Arno

Author: 0xIDA
Platform: FlagYard · Category: mobile · Difficulty: N/A

Solvers

• recon.sh

Summary

Unity IL2CPP Android game reverse engineering challenge from FlagYard. The APK com.Z4ki.Arno is a Unity-based Android game with native IL2CPP code.

Structure

• Category: Mobile Reverse Engineering
• Challenge Name: Arno
• Path: ctf/flagyard/mobile/arno/
• Target: Extract the flag from the Unity game binary

Analysis Performed

• APKTool unpack — extracted smali, AndroidManifest, resources
• DEX extraction — classes.dex + classes2.dex
• Java decompilation — minimal Java code (only R.java in com.Z4ki)
• Native library extraction — libil2cpp.so, libgame.so, libunity.so (arm64-v8a)

Key Observations

• Package: com.Z4ki.Arno
• Unity IL2CPP build — main game logic in libil2cpp.so
• No flag text found in plain strings yet
• Kotlin support libraries present (AndroidX, Kotlin stdlib)

Next Steps

1. Run Il2CppDumper to recover method signatures from libil2cpp.so
2. Analyze global-metadata.dat for Unity metadata
3. Decompile with Ghidra / IDA focused on the IL2CPP code
4. Check Unity assets (AssetRipper) for embedded data
5. Consider dynamic analysis with Frida

Files

File	Size	Purpose
Arno.apk	34 MB	Original APK
extracted/dex/classes.dex	—	Main DEX
extracted/dex/classes2.dex	—	Secondary DEX
extracted/native/arm64-v8a/libil2cpp.so	—	IL2CPP native
extracted/native/arm64-v8a/libgame.so	—	Game native code

Status

Pending — Challenge not yet solved. Analysis is in initial recon phase.