Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

3-28-2013

Comments

University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-13-05.

Abstract

C++ remains a widely used programming language, despite retaining many unsafe features from C. These unsafe features often lead to violations of type and memory safety, which manifest as buffer overflows, use-after-free vulnerabilities, or abstraction violations. Malicious attackers are able to exploit such violations to compromise application and system security. This paper introduces Ironclad C++, an approach to bring the benefits of type and memory safety to C++. Ironclad C++ is, in essence, a library-augmented type-safe subset of C++. All Ironclad C++ programs are valid C++ programs, and thus Ironclad C++ programs can be compiled using standard, off-the-shelf C++ compilers. However, not all valid C++ programs are valid Ironclad C++ programs. To determine whether or not a C++ program is a valid Ironclad C++ program, Ironclad C++ uses a syntactic source code validator that statically prevents the use of unsafe C++ features. For properties that are difficult to check statically Ironclad C++ applies dynamic checking to enforce memory safety using templated smart pointer classes. Drawing from years of research on enforcing memory safety, Ironclad C++ utilizes and improves upon prior techniques to significantly reduce the overhead of enforcing memory safety in C++. To demonstrate the effectiveness of this approach, we translate (with the assistance of a semi-automatic refactoring tool) and test a set of performance benchmarks, multiple bug-detection suites, and the open-source database leveldb. These benchmarks incur a performance overhead of 12% on average as compared to the unsafe original C++ code, which is small compared to prior approaches for providing comprehensive memory safety in C and C++.

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Date Posted: 09 May 2013