1 /* $NetBSD: options.c,v 1.16 2012/03/22 22:59:43 joerg Exp $ */
2
3 /*
4 * General skeleton for adding options to the access control language. The
5 * features offered by this module are documented in the hosts_options(5)
6 * manual page (source file: hosts_options.5, "nroff -man" format).
7 *
8 * Notes and warnings for those who want to add features:
9 *
10 * In case of errors, abort options processing and deny access. There are too
11 * many irreversible side effects to make error recovery feasible. For
12 * example, it makes no sense to continue after we have already changed the
13 * userid.
14 *
15 * In case of errors, do not terminate the process: the routines might be
16 * called from a long-running daemon that should run forever. Instead, call
17 * tcpd_jump() which does a non-local goto back into the hosts_access()
18 * routine.
19 *
20 * In case of severe errors, use clean_exit() instead of directly calling
21 * exit(), or the inetd may loop on an UDP request.
22 *
23 * In verification mode (for example, with the "tcpdmatch" command) the
24 * "dry_run" flag is set. In this mode, an option function should just "say"
25 * what it is going to do instead of really doing it.
26 *
27 * Some option functions do not return (for example, the twist option passes
28 * control to another program). In verification mode (dry_run flag is set)
29 * such options should clear the "dry_run" flag to inform the caller of this
30 * course of action.
31 */
32
33 #include <sys/cdefs.h>
34 #ifndef lint
35 #if 0
36 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
37 #else
38 __RCSID("$NetBSD: options.c,v 1.16 2012/03/22 22:59:43 joerg Exp $");
39 #endif
40 #endif
41
42 /* System libraries. */
43
44 #include <sys/types.h>
45 #include <sys/param.h>
46 #include <sys/socket.h>
47 #include <sys/stat.h>
48 #include <netinet/in.h>
49 #include <netdb.h>
50 #include <stdio.h>
51 #include <syslog.h>
52 #include <unistd.h>
53 #include <stdlib.h>
54 #include <pwd.h>
55 #include <grp.h>
56 #include <ctype.h>
57 #include <setjmp.h>
58 #include <string.h>
59
60 /* Local stuff. */
61
62 #include "tcpd.h"
63
64 /* Options runtime support. */
65
66 int dry_run = 0; /* flag set in verification mode */
67 extern jmp_buf tcpd_buf; /* tcpd_jump() support */
68
69 /* Options parser support. */
70
71 static char whitespace_eq[] = "= \t\r\n";
72 #define whitespace (whitespace_eq + 1)
73
74 static char *get_field /* chew :-delimited field off string */
75 (char *);
76 static char *chop_string /* strip leading and trailing blanks */
77 (char *);
78 struct syslog_names;
79 static int severity_map
80 (const struct syslog_names *, char *);
81
82 /* List of functions that implement the options. Add yours here. */
83
84 static void user_option /* execute "user name.group" option */
85 (char *, struct request_info *);
86 static void group_option /* execute "group name" option */
87 (char *, struct request_info *);
88 static void umask_option /* execute "umask mask" option */
89 (char *, struct request_info *);
90 static void linger_option /* execute "linger time" option */
91 (char *, struct request_info *);
92 static void keepalive_option /* execute "keepalive" option */
93 (char *, struct request_info *);
94 static void spawn_option /* execute "spawn command" option */
95 (char *, struct request_info *);
96 static void twist_option /* execute "twist command" option */
97 (char *, struct request_info *);
98 static void rfc931_option /* execute "rfc931" option */
99 (char *, struct request_info *);
100 static void setenv_option /* execute "setenv name value" */
101 (char *, struct request_info *);
102 static void nice_option /* execute "nice" option */
103 (char *, struct request_info *);
104 static void severity_option /* execute "severity value" */
105 (char *, struct request_info *);
106 __dead static void allow_option /* execute "allow" option */
107 (char *, struct request_info *);
