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!
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