The Android security jungle: pitfalls, threats and survival tips Scott Alexander-Bown @scottyab
The Jungle • Ecosystem • Google’s protection • Threats • Risks
Survival • Network • Data protection (encryption) • App/device integrity • App binary security • Testing
Scott Alexander-Bown • Lead Android Dev (remote) at Intohand • Co-Author - Android Security Cookbook • Co-Founder of SWmobile
1.4 Billion users
OpenSignals.com
Security Services • Google Play Approval process (human approval since 2015) • Developer security notifications • Android Bouncer • • Android device manager (Device security) • Safety net (intrusion detection) • Android at Work
Slide Adrian Ludwig’s - Android Security State of the Union
Newer version of Android are more secure 1.5 stack buffer, integer overflow protection 2.3+ null pointer dereference mitigation, NX 4.0+ ASLR 4.1+ ASLR strengthened 4.3 Security-Enhanced Linux 5.0 Security-Enhanced Linux - enforcing Updatabled Webview (via playstore)
Threats
Threats: App Hijacking • Taking an app and adding malware • Concerns • Reversing Android apps is easy • No need for certificate authority • Sideload
“I ain’t got time to (heart)bleed”
OWASP • Mobile Security Project • iOS and Android • Top 10 risks • attack vectors • threat agents • impacts
OWASP top 10 risks • M1: Weak Server Side • M6: Broken Cryptography Controls • M7: Client Side Injection • M2: Insecure Data Storage • M8: Security Decisions Via • M3: Insufficient Transport Untrusted Inputs Layer Protection • M9: Improper Session Handling • M4: Unintended Data Leakage • M10: Lack of Binary Protections • M5: Poor Authorization and Authentication
Survival kit
Survival tips 1. Harden the network communications 2. Protect stored data (encryption) 3. Validate the device and app integrity 4. Increase binary security
Network communications • Use SSL / TLS! • Use the platform SSL/TLS validation (i.e don’t disable it!) • Use only strong cipher suites (128bit+) and TLS versions (TLS v1.2) • OkHttp 2.1 - https://publicobject.com/2014/11/12/okhttp-2-1/
Looks like you’re not using SSL pinning? • Devices ship with 100+ Certificate Authorities (CA) and users can install their own • Pinning limits the trusted root CA’s • Two types • Certificate pinning • Public Key pinning
Public key pinning
Patch against SSL exploits • Google Play Services provides a dynamic security provider • ProviderInstaller.installIfNeeded(getContext()); • https://developer.android.com/training/articles/security-gms- provider.html#patching
Tips
Code in a slide :’( Password based encryption
Encryption libraries • Conceal • https://facebook.github.io/conceal • SQL cipher https://www.zetetic.net/sqlcipher/sqlcipher-for-android/ • Secure-Preferences (or Hawk) • https://github.com/scottyab/secure-preferences
Hardcoded encryption key
Verifying App integrity • Debuggable check • Apk Checksum • Signing certificate verification
Signing Certificate Verification Build-time Runtime 3. Get the Signature from the 1. Get you certificate signature PackageManager $keytool -list -v -keystore your_app.keystore 4. Hash the Signature 2. Embed in app 5. Compare the signature hashes strings String CERTIFICATE_SHA1 = “71920AC9486E087DCBCF5C7F6F…”;
Verifying device integrity • Emulator check • https://github.com/strazzere/a nti-emulator • Google SafteyNet test • https://github.com/scottyab/sa fetynethelper
root@android:/ # • Root apps / Dangerous apps • Suspect system properties • SU/BusyBox binaries • RW /system • https://github.com/scottyab/rootbeer
Obfuscation
ProGuard • Java code obfuscator • Part of the Android SDK • Free as in Beer! • ReTrace - Supported by Error handling services such as Crashlytics
DexGuard • Commercial version of ProGuard • Designed for Android and protection • Useful security utils - SSL Pinning, Root check, logging removal etc • My favourite features • String Encryption • API hiding
Quick Android Review Kit (Quak) • Python script • Works with .apk or source code • Automated tests • weaknesses • exploits • Creates exploit .apks • https://github.com/linkedin/qark
Click here for more! • 42+ Secure mobile development tips http://bit.ly/viafor42 • OWASP Mobile security risks http://bit.ly/owaspmobile • Android security cookbook [book] http://bit.ly/MscEFu • Android security internals [book] http://bit.ly/andsecint • Droidsec (whitepapers) droidsec.org/wiki
Thanks • @gotocph • @intohand • 20th Century Fox • Android security team
Questions? dev@scottyab.com @scottyab github.com/scottyab Please Remember to rate this session Thank you
WebView • Before • getSettings().setJavaScriptEnabled(false) • getSettings().setAllowFileAccess(false) • During • WebViewClient.shouldOverrideUrlLoading() • enforce local content or Https • Whitelisted hosts/urls • .shouldInterceptRequest() to intercept XmlHttpRequests • After • webview.clearCache(true)
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