8,002 research outputs found
Formal Verification of Security Protocol Implementations: A Survey
Automated formal verification of security protocols has been mostly focused on analyzing high-level abstract models which, however, are significantly different from real protocol implementations written in programming languages. Recently, some researchers have started investigating techniques that bring automated formal proofs closer to real implementations. This paper surveys these attempts, focusing on approaches that target the application code that implements protocol logic, rather than the libraries that implement cryptography. According to these approaches, libraries are assumed to correctly implement some models. The aim is to derive formal proofs that, under this assumption, give assurance about the application code that implements the protocol logic. The two main approaches of model extraction and code generation are presented, along with the main techniques adopted for each approac
Crypto-Verifying Protocol Implementations in ML
We intend to narrow the gap between concrete
implementations and verified models of cryptographic protocols.
We consider protocols implemented in F#, a variant of ML, and
verified using CryptoVerif, Blanchet's protocol verifier for
computational cryptography.
We experiment with compilers from F# code to CryptoVerif processes,
and from CryptoVerif declarations to F# code.
We present two case studies: an implementation of the Otway-Rees
protocol, and an implementation of a simplified password-based
authentication protocol. In both cases, we obtain concrete security
guarantees for a computational model closely related to
executable code
Safe abstractions of data encodings in formal security protocol models
When using formal methods, security protocols are usually modeled at a high level of abstraction. In particular, data encoding and decoding transformations are often abstracted away. However, if no assumptions at all are made on the behavior of such transformations, they could trivially lead to security faults, for example leaking secrets or breaking freshness by collapsing nonces into constants. In order to address this issue, this paper formally states sufficient conditions, checkable on sequential code, such that if an abstract protocol model is secure under a Dolev-Yao adversary, then a refined model, which takes into account a wide class of possible implementations of the encoding/decoding operations, is implied to be secure too under the same adversary model. The paper also indicates possible exploitations of this result in the context of methods based on formal model extraction from implementation code and of methods based on automated code generation from formally verified model
Do not trust me: Using malicious IdPs for analyzing and attacking Single Sign-On
Single Sign-On (SSO) systems simplify login procedures by using an an
Identity Provider (IdP) to issue authentication tokens which can be consumed by
Service Providers (SPs). Traditionally, IdPs are modeled as trusted third
parties. This is reasonable for SSO systems like Kerberos, MS Passport and
SAML, where each SP explicitely specifies which IdP he trusts. However, in open
systems like OpenID and OpenID Connect, each user may set up his own IdP, and a
discovery phase is added to the protocol flow. Thus it is easy for an attacker
to set up its own IdP. In this paper we use a novel approach for analyzing SSO
authentication schemes by introducing a malicious IdP. With this approach we
evaluate one of the most popular and widely deployed SSO protocols - OpenID. We
found four novel attack classes on OpenID, which were not covered by previous
research, and show their applicability to real-life implementations. As a
result, we were able to compromise 11 out of 16 existing OpenID implementations
like Sourceforge, Drupal and ownCloud. We automated discovery of these attacks
in a open source tool OpenID Attacker, which additionally allows fine-granular
testing of all parameters in OpenID implementations. Our research helps to
better understand the message flow in the OpenID protocol, trust assumptions in
the different components of the system, and implementation issues in OpenID
components. It is applicable to other SSO systems like OpenID Connect and SAML.
All OpenID implementations have been informed about their vulnerabilities and
we supported them in fixing the issues
Formally based semi-automatic implementation of an open security protocol
International audienceThis paper presents an experiment in which an implementation of the client side of the SSH Transport Layer Protocol (SSH-TLP) was semi-automatically derived according to a model-driven development paradigm that leverages formal methods in order to obtain high correctness assurance. The approach used in the experiment starts with the formalization of the protocol at an abstract level. This model is then formally proved to fulfill the desired secrecy and authentication properties by using the ProVerif prover. Finally, a sound Java implementation is semi-automatically derived from the verified model using an enhanced version of the Spi2Java framework. The resulting implementation correctly interoperates with third party servers, and its execution time is comparable with that of other manually developed Java SSH-TLP client implementations. This case study demonstrates that the adopted model-driven approach is viable even for a real security protocol, despite the complexity of the models needed in order to achieve an interoperable implementation
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