/// <summary>
/// Creates a hook for a function at a given address.
/// </summary>
/// <param name="function">The function to detour the original function to.</param>
/// <param name="functionAddress">The address of the function to hook.</param>
/// <param name="minHookLength">Optional explicit length of hook. Use only in rare cases where auto-length check overflows a jmp/call opcode.</param>
public Hook(TFunction function, long functionAddress, int minHookLength = -1)
{
_is64Bit = IntPtr.Size == 8;
ReverseWrapper = CreateReverseWrapper(function);
/*
* === Hook Summary ===
*
* A. Insert Absolute Jump to ReverseWrapper (Convention => CDECL Marshaller)
* A1. Backup original bytes and patch between start and end of JMP for (B).
*
* B. Setup Wrapper to call original function (CDECL => Convention Marshaller)
* B1. Take bytes backed up from A, and create stub function with those
* bytes and JMP to end of hook.
* B2. Assign OriginalFunction to that function stub.
*
* Note: For X64 the same principles apply, just replace CDECL with Microsoft calling convention.
*/
Mutex.MakeHookMutex.WaitOne();
/* Create Convention => CDECL Wrapper. */
List <byte> jumpOpcodes = Utilities.AssembleAbsoluteJump(ReverseWrapper.WrapperPointer, _is64Bit).ToList();
/* Calculate Hook Length (Unless Explicit) */
if (minHookLength == -1)
{
minHookLength = Utilities.GetHookLength((IntPtr)functionAddress, jumpOpcodes.Count, _is64Bit);
}
// Sometimes our hook can be larger than the amount of bytes taken by the jmp opcode.
// We need to fill the remaining bytes with NOPs.
Utilities.FillArrayUntilSize <byte>(jumpOpcodes, 0x90, minHookLength);
/* Get bytes from original function prologue and patch them. */
CurrentProcess.SafeReadRaw((IntPtr)functionAddress, out byte[] originalFunction, minHookLength);
var functionPatcher = new FunctionPatcher(_is64Bit);
var functionPatch = functionPatcher.Patch(originalFunction.ToList(), (IntPtr)functionAddress);
IntPtr hookEndAddress = (IntPtr)(functionAddress + minHookLength);
functionPatch.NewFunction.AddRange(Utilities.AssembleAbsoluteJump(hookEndAddress, _is64Bit));
/* Second wave of patching. */
var icedPatcher = new IcedPatcher(_is64Bit, functionPatch.NewFunction.ToArray(), (IntPtr)functionAddress);
/* Create Hook instance. */
OriginalFunctionAddress = icedPatcher.ToMemoryBuffer();
OriginalFunction = CreateWrapper((long)icedPatcher.ToMemoryBuffer(), out IntPtr originalFunctionWrapperAddress);
OriginalFunctionWrapperAddress = originalFunctionWrapperAddress;
_otherHookPatches = functionPatch.Patches;
_hookPatch = new Patch((IntPtr)functionAddress, jumpOpcodes.ToArray());
Mutex.MakeHookMutex.ReleaseMutex();
}
/// <summary>
/// Creates a hook for a function at a given address.
/// </summary>
/// <param name="functionAddress">The address of the function to hook.</param>
/// <param name="minHookLength">Optional explicit length of hook. Use only in rare cases where auto-length check overflows a jmp/call opcode.</param>
/// <param name="options">Options which control the hook generation procedure.</param>
private void CreateHook(nuint functionAddress, int minHookLength = -1, FunctionHookOptions options = null)
{
// Set options if not passed in.
if (options == null)
{
Misc.TryGetAttribute <TFunction, FunctionHookOptions>(out options);
options ??= new FunctionHookOptions();
}
/*
* === Hook Summary ===
*
* A. Insert Absolute Jump to ReverseWrapper (Convention => CDECL Marshaller)
* A1. Backup original bytes and patch between start and end of JMP for (B).
*
* B. Setup Wrapper to call original function (CDECL => Convention Marshaller)
* B1. Take bytes backed up from A, and create stub function with those
* bytes and JMP to end of hook.
* B2. Assign OriginalFunction to that function stub.
*
* Note: For X64 the same principles apply, just replace CDECL with Microsoft calling convention.
*/
/* Create Target Convention => TFunction Wrapper. */
var jumpOpcodes = options.PreferRelativeJump ?
Utilities.TryAssembleRelativeJump(functionAddress, ReverseWrapper.WrapperPointer.ToUnsigned(), _is64Bit, out _) :
Utilities.AssembleAbsoluteJump(ReverseWrapper.WrapperPointer.ToUnsigned(), _is64Bit).ToList();
/* Calculate Hook Length (Unless Explicit) */
if (minHookLength == -1)
{
minHookLength = Utilities.GetHookLength(functionAddress, jumpOpcodes.Count, _is64Bit);
}
// Sometimes our hook can be larger than the amount of bytes taken by the jmp opcode.
// We need to fill the remaining bytes with NOPs.
Utilities.FillArrayUntilSize <byte>(jumpOpcodes, 0x90, minHookLength);
/* Get bytes from original function prologue and patch them. */
CurrentProcess.SafeReadRaw(functionAddress, out byte[] originalFunction, minHookLength);
var functionPatcher = new FunctionPatcher(_is64Bit, options);
var functionPatch = functionPatcher.Patch(originalFunction.ToList(), functionAddress);
nuint hookEndAddress = functionAddress + (nuint)minHookLength;
/* Second wave of patching. */
var icedPatcher = new IcedPatcher(_is64Bit, functionPatch.NewFunction.ToArray(), functionAddress);
/* Create Hook instance. */
OriginalFunctionAddress = icedPatcher.ToMemoryBuffer(hookEndAddress).ToSigned();
OriginalFunction = CreateWrapper(icedPatcher.ToMemoryBuffer(null), out nuint originalFunctionWrapperAddress);
OriginalFunctionWrapperAddress = originalFunctionWrapperAddress.ToSigned();
_otherHookPatches = functionPatch.Patches;
_hookPatch = new Patch(functionAddress, jumpOpcodes.ToArray());
}