X-Git-Url: https://git.distorted.org.uk/~mdw/fwd/blobdiff_plain/a542396b43f4217f5b76bf884ca1b9080dbd5cfa..9155ea97b695b6eb5fca1ee79f57b334f6c4ef53:/fwd.c diff --git a/fwd.c b/fwd.c new file mode 100644 index 0000000..d80275b --- /dev/null +++ b/fwd.c @@ -0,0 +1,717 @@ +/* -*-c-*- + * + * Port forwarding thingy + * + * (c) 1999 Straylight/Edgeware + */ + +/*----- Licensing notice --------------------------------------------------* + * + * This file is part of the `fwd' port forwarder. + * + * `fwd' is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * `fwd' is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with `fwd'; if not, write to the Free Software Foundation, + * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + */ + +#include "fwd.h" + +/*----- Global variables --------------------------------------------------*/ + +sel_state *sel; /* Multiplexor for nonblocking I/O */ + +/*----- Static variables --------------------------------------------------*/ + +typedef struct conffile { + struct conffile *next; + char *name; +} conffile; + +static unsigned flags = 0; /* Global state flags */ +static unsigned active = 0; /* Number of active things */ +static conffile *conffiles = 0; /* List of configuration files */ + +#define FW_SYSLOG 1u +#define FW_QUIET 2u +#define FW_SET 4u + +/*----- Configuration parsing ---------------------------------------------*/ + +/* --- @parse@ --- * + * + * Arguments: @scanner *sc@ = pointer to scanner definition + * + * Returns: --- + * + * Use: Parses a configuration file from the scanner. + */ + +static source_ops *sources[] = + { &xsource_ops, &fsource_ops, &ssource_ops, 0 }; +static target_ops *targets[] = + { &xtarget_ops, &ftarget_ops, &starget_ops, 0 }; + +void parse(scanner *sc) +{ + token(sc); + + for (;;) { + if (sc->t == CTOK_EOF) + break; + if (sc->t != CTOK_WORD) + error(sc, "parse error, keyword expected"); + + /* --- Handle a forwarding request --- */ + + if (strcmp(sc->d.buf, "forward") == 0 || + strcmp(sc->d.buf, "fwd") == 0 || + strcmp(sc->d.buf, "from") == 0) { + source *s; + target *t; + + token(sc); + + /* --- Read a source description --- */ + + { + source_ops **sops; + + /* --- Try to find a source type which understands --- */ + + s = 0; + for (sops = sources; *sops; sops++) { + if ((s = (*sops)->read(sc)) != 0) + goto found_source; + } + error(sc, "unknown source name `%s'", sc->d.buf); + + /* --- Read any source-specific options --- */ + + found_source: + if (sc->t == '{') { + token(sc); + while (sc->t == CTOK_WORD) { + if (!s->ops->option || !s->ops->option(s, sc)) { + error(sc, "unknown %s source option `%s'", + s->ops->name, sc->d.buf); + } + if (sc->t == ';') + token(sc); + } + if (sc->t != '}') + error(sc, "parse error, missing `}'"); + token(sc); + } + } + + /* --- Read a destination description --- */ + + if (sc->t == CTOK_WORD && (strcmp(sc->d.buf, "to") == 0 || + strcmp(sc->d.buf, "->") == 0)) + token(sc); + + { + target_ops **tops; + + /* --- Try to find a target which understands --- */ + + t = 0; + for (tops = targets; *tops; tops++) { + if ((t = (*tops)->read(sc)) != 0) + goto found_target; + } + error(sc, "unknown target name `%s'", sc->d.buf); + + /* --- Read any target-specific options --- */ + + found_target: + if (sc->t == '{') { + token(sc); + while (sc->t == CTOK_WORD) { + if (!t->ops->option || !t->ops->option(t, sc)) { + error(sc, "unknown %s target option `%s'", + t->ops->name, sc->d.buf); + } + if (sc->t == ';') + token(sc); + } + if (sc->t != '}') + error(sc, "parse error, `}' expected"); + token(sc); + } + } + + /* --- Combine the source and target --- */ + + s->ops->attach(s, sc, t); + if (t->ops->confirm) + t->ops->confirm(t); + } + + /* --- Include configuration from a file --- * + * + * Slightly tricky. Scan the optional semicolon from the including + * stream, not the included one. + */ + + else if (strcmp(sc->d.buf, "include") == 