A payload and injector that enables easy .NET Core DLL injection.

A while ago, I was writing some injected C# code for the game FINAL FANTASY XIV. I ended up writing an injector and loader using dll-syringe and netcorehost, supporting the ability to unload itself. Later on, for another game, I wanted to reuse some its features and code, so I ended up writing it again a second time. ...then it came up a third time, and I questioned what I was doing with my life.

goalnet enables you to use C# in another process without having to think about the setup. Add a static method & delegate, write a config file, and then start the injector. No extra thought required.

Let's use the examples/hello-goalnet folder as an example. This project loads into Notepad, shows a message box, and unloads itself.

To demonstrate it in action, start Notepad, then build everything. goalnet-injector takes one argument, which is the path to the config file.

$ cargo build --release
$ dotnet build --configuration Release ./examples/hello-goalnet/HelloGoalnet
$ cargo run --release -p goalnet-injector -- ./examples/hello-goalnet/config.toml

Every project that uses goalnet requires a config file, along with some setup in the assembly itself. See the above example for all values in the config file.

In the project's .csproj, GenerateRuntimeConfigurationFiles must be set to true. This is required for goalnet, as it creates a .runtimeconfig.json (used to determine what .NET version to use).

The assembly must have a class with an entrypoint method, along with a delegate matching the method signature. The entrypoint method must be static, contain no arguments, and returns void.

When unload is set to true, the entrypoint method instead takes one argument, being an IntPtr/nint to the unload function. This can be casted into a delegate, which can be called to signal unloading the assembly from inside itself. This will only work as long as the injector process is still alive and communicating with the goalnet payload.

When copy_build_artifacts is set to true, the entire specified directory (along with the goalnet payload itself) is copied to a temporary directory. This is wasteful, but allows you to bypass file locking issues, meaning you can cleanly unload and reload the assembly without having to restart the target process.