[Pwnable.kr] dragon

by yiz96 04. 3 月 2016 pwnable writeup 0
略需要逆向的一道题，是一个打怪兽的小游戏。首先F5看一下代码（只贴关键部分）
int __cdecl main(int argc, const char **argv, const char **envp)
{
  setvbuf(stdout, 0, 2, 0);
  setvbuf(stdin, 0, 2, 0);
  puts("Welcome to Dragon Hunter!");
  PlayGame();
  return 0;
}

int PlayGame()
{
  int result; // eax@1

  while ( 1 )
  {
    while ( 1 )
    {
      puts("Choose Your Hero\n[ 1 ] Priest\n[ 2 ] Knight");
      result = GetChoice();
      if ( result != 1 && result != 2 )
        break;
      FightDragon(result);
    }
    if ( result != 3 )
      break;
    SecretLevel();
  }
  return result;
}

void __cdecl FightDragon(int a1)
{
  char v1; // al@1
  void *v2; // ST1C_4@10
  int v3; // [esp+10h] [ebp-18h]@7
  _DWORD *ptr; // [esp+14h] [ebp-14h]@1
  _DWORD *v5; // [esp+18h] [ebp-10h]@1

  ptr = malloc(0x10u);
  v5 = malloc(0x10u);
  v1 = Count++;
  if ( v1 & 1 )
  {
    v5[1] = 1;
    *((_BYTE *)v5 + 8) = 80;
    *((_BYTE *)v5 + 9) = 4;
    v5[3] = 10;
    *v5 = PrintMonsterInfo;
    puts("Mama Dragon Has Appeared!");
  }
  else
  {
    v5[1] = 0;
    *((_BYTE *)v5 + 8) = 50;
    *((_BYTE *)v5 + 9) = 5;
    v5[3] = 30;
    *v5 = PrintMonsterInfo;
    puts("Baby Dragon Has Appeared!");
  }
  if ( a1 == 1 )
  {
    *ptr = 1;
    ptr[1] = 42;
    ptr[2] = 50;
    ptr[3] = PrintPlayerInfo;
    v3 = PriestAttack((int)ptr, v5);
  }
  else
  {
    if ( a1 != 2 )
      return;
    *ptr = 2;
    ptr[1] = 50;
    ptr[2] = 0;
    ptr[3] = PrintPlayerInfo;
    v3 = KnightAttack((int)ptr, v5);
  }
  if ( v3 )
  {
    puts("Well Done Hero! You Killed The Dragon!");
    puts("The World Will Remember You As:");
    v2 = malloc(0x10u);
    __isoc99_scanf("%16s", v2);
    puts("And The Dragon You Have Defeated Was Called:");
    ((void (__cdecl *)(_DWORD *))*v5)(v5);
  }
  else
  {
    puts("\nYou Have Been Defeated!");
  }
  free(ptr);
}

int __cdecl PriestAttack(int a1, void *ptr)
{
  int v2; // eax@1

  do
  {
    (*(void (__cdecl **)(void *))ptr)(ptr);
    (*(void (__cdecl **)(int))(a1 + 12))(a1);
    v2 = GetChoice();
    switch ( v2 )
    {
      case 2:
        puts("Clarity! Your Mana Has Been Refreshed");
        *(_DWORD *)(a1 + 8) = 50;
        printf("But The Dragon Deals %d Damage To You!\n", *((_DWORD *)ptr + 3));
        *(_DWORD *)(a1 + 4) -= *((_DWORD *)ptr + 3);
        printf("And The Dragon Heals %d HP!\n", *((char *)ptr + 9));
        *((_BYTE *)ptr + 8) += *((_BYTE *)ptr + 9);
        break;
      case 3:
        if ( *(_DWORD *)(a1 + 8) <= 24 )
        {
          puts("Not Enough MP!");
        }
        else
        {
          puts("HolyShield! You Are Temporarily Invincible...");
          printf("But The Dragon Heals %d HP!\n", *((char *)ptr + 9));
          *((_BYTE *)ptr + 8) += *((_BYTE *)ptr + 9);
          *(_DWORD *)(a1 + 8) -= 25;
        }
        break;
      case 1:
        if ( *(_DWORD *)(a1 + 8) <= 9 )
        {
          puts("Not Enough MP!");
        }
        else
        {
          printf("Holy Bolt Deals %d Damage To The Dragon!\n", 20);
          *((_BYTE *)ptr + 8) -= 20;
          *(_DWORD *)(a1 + 8) -= 10;
          printf("But The Dragon Deals %d Damage To You!\n", *((_DWORD *)ptr + 3));
          *(_DWORD *)(a1 + 4) -= *((_DWORD *)ptr + 3);
          printf("And The Dragon Heals %d HP!\n", *((char *)ptr + 9));
          *((_BYTE *)ptr + 8) += *((_BYTE *)ptr + 9);
        }
        break;
    }
    if ( *(_DWORD *)(a1 + 4) <= 0 )
    {
      free(ptr);
      return 0;
    }
  }
  while ( *((_BYTE *)ptr + 8) > 0 );
  free(ptr);
  return 1;
}