The services offered to the Internet community have been constantly increasing the last few years. This is mainly due to the fact that mobile code has matured enough in order to provide the Internet users with high quality applications that can be executed remotely. When a user downloads and executes code from various Internet sources, security issues arise. In this paper, we are addressing the latter and we present a comparative evaluation of the methods used by Java, Safe-Tcl and ActiveX in order to confront with these issues, based on current security functions and implementations as well as on future adjustments and extensions.

1. Addressing Security Issues in
Programming Languages for
Mobile Code
S. Gritzalis, J. Iliadis
• Department of Information and Communication Systems,
University of the Aegean
DEXA’98
• Department of Informatics,
Technological Educational Institute of Athens

2. Introduction
• Mobile Code
– travels on heterogeneous networks
– crosses security domains
– is executed upon arrival to the destination
– security concerns

3. Mobile Code Languages
• Java
general-purpose, object oriented language. Portable in compiled
binary code
• Safe-Tcl
high-level interpreted scripting language
• ActiveX
visual control framework, using COM as the underlying
infrastructure. O/S dependent

4. Security Issues
Hostile Applets
– attack the Integrity of a system
– violate the user’s Privacy
– limit the Availability of a system
– achieve user’s Annoyance

5. Java Security
• Sandbox
• Classloader
• Bytecode Verifier
• Security Manager
• JDK 1.2 new security modus operandi
• security policy
• access control
• protection domains

6. Java Security - Extensions
• Digital Signatures
• Policy Enforcement
– capabilities
– extended stack
introspection
– namespace
management
• Policy Definition
• Secure Code
Distribution
• Corporate-wide
policy
• Confining the use of
Java in a network
domain

7. Safe-Tcl Security
• Padded cell approach / Dual-Interpreter
– Trusted Interpreter -> Full Tcl
– Untrusted/Restricted Interpreter -> Safe-Tcl
• Command Aliases
• Security Policy

8. Safe-Tcl Security Extensions
• Authentication of Tclets
• Authentication of Safe-Tcl security
policies
• Confronting with denial-of-service attacks

9. ActiveX Security
• Applet authentication
• code safe for initialising
• code safe for scripting
• lack of configurable security policy
• ActiveX, Digital Signatures and Firewalls

10. ActiveX Security - Extensions
• Execution safety
• Software memory protection
– attach proofs of memory protection to code

11. Conclusions
• Security Scheme
• Detailed Security Policy
• Security Integration