vm-and-bytecode-reverse

Name: vm-and-bytecode-reverse
Availability: InStock
Author: doriangallo

Reconstruct custom virtual-machine bytecode and map opcode handlers to semantics.

5|2|Updated May 16, 2026

Search Tags:#bytecode #vm #reverse engineering #disassembler #dynamic tracing #opcode mapping #ctf solving

Ready to run

npx skills add https://github.com/DorianGallo/hack-skills-local --skill vm-and-bytecode-reverse-doriangallo

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: vm-and-bytecode-reverse
Source: https://github.com/DorianGallo/hack-skills-local/tree/main/skills/vm-and-bytecode-reverse
Command: npx skills add https://github.com/DorianGallo/hack-skills-local --skill vm-and-bytecode-reverse-doriangallo

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

This Skill helps you reverse custom virtual machines and bytecode interpreters so you can understand how protected programs validate input and produce outputs.

Core Features & Use Cases

Dispatcher Identification & ISA Reconstruction: Find switch/table/if-chain dispatch loops and map opcode handlers into an instruction set you can reason about.
Bytecode Extraction & Custom Disassembly: Locate the bytecode program and build a purpose-fit disassembler to turn opaque byte streams into readable operations.
CTF-Oriented Solving Workflows: Handle common VM patterns (stack/register/maze/bf-like) and apply real-world protector analysis strategies to reach the underlying check logic.

Quick Start

Use the vm-and-bytecode-reverse Skill to identify the VM dispatcher in a target binary, map opcodes to semantics, extract the bytecode program, and produce a custom disassembly that reveals the exact input transformations to solve the challenge.

Frequently Asked Questions about vm-and-bytecode-reverse

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I reverse engineer a custom virtual machine and reconstruct its bytecode instruction set?▼

To reverse a custom virtual machine, identify the dispatcher structure, map opcode handlers to operands and side effects, extract the bytecode program, and write a custom disassembler to recover the underlying instruction set semantics.

What is the best way to analyze a fetch-decode-execute interpreter in a protected binary?▼

Analyzing a fetch-decode-execute interpreter involves locating the dispatch loop, mapping individual opcode handlers to their specific side effects, and extracting the embedded bytecode program to reveal the exact input validation logic.

How do I solve CTF challenges that use maze-style grid logic or proprietary VM dispatchers?▼

Solving CTF challenges with proprietary VM dispatchers requires mapping opcode handlers, building a custom disassembler or dynamic tracer, and applying constraint-based reversal to understand the maze-style grid logic and input checks.

Can I trace bytecode execution dynamically to understand input validation logic in protected software?▼

Yes, you can write a custom dynamic tracer to trace bytecode execution, map opcode semantics, and guide constraint-based or manual reversal to recover the exact input transformations and validation logic of protected software.

Does this approach work for reversing stack-based, register-based, and brainfuck-like VM architectures?▼

This approach handles common VM patterns including stack-based, register-based, maze-style, and brainfuck-like architectures by reconstructing the instruction set and applying real-world protector analysis strategies.

Why does bytecode remain opaque when analyzing a proprietary dispatcher, and how do I make it readable?▼

Bytecode remains opaque because proprietary dispatchers use custom opcodes. To make it readable, map the opcode handlers, extract the byte stream, and build a purpose-fit disassembler to turn opaque bytes into readable operations.