一个出具证明编译器后端的设计与实现

设计并实现一个类C语言PointerC的出具证明编译器后端。该后端采用最强后条件演算同步处理整型断言和指针断言实现整型验证条件和指针验证条件的证明,能够完全自动地产生目标级程序的指针安全性证明,处理常见递归数据结构中的非一致性别名问题。后端包括独立的定理检查器,能够检验携证明代码的完整性。     

出具证明编译器中线性整数命题证明的自动生成

近年来,出具证明编译器作为构建高可信软件的重要途径,逐渐成为编译器理论和形式化验证的研究热点.在其理论框架中,编译器需要借助自动定理证明技术,自动地证明验证条件并生成机器可检查的证明项,因此好的自动定理证明器对出具证明编译器至关重要.本文基于Simplex算法在出具证明编译器的框架内设计并实现了一个支持线性整数命题求解的自动定理证明器,并且提出一套证明项构造方法,将其应用于自动定理证明器中可生成Coq可检查的证明.     

一个出具证明编译器原型系统的实现

出具证明编译器是随着人们对现今的软件提出更高的可靠性和安全性要求而产生的工具,它结合了以往程序设计和程序安全性证明的技术。论文介绍了一个出具证明编译器原型系统的实现。     

出具证明编译器中代码优化与程序规范转换

出具证明编译器在软件安全研究得到越来越多的关注,是程序验证研究的一个重要方向.但目前关于出具证明编译器的研究主要是在程序逻辑设计和定理自动化证明方面,很少关注编译优化对规范的影响.而编译优化是决定出具证明编译器是否能走向应用的关键因素之一.通过研究数据流优化的基本行为,提出利用数据流分析结果来变换规范的方法,以使原规范的约束准确而充分地施加于优化后的代码,并实现了一个包含多种优化和相应规范转换的编译器原型系统,展示了方法的可行性.     

一种构造代码安全性证明的方法

提出一种构造代码安全性证明的新方法.这种方法的基本思想是,在基础逻辑中定义辅助递归函数来帮助构造证明.这种构造方法在不增加系统信任计算基础的情况下可以极大地减轻构造证明的工作量,并且减小安全性证明的规模同时介绍了该方法在一个FPCC系统中的应用.在这个系统中使用该方法使得代码的安全性证明可以自动产生.全部工作的细节已在证明辅助工具Coq中得以实现.     

一种用于指针程序验证的指针逻辑

本文改进并扩展先前为验证指针程序提出的指针逻辑,主要贡献是提出了合法访问路径集合的概念,极大地简化了访问路径上的基本运算,并使得指针逻辑推理规则变得易理解.另外,增加了局部推理规则和函数构造的推理规则,使得指针逻辑可以方便地用于有函数调用的场合.     

汇编代码验证中的形式规范自动生成

与传统的高级语言程序验证相比,汇编代码验证中所需要的形式规范往往比较复杂,通常的做法是要求程序员手写形式规范,或是牺牲形式规范的表达能力以期能够自动生成规范.本文提出一种能够自动生成形式规范的方法,该方法依托一个出具证明的编译器自动生成汇编级形式规范,从而减轻程序员的负担.使用该方法生成的规范比现有的其他方法自动生成的规范具有更强的表达能力.文章主要描述该方法在出具证明编译器中的实现.     

一种可用于编译器调试的目标代码验证方法

传统编译器测试方法是通过比较预期的结果和待测的结果是否一致,以确定编译器是否存在错误。在此基础上,提出了引入参考编译器和参考仿真器的测试方法,在指令集软件仿真过程中生成可用于编译器调试的动态数据信息文件,对参考动态数据信息文件和待测动态数据信息文件进行比较,编译器测试工具可根据比较的结果来确定待测编译器存在错误的位置,这对编译器的调试是非常有用的。     

一种汇编程序的形式验证框架

在高可信软件的各种性质中,安全性是关注的重点.软件满足安全策略的证明方法是安全性研究的热点之一.根据前期提出的安全程序设计与证明的框架以及指针逻辑推理系统,介绍在所实现的出具证明编译器(certifying compiler)原型系统中有关目标机器的形式定义、汇编程序的形式验证框架以及汇编程序指针程序性质证明等方面的研究.它们的主要特点是汇编验证框架是基于Hoare风格的程序验证方式;与指针有关的性质使用和源语言一级类似的指针逻辑推理系统进行证明;使用一个简单的类型系统完成有关指针的类型检查.     

