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r2con{ctf_2019_wr1t3up5}

The r2con CTF is the CTF for the r2con 2019 held during the weekend before the conference which consisted mainly of reversing challenges. I managed to solve all but one challenge (technicaly, at least...) and it was so much fun! I'd like to thank the organizers a lot for making the event happen :-)

There may be errors and inclompete sections. I tried to make a write-up for every challenge, just contact me if anything is unclear or missing!

[100] r2boy1

Time to remember the best games ever!

Effective Modern CMake

Getting Started

For a brief user-level introduction to CMake, watch C++ Weekly, Episode 78, Intro to CMake by Jason Turner. LLVM’s CMake Primer provides a good high-level introduction to the CMake syntax. Go read it now.

After that, watch Mathieu Ropert’s CppCon 2017 talk Using Modern CMake Patterns to Enforce a Good Modular Design (slides). It provides a thorough explanation of what modern CMake is and why it is so much better than “old school” CMake. The modular design ideas in this talk are based on the book [Large-Scale C++ Software Design](https://www.amazon.de/Large-Scale-Soft

Setup

Add this to your .profile, .bashrc, .zshrc...

decode_base64_url() {
  local len=$((${#1} % 4))
  local result="$1"
  if [ $len -eq 2 ]; then result="$1"'=='
  elif [ $len -eq 3 ]; then result="$1"'=' 
  fi
 echo "$result" | tr '_-' '/+' | openssl enc -d -base64

	// ltrace seems to be failing when getenv is called by shared object
	// gcc -shared -fpic -ldl -o hook_getenv.so hook_getenv.c

	#define _GNU_SOURCE
	#include <stdio.h>
	#include <stdlib.h>
	#include <dlfcn.h>
	#include <limits.h>
	#include <errno.h>
	#include <sys/stat.h>

	#include <iostream>
	#include <stdio.h>
	#include <stdlib.h>
	#include <linux/ioctl.h>
	#include <linux/types.h>
	#include <linux/v4l2-common.h>
	#include <linux/v4l2-controls.h>
	#include <linux/videodev2.h>
	#include <fcntl.h>
	#include <unistd.h>

	# Thanks to @danger89 and @Ilothar for updating the gist.
	# Set the name and the supported language of the project
	project(hello-world C CXX)

	# Set the minimum version of cmake required to build this project
	cmake_minimum_required(VERSION 3.10)

	# Use the package PkgConfig to detect GTK+ headers/library files
	find_package(PkgConfig REQUIRED)
	pkg_check_modules(GTK REQUIRED gtkmm-3.0)