程序的自我修改

本文目的在于向读者说明程序进行自我修改的基本方法，并希望可以起到抛砖引玉的作用。
如果读者有更好的方法或见解，欢迎来信交流E-mail: default_and_default@yahoo.cn

/*//////////////////////////////////////////////////////////////////////////////
This program will modify itself at the running time,
These  methods will be very useful in some situations,
Gook Luck!
//////////////////////////////////////////////////////////////////////////////*/
#include<stdio.h>
#include<windows.h>

void main()
{
  TCHAR Info001[MAX_PATH]="Welcome to Big Apple!";
  TCHAR Info002[MAX_PATH]="Welcome to Washington!";
  char temp=(char)0x90;
  WORD temp001=0x9090;
  DWORD temp002=0x90909090;

  PVOID BaseAddressOne=NULL;
  PVOID BaseAddressTwo=NULL;

  _asm
  {
    mov BaseAddressOne,offset LabelOne
    mov BaseAddressTwo,offset LabelTwo
  }

  MessageBox(NULL,Info001,"Information",MB_OK|MB_ICONINFORMATION);

//a kind of method to modify itself
  WriteProcessMemory(GetCurrentProcess(),BaseAddressTwo,&temp001,2,NULL);
  WriteProcessMemory(GetCurrentProcess(),BaseAddressOne,&temp001,2,NULL);


/*
//Another method to modify itself,this method needs to modify the code section's
//characteristics in PE file.

  _asm
  {
    mov ebx,BaseAddressOne
    mov ecx,BaseAddressTwo
    mov dx,temp001

    mov [ebx],dx
    mov [ecx],dx
  }
*/

LabelTwo:
  _asm
  {
    jmp LabelOne
  }
  _asm
  {
    nop
    nop
    nop
  }



  MessageBox(NULL,Info002,"Information",MB_OK|MB_ICONINFORMATION);
LabelOne:
  _asm
  {
    jmp Over
  }
  MessageBox(NULL,Info002,"Information",MB_OK|MB_ICONINFORMATION);
Over:
  return;
}



编译这个程序，我们发现WriteProcessMemory() 成功修改了程序自身代码，程序运行正常。
然后我们屏蔽程序中的WriteProcessMemory()调用，用/*  */之中的代码完成自我修改，
运行后会发现系统抛出异常 Access Violation.这是因为PE 中 代码节的属性默认为 0x60000020，
20 表示代码 20000000表示可执行，40000000表示可读，如果我们在此基础上加上 0x80000000(可写）
操作系统的loader在装载可执行文件时，便会将存放代码节数据的内存标记为可读，可写，可执行。
这样就不会有异常了。
读者可使用下面的程序来修改节属性：
/**************************************************************************************/
//The following code is used to modify characteristics of sections

#include<windows.h>
#include<stdio.h>
BOOL ModifyCharacteristicsOfSections (LPCTSTR FileName)
{
  DWORD i=0;
  HANDLE hDestinationFile=NULL;
  TCHAR  DestinationPEFile[MAX_PATH];
  DWORD NumberOfBytesRead=0;   //Number of bytes read
  DWORD NumberOfBytesWritten=0; //Number of bytes written

  DWORD ImageNtSignature=0;  //PE signature
  DWORD OffsetOfNewHeader=0;
  DWORD NumberOfSections=0;
  DWORD SizeOfSectionTable=0;           //size of section table
  
  HANDLE hGlobalAllocatedMemory=NULL;  //use GlobalAlloc();
  
  PIMAGE_SECTION_HEADER pImageSectionHeader=NULL; //a pointer to IMAGE_SECTION_TABLE

  IMAGE_DOS_HEADER ImageDosHeader;
  IMAGE_NT_HEADERS ImageNTHeaders;
  IMAGE_FILE_HEADER ImageFileHeader;
  
  IMAGE_OPTIONAL_HEADER ImageOptionalHeader;
  IMAGE_SECTION_HEADER ImageSectionHeader;
  DWORD dwFileSize=0;

  RtlZeroMemory(&ImageDosHeader,sizeof(IMAGE_DOS_HEADER));
  RtlZeroMemory(&ImageNTHeaders,sizeof(IMAGE_NT_HEADERS));
  RtlZeroMemory(&ImageFileHeader,sizeof(IMAGE_FILE_HEADER));
  
