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

   1 /* -*-c-*-
   2  *
   3  * $Id: fw.c,v 1.14 2003/01/24 20:12:40 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 1.14  2003/01/24 20:12:40  mdw
  33  * Correctly cast uid and gid sentinel values.
  34  *
  35  * Revision 1.13  2002/02/22 23:45:20  mdw
  36  * Add option to change the listen(2) parameter.  Receive `fw'-specific
  37  * code from `conf.c'.
  38  *
  39  * Revision 1.12  2002/01/13 14:49:17  mdw
  40  * Track @dstr_vputf@ change.
  41  *
  42  * Revision 1.11  2001/02/03 20:33:26  mdw
  43  * Fix flags to be unsigned.
  44  *
  45  * Revision 1.10  2001/02/03 20:30:03  mdw
  46  * Support re-reading config files on SIGHUP.
  47  *
  48  * Revision 1.9  2001/01/20 11:55:17  mdw
  49  * Handle select errors more robustly.
  50  *
  51  * Revision 1.8  2000/03/23 23:19:19  mdw
  52  * Fix changed options in parser table.
  53  *
  54  * Revision 1.7  2000/03/23 00:37:33  mdw
  55  * Add option to change user and group after initialization.  Naughtily
  56  * reassign short equivalents of --grammar and --options.
  57  *
  58  * Revision 1.6  1999/12/22 15:44:10  mdw
  59  * Make syslog a separate option, and do it better.
  60  *
  61  * Revision 1.5  1999/10/22 22:47:50  mdw
  62  * Grammar changes.  Also, don't enable SIGINT if it's currently ignored.
  63  *
  64  * Revision 1.4  1999/10/10 16:46:12  mdw
  65  * New resolver to initialize.  Also, include options for grammar and
  66  * options references.
  67  *
  68  * Revision 1.3  1999/07/26 23:30:42  mdw
  69  * Major reconstruction work for new design.
  70  *
  71  * Revision 1.2  1999/07/03 13:55:17  mdw
  72  * Various changes.  Add configuration grammar to help text.  Change to
  73  * root directory and open syslog when forking into background.
  74  *
  75  * Revision 1.1.1.1  1999/07/01 08:56:23  mdw
  76  * Initial revision.
  77  *
  78  */
  79
  80 /*----- Header files ------------------------------------------------------*/
  81
  82 #include "config.h"
  83
  84 #include <assert.h>
  85 #include <ctype.h>
  86 #include <errno.h>
  87 #include <signal.h>
  88 #include <stdarg.h>
  89 #include <stdio.h>
  90 #include <stdlib.h>
  91 #include <string.h>
  92 #include <time.h>
  93
  94 #include <unistd.h>
  95 #include <syslog.h>
  96
  97 #include <grp.h>
  98 #include <pwd.h>
  99
 100 #include <mLib/bres.h>
 101 #include <mLib/dstr.h>
 102 #include <mLib/mdwopt.h>
 103 #include <mLib/quis.h>
 104 #include <mLib/report.h>
 105 #include <mLib/sel.h>
 106 #include <mLib/sig.h>
 107 #include <mLib/sub.h>
 108
 109 #include "conf.h"
 110 #include "endpt.h"
 111 #include "exec.h"
 112 #include "fattr.h"
 113 #include "file.h"
 114 #include "fw.h"
 115 #include "scan.h"
 116 #include "socket.h"
 117 #include "source.h"
 118
 119 /*----- Global variables --------------------------------------------------*/
 120
 121 sel_state *sel;                         /* Multiplexor for nonblocking I/O */
 122
 123 /*----- Static variables --------------------------------------------------*/
 124
 125 typedef struct conffile {
 126   struct conffile *next;
 127   char *name;
 128 } conffile;
 129
 130 static unsigned flags = 0;              /* Global state flags */
 131 static unsigned active = 0;             /* Number of active things */
 132 static conffile *conffiles = 0;         /* List of configuration files */
 133
 134 #define FW_SYSLOG 1u
 135 #define FW_QUIET 2u
 136 #define FW_SET 4u
 137
 138 /*----- Configuration parsing ---------------------------------------------*/
 139
 140 /* --- @parse@ --- *
 141  *
 142  * Arguments:   @scanner *sc@ = pointer to scanner definition
 143  *
 144  * Returns:     ---
 145  *
 146  * Use:         Parses a configuration file from the scanner.
