mdw@git.distorted.org.uk Git - fwd/blob - fw.c

   1 /* -*-c-*-
   2  *
   3  * $Id: fw.c,v 1.6 1999/12/22 15:44:10 mdw Exp $
   4  *
   5  * Port forwarding thingy
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of the `fw' port forwarder.
  13  *
  14  * `fw' is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * `fw' is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with `fw'; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: fw.c,v $
  32  * Revision 1.6  1999/12/22 15:44:10  mdw
  33  * Make syslog a separate option, and do it better.
  34  *
  35  * Revision 1.5  1999/10/22 22:47:50  mdw
  36  * Grammar changes.  Also, don't enable SIGINT if it's currently ignored.
  37  *
  38  * Revision 1.4  1999/10/10 16:46:12  mdw
  39  * New resolver to initialize.  Also, include options for grammar and
  40  * options references.
  41  *
  42  * Revision 1.3  1999/07/26 23:30:42  mdw
  43  * Major reconstruction work for new design.
  44  *
  45  * Revision 1.2  1999/07/03 13:55:17  mdw
  46  * Various changes.  Add configuration grammar to help text.  Change to
  47  * root directory and open syslog when forking into background.
  48  *
  49  * Revision 1.1.1.1  1999/07/01 08:56:23  mdw
  50  * Initial revision.
  51  *
  52  */
  53
  54 /*----- Header files ------------------------------------------------------*/
  55
  56 #include "config.h"
  57
  58 #include <ctype.h>
  59 #include <errno.h>
  60 #include <signal.h>
  61 #include <stdarg.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64 #include <string.h>
  65 #include <time.h>
  66
  67 #include <unistd.h>
  68 #include <syslog.h>
  69
  70 #include <mLib/bres.h>
  71 #include <mLib/dstr.h>
  72 #include <mLib/mdwopt.h>
  73 #include <mLib/quis.h>
  74 #include <mLib/report.h>
  75 #include <mLib/sel.h>
  76 #include <mLib/sig.h>
  77 #include <mLib/sub.h>
  78
  79 #include "conf.h"
  80 #include "endpt.h"
  81 #include "exec.h"
  82 #include "fattr.h"
  83 #include "fw.h"
  84 #include "scan.h"
  85 #include "source.h"
  86
  87 /*----- Global variables --------------------------------------------------*/
  88
  89 sel_state *sel;                         /* Multiplexor for nonblocking I/O */
  90
  91 /*----- Static variables --------------------------------------------------*/
  92
  93 static unsigned flags = 0;              /* Global state flags */
  94 static unsigned active = 0;             /* Number of active things */
  95
  96 #define FW_SYSLOG 1u
  97 #define FW_QUIET 2u
  98 #define FW_SET 4u
  99
 100 /*----- Main code ---------------------------------------------------------*/
 101
 102 /* --- @fw_log@ --- *
 103  *
 104  * Arguments:   @time_t t@ = when the connection occurred or (@-1@)
 105  *              @const char *fmt@ = format string to fill in
 106  *              @...@ = other arguments
 107  *
 108  * Returns:     ---
 109  *
 110  * Use:         Logs a connection.
 111  */
 112
 113 void fw_log(time_t t, const char *fmt, ...)
 114 {
 115   struct tm *tm;
 116   dstr d = DSTR_INIT;
 117   va_list ap;
 118
 119   if (flags & FW_QUIET)
 120     return;
 121
 122   if (t == -1)
 123     t = time(0);
 124   tm = localtime(&t);
 125   DENSURE(&d, 64);
 126   d.len += strftime(d.buf, d.sz, "%Y-%m-%d %H:%M:%S ", tm);
 127   va_start(ap, fmt);
 128   dstr_vputf(&d, fmt, ap);
 129   va_end(ap);
 130   if (flags & FW_SYSLOG)
 131     syslog(LOG_NOTICE, "%s", d.buf);
 132   else {
 133     DPUTC(&d, '\n');
 134     dstr_write(&d, stderr);
 135   }
 136   DDESTROY(&d);
 137 }
 138
 139 /* --- @fw_inc@, @fw_dec@ --- *
 140  *
 141  * Arguments:   ---
 142  *
 143  * Returns:     ---
 144  *
 145  * Use:         Increments or decrements the active thing count.  `fw' won't
 146  *              quit while there are active things.
