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Enhancing API-Level Access Control in Android Through Bytecode Rewriting Techniques

This paper presents a systematic study on the effectiveness of bytecode rewriting to enforce API-level access control in Android applications. The authors analyze the method invocation instructions in Android and demonstrate how static analysis can be utilized to identify sensitive API calls. By focusing on fine-grained access control, the study highlights various attack vectors against bytecode rewriting, provides insights into defending against them, and makes recommendations to strengthen application security. The findings contribute to the discourse on network and information security in mobile environments.

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Enhancing API-Level Access Control in Android Through Bytecode Rewriting Techniques

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  1. On the Effectiveness of API-Level Access Control Using Bytecode Rewriting in Android Presenter: Lu Gong

  2. Authors • Students: Hao Hao, Vicky Singh • Professor: Wenliang (Kevin) Du • Dept. of EE & CS, Syracuse University, New York

  3. The Conference • AsiaCCS: • ACM Symposium on Information, Computer and Communications Security • Rank C in the CCF recommendation list • Network and Information Security

  4. The paper • The first systematic study on the effectiveness of using bytecode rewriting for API-level access control • Cited by: • Structural detection of android malware using embedded call graphs (AISec ’13) • Compac: Enforce Component-Level Access Control in Android (ACM CodaSpy ’14)

  5. Background (1/3) • Bytecode rewriting • Use static analysis to identify sensitive API calls • Instrument bytecode to control access • Aim at implement fine-grained access control

  6. Background (2/3) • API-Level Access Control

  7. Background (3/3) • Method invocation instructions: • invoke-virtual: used to invoke a normal virtual method • invoke-direct: used to invoke either a private instance method or a constructor • invoke-static: used to invoke a static method • invoke-interface: used to invoke an interface method on an object whose concrete class is not known • invoke-super: used to invoke the closest superclass’ virtual method

  8. Scoping (1/5) • Two kinds of byte-code rewrite mechanisms: • Put the reference monitor in another service • Put the reference monitor within the application • Only focus on the second approach • Because the first one is fail-safe

  9. Scoping (2/5) • Assumption • The application either do not have native code or their native code is blocked from being executed • Reasons • Native code is running in the same process space as DVM • With native code, the app can easily tamper the DVM state, thus byte-code rewriting is useless

  10. Scoping (3/5) • Privileged resources • Hardware devices • Kernel data • Data from another process space • Ways to access them • System calls • Inter-process communication

  11. Scoping (4/5)

  12. Scoping (5/5) • Concealing API usage (the 4th attack) is possible • Java reflection • Dynamic binding

  13. Prelude (1/2) • Byte-code rewriting for a non-final class

  14. Prelude (2/2) • Byte-code rewriting for a final class

  15. Methodology • Study all possible attacks against bytecode rewriting • Give deeper insight into the attacks • Make recommendations on how to defend against these attacks

  16. Exploit JNI Naming Convention

  17. The JNI naming convention

  18. Dynamic binding

  19. The problem MyClass.my_Func() Java_MyClass_my_1Func MyClass.my.1Func()

  20. Case study

  21. Recommendations • If any names starts with numbers, bytecoderewriter should remove the digit as it is illegal.

  22. Exploit Java Class Reloading

  23. Example

  24. Case Study (1/2)

  25. Case Study (2/2)

  26. Recommendations • Stop application’s Java code from reloading preloaded Android core classes • BaseDexClassLoader.findClass() • DexFile.loadClass()

  27. Exploit Customized RPC stubs

  28. Case Study (1/2)

  29. Case Study (2/2)

  30. Recommendation • Apply API-level access control on android.os.ServiceManager.getService() • Alternative: rewrite android.os.Binder

  31. Conclusion • Although all problems are fixable, more static analysis and dynamic checking should be performed while byte-code rewriting

  32. Thank you

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