Methods to Reverse Engineer a Unity Recreation

On this tutorial you’ll use ILSpy and AssetStudio to extract code and property from a compiled Unity sport.

Within the context of software program, reverse engineering is the apply of analyzing a system to extract design and implementation info. That is usually used to higher perceive how software program features. One methodology of reverse engineering is decompiling, which performs the alternative operations of a compiler to transform executable applications again into human-readable code.

You possibly can decompile Unity video games utilizing specialised instruments to extract the code and most property. Listed below are some frequent use instances the place this may be helpful:

• Recuperate the misplaced code and property of a sport you made.
• Check out the supply code or 3D fashions of a sport to review and be taught from.
• Mod a sport by changing property with your personal.

Word: With nice energy comes nice accountability. The reverse engineering methods described on this tutorial are supposed for authorized use instances like recovering initiatives you made your self or for academic use. Stealing code and property and claiming them as your personal is prohibited and I’m not answerable for any authorized penalties.

On this tutorial, you’ll use ILSpy and AssetStudio to decompile a Unity sport on Home windows. Alongside the best way, you’ll learn to:

• Use ILSpy to decompile a sport’s code
• Save the code to your laptop
• Examine property utilizing AssetStudio
• Extract audio and 3D fashions from a sport

Whereas I’ll be protecting Home windows functions on this tutorial, there are alternate options for Linux and macOS on the market with the identical performance like AvaloniaILSpy and UnityPy. I’ve additionally added some extra software program concerns on the backside of the tutorial, a few of that are cross-platform.

Getting Began

Click on the Obtain Supplies button on the prime or backside of this web page to obtain the pattern sport, Avoiding Duty. Extract the zip file to a folder to be used in a while. If you’d like, you possibly can play the sport on Home windows by operating Avoiding Duty.exe. You possibly can give up the sport by urgent Escape or Alt + F4.

Granted, there’s not a lot happening aside from some purple “accountability” crystals falling down from above whereas a cheery tune performs within the background. It gained’t be the sport of the 12 months anytime quickly, however that’s not the main focus of this tutorial. Within the following sections, you’ll choose this sport aside to entry its supply code and property.

Instrument necessities

On to the instruments! Each ILSpy and AssetStudio want the .NET 6 SDK to work. To examine if you have already got this SDK put in, open a Command Immediate by opening the Begin menu, getting into “cmd” and urgent Enter. With the Command Immediate open, enter the next command and press Enter to execute it:

dotnet --list-sdks

When you have .NET 6 SDK put in, there needs to be a 6.X.X entry within the listing:

If there’s no 6.X.X entry, otherwise you get an “dotnet isn’t acknowledged” error, you’ll want to put in the newest model of the SDK from right here: https://dotnet.microsoft.com/en-us/obtain/dotnet/6.0
Select the installer model that matches your CPU’s structure and obtain it. In most trendy programs, this will likely be x64:

Now set up the SDK and re-run the dotnet --list-sdks command in a Command Immediate to confirm it’s put in.

Downloading ILSpy and AssetStudio

With the necessities out of the best way, head over to the releases web page of ILSpy: https://github.com/icsharpcode/ILSpy/releases

Click on on the Belongings button on the backside of the changelog of the newest launch and click on on the ILSpy_selfcontained_x64 zip to obtain it.

As soon as the obtain finishes, extract the zip to a folder to be used within the subsequent part.

Subsequent up is AssetStudio, the obtain course of right here is just like IlSpy. To begin off, head over to the releases web page: https://github.com/Perfare/AssetStudio/releases

Click on the Belongings button if the property aren’t seen immediately and click on on the .net6 hyperlink to obtain the .NET 6 model of AssetStudio.

Extract the contents of the zip to a folder for later use.

Extracting Supply Code

To extract the code from the pattern sport, you’ll want to make use of ILSpy, which is a an open-source .NET meeting browser and decompiler. Unity video games use C# for his or her scripts, which get compiled to Intermediate Language, or IL for brief. IL is a decrease degree language than C#, however nonetheless larger degree than machine code. Right here’s what IL code seems like:

.methodology public hidebysig static void Essential() il managed
{
    .entrypoint
    // Code dimension    11 (0xb)
    .maxstack 8
    IL_0000:         ldstr     "Hiya, World"
    IL_0005:    name void [mscorlib]System.Console::WriteLine
                         (class System.String)
} // finish of methodology HelloWorld::Essential

By default, Unity compiles all scripts collectively right into a single file named Meeting-CSharp.dll. As a Unity developer, you possibly can select to group scripts in further meeting definitions recordsdata, which can generate additional meeting recordsdata when you compile your sport. ILSpy can learn the IL code in these recordsdata and convert them again to C# courses.

