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Security in IT systems, particularly in embedded devices like Cyber Physical Systems (CPSs), has become an important matter of concern as it is the prerequisite for ensuring privacy and safety. Among a multitude of existing security measures, the Transport Layer Security (TLS) protocol family offers mature and standardized means for establishing secure communication channels over insecure transport media. In the context of classical IT infrastructure, its security with regard to protocol and implementation attacks has been subject to extensive research. As TLS protocols find their way into embedded environments, we consider the security and robustness of implementations of these protocols specifically in the light of the peculiarities of embedded systems. We present an approach for systematically checking the security and robustness of such implementations using fuzzing techniques and differential testing. In spite of its origin in testing TLS implementations we expect our approach to likewise be applicable to implementations of other cryptographic protocols with moderate efforts.
Digital networked communications are the key to all Internet-of-Things applications, especially to smart metering systems and the smart grid. In order to ensure a safe operation of systems and the privacy of users, the transport layer security (TLS) protocol, a mature and well standardized solution for secure communications, may be used. We implemented the TLS protocol in its latest version in a way suitable for embedded and resource-constrained systems. This paper outlines the challenges and opportunities of deploying TLS in smart metering and smart grid applications and presents performance results of our TLS implementation. Our analysis shows that given an appropriate implementation and configuration, deploying TLS in constrained smart metering systems is possible with acceptable overhead.
Die Vielfalt der Protokolle, die praktisch auf allen Ebenen der Netzwerkkommunikation zu berücksichtigen ist, stellt eine der großen Herausforderungen bei der fortschreitenden Automatisierung des intelligenten Hauses dar. Unter dem Überbegriff Internet der Dinge (Internet of Things) entstehen gegenwärtig zahlreiche neue Entwicklungen, Standards, Allianzen und so genannte Ökosysteme. Diese haben die Absicht einer horizontalen Integration gewerkeübergreifender Anwendungen und verfolgen fast alle das Ziel, die Situation zu vereinfachen, die Entwicklungen zu beschleunigen und Markterfolge zu erreichen. Leider macht diese Vielfalt momentan die Welt aber eher noch komplexer und bringt damit das Risiko mit sich, genau das Gegenteil der ursprünglichen Absichten zu erreichen. Dieser Beitrag versucht, die Entwicklungen möglichst systematisch zu kategorisieren und mögliche Lösungsansätze zu beschreiben.
eTPL: An Enhanced Version of the TLS Presentation Language Suitable for Automated Parser Generation
(2017)
The specification of the Transport Layer Security (TLS) protocol defines its own presentation language used for the purpose of semi-formally describing the structure and on-the-wire format of TLS protocol messages. This TLS Presentation Language (TPL) is more expressive and concise than natural language or tabular descriptions, but as a result of its limited objective has a number of deficiencies. We present eTPL, an enhanced version of TPL that improves its expressiveness, flexibility, and applicability to non-TLS scenarios. We first define a generic model that describes the parsing of binary data. Based on this, we propose language constructs for TPL that capture important information which would otherwise have to be picked manually from informal protocol descriptions. Finally, we briefly introduce our software tool etpl-tool which reads eTPL definitions and automatically generates corresponding message parsers in C++. We see our work as a contribution supporting sniffing, debugging, and rapid-prototyping of wired and wireless communication systems.
Exploiting Dissent: Towards Fuzzing-based Differential Black Box Testing of TLS Implementations
(2017)
The Transport Layer Security (TLS) protocol is one of the most widely used security protocols on the internet. Yet do implementations of TLS keep on suffering from bugs and security vulnerabilities. In large part is this due to the protocol's complexity which makes implementing and testing TLS notoriously difficult. In this paper, we present our work on using differential testing as effective means to detect issues in black-box implementations of the TLS handshake protocol. We introduce a novel fuzzing algorithm for generating large and diverse corpuses of mostly-valid TLS handshake messages. Stimulating TLS servers when expecting a ClientHello message, we find messages generated with our algorithm to induce more response discrepancies and to achieve a higher code coverage than those generated with American Fuzzy Lop, TLS-Attacker, or NEZHA. In particular, we apply our approach to OpenssL, BoringSSL, WolfSSL, mbedTLS, and MatrixSSL, and find several real implementation bugs; among them a serious vulnerability in MatrixSSL 3.8.4. Besides do our findings point to imprecision in the TLS specification. We see our approach as present in this paper as the first step towards fully interactive differential testing of black-box TLS protocol implementations. Our software tools are publicly available as open source projects.
Real-Time Ethernet has become the major communication technology for modern automation and industrial control systems. On the one hand, this trend increases the need for an automation-friendly security solution, as such networks can no longer be considered sufficiently isolated. On the other hand, it shows that, despite diverging requirements, the domain of Operational Technology (OT) can derive advantage from high-volume technology of the Information Technology (IT) domain. Based on these two sides of the same coin, we study the challenges and prospects of approaches to communication security in real-time Ethernet automation systems. In order to capitalize the expertise aggregated in decades of research and development, we put a special focus on the reuse of well-established security technology from the IT domain. We argue that enhancing such technology to become automation-friendly is likely to result in more robust and secure designs than greenfield designs. Because of its widespread deployment and the (to this date) nonexistence of a consistent security architecture, we use PROFINET as a showcase of our considerations. Security requirements for this technology are defined and different well-known solutions are examined according their suitability for PROFINET. Based on these findings, we elaborate the necessary adaptions for the deployment on PROFINET.