> For the complete documentation index, see [llms.txt](https://simon-6.gitbook.io/simoncyber/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://simon-6.gitbook.io/simoncyber/ctf-writeups/picoctf-2024/forensics/mob-psycho-medium.md).
# Mob psycho (Medium)
This is my first APK challenge, hence I'll do a little of bit research before the challenge.
***
### What is a APK
{% embed url="" %}
"An **APK file,** or **Android Package Kit**, is a type of file format used to distribute and install applications on the [**Android** ](https://www.geeksforgeeks.org/android/android-tutorial/)**operating system.** It's like the same thing as downloading files as exe on windows, except for files you download lets say from the app store would be APK files.
The two most commonly associated tools associated with APK ctfs is JADX and apktool.
```
sudo apt install jadx
sudo apt install apktool
```
> More or less, "Use **JADX** and **APKTool** together, **JADX** for readable code, **APKTool** for precise resource mapping."
There's 7 main compendents of a APK file. I'll go through them quickly.
1. AndriodManifest.xml: The identity card, contains the apps settings and permissions
2. classes.dex: Contains the code of the program
3. resources.arsc: Contains all the resources shown on the screen (Like CSS)
4. res/: Uncomplied resources of the app
5. META-INF/: Contains security information and certificates
6. lib/: Contains the libraries
7. assets/: Contains the files, like images, sounds, fonts
***
### Solving it
The hint says to unzip it so the first thing to is that.
```
unzip mobpsycho.apk
```
Once we unzip it, we get a lot of files to sort through.
Sorting through this manually isn't efficient, let's use grep!
```
strings mobphysco.apk | grep -i flag
```
After this we could just do "cat ./res/color/flag.txt to get a hex version of the flag.