RustHorn: CHC-based Verification for Rust Programs (full version)

Reduction to the satisfiability problem for constrained Horn clauses (CHCs) is a widely studied approach to automated program verification. The current CHC-based methods for pointer-manipulating programs, however, are not very scalable. This paper proposes a novel translation of pointer-manipulating Rust programs into CHCs, which clears away pointers and memories by leveraging ownership. We formalize the translation for a simplified core of Rust and prove its correctness. We have implemented a prototype verifier for a subset of Rust and confirmed the effectiveness of our method.Comment: Full version of the same-titled paper in ESOP202

Hacspec: succinct, executable, verifiable specifications for high-assurance cryptography embedded in Rust

Despite significant progress in the formal verification of security-critical components like cryptographic libraries and protocols, the secure integration of these components into larger unverified applications remains an open challenge. The first problem is that any memory safety bug or side-channel leak in the unverified code can nullify the security guarantees of the verified code. A second issue is that application developers may misunderstand the specification and assumptions of the verified code and so use it incorrectly. In this paper, we propose a novel verification framework that seeks to close these gaps for applications written in Rust. At the heart of this framework is hacspec, a new language for writing succinct, executable, formal specifications for cryptographic components. Syntactically, hacspec is a purely functional subset of Rust that aims to be readable by developers, cryptographers, and verification experts. An application developer can use hacspec to specify and prototype cryptographic components in Rust, and then replace this specification with a verified implementation before deployment. We present the hacspec language, its formal semantics and type system, and describe a translation from hacspec to F. We evaluate the language and its toolchain on a library of popular cryptographic algorithms. An earlier attempt in this direction by some of the same authors, was also called hacspec, and sought to embed a cryptographic specification language into Python. We now believe that the strong typing of Rust provides an essential improvement to the specification and programming workflow. This work subsumes and obsoletes that earlier attempt. Hereafter, we use hacspec-python to refer to this prior version

Understanding and evolving the Rust programming language

Rust is a young systems programming language that aims to fill the gap between high-level languages—which provide strong static guarantees like memory and thread safety—and low-level languages—which give the programmer fine-grained control over data layout and memory management. This dissertation presents two projects establishing the first formal foundations for Rust, enabling us to better understand and evolve this important language: RustBelt and Stacked Borrows. RustBelt is a formal model of Rust’s type system, together with a soundness proof establishing memory and thread safety. The model is designed to verify the safety of a number of intricate APIs from the Rust standard library, despite the fact that the implementations of these APIs use unsafe language features. Stacked Borrows is a proposed extension of the Rust specification, which enables the compiler to use the strong aliasing information in Rust’s types to better analyze and optimize the code it is compiling. The adequacy of this specification is evaluated not only formally, but also by running real Rust code in an instrumented version of Rust’s Miri interpreter that implements the Stacked Borrows semantics. RustBelt is built on top of Iris, a language-agnostic framework, implemented in the Coq proof assistant, for building higher-order concurrent separation logics. This dissertation begins by giving an introduction to Iris, and explaining how Iris enables the derivation of complex high-level reasoning principles from a few simple ingredients. In RustBelt, this technique is exploited crucially to introduce the lifetime logic, which provides a novel separation-logic account of borrowing, a key distinguishing feature of the Rust type system.Rust ist eine junge systemnahe Programmiersprache, die es sich zum Ziel gesetzt hat, die Lücke zu schließen zwischen Sprachen mit hohem Abstraktionsniveau, die vor Speicher- und Nebenläufigkeitsfehlern schützen, und Sprachen mit niedrigem Abstraktionsniveau, welche dem Programmierer detaillierte Kontrolle über die Repräsentation von Daten und die Verwaltung des Speichers ermöglichen. Diese Dissertation stellt zwei Projekte vor, welche die ersten formalen Grundlagen für Rust zum Zwecke des besseren Verständnisses und der weiteren Entwicklung dieser wichtigen Sprache legen: RustBelt und Stacked Borrows. RustBelt ist ein formales Modell des Typsystems von Rust einschließlich eines Korrektheitsbeweises, welcher die Sicherheit von Speicherzugriffen und Nebenläufigkeit zeigt. Das Modell ist darauf ausgerichtet, einige komplexe Komponenten der Standardbibliothek von Rust zu verifizieren, obwohl die Implementierung dieser Komponenten unsichere Sprachkonstrukte verwendet. Stacked Borrows ist eine Erweiterung der Spezifikation von Rust, die es dem Compiler ermöglicht, den Quelltext mit Hilfe der im Typsystem kodierten Alias-Informationen besser zu analysieren und zu optimieren. Die Tauglichkeit dieser Spezifikation wird nicht nur formal belegt, sondern auch an echten Programmen getestet, und zwar mit Hilfe einer um Stacked Borrows erweiterten Version des Interpreters Miri. RustBelt basiert auf Iris, welches die Konstruktion von Separationslogiken für beliebige Programmiersprachen im Beweisassistenten Coq ermöglicht. Diese Dissertation beginnt mit einer Einführung in Iris und erklärt, wie komplexe Beweismethoden mit Hilfe weniger einfacher Bausteine hergeleitet werden können. In RustBelt wird diese Technik für die Umsetzung der „Lebenszeitlogik“ verwendet, einer Erweiterung der Separationslogik mit dem Konzept von „Leihgaben“ (borrows), welche eine wichtige Rolle im Typsystem von Rust spielen.This research was supported in part by a European Research Council (ERC) Consolidator Grant for the project "RustBelt", funded under the European Union’s Horizon 2020 Framework Programme (grant agreement no. 683289)