Team VerTeCs

Overall Objectives
Scientific Foundations
Application Domains
New Results
Contracts and Grants with Industry
Other Grants and Activities

Section: Other Grants and Activities

National Grants & Contracts

CNRS ACI Sécurité Potestat: Security Policies: Test Directed Analysis of Open Network Systems

Participants : Jérémy Dubreil, Thierry Jéron, Hervé Marchand, Vlad Rusu.

The Potestat project ( ) [2004-2007] involves Lsr-IMAG Grenoble, VERIMAG Grenoble and Lande and VerTeCs project teams in Irisa.

In the framework of open service implementations, based on the interconnection of heterogeneous systems, the security managers lack of well-formalized analysis techniques. The security of such systems is therefore organized from pragmatic elements, based on well-known vulnerabilities and their associated solutions. It then remains to verify if such security policies are correctly and effectively implemented in the actual system. This is usually carried out by auditing the administrative procedures and the system configuration. Tests are then performed, for instance by probing, to check the presence of some particular vulnerabilities. Although some tools are already available for specific tests (like password crackers), there is no solution to analyse the whole system conformance with respect to a security policy. This lack may be explained by several factors. First, there is currently no complete study about the formal modeling of a security policy, even if some particular aspects have been more thoroughly studied. Furthermore, verification based researches about security usually concern more precise elements, like cryptographic protocols or code analysis. Finally, most of these works are dedicated to an a priori verification of the coherency of security policies before their implementation. We are concerned here by the conformance of a system configuration with respect to a given policy. In the framework of the POTESTAT project we plan to tackle this problem according to the following items:

A long-term objective of this project is to offer some tools allowing security managers to model information flow, network elements (protocols, node types and their associated security policy, etc) to better describe the security policy for conformance testing and to provide some practical tools to perform coherency verification and vulnerabilities detection.

CNRS ACI Sécurité APRON: Analysis of Numerical Programs

Participant : Bertrand Jeannet.

The APRON (Analyse de PROgrammes Numériques) project ( ) [2004-2007] involves ENSMP, LIENS-ENS, LIX-Polytechnique, VERIMAG and VerTeCs -Irisa.

The goal is to develop methods and tools to analyse statically embedded software with high-level of criticity for which the detection of errors at run-time is unacceptable for safety or security reasons. Such safety and security software is found in the context of transportation, automotive, avionics, space, industrial process control and supervision, etc. One characteristics of such software is that it is based on physical models whence involve a lot of numerical computations. Moreover, counters play an important role in the control of reactive programs (e.g., delay counting in synchronous programming). Critical properties depending on these counters are generally outside the scope of model-checking approaches, while being simple enough to be accurately analysed by more sophisticated numerical analyses.

The goal of the project is the static analysis of large specifications (e.g. à la Lustre ) and corresponding programs (e.g. of 100 to 500 000 LOCs of C), made of thousands of procedures, involving a lot of numerical floating-point computations, as well as boolean and counter-based control in order to verify critical properties (including the detection of possible runtime errors), and to help in automatically locating the origin of critical property potential violation.

An example of such critical properties, as found in control/command programs, is of the form ``under a condition holding on boolean and numerical variables for some time, the program must imperatively establish a given boolean and/or numerical property, in a given bounded delay''.

VerTeCs contributes to the following topics within the APRON project:

VerTeCs focuses mainly on Lustre specifications and provides with the NBac tool one of the main experimental platforms of the project for the verification of critical properties on such specifications.

In 2006, most of the effort of VerTeCs was spent on the design and implementation of the common interface.

CNRS ACI Sécurité V3F: Validation and Verification of Programs with Floating Point Numbers

Participants : Bertrand Jeannet, Thierry Jéron.

V3F ( )[2003-2006] is a project involving LIFC Besançon, Inria-I3S Nice, LIST-CEA Saclay and project teams Lande and VerTeCs in Irisa. The goal of this project is to provide tools to support the verification and validation process of programs with floating-point numbers. More precisely, project V3F investigates techniques to check that a program satisfies the calculations hypothesis on the real numbers that have been done during the modeling step. The underlying technology will be based on constraint programming. Constraints solving techniques have been successfully used during the last years for automatic test data generation, model-checking and static analysis. However in all these applications, the domains of the constraints were restricted either to finite subsets of the integers, rational numbers or intervals of real numbers. Hence, the investigation of solving techniques for constraint systems over floating-point numbers is an essential issue for handling problems over the floats.

The results obtained in the course of the project V3F are a clean design of constraint solving techniques over floating-point number, and a study of the capabilities of these techniques in the software validation and verification process. An open and generic prototype of a constraint solver over the floats was developped. We also paid attention on the integration of floats into various formal notations (e.g., B, Lustre, UML/OCL) to allow an effective use of the constraint solver in formal model verification, automatic test data generation (functional and structural) and static analysis.

Our contribution to this project is to precisely formalize a conformance testing theory for programs with floating point with respect to their specifications, and second, to describe test generation algorithms in this framework. We consider the IOSTS model for the specification and the test purpose. An important point is to obtain a computable conformance relation. The solution that we propose takes into account the inaccuracy of floating points computations w.r.t. real semantics by allowing a limited skew of floating points values in conformant traces. In order to be able to recognize conformant traces/execution during test execution, and to check that the allowed skew does not diverge, we use a projection technique that allows the tester to use safely the values emitted by the implementation for its own execution. A nice point of our approach is that we can fully reuse the test generation and selection techniques implemented in our STG tool, the only change being in the implementation of the test driver. This result has been presented in the last meeting but has not yet been published.

This project ended this year with a final report presenting the main results of the project [28] and the organization by V3F project members of the workshop CSTVA'06 (Workshop on Constraints in Software Testing) in Nantes in September 2006, where the results of V3F were presented [16] .

RNRT POLITESS: Security Policies for Network Information Systems: Modeling, Deployment, Testing and Supervision

Participants : Jérémy Dubreil, Thierry Jéron, Hervé Marchand, Vlad Rusu.

The POLITESS project ( ) [2006-2008] involves GET (INT Evry and ENST Rennes), INPG-IMAG (LSR and VERIMAG laboratories), France Telecom R&D Caen, Leyrios Technologies, SAP Research, AQL Silicomp Rennes and Irisa. In a sense, this project is an extension of the Potestat project. The objective of the project is to study and provide methodological guidelines and software solutions for a formal approach to security of networks. This encompasses the specification of high level security policies with clear semantics, their deployment on the network in terms of security artifacts and the analysis of this deployment, testing and monitoring of security based on models of security policies and abstract models of networks. Our team is involved in several activities, in particular in modelling (defining adequate models for both the system and security policies), testing (modelling security testing, test generation/selection), supervision (intrusion detection, diagnosis) and case studies.


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