Android Application Security at Devoxx 2013

Slides from the 'Android Application Security' session at Devoxx 2013

Transcript

1. @fmaelbrancke @tegbird Android Application Security Filip Maelbrancke Tegbir Dhillon
2. Application security ANDROID FOR DEVELOPERS
3. WE Filip Maelbrancke Consultant @ iDA MediaFoundry ! ! ! Tegbir Dhillon Team lead @ ING Bank Belgium
5. demo app http://git.io/devoxx-2013-android-app-sec CODE
6. Security The only system that is truly secure is one that is switched off and unplugged, locked in a titanium-lined safe, buried in a concrete bunker, and surrounded by nerve gas and very highly-paid armed guards. Even then, I wouldn't stake my life on it. “ ” Gene Spafford
7. Security = managing risk Cri$cality/Impact High  Risk Low  Risk Asset Medium  Risk Exploitability Low  Risk Vulnerability Medium  Risk M edium  Risk Probability Low  Risk   Threat
8. All in one device Increases threat proBability ! • GPS • Contacts • Camera • Email (work) • Wallet
9. Always out Vulnerability / Exploitability ! • Stolen • Forgotten • Lost • Weak pins • Use of open public WiFi
10. Everyone uses it
11. Everyone uses it
12. Android security application sandbox Each app runs with its own userID
13. traditional System resources File system Network System resource App 1 App 2 App ... UID = 1 2 3 4 5 starts permissions UID = 1 2 3 4 5
14. Android sandbox App1$$ Linux$UID:$ 12345$ Resources$ UID:12345$ DB$ Network$ File$ resources$ Permissions$$ UID:12345$ Sandbox$ App2$$ Linux$UID:$ 56789$ Resources$ UID:56789$ DB$ Network$ Files$ resources$ Permissions$ UID:56789$ $ Sandbox$ App1$$ App2$$
15. shared user id App1$$ App2$$ App1$$ Linux$UID:$ 10160$ Resources$ UID:10160$ DB$ Network$ File$ Resources$ DB$ Network$ File$ resources$ Permissions$$ UID:10160$ App1$$ Linux$UID:$ 10160$ Sandbox$ <manifest ... android:sharedUserId=“com.example.apps” ...>
16. Permission types Permission) Permission)Level) Normal) Permission)Level) dangerous) Permission)Level) Signature) Permission)Level) SignatureOrSystem)
17. Signing tips Secure your private key Strong passwords Four eyes principle Keep key-store in safe place Provide geographic redundancy
18. typical mobile app MOBILE APPLICATION UI LOCAL STORAGE REMOTING LAYER REMOTE API COMMUNICATION CHANNEL
19. Security APP HARDENING DATA NETWORK SERVICES
21. Securing the app JAVA CLASS DEX
22. Obfuscation
23. Proguard obfuscate optimize Shrink
24. proguard obfuscation
25. proguard configuration
26. proguard Beware!
27. proguard loggingwrapper
28. proguard configuration
29. proguard BEtter
30. reverse engineer
31. reverse engineer TOOLS ! • Apktool • Dex2jar • Apk to Java !
32. reverse engineer code
33. other techniques If possible, run code at server! server String encryption Hide sensitive strings eg “Secure” Native code Java Native Interface reflection Proxy Introduces indirection Class encryption Use DexGuard
34. dexguard Same config proguard++ Commercial Good value for the money Tamper checks
35. proguard tips Test! release build Mapping.txt Save! Crash? Supported on Crashlytics, Crittercism, ...
36. TAMPER DETECTION
37. Environment 1.installer 2.debugger / emulator 3.BINARY Validation Tamper detection / protection
38. INSTALLER PLAY STORE INSTALLER
39. debugger Debugger check
40. debugger Debugger check
41. emulator EMULATOR check
42. SIGNING KEY Valid signing key ! • SHA1 of signing cert • Embed • Check with runtime signature !
43. SIGNING KEY Valid signing key
44. rooted device root detection ! • Check typical apps / files • Check keys • … !
46. local Data protection Avoid it if you can Avoid External storage Avoid external storage for sensitive information For critical info set android:saveEnabled="false" Backup set android:allowBackup=false proper permissions MODE_PRIVATE with files
47. local Data protection getWindow().setFlags(LayoutParams.FLAG_SECURE, LayoutParams.FLAG_SECURE); avoid screen shots LOGOUT on inactivity if usability allows and clear the cached information
48. keylogger
49. encryption
50. bouncy castle Android = subset of upstream release cut-down CONSISTENT Consistent crypto across Android versions MINIMAL change github.com/rtyley/spongycastle Spongy castle Repackage of Bouncy Castle for Android
51. encryption libs SQLCipher sqlcipher.net ! • Modified version of SQLite • AES-256 encryption • Drop-in replacement ! iocipher guardianproject.info/code/iocipher ! Virtual encrypted disk
52. key management Store along with the data (file private to the app) Store Embed Embed in source code (obfuscated ?) EASY TO EXTRACT
53. key management don’t store Don’t store the key on the device Have it entered each time necessary Store In systems service SOLUTIONS
54. key derivation Long random strings of bits encryption keys people vs keys Users are familiar with passwords Crypto algo PBKDF2WithHmacSHA1 password based encryption Generate strong crypto keys based on humanly-manageable passwords
55. proper key derivation Using a salt protects from table- assisted / pre-computed dictionary attacks SALT key stretching Repeat the key derivation operation multiple times to produce the final key Slows down brute force attacks https://github.com/nelenkov/android-pbe http://nelenkov.blogspot.jp/2012/04/using-password-based-encryption-on.html Nikolay Elenkov
56. KEYCHain? Keystore provider ! • Since Android 4.3 • Can be hardware-backed https://github.com/nelenkov/android-keystore Nikolay Elenkov
57. network
58. Secure communication channel use https Use SSL / TLS ! • Confidentiality • Authentication ! VALIDATION Hostname verification ! Certificate pinning
59. secure communication channel hostname verification
60. Trustmanager StrongTrustManager ! • Validate whole certificate chain • Debian certificate store !
61. self-signed cert
62. self-signed cert don’t trust all!
63. certificate pinning echo | openssl s_client -connect host:443 2>&1 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > mycertificate.pem get certificate (openssl) embed in application /res/raw Custom trustmanager Based on keystore Load into keystore SSL context Init SSL context with TrustManager https://developer.android.com/training/articles/security-ssl.html
65. Securing services Controls ! • Kill switch for specific functionality • Server downtime communication • Mandatory update mechanism !
66. securing services Backend REST and APIs can have similar vulnerabilities to web applications mitigate follow OWASP top 10
67. Effective security Using CryptoLint, we performed a study on cryptographic implementations in 11,748 Android applications. Overall we find that 10,327 programs – 88% in total – use cryptography inappropriately. The raw scale of misuse indicates a widespread misunderstanding of how to properly use cryptography in Android development. “ ”
68. effective security hardcoded passphrases manually seeded SecureRandom insufficient key generation iterations hardcoded salts non-random initialization vectors
69. security testing Static analysis Manual code review design review Analysis Static Dynamic Penetration testing
70. HOW TO CONTACT TWITTER: @fmaelbrancke EMAIL: filip@maelbrancke.net THANK YOU TWITTER: @tegbird EMAIL: tegbird@gmail.com