networking/nc.c

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