 147  */
 148
 149 void fw_inc(void) { flags |= FW_SET; active++; }
 150 void fw_dec(void) { if (active) active--; }
 151
 152 /* --- @fw_exit@ --- *
 153  *
 154  * Arguments:   ---
 155  *
 156  * Returns:     ---
 157  *
 158  * Use:         Exits when appropriate.
 159  */
 160
 161 static void fw_exit(void)
 162 {
 163   endpt_killall();
 164   source_killall();
 165 }
 166
 167 /* --- @fw_tidy@ --- *
 168  *
 169  * Arguments:   @int n@ = signal number
 170  *              @void *p@ = an uninteresting argument
 171  *
 172  * Returns:     ---
 173  *
 174  * Use:         Handles various signals and causes a clean tidy-up.
 175  */
 176
 177 static void fw_tidy(int n, void *p)
 178 {
 179   const char *sn = "unexpected signal (bug!)";
 180   if (n == SIGTERM)
 181     sn = "SIGTERM";
 182   else if (n == SIGINT)
 183     sn = "SIGINT";
 184
 185   fw_log(-1, "closing down on %s", sn);
 186   fw_exit();
 187 }
 188
 189 /* --- Standard GNU help options --- */
 190
 191 static void version(FILE *fp)
 192 {
 193   pquis(fp, "$ version " VERSION "\n");
 194 }
 195
 196 static void usage(FILE *fp)
 197 {
 198   pquis(fp, "Usage: $ [-dql] [-f file] [config statements...]\n");
 199 }
 200
 201 static void help(FILE *fp)
 202 {
 203   version(fp);
 204   fputc('\n', fp);
 205   usage(fp);
 206   pquis(fp, "\n\
 207 An excessively full-featured port-forwarder, which subsumes large chunks\n\
 208 of the functionality of inetd, netcat, and normal cat.  Options available\n\
 209 are:\n\
 210 \n\
 211 -h, --help        Display this help message.\n\
 212 -v, --version     Display the program's version number.\n\
 213 -u, --usage       Display a terse usage summary.\n\
 214 \n\
 215 -g, --grammar     Show a summary of the configuration language.\n\
 216 -o, --options     Show a summary of the source and target options.\n\
 217 \n\
 218 -f, --file=FILE   Read configuration from a file.\n\
 219 -q, --quiet       Don't emit any logging information.\n\
 220 -d, --daemon      Fork into background after initializing.\n\
 221 -l, --syslog      Send log output to the system logger.\n\
 222 \n\
 223 Configuration may be supplied in one or more configuration files, or on\n\
 224 the command line (or both).  If no `-f' option is present, and no\n\
 225 configuration is given on the command line, the standard input stream is\n\
 226 read.\n\
 227 \n\
 228 Configuration is free-form.  Comments begin with a `#' character and\n\
 229 continue to the end of the line.  Each command line argument is considered\n\
 230 to be a separate line.\n\
 231 \n\
 232 The grammar is fairly complicated.  For a summary, run `$ --grammar'.\n\
 233 For a summary of the various options, run `$ --options'.\n\
 234 ");
 235 }
 236
 237 /* --- Other helpful options --- */
 238
 239 static void grammar(FILE *fp)
 240 {
 241   version(fp);
 242   pquis(fp, "\n\
 243 Grammar summary\n\
 244 \n\
 245 Basic syntax\n\
 246         file ::= empty | file stmt [`;']\n\
 247         stmt ::= option-stmt | fw-stmt\n\
 248         fw-stmt ::= `fw' source options [`to'|`->'] target options\n\
 249         options ::= `{' option-seq `}'\n\
 250         option-seq ::= empty | option-stmt [`;'] option-seq\n\
 251 \n\
 252 Option syntax\n\
 253         option-stmt ::= q-option\n\
 254         q-option ::= option\n\
 255              | prefix `.' q-option\n\
 256              | prefix `{' option-seq `}'\n\
 257         prefix ::= word\n\
 258 \n\
 259 File source and target\n\
