A Guide to Kaitai Web IDE

This post is a continuation of my previous post about Kaitai Struct DSL language for description of binary data formats. This post will describe how to download Kaitai Web IDE and run it locally as a web application and  also how to build and run it.

Prerequisites

If you are interested to run Kaitai Web IDE locally or take part in its development then there is a need to install some additional software, such as

• Anaconda 2/3 that will help install
  • Git
  • Python 2/3
  • Node.js (to be able to build locally)

This guide will explain how to do it on Windows and Linux(Ubuntu). 

In addition the following versions will be used

• Anaconda with Python 2.7
• Git 2.14.1
• Python 2.7
• Node.js 6.11.0

Anaconda for the rescue

Anaconda is a package manager for various libraries be it Python, Node.js etc. We’ll use it to install all the dependencies we need for Kaitai Web IDE.

1. Download Anaconda from official site

For the sake of this tutorial you can chose either Python 2.7 or 3.6 version.

2. Install Anaconda as any application.

Look for newly installed programs and run Anaconda Prompt (Windows)

3. Open command line or Anaconda prompt and install Git (taken from here)

conda install -c conda-forge git

4. Approve if asked to install any additional packages.

5. Test that Git was installed correctly

C:\Users>git --version
git version 2.14.1.windows.1

6. Clone or download Kaitai Web IDE stable release from GitHub repository.

git clone https://github.com/kaitai-io/ide-kaitai-io.github.io

7. You’ll see output resembling this one

C:\Users>git clone https://g
ithub.com/kaitai-io/ide-kaitai-io.github.io
Cloning into 'ide-kaitai-io.github.io'...
remote: Counting objects: 3003, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 3003 (delta 0), reused 1 (delta 0), pack-reused 2995
Receiving objects: 100% (3003/3003), 5.98 MiB | 5.11 MiB/s, done.
Resolving deltas: 100% (2118/2118), done.

To run Kaitai Web IDE as is 

8. Open the folder where you placed Kaitai Web IDE (in my case

C:\Users\ide-kaitai-io.github.io

)

9. Run following command to lunch web server that will host locally Kaitai Web IDE app

python -mSimpleHTTPServer

10. Go to http://127.0.0.1:8000/

Note: pay attention that instead of port 8000 you may need to use any other such as 8888 if 8000 is used by some application if you see the error below

socket.error: [Errno 10013] An attempt was made to access a socket in a way forb
idden by its access permissions

10 (in case of error). To fix this execute previous command with a port as an argument

python -mSimpleHTTPServer 8888

Go to http://127.0.0.1:8888/

As you can see in the screenshot below I had to run on port 8888 and Kaitai Web IDE is up and running!

Build it yourself

If you want to build Kaitai Web IDE yourself then install additional software with Anaconda.

The attempt below failed but the one after it passed. I preserve it for the sake of an argument (it can be done easily on Linux)

11. Install Node.js from here

conda install -c conda-forge nodejs 

12. Approve if asked to install any additional packages.

And there was an error on Windows (why is that?)

CondaError: WindowsError(206, 'The filename or extension is too long')

12 (once again). Ok. Then let’s download and install Node.js from official site.

13. Open command prompt and test Node.js version

C:\Users\iscamc>node --version
v6.11.3

We are almost on the finish line. To build Kaitai Web IDE

14. Clone or download Kaitai Web IDE stable release from GitHub repository.

git clone --recursive https://github.com/kaitai-io/kaitai_struct_webide

You’ll see output like this

C:\Users>git clone --recursi
ve https://github.com/kaitai-io/kaitai_struct_webide
Cloning into 'kaitai_struct_webide'...
remote: Counting objects: 5175, done.
remote: Compressing objects: 100% (17/17), done.
remote: Total 5175 (delta 6), reused 12 (delta 5), pack-reused 5153
Receiving objects: 100% (5175/5175), 9.63 MiB | 4.49 MiB/s, done.
Resolving deltas: 100% (3852/3852), done.
Submodule 'formats' (https://github.com/kaitai-io/kaitai_struct_formats/) regist
ered for path 'formats'
Cloning into 'C:/Users/kaitai_struct_webide/formats'...
remote: Counting objects: 1576, done.
remote: Compressing objects: 100% (58/58), done.
remote: Total 1576 (delta 37), reused 63 (delta 23), pack-reused 1495
Receiving objects: 100% (1576/1576), 431.29 KiB | 2.82 MiB/s, done.
Resolving deltas: 100% (888/888), done.
Submodule path 'formats': checked out 'a3643b677daccfd323f7d9ace998292c9ee51811'

