Creating high-performance statically type-safe network applications

A typical Internet server finds itself in the middle of a virtual battleground, under constant threat from worms, viruses and other malware seeking to subvert the original intentions of the programmer. In particular, critical Internet servers such as OpenSSH, BIND and Sendmail have had numerous security issues ranging from low-level buffer overflows to subtle protocol logic errors. These problems have cost billions of dollars as the growth of the Internet exposes increasing numbers of computers to electronic malware. Despite the decades of research on techniques such as model-checking, type-safety and other forms of formal analysis, the vast majority of server implementations continue to be written unsafely and informally in C/C++. In this dissertation we propose an architecture for constructing new implementations of standard Internet protocols which integrates mature formal methods not currently used in deployed servers: (i) static type systems from the ML family of functional languages; (ii) model checking to verify safety properties exhaustively about aspects of the servers; and (iii) generative meta-programming to express high-level constraints for the domain-specific tasks of packet parsing and constructing non-deterministic state machines. Our architecture—dubbed MELANGE—is based on Objective Caml and contributes two domain-specific languages: (i) the Meta Packet Language (MPL), a data description language used to describe the wire format of a protocol and output statically type-safe code to handle network traffic using high-level functional data structures; and (ii) the Statecall Policy Language (SPL) for constructing non-deterministic finite state automata which are embedded into applications and dynamically enforced, or translated into PROMELA and statically model-checked. Our research emphasises the importance of delivering efficient, portable code which is feasible to deploy across the Internet. We implemented two complex protocols—SSH and DNS—to verify our claims, and our evaluation shows that they perform faster than their standard counterparts OpenSSH and BIND, in addition to providing static guarantees against some classes of errors that are currently a major source of security problems.