0) { + FILE *fp; + dstr d = DSTR_INIT; + + token(sc); + conf_name(sc, '/', &d); + if ((fp = fopen(d.buf, "r")) == 0) + error(sc, "can't include `%s': %s", d.buf, strerror(errno)); + if (sc->t == ';') + token(sc); + pushback(sc); + scan_push(sc, scan_file(fp, d.buf, 0)); + token(sc); + dstr_destroy(&d); + continue; /* Don't parse a trailing `;' */ + } + + /* --- Other configuration is handled elsewhere --- */ + + else { + + /* --- First try among the sources --- */ + + { + source_ops **sops; + + for (sops = sources; *sops; sops++) { + if ((*sops)->option && (*sops)->option(0, sc)) + goto found_option; + } + } + + /* --- Then try among the targets --- */ + + { + target_ops **tops; + + for (tops = targets; *tops; tops++) { + if ((*tops)->option && (*tops)->option(0, sc)) + goto found_option; + } + } + + /* --- Nobody wants the option --- */ + + error(sc, "unknown global option or prefix `%s'", sc->d.buf); + + found_option:; + } + + if (sc->t == ';') + token(sc); + } +} + +/*----- General utility functions -----------------------------------------*/ + +/* --- @fw_log@ --- * + * + * Arguments: @time_t t@ = when the connection occurred or (@-1@) + * @const char *fmt@ = format string to fill in + * @...@ = other arguments + * + * Returns: --- + * + * Use: Logs a connection. + */ + +void fw_log(time_t t, const char *fmt, ...) +{ + struct tm *tm; + dstr d = DSTR_INIT; + va_list ap; + + if (flags & FW_QUIET) + return; + + if (t == -1) + t = time(0); + tm = localtime(&t); + DENSURE(&d, 64); + d.len += strftime(d.buf, d.sz, "%Y-%m-%d %H:%M:%S ", tm); + va_start(ap, fmt); + dstr_vputf(&d, fmt, &ap); + va_end(ap); + if (flags & FW_SYSLOG) + syslog(LOG_NOTICE, "%s", d.buf); + else { + DPUTC(&d, '\n'); + dstr_write(&d, stderr); + } + DDESTROY(&d); +} + +/* --- @fw_inc@, @fw_dec@ --- * + * + * Arguments: --- + * + * Returns: --- + * + * Use: Increments or decrements the active thing count. `fwd' won't + * quit while there are active things. + */ + +void fw_inc(void) { flags |= FW_SET; active++; } +void fw_dec(void) { if (active) active--; } + +/* --- @fw_exit@ --- * + * + * Arguments: --- + * + * Returns: --- + * + * Use: Exits when appropriate. + */ + +static void fw_exit(void) +{ + endpt_killall(); + source_killall(); +} + +/* --- @fw_tidy@ --- * + * + * Arguments: @int n@ = signal number + * @void *p@ = an uninteresting argument + * + * Returns: --- + * + * Use: Handles various signals and causes a clean tidy-up. + */ + +static void fw_tidy(int n, void *p) +{ + const char *sn = 0; + switch (n) { + case SIGTERM: sn = "SIGTERM"; break; + case SIGINT: sn = "SIGINT"; break; + default: abort(); + } + + fw_log(-1, "closing down gracefully on %s", sn); + source_killall(); +} + +/* --- @fw_die@ --- * + * + * Arguments: @int n@ = signal number + * @void *p@ = an uninteresting argument + * + * Returns: --- + * + * Use: Handles various signals and causes an abrupt shutdown. + */ + +static void fw_die(int n, void *p) +{ + const char *sn = 0; + switch (n) { + case SIGQUIT: sn = "SIGQUIT"; break; + default: abort(); + } + + fw_log(-1, "closing down abruptly on %s", sn); + source_killall(); + endpt_killall(); +} + +/* --- @fw_reload@ --- * + * + * Arguments: @int n@ = a signal number + * @void *p@ = an uninteresting argument + * + * Returns: --- + * + * Use: Handles a hangup signal by re-reading configuration files. + */ + +static void fw_reload(int n, void *p) +{ + FILE *fp; + scanner sc; + conffile *cf; + + assert(n == SIGHUP); + if (!conffiles) { + fw_log(-1, "no configuration files to reload: ignoring SIGHUP"); + return; + } + fw_log(-1, "reloading configuration files..."); + source_killall(); + scan_create(&sc); + for (cf = conffiles; cf; cf = cf->next) { + if ((fp = fopen(cf->name, "r")) == 0) + fw_log(-1, "error loading `%s': %s", cf->name, strerror(errno)); + else + scan_add(&sc, scan_file(fp, cf->name, 0)); + } + parse(&sc); + fw_log(-1, "... reload completed OK"); +} + +/*----- Startup and options parsing ---------------------------------------*/ + +/* --- Standard GNU help options --- */ + +static void version(FILE *fp) +{ + pquis(fp, "$ version " VERSION "\n"); +} + +static void usage(FILE *fp) +{ + pquis(fp, "Usage: $ [-dql] [-p PIDFILE] [-f FILE] [CONFIG-STMTS...]