基于类型注解的认证编译器设计与实现

基于类型注解的认证编译器是安全策略系统的核心部件,它不仅能够用C语言的类型安全子集编写的程序编译成优化的Intel x86／linux汇编语言程序,而且还可以根据类型安全策略的要求产生带注解的汇编程序．实验结果表明,新设计的认证编译器可实现：①类型安全的C语言子集的编译;②许多标准的局部优化;③可以对数组运行时越界操作进行检查．由于安全策略系统的证明是建立在含注解的代码基础之上的,因此,该认证编译器在移动代码安全检查中非常有用。     

Certifying Compilation and Run-Time Code Generation

A certifying compiler takes a source language program and produces object code, as well as a certificate that can be used to verify that the object code satisfies desirable properties, such as type safety and memory safety. Certifying compilation helps to increase both compiler robustness and program safety. Compiler robustness is improved since some compiler errors can be caught by checking the object code against the certificate immediately after compilation. Program safety is improved because the object code and certificate alone are sufficient to establish safety: even if the object code and certificate are produced on an unknown machine by an unknown compiler and sent over an untrusted network, safe execution is guaranteed as long as the code and certificate pass the verifier.Existing work in certifying compilation has addressed statically generated code. In this paper, we extend this to code generated at run time. Our goal is to combine certifying compilation with run-time code generation to produce programs that are both fast and verifiably safe. To achieve this goal, we present two new languages with explicit run-time code generation constructs: Cyclone, a type safe dialect of C, and TAL/T, a type safe assembly language. We have designed and implemented a system that translates a safe C program into Cyclone, which is then compiled to TAL/T, and finally assembled into executable object code. This paper focuses on our overall approach and the front end of our system; details about TAL/T will appear in a subsequent paper.     

PCC中数组边界检查的优化和生成

PCC的数组边界检查存在着由于无法确定数组下标表达式符号值的范围，而造成拒绝执行一些安全的移动代码等问题。本文给出的一种数组边界检查的优化及生成算法，不仅能够比较好地解决了这一问题，同时还生成了循环不变式注解中的条件谓词。我们设计的编译器——认证编译器——已经实现了这些算法，并完成了从用C编程语言的类型安全子集编写的源程序到携带注解的Intelx86／linux汇编语言程序的编译过程。由于基于语言安全策略系统的证明是建立在携带注解的代码基础之上的，因此该认证编译器中实现的算法在移动代码安全检查中非常有用。     

Interactive and Probabilistic Proof of Mobile Code Safety

This paper proposes a new proof-based approach to safe evolution of distributed software systems. Specifically, it extends the simple certification mechanism of proof-carrying code (PCC) to make it interactive and probabilistic, thereby devising interactive proof-carrying code (iPCC). With iPCC, a code consumer is convinced, with overwhelming probability, of the existence and validity of a safety proof of a transmitted code through interaction with a code producer. The iPCC mechanism theoretically solves the problem of proof explosion with PCC and can be used to efficiently prove a greater variety of safety properties that may require longer proofs. Technically, the class (PSPACE) of safety properties that are efficiently provable by iPCC is larger than the class (NP) efficiently provable by PCC. To illustrate the power of iPCC, this paper demonstrates that the verification of certain basic safety properties of typical machine instruction codes needs co-NP-complete computation, and shows how these safety properties can be efficiently verified by the iPCC mechanism.This is an extended and revised version of Tsukada (2001a), which appeared in the Proceedings of the 2000 International Symposium on Principles of Software Evolution. A preliminary version was also presented at the International Conference on Advances in Infrastructure for Electronic Business, Science, and Education on the Internet (Tsukada, 2001b).     

Completeness of a Bytecode Verifier and a Certifying Java-to-JVM Compiler

During an attempt to prove that the Java-to-JVM compiler generates code that is accepted by the bytecode verifier, we found examples of legal Java programs that are rejected by the verifier. We propose therefore to restrict the rules of definite assignment for the try-finally statement as well as for the labeled statement so that the example programs are no longer allowed. Then we can prove, using the framework of Abstract State Machines, that each program from the slightly restricted Java language is accepted by the Bytecode Verifier. In the proof we use a new notion of bytecode type assignment without subroutine call stacks. This revised version was published online in August 2006 with corrections to the Cover Date.