Lead.Hook 1.0.0

Lead.Hook

A lightweight IL-rewriting hook engine for .NET 8+ and .NET 10 — no Harmony, no runtime patching, no native hooks.

How It Works

Lead.Hook rewrites IL instructions at assembly load time using Mono.Cecil. It scans target assemblies for specific IL patterns and replaces them with calls to your replacement methods — before the code ever executes.

Supported Hook Types

Quick Start

using Lead.Hook;

var engine = new HookBuilder()
    // CallSite: redirect method call
    .Hook("MyApp.TextPrinter", "GetText")
        .With(typeof(MyReplacement), "GetText")

    // MethodBody: replace entire method body (static class safe)
    .Hook("MyApp.SecretKeeper", "GetSecret", HookType.MethodBody)
        .With(typeof(SecretReplacement), "GetSecret")

    // NewObj: intercept constructor
    .Hook("MyApp.ConfigLoader", ".ctor", HookType.NewObj)
        .With(typeof(ConfigFactory), "Create")

    // FieldRead: intercept field access
    .Hook("MyApp.UserProfile", "Name", HookType.FieldRead)
        .With(typeof(FieldHooks), "GetName")

    .Build();

var result = engine.RewriteWithResult("TargetApp.dll");
// Load result.RewrittenAssembly via AssemblyLoadContext

Replacement Method Signatures

// CallSite (instance method): first param is 'this'
public static int Add(object self, int x) => 0;

// CallSite (static method): no 'this'
public static string GetText() => "replaced";

// MethodBody: same as CallSite
public static string GetSecret() => "replaced";

// NewObj: same params as constructor, returns replacement object
public static ConfigShadow Create(string env) => new("hacked-" + env);

// FieldRead (instance): receives 'this'
public static string GetName(object self) => "replaced";

// FieldRead (static): no params
public static string GetRole() => "admin";

// FieldWrite (instance): receives 'this' + value
public static void SetName(object self, string value) { }

// FieldWrite (static): receives value
public static void SetRole(string value) { }

// TypeCheck: receives object, returns object?
public static object? CheckType(object obj) => obj;

// Box: receives value type, returns object
public static object BoxInt(int value) => value;

// Unbox: receives object, returns value type
public static int UnboxInt(object value) => (int)value;

// FunctionPointer: returns IntPtr
public static IntPtr GetPtr() => IntPtr.Zero;

.NET 10 Compatibility

Lead.Hook targets net8.0 and is fully compatible with .NET 10 applications. No known breaking issues.

License

MIT