Strong Optimistic Solving for Dynamic Symbolic Execution

Dynamic symbolic execution (DSE) is an effective method for automated program testing and bug detection. It is increasing the code coverage by the complex branches exploration during hybrid fuzzing. DSE tools invert the branches along some execution path and help fuzzer examine previously unavailable program parts. DSE often faces over- and underconstraint problems. The first one leads to significant analysis complication while the second one causes inaccurate symbolic execution. We propose strong optimistic solving method that eliminates irrelevant path predicate constraints for target branch inversion. We eliminate such symbolic constraints that the target branch is not control dependent on. Moreover, we separately handle symbolic branches that have nested control transfer instructions that pass control beyond the parent branch scope, e.g. return, goto, break, etc. We implement the proposed method in our dynamic symbolic execution tool Sydr. We evaluate the strong optimistic strategy, the optimistic strategy that contains only the last constraint negation, and their combination. The results show that the strategies combination helps increase either the code coverage or the average number of correctly inverted branches per one minute. It is optimal to apply both strategies together in contrast with other configurations

Sydr-Fuzz: Continuous Hybrid Fuzzing and Dynamic Analysis for Security Development Lifecycle

Nowadays automated dynamic analysis frameworks for continuous testing are in high demand to ensure software safety and satisfy the security development lifecycle~(SDL) requirements. The security bug hunting efficiency of cutting-edge hybrid fuzzing techniques outperforms widely utilized coverage-guided fuzzing. We propose an enhanced dynamic analysis pipeline to leverage productivity of automated bug detection based on hybrid fuzzing. We implement the proposed pipeline in the continuous fuzzing toolset Sydr-Fuzz which is powered by hybrid fuzzing orchestrator, integrating our DSE tool Sydr with libFuzzer and AFL++. Sydr-Fuzz also incorporates security predicate checkers, crash triaging tool Casr, and utilities for corpus minimization and coverage gathering. The benchmarking of our hybrid fuzzer against alternative state-of-the-art solutions demonstrates its superiority over coverage-guided fuzzers while remaining on the same level with advanced hybrid fuzzers. Furthermore, we approve the relevance of our approach by discovering 85 new real-world software flaws within the OSS-Sydr-Fuzz project. Finally, we open Casr source code to the community to facilitate examination of the existing crashes