Enhancing Conformance Testing Using Symbolic Execution for Network Protocols

Security protocols are notoriously difficult to get right, and most go through several iterations before their hidden security vulnerabilities, which are hard to detect, are triggered. To help protocol designers and developers efficiently find non-trivial bugs, we introduce SYMCONF, a practical conformance testing tool that generates high-coverage test input packets using a conformance test suite and symbolic execution. Our approach can be viewed as the combination of conformance testing and symbolic execution: 1) it first selects symbolic inputs from an existing conformance test suite; 2) it then symbolically executes a network protocol implementation with the symbolic inputs; and 3) it finally generates high-coverage test input packets using a conformance test suite. We demonstrate the feasibility of this methodology by applying SYMCONF to the generation of a stream of high quality test input packets for multiple implementations of two network protocols, the Kerberos Telnet protocol and Dynamic Host Configuration Protocol (DHCP), and discovering non-trivial security bugs in the protocols.