加壳原理与简单实现加壳（delphi源码）

{*****************************************************************
AddShell（）源自于前一段时间有写的addsection（）新增区段代码，
在增加区段代码的基础上，追加了
1.修改启动入口点位置
2.增加一段壳头xor $50的代码function AttachStart-function AttachEnd
这一段代码是先填充，再被修改成合适原EXE的壳头
3.修改原启动代码入口点所在区段的段属性可写并进行xor $50运算加密

不支持addshell（）处理已经过addshell的exe
*****************************************************************}

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
Button2: TButton;
Button3: TButton;
procedure Button1Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1 : TForm1;

implementation

{$R *.dfm}
function AttachStart: dword; stdcall; //我们定义的待填充数据
asm
pushfd
pushad
mov eax,$12345678 //将会被自动计算并修改为加密初始地址
mov ebx,$1234 //将会被自动计算并修改为加密大小
mov ecx,0
@AA:
xor byte ptr[eax],$50
inc eax
inc ecx
cmp ecx,ebx
jbe @aa
popad
popfd
push $12345678 //将会被自动计算并修改为原OEP
ret
end;

function AttachEnd: dword; stdcall;
begin
end;

{-------------------------增加区块并实现简易加壳--------------------------------}
procedure AddShell(lFileName: string; lBackup: boolean); //打开exe文件,是否备份
var
hFile : THandle; //文件句柄
ImageDosHeader : IMAGE_DOS_HEADER; //DOS部首
ImageNtHeaders : IMAGE_NT_HEADERS; //映象头
ImageSectionHeader: IMAGE_SECTION_HEADER; //块表
lPointerToRawData : dword; //指向文件中的偏移
lVirtualAddress : dword; //指向内存中的偏移
i : integer; //循环变量
BytesRead, ByteSWrite: Cardinal; //读写用参数
AttachSize : dword; //附加段大小
AttachData, ChangeData: integer; //附加段填充数据
OEP : integer; //使用过程中用到的EP
lpBuffer : array[0..1024 * 400] of byte; {待加密数据存储缓冲区}
nNumberOfBytesToRead, lpNumberOfBytesRead: dword; //加密时用到的一些数据
StartEN, SizeEN, StartCr: dword; //加密用的开始物理地址和大小
begin

//定义附加段填充数据
AttachData := 0;

//打开文件
hFile := CreateFile(PChar(lFileName), GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ or FILE_SHARE_WRITE, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

//校验
if hFile = INVALID_HANDLE_VALUE then
begin
ShowMessage('打开文件失败');
exit;
end;

//确认备份
if lBackup then CopyFile(PChar(lFileName), PChar(lFileName + '.bak'), False);
try

//读取DOS部首到ImageDosHeader
ReadFile(hFile, ImageDosHeader, SizeOf(ImageDosHeader), BytesRead, nil);

//校验
if ImageDosHeader.e_magic <> IMAGE_DOS_SIGNATURE then
begin
ShowMessage('不是有效的PE文件!');
exit;
end;

//指向映象头
SetFilePointer(hFile, ImageDosHeader._lfanew, nil, FILE_BEGIN);

//读取映向头到ImageNtHeaders
ReadFile(hFile, ImageNtHeaders, SizeOf(ImageNtHeaders), BytesRead, nil);

//校验
if ImageNtHeaders.Signature <> IMAGE_NT_SIGNATURE then
begin
ShowMessage('不是有效的PE文件');
exit;
end;
{********************************}
{OEP=基址+原EP}
OEP := ImageNtHeaders.OptionalHeader.ImageBase + ImageNtHeaders.OptionalHeader.AddressOfEntryPoint;

{********************************}

//计算加入块对齐后大小
AttachSize := ((integer(@AttachEnd) - integer(@AttachStart)) div ImageNtHeaders.OptionalHeader.FileAlignment + 1) * ImageNtHeaders.OptionalHeader.FileAlignment;

//初始化文件中偏移和映象中偏移
lPointerToRawData := 0;
lVirtualAddress := 0;

for i := 0 to ImageNtHeaders.FileHeader.NumberOfSections - 1 do
begin

//读取块表中信息
ReadFile(hFile, ImageSectionHeader, SizeOf(ImageSectionHeader), BytesRead, nil);

{********************************}
{查找原EP所在区段(原EP所在区段)，记录物理偏移（加密用初始地址），物理大小（加密用长度）}
if LPCSTR(@ImageSectionHeader.Name[0]) = '.EN' then
begin
ShowMessage('已经过本addshell处理！');
exit;
end;

if ImageNtHeaders.OptionalHeader.AddressOfEntryPoint > ImageSectionHeader.VirtualAddress then
begin
StartEN := ImageSectionHeader.PointerToRawData;
SizeEN := ImageSectionHeader.SizeOfRawData;
StartCr := ImageNtHeaders.OptionalHeader.ImageBase + ImageSectionHeader.VirtualAddress;
end;

{********************************}

//计算文件中偏移
if lPointerToRawData < ImageSectionHeader.PointerToRawData + ImageSectionHeader.SizeOfRawData then
lPointerToRawData := ImageSectionHeader.PointerToRawData + ImageSectionHeader.SizeOfRawData;

//计算映象中偏移
if lVirtualAddress < ImageSectionHeader.VirtualAddress + ImageSectionHeader.Misc.VirtualSize then
lVirtualAddress := ImageSectionHeader.VirtualAddress + ImageSectionHeader.Misc.VirtualSize;
end;

{增加块,定义块各项属性}

Move('.EN'#0, ImageSectionHeader.Name[0], 5);

