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peloader加载器

1.创建数组来保存pe文件中的内容

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HANDLE X1(char* x, unsigned char** pbuf)
{
	HANDLE X;
	DWORD FileSize;
	LPDWORD IFFileSize=0;
	LPDWORD IFReadFile=0;
	X = CreateFileA(x,
		GENERIC_READ,
		FILE_SHARE_READ | FILE_SHARE_WRITE,
		NULL,
		OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL,
		NULL
	);
	DWORD err= GetLastError();
	if (X == INVALID_HANDLE_VALUE)
	{
		printf("未能打开文件%d", err);
		exit(0);
	}
	FileSize = GetFileSize(X, IFFileSize);
	if (IFFileSize == -1)
	{
		printf("未能得到文件尺寸");
		exit(0);
	}
    *pbuf =(unsigned char *)malloc(sizeof(unsigned char)* FileSize);
	ZeroMemory(*pbuf, FileSize);//清零
	ReadFile(X, *pbuf, FileSize, IFReadFile, NULL);
	if (IFReadFile == -1)
	{
		printf("未能复制文件");
		exit(0);
	}
}

2.申请内存将DOS头NT头写入

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PIMAGE_DOS_HEADER DOS = (PIMAGE_DOS_HEADER)pbuf;
PIMAGE_NT_HEADERS64 NT = (PIMAGE_NT_HEADERS64)(pbuf + DOS->e_lfanew);
DWORD SizeOfImage = NT->OptionalHeader.SizeOfImage;
LPVOID Alloc;
if (NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress != 0)
Alloc = VirtualAlloc(NULL, SizeOfImage, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
else
Alloc = VirtualAlloc(NT->OptionalHeader.ImageBase, SizeOfImage, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
ZeroMemory(Alloc, SizeOfImage);
CopyMemory(Alloc, pbuf, NT->OptionalHeader.SizeOfHeaders);//申请dos，nt空间

3.将节区循环写入申请内存

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DWORD SectionNumber = NT->FileHeader.NumberOfSections;
for (DWORD n=0; n < SectionNumber; n++)//复制节区
{
	PIMAGE_SECTION_HEADER SectionHead = (PIMAGE_SECTION_HEADER)((char*)NT+sizeof(IMAGE_NT_HEADERS64)+ sizeof(IMAGE_SECTION_HEADER)*n);
	if (SectionHead->PointerToRawData!=0)//.bss节区（需要初始化）
	CopyMemory(SectionHead->VirtualAddress + (PCHAR)Alloc, pbuf + SectionHead->PointerToRawData, SectionHead->SizeOfRawData);
	else
	{
		ZeroMemory(SectionHead->VirtualAddress + (PCHAR)Alloc, SectionHead->Misc.VirtualSize);//清零
	}
}

4.加载重定位表

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if (NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress != 0)
{
	PIMAGE_BASE_RELOCATION ReLoc = (PIMAGE_BASE_RELOCATION)(NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress + (PCHAR)Alloc);
	while (ReLoc->SizeOfBlock != 0)
	{
		PCHAR ReV = ReLoc->VirtualAddress + (PCHAR)Alloc;//每页的虚拟地址
		int NumberOfBlock = (ReLoc->SizeOfBlock - 8) / 2;//每页有多少需要修改的值
		for (int n = 0; n < NumberOfBlock; n++)
		{
			PWORD ChangByte = (PWORD)(ReLoc + 1);
			char Type = ChangByte[n] >> 12;//获得标志位
			if (Type == 10)
			{
				PDWORD64 Offest = (PDWORD64*)((ChangByte[n] & 0xfff) + ReV);//这页当中需要修改的具体位置
				*Offest = *Offest + (ULONGLONG)Alloc - NT->OptionalHeader.ImageBase;//加上基址
			}
		}
		ReLoc = (PIMAGE_SECTION_HEADER)((PCHAR)ReLoc + ReLoc->SizeOfBlock);//下一页
	}
}

