NOTE: Il2CppInspector is not a decompiler. It can provide you with the structure of an application and function addresses for every method so that you can easily jump straight to methods of interest in your disassembler. It does not attempt to recover the entire source code of the application.

File format and architecture support:

Supports ELF (Android .so), PE (Windows .exe), Mach-O (Apple iOS/Mac), Universal Binary (Fat Mach-O) and FSELF (PlayStation 4 .prx/.sprx) file formats
Also supports APK (Android) and decrypted IPA (iOS) application package files as input
32-bit and 64-bit support for all file formats
Supports ARMv7, Thumb-2, ARMv8 (A64), x86 and x64 architectures regardless of file format
Supports applications created with Unity 5.3.0 onwards (full IL2CPP version table below)

Nice to have:

Support for assemblies, classes, methods, constructors, fields, properties, enumerations, events, interfaces, structs, pointers, references, attributes, nested types, generic types, generic methods, generic constraints, default field values and default method parameter values
C# syntactic sugar for CTS value types, compiler-generated types, delegates, extension methods, operator overloading, indexers, user-defined conversion operators, explicit interface instantiations, finalizers, nullable types, unsafe contexts, fixed-size arrays, variable length argument lists, method hiding and escaped strings
Partition C# code output by namespace, assembly, class, full tree or single file; sort by index or type name; output flat or nested folder hierarchy. Each file includes the necessary using directives. Scope and type name conflicts are resolved automatically to produce code that compiles.
Static and dynamic symbol table scanning and relocation processing for ELF binaries
Static symbol table scanning for Mach-O binaries
Automatically defeats certain basic obfuscation methods

Reusable class library APIs:

Il2CppInspector - low-level access to the binary image and metadata
TypeModel - high-level .NET Reflection-like query API for all of the .NET types in the source project as a tree model
ApplicationModel - access to all of the C++ types and methods, plus the IL2CPP API exports, with detailed address and offset data and mappings to their .NET equivalents

Use these APIs to easily query IL2CPP types, create new output modules and integrate Il2CppInspector with your own static analysis applications.
Test chassis for automated integration testing of IL2CPP binaries

Class library targets .NET Standard 2.1. Application targets .NET Core 3.0. Built with Visual Studio 2019.

Build instructions

git clone --recursive https://github.com/djkaty/Il2CppInspector
cd Il2CppInspector
dotnet publish -c Release

This will build Il2CppInspector for Windows 64-bit. For MacOS and Linux, add -r xxx to the final command where xxx is a RID from https://docs.microsoft.com/en-us/dotnet/articles/core/rid-catalog

The output binary for command-line usage is placed in Il2CppInspector/Il2CppInspector.CLI/bin/Release/netcoreapp3.0/win-x64/publish/Il2CppInspector.exe.

The output binary for Windows GUI is places in Il2CppInspector/Il2CppInspector.GUI/bin/Release/netcoreapp3.1/win-x64/publish/Il2CppInspector.exe.

Command-line Usage

Run Il2CppInspector.exe at the command prompt.

File format and architecture are automatically detected.

  -i, --bin                   (Default: libil2cpp.so) IL2CPP binary, APK or IPA input file
  -m, --metadata              (Default: global-metadata.dat) IL2CPP metadata file input (ignored for APK/IPA)
  -c, --cs-out                (Default: types.cs) C# output file (when using single-file layout) or path (when using per namespace, assembly or class layout)
  -p, --py-out                (Default: ida.py) IDA Python script output file
  -h, --cpp-out               (Default: il2cpp-types.h) C++ header output file
  -e, --exclude-namespaces    (Default: System Mono Microsoft.Reflection Microsoft.Win32 Internal.Runtime Unity UnityEditor UnityEngine UnityEngineInternal AOT JetBrains.Annotations) Comma-separated list of
                              namespaces to suppress in C# output, or 'none' to include all namespaces
  -l, --layout                (Default: single) Partitioning of C# output ('single' = single file, 'namespace' = one file per namespace in folders, 'assembly' = one file per assembly, 'class' = one file per
                              class in namespace folders, 'tree' = one file per class in assembly and namespace folders)
  -s, --sort                  (Default: index) Sort order of type definitions in C# output ('index' = by type definition index, 'name' = by type name). No effect when using file-per-class or tree layout
  -f, --flatten               Flatten the namespace hierarchy into a single folder rather than using per-namespace subfolders. Only used when layout is per-namespace or per-class. Ignored for tree layout
  -n, --suppress-metadata     Diff tidying: suppress method pointers, field offsets and type indices from C# output. Useful for comparing two versions of a binary for changes with a diff tool
  -k, --must-compile          Compilation tidying: try really hard to make code that compiles. Suppress generation of code for items with CompilerGenerated attribute. Comment out attributes without
                              parameterless constructors or all-optional constructor arguments. Don't emit add/remove/raise on events. Specify AttributeTargets.All on classes with AttributeUsage attribute.
                              Force auto-properties to have get accessors. Force regular properties to have bodies. Suppress global::Locale classes. Generate dummy parameterless base constructors and ref
                              return fields.
  --separate-attributes       Place assembly-level attributes in their own AssemblyInfo.cs files. Only used when layout is per-assembly or tree
  -j, --project               Create a Visual Studio solution and projects. Implies --layout tree, --must-compile and --separate-attributes
  --cpp-compiler              (Default: BinaryFormat) Compiler to make C++ output compatible with (MSVC or GCC); selects based on binary executable type by default
  --unity-path                (Default: C:\Program Files\Unity\Hub\Editor\*) Path to Unity editor (when using --project). Wildcards select last matching folder in alphanumeric order
  --unity-assemblies          (Default: C:\Program Files\Unity\Hub\Editor\*\Editor\Data\Resources\PackageManager\ProjectTemplates\libcache\com.unity.template.3d-*\ScriptAssemblies) Path to Unity script
                              assemblies (when using --project). Wildcards select last matching folder in alphanumeric order
  --unity-version             Version of Unity used to create the input files, if known. Used to enhance IDAPython and C++ output. If not specified, a close match will be inferred automatically.
  --help                      Display this help screen.
  --version                   Display version information.

