Towards an Automatic Analysis of Web Service Security

Abstract

The original publication is available at www.springerlink.comInternational audienceWeb services send and receive messages in XML syntax with some parts hashed, encrypted or signed, according to the WS-Security standard. We have introduced a model to formally describe the protocols that underly these services, their security properties and the rewriting attacks they might be subject to. Unlike other protocol models (in symbolic analysis) ours can handle non-deterministic receive/send actions and unordered sequence of XML nodes. Then to detect the attacks we have to consider the services as combining multiset operators and cryptographic ones and we have to solve specific satisfiability problems in the combined theory. By an extension of the combination techniques we obtain a decision procedure for insecurity of Web services with messages built using encryption, signature, and other cryptographic primitives. This combination technique allows one to decide insecurity in a modular way by reducing the associated constraint solving problems to problems in simpler theories.Nous introduisons un modèle abstrait des services web qui permet d'exprimer les attaques par réécriture. Nous proposons un algorithme pour détecter ce type de vulnérabilité

Key Substitution in the Symbolic Analysis of Cryptographic Protocols

“…Although this general class encompasses all intruder deduction systems and constraint systems given in this paper, we have preferred to give the simpler definitions from [17] which are sufficient for stating our problem. We will refer, without further justifications, to the model of [15] as extended intruder systems and extended constraint systems. The latter correspond to symbolic derivations in which a most general unifier of the unification system has been applied on the input/output messages.…”

Automatic Composition of Services with Security Policies

“…In the following definition, we employ these simplifying hypotheses to introduce symbolic derivations, a recent model for secured Web services that we have proposed in [7]. We give here a definition parameterized by a deduction system D on a signature F. This deduction system defines computation rules that express how a new term can be constructed from an existing set of terms.…”

“…In their full generality, messages exchanged between Web services are XML documents adhering to a specified schema. These schemas permit one to define open-ended structures such as lists which are beyond the scope of existing tools, though decision procedures could in principle be implemented to take into account schemas or the XML format [7]. In this paper, we consider messages defined by terms over the signature:…”

“…An additional advantage is that it is possible to analyse the security of the composed service employing the very same tools. While all these results are valid in the Dolev-Yao abstract model of messages with cryptography, the tools can be extended to XML messages to take into account rewriting attacks [7].…”

“…In this paper we address the latter problem: assuming that semantically equivalent constructions are represented by identical symbols, we adapt the structures of the messages exchanged between Web services. This approach is based on Deduction systems (expressing the possible computations on messages) and symbolic derivations (sequences of deductions and communications states) defined in [7].…”