相关加载重定位表的理解可以看这篇文章：https://blog.csdn.net/Apollon_krj/article/details/77370452

5.填充IAT表

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PIMAGE_IMPORT_DESCRIPTOR IntImport = (PIMAGE_IMPORT_DESCRIPTOR)(NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress + (PCHAR)Alloc);
while (IntImport->Name!=0)//循环dll库
{
	HMODULE DllHandle;
	char DllName[50];
	strncpy(DllName,IntImport->Name+(PCHAR)Alloc,49);
	DllHandle = LoadLibraryA(DllName);
	PIMAGE_THUNK_DATA64	INT = IntImport->OriginalFirstThunk + (PCHAR)Alloc;
	PIMAGE_THUNK_DATA64	IAT = IntImport->FirstThunk + (PCHAR)Alloc;
	while (INT->u1.AddressOfData != 0)//循环dll中每个函数
	{
		if (INT->u1.Ordinal & IMAGE_ORDINAL_FLAG64)//通过序号查找函数
		{
			IAT->u1.AddressOfData = GetProcAddress(DllHandle, INT->u1.Ordinal);
		}	
		else//通过名字查找函数
		{
			PIMAGE_IMPORT_BY_NAME Fcn = (PIMAGE_IMPORT_BY_NAME)(INT->u1.AddressOfData + (PCHAR)Alloc);
			IAT->u1.AddressOfData = GetProcAddress(DllHandle, Fcn->Name);//填充IAT表
			int l = 1;
		}
		INT++;
		IAT++;
	}
	IntImport++;
}

相关填充IAT表的理解可以看这篇文章：https://blog.csdn.net/qq_35289660/article/details/107329444

6.修改程序入口

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FARPROC EOP = (FARPROC)((LPBYTE)Alloc + NT->OptionalHeader.AddressOfEntryPoint);//修改程序入口点
EOP(); 

free(pbuf);
free(Alloc);
return 0;

汇总

peloader的加载原理就是将pe文件的内容读取后根据当中的VirtualAddress将内容分配到申请空间里，然后执行。（下面是所有代码）

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#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<windows.h>
#include <stdbool.h>
#include<winnt.h>

