移动PE导出表

Contents

1. 1. 导出表
2. 2. 移动导出表的步骤
3. 3. 移动导出表

导出表

导出表一般多见于DLL和SYS文件，EXE在少部分情况下拥有导出表，导出表中存储了，当前DLL可供调用的函数的地址、函数名称，导出表的地址存储在数据目录项的第一个结构中。

IMAGE_SECTION_HEADER[0]

typedef struct _IMAGE_DATA_DIRECTORY {
    DWORD   VirtualAddress;//导出表开始的地址 RVA
    DWORD   Size;//导出表大小				
}IMAGE_DATA_DIRECTORY, *PIMAGE_DATA_DIRECTORY;

存储了导出表的地址(RVA)及其大小

导出表结构

typedef struct _IMAGE_EXPORT_DIRECTORY {
    DWORD   Characteristics;    // 未使用					
    DWORD   TimeDateStamp;		// 时间戳					
    WORD    MajorVersion;		// 未使用
    WORD    MinorVersion;		// 未使用
    DWORD   Name;				// 指向该导出表文件名字符串
    DWORD   Base;				// 导出函数起始序号
    DWORD   NumberOfFunctions;	// 所有导出函数的个数
    DWORD   NumberOfNames;		// 以函数名字导出的函数个数
    DWORD   AddressOfFunctions;     // 导出函数地址表RVA
    DWORD   AddressOfNames;         // 导出函数名称表RVA
    DWORD   AddressOfNameOrdinals;  // 导出函数序号表RVA
} IMAGE_EXPORT_DIRECTORY, *PIMAGE_EXPORT_DIRECTORY;

导出表中最重要的就是三张表，AddressOfFunctions、AddressOfNames、AddressOfNameOrdinals，分别存储了函数地址，函数名称，函数序号，这里有两种函数查找方式，分别是按照函数名称查找，还有按照序号查找。

我们在移动的时候，要注意RVA和FOA的转换，RVA是在内存中拉伸后的偏移，需要我们转换成文件中的偏移FOA才可以在文件中进行复制和修改。

导出函数名称表的移动是一个难点，导出函数名称表中存储了导出函数名称的偏移地址RVA，需要根据地址再进行访问函数名称。

移动导出表的步骤

1. 在PE文件中新增一个节，并且新增对应的节表。
2. 复制：AddressOfFunction(size:NumberOfFunctions * 4) 到新增的节
3. 复制：AddressOfNameOrdinals(size:NumberOfNames * 2) 到新增的节中
4. 复制：AddressOfNames(szie:NumberOfNames * 4) 到新增的节中
5. 复制：AddressOfNames表中对应的所有地址，及其函数名，移动字符串时也需要注意大小\0结尾(每复制一个函数名就要计算偏移RVA添加到函数名称表的地址中)
6. 复制：导出表结构体 到新增的节中
7. 修改导出表结构中的对应AddressOfFunctions、AddressOfNameOrdinals、AddressOfNames 地址，其他的参数不影响运行。
8. 修复目录项中的VirtualAddress，指向新的导出表的地址

这里要梳理清楚在移动过程中的各个参数，在什么时候转换为FOA，什么时候转换为RVA

定位导出表的地址时，需要将IMAGE_SECTION_HEADER[0].VirtualAddress的RVA->FOA，以便于在文件中定位导出表的地址

在移动导出表的AddressOfFunction、AddressOfNameOrdinals、AddressOfNames时，需要将RVA->FOA以便于在文件中复制

在移动AddressOfNames中的地址指向的函数名字符串时，要将AddressOfNames中的地址RVA->FOA，并且在移动完后，修改AddressOfNames中存储的地址时，要FOA->RVA

将导出表中的AddressOfFunctions、AddressOfNameOrdinals、AddressOfNames 地址修改为新复制的对应的地址时，要将新复制的对应的地址FOA->RVA