For Apple Universal Binaries, multiple output files will be generated, with each filename besides the first suffixed by the index of the image in the Universal Binary. Unsupported images will be skipped.

For IPA packages, the executable must be decrypted first. Encrypted executable binaries are not supported.

Creating C# prototypes

To exclude types from certain namespaces from being generated in the C# source file output, provide a comma-separated list of case-sensitive namespaces in --exclude-namespaces. The following namespaces will be excluded if no argument is specified:

System
Mono
Microsoft.Reflection
Microsoft.Win32
Internal.Runtime
Unity
UnityEditor
UnityEngine
UnityEngineInternal
AOT
JetBrains.Annotations

Providing an argument to --exclude-namespaces will override the default list. To output all namespaces, use --exclude-namespaces=none. This only applies to C# prototypes output.

Adding metadata to your IDA workflow

Simply run Il2CppInspector with the -p switch to choose the IDA script output file. Load your binary file into IDA, press Alt+F7 and select the generated script. Observe the Output Window while IDA analyzes the file - this may take a long time.

If you know which version of Unity the binary was compiled with, you can improve the output by specifying this with --unity-version, for example --unity-version 2019.3.1f1. Otherwise Il2CppInspector will make an educated guess based on the contents of the binary.

Il2CppInspector generates the following data for IDA projects:

Type declarations for all IL2CPP internal types
Type declarations for every type in the IL2CPP application including generic instances
Addresses for every known type
Names for all regular .NET methods
Names for all constructed generic methods
Names for all IL2CPP custom attributes generator functions
Names, .NET argument type lists and C++ signatures for all IL2CPP runtime invoker functions for both regular and constructed generic methods (per-signature Method.Invoke endpoints)
Function boundaries for all of the above
Comments at each function entry point with .NET method signatures for all of the above
Names and type declarations for all of the following IL metadata references: Type, TypeInfo, MethodDef, FieldInfo, StringLiteral, MethodRef (this includes all generic class and method instantiation metadata)
Comments for all IL string literal metadata pointers containing the value of the string
Names for some IL2CPP-specific data structures and functions

Example IDA C++ decompilation after applying Il2CppInspector (initialization code omitted for brevity):

Creating C++ scaffolding

Il2CppInspector generates C++ headers containing:

Type declarations for all internal IL2CPP types
Type declarations for every type used in the application including all enums, concrete generic type instances and inferred usages from metadata.
Boxed versions for types where applicable
VTables for every type

You can use these files with a tool like x64dbg to analyze the memory of the application, or for accessing types via DLL injection, among other uses.

You can target which C++ compiler you wish to use the output files with: specify --cpp-compiler MSVC for Visual Studio and --cpp-compiler GCC for gcc. Clang is compatible with either option.

Il2CppInspector performs automatic name conflict resolution to avoid the use of pre-defined symbols and keywords in C++, and to handle re-definition of same-named symbols in the application.

Creating a Visual Studio solution

Il2CppInspector can create a complete Visual Studio workspace with a solution (.sln) file, project (.csproj) files and assembly-namespace-class tree-like folder structure. Each project creates a single assembly.

Use the --project flag to generate a solution workspace.

In order for Il2CppInspector to be able to create .csproj files which contain the correct Unity assembly references, you must provide the path to an installed Unity editor and a project template or ScriptAssemblies folder of an existing Unity project.

NOTE: The default settings will select the latest installed version of Unity and the latest installed version of the default 3D project template, if they have been installed in the default location.

Typical Unity editor location (specified with --unity-path): C:\Program Files\Unity\Hub\Editor\20xx.y.z

Typical Unity project template location (specified with --unity-assemblies): C:\Program Files\Unity\Hub\Editor\20xx.y.z\Editor\Data\Resources\PackageManager\ProjectTemplates\libcache\<name-of-template>

Typical Unity script assemblies location in existing project (specified with --unity-aseemblies): X:\MyProject\Library\ScriptAssemblies

Replace x, y and z with your Unity version number. Replace <name-of-template> with the desired template.

