Snorlax - Payatu Hiring CTF Writeup

Challenge Info

Field	Details
CTF	Payatu Hiring CTF
Challenge	Snorlax
Category	Android / Reverse Engineering

Solution

We can install the APK in our emulator,But when we try to open it

We cannot enter the APP, it is doing somekind of checking - probably root/emulator detection which is not allowing us to open the app. We can inspect it in Jadx to get more idea

There isn’t much in Main Activity, we just need to open the app and click on the image to get the flag which is loaded from a native lib If we check the lib folder we see,

There are two native libs

1. libnative-lib.so –> from where the flag is loaded
2. libtoolcheck.so –> the root detector

We can further inspect libtoolcheck.so to get more idea about it

It is indeed a root check which checks if a particular root binaries are present or not for root detection We just need to bypass this to get the flag I used a Frida root detection bypass script from github And loaded this bypass script, to get the flag

Flag

FLAG:PAYATU{SN0RL3X15BL0CKNGXYZUIQP13J4}