修复数据目录项中的VirualAddress时，要将新复制的导出表的存储地址FOA->RVA

移动导出表

DWORD RVATOFOA(DWORD RVA,LPVOID pFileBuffer)
{
	DWORD FOA = NULL;
	PIMAGE_DOS_HEADER pDosHeader = NULL;
	PIMAGE_NT_HEADERS pNtHeaders = NULL;
	PIMAGE_FILE_HEADER pFileHeader = NULL;
	PIMAGE_OPTIONAL_HEADER pOptionalHeader = NULL;
	PIMAGE_SECTION_HEADER pSectionHeader = NULL;

	pDosHeader = (PIMAGE_DOS_HEADER)pFileBuffer;
	pNtHeaders = (PIMAGE_NT_HEADERS)((DWORD)pDosHeader + pDosHeader->e_lfanew);
	pFileHeader = (PIMAGE_FILE_HEADER)((DWORD)pNtHeaders + 4);
	pOptionalHeader = (PIMAGE_OPTIONAL_HEADER)((DWORD)pFileHeader + IMAGE_SIZEOF_FILE_HEADER);
	pSectionHeader = (PIMAGE_SECTION_HEADER)((DWORD)pOptionalHeader + pFileHeader->SizeOfOptionalHeader);
	
	if(RVA <= pOptionalHeader->SizeOfHeaders)
		return RVA;
	for(;RVA > (pSectionHeader->VirtualAddress + pSectionHeader->Misc.VirtualSize);pSectionHeader++);//定位到所在节
	FOA = RVA - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
	return FOA;

}

DWORD FOATORVA(DWORD FOA,LPVOID pFileBuffer)
{
	DWORD RVA = NULL;

	PIMAGE_DOS_HEADER pDosHeader = NULL;
	PIMAGE_NT_HEADERS pNtHeaders = NULL;
	PIMAGE_FILE_HEADER pFileHeader = NULL;
	PIMAGE_OPTIONAL_HEADER pOptionalHeader = NULL;
	PIMAGE_SECTION_HEADER pSectionHeader = NULL;
    
	pDosHeader = (PIMAGE_DOS_HEADER)pFileBuffer;
	pNtHeaders = (PIMAGE_NT_HEADERS)((DWORD)pDosHeader + pDosHeader->e_lfanew);
	pFileHeader = (PIMAGE_FILE_HEADER)((DWORD)pNtHeaders + 4);
	pOptionalHeader = (PIMAGE_OPTIONAL_HEADER)((DWORD)pFileHeader + IMAGE_SIZEOF_FILE_HEADER);
	pSectionHeader = (PIMAGE_SECTION_HEADER)((DWORD)pOptionalHeader + pFileHeader->SizeOfOptionalHeader);

	if(FOA <= pOptionalHeader->SizeOfHeaders)
		return FOA;
	for(;FOA > (pSectionHeader->VirtualAddress + pSectionHeader->Misc.VirtualSize);pSectionHeader++);//定位到所在节
	RVA = FOA - pSectionHeader->PointerToRawData + pSectionHeader->VirtualAddress ;
	return RVA;
}

BOOL MoveExport(LPVOID pFileBuffer)
{
	PIMAGE_DOS_HEADER pDosHeader = NULL;//DOS头
	PIMAGE_NT_HEADERS pNtHeaders = NULL;//NT头
	PIMAGE_FILE_HEADER pFileHeader = NULL;//标准PE头
	PIMAGE_OPTIONAL_HEADER pOptionalHeader = NULL;//拓展PE头
	PIMAGE_SECTION_HEADER pSectionHeader = NULL;//节表
	PIMAGE_SECTION_HEADER pNewSec = NULL;//新节表结构
	PIMAGE_EXPORT_DIRECTORY pExportDirectory = NULL; //导出表结构体

	pDosHeader = (PIMAGE_DOS_HEADER)pFileBuffer;
	pNtHeaders = (PIMAGE_NT_HEADERS)((DWORD)pDosHeader + pDosHeader->e_lfanew);
	pFileHeader = (PIMAGE_FILE_HEADER)((DWORD)pNtHeaders + 4);
	pOptionalHeader = (PIMAGE_OPTIONAL_HEADER)((DWORD)pFileHeader + IMAGE_SIZEOF_FILE_HEADER);
	pSectionHeader = (PIMAGE_SECTION_HEADER)((DWORD)pOptionalHeader + pFileHeader->SizeOfOptionalHeader);