  RtlZeroMemory(&ImageOptionalHeader,sizeof(IMAGE_OPTIONAL_HEADER));
  RtlZeroMemory(&ImageSectionHeader,sizeof(IMAGE_SECTION_HEADER));
  
  strcpy(DestinationPEFile,FileName);

  hDestinationFile=CreateFile(DestinationPEFile,
    FILE_WRITE_DATA|FILE_READ_DATA,
    FILE_SHARE_WRITE,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_ARCHIVE,NULL);
  
  if(hDestinationFile==INVALID_HANDLE_VALUE)
  {
//    printf("/nCreateFile() fails!Can't open file. Please try again!/n");
//    CloseHandle(hDestinationFile);
    return TRUE;
  }
  else
  {
    dwFileSize=GetFileSize(hDestinationFile,NULL);
  }

  SetFilePointer(hDestinationFile,0,NULL,FILE_BEGIN); //Revert the file pointer,this is very important.
  
  ReadFile(hDestinationFile,&ImageDosHeader,
    sizeof(IMAGE_DOS_HEADER),&NumberOfBytesRead,NULL);
  if(NumberOfBytesRead!=sizeof(IMAGE_DOS_HEADER))
  {
//    printf("/nReadFile() fails! Can't get IMAGE_DOS_HEADER./n");
    CloseHandle(hDestinationFile);
    return FALSE;
  }
  
  OffsetOfNewHeader=ImageDosHeader.e_lfanew; //File address of new exe header
  
  SetFilePointer(hDestinationFile,(LONG)OffsetOfNewHeader,NULL,FILE_BEGIN);
  
  ReadFile(hDestinationFile,&ImageNTHeaders,
    sizeof(IMAGE_NT_HEADERS),&NumberOfBytesRead,NULL); //Retrieve IMAGE_NT_HEADERS
  if(NumberOfBytesRead!=sizeof(IMAGE_NT_HEADERS))
  {
    CloseHandle(hDestinationFile);
    return FALSE;
  }

  if(ImageNTHeaders.Signature!=0x00004550)
  {
//    printf("Error./nPE signature is invalid!/n");
    CloseHandle(hDestinationFile);
    return FALSE;
  }
  
  
  SetFilePointer(hDestinationFile,OffsetOfNewHeader+4,NULL,FILE_BEGIN);  //Set the file pointer to point to IMAGE_FILE_HEADER
  ReadFile(hDestinationFile,&ImageFileHeader,
    sizeof(IMAGE_FILE_HEADER),&NumberOfBytesRead,NULL); //Retrieve IMAGE_FILE_HEADER
  if(NumberOfBytesRead!=sizeof(IMAGE_FILE_HEADER))
  {
//    printf("/nReadFile() fails! Can't get IMAGE_FILE_HEADER./n");
    CloseHandle(hDestinationFile);
    return FALSE;
  }


  if(ImageFileHeader.NumberOfSections<1)
  {
    CloseHandle(hDestinationFile);
    return FALSE;
  }
  
  if(dwFileSize<(sizeof(IMAGE_DOS_HEADER)+sizeof(IMAGE_NT_HEADERS)+sizeof(IMAGE_SECTION_HEADER)*ImageFileHeader.NumberOfSections))
  {
    CloseHandle(hDestinationFile);
    return FALSE;
  }



  ReadFile(hDestinationFile,&ImageOptionalHeader,
    sizeof(IMAGE_OPTIONAL_HEADER),&NumberOfBytesRead,NULL); //Retrieve IMAGE_OPTIONAL_HEADER

  if(NumberOfBytesRead!=sizeof(IMAGE_OPTIONAL_HEADER))
  {
//    printf("/nReadFile() fails! Can't get IMAGE_OPTIONAL_HEADER./n");
    CloseHandle(hDestinationFile);
    return FALSE;
  }
  if(ImageOptionalHeader.SectionAlignment<ImageOptionalHeader.FileAlignment)
  {
    CloseHandle(hDestinationFile);
    return FALSE;
  }