 147  */
 148
 149 static source_ops *sources[] =
 150   { &xsource_ops, &fsource_ops, &ssource_ops, 0 };
 151 static target_ops *targets[] =
 152   { &xtarget_ops, &ftarget_ops, &starget_ops, 0 };
 153
 154 void parse(scanner *sc)
 155 {
 156   token(sc);
 157
 158   for (;;) {
 159     if (sc->t == CTOK_EOF)
 160       break;
 161     if (sc->t != CTOK_WORD)
 162       error(sc, "parse error, keyword expected");
 163
 164     /* --- Handle a forwarding request --- */
 165
 166     if (strcmp(sc->d.buf, "forward") == 0 ||
 167         strcmp(sc->d.buf, "fw") == 0 ||
 168         strcmp(sc->d.buf, "from") == 0) {
 169       source *s;
 170       target *t;
 171
 172       token(sc);
 173
 174       /* --- Read a source description --- */
 175
 176       {
 177         source_ops **sops;
 178
 179         /* --- Try to find a source type which understands --- */
 180
 181         s = 0;
 182         for (sops = sources; *sops; sops++) {
 183           if ((s = (*sops)->read(sc)) != 0)
 184             goto found_source;
 185         }
 186         error(sc, "unknown source name `%s'", sc->d.buf);
 187
 188         /* --- Read any source-specific options --- */
 189
 190       found_source:
 191         if (sc->t == '{') {
 192           token(sc);
 193           while (sc->t == CTOK_WORD) {
 194             if (!s->ops->option || !s->ops->option(s, sc)) {
 195               error(sc, "unknown %s source option `%s'",
 196                     s->ops->name, sc->d.buf);
 197             }
 198             if (sc->t == ';')
 199               token(sc);
 200           }
 201           if (sc->t != '}')
 202             error(sc, "parse error, missing `}'");
 203           token(sc);
 204         }
 205       }
 206
 207       /* --- Read a destination description --- */
 208
 209       if (sc->t == CTOK_WORD && (strcmp(sc->d.buf, "to") == 0 ||
 210                                  strcmp(sc->d.buf, "->") == 0))
 211         token(sc);
 212
 213       {
 214         target_ops **tops;
 215
 216         /* --- Try to find a target which understands --- */
 217
 218         t = 0;
 219         for (tops = targets; *tops; tops++) {
 220           if ((t = (*tops)->read(sc)) != 0)
 221             goto found_target;
 222         }
 223         error(sc, "unknown target name `%s'", sc->d.buf);
 224
 225         /* --- Read any target-specific options --- */
 226
 227       found_target:
 228         if (sc->t == '{') {
 229           token(sc);
 230           while (sc->t == CTOK_WORD) {
 231             if (!t->ops->option || !t->ops->option(t, sc)) {
 232               error(sc, "unknown %s target option `%s'",
 233                     t->ops->name, sc->d.buf);
 234             }
 235             if (sc->t == ';')
 236               token(sc);
 237           }
 238           if (sc->t != '}')
 239             error(sc, "parse error, `}' expected");
 240           token(sc);
 241         }
 242       }
 243
 244       /* --- Combine the source and target --- */
 245
 246       s->ops->attach(s, sc, t);
 247     }
 248
 249     /* --- Include configuration from a file --- *
 250      *
 251      * Slightly tricky.  Scan the optional semicolon from the including
 252      * stream, not the included one.