\n"); +} + +static void help(FILE *fp) +{ + version(fp); + fputc('\n', fp); + usage(fp); + pquis(fp, "\n\ +An excessively full-featured port-forwarder, which subsumes large chunks\n\ +of the functionality of inetd, netcat, and normal cat.\n\ +\n\ +Configuration may be supplied in one or more configuration files, or on\n\ +the command line (or both). If no `-f' option is present, and no\n\ +configuration is given on the command line, the standard input stream is\n\ +read.\n\ +\n\ +Configuration is free-form. Comments begin with a `#' character and\n\ +continue to the end of the line. Each command line argument is considered\n\ +to be a separate line.\n\ +\n\ +The grammar is fairly complicated. For a summary, run `$ --grammar'.\n\ +For a summary of the various options, run `$ --options'.\n\ +\n\ +Options available are:\n\ +\n\ +Help options:\n\ + -h, --help Display this help message.\n\ + -v, --version Display the program's version number.\n\ + -u, --usage Display a terse usage summary.\n\ +\n\ +Configuration summary:\n\ + -G, --grammar Show a summary of the configuration language.\n\ + -O, --options Show a summary of the source and target options.\n\ +\n\ +Other options:\n\ + -f, --file=FILE Read configuration from a file.\n\ + -q, --quiet Don't emit any logging information.\n\ + -d, --daemon Fork into background after initializing.\n\ + -p, --pidfile=FILE Write process-id to the named FILE.\n\ + -l, --syslog Send log output to the system logger.\n\ + -s, --setuid=USER Change uid to USER after initializing sources.\n\ + -g, --setgid=GRP Change gid to GRP after initializing sources.\n\ +"); +} + +/* --- Other helpful options --- */ + +static void grammar(FILE *fp) +{ + version(fp); + fputs("\nGrammar summary\n\n", fp); + fputs(grammar_text, fp); +} + +static void options(FILE *fp) +{ + version(fp); + fputs("\nOption summary\n\n", fp); + fputs(option_text, fp); +} + +/* --- @main@ --- * + * + * Arguments: @int argc@ = number of command line arguments + * @char *argv[]@ = vector of argument strings + * + * Returns: --- + * + * Use: Simple port-forwarding server. + */ + +int main(int argc, char *argv[]) +{ + unsigned f = 0; + sel_state sst; + sig s_term, s_quit, s_int, s_hup; + scanner sc; + uid_t drop = -1; + gid_t dropg = -1; + const char *pidfile = 0; + conffile *cf, **cff = &conffiles; + +#define f_bogus 1u +#define f_file 2u +#define f_syslog 4u +#define f_fork 8u + + /* --- Initialize things --- */ + + ego(argv[0]); + sel = &sst; + sel_init(sel); + sub_init(); + sig_init(sel); + bres_init(sel); + bres_exec(0); + exec_init(); + fattr_init(&fattr_global); + scan_create(&sc); + + atexit(fw_exit); + + /* --- Parse command line options --- */ + + for (;;) { + static struct option opts[] = { + + /* --- Standard GNU help options --- */ + + { "help", 0, 0, 'h' }, + { "version", 0, 0, 'v' }, + { "usage", 0, 0, 'u' }, + + /* --- Other help options --- */ + + { "grammar", 0, 0, 'G' }, + { "options", 0, 0, 'O' }, + + /* --- Other useful arguments --- */ + + { "file", OPTF_ARGREQ, 0, 'f' }, + { "fork", 0, 0, 'd' }, + { "daemon", 0, 0, 'd' }, + { "pidfile", OPTF_ARGREQ, 0, 'p' }, + { "syslog", 0, 0, 'l' }, + { "log", 0, 0, 'l' }, + { "quiet", 0, 0, 'q' }, + { "setuid", OPTF_ARGREQ, 0, 's' }, + { "uid", OPTF_ARGREQ, 0, 's' }, + { "setgid", OPTF_ARGREQ, 0, 'g' }, + { "gid", OPTF_ARGREQ, 0, 'g' }, + + /* --- Magic terminator --- */ + + { 0, 0, 0, 0 } + }; + int i = mdwopt(argc, argv, "+hvu" "GO" "f:dp:ls:g:", opts, 0, 0, 0); + + if (i < 0) + break; + switch (i) { + case 'h': + help(stdout); + exit(0); + break; + case 