	//判断是否有足够的空间添加节表
	if ((pOptionalHeader->SizeOfHeaders - ((DWORD)pSectionHeader - (DWORD)pFileBuffer + pFileHeader->NumberOfSections * 40)) < 80)
	{
		printf("空间不足");
		return false;
	}

	//新增节表结构
	pNewSec = (PIMAGE_SECTION_HEADER)(pSectionHeader + pFileHeader->NumberOfSections);

	//修改节表内容
	memcpy(pNewSec->Name,".export",8);//修改节表名

	PIMAGE_SECTION_HEADER upSecHeader = (PIMAGE_SECTION_HEADER)(pSectionHeader + pFileHeader->NumberOfSections-1);

	if(upSecHeader->Misc.VirtualSize > upSecHeader->SizeOfRawData)//修改节表VrituallAddress
	{
		pNewSec->VirtualAddress = upSecHeader->VirtualAddress + upSecHeader->Misc.VirtualSize;
	}else{
		pNewSec->VirtualAddress = upSecHeader->VirtualAddress + upSecHeader->SizeOfRawData;
	}

	pNewSec->SizeOfRawData = 0x1000;//新增的节区的大小
	pNewSec->PointerToRawData = upSecHeader->PointerToRawData + upSecHeader->SizeOfRawData;//文件中的偏移
	pNewSec->Characteristics = 0x60000020;//修改属性(可执行)

	//在新增节表后增加40个字节的空白区
	memset(pNewSec+1, 0, 40);

	//修改NT头属性
	
	pFileHeader->NumberOfSections += 1;//修改NumberOfSection数量
	pOptionalHeader->SizeOfImage += 0x1000;//修改SizeOfImage大小

	
	LPVOID NewBuffer = malloc(pOptionalHeader->SizeOfImage);//申请内存
	memset(NewBuffer, 0, pOptionalHeader->SizeOfImage);//初始化内存

	memcpy(NewBuffer, pFileBuffer,pOptionalHeader->SizeOfImage);//复制内存


	//定位导出表
	DWORD ExportFoa = NULL;//导出表FOA
	PDWORD AddressOfNames = NULL;//导出函数名称表
	LPVOID AddressOfFunctions = NULL;//导出函数地址表
	PWORD AddressOfNameOrdinals = NULL;//导出函数序号表

	DWORD AddressOfNamesFOA = NULL;//导出函数名称表FOA
	DWORD AddressOfFunctionsFOA = NULL;//导出函数地址表FOA
	DWORD AddressOfNameOrdinalsFOA = NULL;//导出函数序号表FOA

	ExportFoa = RVATOFOA(pOptionalHeader->DataDirectory[0].VirtualAddress,pFileBuffer);//获取导出表的地址FOA

	pExportDirectory = (PIMAGE_EXPORT_DIRECTORY)((DWORD)pFileBuffer + ExportFoa);//定位导出表

	AddressOfNamesFOA = RVATOFOA(pExportDirectory->AddressOfNames,pFileBuffer);//获取导出函数名称表FOA
	AddressOfFunctionsFOA = RVATOFOA(pExportDirectory->AddressOfFunctions,pFileBuffer);//获取到处函数地址表FOA
	AddressOfNameOrdinalsFOA = RVATOFOA(pExportDirectory->AddressOfNameOrdinals,pFileBuffer);//获取导出函数序号表FOA

	AddressOfNames = (PDWORD)((DWORD)pFileBuffer + AddressOfNamesFOA);//定位导出函数名称表
	AddressOfFunctions = (LPVOID)((DWORD)pFileBuffer + AddressOfFunctionsFOA);//定位导出函数地址表
	AddressOfNameOrdinals = (PWORD)((DWORD)pFileBuffer + AddressOfNameOrdinalsFOA);//定位导出函数序号表

	////复制AddressOfFunctions表 
	LPVOID pNewSecAddr = (LPVOID)((DWORD)NewBuffer+pNewSec->PointerToRawData);//定位新节表的地址
	memcpy(pNewSecAddr,AddressOfFunctions,(pExportDirectory->NumberOfFunctions * 4));

	//复制AddressOfNameOrdinals表
	pNewSecAddr =(LPVOID)((DWORD)pNewSecAddr + (pExportDirectory->NumberOfFunctions * 4));
	memcpy(pNewSecAddr,AddressOfNameOrdinals,(pExportDirectory->NumberOfNames * 2));