//设置初始属性
ImageSectionHeader.Misc.VirtualSize := AttachSize;
ImageSectionHeader.VirtualAddress := lVirtualAddress;
ImageSectionHeader.SizeOfRawData := AttachSize;
ImageSectionHeader.PointerToRawData := lPointerToRawData;
ImageSectionHeader.PointerToRelocations := 0;
ImageSectionHeader.PointerToLinenumbers := 0;
ImageSectionHeader.NumberOfRelocations := 0;

//校正新节物理偏移(物理区块对齐)
if ImageSectionHeader.VirtualAddress mod ImageNtHeaders.OptionalHeader.SectionAlignment > 0 then
ImageSectionHeader.VirtualAddress := (ImageSectionHeader.VirtualAddress div ImageNtHeaders.OptionalHeader.SectionAlignment + 1) * ImageNtHeaders.OptionalHeader.SectionAlignment;

//校正新节映象偏移(映象中区块对齐)
if ImageSectionHeader.Misc.VirtualSize mod ImageNtHeaders.OptionalHeader.SectionAlignment > 0 then
ImageSectionHeader.Misc.VirtualSize := (ImageSectionHeader.Misc.VirtualSize div ImageNtHeaders.OptionalHeader.SectionAlignment + 1) * ImageNtHeaders.OptionalHeader.SectionAlignment;

//设置区块属性
ImageSectionHeader.Characteristics := $E00000E0;

//保存区块信息
WriteFile(hFile, ImageSectionHeader, SizeOf(ImageSectionHeader), ByteSWrite, nil);

//校正内存映象大小
ImageNtHeaders.OptionalHeader.SizeOfImage := ImageNtHeaders.OptionalHeader.SizeOfImage + ImageSectionHeader.Misc.VirtualSize;
//更新OEP
ImageNtHeaders.OptionalHeader.AddressOfEntryPoint := ImageSectionHeader.VirtualAddress;

//校正块数目
Inc(ImageNtHeaders.FileHeader.NumberOfSections);

//定位到映象头
SetFilePointer(hFile, ImageDosHeader._lfanew, nil, FILE_BEGIN);

//保存校正过的映象头
WriteFile(hFile, ImageNtHeaders, SizeOf(ImageNtHeaders), ByteSWrite, nil);

//定位到新节开始处
SetFilePointer(hFile, ImageSectionHeader.PointerToRawData, nil, FILE_BEGIN);

//用00数据填充满新节
for i := 1 to AttachSize do
begin
WriteFile(hFile, PByte(@AttachData)^, 1, ByteSWrite, nil);
end;

{填充自定义数据}
//指向新节开始处
SetFilePointer(hFile, ImageSectionHeader.PointerToRawData, nil, FILE_BEGIN);

//填充我们定义的数据
WriteFile(hFile, PByte(@AttachStart)^, integer(@AttachEnd) - integer(@AttachStart), ByteSWrite, nil);
{********************************}
//修改所谓的外壳处大量数据
ChangeData := ImageSectionHeader.PointerToRawData + 3;
SetFilePointer(hFile, ChangeData, nil, FILE_BEGIN);
WriteFile(hFile, StartCr, 4, ByteSWrite, nil); //开始加密地址
ChangeData := ChangeData + 5;
SetFilePointer(hFile, ChangeData, nil, FILE_BEGIN);
WriteFile(hFile, SizeEN, 4, ByteSWrite, nil); //大小
ChangeData := ChangeData + 21;
SetFilePointer(hFile, ChangeData, nil, FILE_BEGIN);
WriteFile(hFile, OEP, 4, ByteSWrite, nil); //跳回OEP

{********************************}
//没有异常,显示增加区块成功!
ShowMessage('增加区块成功!');

SetFilePointer(hFile, StartEN, nil, FILE_BEGIN);
ReadFile(hFile, lpBuffer, SizeEN, BytesRead, nil);
for i := 0 to SizeEN - 1 do
begin
byte(pointer(integer(@lpBuffer) + i)^) := byte(pointer(integer(@lpBuffer) + i)^) xor $50;
end;
SetFilePointer(hFile, StartEN, nil, FILE_BEGIN);
WriteFile(hFile, lpBuffer, SizeEN, ByteSWrite, nil);
//没有异常,显示变换成功!
ShowMessage('变换数据成功!');

{********************************}
SetFilePointer(hFile, (ImageDosHeader._lfanew + SizeOf(ImageNtHeaders)), nil, FILE_BEGIN);

for i := 0 to ImageNtHeaders.FileHeader.NumberOfSections - 1 do
begin

//读取块表中信息
ReadFile(hFile, ImageSectionHeader, SizeOf(ImageSectionHeader), BytesRead, nil);
if ImageSectionHeader.PointerToRawData = StartEN then
begin
ImageSectionHeader.Characteristics := $E00000E0;
SetFilePointer(hFile, -SizeOf(ImageSectionHeader), nil, FILE_CURRENT);
//保存区块信息
WriteFile(hFile, ImageSectionHeader, SizeOf(ImageSectionHeader), ByteSWrite, nil);
Break;
end;
end;
ShowMessage('修改区段属性成功!');
{********************************}

finally

{8.退出}
//关闭文件
CloseHandle(hFile);
end;

end;
{*************************Func end*********************************}

procedure TForm1.Button1Click(Sender: TObject);//addshell
begin

AddShell(Edit1.text, true);
end;

procedure TForm1.Button3Click(Sender: TObject);//browser
begin
with TOpenDialog.Create(Self) do
try
Filter := '可执行文件 (*.exe)|*.exe';
if Execute then
begin
Edit1.text := FileName;
end;
finally
Free;
end;
end;

procedure TForm1.Button2Click(Sender: TObject);//exit
begin
close;
end;

end.