networking/nc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * nc: mini-netcat - built from the ground up for LRP
   4  *
   5  * Copyright (C) 1998, 1999  Charles P. Wright
   6  * Copyright (C) 1998  Dave Cinege
   7  *
   8  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   9  */
  10 //config:config NC
  11 //config:       bool "nc (11 kb)"
  12 //config:       default y
  13 //config:       help
  14 //config:       A simple Unix utility which reads and writes data across network
  15 //config:       connections.
  16 //config:
  17 //config:config NETCAT
  18 //config:       bool "netcat (11 kb)"
  19 //config:       default n
  20 //config:       help
  21 //config:       Alias to nc.
  22 //config:
  23 //config:config NC_SERVER
  24 //config:       bool "Netcat server options (-l)"
  25 //config:       default y
  26 //config:       depends on NC || NETCAT
  27 //config:       help
  28 //config:       Allow netcat to act as a server.
  29 //config:
  30 //config:config NC_EXTRA
  31 //config:       bool "Netcat extensions (-eiw and -f FILE)"
  32 //config:       default y
  33 //config:       depends on NC || NETCAT
  34 //config:       help
  35 //config:       Add -e (support for executing the rest of the command line after
  36 //config:       making or receiving a successful connection), -i (delay interval for
  37 //config:       lines sent), -w (timeout for initial connection).
  38 //config:
  39 //config:config NC_110_COMPAT
  40 //config:       bool "Netcat 1.10 compatibility (+2.5k)"
  41 //config:       default y
  42 //config:       depends on NC || NETCAT
  43 //config:       help
  44 //config:       This option makes nc closely follow original nc-1.10.
  45 //config:       The code is about 2.5k bigger. It enables
  46 //config:       -s ADDR, -n, -u, -v, -o FILE, -z options, but loses
  47 //config:       busybox-specific extensions: -f FILE.
  48
  49 //applet:IF_NC(APPLET(nc, BB_DIR_USR_BIN, BB_SUID_DROP))
  50 //                 APPLET_ODDNAME:name    main location        suid_type     help
  51 //applet:IF_NETCAT(APPLET_ODDNAME(netcat, nc,  BB_DIR_USR_BIN, BB_SUID_DROP, nc))
  52
  53 //kbuild:lib-$(CONFIG_NC) += nc.o
  54 //kbuild:lib-$(CONFIG_NETCAT) += nc.o
  55
  56 #include "libbb.h"
  57 #include "common_bufsiz.h"
  58 #if ENABLE_NC_110_COMPAT
  59 # include "nc_bloaty.c"
  60 #else
  61
  62 //usage:#if !ENABLE_NC_110_COMPAT
  63 //usage:
  64 //usage:#if ENABLE_NC_SERVER || ENABLE_NC_EXTRA
  65 //usage:#define NC_OPTIONS_STR "\n"
  66 //usage:#else
  67 //usage:#define NC_OPTIONS_STR
  68 //usage:#endif
  69 //usage:
  70 //usage:#define nc_trivial_usage
  71 //usage:        IF_NC_EXTRA("[-iN] [-wN] ")IF_NC_SERVER("[-l] [-p PORT] ")
  72 //usage:       "["IF_NC_EXTRA("-f FILE|")"IPADDR PORT]"IF_NC_EXTRA(" [-e PROG]")
  73 //usage:#define nc_full_usage "\n\n"
  74 //usage:       "Open a pipe to IP:PORT" IF_NC_EXTRA(" or FILE")
  75 //usage:        NC_OPTIONS_STR
  76 //usage:        IF_NC_SERVER(
  77 //usage:     "\n        -l      Listen mode, for inbound connects"
  78 //usage:        IF_NC_EXTRA(
  79 //usage:     "\n                (use -ll with -e for persistent server)"
  80 //usage:        )
  81 //usage:     "\n        -p PORT Local port"
  82 //usage:        )
  83 //usage:        IF_NC_EXTRA(
  84 //usage:     "\n        -w SEC  Connect timeout"
  85 //usage:     "\n        -i SEC  Delay interval for lines sent"
  86 //usage:     "\n        -f FILE Use file (ala /dev/ttyS0) instead of network"
  87 //usage:     "\n        -e PROG Run PROG after connect"
  88 //usage:        )
  89 //usage:
  90 //usage:#define nc_notes_usage ""
  91 //usage:        IF_NC_EXTRA(
  92 //usage:       "To use netcat as a terminal emulator on a serial port:\n\n"