NOTE: You can use the asterisk wildcard (*) one or more times when specifying these paths. Il2CppInspector will select the last matching folder in alphanumeric order. This is useful if you have multiple side-by-side Unity installs and wish to always select the latest version or template.

In the event that the assembly references are not correctly resolved the first time you load a solution, simply close and re-open the solution to force them to be resolved.

Generating IL2CPP binaries without a Unity project

Two Powershell scripts are provided to enable easy testing and debugging:

generate-binaries.ps1 compiles every C# source file in TestSources as a separate assembly and outputs them to TestAssemblies. It then takes every assembly in TestAssemblies and compiles each one as a separate IL2CPP project for each of these architectures: Windows x86 standalone, Windows x64 standalone, Android ARMv7 (32-bit) and Android ARMv8-A (64-bit). These are placed into the TestBinariesfolder. It then calls generate-tests.ps1.
generate-tests.ps1 generates a file called Tests.cs in the Il2CppTests project, containing one test per IL2CPP project in TestBinaries. This file will be compiled by the Il2CppTestsproject. You will then be able to see one test per IL2CPP project in Visual Studio's Test Explorer.

The auto-generated tests generate a file in the test IL2CPP binary's folder called test-result.cs and compares it (whitespace-insensitive) with the corresponding project name cs file in TestExpectedResults. In this way, you can check for files with known structure that the analysis is being performed correctly, or step through the analysis of specific binaries in the debugger without having to change the project's command-line arguments.

To learn more about this feature, see the section entitled Using Il2CppInspector to generate IL2CPP code in IL2CPP Reverse Engineering Part 1.

Using the APIs for programmatic analysis

To utilize Il2CppInspector in your own projects, add a reference to Il2CppInspector.Common.dll.

Include the following using directives:

using Il2CppInspector to use Il2CppInspector.
using Il2CppInspector.Reflection to use TypeModel.
using Il2CppInspector.Model to use ApplicationModel.

See the source code for further details.

Version support

Unity version	IL2CPP version	Support
4.6.1+	First release	Unsupported
5.2.x	15	Unsupported
5.3.0-5.3.1	16	Working
5.3.2	19	Working
5.3.3-5.3.4	20	Working
5.3.5-5.4.x	21	Working
5.5.x	22	Working
5.6.x	23	Working
2017.1.x-2018.2.x	24.0	Working
2018.3.x-2018.4.x	24.1	Working
2019.1.x-2019.3.6	24.2	Working
2019.3.7-2019.4.x	24.3	Working
2020.1	24.?	Awaiting stable release

Please refer to the separate repository https://github.com/nneonneo/Il2CppVersions if you would like to track the changes between each IL2CPP release version.

Problems

If you have files that don't work or are in an unsupported format, please open a new issue on GitHub and attach a sample with details on the file format, and I'll try to add support. Include both the IL2CPP binary and global-metadata.dat in your submission.

Please check the binary file in a disassembler to ensure that it is a plain IL2CPP binary before filing an issue. Il2CppInspector is not intended to handle packed, encrypted or obfuscated IL2CPP files.

Support

If you found Il2CppInspector useful, you can really help support the project by making a small donation at http://paypal.me/djkaty!

You can also donate with bitcoin: 3FoRUqUXgYj8NY8sMQfhX6vv9LqR3e2kzz

Much love! - Katy

Acknowledgements

Thanks to the following major contributors!

nneonneo - https://github.com/nneonneo (huge overhaul of generics and script generation)
carterbush - https://github.com/carterbush (IDA script generation)

Thanks to the following individuals whose code and research helped me develop this tool:

Perfare - https://github.com/Perfare/Il2CppDumper
Jumboperson - https://github.com/Jumboperson/Il2CppDumper
nevermoe - https://github.com/nevermoe/unity_metadata_loader
branw - https://github.com/branw/pogo-proto-dumper
fry - https://github.com/fry/d3
ARMConverter - http://armconverter.com
Defuse - https://defuse.ca/online-x86-assembler.htm
Jackson Dunstan has an awesome series of articles on IL2CPP - https://jacksondunstan.com/articles/tag/il2cpp
Josh Grunzweig's IDAPython primer series - https://unit42.paloaltonetworks.com/using-idapython-to-make-your-life-easier-part-1/

The following books and documents were also very helpful:

Practical Reverse Engineering by Bruce Dang
Expert .NET 2.0 IL Assembler by Serge Lidin
The IDA Pro Book, 2nd Edition by Chris Eagle
The Beginner's Guide to IDAPython by Alexander Hanel
ARM Architecture Reference Manual ARMv8-A
Intel 64 and IA-32 Architectures Software Developer's Manual

Pizza spinner animation in the GUI made by Chris Gannon - https://gannon.tv/

License

This software is licensed under AGPLv3.

Languages

C# 70.4%

C 28.6%

Svelte 0.4%

Python 0.3%

TypeScript 0.2%

Other 0.1%