 253      */
 254
 255     else if (strcmp(sc->d.buf, "include") == 0) {
 256       FILE *fp;
 257       dstr d = DSTR_INIT;
 258
 259       token(sc);
 260       conf_name(sc, '/', &d);
 261       if ((fp = fopen(d.buf, "r")) == 0)
 262         error(sc, "can't include `%s': %s", d.buf, strerror(errno));
 263       if (sc->t == ';')
 264         token(sc);
 265       pushback(sc);
 266       scan_push(sc, scan_file(fp, d.buf, 0));
 267       token(sc);
 268       dstr_destroy(&d);
 269       continue;                         /* Don't parse a trailing `;' */
 270     }
 271
 272     /* --- Other configuration is handled elsewhere --- */
 273
 274     else {
 275
 276       /* --- First try among the sources --- */
 277
 278       {
 279         source_ops **sops;
 280
 281         for (sops = sources; *sops; sops++) {
 282           if ((*sops)->option && (*sops)->option(0, sc))
 283             goto found_option;
 284         }
 285       }
 286
 287       /* --- Then try among the targets --- */
 288
 289       {
 290         target_ops **tops;
 291
 292         for (tops = targets; *tops; tops++) {
 293           if ((*tops)->option && (*tops)->option(0, sc))
 294             goto found_option;
 295         }
 296       }
 297
 298       /* --- Nobody wants the option --- */
 299
 300       error(sc, "unknown global option or prefix `%s'", sc->d.buf);
 301
 302     found_option:;
 303     }
 304
 305     if (sc->t == ';')
 306       token(sc);
 307   }
 308 }
 309
 310 /*----- General utility functions -----------------------------------------*/
 311
 312 /* --- @fw_log@ --- *
 313  *
 314  * Arguments:   @time_t t@ = when the connection occurred or (@-1@)
 315  *              @const char *fmt@ = format string to fill in
 316  *              @...@ = other arguments
 317  *
 318  * Returns:     ---
 319  *
 320  * Use:         Logs a connection.
 321  */
 322
 323 void fw_log(time_t t, const char *fmt, ...)
 324 {
 325   struct tm *tm;
 326   dstr d = DSTR_INIT;
 327   va_list ap;
 328
 329   if (flags & FW_QUIET)
 330     return;
 331
 332   if (t == -1)
 333     t = time(0);
 334   tm = localtime(&t);
 335   DENSURE(&d, 64);
 336   d.len += strftime(d.buf, d.sz, "%Y-%m-%d %H:%M:%S ", tm);
 337   va_start(ap, fmt);
 338   dstr_vputf(&d, fmt, &ap);
 339   va_end(ap);
 340   if (flags & FW_SYSLOG)
 341     syslog(LOG_NOTICE, "%s", d.buf);
 342   else {
 343     DPUTC(&d, '\n');
 344     dstr_write(&d, stderr);
 345   }
 346   DDESTROY(&d);
 347 }
 348
 349 /* --- @fw_inc@, @fw_dec@ --- *
 350  *
 351  * Arguments:   ---
 352  *
 353  * Returns:     ---
 354  *
 355  * Use:         Increments or decrements the active thing count.  `fw' won't
 356  *              quit while there are active things.
 357  */
 358
 359 void fw_inc(void) { flags |= FW_SET; active++; }
 360 void fw_dec(void) { if (active) active--; }
 361
 362 /* --- @fw_exit@ --- *
 363  *
 364  * Arguments:   ---
 365  *
 366  * Returns:     ---
 367  *
 368  * Use:         Exits when appropriate.
 369  */
 370
 371 static void fw_exit(void)
 372 {
 373   endpt_killall();
 374   source_killall();
 375 }
 376
 377 /* --- @fw_tidy@ --- *
 378  *
 379  * Arguments:   @int n@ = signal number
 380  *              @void *p@ = an uninteresting argument
 381  *
 382  * Returns:     ---
 383  *
 384  * Use:         Handles various signals and causes a clean tidy-up.
 385  */
 386
 387 static void fw_tidy(int n, void *p)
 388 {
 389   const char *sn = 0;
 390   switch (n) {
 391     case SIGTERM: sn = "SIGTERM"; break;
 392     case SIGINT: sn = "SIGINT"; break;
 393     default: abort();
 394   }
 395
 396   fw_log(-1, "closing down gracefully on %s", sn);
 397   source_killall();
 398 }
 399
 400 /* --- @fw_die@ --- *
 401  *
 402  * Arguments:   @int n@ = signal number
 403  *              @void *p@ = an uninteresting argument
 404  *
 405  * Returns:     ---
 406  *
 407  * Use:         Handles various signals and causes an abrupt shutdown.