Time to check out what IlSpy provides! Open the ILSpy folder and double click on on ILSpy.exe to begin ILSpy. In case your necessities are so as, that is what you’ll see as soon as the applying hundreds:

Exploring ILSpy

The interface is cut up up into two major sections: an inventory of loaded assemblies on the left and the decompiled C# code on the suitable. ILSpy has some generally used .NET assemblies loaded by default like mscorelib and System.

To load the pattern sport’s CSharp meeting, click on on the folder icon within the menu bar or press CTRL + O in your keyboard to open a folder browser window.

Navigate to the Avoiding Duty folder you unzipped earlier, there needs to be a file named Avoiding Duty.exe in there. From there, navigate to the Information folder, named Avoiding Responsibility_Data on this case and open the Managed folder in there. In brief: Recreation folder / Information / Managed.

You must see an inventory of DLL recordsdata in there.

Double-click Meeting-CSharp.dll to load the meeting in ILSpy. If all went properly, a brand new entry was added within the Assemblies listing on the left named Meeting-CSharp.

To examine the meeting, click on on the little + button on the left of the entry to broaden the meeting. This unveils the next gadgets:

• Metadata: This comprises info on the meeting, together with its headers and strings.
• References: A listing of different assemblies this meeting references. ILSpy will robotically load in these assemblies if you’re inspecting code that references them, so don’t be shocked if the Assemblies listing will get crammed up with extra assemblies.
• A “-” namespace: The pattern sport doesn’t use namespaces in its code, however different initiatives can have an inventory right here of the completely different namespaces used. That is the place the supply code lives.

Develop the - namespace to get your first glimpse of one thing acquainted — an inventory of courses! Subsequent, click on on the Rotate class and also you’ll see the supply code being proven on the suitable.

You might have to click on the + buttons within the code to broaden the strategies, however it’s all proper there:

Exporting Code

It can save you the code by copy-pasting it right into a file, or by right-clicking the category within the Assemblies listing and deciding on Save Code… within the menu. Now you can select a location to avoid wasting the C# file to. Don’t fear, you’re free to repeat my superb code and use it to your personal. :]

In massive assemblies, having to examine and save the courses individually can get tedious, so I’ll introduce you to a extra environment friendly approach of saving the code. Proper-click on Meeting-CSharp and select Save Code… within the menu. This can immediate you to decide on a location to avoid wasting the C# venture file to. It’d look like you’re saving a single file right here, however ILSpy will really copy over all courses it might probably discover as C# recordsdata, together with a venture file.

Typically, ILSpy does a fairly good job of decompiling the code, however you might run into some bizarre code right here and there if the decompiler wasn’t positive what to do. For example, when you check out the BrokenResponsibility class, it has a DestroySelf methodology which differs from the unique code. The decompiled model seems like this:

personal void DestroySelf()
{
  Object.Destroy(base.gameObject);
}

Whereas the unique code was the next:

personal void DestroySelf()
{
  Destroy(gameObject);
}

Word the Object class and base key phrase that had been added to the strategy name. The decompiled code remains to be legitimate, however you would possibly need to contemplate cleansing it up a bit when utilizing it in your personal initiatives.

That concludes using ILSpy! It’s a strong device to bear in mind when it’s worthwhile to extract the supply code from Unity video games and different .NET based mostly merchandise. It has saved me a number of occasions already once I misplaced my initiatives as a consequence of knowledge corruption. Backups are higher in each approach, however it is a good backup. Simply keep in mind to be good and use it for good solely.

Now you know the way to examine and save supply code, it’s time to maneuver on to extracting the property.

