DxWnd.reloaded/dll/iatpatch.cpp

#include <windows.h>
#include "dxwnd.h"
#include "dxwcore.hpp"

void *IATPatch(HMODULE module, char *dll, void *apiproc, const char *apiname, void *hookproc)
{
	PIMAGE_NT_HEADERS pnth;
	PIMAGE_IMPORT_DESCRIPTOR pidesc;
	DWORD base, rva;
	PSTR impmodule;
	PIMAGE_THUNK_DATA ptaddr;
	PIMAGE_THUNK_DATA ptname;
	PIMAGE_IMPORT_BY_NAME piname;
	DWORD oldprotect;
	void *org;

	base = (DWORD)module;
	org = 0; // by default, ret = 0 => API not found

	__try{
		pnth = PIMAGE_NT_HEADERS(PBYTE(base) + PIMAGE_DOS_HEADER(base)->e_lfanew);
		if(!pnth) {
			OutTraceH("IATPatch: ERROR no PNTH at %d\n", __LINE__);
			return 0;
		}
		rva = pnth->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress;
		if(!rva) {
			OutTraceH("IATPatch: ERROR no RVA at %d\n", __LINE__);
			return 0;
		}
		pidesc = (PIMAGE_IMPORT_DESCRIPTOR)(base + rva);

		while(pidesc->FirstThunk){
			impmodule = (PSTR)(base + pidesc->Name);
			if(!lstrcmpi(dll, impmodule)) {
				//OutTraceH("IATPatch: dll=%s found at %x\n", dll, impmodule);

				ptaddr = (PIMAGE_THUNK_DATA)(base + (DWORD)pidesc->FirstThunk);
				ptname = (pidesc->OriginalFirstThunk) ? (PIMAGE_THUNK_DATA)(base + (DWORD)pidesc->OriginalFirstThunk) : NULL;

				while(ptaddr->u1.Function){
					if (ptname){
						// examining by function name
						if(!IMAGE_SNAP_BY_ORDINAL(ptname->u1.Ordinal)){
							piname = (PIMAGE_IMPORT_BY_NAME)(base + (DWORD)ptname->u1.AddressOfData);
							if(!lstrcmpi(apiname, (char *)piname->Name)) break;
						}
					}
					if (apiproc){
						// examining by function addr
						if(ptaddr->u1.Function == (DWORD)apiproc) break;
					}
					ptaddr ++;
					if (ptname) ptname ++;
				}

				if(ptaddr->u1.Function) {
					org = (void *)ptaddr->u1.Function;
					if(org == hookproc) return 0; // already hooked
						
					if(!VirtualProtect(&ptaddr->u1.Function, 4, PAGE_EXECUTE_READWRITE, &oldprotect)) {
						OutTraceDW("IATPatch: VirtualProtect error %d at %d\n", GetLastError(), __LINE__);
						return 0;
					}
					ptaddr->u1.Function = (DWORD)hookproc;
					if(!VirtualProtect(&ptaddr->u1.Function, 4, oldprotect, &oldprotect)) {
						OutTraceDW("IATPatch: VirtualProtect error %d at %d\n", GetLastError(), __LINE__);
						return 0;
					}
					if (!FlushInstructionCache(GetCurrentProcess(), &ptaddr->u1.Function, 4)) {
						OutTraceDW("IATPatch: FlushInstructionCache error %d at %d\n", GetLastError(), __LINE__);
						return 0;
					}
					OutTraceH("IATPatch hook=%s address=%x->%x\n", apiname, org, hookproc);

					return org;
				}
			}
			pidesc ++;
		}
		if(!pidesc->FirstThunk) {
			OutTraceH("IATPatch: PE unreferenced function %s:%s\n", dll, apiname);
			return 0;
		}
	}
	__except(EXCEPTION_EXECUTE_HANDLER)
	{       
		OutTraceDW("IATPatch: EXCEPTION hook=%s:%s Hook Failed.\n", dll, apiname);
	}
	return org;
}