 408  */
 409
 410 static void fw_die(int n, void *p)
 411 {
 412   const char *sn = 0;
 413   switch (n) {
 414     case SIGQUIT: sn = "SIGQUIT"; break;
 415     default: abort();
 416   }
 417
 418   fw_log(-1, "closing down abruptly on %s", sn);
 419   source_killall();
 420   endpt_killall();
 421 }
 422
 423 /* --- @fw_reload@ --- *
 424  *
 425  * Arguments:   @int n@ = a signal number
 426  *              @void *p@ = an uninteresting argument
 427  *
 428  * Returns:     ---
 429  *
 430  * Use:         Handles a hangup signal by re-reading configuration files.
 431  */
 432
 433 static void fw_reload(int n, void *p)
 434 {
 435   FILE *fp;
 436   scanner sc;
 437   conffile *cf;
 438
 439   assert(n == SIGHUP);
 440   if (!conffiles) {
 441     fw_log(-1, "no configuration files to reload: ignoring SIGHUP");
 442     return;
 443   }
 444   fw_log(-1, "reloading configuration files...");
 445   source_killall();
 446   scan_create(&sc);
 447   for (cf = conffiles; cf; cf = cf->next) {
 448     if ((fp = fopen(cf->name, "r")) == 0)
 449       fw_log(-1, "error loading `%s': %s", cf->name, strerror(errno));
 450     else
 451       scan_add(&sc, scan_file(fp, cf->name, 0));
 452   }
 453   parse(&sc);
 454   fw_log(-1, "... reload completed OK");
 455 }
 456
 457 /*----- Startup and options parsing ---------------------------------------*/
 458
 459 /* --- Standard GNU help options --- */
 460
 461 static void version(FILE *fp)
 462 {
 463   pquis(fp, "$ version " VERSION "\n");
 464 }
 465
 466 static void usage(FILE *fp)
 467 {
 468   pquis(fp, "Usage: $ [-dql] [-f file] [config statements...]\n");
 469 }
 470
 471 static void help(FILE *fp)
 472 {
 473   version(fp);
 474   fputc('\n', fp);
 475   usage(fp);
 476   pquis(fp, "\n\
 477 An excessively full-featured port-forwarder, which subsumes large chunks\n\
 478 of the functionality of inetd, netcat, and normal cat.  Options available\n\
 479 are:\n\
 480 \n\
 481 -h, --help        Display this help message.\n\
 482 -v, --version     Display the program's version number.\n\
 483 -u, --usage       Display a terse usage summary.\n\
 484 \n\
 485 -G, --grammar     Show a summary of the configuration language.\n\
 486 -O, --options     Show a summary of the source and target options.\n\
 487 \n\
 488 -f, --file=FILE   Read configuration from a file.\n\
 489 -q, --quiet       Don't emit any logging information.\n\
 490 -d, --daemon      Fork into background after initializing.\n\
 491 -l, --syslog      Send log output to the system logger.\n\
 492 -s, --setuid=USER Change uid to USER after initializing sources.\n\
 493 -g, --setgid=GRP  Change gid to GRP after initializing sources.\n\
 494 \n\
 495 Configuration may be supplied in one or more configuration files, or on\n\
 496 the command line (or both).  If no `-f' option is present, and no\n\
 497 configuration is given on the command line, the standard input stream is\n\
 498 read.\n\
 499 \n\
 500 Configuration is free-form.  Comments begin with a `#' character and\n\
 501 continue to the end of the line.  Each command line argument is considered\n\
 502 to be a separate line.\n\
 503 \n\
 504 The grammar is fairly complicated.  For a summary, run `$ --grammar'.\n\
 505 For a summary of the various options, run `$ --options'.\n\
 506 ");
 507 }
 508
 509 /* --- Other helpful options --- */
 510
 511 static void grammar(FILE *fp)
 512 {
 513   version(fp);
 514   pquis(fp, "\n\
 515 Grammar summary\n\
