模拟PE加载器加载PE文件，对导入表以及重定位表的操作过程。
PE加载器的步骤：
1.将PE文件用ReadFile读取数据
char szFileName[] = "1.exe";
//打开文件,设置属性可读可写
HANDLE hFile = CreateFileA(szFileName,
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_ARCHIVE,
NULL);
if (INVALID_HANDLE_VALUE == hFile)
{
printf("文件打开失败\n");
return 1;
}
//获取文件大小
DWORD dwFileSize = GetFileSize(hFile, NULL);
//申请空间将exe读取到内存中
char *pData = new char[dwFileSize];
if (NULL == pData)
{
printf("空间申请失败\n");
return 2;
}
DWORD dwRet = 0;
ReadFile(hFile, pData, dwFileSize, &dwRet, NULL);
CloseHandle(hFile);
2.根据PE结构获取镜像大小，在自己的程序中申请可读可写可执行的内存。
char* chBaseAddress = NULL;
//获取镜像大小
DWORD dwSizeOfImage = GetSizeOfImage(pFileBuff);
//在进程中开辟一块内存空间
chBaseAddress = (char*)VirtualAlloc(NULL,
dwSizeOfImage,
MEM_COMMIT | MEM_RESERVE,
PAGE_EXECUTE_READWRITE);
if (NULL == chBaseAddress)
{
printf("申请进程空间失败\n");
return NULL;
}
3.将申请的空间全部填为0
RtlZeroMemory(chBaseAddress, dwSizeOfImage);
4.将用ReadFile读取的数据映射到内存中
由上图可知，PE文件在加载到内存中对齐粒度不同，因此在写代码时要注意这个问题
PIMAGE_DOS_HEADER pDos = (PIMAGE_DOS_HEADER)pFileBuff;
PIMAGE_NT_HEADERS pNt = (PIMAGE_NT_HEADERS)(pFileBuff + pDos->e_lfanew);
PIMAGE_SECTION_HEADER pSection = IMAGE_FIRST_SECTION(pNt);
//所有头 + 结表头的大小
DWORD dwSizeOfHeaders = pNt->OptionalHeader.SizeOfHeaders;
//获取区段数量
int nNumerOfSections = pNt->FileHeader.NumberOfSections;
// 将前一部分都拷贝过去
RtlCopyMemory(chBaseAddress, pFileBuff, dwSizeOfHeaders);
char* chSrcMem = NULL;
char* chDestMem = NULL;
DWORD dwSizeOfRawData = 0;
for (int i = 0; i < nNumerOfSections; i++)
{
if ((0 == pSection->VirtualAddress) ||
(0 == pSection->SizeOfRawData))
{
pSection++;
continue;
}
chSrcMem = (char*)((DWORD)pFileBuff + pSection->PointerToRawData);
chDestMem = (char*)((DWORD)chBaseAddress + pSection->VirtualAddress);
dwSizeOfRawData = pSection->SizeOfRawData;
RtlCopyMemory(chDestMem, chSrcMem, dwSizeOfRawData);
pSection++;
}
return TRUE;
5.修复重定位
重定位后的地址 = 需要重定位的地址 - 默认加载基址 + 当前加载基址
PIMAGE_DOS_HEADER pDos = (PIMAGE_DOS_HEADER)chBaseAddress;
PIMAGE_NT_HEADERS pNt = (PIMAGE_NT_HEADERS)(chBaseAddress + pDos->e_lfanew);
PIMAGE_BASE_RELOCATION pLoc = (PIMAGE_BASE_RELOCATION)(chBaseAddress + pNt->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress);
//判断是否有重定位表
if ((char*)pLoc == (char*)pDos)
{
return TRUE;
}
while ((pLoc->VirtualAddress + pLoc->SizeOfBlock) != 0) //开始扫描重定位表
{
WORD *pLocData = (WORD *)((PBYTE)pLoc + sizeof(IMAGE_BASE_RELOCATION));
//计算需要修正的重定位项（地址）的数目
int nNumberOfReloc = (pLoc->SizeOfBlock - sizeof(IMAGE_BASE_RELOCATION)) / sizeof(WORD);
for (int i = 0; i < nNumberOfReloc; i++)
{
// 每个WORD由两部分组成。高4位指出了重定位的类型，WINNT.H中的一系列IMAGE_REL_BASED_xxx定义了重定位类型的取值。
