Reverse analysis and fuzzy testing of a communication protocol for new power system terminals

Abstract

Most of the existing new power system terminals use private protocols of third-party vendors， which often proves to be challenging to analyze. The Modbus protocol commonly used in existing new power system terminals is analyzed in reverse. Based on the characteristics of protocol hierarchy， the valid fields of the unknown protocol are extracted from the header fields of network messages， and the protocol fields are divided into words based on the statistical N-gram algorithm， and a Modbus protocol state machine is constructed using protocol keywords. Further， by protocol source code compilation and instrumentation， the Modbus server-side program is fuzzy tested by generating random test cases， and the test crash results are analyzed. The experimental results show that the scheme is capable of fast reverse identification and fuzzy testing of private protocols from third-party vendors and holds substantial practical value.

Keywords

• new power system terminals
• protocol reverse analysis
• dynamic binary instrumentation
• state machine comparison
• fuzzy testing