//////////////////////////////////////////////////////////////////////////
//	(c) Exception hook engine by sn0w. big thx to kez for good advices ;)
//	(c) cih.[ms] community, 2009
//////////////////////////////////////////////////////////////////////////

#include <windows.h>
#include "alldefs.h"

//////////////////////////////////////////////////////////////////////////
// анхук не поддерживается, пока. впадлу бля)
//////////////////////////////////////////////////////////////////////////

LIST_ENTRY   exception_list_head;

//////////////////////////////////////////////////////////////////////////

#define InitializeListHead(ListHead) (\
	(ListHead)->Flink = (ListHead)->Blink = (ListHead))

#define InsertHeadList(ListHead,Entry) {\
	PLIST_ENTRY _EX_Flink;\
	PLIST_ENTRY _EX_ListHead;\
	_EX_ListHead = (ListHead);\
	_EX_Flink = _EX_ListHead->Flink;\
	(Entry)->Flink = _EX_Flink;\
	(Entry)->Blink = _EX_ListHead;\
	_EX_Flink->Blink = (Entry);\
	_EX_ListHead->Flink = (Entry);\
}

//////////////////////////////////////////////////////////////////////////

PHOOK_ENTRY	find_hook_entry(LPVOID real_address)
{
	PLIST_ENTRY		current_list;
	PHOOK_ENTRY		pcurr_hook;

	current_list = exception_list_head.Flink;

	while(current_list != &exception_list_head){
		pcurr_hook = CONTAINING_RECORD(current_list, HOOK_ENTRY, list_entry);

		if ((DWORD)pcurr_hook->real_address == (DWORD)real_address)
			return pcurr_hook;
		
		current_list = current_list->Flink;
	}

	return NULL;
}

//////////////////////////////////////////////////////////////////////////

VOID (WINAPI * Real_KiUserExceptionDispatcher)(IN PEXCEPTION_RECORD ExceptionRecord, IN PCONTEXT ContextFrame);
VOID WINAPI My_KiUserExceptionDispatcher(IN PEXCEPTION_RECORD ExceptionRecord, IN PCONTEXT ContextFrame)
{

    if(ExceptionRecord->ExceptionCode == STATUS_PRIVILEGED_INSTRUCTION){
		PHOOK_ENTRY hhk;
		hhk = find_hook_entry(ExceptionRecord->ExceptionAddress);

		if(hhk){
			ContextFrame->Eip = (DWORD)hhk->handler;
			NtContinue(ContextFrame, FALSE);
		}

    }

    Real_KiUserExceptionDispatcher(ExceptionRecord,ContextFrame);
}

//////////////////////////////////////////////////////////////////////////

__declspec(naked) VOID WINAPI Stub_KiUserExceptionDispatcher(IN PEXCEPTION_RECORD ExceptionRecord,
															 IN PCONTEXT ContextFrame)
{
	__asm{
		sub	esp, 4
		jmp	My_KiUserExceptionDispatcher
	}
}

//////////////////////////////////////////////////////////////////////////

inline void generate_pushret_code(LPVOID at_address, LPVOID to_address)
{
	*(LPBYTE)at_address = 0x68;
	*(DWORD*)((LPBYTE)at_address + 1) = (DWORD)to_address;
	*((LPBYTE)at_address + 5) = 0xC3;
}

//////////////////////////////////////////////////////////////////////////

PHOOK_ENTRY	ExceptionHookFunction(LPVOID function, LPVOID handler)
{
	BYTE privileged_opcodes[] = {0xFA, 0xFB, 0xEE, 0xEF, 0xEC, 0x6C, 0x6F};
	
	LPVOID		trampoline;
	DWORD		first_inst_len, protection;
	PHOOK_ENTRY phhk;
		
	get_instruction_length(function, &first_inst_len);
	
	trampoline = valloc(first_inst_len + 6);
	memcpy(trampoline, function, first_inst_len);
	generate_pushret_code((LPVOID)((LPBYTE)trampoline + first_inst_len), (LPVOID)((LPBYTE)function + first_inst_len));
	
	phhk = (PHOOK_ENTRY)valloc(sizeof(HOOK_ENTRY));	
	phhk->handler = handler;
	phhk->real_address = function;
	phhk->trampoline = trampoline;

	InsertHeadList(&exception_list_head, &phhk->list_entry);
	
	VirtualProtect(function, first_inst_len, PAGE_EXECUTE_READWRITE, &protection);
	*(LPBYTE)function = privileged_opcodes[brandom(0, sizeof(privileged_opcodes) - 1)];
	VirtualProtect(function, first_inst_len, protection, &protection);

	return phhk;
}

//////////////////////////////////////////////////////////////////////////

void InitializeExceptionHook()
{
	InitializeListHead(&exception_list_head);

	SpliceHookFunction((DWORD)GetProcAddress(GetModuleHandle("ntdll.dll"), "KiUserExceptionDispatcher"),
			Stub_KiUserExceptionDispatcher, (DWORD*)&Real_KiUserExceptionDispatcher);

}

//////////////////////////////////////////////////////////////////////////