Yuwei Liu

Minghua Wang, Yuxi Ling, Mingzhi Gao et al.

Rust's ownership and type system provide strong memory safety guarantees, but unsafe code still presents memory safety risks. Formal verification is crucial for ensuring memory safety, but writing precise specifications for unsafe Rust is challenging and largely manual. Large language models (LLMs) have shown promise in generating formal specifications but are often code-centric, prone to inheriting implementation flaws, and lack systematic quality assessment. In this paper, we present KaPilot, a multi-agent framework for automatically generating specifications to verify unsafe Rust memory safety using Kani. The process begins with lightweight program analysis and proof harness generation. The SafetyReq agent extracts a concise, refined list of safety requirements from the target Rust function's documentation, which guides the SpecGenerate agent in producing initial specifications that specify memory safety concerns. Then, the specifications are iteratively refined through a generate-precheck-verify loop involving SpecGenerate, SpecPrecheck, and SpecVerify agents, which assess quality and feed errors back. By executing this loop multiple times, KaPilot generates a set of candidate specifications. Finally, the shuffle-and-implication strategy is applied to systematically determine the best specification from these candidates. We evaluated KaPilot on 54 unsafe Rust functions with ground truth and 70 without. KaPilot achieved 88.9% and 71.4% specification generation success, respectively, with 57.4% of generated specifications equivalent to or stronger than the ground truth. Compared with AutoSpec, KaPilot produces 14.8% more verifiable specifications and 25.9% more equivalent-or-better specifications.

Minghua Wang, Yuwei Liu, Lin Huang

Rust's ownership model and type system offer strong memory safety guarantees, but unsafe code and runtime panics still present significant risks. Formal verification is essential to ensure memory safety, but developing verification harnesses remains a challenging and manual task. Although large language models (LLMs) have shown strong performance in various code analysis tasks, directly applying them to harness generation often results in inaccurate API invocations, inefficient nondeterministic data generation, and fabricated fixes. In this paper, we present HarnessLLM, an automated workflow that leverages LLMs to generate verification harnesses for Rust code directly from existing test suites. HarnessLLM automatically extracts calling scenarios from test cases, generates nondeterministic arguments based on dependency analysis, and incrementally synthesizes harnesses. It then iteratively refines the harnesses, preserving critical code regions and reporting fabricated types or functions to LLMs for correction. In our evaluation on 9 real-world Rust codebases, HarnessLLM extracted 294 calling scenarios from 494 test cases with 94.66% precision and generated harnesses for all scenarios in an average of 145 seconds each. It outperformed the existing approach, Autoharness, which succeeded on only 41% of those scenarios. Finally, 6 real-world memory safety bugs were detected using the generated harnesses, demonstrating the practical utility of our approach in verification. To our knowledge, this is the first work to use LLMs for generating harnesses aimed at memory safety verification in real-world Rust projects.