Extract https://www.kotobee.com/

My friend’s university sent her today a PDF file that was bundled inside an MS windows executable (exe), she needed to run it outside of the Windows machine. Upon extracting it, I found it was bundled as a Kotobee ebook, which turned to be a DRM service to create “interactive books”. After doing a quick binary analysis to ensure that we are indeed dealing with a DRM’d exe file (and not embarrassingly fdoc file renamed to be .exe), I managed to build a document out of it. Here’s the steps:

First of all, simply, extract the exe content:

unzip file.exe -d extracted_directory

The extracted directory should have a similar tree to this:

larrasket [~/tmp/rq/e]$ ls -l
total 152
-rw-r--r-- 1 l l   2227 Aug 21 14:42 config.js
drwxr-xr-x 1 l l     44 Aug 21 14:42 css
drwxr-xr-x 1 l l     52 Aug 21 14:42 epub
drwxr-xr-x 1 l l     90 Aug 21 14:42 fonts
-rw-r--r-- 1 l l  10709 Aug 21 14:42 icon.png
drwxr-xr-x 1 l l      4 Aug 21 14:42 img
drwxr-xr-x 1 l l      0 Aug 21 14:42 imgUser
-rw-r--r-- 1 l l  14844 Aug 21 14:42 index.html
drwxr-xr-x 1 l l     98 Aug 21 14:42 js
drwxr-xr-x 1 l l     74 Aug 21 14:42 lib
drwxr-xr-x 1 l l    232 Aug 21 14:42 locales
-rw-r--r-- 1 l l 116350 Aug 21 14:42 npmModules.min.js
-rw-r--r-- 1 l l    294 Aug 21 14:42 package.json

From here it’s very obvious that we can run this node app in a web server. You can run a simple http server here:

python3 -m http.server 9000

And the app will be available at port 9000. Alternatively you can build an epub from the provided epub directory:

Inside the epub directory append the mimetype

zip -0X "../book.epub" mimetype
zip -rDX9 "../book.epub" * -x "*.DS_Store" -x mimetype

This will get you the epub. Right after, you can convert it to pdf with epub-tools:

ebook-convert ../book.epub ../book.pdf

As a single command:

(zip -0X "../book.epub" mimetype && \\
     zip -rDX9 "../book.epub" * -x "*.DS_Store" -x mimetype) \\
        && ebook-convert ../book.epub ../book.pdf