	//复制AddressOfNames
	pNewSecAddr =(LPVOID)((DWORD)pNewSecAddr + (pExportDirectory->NumberOfNames * 2));
	PDWORD NameAddr = (PDWORD)pNewSecAddr;//这里存储一下函数地址名称表的地址，以便后边移动名称的时候修改相应地址
	memcpy(pNewSecAddr,AddressOfNames,(pExportDirectory->NumberOfNames * 4));


	//复制函数名称表中的名称 
	pNewSecAddr =(LPVOID)((DWORD)pNewSecAddr + (pExportDirectory->NumberOfNames * 4));
	//每复制一个函数名就要计算偏移添加到名字表的地址里

	DWORD NameAddOffset = (DWORD)pNewSecAddr - (DWORD)NewBuffer;//函数名称偏移

	for(size_t i=0;i < pExportDirectory->NumberOfNames;i++,AddressOfNames++)
	{
		DWORD NameOffset = (DWORD)*AddressOfNames;
		PCHAR FName = (PCHAR)((DWORD)pFileBuffer + NameOffset);
		size_t l = 0;
		
		*NameAddr = FOATORVA(NameAddOffset,NewBuffer);//复制函数名称偏移到地址中
		NameAddr = (PDWORD)((DWORD)NameAddr + 0x4);

		while(FName[l] != '\0')
		{
			l += 1;
		}

		NameAddOffset += (l+1);
		memcpy(pNewSecAddr,FName,(l+1));//复制函数名字符串到地址中

		pNewSecAddr =(LPVOID)((DWORD)pNewSecAddr + l+1);
	}

	//复制IMAGE_EXPORT_DIRECTORY结构体
	memcpy(pNewSecAddr,pExportDirectory,pOptionalHeader->DataDirectory[0].Size);
	PIMAGE_EXPORT_DIRECTORY pNewExportDirectory = (PIMAGE_EXPORT_DIRECTORY)pNewSecAddr;//地址赋值给新的导出表结构体

	//修改新的导出表的AddressOfFunctions、AddressOfNameOrdinals、AddressOfNames地址，这里需要FOA->RVA
	pNewExportDirectory->AddressOfFunctions = FOATORVA(pNewSec->PointerToRawData,NewBuffer);
	pNewExportDirectory->AddressOfNameOrdinals = FOATORVA(pNewSec->PointerToRawData + pExportDirectory->NumberOfFunctions * 4,NewBuffer);
	pNewExportDirectory->AddressOfNames = FOATORVA(pNewSec->PointerToRawData + pExportDirectory->NumberOfFunctions * 4 + pExportDirectory->NumberOfNames * 2,NewBuffer);
	
	
	//修复目录项中的值，指向新的导出表的地址RVA
	pDosHeader = (PIMAGE_DOS_HEADER)NewBuffer;
	pNtHeaders = (PIMAGE_NT_HEADERS)((DWORD)pDosHeader + pDosHeader->e_lfanew);
	pFileHeader = (PIMAGE_FILE_HEADER)((DWORD)pNtHeaders + 4);
	pOptionalHeader = (PIMAGE_OPTIONAL_HEADER)((DWORD)pFileHeader + IMAGE_SIZEOF_FILE_HEADER);
	pSectionHeader = (PIMAGE_SECTION_HEADER)((DWORD)pOptionalHeader + pFileHeader->SizeOfOptionalHeader);
	pOptionalHeader->DataDirectory[0].VirtualAddress = FOATORVA((DWORD)pNewExportDirectory - (DWORD)NewBuffer,NewBuffer);

	FILE* fp = fopen("C:\\testD.dll","wb+");
	fwrite(NewBuffer,pOptionalHeader->SizeOfImage,1,fp);
	fclose(fp);
	return true;

}

查看移动后的效果

用工具打开，可以看到节表添加成功

导出表也可以正常解析

用十六进制编辑器打开我们移动后的Dll文件进行查看，可以看到我们移动的各个位置如下

在移动的过程中，如果遇到问题，也可以用十六进制编辑器打开我们移动后保存的文件，一步一步的对比调试。

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