// 低12位是相对于VirtualAddress域的偏移，指出了必须进行重定位的位置。
if ((DWORD)(pLocData[i] & 0x0000F000) == 0x00003000) //这是一个需要修正的地址
{
DWORD* pAddress = (DWORD *)((PBYTE)pDos + pLoc->VirtualAddress + (pLocData[i] & 0x0FFF));
DWORD dwDelta = (DWORD)pDos - pNt->OptionalHeader.ImageBase;
*pAddress += dwDelta;
}
}
//转移到下一个节进行处理
pLoc = (PIMAGE_BASE_RELOCATION)((PBYTE)pLoc + pLoc->SizeOfBlock);
}
return TRUE;
6.根据PE结构的导入表，加载所需的dll，并获取导入函数的地址并写入导入表中
PIMAGE_DOS_HEADER pDos = (PIMAGE_DOS_HEADER)chBaseAddress;
PIMAGE_NT_HEADERS pNt = (PIMAGE_NT_HEADERS)(chBaseAddress + pDos->e_lfanew);
PIMAGE_IMPORT_DESCRIPTOR pImportTable = (PIMAGE_IMPORT_DESCRIPTOR)((DWORD)pDos +
pNt->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);
// 循环遍历DLL导入表中的DLL及获取导入表中的函数地址
char *lpDllName = NULL;
HMODULE hDll = NULL;
PIMAGE_THUNK_DATA lpImportNameArray = NULL;
PIMAGE_IMPORT_BY_NAME lpImportByName = NULL;
PIMAGE_THUNK_DATA lpImportFuncAddrArray = NULL;
FARPROC lpFuncAddress = NULL;
DWORD i = 0;
while (TRUE)
{
if (0 == pImportTable->OriginalFirstThunk)
{
break;
}
// 获取导入表中DLL的名称并加载DLL
lpDllName = (char *)((DWORD)pDos + pImportTable->Name);
hDll = GetModuleHandleA(lpDllName);
if (NULL == hDll)
{
hDll = LoadLibraryA(lpDllName);
if (NULL == hDll)
{
pImportTable++;
continue;
}
}
i = 0;
// 获取OriginalFirstThunk以及对应的导入函数名称表首地址
lpImportNameArray = (PIMAGE_THUNK_DATA)((DWORD)pDos + pImportTable->OriginalFirstThunk);
// 获取FirstThunk以及对应的导入函数地址表首地址
lpImportFuncAddrArray = (PIMAGE_THUNK_DATA)((DWORD)pDos + pImportTable->FirstThunk);
while (TRUE)
{
if (0 == lpImportNameArray[i].u1.AddressOfData)
{
break;
}
// 获取IMAGE_IMPORT_BY_NAME结构
lpImportByName = (PIMAGE_IMPORT_BY_NAME)((DWORD)pDos + lpImportNameArray[i].u1.AddressOfData);
// 判断导出函数是序号导出还是函数名称导出
if (0x80000000 & lpImportNameArray[i].u1.Ordinal)
{
// 序号导出
lpFuncAddress = GetProcAddress(hDll, (LPCSTR) (lpImportNameArray[i].u1.Ordinal & 0x0000FFFF));
}
else
{
// 名称导出
lpFuncAddress = GetProcAddress(hDll, (LPCSTR)lpImportByName->Name);
}
lpImportFuncAddrArray[i].u1.Function = (DWORD)lpFuncAddress;
i++;
}
pImportTable++;
}
7.修改PE文件的加载基址
PIMAGE_DOS_HEADER pDos = (PIMAGE_DOS_HEADER)chBaseAddress;
PIMAGE_NT_HEADERS pNt = (PIMAGE_NT_HEADERS)(chBaseAddress + pDos->e_lfanew);
pNt->OptionalHeader.ImageBase = (ULONG32)chBaseAddress;
8.跳转到PE的入口点处执行
PIMAGE_DOS_HEADER pDos = (PIMAGE_DOS_HEADER)chBaseAddress;
PIMAGE_NT_HEADERS pNt = (PIMAGE_NT_HEADERS)(chBaseAddress + pDos->e_lfanew);
char* ExeEntry = (char*)(chBaseAddress + pNt->OptionalHeader.AddressOfEntryPoint);
// 跳转到入口点处执行
__asm
{
mov eax, ExeEntry
jmp eax
}
通过上述代码，成功加载并运行程序：
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发表于 2019-1-25 20:53
