新CrackMe160之142 - xyzero - keygenme2

OD载入程序,搜索界面可定位到成功关键词Good job %s 0040135B, 向上可以找到方法入口为0040112E, C++的程序,在IDA中查看对应源码为:

...
v49 = 24711447;
nSize = 255;
pcbBuffer = 255;
GetDlgItemTextA(hDlg, 1000, &String, 24);
v1 = strlen(&String);
v45 = v1;
if ( v1 >= 4 )
{
  v2 = 0;
  if ( v1 )
  {
    do
      i += v49++ + *(&String + v2++);
    while ( v2 < v1 );
  }
  v3 = v49 + i * v1;
  GetComputerNameA(&Buffer, &nSize);
  wsprintfA(&String1, aS, &Buffer);
  GetUserNameA(&v25, &pcbBuffer);
  wsprintfA(&String2, aS, &v25);
  lstrcatA(&String1, &String2);
  v4 = strlen(&String1);
  v5 = 0;
  if ( v4 )
  {
    v6 = &v11 + v4;
    do
      *(&String2 + v5++) = *v6--;
    while ( v5 < v4 );
  }
  CharUpperA(&String2);
  if ( v4 )
  {
    v7 = 32;
    v8 = (int)&v14;
    for ( i = (int)&v14; ; v8 = i )
    {
      v48 += v45 * (v7 ^ *(_BYTE *)(v8 + v7));
      ++v7;
      if ( v7 - 32 >= v4 )
        break;
    }
  }
  GetDlgItemTextA(hDlg, 1001, &Str, 36);
  v9 = atol(&Str);
  if ( v3 + v48 == (v48 ^ v9) )
  {
    wsprintfA(&Text, aGoodJobS, &String);
    MessageBoxA(hDlg, &Text, aOk, 0);
  }
  else
  {
    SetDlgItemTextA(hDlg, 1001, 0);
  }
}
else
{
  SetDlgItemTextA(hDlg, 1001, 0);
  SetDlgItemTextA(hDlg, 1000, &::String);
}
...

算法都在上面了,直接翻译:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
	char user[256] = {0}; 
	printf("用户名: ");
	scanf("%s", user); getchar(); 
	int lenu = strlen(user), lens;
	if(lenu < 4){
		printf("用户名4位以上");
		getchar(); return 0; 
	}
	
	int i = 0, v49 = 24711447, nSize = 255;
	unsigned int sum = 0, sum1 = 0;
	char cn[256]={0}, cu[256]={0};
	
	do
	  sum += v49++ + user[i++];
	while ( i < lenu );
	sum = v49 + sum * lenu;
	
	GetComputerNameA(cn, &nSize);
	GetUserNameA(cu, &nSize);
	lstrcatA(cn, cu);
	lens = strlen(cn);
	i = 0;
	do
		cu[i] = cn[lens-1-i];
	while ( ++i < lens );
	CharUpperA(cu);
	
	for (i=0; i<lens; i++)
	{
		sum1 += lenu * ((i+32) ^ cu[i]);
	}
	
	sum = (sum + sum1) ^ sum1;
	printf("系列号: %lu", sum);
	
	getchar(); return 0;
}

运行示例:
用户名: keygenme2
系列号: 2026399486

 
 
本节高手录制的视频,点击前往查看

 
 
 
使用的工具连接(工具有点多有点大,可以先下OD,其它的后面慢慢下) 点击前往下载

下面是我的OD的界面布局,我觉得这4个是最常用的界面,其它的我基本上没用到~