 516 \n\
 517 Basic syntax\n\
 518         file ::= empty | file stmt [`;']\n\
 519         stmt ::= option-stmt | fw-stmt\n\
 520         fw-stmt ::= `fw' source options [`to'|`->'] target options\n\
 521         options ::= `{' option-seq `}'\n\
 522         option-seq ::= empty | option-stmt [`;'] option-seq\n\
 523 \n\
 524 Option syntax\n\
 525         option-stmt ::= q-option\n\
 526         q-option ::= option\n\
 527              | prefix `.' q-option\n\
 528              | prefix `{' option-seq `}'\n\
 529         prefix ::= word\n\
 530 \n\
 531 File source and target\n\
 532         source ::= file\n\
 533         target ::= file\n\
 534         file ::= `file' [`.'] fspec [`,' fspec]\n\
 535         fspec ::= fd-spec | name-spec | null-spec\n\
 536         fd-spec ::= [[`:']`fd'[`:']] number|`stdin'|`stdout'\n\
 537         name-spec ::= [[`:']`file'[`:']] file-name\n\
 538         file-name ::= path-seq | [ path-seq ]\n\
 539         path-seq ::= path-elt | path-seq path-elt\n\
 540         path-elt ::= `/' | word\n\
 541         null-spec ::= [`:']`null'[`:']\n\
 542 \n\
 543 Exec source and target\n\
 544         source ::= exec\n\
 545         target ::= exec\n\
 546         exec ::= `exec' [`.'] cmd-spec\n\
 547         cmd-spec ::= shell-cmd | [prog-name] `[' argv0 arg-seq `]'\n\
 548         arg-seq ::= word | arg-seq word\n\
 549         shell-cmd ::= word\n\
 550         argv0 ::= word\n\
 551 \n\
 552 Socket source and target\n\
 553         source ::= socket-source\n\
 554         target ::= socket-target\n\
 555         socket-source ::= [`socket'[`.']] [[`:']addr-type[`:']] source-addr\n\
 556         socket-target ::= [`socket'[`.']] [[`:']addr-type[`:']] target-addr\n\
 557 \n\
 558         inet-source-addr ::= [port] port\n\
 559         inet-target-addr ::= address [`:'] port\n\
 560         address ::= addr-elt | address addr-elt\n\
 561         addr-elt ::= `.' | word\n\
 562 \n\
 563         unix-source-addr ::= file-name\n\
 564         unix-target-addr ::= file-name\n\
 565 ");
 566 }
 567
 568 static void options(FILE *fp)
 569 {
 570   version(fp);
 571   pquis(fp, "\n\
 572 Options summary\n\
 573 \n\
 574 File attributes (`fattr')\n\
 575         prefix.fattr.mode [=] mode\n\
 576         prefix.fattr.owner [=] user\n\
 577         prefix.fattr.group [=] group\n\
 578 \n\
 579 File options\n\
 580         file.create [=] yes|no\n\
 581         file.open [=] no|truncate|append\n\
 582         file.fattr.*\n\
 583 \n\
 584 Exec options\n\
 585         exec.logging [=] yes|no\n\
 586         exec.dir [=] file-name\n\
 587         exec.root [=] file-name\n\
 588         exec.user [=] user\n\
 589         exec.group [=] group\n\
 590         exec.rlimit.limit[.hard|.soft] [=] value\n\
 591         exec.env.clear\n\
 592         exec.env.unset var\n\
 593         exec.env.[set] var [=] value\n\
 594 \n\
 595 Socket options\n\
 596         socket.conn [=] number|unlimited|one-shot\n\
 597         socket.listen [=] number\n\
 598         socket.logging [=] yes|no\n\
 599 \n\
 600         socket.inet.[allow|deny] [from] address [/ address]\n\
 601 \n\
 602         socket.unix.fattr.*\n\
 603 ");
 604 }
 605
 606 /* --- @main@ --- *
 607  *
 608  * Arguments:   @int argc@ = number of command line arguments
 609  *              @char *argv[]@ = vector of argument strings
 610  *
 611  * Returns:     ---
 612  *
 613  * Use:         Simple port-forwarding server.
