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We propose a method, based on program analysis and transformation, for eliminating timing side channels in software code that implements security-critical applications. Our method takes as input the original program together with a list of secret variables (e.g., cryptographic keys, security tokens, or passwords) and returns the transformed program as output. The transformed program is guaranteed to be functionally equivalent to the original program and free of both instruction- and cache-timing side channels. Specifically, we ensure that the number of CPU cycles taken to execute any path is independent of the secret data, and the cache behavior of memory accesses, in terms of hits and misses, is independent of the secret data. We have implemented our method in LLVM and validated its effectiveness on a large set of applications, which are cryptographic libraries with 19,708 lines of C/C++ code in total. Our experiments show the method is both scalable for real applications and effective in eliminating timing side channels. 

A unified modeling framework for non-functional properties of a program is essential for research in software analysis and verification, since it reduces burdens on individual researchers to implement new approaches and compare existing approaches. We present CANAL, a framework that models the cache behaviors of a program by transforming its intermediate representation in the LLVM compiler. CANAL inserts auxiliary variables and instructions over these variables, to allow standard verification tools to handle a new class of cache related properties, e.g., for computing the worst-case execution time and detecting side-channel leaks. We demonstrate the effectiveness of using three verification tools: KLEE, SMACK and Crab-llvm. We confirm the accuracy of our cache model by comparing with CPU cycle-accurate simulation results of GEM5. CANAL is available on GitHub(https://github.com/canalcache/canal) and YouTube(https://youtu.be/JDou3F1j2nY).