  NumberOfSections=ImageFileHeader.NumberOfSections; //Number of sections
  SizeOfSectionTable=sizeof(IMAGE_SECTION_HEADER)*NumberOfSections; //Get the size of Section Table
  
  hGlobalAllocatedMemory=GlobalAlloc(GPTR,SizeOfSectionTable);      //Allocate memory and initialize with zero
  if(hGlobalAllocatedMemory==NULL)
  {
//    printf("/nGlobalAlloc() failed! Please try again./n"); //if failed,return
    CloseHandle(hDestinationFile);
    return FALSE;
  }
  
  
    pImageSectionHeader=(PIMAGE_SECTION_HEADER)hGlobalAllocatedMemory; //Convert a handle to a pointer to IMAGE_SECTION_HEADER
  
  for(i=0;i<NumberOfSections;i++)  //Retrieve the Section Table
  {
    ReadFile(hDestinationFile,pImageSectionHeader+i,
      sizeof(IMAGE_SECTION_HEADER),&NumberOfBytesRead,NULL);
    if(NumberOfBytesRead!=sizeof(IMAGE_SECTION_HEADER))
    {
//      printf("Error.Can't get IMAGE_SECTION_HEADER./n");
      CloseHandle(hDestinationFile);
      return FALSE;
    }
  }

  for(i=0;i<NumberOfSections;i++)
  {
    DWORD dwTempCharacteristics=0;

    if((*(pImageSectionHeader+i)).PointerToRawData+(*(pImageSectionHeader+i)).SizeOfRawData>dwFileSize)
    {
      CloseHandle(hDestinationFile);
      return FALSE;
    }
    if((*(pImageSectionHeader+i)).PointerToRawData % ImageOptionalHeader.FileAlignment!=0)
    {
      CloseHandle(hDestinationFile);
      return FALSE;
    }
    printf("/nThe name of the section%d: ",i);
    printf("%s/n",(*(pImageSectionHeader+i)).Name);
    
    printf("Characteristics: %#x/n",(*(pImageSectionHeader+i)).Characteristics);
    printf("/nPlease input the new characteristics of the section./n");
    printf("If you enter 0,the characteristics of the section will not be modified./n");
    scanf("%x",&dwTempCharacteristics);

    if(dwTempCharacteristics!=0)
      (*(pImageSectionHeader+i)).Characteristics=dwTempCharacteristics;
      printf("------------------------------------------------------");
  }

  SetFilePointer(hDestinationFile,-((long)SizeOfSectionTable),NULL,FILE_CURRENT); //Set the file poiner

  WriteFile(hDestinationFile,pImageSectionHeader,SizeOfSectionTable,&NumberOfBytesWritten,NULL);
  if(NumberOfBytesWritten==SizeOfSectionTable)
  {
    printf("/nComplete successfully!/n");
  }
  else
  {
       printf("/nWriteFile() failed!/n");
  }
  GlobalFree(hGlobalAllocatedMemory); //Free memory

  CloseHandle(hDestinationFile);

  return TRUE;    
}

void main(int argc,char *argv[])
{
  if(argc!=2)
  {
    printf("Error/nUsage:ModifyCharacteristicsOfSections CompleteDestinationFileName/n");
    return;
  }
  if(!ModifyCharacteristicsOfSections(argv[1]))
  {
    printf("/nError.This usually means that this file is not a valid PE file or/n");
    printf("that this PE file has been modified by another program,for example,shell programm./n");
  }
}


/**********************************************************************************************/
以下是上面程序的输出信息：

The name of the section0: .text
Characteristics: 0x60000020

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
e0000020
------------------------------------------------------
The name of the section1: .rdata
Characteristics: 0x40000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section2: .data
Characteristics: 0xc0000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section3: .idata
Characteristics: 0xc0000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section4: .reloc
Characteristics: 0x42000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
Complete successfully!

////////////////////////////////////////////////////////////////////////////

The name of the section0: .text
Characteristics: 0xe0000020

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section1: .rdata
Characteristics: 0x40000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section2: .data
Characteristics: 0xc0000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section3: .idata
Characteristics: 0xc0000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
The name of the section4: .reloc
Characteristics: 0x42000040

Please input the new characteristics of the section.
If you enter 0,the characteristics of the section will not be modified.
0
------------------------------------------------------
Complete successfully!