GCC Static Analyzer (SA) is a highly promising tool aiming to enhance the compiler with extensive analysis capabilities, such as through the use of a plugin API. We used it to implement an analysis targeting constant-time vulnerabilities. Most of the existing tools rely on formal methods and remain barely used (see Jancar et al.). This study conclude that compiler-based tools are well-received among cryptographic developers.

Our initial tests highlighted that the primary design of the analyzer's inner state machines heavily relies on pointer-related analysis, which leverages alias analysis. However, it was triggering undesirable side effects in our case. The needs for our analysis is to also be able to track state for lvalue, alongside rvalue, depending of the target's type.

The subject of this talk is to introduce a practical case where this behavior would allow such analysis to be done, especially since the SA codebase is already heavily prepared for it. A proof-of-concept to give this ability to the SA has been implemented and aims to be merged after feedback from the community on the idea. Problems caused by some aspects of C semantics arise and will be interesting to discuss (e.g., the thin frontier between arrays and pointers).

Source code of the project is publicly available here: https://gitlab.inria.fr/pphilipp/gcc-plugin-ct.

Prior knowledge for attending: GCC internals and GCC SA basic knowledge, C semantics.