LeastProtocol: Minimizing Attack Surface by Removing Unwanted Protocol Features

Standard protocols such as SSL, SSH, etc. are implemented as one-size-fits-all libraries. To maximize compatibility, these libraries implement rarely used features that increase attack surface. Examples include the SSL Heart Beat feature (HeartBleed) and weak SSH ciphers (LOGJAM).The Navy would like to reduce software attack surface by removing unused protocol features. Our proposal, LeastProtocol, aims to develop a means to identify and eliminate features from existing software binaries. We will base our feature removal and identification research on two techniques: monitored execution and differential slicing. Multiple research papers have demonstrated that monitored execution combined with statistical techniques can map coarse protocol features to implementation code. Differential slicing compares two program executions and identifies locations where execution differs, enabling precise feature identification.For Phase 1, we will implement a proof of concept that works on a single protocol and implementation. The protocol and implementation will be of a real, deployed protocol but limited to open source software that runs on x86 Linux. We envision LeastProtocol will accept a protocol specification, a list of features, and a program binary. The tool will output a new binary that speaks the same protocol sans unwanted features.