nmap/nsock/examples/nsock_telnet.c

/***************************************************************************
 * nsock_telnet.c -- A simple "telnet" client -- a trivial example of      *
 * using the nsock parallel socket event library                           *
 *                                                                         *
 ***********************IMPORTANT NSOCK LICENSE TERMS***********************
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 ***************************************************************************/


#include "nsock.h"

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <sys/time.h>

#include <openssl/ssl.h>
#include <openssl/err.h>
/* #include <nbase.h> */

/* from nbase.h */
int socket_errno();


extern char *optarg;
extern int optind;

struct telnet_state {
  nsock_iod tcp_nsi;
  nsock_iod stdin_nsi;
  nsock_event_id latest_readtcpev;
  nsock_event_id latest_readstdinev;
  void *ssl_session;
};

/* Tries to resolve given hostname and stores
   result in ip .  returns 0 if hostname cannot
   be resolved */
int resolve(char *hostname, struct in_addr *ip) {
  struct hostent *h;

  if (!hostname || !*hostname) {  
    fprintf(stderr, "NULL or zero-length hostname passed to resolve().  Quitting.\n");
    exit(1);
  }

  if (inet_aton(hostname, ip))
    return 1; /* damn, that was easy ;) */
  if ((h = gethostbyname(hostname))) {
    memcpy(ip, h->h_addr_list[0], sizeof(struct in_addr));
    return 1;
  }
  return 0;
}

void telnet_event_handler(nsock_pool nsp, nsock_event nse, void *mydata) {

nsock_iod nsi = nse_iod(nse);
enum nse_status status = nse_status(nse);
enum nse_type type = nse_type(nse);
struct sockaddr_in peer;
struct telnet_state *ts;
int nbytes;
char *str;
int read_timeout = -1;
int write_timeout = 2000;

 ts = (struct telnet_state *) mydata; 

 printf("telnet_event_handler: Received callback of type %s with status %s\n",
	 nse_type2str(type), nse_status2str(status));

 if (status == NSE_STATUS_SUCCESS ) { 
   switch(type) {
   case NSE_TYPE_CONNECT:
   case NSE_TYPE_CONNECT_SSL:
     nsi_getlastcommunicationinfo(nsi, NULL, NULL, NULL, (struct sockaddr*)&peer, sizeof peer);
     printf("Successfully connected %sto %s:%hu -- start typing lines\n", (type == NSE_TYPE_CONNECT_SSL)? "(SSL!) " : "", inet_ntoa(peer.sin_addr), peer.sin_port);
     /* First of all, lets add STDIN to our list of watched filehandles */
     if ((ts->stdin_nsi = nsi_new2(nsp, STDIN_FILENO, NULL)) == NULL) {
       fprintf(stderr, "Failed to create stdin msi\n");
       exit(1);
     }