  93 //usage:       "$ stty 115200 -F /dev/ttyS0\n"
  94 //usage:       "$ stty raw -echo -ctlecho && nc -f /dev/ttyS0\n"
  95 //usage:        )
  96 //usage:
  97 //usage:#define nc_example_usage
  98 //usage:       "$ nc foobar.somedomain.com 25\n"
  99 //usage:       "220 foobar ESMTP Exim 3.12 #1 Sat, 15 Apr 2000 00:03:02 -0600\n"
 100 //usage:       "help\n"
 101 //usage:       "214-Commands supported:\n"
 102 //usage:       "214-    HELO EHLO MAIL RCPT DATA AUTH\n"
 103 //usage:       "214     NOOP QUIT RSET HELP\n"
 104 //usage:       "quit\n"
 105 //usage:       "221 foobar closing connection\n"
 106 //usage:
 107 //usage:#endif
 108
 109 /* Lots of small differences in features
 110  * when compared to "standard" nc
 111  */
 112
 113 static void timeout(int signum UNUSED_PARAM)
 114 {
 115         bb_error_msg_and_die("timed out");
 116 }
 117
 118 int nc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 119 int nc_main(int argc, char **argv)
 120 {
 121         /* sfd sits _here_ only because of "repeat" option (-l -l). */
 122         int sfd = sfd; /* for gcc */
 123         int cfd = 0;
 124         unsigned lport = 0;
 125         IF_NOT_NC_SERVER(const) unsigned do_listen = 0;
 126         IF_NOT_NC_EXTRA (const) unsigned wsecs = 0;
 127         IF_NOT_NC_EXTRA (const) unsigned delay = 0;
 128         IF_NOT_NC_EXTRA (const int execparam = 0;)
 129         IF_NC_EXTRA     (char **execparam = NULL;)
 130         struct pollfd pfds[2];
 131         int opt; /* must be signed (getopt returns -1) */
 132
 133         if (ENABLE_NC_SERVER || ENABLE_NC_EXTRA) {
 134                 /* getopt32 is _almost_ usable:
 135                 ** it cannot handle "... -e PROG -prog-opt" */
 136                 while ((opt = getopt(argc, argv,
 137                         "" IF_NC_SERVER("lp:") IF_NC_EXTRA("w:i:f:e:") )) > 0
 138                 ) {
 139                         if (ENABLE_NC_SERVER && opt == 'l')
 140                                 IF_NC_SERVER(do_listen++);
 141                         else if (ENABLE_NC_SERVER && opt == 'p')
 142                                 IF_NC_SERVER(lport = bb_lookup_port(optarg, "tcp", 0));
 143                         else if (ENABLE_NC_EXTRA && opt == 'w')
 144                                 IF_NC_EXTRA( wsecs = xatou(optarg));
 145                         else if (ENABLE_NC_EXTRA && opt == 'i')
 146                                 IF_NC_EXTRA( delay = xatou(optarg));
 147                         else if (ENABLE_NC_EXTRA && opt == 'f')
 148                                 IF_NC_EXTRA( cfd = xopen(optarg, O_RDWR));
 149                         else if (ENABLE_NC_EXTRA && opt == 'e' && optind <= argc) {
 150                                 /* We cannot just 'break'. We should let getopt finish.
 151                                 ** Or else we won't be able to find where
 152                                 ** 'host' and 'port' params are
 153                                 ** (think "nc -w 60 host port -e PROG"). */
 154                                 IF_NC_EXTRA(
 155                                         char **p;
 156                                         // +2: one for progname (optarg) and one for NULL
 157                                         execparam = xzalloc(sizeof(char*) * (argc - optind + 2));
 158                                         p = execparam;
 159                                         *p++ = optarg;
 160                                         while (optind < argc) {
 161                                                 *p++ = argv[optind++];
 162                                         }
 163                                 )
 164                                 /* optind points to argv[argc] (NULL) now.
