TCD: Statically Detecting Type Confusion Errors in C plus plus Programs

For performance reasons, C++, albeit unsafe, is often the programming language of choice for developing software infrastructures. A serious type of security vulnerability in C++ programs is type confusion, which may lead to program crashes and control flow hijack attacks. While existing mitigation solutions almost exclusively rely on dynamic analysis techniques, which suffer from low code coverage and high overhead, static analysis has rarely been investigated. This paper presents TCD, a static type confusion detector built on top of a precise demand-driven field-, context- and flow-sensitive pointer analysis. Unlike existing pointer analyses, TCD is type-aware as it not only preserves the type information in the pointed-to objects but also handles complex language features of C++ such as multiple inheritance and placement new, making it therefore possible to reason about type casting in C++ programs. We have implemented TCD in LLVM and evaluated it using seven C++ applications (totaling 526,385 lines of C++ code) from Qt, a widely-adopted C++ toolkit for creating GUIs and cross-platform software. TCD has found five type confusion bugs, including one reported previously in prior work and four new ones, in under 7.3 hours, with a low false positive rate of 28.2%.