Analysis and Automated Discovery of Attacks in Transport Protocols

Transport protocols like TCP and QUIC are a crucial component of today’s Internet, underlying services as diverse as email, file transfer, web browsing, video conferencing, and instant messaging as well as infrastructure protocols like BGP and secure network protocols like TLS. Transport protocols provide a variety of important guarantees like reliability, in-order delivery, and congestion control to applications. As a result, the design and implementation of transport protocols is complex, with many components, special cases, interacting features, and efficiency considerations, leading to a high probability of bugs. Unfortunately, today the testing of transport protocols is mainly a manual, ad-hoc process. This lack of systematic testing has resulted in a steady stream of attacks compromising the availability, performance, or security of transport protocols, as seen in the literature. Given the importance of these protocols, we believe that there is a need for the development of automated systems to identify complex attacks in implementations of these protocols and for a better understanding of the types of attacks that will be faced by next generation transport protocols. In this dissertation, we focus on improving this situation, and the security of transport protocols, in three ways. First, we develop a system to automatically search for attacks that target the availability or performance of protocol connections on real transport protocol implementations. Second, we implement a model-based system to search for attacks against implementations of TCP congestion control. Finally, we examine QUIC, Google’s next generation encrypted transport protocol, and identify attacks on availability and performance

How Secure and Quick is QUIC? Provable Security and Performance Analyses

QUIC is a secure transport protocol developed by Google and implemented in Chrome in 2013, currently representing one of the most promising solutions to decreasing latency while intending to provide security properties similar with TLS. In this work we shed some light on QUIC\u27s strengths and weaknesses in terms of its provable security and performance guarantees in the presence of attackers. We first introduce a security model for analyzing performance-driven protocols like QUIC and prove that QUIC satisfies our definition under reasonable assumptions on the protocol\u27s building blocks. However, we find that QUIC does not satisfy the traditional notion of forward secrecy that is provided by some modes of TLS, e.g., TLS-DHE. Our analyses also reveal that with simple bit-flipping and replay attacks on some public parameters exchanged during the handshake, an adversary could easily prevent QUIC from achieving minimal latency advantages either by having it fall back to TCP or by causing the client and server to have an inconsistent view of their handshake leading to a failure to complete the connection. We have implemented these attacks and demonstrated that they are practical. Our results suggest that QUIC\u27s security weaknesses are introduced by the very mechanisms used to reduce latency, which highlights the seemingly inherent trade off between minimizing latency and providing `good\u27 security guarantees

Secure Communication Channel Establishment: TLS 1.3 (over TCP Fast Open) versus QUIC

Secure channel establishment protocols such as Transport Layer Security (TLS) are some of the most important cryptographic protocols, enabling the encryption of Internet traffic. Reducing latency (the number of interactions between parties before encrypted data can be transmitted) in such protocols has become an important design goal to improve user experience. The most important protocols addressing this goal are TLS 1.3, the latest TLS version standardized in 2018 to replace the widely deployed TLS 1.2, and Quick UDP Internet Connections (QUIC), a secure transport protocol from Google that is implemented in the Chrome browser. There have been a number of formal security analyses for TLS 1.3 and QUIC, but their security, when layered with their underlying transport protocols, cannot be easily compared. Our work is the first to thoroughly compare the security and availability properties of these protocols. Towards this goal, we develop novel security models that permit layered\u27\u27 security analysis. In addition to the standard goals of server authentication and data confidentiality and integrity, we consider the goals of IP spoofing prevention, key exchange packet integrity, secure channel header integrity, and reset authentication, which capture a range of practical threats not usually taken into account by existing security models that focus mainly on the cryptographic cores of the protocols. Equipped with our new models we provide a detailed comparison of three low-latency layered protocols: TLS 1.3 over TCP Fast Open (TFO), QUIC over UDP, and QUIC[TLS] (a new design for QUIC that uses TLS 1.3 key exchange) over UDP. In particular, we show that TFO\u27s cookie mechanism does provably achieve the security goal of IP spoofing prevention. Additionally, we find several new availability attacks that manipulate the early key exchange packets without being detected by the communicating parties. By including packet-level attacks in our analysis, our results shed light on how the reliability, flow control, and congestion control of the above layered protocols compare, in adversarial settings. We hope that our models will help protocol designers in their future protocol analyses and that our results will help practitioners better understand the advantages and limitations of secure channel establishment protocols

Secure Communication Channel Establishment: TLS 1.3 (over TCP Fast Open) versus QUIC

Secure channel establishment protocols such as Transport Layer Security (TLS) are some of the most important cryptographic protocols, enabling the encryption of Internet traffic. Reducing latency (the number of interactions between parties before encrypted data can be transmitted) in such protocols has become an important design goal to improve user experience. The most important protocols addressing this goal are TLS 1.3, the latest TLS version standardized in 2018 to replace the widely deployed TLS 1.2, and Quick UDP Internet Connections (QUIC), a secure transport protocol from Google that is implemented in the Chrome browser. There have been a number of formal security analyses for TLS 1.3 and QUIC, but their security, when layered with their underlying transport protocols, cannot be easily compared. Our work is the first to thoroughly compare the security and availability properties of these protocols. Toward this goal, we develop novel security models that permit “layered” security analysis. In addition to the standard goals of server authentication and data confidentiality and integrity, we consider the goals of IP spoofing prevention, key exchange packet integrity, secure channel header integrity, and reset authentication, which capture a range of practical threats not usually taken into account by existing security models that focus mainly on the cryptographic cores of the protocols. Equipped with our new models we provide a detailed comparison of three low-latency layered protocols: TLS 1.3 over TCP Fast Open (TFO), QUIC over UDP, and QUIC[TLS] (a new design for QUIC that uses TLS 1.3 key exchange) over UDP. In particular, we show that TFO’s cookie mechanism does provably achieve the security goal of IP spoofing prevention. Additionally, we find several new availability attacks that manipulate the early key exchange packets without being detected by the communicating parties. By including packet-level attacks in our analysis, our results shed light on how the reliability, flow control, and congestion control of the above layered protocols compare, in adversarial settings. We hope that our models will help protocol designers in their future protocol analyses and that our results will help practitioners better understand the advantages and limitations of secure channel establishment protocols

Leveraging Textual Specifications for Grammar-Based Fuzzing of Network Protocols

Grammar-based fuzzing is a technique used to find software vulnerabilities by injecting well-formed inputs generated following rules that encode application semantics. Most grammar-based fuzzers for network protocols rely on human experts to manually specify these rules. In this work we study automated learning of protocol rules from textual specifications (i.e. RFCs). We evaluate the automatically extracted protocol rules by applying them to a state-of-the-art fuzzer for transport protocols and show that it leads to a smaller number of test cases while finding the same attacks as the system that uses manually specified rules