108 __dead static void deny_option /* execute "deny" option */
109 (char *, struct request_info *);
110 static void banners_option /* execute "banners path" option */
111 (char *, struct request_info *);
112
113 /* Structure of the options table. */
114
115 struct option {
116 const char *name; /* keyword name, case is ignored */
117 void (*func) /* function that does the real work */
118 (char *, struct request_info *);
119 int flags; /* see below... */
120 };
121
122 #define NEED_ARG (1<<1) /* option requires argument */
123 #define USE_LAST (1<<2) /* option must be last */
124 #define OPT_ARG (1<<3) /* option has optional argument */
125 #define EXPAND_ARG (1<<4) /* do %x expansion on argument */
126
127 #define need_arg(o) ((o)->flags & NEED_ARG)
128 #define opt_arg(o) ((o)->flags & OPT_ARG)
129 #define permit_arg(o) ((o)->flags & (NEED_ARG | OPT_ARG))
130 #define use_last(o) ((o)->flags & USE_LAST)
131 #define expand_arg(o) ((o)->flags & EXPAND_ARG)
132
133 /* List of known keywords. Add yours here. */
134
135 static struct option option_table[] = {
136 { "user", user_option, NEED_ARG },
137 { "group", group_option, NEED_ARG },
138 { "umask", umask_option, NEED_ARG },
139 { "linger", linger_option, NEED_ARG },
140 { "keepalive", keepalive_option, 0 },
141 { "spawn", spawn_option, NEED_ARG | EXPAND_ARG },
142 { "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST },
143 { "rfc931", rfc931_option, OPT_ARG },
144 { "setenv", setenv_option, NEED_ARG | EXPAND_ARG },
145 { "nice", nice_option, OPT_ARG },
146 { "severity", severity_option, NEED_ARG },
147 { "allow", allow_option, USE_LAST },
148 { "deny", deny_option, USE_LAST },
149 { "banners", banners_option, NEED_ARG },
150 { NULL, NULL, 0 }
151 };
152
153 /* process_options - process access control options */
154
155 void
process_options(char * options,struct request_info * request)156 process_options(char *options, struct request_info *request)
157 {
158 char *key;
159 char *value;
160 char *curr_opt;
161 char *next_opt;
162 struct option *op;
163 char bf[BUFSIZ];
164
165 for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
166 next_opt = get_field((char *) 0);
167
168 /*
169 * Separate the option into name and value parts. For backwards
170 * compatibility we ignore exactly one '=' between name and value.
171 */
172 curr_opt = chop_string(curr_opt);
173 if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
174 if (*value != '=') {
175 *value++ = 0;
176 value += strspn(value, whitespace);
177 }
178 if (*value == '=') {
179 *value++ = 0;
180 value += strspn(value, whitespace);
181 }
182 }
183 if (*value == 0)
184 value = 0;
185 key = curr_opt;
186
187 /*
188 * Disallow missing option names (and empty option fields).
189 */
190 if (*key == 0)
191 tcpd_jump("missing option name");
192
193 /*
194 * Lookup the option-specific info and do some common error checks.
195 * Delegate option-specific processing to the specific functions.
196 */
197
198 for (op = option_table; op->name && STR_NE(op->name, key); op++)
199 /* VOID */ ;
200 if (op->name == 0)
201 tcpd_jump("bad option name: \"%s\"", key);
202 if (!value && need_arg(op))
203 tcpd_jump("option \"%s\" requires value", key);
204 if (value && !permit_arg(op))
205 tcpd_jump("option \"%s\" requires no value", key);
206 if (next_opt && use_last(op))
207 tcpd_jump("option \"%s\" must be at end", key);
208 if (value && expand_arg(op))
209 value = chop_string(percent_x(bf, sizeof(bf), value, request));
210 if (hosts_access_verbose)
211 syslog(LOG_DEBUG, "option: %s %s", key, value ? value : "");
212 (*(op->func)) (value, request);
213 }
214 }
215
216 /* allow_option - grant access */
217
218 /* ARGSUSED */
219
220 static void
allow_option(char * value,struct request_info * request)221 allow_option(char *value, struct request_info *request)
222 {
223 longjmp(tcpd_buf, AC_PERMIT);
224 }
225
226 /* deny_option - deny access */
227