Extracting Belongings

AssetStudio is an open-source device that may examine and extract the next asset sorts from Unity 3.4 to 2022.1:

• Textures and sprites
• Audio
• Fonts
• Meshes
• Textual content
• Shaders
• Video recordsdata
• Animations

It does this by reverse engineering the packed codecs and changing these again into usable codecs. A texture for instance might be transformed into png, tga, jpeg or bmp.

Open AssetStudio by opening the folder you extracted within the Getting Began part and double-click AssetStudioGUI.exe. After a short time, you’ll be greeted by its person interface:

Tour of AssetStudio

Like ILSpy, AssetStudio has two major sections: a file browser on the left and a preview on the suitable. Not like ILSpy nevertheless, there’s nothing to see right here till you open an property file or a folder of a compiled sport.
Earlier than delving deeper within the utility, disable all error messages as on the time of writing AssetStudio has some points with loading in shaders, leading to a ton of errors being generated. To disregard these, choose Debug within the toolbar and uncheck Present error message.

Now load within the property by deciding on File ▸ Load folder within the toolbar to open a folder browser window.

Navigate to the Avoiding Duty folder, you realize you’re on the proper place when you see the Avoiding Responsibility_Data folder:

Choose this folder to load it. AssetStudio will now search all subfolders for any asset recordsdata and skim their contents. This could take fairly some time relying on the quantity of property and their kind. So long as the progress bar on the backside is shifting and the textual content discipline under the preview reads “Learn property…” you need to be good. It took my system about two minutes earlier than the applying was lastly executed loading.

As soon as the property are loaded, you must see an inventory of scenes and prefabs showing within the Scene Hierarchy tab:

You possibly can broaden these to get a tough thought of what kind of GameObjects make up the scene, however other than that it’s not that helpful.

Exporting Belongings

Open the Asset Checklist tab, as that’s the place the enjoyable begins. In right here, you’ll find all property supported by AssetStudio which are a part of the pattern sport. Most of those are included by Unity, however some had been added by me when creating the sport.

The listing might be filtered by identify if you realize what to search for by utilizing the textbox under the tabs. For instance, kind in “Entertainer” and wait a short time, the listing will shrink right down to a single AudioClip of the background music.

Preview the file by clicking on its identify within the Asset Checklist and urgent the Play button within the Preview window on the suitable.

Click on on the Cease button when you’re executed having fun with the tune. It can save you this asset by right-clicking its identify and deciding on Export chosen property within the menu. This can immediate you to decide on a folder to reserve it to.

Word: The music is “The Entertainer” by Kevin MacLeod (incompetech.com). It’s licensed underneath the Artistic Commons: By Attribution 4.0 License.

AssetStudio will create a folder based mostly on the kind of asset, AudioClip on this case. Inside you’ll discover the audio file in WAV format.

Filter the filter by deciding on the textual content you’ve added and hitting Backspace or Delete in your keyboard. There’s one other technique to filter property: by their kind.

Choose Filter Kind ▸ Mesh within the toolbar to solely present 3D fashions within the listing. The fashions used within the pattern sport all have the identical identify: default. You possibly can choose them one after the other to get a pleasant preview.

Now choose all default meshes, right-click on any of them and choose Export chosen Belongings within the menu. Choose a folder to avoid wasting the fashions to within the folder browser window like earlier than.

As soon as the fashions are exported, they’re all in OBJ format. You should use an utility like Blender to import these recordsdata, edit them and export to a format of your selecting. You may as well use them as-is, as most sport engines assist OBJ meshes.

Right here’s the default.obj file opened up in Blender for example:

That’s it for AssetStudio, one other positive device to have in your arsenal.

The place to Go From Right here?

Congratulations on ending this tutorial! You now know tips on how to extract the supply code and property out of a compiled Unity sport. I sincerely hope these methods will show as helpful for you as they did for me.

You possibly can obtain the pattern sport utilizing the Obtain Supplies button on the prime or backside of this tutorial if you wish to mess around with it some extra.
If you wish to check out another instruments to reverse engineer Unity video games, listed below are my suggestions:

• dnSpyEx: Much like ILSpy, however it lets you debug and even edit assemblies
• IL2CppDumper: Extracts the supply code from video games that had been constructed with IL2CPP
• AssetRipper: A substitute for AssetStudio to extract property

Thanks for studying this tutorial to the tip! When you have any questions or feedback, be happy to affix the dialogue under.