1. Basic Security: Java vs.NET Master Seminar Advanced Software Engineering Topics Prof. Jacques Pasquier-Rocha Software Engineering Group Department of Informatics University of Fribourg, Switzerland Author: David Buchmann Supervisor: Ghita Kouadri Mostéfaoui 15. Mai 2003

2. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

3. Introduction ● Use downloaded code (web browser, distributed application) ● Need for strict control ● Sandbox ● Permission Management ● Codebases resp. Trust zones

4. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

5. Principles ● Compiler produces Byte Code ● Virtual Machine to interpret code ● Class Loader ● Code Verifier ● Access Control ● Interface for native code

6. Distribution ● Packages / Namespaces to avoid naming conflicts ● Reflection to analyse code ● Code and resource libraries (JAR resp. Assembly)

7. Remote Calls ● RMI resp..NET Remoting ● Use remote objects, marshalling of parameter objects ● Typical case of executing foreign code ● See presentation of Robert Feldmann

8. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

9. What kind of security?

10. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

11. Access to private data ● Public, protected, private, final ● Pointer, arrays ● Casts, stack corruption ● Uninitialized variables ● Byte code verifier

12. Sandbox and native code ●.NET application domain, fixed at startup ● Java protection domain, dynamic ● Old native code can be used, but not controlled by the VM ● Managed vs. unmanaged code

13. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

14. Permissions ● Allow operations depending on protection domain ● Build groups of domains – Directory – URL – Signature – All Code

15. .NET Code Groups

16. Determining the group in Java ● Dynamically determine group ● Based on the protection domain of classes on the execution stack

18. Managing groups and permissions ● Java: Policy file – Java -Djava.security.policy= ●.NET caspol.exe front end – caspol.exe -addgroup 1.3 -site www.unifr.ch FullTrust – caspol.exe -security off – caspol.exe -addpset MyCustomSet permissions.xml <PermissionSet class=“System.Security.NamedPermissionSet“ version=“1“ Name=“MyCustomSet“ Description=“An example set“> <IPermission class=“System.Security.Permissions. EnvironmentPermission, mscorlib, Version=1.0.3300.0, Culture=neutral, PublicKeyToken=b77a5c51934e089“ version=“1“ Unrestricted=“true“ />

19. Policy levels & flexibility ●.NET: machine, user, enterprise level – intersection of permissions ● Java: default policy, user - union of permissions ● Java can replace security manager, permission manager and class loader

20. Overview ● Part 1: Theory – Introduction – Principles of Java and.NET – What kind of security? – Language security – Permission Management ● Part 2: Example with Java

21. Downloaded code ● Downloaded code is in separate protection domain

22. No access to file system ● Downloaded code should not have access to the file system

23. Network access ● Downloaded code should only connect to the server it comes from

24. The calling stack ● Local code called by remote code is not trusted, but treated as if it was remote.

25. Conclusion ● Private and final not only for clean programming, but important for security ● Virtual machines to enforce proper code and access control ● Java and.NET very similar – Java more flexible –.NET better default framework – but no replace

26. Java vs.NET ● Long used, security holes found ● Implement own security features ● Run on different platforms ● Integrate with different systems ● Many open source projects ● Integrated with windows infrastructure ● Good security implementation ● Use different languages ● Very professional Visual Studio.NET ● Will become important because of Microsofts marketing power

27. Thank You Questions ?