228 /* ARGSUSED */
229
230 static void
deny_option(char * value,struct request_info * request)231 deny_option(char *value, struct request_info *request)
232 {
233 longjmp(tcpd_buf, AC_DENY);
234 }
235
236 /* banners_option - expand %<char>, terminate each line with CRLF */
237
238 static void
banners_option(char * value,struct request_info * request)239 banners_option(char *value, struct request_info *request)
240 {
241 char path[MAXPATHLEN];
242 char ibuf[BUFSIZ];
243 char obuf[2 * BUFSIZ];
244 struct stat st;
245 int ch;
246 FILE *fp;
247
248 (void)snprintf(path, sizeof path, "%s/%s", value, eval_daemon(request));
249 if ((fp = fopen(path, "r")) != 0) {
250 while ((ch = fgetc(fp)) == 0)
251 write(request->fd, "", 1);
252 ungetc(ch, fp);
253 while (fgets(ibuf, sizeof(ibuf) - 2, fp)) {
254 if (split_at(ibuf, '\n'))
255 strcat(ibuf, "\r\n"); /* XXX strcat is safe */
256 percent_x(obuf, sizeof(obuf), ibuf, request);
257 write(request->fd, obuf, strlen(obuf));
258 }
259 fclose(fp);
260 } else if (stat(value, &st) < 0) {
261 tcpd_warn("%s: %m", value);
262 }
263 }
264
265 /* group_option - switch group id */
266
267 /* ARGSUSED */
268
269 static void
group_option(char * value,struct request_info * request)270 group_option(char *value, struct request_info *request)
271 {
272 struct group grs, *grp;
273 char grbuf[1024];
274
275 (void)getgrnam_r(value, &grs, grbuf, sizeof(grbuf), &grp);
276 if (grp == NULL)
277 tcpd_jump("unknown group: \"%s\"", value);
278
279 if (dry_run == 0 && setgid(grp->gr_gid))
280 tcpd_jump("setgid(%s): %m", value);
281 }
282
283 /* user_option - switch user id */
284
285 /* ARGSUSED */
286
287 static void
user_option(char * value,struct request_info * request)288 user_option(char *value, struct request_info *request)
289 {
290 struct passwd *pwd, pws;
291 char *group;
292 char pwbuf[1024];
293
294 if ((group = split_at(value, '.')) != 0)
295 group_option(group, request);
296 (void)getpwnam_r(value, &pws, pwbuf, sizeof(pwbuf), &pwd);
297 if (pwd == NULL)
298 tcpd_jump("unknown user: \"%s\"", value);
299
300 if (dry_run == 0 && setuid(pwd->pw_uid))
301 tcpd_jump("setuid(%s): %m", value);
302 }
303
304 /* umask_option - set file creation mask */
305
306 /* ARGSUSED */
307
308 static void
umask_option(char * value,struct request_info * request)309 umask_option(char *value, struct request_info *request)
310 {
311 unsigned mask;
312 char junk;
313
314 if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
315 tcpd_jump("bad umask value: \"%s\"", value);
316 (void) umask(mask);
317 }
318
319 /* spawn_option - spawn a shell command and wait */
320
321 /* ARGSUSED */
322
323 static void
spawn_option(char * value,struct request_info * request)324 spawn_option(char *value, struct request_info *request)
325 {
326 if (dry_run == 0)
327 shell_cmd(value);
328 }
329
330 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
331
332 /* ARGSUSED */
333
334 static void
linger_option(char * value,struct request_info * request)335 linger_option(char *value, struct request_info *request)
336 {
337 struct linger linger;
338 char junk;
339
340 if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
341 || linger.l_linger < 0)
342 tcpd_jump("bad linger value: \"%s\"", value);
343 if (dry_run == 0) {
344 linger.l_onoff = (linger.l_linger != 0);
345 if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
346 sizeof(linger)) < 0)
347 tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
348 }
349 }
350
351 /* keepalive_option - set the socket keepalive option */
352
353 /* ARGSUSED */
354
355 static void
keepalive_option(char * value,struct request_info * request)356 keepalive_option(char *value, struct request_info *request)
357 {
358 static int on = 1;
359
360 if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
361 (char *) &on, sizeof(on)) < 0)
362 tcpd_warn("setsockopt SO_KEEPALIVE: %m");
363 }
364
365 /* nice_option - set nice value */
366
367 /* ARGSUSED */