 165                                 ** FIXME: we assume that getopt will not count options
 166                                 ** possibly present on "-e PROG ARGS" and will not
 167                                 ** include them into final value of optind
 168                                 ** which is to be used ...  */
 169                         } else bb_show_usage();
 170                 }
 171                 argv += optind; /* ... here! */
 172                 argc -= optind;
 173                 // -l and -f don't mix
 174                 if (do_listen && cfd) bb_show_usage();
 175                 // File mode needs need zero arguments, listen mode needs zero or one,
 176                 // client mode needs one or two
 177                 if (cfd) {
 178                         if (argc) bb_show_usage();
 179                 } else if (do_listen) {
 180                         if (argc > 1) bb_show_usage();
 181                 } else {
 182                         if (!argc || argc > 2) bb_show_usage();
 183                 }
 184         } else {
 185                 if (argc != 3) bb_show_usage();
 186                 argc--;
 187                 argv++;
 188         }
 189
 190         if (wsecs) {
 191                 signal(SIGALRM, timeout);
 192                 alarm(wsecs);
 193         }
 194
 195         if (!cfd) {
 196                 if (do_listen) {
 197                         sfd = create_and_bind_stream_or_die(argv[0], lport);
 198                         xlisten(sfd, do_listen); /* can be > 1 */
 199 #if 0  /* nc-1.10 does not do this (without -v) */
 200                         /* If we didn't specify a port number,
 201                          * query and print it after listen() */
 202                         if (!lport) {
 203                                 len_and_sockaddr lsa;
 204                                 lsa.len = LSA_SIZEOF_SA;
 205                                 getsockname(sfd, &lsa.u.sa, &lsa.len);
 206                                 lport = get_nport(&lsa.u.sa);
 207                                 fdprintf(2, "%d\n", ntohs(lport));
 208                         }
 209 #endif
 210                         close_on_exec_on(sfd);
 211  accept_again:
 212                         cfd = accept(sfd, NULL, 0);
 213                         if (cfd < 0)
 214                                 bb_perror_msg_and_die("accept");
 215                         if (!execparam)
 216                                 close(sfd);
 217                 } else {
 218                         cfd = create_and_connect_stream_or_die(argv[0],
 219                                 argv[1] ? bb_lookup_port(argv[1], "tcp", 0) : 0);
 220                 }
 221         }
 222
 223         if (wsecs) {
 224                 alarm(0);
 225                 /* Non-ignored signals revert to SIG_DFL on exec anyway */
 226                 /*signal(SIGALRM, SIG_DFL);*/
 227         }
 228
 229         /* -e given? */
 230         if (execparam) {
 231                 pid_t pid;
 232                 /* With more than one -l, repeatedly act as server */
 233                 if (do_listen > 1 && (pid = xvfork()) != 0) {
 234                         /* parent */
 235                         /* prevent zombies */
 236                         signal(SIGCHLD, SIG_IGN);
 237                         close(cfd);
 238                         goto accept_again;
 239                 }
 240                 /* child, or main thread if only one -l */
 241                 xmove_fd(cfd, 0);
 242                 xdup2(0, 1);
 243                 /*xdup2(0, 2); - original nc 1.10 does this, we don't */
 244                 IF_NC_EXTRA(BB_EXECVP(execparam[0], execparam);)
 245                 IF_NC_EXTRA(bb_perror_msg_and_die("can't execute '%s'", execparam[0]);)
 246         }
 247
 248         /* loop copying stdin to cfd, and cfd to stdout */
 249
 250         pfds[0].fd = STDIN_FILENO;
 251         pfds[0].events = POLLIN;
 252         pfds[1].fd = cfd;
 253         pfds[1].events = POLLIN;
 254
 255 #define iobuf bb_common_bufsiz1
 256         setup_common_bufsiz();
 257         for (;;) {
 258                 int fdidx;
 259                 int ofd;
 260                 int nread;
 261
 262                 if (safe_poll(pfds, 2, -1) < 0)
 263                         bb_perror_msg_and_die("poll");
 264
 265                 fdidx = 0;
 266                 while (1) {
 267                         if (pfds[fdidx].revents) {
 268                                 nread = safe_read(pfds[fdidx].fd, iobuf, COMMON_BUFSIZE);
 269                                 if (fdidx != 0) {
 270                                         if (nread < 1)
 271                                                 exit(EXIT_SUCCESS);
 272                                         ofd = STDOUT_FILENO;
 273                                 } else {
 274                                         if (nread < 1) {
 275                                                 /* Close outgoing half-connection so they get EOF,
 276                                                  * but leave incoming alone so we can see response */
 277                                                 shutdown(cfd, SHUT_WR);
 278                                                 pfds[0].fd = -1;
 279                                         }
 280                                         ofd = cfd;
 281                                 }
 282                                 xwrite(ofd, iobuf, nread);
 283                                 if (delay > 0)
 284                                         sleep(delay);
 285                         }
 286                         if (fdidx == 1)
 287                                 break;
 288                         fdidx++;
 289                 }
 290         }
 291 }
 292 #endif