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Facebook Awards Researchers $100k For Detecting Emerging Class of C++ Bugs
An anonymous reader writes: Facebook has awarded $100,000 to a team of researchers from Georgia Tech University for their discovery of a new method for identifying "bad-casting" vulnerabilities that affect programs written in C++. "Type casting, which converts one type of an object to another, plays an essential role in enabling polymorphism in C++ because it allows a program to utilize certain general or specific implementations in the class hierarchies. However, if not correctly used, it may return unsafe and incorrectly casted values, leading to so-called bad-casting or type-confusion vulnerabilities," the researchers explained in their paper.
dynamic_cast requires RTTI, which means you're a bit optimistic to say "Most caught at compile time, for other casts use dynamic_cast".
Of course, templates mean that the compiler can substitute actual types. That gives you compile-time polymorphism instead of runtime polymorphism, and that in turn means you're increasingly right that most cast errors are caught at compile time. The price is unfortunately even longer compile times. Guess why I'm posting right now....
I actually read the paper (okay, mod me down). Java and .Net have very strong runtime typing systems. C/C++ does not. Adding one is a bit tricky because there are certain things that are legal in C/C++ and not Java. Specifically, it's okay to cast between two classes that are non-polymorphic (unrelated from a type system perspective). Also C/C++ applications often have some additional performance requirements. They've created a runtime typing system and then a mechanism (probably a pre-processor) that can cause static_cast and dynamic_cast to instead use their casting mechanism. You turn it on for debug and off for release. We already have things like debug heaps to look for memory corruption at a small performance cost why not also have a debug type checking system. And, of course, since it gets switched off in production builds, it doesn't have the runtime performance costs. It's one of those things that is obvious as soon as somebody does it. Those are often some of the best advances as they can have a lot of impact quickly.