一个用CRC程序保护程序的具体例子

标题：一个用CRC程序保护程序的具体例子
作者：bzhkl
时间：2007-03-12 20:25
链接：http://bbs.pediy.com/showthread.php?t=40938

这是一个用CRC程序保护的具体例子前几天在网上找具体的例子想直接放在自己的程序里竟然没有找到完整的实例只有算法和原理我整理了一下找到的内容在控制台下写了个完整的程序

只要大家用改动程序的一个字节程序也能检测出来比如把int3 nop掉也能检测出来

程序链接成可执行文件后要用16进制工具把原来程序的CRC值写在PE Optional_Section的Win32Version处

下面是源代码附件是CRC值已经写入的可执行文件大家可试验一下

#include "stdio.h"
#include "windows.h"

DWORD CRC32(BYTE* ptr,DWORD Size)
{

  DWORD crcTable[256],crcTmp1;

  //动态生成CRC-32表
  for (int i=0; i<256; i++)
   {
    crcTmp1 = i;
    for (int j=8; j>0; j--)
     {
      if (crcTmp1&1) crcTmp1 = (crcTmp1 >> 1) ^ 0xEDB88320L;
       else crcTmp1 >>= 1;
    }

     crcTable[i] = crcTmp1;
   }
  //计算CRC32值
  DWORD crcTmp2= 0xFFFFFFFF;
  while(Size--)
  {
    crcTmp2 = ((crcTmp2>>8) & 0x00FFFFFF) ^ crcTable[ (crcTmp2^(*ptr)) & 0xFF ];
    ptr++;
  }

  return (crcTmp2^0xFFFFFFFF);
}
bool isModified = false;

void main()
{
/*  DWORD res = CRC32((BYTE*)p, 6);
  printf("%x    ", res);*/
  DWORD dwNumberOfBytesReadWritten;
  HMODULE hmod;
  HGLOBAL hMemory;
  LPVOID pMemory;
  DWORD dwFileSize;
  CHAR szFileName[20];
  hmod = ::GetModuleHandle(0);

  ::GetModuleFileName(hmod, szFileName, MAX_PATH);

  HANDLE hFile = ::CreateFile(szFileName, GENERIC_READ, FILE_SHARE_READ, NULL,
    OPEN_EXISTING, FILE_ATTRIBUTE_ARCHIVE, 0);
  if(hFile != INVALID_HANDLE_VALUE)
    dwFileSize = ::GetFileSize(hFile, NULL);

  hMemory = ::GlobalAlloc(GMEM_MOVEABLE|GMEM_ZEROINIT,  dwFileSize);

  pMemory = ::GlobalLock(hMemory);

  ReadFile(hFile, pMemory, dwFileSize, &dwNumberOfBytesReadWritten, NULL);

  ::CloseHandle(hFile);

  DWORD dwPEHead, dwWin32Version;
  LPVOID pWin32Version;
  LPVOID pMemoryPEHead = pMemory;

  BYTE* pp;
  pp = static_cast<BYTE*>(pMemory) + 0x3c;
  pMemoryPEHead = (LPVOID)pp;
//  static_cast<BYTE*>(pMemory)++
//  static_cast(BYTE*)pMemory2 = static_cast(BYTE*)pMemory+ 0x3c;
  //static_cast<BYTE*>(pMemory2) = static_cast<BYTE*>(pMemory2) + 0x3c;
  dwPEHead = *((DWORD*)pMemoryPEHead);

  pWin32Version = pMemory;
  dwWin32Version = dwPEHead + 0x4c;

  BYTE* Version;
  Version = static_cast<BYTE*>(pWin32Version) + dwWin32Version;
  pWin32Version = (BYTE*)Version;

  DWORD OriginalCRC32 = *((DWORD*)pWin32Version);
  *((DWORD*)pWin32Version) = 0;

  DWORD NowCRC32 = CRC32((BYTE*)pMemory, dwFileSize);

  if(OriginalCRC32 != NowCRC32)
    ::MessageBox(0, "error", "e", MB_OK);
  else
    ::MessageBox(0, "chenggong", "c", MB_OK);

  getchar();


}