 260         source ::= file\n\
 261         target ::= file\n\
 262         file ::= `file' [`.'] fspec [`,' fspec]\n\
 263         fspec ::= fd-spec | name-spec | null-spec\n\
 264         fd-spec ::= [[`:']`fd'[`:']] number|`stdin'|`stdout'\n\
 265         name-spec ::= [[`:']`file'[`:']] file-name\n\
 266         file-name ::= path-seq | [ path-seq ]\n\
 267         path-seq ::= path-elt | path-seq path-elt\n\
 268         path-elt ::= `/' | word\n\
 269         null-spec ::= [`:']`null'[`:']\n\
 270 \n\
 271 Exec source and target\n\
 272         source ::= exec\n\
 273         target ::= exec\n\
 274         exec ::= `exec' [`.'] cmd-spec\n\
 275         cmd-spec ::= shell-cmd | [prog-name] `[' argv0 arg-seq `]'\n\
 276         arg-seq ::= word | arg-seq word\n\
 277         shell-cmd ::= word\n\
 278         argv0 ::= word\n\
 279 \n\
 280 Socket source and target\n\
 281         source ::= socket-source\n\
 282         target ::= socket-target\n\
 283         socket-source ::= [`socket'[`.']] [[`:']addr-type[`:']] source-addr\n\
 284         socket-target ::= [`socket'[`.']] [[`:']addr-type[`:']] target-addr\n\
 285 \n\
 286         inet-source-addr ::= [port] port\n\
 287         inet-target-addr ::= address [`:'] port\n\
 288         address ::= addr-elt | address addr-elt\n\
 289         addr-elt ::= `.' | word\n\
 290 \n\
 291         unix-source-addr ::= file-name\n\
 292         unix-target-addr ::= file-name\n\
 293 ");
 294 }
 295
 296 static void options(FILE *fp)
 297 {
 298   version(fp);
 299   pquis(fp, "\n\
 300 Options summary\n\
 301 \n\
 302 File attributes (`fattr')\n\
 303         prefix.fattr.mode [=] mode\n\
 304         prefix.fattr.owner [=] user\n\
 305         prefix.fattr.group [=] group\n\
 306 \n\
 307 File options\n\
 308         file.create [=] yes|no\n\
 309         file.open [=] no|truncate|append\n\
 310         file.fattr.*\n\
 311 \n\
 312 Exec options\n\
 313         exec.logging [=] yes|no\n\
 314         exec.dir [=] file-name\n\
 315         exec.root [=] file-name\n\
 316         exec.user [=] user\n\
 317         exec.group [=] group\n\
 318         exec.rlimit.limit[.hard|.soft] [=] value\n\
 319         exec.env.clear\n\
 320         exec.env.unset var\n\
 321         exec.env.[set] var [=] value\n\
 322 \n\
 323 Socket options\n\
 324         socket.conn [=] number|unlimited|one-shot\n\
 325         socket.logging [=] yes|no\n\
 326         socket.inet.[allow|deny] [from] address [/ address]\n\
 327         socket.unix.fattr.*\n\
 328 ");
 329 }
 330
 331 /* --- @main@ --- *
 332  *
 333  * Arguments:   @int argc@ = number of command line arguments
 334  *              @char *argv[]@ = vector of argument strings
 335  *
 336  * Returns:     ---
 337  *
 338  * Use:         Simple port-forwarding server.
 339  */
 340
 341 int main(int argc, char *argv[])
 342 {
 343   unsigned f = 0;
 344   sel_state sst;
 345   sig s_term, s_int;
 346   scanner sc;
 347
 348   enum {
 349     f_bogus = 1,
 350     f_file = 2,
 351     f_syslog = 4,
 352     f_fork = 8
 353   };
 354
 355   /* --- Initialize things --- */
 356
 357   ego(argv[0]);
 358   sel = &sst;
 359   sel_init(sel);
 360   sub_init();
 361   sig_init(sel);
 362   bres_init(sel);
 363   bres_exec(0);
 364   exec_init();
 365   fattr_init(&fattr_global);
 366   scan_create(&sc);
 367
 368   /* --- Set up some signal handlers --- *
 369    *
 370    * Don't enable @SIGINT@ if the caller already disabled it.