 614  */
 615
 616 int main(int argc, char *argv[])
 617 {
 618   unsigned f = 0;
 619   sel_state sst;
 620   sig s_term, s_quit, s_int, s_hup;
 621   scanner sc;
 622   uid_t drop = -1;
 623   gid_t dropg = -1;
 624   conffile *cf, **cff = &conffiles;
 625
 626 #define f_bogus 1u
 627 #define f_file 2u
 628 #define f_syslog 4u
 629 #define f_fork 8u
 630
 631   /* --- Initialize things --- */
 632
 633   ego(argv[0]);
 634   sel = &sst;
 635   sel_init(sel);
 636   sub_init();
 637   sig_init(sel);
 638   bres_init(sel);
 639   bres_exec(0);
 640   exec_init();
 641   fattr_init(&fattr_global);
 642   scan_create(&sc);
 643
 644   atexit(fw_exit);
 645
 646   /* --- Parse command line options --- */
 647
 648   for (;;) {
 649     static struct option opts[] = {
 650
 651       /* --- Standard GNU help options --- */
 652
 653       { "help",         0,              0,      'h' },
 654       { "version",      0,              0,      'v' },
 655       { "usage",        0,              0,      'u' },
 656
 657       /* --- Other help options --- */
 658
 659       { "grammar",      0,              0,      'G' },
 660       { "options",      0,              0,      'O' },
 661
 662       /* --- Other useful arguments --- */
 663
 664       { "file",         OPTF_ARGREQ,    0,      'f' },
 665       { "fork",         0,              0,      'd' },
 666       { "daemon",       0,              0,      'd' },
 667       { "syslog",       0,              0,      'l' },
 668       { "log",          0,              0,      'l' },
 669       { "quiet",        0,              0,      'q' },
 670       { "setuid",       OPTF_ARGREQ,    0,      's' },
 671       { "uid",          OPTF_ARGREQ,    0,      's' },
 672       { "setgid",       OPTF_ARGREQ,    0,      'g' },
 673       { "gid",          OPTF_ARGREQ,    0,      'g' },
 674
 675       /* --- Magic terminator --- */
 676
 677       { 0,              0,              0,      0 }
 678     };
 679     int i = mdwopt(argc, argv, "+hvu GO f:dls:g:", opts, 0, 0, 0);
 680
 681     if (i < 0)
 682       break;
 683     switch (i) {
 684       case 'h':
 685         help(stdout);
 686         exit(0);
 687         break;
 688       case 'v':
 689         version(stdout);
 690         exit(0);
 691         break;
 692       case 'u':
 693         usage(stdout);
 694         exit(0);
 695         break;
 696       case 'G':
 697         grammar(stdout);
 698         exit(0);
 699         break;
 700       case 'O':
 701         options(stdout);
 702         exit(0);
 703         break;
 704       case 'f':
 705         if (strcmp(optarg, "-") == 0)
 706           scan_add(&sc, scan_file(stdin, "<stdin>", SCF_NOCLOSE));
 707         else {
 708           FILE *fp;
 709           if ((fp = fopen(optarg, "r")) == 0)
 710             die(1, "couldn't open file `%s': %s", optarg, strerror(errno));
 711           cf = CREATE(conffile);
 712           cf->name = optarg;
 713           *cff = cf;
 714           cff = &cf->next;
 715           scan_add(&sc, scan_file(fp, optarg, 0));
 716         }
 717         f |= f_file;
 718         break;
 719       case 'd':
 720         f |= f_fork;
 721         break;
 722       case 'l':
 723         f |= f_syslog;
 724         break;
 725       case 'q':
 726         flags |= FW_QUIET;
 727         break;
 728       case 's':
 729         if (isdigit((unsigned char )optarg[0])) {
 730           char *q;
 731           drop = strtol(optarg, &q, 0);
 732           if (*q)
 733             die(1, "bad uid `%s'", optarg);