     /* Now lets read from stdin and the network, line buffered (by nsock) */
     ts->latest_readtcpev = nsock_readlines(nsp, ts->tcp_nsi, telnet_event_handler, read_timeout, ts, 1);
     ts->latest_readstdinev = nsock_readlines(nsp, ts->stdin_nsi, telnet_event_handler, read_timeout, ts, 1);
     break;     
   case NSE_TYPE_READ:
     str = nse_readbuf(nse, &nbytes);
     if (nsi == ts->tcp_nsi) {
       printf("%s", str);
       /*       printf("Read from tcp socket (%d bytes):\n%s", nbytes, str); */
       ts->latest_readtcpev = nsock_readlines(nsp, ts->tcp_nsi, telnet_event_handler, read_timeout, ts, 1);
     } else {
       /*       printf("Read from  stdin (%d bytes):\n%s", nbytes, str); */
       nsock_write(nsp, ts->tcp_nsi, telnet_event_handler, write_timeout, ts, str, nbytes);
       ts->latest_readstdinev = nsock_readlines(nsp, ts->stdin_nsi, telnet_event_handler, read_timeout, ts, 1);
     }
     break;
   case NSE_TYPE_WRITE:
     /* Nothing to do, really */
     break;
   case NSE_TYPE_TIMER:
     break;
   default:
     fprintf(stderr, "telnet_event_handler: Got bogus type -- quitting\n");
     exit(1);
     break;
   }
 } else if (status == NSE_STATUS_EOF) {
   printf("Got EOF from %s\nCancelling outstanding readevents.\n", (nsi == ts->tcp_nsi)? "tcp socket" : "stdin");
   /* One of these is the event I am currently handling!  But I wanted to
      be evil when testing this out... */
   if (nsock_event_cancel(nsp, ts->latest_readtcpev, 1) != 0) {
     printf("Cancelled tcp event: %li\n", ts->latest_readtcpev);
   }
   if (nsock_event_cancel(nsp, ts->latest_readstdinev, 1) != 0) {
     printf("Cancelled stdin event: %li\n", ts->latest_readstdinev);
   }
 } else if (status == NSE_STATUS_ERROR) {
   if (nsi_checkssl(nsi)) {
     printf("SSL %s failed: %s\n", nse_type2str(type), ERR_error_string(ERR_get_error(), NULL));
   } else {
     printf("%s failed: %s\n", nse_type2str(type), strerror(socket_errno()));
   }
 }
 return;
}

void usage() {
  fprintf(stderr, "\nUsage: nsock_telnet [-s] [-t tracelevel] <hostnameorip> [portnum]\n"
	  "       Where -s enables SSL for the connection\n\n");
  exit(1);
}

int main(int argc, char *argv[]) {
  struct in_addr target;
  nsock_pool nsp;
  nsock_event_id ev;
  unsigned short portno;
  enum nsock_loopstatus loopret;
  struct telnet_state ts;
  int c;
  int usessl = 0;
  int tracelevel = 0;
  struct timeval now;
  struct sockaddr_in taddr;

  ts.stdin_nsi = NULL;

  while((c = getopt(argc, argv, "st:")) != -1) {
    switch(c) {
    case 's':
      usessl = 1;
      break;
    case 't':
      tracelevel = atoi(optarg);
      assert(tracelevel >= 0);
      break;
    default:
      usage(); break;
    }
  }

  if (argc - optind <= 0 || argc - optind > 2)
    usage();


  if (!resolve(argv[optind], &target)) {
    fprintf(stderr, "Failed to resolve target host: %s\nQUITTING.\n", argv[optind]);
    exit(1);
  }
  optind++;

  if (optind < argc)
    portno = atoi(argv[optind]);
  else portno = 23;

  /* OK, we start with creating a p00l */
  if ((nsp = nsp_new(NULL)) == NULL) {
    fprintf(stderr, "Failed to create new pool.  QUITTING.\n");
    exit(1);
  }

  gettimeofday(&now, NULL);

  nsp_settrace(nsp, NULL, tracelevel, &now);

  if ((ts.tcp_nsi = nsi_new(nsp, NULL)) == NULL) {
    fprintf(stderr, "Failed to create new nsock_iod.  QUITTING.\n");
    exit(1);
  }

  taddr.sin_family = AF_INET;
  taddr.sin_addr = target;
  taddr.sin_port = portno;

  if (usessl)
  {
    ts.ssl_session = NULL;
    ev = nsock_connect_ssl(nsp, ts.tcp_nsi, telnet_event_handler, 10000, &ts, (struct sockaddr *)&taddr, sizeof taddr, IPPROTO_TCP, portno, ts.ssl_session);
  }
  else
    ev = nsock_connect_tcp(nsp, ts.tcp_nsi, telnet_event_handler, 10000, &ts, (struct sockaddr *)&taddr, sizeof taddr, portno);

  printf("The event id is %lu -- initiating l00p\n", ev);

  /* Now lets get this party started right! */
  loopret = nsock_loop(nsp, -1);

  printf("nsock_loop returned %d\n", (int) loopret);

  return 0;
}