mcsema - The Trail of Bits Blog

As a summer intern at Trail of Bits, I’ve been working on building Fennec, a tool to automatically replace function calls in compiled binaries that’s built on top of McSema, a binary lifter developed by Trail of Bits. The Problem Let’s say you have a compiled binary, but you […]

C++ programs using exceptions are problematic for binary lifters. The non-local control-flow “throw” and “catch” operations that appear in C++ source code do not map neatly to straightforward binary representations. One could allege that the compiler, runtime, and stack unwinding library collude to make exceptions work. We recently completed our investigation into exceptions and can […]

Today, we’re going to talk about a hard problem that we are working on as part of DARPA’s Cyber Fault-Tolerant Attack Recovery (CFAR) program: automatically protecting software from 0-day exploits, memory corruption, and many currently undiscovered bugs. You might be thinking: “Why bother? Can’t I just compile my code with exploit mitigations like stack guard, […]

Tim Alberdingk Thijm As part of my Springternship at Trail of Bits, I created a series of data-flow-based optimizations that eliminate most “dead” stores that emulate writes to machine code registers in McSema-lifted programs. For example, applying my dead-store-elimination (DSE) passes to Apache httpd eliminated 117,059 stores, or 50% of the store operations to Remill’s […]

Four years ago, we released McSema, our x86 to LLVM bitcode binary translator. Since then, it has stretched and flexed; we added x86-64 support, put it on a performance-focused diet, and improved its usability and documentation. McSema wasn’t the only thing improving these past years, though. At the same time, programs were increasingly adopting modern […]

McSema, our x86 machine code to LLVM bitcode binary translator, just got a fresh coat of paint. Last week we held a successful hackathon that produced substantial improvements to McSema’s usability, documentation, and code quality. It’s now easier than ever to use McSema to analyze and reverse-engineer binaries. Growth stage We use McSema on a […]

The Cyber Grand Challenge qualifying event was held on June 3rd, at exactly noon Eastern time. At that instant, our Cyber Reasoning System (CRS) was given 131 purposely built insecure programs. During the following 24 hour period, our CRS was able to identify vulnerabilities in 65 of those programs and rewrite 94 of them to […]

This is part two of a two-part blog post that shows how to use KLEE with mcsema to symbolically execute Linux binaries (see the first post!). This part will cover how to build KLEE, mcsema, and provide a detailed example of using them to symbolically execute an existing binary. The binary we’ll be symbolically executing […]

At THREADS 2014, I demonstrated a new capability of mcsema that enables the use of KLEE, a symbolic execution framework, on software available only in binary form. In the talk, I described how to use mcsema and KLEE to learn an unknown protocol defined in a binary that has never been seen before. In the example, […]

We are proud to announce that McSema is now open source! McSema is a framework for analyzing and transforming machine-code programs to LLVM bitcode. It supports translation of x86 machine code, including integer, floating point, and SSE instructions. We previously covered some features of McSema in an earlier blog post and in our talk at ReCON 2014. Our […]

On June 28th Artem Dinaburg and Andrew Ruef will be speaking at REcon 2014 about a project named McSema. McSema is a framework for translating x86 binaries into LLVM bitcode. This translation is the opposite of what happens inside a compiler. A compiler translates LLVM bitcode to x86 machine code. McSema translates x86 machine code into LLVM […]