Down to the Wire

Posts by Zach Wade

PlaidCTF 2018: I Heard You Like XSS

Zachary Wade

In preparation for PlaidCTF 2018 I designed a two part web challenge called S-Exploitation (Paren Trap and the Wizard of OSS). Although I intended the first part to be an easier web challenge, and the second to be a tricky follow up, the former had only 16 solves and the latter just 2. Since I had a number of people ask me for clarification after the CTF, and to help other organizers to learn from it, I’ve described below how S-exploitation was designed and meant to be solved.

GADTs: Wizardry for a Typesafe Age

Zachary Wade

Generalized algebraic data types (or GADTs) are a powerful tool that can augment algebraic type systems enabling them to be far more expressive. In addition to enabling polymorphic recursion, they also serve as a fundamental unit for existential types. In this post we will look at what all of those phrases mean, and how GADTs can be used in practice.

To Depart from Clemency: A DEF CON 2017 Retrospective

Zachary Wade

Another year, another DEF CON. This year, from the far reaches of LegitBS’s wild imagination came an architecture so bizarre and so confusing that it was actually pretty good. Over the course of three days, we were introduced to cLEMENCy, an intriguing RISC architecture that sported 9-bit bytes, middle endianness, and reversible stacks. It took many sleepless nights, but once again the were able to tool and exploit our way to a tight victory. As a member of the Plaid Parliament of Pwning, here is an overview of the year’s biggest CTF from my perspective.

A DefCon 2016 Retrospective

Zachary Wade

Defcon CTF 2016 was held from August 5th to 7th during the annual Defcon conference. This year DARPA chose to host their Cyber Grand Challenge (CGC) — a CTF-style competition between fully autonomous Cyber Reasoning Systems (CRS’) — at Defcon as well, so the Legitimate Business Syndicate oriented their competition around it to allow the winning machine to compete against the human teams. The new format brought with it several interesting gameplay mechanisms as well as a couple of issues, resulting in a fun but occasionally problematic contest. During the competition I played with the Plaid Parliament of Pwning (PPP), with whom I placed first. This is a brief reflection of how the game operated, what succeeded, and what did not.

Context Free Grammars and the Tyranny of Node

Zachary Wade

While language and grammar are undoubtably linguistic constructs, they have very practical uses inside the realm of computer science. However, while looking for language and grammar parsing tools written for Node, I was disappointed to find no easy-to-use and suitably-flexible libraries. In response, I began development on Tyranny, a node module that allows for the description and parsing of arbitrary context-free grammars. Here is what it is, how it works, and what it does.

Stream Based Processing in Node

Zachary Wade

Over the past few weeks, I have begun working on a set of tools called hakkit for helping me to write CTF scripts in node.js. Many of the ideas are lifted off of pwnlib, but soon after I started, I realized that by utilizing Node’s stream APIs, I could take my tools a step further than the pwnlib ones. By behaving similar to unix file descriptors, Node streams allow for powerful and extensible data manipulation.


Zachary Wade

Welcome to Down to the Wire!

In the coming weeks we will start adding posts and discussing current projects and goals, including an upcoming post about developing Down to the Wire itself. Until then, however, I wanted to share a little bit about what DttW is, and why we decided to start it.