vortex0.c

#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>

#define HOST "vortex.labs.overthewire.org"
#define PORT "5842"

int main() {
  int error;
  struct addrinfo hints;
  struct addrinfo *ai, *aiptr;
  char addrstr[INET_ADDRSTRLEN];
  int fd;
  uint32_t ints[4];
  int i;
  uint32_t sum;
  char buf[100];

  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;

  if ((error = getaddrinfo(HOST, PORT, &hints, &ai)) < 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(error));
    goto getaddrinfo_failed;
  }

  for (aiptr = ai; aiptr != NULL; aiptr = aiptr->ai_next) {
    if ((fd = socket(ai->ai_family, ai->ai_socktype,
                     ai->ai_protocol)) >= 0)
      break;
  }

  if (fd < 0) {
    fprintf(stderr, "socket: %s\n", strerror(errno));
    goto socket_failed;
  }

  if (connect(fd, ai->ai_addr, ai->ai_addrlen) < 0) {
    fprintf(stderr, "connect: %s\n", strerror(errno));
    goto exit;
  }

  if (inet_ntop(ai->ai_family, ai->ai_addr, addrstr,
                sizeof(addrstr)) != NULL)
    printf("Connected to "HOST" (%s) at port "PORT"\n", addrstr);

  for (i = 0; i < 4; i++) {
    if (recv(fd, &ints[i], sizeof(*ints), 0) < 0) {
      fprintf(stderr, "recv: %s\n", strerror(errno));
      goto exit;
    }
  }

  sum = 0;
  for (i = 0; i < 4; i++)
    sum += ints[i];

  if (send(fd, &sum, sizeof(sum), 0) < 0) {
    fprintf(stderr, "send: %s\n", strerror(errno));
    goto exit;
  }

  memset(buf, 0, sizeof(buf));
  if (recv(fd, buf, sizeof(buf), 0) < 0) {
    goto exit;
  }

  printf("%s\n", buf);

exit:
  close(fd);
  freeaddrinfo(ai);
  return 0;

socket_failed:
  freeaddrinfo(ai);
getaddrinfo_failed:
  exit(EXIT_FAILURE);
}