 734         } else {
 735           struct passwd *pw = getpwnam(optarg);
 736           if (!pw)
 737             die(1, "unknown user `%s'", optarg);
 738           drop = pw->pw_uid;
 739         }
 740         break;
 741       case 'g':
 742         if (isdigit((unsigned char )optarg[0])) {
 743           char *q;
 744           dropg = strtol(optarg, &q, 0);
 745           if (*q)
 746             die(1, "bad gid `%s'", optarg);
 747         } else {
 748           struct group *gr = getgrnam(optarg);
 749           if (!gr)
 750             die(1, "unknown group `%s'", optarg);
 751           dropg = gr->gr_gid;
 752         }
 753         break;
 754       default:
 755         f |= f_bogus;
 756         break;
 757     }
 758   }
 759
 760   if (f & f_bogus) {
 761     usage(stderr);
 762     exit(1);
 763   }
 764   *cff = 0;
 765
 766   /* --- Deal with the remaining arguments --- */
 767
 768   if (optind < argc)
 769     scan_add(&sc, scan_argv(argv + optind));
 770   else if (f & f_file)
 771     /* Cool */;
 772   else if (!isatty(STDIN_FILENO))
 773     scan_add(&sc, scan_file(stdin, "<stdin>", SCF_NOCLOSE));
 774   else {
 775     moan("no configuration given and stdin is a terminal.");
 776     moan("type `%s --help' for usage information.", QUIS);
 777     exit(1);
 778   }
 779
 780   /* --- Parse the configuration now gathered --- */
 781
 782   parse(&sc);
 783
 784   /* --- Set up some signal handlers --- *
 785    *
 786    * Don't enable @SIGINT@ if the caller already disabled it.
 787    */
 788
 789   {
 790     struct sigaction sa;
 791
 792     sig_add(&s_term, SIGTERM, fw_tidy, 0);
 793     sig_add(&s_quit, SIGQUIT, fw_die, 0);
 794     sigaction(SIGINT, 0, &sa);
 795     if (sa.sa_handler != SIG_IGN)
 796       sig_add(&s_int, SIGINT, fw_tidy, 0);
 797     sig_add(&s_hup, SIGHUP, fw_reload, 0);
 798   }
 799
 800   /* --- Drop privileges --- */
 801
 802 #ifdef HAVE_SETGROUPS
 803   if ((dropg != (gid_t)-1 && (setgid(dropg) || setgroups(1, &dropg))) ||
 804       (drop != (uid_t)-1 && setuid(drop)))
 805     die(1, "couldn't drop privileges: %s", strerror(errno));
 806 #else
 807   if ((dropg != (gid_t)-1 && setgid(dropg)) ||
 808       (drop != (uid_t)-1 && setuid(drop)))
 809     die(1, "couldn't drop privileges: %s", strerror(errno));
 810 #endif
 811
 812   /* --- Fork into the background --- */
 813
 814   if (f & f_fork) {
 815     pid_t kid;
 816
 817     kid = fork();
 818     if (kid == -1)
 819       die(1, "couldn't fork: %s", strerror(errno));
 820     if (kid != 0)
 821       _exit(0);
 822
 823     close(0); close(1); close(2);
 824     chdir("/");
 825     setsid();
 826
 827     kid = fork();
 828     if (kid != 0)
 829       _exit(0);
 830   }
 831
 832   if (f & f_syslog) {
 833     flags |= FW_SYSLOG;
 834     openlog(QUIS, 0, LOG_DAEMON);
 835   }
 836
 837   /* --- Let rip --- */
 838
 839   if (!(flags & FW_SET))
 840     moan("nothing to do!");
 841   signal(SIGPIPE, SIG_IGN);
 842
 843   {
 844     int selerr = 0;
 845     while (active) {
 846       if (!sel_select(sel))
 847         selerr = 0;
 848       else if (errno != EINTR && errno != EAGAIN) {
 849         fw_log(-1, "error from select: %s", strerror(errno));
 850         selerr++;
 851         if (selerr > 8) {
 852           fw_log(-1, "too many consecutive select errors: bailing out");
 853           exit(EXIT_FAILURE);
 854         }
 855       }
 856     }
 857   }
 858
 859   return (0);
 860 }
 861
 862 /*----- That's all, folks -------------------------------------------------*/