deleted files 삭제된데이터는최대 30 일 ( 팩랫 : 무제한 ) 보관

6 Dropbox Forensics Dropbox 의데이터는디스크에저장 디스크이미지에서각파일을접근할수있음 별다른문제없이분석을진행할수있음 삭제된파일은?.dropbox.cache 에삭제한파일을기록 Dropbox 페이지에버전정보기록

7 Show deleted files 삭제된파일은.dropbox.cache 에저장 동기화후이동 / 수정 / 삭제된파일저장 최대 3 일간데이터를유지 n0fate-macbook-air:~ n0fate$ cd Dropbox/.dropbox.cache/ n0fate-macbook-air:.dropbox.cache n0fate$ ls n0fate-macbook-air:.dropbox.cache n0fate$ cd n0fate-macbook-air: n0fate$ ls 2013 (deleted 60f35a91ffee07c883802a5920aa553f).pptx 2013 (deleted eafa23ac8430ffa0cfb77d847926c0bf).pptx 3E4E51888FB14B B07A3D035 (deleted 2bdac50f2409a961cbefaa83ada787c8).doentry 43B030297C994934B65199C78C8C8F75 (deleted b78f5a24a5cf8f2f18611a764f67b767).doentry n0fate-macbook-air: n0fate$ file * 2013 (deleted 60f35a91ffee07c883802a5920aa553f).pptx: Zip archive data, at least v2.0 to extract...<snip>... 43B030297C994934B65199C78C8C8F75 (deleted b78f5a24a5cf8f2f18611a764f67b767).doentry: XML document text

8 Dropbox Forensics 공격자가해당폴더 Wiping 수행한경우? 해당디렉터리의정보가 zero- out 되기때문에분석할수없음 다른요소를이용하여최대한분석필요 존재할수있는요소 계정정보 파일목록 ( 존재하는 / 삭제된파일 ) 파일동기화여부

9 filecache.dbx SQLite3 Database format file_journal table (<2013) Containing a lis_ng of all directories and files Synchroniza_on informa_on Only the live files, not deleted ones Recovery deleted record though SQLite3 Carving In early 2013 Dropbox released an update that encrypted this file

10 filecache.dbx SQLite3 DB Browser 로내용확인불가능 Hex Editor 에서정상적인파일로보이지않음 데이터암호화로인해올바른해석불가 Sqlite3 Database Encryp_on 기술을이용 User Password 기반의 Database Key 를생성하여모든데이터베이스암호화 역으로키를생성하여복호화를수행해야함.

$HKCU\SOFTWARE\Dropbox\ks Client$ version 1.

11 Database Key Genera_on User key genera_on (Windows) HMAC Key ( 고정값 ) Registry Path HKCU\SOFTWARE\Dropbox\ks Client version 1. HMAC Payload length payload valida_on HMAC 2. CryptUnprotectData API User Key

12 Database Key Genera_on User key genera_on (Linux) HMAC Key ( 고정값 ) File Path /home/<user>/.dropbox/hostkeys hostkeys version 1. HMAC payload Unique Key md5( ia9 <hostkeys FILEPATH>Xa ui20 ) 2. AES- 128 with CBC valida_on HMAC Ini_al Vector ( 고정값 ) User Key

13 Database Key Genera_on (Windows/Linux) Database Key genera_on Salt ( 고정값 ) Itera_on Count (1066) Itera_on Count User Key salt PBKDF2 passphrase DB Key (16bytes)

14 Decryp_ng SQLite DBX SQLite Encryp_on Extension (SEE) Read and write encrypted database files All data and the metadata is encrypted So outside observer the database appears to contain white noise Public version of SQLite will not be able to read or write an encrypted database file Link : hip://

15 Decryp_ng SQLite DBX Product Ac_va_on Key (7bb07b8d471d642e) DB Key (16bytes) RC4 AES OFB AES OFB AES CCM Encryp_on mode (default : AES128OFB)

16 Tools (Online) A Cri_cal Analysis of Dropbox Security 를발표한 newsom 멤버가개발 hips://github.com/newsom Tool Dropbox DB Key Generator : dbx- keygen- windows/linux (Mac OS X 는없음 ) DBX Decryptor : sqlite3- dbx

17 Tools (Online) 시연

18 Dropbox Decryptor (Offline)

19 Dropbox Decryptor When/Who : March, 1, 2013, Magnet Forensics Requirements filecache.dbx file [root]\documents and Seqngs\username\Applica_on Data\Dropbox on XP, or [root]\users\jad\appdata\roaming\dropbox on Vista The en_re protect folder for that user [root]\documents and Seqngs\username\Applica_on Data\Microsom on XP, or [root]\users\jad\appdata\roaming\microsom on Vista/7 A file containing the raw bytes from the Dropbox client value under the ks key in registry registry/ntuser.dat file (full path is HKEY_CURRENT_USER\Somware \Dropbox\ks User s windows login password

20 Dropbox Decryptor CryptProtectData hcp:// Password SID Master Key Storage Folder (Protected Folder) salt PBKDF2 login creden_al salt Encrypted Master Key Algorithm : AES- 256 HMAC : SHA512 Itera_on count : 5600 Master Key

21 Dropbox Decryptor

22 Q & A Homepage : forensic.n0fate.com E- Mail : n0fate@n0fate.com

23 Reference Florian LEDOUX,Nicolas RUFF. Applica_on Security Forum A Cri_cal Analysis Dropbox Security Dhiru Kholia, Przemyslaw Wegrzyn. Looking inside the (Drop) box

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