I was playing a lot with radare2 in the past year, ever since I began participating in CTFs and got dAnalyze alleeper into RE and exploitation challenges. I found radare2 very helpful with many CTFs tasks and my solutions had shortened significantly. It’s sometimes also my go-to tool for malware analysis tasks such as configuration retrievals. Sadly, I believe that only few people are familiar with radare2. It might be because they’re afraid to break out of their comfort zone (IDA Pro, OllyDBG, gdb) or they have simply not heard of it. Either way, I honestly believe that you must include radare2 in your toolbox.
Because I got really enthusiastic about the project and I want more and more researchers to be familiar with it, use it and hopefully contribute to the project, I decided to create a series of articles and use-cases of r2. Since these articles aim to teach you the basics of radare2, its features and capabilities, I’ll explain much more than you actually need to know in order to solve each task.
Welcome to IDA 10.0. (see radare2/doc/fortunes.fun for more fortunes)
radare2 is an open source framework for reverse engineering and binaries analysis which implements a rich command line interface for disassembling, analyzing data, patching binaries, comparing data, searching, replacing, visualizing and more. It has great scripting capabilities, it runs on all major platforms (GNU/Linux, .Windows *BSD, iOS, OSX, Solaris…) and it supports tons of architectures and file formats. But maybe above all of its features stands the ideology – radare2 is absolutely libre.
This framework is composed of a set of utilities that can be used either together from r2 shell or independently – We’ll get familiar with tools such as rahash2, rabin2, ragg2. Together they create one of the most powerful tools in the field of static and dynamic analysis, hex editing and exploitation (I’ll dive deeper in the following articles).
It is important to note that r2’s learning curve is pretty steep – although r2 have a GUI and a WebUI, none of them is quite enough to compete with the GUI or the convenience of IDA, IMHO. The CLI, however, including its Visual Mode, is still the core of radare2 and where its power lays. Because of its complexity I’ll try to make things as clear and simple as I can.
This is more or less how r2 learning curve works.
Before we begin you can check out the “Unfair comparison between r2, IDA Pro and Hopper” to get an idea of what we’re dealing with.
Radare2’s development is pretty quick – the project evolves every day, therefore it’s recommended to use the current git version over the stable one. Sometimes the stable version is less stable than the current git version!
$ git clone https://github.com/radare/radare2.git
$ cd radare2
If you don’t want to install the git version or you want the binaries for another machine (Windows, OS X, iOS, etc) check out the download page at the radare2 website.
As I said before, it is highly recommended to always use the newest version of r2 from the git repository. All you need to do to update your r2 version from the git is to execute:
And you’ll have the latest version from git. I usually update my version of radare2 in the morning, while watching cat videos.
I Can’t think of a reason for you to uninstall radare2 so early in the article but if you do have you can simply execute:
$ make uninstall
$ make purge
You can download the first challenge here.
Now that radare2 is installed on your system and you have downloaded the binary, we are ready to start exploring the basic usage of radare2. I’ll work on a Remnux machine but most of the commands and explanations (if not all of them) would be the same for Windows machines and others.
Command Line Arguments
As most command line utilities, the best approach to reveal the list of the possible arguments is to execute the program with the
$ r2 -h
I won’t paste here the full output, Instead I’ll point out those which I usually use in my daily work:
Usage: r2 [-ACdfLMnNqStuvwz] [-P patch] [-p prj] [-a arch] [-b bits] [-i file]
[-s addr] [-B baddr] [-M maddr] [-c cmd] [-e k=v] file|pid|-|--|=
-d: Debug the executable 'file' or running process 'pid'
-A: Analyze executable at load time (xrefs, etc)
-q: Quiet mode, exit after processing commands
-w: Write mode enabled
-L: List of supported IO plugins
-i [file]: Interprets a r2 script
-n: Bare load. Do not load executable info as the entrypoint
-c 'command; command; ...': Run r2 and execute commands (eg: r2 's main; px 60')
-p [prj]: Creates a project for the file being analyzed
-: Opens r2 with the malloc plugin that gives a 512 bytes memory area to play with