15. Open the folder where you placed Kaitai Web IDE (in my case 

C:\Users\ide-kaitai-io.github.io

)

16. Run following command to install all the JavaScript and TypeScript dependencies with 

npm install

17. Now  compile and run the Web IDE itself

python serve.py --compile

Note: pay attention that instead of port 8000 you may need to use any other such as 8888 if 8000 is used by some application if you see the error below

socket.error: [Errno 10013] An attempt was made to access a socket in a way forb
idden by its access permissions

To fix this error open in any text editor of your choice serve.py file that resides inside Kaitai folder in my case in C:\Users\kaitai_struct_webide and replace PORT=8000 with, say PORT=8888  on line 15.

17 (in case of error). Rerun command below

python serve.py --compile

When everything worked nice you’ll see something like this

C:\Users\kaitai_struct_webide>python serve.py --compile
Starting typescript compiler...
Please use 127.0.0.1:8888 on Windows (using localhost makes 1sec delay)
Press Ctrl+C to exit.
12:57:28 AM - Compilation complete. Watching for file changes.

18. Go to http://127.0.0.1:8888/

Congratulations you’ve build Kaitai Web IDE!

 

Reverse engineering the easy way

Imagine you have some kind of 3rd party data storage that you need to understand how to work with and the only thing you have is a detailed description of the protocol using the device. The only problem is that there is no source code available that can make this process easy to accomplish. And what is left is to implement manually this protocol while having lots of trial and error iterations. Next time in similar occasion repeat this difficult process once again. But no worries, there is one tool that comes in handy in situations like this when there is a file or a stream that you want to parse and you want to be able to do it fast.  

Meet Kaitai Struct

First, here comes an official description of Kaitai Struct

Kaitai Struct is a domain-specific language (DSL) that is designed with one particular task in mind: dealing with arbitrary binary formats.

Parsing binary formats is hard, and that’s a reason for that: such formats were designed to be machine-readable, not human-readable. Even when one’s working with a clean, well-documented format, there are multiple pitfalls that await the developer: endianness issues, in-memory structure alignment, variable size structures, conditional fields, repetitions, fields that depend on other fields previously read, etc, etc, to name a few.

Kaitai Struct tries to isolate the developer from all these details and allow to focus on the things that matter: the data structure itself, not particular ways to read or write it.

Features

• Kaitai is supported on Linux and Windows (not sure about Mac).
• So far, Kaitai supports generating parsers in following languages
  • C++/STL
  • C#
  • Java
  • JavaScript
  • Perl
  • PHP
  • Python
  • Ruby
• If you want you are welcome to add one more language to the list

How to use this Kaitai?

In short, to use Katai 

• You use declarative syntax to describe a data source you want to be able to parse, such as file system or image format or whatever you like, in ksy file. 
• Then using Kaitai Web IDE or Katai Struct compiler you generate a code in one of the relevant supported languages, such as Java, C#, C++ etc.
• That’s it. Now use the code to get full access to your data source.

Kaitai REPL (Read–Eval–Print Loop) 

To get a feeling what Kaitai is capable of you can start from playing with Kaitai REPL which has a number of examples showcasing what can be achieved with it, such as parsing doom.wad package files format.

Katai Web IDE

If you think you are ready to start applying Kaitai to real problems then jump into Katai Web IDE which is very nice and easy to use. You can upload there your data source and start writing a description of how the data source is organized. 

This official wiki page will show you the main features or Web IDE.

Kaitai Compiler stand alone 

It is possible to use Katai compiler in a stand alone mode via command line interface of your choice be it on Linux, Windows etc. How to do it is described here.

Resources

• Kaitai User Guide
• Kaitai Struct: KSY reference
• See what file formats were already described with Kaitai and maybe you’ll spare an effort re-implementing them yourself.
• Kaitai presentation Dissecting media file formats with Kaitai Struct by Mikhail Yakshin

• Reverse Engineering of Binary Structures Using Kaitai Struct by Mikhail Yakshin

  • English
  • Russian
• Reverse engineering visual novels 101 by Masumi Nakamura

• Reverse engineering visual novels 101, part 2 by Masumi Nakamura