'v': + version(stdout); + exit(0); + break; + case 'u': + usage(stdout); + exit(0); + break; + case 'G': + grammar(stdout); + exit(0); + break; + case 'O': + options(stdout); + exit(0); + break; + case 'f': + if (strcmp(optarg, "-") == 0) + scan_add(&sc, scan_file(stdin, "", SCF_NOCLOSE)); + else { + FILE *fp; + if ((fp = fopen(optarg, "r")) == 0) + die(1, "couldn't open file `%s': %s", optarg, strerror(errno)); + cf = CREATE(conffile); + cf->name = optarg; + *cff = cf; + cff = &cf->next; + scan_add(&sc, scan_file(fp, optarg, 0)); + } + f |= f_file; + break; + case 'd': + f |= f_fork; + break; + case 'p': + pidfile = optarg; + break; + case 'l': + f |= f_syslog; + break; + case 'q': + flags |= FW_QUIET; + break; + case 's': + if (isdigit((unsigned char )optarg[0])) { + char *q; + drop = strtol(optarg, &q, 0); + if (*q) + die(1, "bad uid `%s'", optarg); + } else { + struct passwd *pw = getpwnam(optarg); + if (!pw) + die(1, "unknown user `%s'", optarg); + drop = pw->pw_uid; + } + break; + case 'g': + if (isdigit((unsigned char )optarg[0])) { + char *q; + dropg = strtol(optarg, &q, 0); + if (*q) + die(1, "bad gid `%s'", optarg); + } else { + struct group *gr = getgrnam(optarg); + if (!gr) + die(1, "unknown group `%s'", optarg); + dropg = gr->gr_gid; + } + break; + default: + f |= f_bogus; + break; + } + } + + if (f & f_bogus) { + usage(stderr); + exit(1); + } + *cff = 0; + + /* --- Deal with the remaining arguments --- */ + + if (optind < argc) + scan_add(&sc, scan_argv(argv + optind)); + else if (f & f_file) + /* Cool */; + else if (!isatty(STDIN_FILENO)) + scan_add(&sc, scan_file(stdin, "", SCF_NOCLOSE)); + else { + moan("no configuration given and stdin is a terminal."); + moan("type `%s --help' for usage information.", QUIS); + exit(1); + } + + /* --- Parse the configuration now gathered --- */ + + parse(&sc); + + /* --- Set up some signal handlers --- * + * + * Don't enable @SIGINT@ if the caller already disabled it. + */ + + { + struct sigaction sa; + + sig_add(&s_term, SIGTERM, fw_tidy, 0); + sig_add(&s_quit, SIGQUIT, fw_die, 0); + sigaction(SIGINT, 0, &sa); + if (sa.sa_handler != SIG_IGN) + sig_add(&s_int, SIGINT, fw_tidy, 0); + sig_add(&s_hup, SIGHUP, fw_reload, 0); + } + + /* --- Fork into the background --- */ + + if (f & f_fork) { + pid_t kid; + + kid = fork(); + if (kid == -1) + die(1, "couldn't fork: %s", strerror(errno)); + if (kid != 0) + _exit(0); + + close(0); close(1); close(2); + chdir("/"); + setsid(); + + kid = fork(); + if (kid != 0) + _exit(0); + } + if (pidfile) { + FILE *fp = fopen(pidfile, "w"); + if (!fp) { + die(EXIT_FAILURE, "couldn't create pidfile `%s': %s", + pidfile, strerror(errno)); + } + fprintf(fp, "%lu\n", (unsigned long)getpid()); + if (fflush(fp) || ferror(fp) || fclose(fp)) { + die(EXIT_FAILURE, "couldn't write pidfile `%s': %s", + pidfile, strerror(errno)); + } + } + + if (f & f_syslog) { + flags |= FW_SYSLOG; + openlog(QUIS, 0, LOG_DAEMON); + } + + /* --- Drop privileges --- */ + + if (drop != (uid_t)-1) + privconn_split(sel); +#ifdef HAVE_SETGROUPS + if ((dropg != (gid_t)-1 && (setgid(dropg) || setgroups(1, &dropg))) || + (drop != (uid_t)-1 && setuid(drop))) + die(1, "couldn't drop privileges: %s", strerror(errno)); +#else + if ((dropg != (gid_t)-1 && setgid(dropg)) || + (drop != (uid_t)-1 && setuid(drop))) + die(1, "couldn't drop privileges: %s", strerror(errno)); +#endif + + /* --- Let rip --- */ + + if (!(flags & FW_SET)) + moan("nothing to do!"); + signal(SIGPIPE, SIG_IGN); + + { + int selerr = 0; + while (active) { + if (!sel_select(sel)) + selerr = 0; + else if (errno != EINTR && errno != EAGAIN) { + fw_log(-1, "error from select: %s", strerror(errno)); + selerr++; + if (selerr > 8) { + fw_log(-1, "too many consecutive select errors: bailing out"); + exit(EXIT_FAILURE); + } + } + } + } + + return (0); +} + +/*----- That's all, folks -------------------------------------------------*/