OverTheWire: Vortex Level0

So what’s this whole thing about? “The wargames offered by the OverTheWire community can help you to learn and practice security concepts in the form of funfilled games.” by OverTheWire.org. So I started with Vortex and coded an example how to read 4 integers from server, sum them up, send result to server and get the login information back from server again. Sounds quite simple. I admit I had to refresh my knowledge about linux socket programming and go through some coding examples. And here is my solution for level0:

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 * ========================================================
 *
 *       Filename:  vortex_level0.c  
 *
 *    Description:  Read 4 integers from vortex.labs.pulltheplug.org:5842, sum
 *                  them up, send result to server and get login data
 *
 *        Version:  1.0
 *        Created:  05/20/2009 08:53:53 PM
 *       Compiler:  gcc
 *
 *         Author:  Victor Dorneanu 
 *
 * ========================================================
 */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define HOSTNAME "vortex.labs.pulltheplug.org"
#define PORT "5842"

void die(char *mess) { perror(mess); exit(1); }

int main(int argc, char *argv[]) {
   int sock, rv;
   struct addrinfo hints, *servinfo, *p;
   unsigned int buffer[4];
   char login_data[200];
   unsigned int received = 0;
   int i, bytes;

   /*  Construct the server addrinfo structure */
   memset(&hints, 0, sizeof hints);         /*  Clear struct */
   hints.ai_family = AF_UNSPEC;             /*  IPv4 or IPv6 */
   hints.ai_socktype = SOCK_STREAM;

   if ((rv = getaddrinfo(HOSTNAME, PORT, &hints, &servinfo)) != 0) {
		fprintf(stderr, "getaddrinfo: %s
", gai_strerror(rv));
		return 1;
	}

	// loop through all the results and make a socket
	for(p = servinfo; p != NULL; p = p-&gt;ai_next) {
		if ((sock = socket(p-&gt;ai_family, p-&gt;ai_socktype, p-&gt;ai_protocol)) == -1) {
			die("Couldn't create socket");
			continue;
		}
		break;
	}

   /*  Establish  connection */
   if (connect(sock, servinfo-&gt;ai_addr, servinfo-&gt;ai_addrlen) &lt; 0) {
      die("Failed to connect to server");
   }

   /* Read 4 integers from server */
   for (i = 0; i &lt; 4; i ++) 
      read(sock, &buffer[i], 4);

   /* Sum up integers */
   received = 0;
   for(i=0; i &lt; 4; i++)  
      received += buffer[i];

   /*  Send sum to the server */
   if (send(sock, &received, sizeof(received), 0) != sizeof received) {
      die("Mismatch in number of sent bytes");
   }

   /* Read login data */
   if (recv(sock, &login_data, 200, 0) &lt; 1) {
      die("Mismatch in number of received bytes");
   }

   fprintf(stdout,"login: %s
", login_data);

   /*  Free addrinfo structure */
   freeaddrinfo(servinfo);

   /* Close connection */
   close(sock);
   exit(0);
}