tcp_stealth_client.c

#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/select.h>

#define TCP_STEALTH                      26
#define TCP_STEALTH_INTEGRITY            27
#define SERVER_ADDR                      "127.0.0.1"

int main(int argc, char **argv)
{
  int sock, retval;
  struct sockaddr_in addr;
  unsigned char buf[512];
  fd_set rfds;

  addr.sin_family = AF_INET;
  addr.sin_port   = htons(8080);
  inet_aton(SERVER_ADDR, &addr.sin_addr);

  char secret[64] = "C007 magic that cannot be bork'd.";
  char payload[4] = "1234";

  sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (sock < 0) {
    printf("socket() failed, %s\n", strerror(errno));
    return 1;
  }

  if (setsockopt(sock, IPPROTO_TCP, TCP_STEALTH, secret, sizeof(secret))) {
    printf("setsockopt() failed, %s\n", strerror(errno));
    return 1;
  }

  if (setsockopt(sock, IPPROTO_TCP, TCP_STEALTH_INTEGRITY, payload,
		 sizeof(payload))) {
    printf("setsockopt() failed, %s\n", strerror(errno));
    return 1;
  }

  if (connect(sock, (struct sockaddr*) &addr, sizeof(addr))) {
    printf("connect() failed, %s", strerror(errno));
    return 1;
  }


  do {
    FD_ZERO(&rfds);
    FD_SET(STDIN_FILENO, &rfds);
    FD_SET(sock, &rfds);

    select(sock + 1, &rfds, NULL, NULL, NULL);

    if (FD_ISSET(STDIN_FILENO, &rfds)) {
      int len = read(STDIN_FILENO, buf, sizeof(buf));
      write(sock, buf, len);
    }
    if (FD_ISSET(sock, &rfds)) {
      int len = read(sock, buf, sizeof(buf));
      if (!len) {
	puts("Peer closed connection.");
	break;
      }
      printf("%s", buf);
    }

  } while (retval > 0);

  return 0;
}