 371    */
 372
 373   {
 374     struct sigaction sa;
 375
 376     sig_add(&s_term, SIGTERM, fw_tidy, 0);
 377     sigaction(SIGINT, 0, &sa);
 378     if (sa.sa_handler != SIG_IGN)
 379       sig_add(&s_int, SIGINT, fw_tidy, 0);
 380   }
 381
 382   atexit(fw_exit);
 383
 384   /* --- Parse command line options --- */
 385
 386   for (;;) {
 387     static struct option opts[] = {
 388
 389       /* --- Standard GNU help options --- */
 390
 391       { "help",         0,              0,      'h' },
 392       { "version",      0,              0,      'v' },
 393       { "usage",        0,              0,      'u' },
 394
 395       /* --- Other help options --- */
 396
 397       { "grammar",      0,              0,      'g' },
 398       { "options",      0,              0,      'o' },
 399
 400       /* --- Other useful arguments --- */
 401
 402       { "file",         OPTF_ARGREQ,    0,      'f' },
 403       { "fork",         0,              0,      'd' },
 404       { "daemon",       0,              0,      'd' },
 405       { "syslog",       0,              0,      'l' },
 406       { "log",          0,              0,      'l' },
 407       { "quiet",        0,              0,      'q' },
 408
 409       /* --- Magic terminator --- */
 410
 411       { 0,              0,              0,      0 }
 412     };
 413     int i = mdwopt(argc, argv, "+hvu go f:dl", opts, 0, 0, 0);
 414
 415     if (i < 0)
 416       break;
 417     switch (i) {
 418       case 'h':
 419         help(stdout);
 420         exit(0);
 421         break;
 422       case 'v':
 423         version(stdout);
 424         exit(0);
 425         break;
 426       case 'u':
 427         usage(stdout);
 428         exit(0);
 429         break;
 430       case 'g':
 431         grammar(stdout);
 432         exit(0);
 433         break;
 434       case 'o':
 435         options(stdout);
 436         exit(0);
 437         break;
 438       case 'f':
 439         if (strcmp(optarg, "-") == 0)
 440           scan_add(&sc, scan_file(stdin, "<stdin>", SCF_NOCLOSE));
 441         else {
 442           FILE *fp;
 443           if ((fp = fopen(optarg, "r")) == 0)
 444             die(1, "couldn't open file `%s': %s", optarg, strerror(errno));
 445           scan_add(&sc, scan_file(fp, optarg, 0));
 446         }
 447         f |= f_file;
 448         break;
 449       case 'd':
 450         f |= f_fork;
 451         break;
 452       case 'l':
 453         f |= f_syslog;
 454         break;
 455       case 'q':
 456         flags |= FW_QUIET;
 457         break;
 458       default:
 459         f |= f_bogus;
 460         break;
 461     }
 462   }
 463
 464   if (f & f_bogus) {
 465     usage(stderr);
 466     exit(1);
 467   }
 468
 469   /* --- Deal with the remaining arguments --- */
 470
 471   if (optind < argc)
 472     scan_add(&sc, scan_argv(argv + optind));
 473   else if (f & f_file)
 474     /* Cool */;
 475   else if (!isatty(STDIN_FILENO))
 476     scan_add(&sc, scan_file(stdin, "<stdin>", SCF_NOCLOSE));
 477   else {
 478     moan("no configuration given and stdin is a terminal.");
 479     moan("type `%s --help' for usage information.", QUIS);
 480     exit(1);
 481   }
 482
 483   /* --- Parse the configuration now gathered --- */
 484
 485   conf_parse(&sc);
 486
 487   /* --- Fork into the background --- */
 488
 489   if (f & f_fork) {
 490     pid_t kid;
 491
 492     kid = fork();
 493     if (kid == -1)
 494       die(1, "couldn't fork: %s", strerror(errno));
 495     if (kid != 0)
 496       _exit(0);
 497
 498     close(0); close(1); close(2);
 499     chdir("/");
 500     setsid();
 501
 502     kid = fork();
 503     if (kid != 0)
 504       _exit(0);
 505   }
 506
 507   if (f & f_syslog) {
 508     flags |= FW_SYSLOG;
 509     openlog(QUIS, 0, LOG_DAEMON);
 510   }
 511
 512   /* --- Let rip --- */
 513
 514   if (!(flags & FW_SET))
 515     moan("nothing to do!");
 516   signal(SIGPIPE, SIG_IGN);
 517   while (active)
 518     sel_select(sel);
 519   return (0);
 520 }
 521
 522 /*----- That's all, folks -------------------------------------------------*/