networking/nc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*  nc: mini-netcat - built from the ground up for LRP
   3     Copyright (C) 1998  Charles P. Wright
   4
   5     0.0.1   6K      It works.
   6     0.0.2   5K      Smaller and you can also check the exit condition if you wish.
   7     0.0.3           Uses select()
   8
   9     19980918 Busy Boxed! Dave Cinege
  10     19990512 Uses Select. Charles P. Wright
  11     19990513 Fixes stdin stupidity and uses buffers.  Charles P. Wright
  12
  13     This program is free software; you can redistribute it and/or modify
  14     it under the terms of the GNU General Public License as published by
  15     the Free Software Foundation; either version 2 of the License, or
  16     (at your option) any later version.
  17
  18     This program is distributed in the hope that it will be useful,
  19     but WITHOUT ANY WARRANTY; without even the implied warranty of
  20     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21     GNU General Public License for more details.
  22
  23     You should have received a copy of the GNU General Public License
  24     along with this program; if not, write to the Free Software
  25     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 */
  28
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <unistd.h>
  33 #include <signal.h>
  34
  35 #include <sys/types.h>
  36 #include <sys/socket.h>
  37 #include <netinet/in.h>
  38 #include <arpa/inet.h>
  39 #include <netdb.h>
  40 #include <sys/time.h>
  41 #include <sys/ioctl.h>
  42 #include "busybox.h"
  43
  44 #define GAPING_SECURITY_HOLE
  45
  46 static void timeout(int signum)
  47 {
  48         bb_error_msg_and_die("Timed out");
  49 }
  50
  51 int nc_main(int argc, char **argv)
  52 {
  53         int do_listen = 0, lport = 0, delay = 0, wsecs = 0, tmpfd, opt, sfd, x;
  54         char buf[BUFSIZ];
  55 #ifdef GAPING_SECURITY_HOLE
  56         char * pr00gie = NULL;
  57 #endif
  58
  59         struct sockaddr_in address;
  60         struct hostent *hostinfo;
  61
  62         fd_set readfds, testfds;
  63
  64         while ((opt = getopt(argc, argv, "lp:i:e:w:")) > 0) {
  65                 switch (opt) {
  66                         case 'l':
  67                                 do_listen++;
  68                                 break;
  69                         case 'p':
  70                                 lport = bb_lookup_port(optarg, "tcp", 0);
  71                                 break;
  72                         case 'i':
  73                                 delay = atoi(optarg);
  74                                 break;
  75 #ifdef GAPING_SECURITY_HOLE
  76                         case 'e':
  77                                 pr00gie = optarg;
  78                                 break;
  79 #endif
  80                         case 'w':
  81                                 wsecs = atoi(optarg);
  82                                 break;
  83                         default:
  84                                 bb_show_usage();
  85                 }
  86         }
  87
  88 #ifdef GAPING_SECURITY_HOLE
  89         if (pr00gie) {
  90                 /* won't need stdin */
  91                 close (STDIN_FILENO);
  92         }
  93 #endif /* GAPING_SECURITY_HOLE */
  94
  95
  96         if ((do_listen && optind != argc) || (!do_listen && optind + 2 != argc))
  97                 bb_show_usage();
  98
  99         if ((sfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
 100                 bb_perror_msg_and_die("socket");
 101         x = 1;
 102         if (setsockopt (sfd, SOL_SOCKET, SO_REUSEADDR, &x, sizeof (x)) == -1)
 103                 bb_perror_msg_and_die ("reuseaddr failed");
 104         address.sin_family = AF_INET;
 105
 106         if (wsecs) {
 107                 signal(SIGALRM, timeout);
 108                 alarm(wsecs);
 109         }
 110
 111         if (lport != 0) {
 112                 memset(&address.sin_addr, 0, sizeof(address.sin_addr));
 113                 address.sin_port = lport;
 114
 115                 if (bind(sfd, (struct sockaddr *) &address, sizeof(address)) < 0)
 116                         bb_perror_msg_and_die("bind");
 117         }
 118
 119         if (do_listen) {
 120                 socklen_t addrlen = sizeof(address);
 121
 122                 if (listen(sfd, 1) < 0)
 123                         bb_perror_msg_and_die("listen");
 124
 125                 if ((tmpfd = accept(sfd, (struct sockaddr *) &address, &addrlen)) < 0)
 126                         bb_perror_msg_and_die("accept");
 127
 128                 close(sfd);
 129                 sfd = tmpfd;
 130         } else {
 131                 hostinfo = xgethostbyname(argv[optind]);
 132
 133                 address.sin_addr = *(struct in_addr *) *hostinfo->h_addr_list;
 134                 address.sin_port = bb_lookup_port(argv[optind+1], "tcp", 0);
 135
 136                 if (connect(sfd, (struct sockaddr *) &address, sizeof(address)) < 0)
 137                         bb_perror_msg_and_die("connect");
 138         }
 139
 140         if (wsecs) {
 141                 alarm(0);
 142                 signal(SIGALRM, SIG_DFL);
 143         }
 144
 145 #ifdef GAPING_SECURITY_HOLE
 146         /* -e given? */
 147         if (pr00gie) {
 148                 dup2(sfd, 0);
 149                 close(sfd);
 150                 dup2 (0, 1);
 151                 dup2 (0, 2);
 152                 execl (pr00gie, pr00gie, NULL);
 153                 /* Don't print stuff or it will go over the wire.... */
 154                 _exit(-1);
 155         }
 156 #endif /* GAPING_SECURITY_HOLE */
 157
 158
 159         FD_ZERO(&readfds);
 160         FD_SET(sfd, &readfds);
 161         FD_SET(STDIN_FILENO, &readfds);
 162
 163         while (1) {
 164                 int fd;
 165                 int ofd;
 166                 int nread;
 167
 168                 testfds = readfds;
 169
 170                 if (select(FD_SETSIZE, &testfds, NULL, NULL, NULL) < 0)
 171                         bb_perror_msg_and_die("select");
 172
 173                 for (fd = 0; fd < FD_SETSIZE; fd++) {
 174                         if (FD_ISSET(fd, &testfds)) {
 175                                 if ((nread = safe_read(fd, buf, sizeof(buf))) < 0)
 176                                         bb_perror_msg_and_die("read");
 177
 178                                 if (fd == sfd) {
 179                                         if (nread == 0)
 180                                                 exit(0);
 181                                         ofd = STDOUT_FILENO;
 182                                 } else {
 183                                         if (nread == 0)
 184                                                 shutdown(sfd, 1);
 185                                         ofd = sfd;
 186                                 }
 187
 188                                 if (bb_full_write(ofd, buf, nread) < 0)
 189                                         bb_perror_msg_and_die("write");
 190                                 if (delay > 0) {
 191                                         sleep(delay);
 192                                 }
 193                         }
 194                 }
 195         }
 196 }