HANDLE X1(char* x, unsigned char** pbuf)
{
	HANDLE X;
	DWORD FileSize;
	LPDWORD IFFileSize=0;
	LPDWORD IFReadFile=0;
	X = CreateFileA(x,
		GENERIC_READ,
		FILE_SHARE_READ | FILE_SHARE_WRITE,
		NULL,
		OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL,
		NULL
	);
	DWORD err= GetLastError();
	if (X == INVALID_HANDLE_VALUE)
	{
		printf("未能打开文件%d", err);
		exit(0);
	}
	FileSize = GetFileSize(X, IFFileSize);
	if (IFFileSize == -1)
	{
		printf("未能得到文件尺寸");
		exit(0);
	}
    *pbuf =(unsigned char *)malloc(sizeof(unsigned char)* FileSize);
	ZeroMemory(*pbuf, FileSize);
	ReadFile(X, *pbuf, FileSize, IFReadFile, NULL);
	if (IFReadFile == -1)
	{
		printf("未能复制文件");
		exit(0);
	}
}
VOID MAIN1(unsigned char* pbuf) {
	printf("这是个64进制文件\n");
	Sleep(500);
	PIMAGE_DOS_HEADER DOS = (PIMAGE_DOS_HEADER)pbuf;
	PIMAGE_NT_HEADERS64 NT = (PIMAGE_NT_HEADERS64)(pbuf + DOS->e_lfanew);
	DWORD SizeOfImage = NT->OptionalHeader.SizeOfImage;
	LPVOID Alloc;
	if (NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress != 0)
	Alloc = VirtualAlloc(NULL, SizeOfImage, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
	else
	Alloc = VirtualAlloc(NT->OptionalHeader.ImageBase, SizeOfImage, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE);
	ZeroMemory(Alloc, SizeOfImage);
	CopyMemory(Alloc, pbuf, NT->OptionalHeader.SizeOfHeaders);//申请dos，nt空间
	DWORD SectionNumber = NT->FileHeader.NumberOfSections;
	for (DWORD n=0; n < SectionNumber; n++)//复制节区
	{
		PIMAGE_SECTION_HEADER SectionHead = (PIMAGE_SECTION_HEADER)((char*)NT+sizeof(IMAGE_NT_HEADERS64)+ sizeof(IMAGE_SECTION_HEADER)*n);
		if (SectionHead->PointerToRawData!=0)//.bss特殊
		CopyMemory(SectionHead->VirtualAddress + (PCHAR)Alloc, pbuf + SectionHead->PointerToRawData, SectionHead->SizeOfRawData);
		else//.bss特殊
		{
			ZeroMemory(SectionHead->VirtualAddress + (PCHAR)Alloc, SectionHead->Misc.VirtualSize);
		}
	}
	if (NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress != 0)
	{
		PIMAGE_BASE_RELOCATION ReLoc = (PIMAGE_BASE_RELOCATION)(NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC].VirtualAddress + (PCHAR)Alloc);
		while (ReLoc->SizeOfBlock != 0)
		{
			PCHAR ReV = ReLoc->VirtualAddress + (PCHAR)Alloc;
			int NumberOfBlock = (ReLoc->SizeOfBlock - 8) / 2;
			for (int n = 0; n < NumberOfBlock; n++)
			{
				PWORD ChangByte = (PWORD)(ReLoc + 1);
				char Type = ChangByte[n] >> 12;
				//PDWORD64 Offest = 0;
				if (Type == 10)
				{
					// 找到目标地址
					// 修改目标地址的值：方法是原来的值+偏移
					PDWORD64 Offest = (PDWORD64*)((ChangByte[n] & 0xfff) + ReV);
					*Offest = *Offest + (ULONGLONG)Alloc - NT->OptionalHeader.ImageBase;
				}
			}
			ReLoc = (PIMAGE_SECTION_HEADER)((PCHAR)ReLoc + ReLoc->SizeOfBlock);
		}
	}
	PIMAGE_IMPORT_DESCRIPTOR IntImport = (PIMAGE_IMPORT_DESCRIPTOR)(NT->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress + (PCHAR)Alloc);
	while (IntImport->Name!=0)//引入表
	{
		HMODULE DllHandle;
		char DllName[50];
		strncpy(DllName,IntImport->Name+(PCHAR)Alloc,49);
		DllHandle = LoadLibraryA(DllName);
		PIMAGE_THUNK_DATA64	INT = IntImport->OriginalFirstThunk + (PCHAR)Alloc;
		PIMAGE_THUNK_DATA64	IAT = IntImport->FirstThunk + (PCHAR)Alloc;
		while (INT->u1.AddressOfData != 0)
		{
			if (INT->u1.Ordinal & IMAGE_ORDINAL_FLAG64)
			{
				IAT->u1.AddressOfData = GetProcAddress(DllHandle, INT->u1.Ordinal);
			}	
			else
			{
				PIMAGE_IMPORT_BY_NAME Fcn = (PIMAGE_IMPORT_BY_NAME)(INT->u1.AddressOfData + (PCHAR)Alloc);
				IAT->u1.AddressOfData = GetProcAddress(DllHandle, Fcn->Name);
				int l = 1;
			}
			INT++;
			IAT++;
		}
		IntImport++;
	}
	FARPROC EOP = (FARPROC)((LPBYTE)Alloc + NT->OptionalHeader.AddressOfEntryPoint);
	EOP(); 

	free(pbuf);
	free(Alloc);
	return 0;
}//64文件处理
int main(int argc,char* argv[])
{
	unsigned char* pbuf=NULL;
	X1(argv[1],&pbuf);
	PIMAGE_DOS_HEADER DOS = (PIMAGE_DOS_HEADER)pbuf;
	if (*(PWORD)pbuf == 0x5A4D)
		printf("这是个PE文件\n");
	WORD Magic = *(WORD*)(pbuf + (DOS->e_lfanew + 6 * 4));
	if (Magic == 0x20b)
		MAIN1(pbuf);
}