Custom VM Challenges

This repository contains a collection of CTF challenges I created for niteCTF 2025. The challenges are all based on a custom-built virtual machine and cover binary exploitation and reverse engineering.

Core VM Architecture

All challenges use a shared, custom stack-based virtual machine. The complete source code for the VM, the assembler, and the instruction set documentation are located in the vm_src/ directory.

Building the VM

To build the VM, navigate to the vm_src/src directory and run make:

cd vm_src/src
make

Challenges

1. virtual_rift (Pwn)

A binary exploitation challenge that requires finding and exploiting a heap out-of-bounds vulnerability in the VM to gain code execution.

• Challenge files: virtual_rift/
• Solution: virtual_rift/README.md

2. ghost_in_the_machine (Rev)

A reverse engineering challenge where you must analyze a program running on the VM to understand its custom encryption algorithm and decrypt the flag.

• Challenge files: ghost_in_the_machine/
• Solution: ghost_in_the_machine/README.md