368
369 static void
nice_option(char * value,struct request_info * request)370 nice_option(char *value, struct request_info *request)
371 {
372 int niceval = 10;
373 char junk;
374
375 if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
376 tcpd_jump("bad nice value: \"%s\"", value);
377 if (dry_run == 0 && nice(niceval) < 0)
378 tcpd_warn("nice(%d): %m", niceval);
379 }
380
381 /* twist_option - replace process by shell command */
382
383 static void
twist_option(char * value,struct request_info * request)384 twist_option(char *value, struct request_info *request)
385 {
386 if (dry_run != 0) {
387 dry_run = 0;
388 } else {
389 if (resident > 0)
390 tcpd_jump("twist option in resident process");
391
392 syslog(deny_severity, "twist %s to %s", eval_client(request), value);
393
394 /* Before switching to the shell, set up stdin, stdout and stderr. */
395
396 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
397
398 if (maybe_dup2(request->fd, 0) != 0 ||
399 maybe_dup2(request->fd, 1) != 1 ||
400 maybe_dup2(request->fd, 2) != 2) {
401 tcpd_warn("twist_option: dup: %m");
402 } else {
403 if (request->fd > 2)
404 close(request->fd);
405 (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
406 tcpd_warn("twist_option: /bin/sh: %m");
407 }
408
409 /* Something went wrong: we MUST terminate the process. */
410 clean_exit(request);
411 }
412 }
413
414 /* rfc931_option - look up remote user name */
415
416 static void
rfc931_option(char * value,struct request_info * request)417 rfc931_option(char *value, struct request_info *request)
418 {
419 int timeout;
420 char junk;
421
422 if (value != 0) {
423 if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
424 tcpd_jump("bad rfc931 timeout: \"%s\"", value);
425 rfc931_timeout = timeout;
426 }
427 (void) eval_user(request);
428 }
429
430 /* setenv_option - set environment variable */
431
432 /* ARGSUSED */
433
434 static void
setenv_option(char * value,struct request_info * request)435 setenv_option(char *value, struct request_info *request)
436 {
437 char *var_value;
438
439 if (*(var_value = value + strcspn(value, whitespace)))
440 *var_value++ = 0;
441 if (setenv(chop_string(value), chop_string(var_value), 1))
442 tcpd_jump("memory allocation failure");
443 }
444
445 /*
446 * The severity option goes last because it comes with a huge amount of ugly
447 * #ifdefs and tables.
448 */
449
450 struct syslog_names {
451 const char *name;
452 int value;
453 };
454
455 static const struct syslog_names log_fac[] = {
456 #ifdef LOG_KERN
457 { "kern", LOG_KERN },
458 #endif
459 #ifdef LOG_USER
460 { "user", LOG_USER },
461 #endif
462 #ifdef LOG_MAIL
463 { "mail", LOG_MAIL },
464 #endif
465 #ifdef LOG_DAEMON
466 { "daemon", LOG_DAEMON },
467 #endif
468 #ifdef LOG_AUTH
469 { "auth", LOG_AUTH },
470 #endif
471 #ifdef LOG_LPR
472 { "lpr", LOG_LPR },
473 #endif
474 #ifdef LOG_NEWS
475 { "news", LOG_NEWS },
476 #endif
477 #ifdef LOG_UUCP
478 { "uucp", LOG_UUCP },
479 #endif
480 #ifdef LOG_CRON
481 { "cron", LOG_CRON },
482 #endif
483 #ifdef LOG_AUTHPRIV
484 { "authpriv", LOG_AUTHPRIV },
485 #endif
486 #ifdef LOG_FTP
487 { "ftp", LOG_FTP },
488 #endif
489 #ifdef LOG_LOCAL0
490 { "local0", LOG_LOCAL0 },
491 #endif
492 #ifdef LOG_LOCAL1
493 { "local1", LOG_LOCAL1 },
494 #endif
495 #ifdef LOG_LOCAL2
496 { "local2", LOG_LOCAL2 },
497 #endif
498 #ifdef LOG_LOCAL3
499 { "local3", LOG_LOCAL3 },
500 #endif
501 #ifdef LOG_LOCAL4
502 { "local4", LOG_LOCAL4 },
503 #endif
504 #ifdef LOG_LOCAL5
505 { "local5", LOG_LOCAL5 },
506 #endif
507 #ifdef LOG_LOCAL6
508 { "local6", LOG_LOCAL6 },
509 #endif
510 #ifdef LOG_LOCAL7
511 { "local7", LOG_LOCAL7 },
512 #endif
513 { NULL, 0 }
514 };
515
516 static const struct syslog_names log_sev[] = {
517 #ifdef LOG_EMERG
518 { "emerg", LOG_EMERG },
519 #endif
520 #ifdef LOG_ALERT
521 { "alert", LOG_ALERT },
522 #endif
523 #ifdef LOG_CRIT
524 { "crit", LOG_CRIT },
525 #endif
526 #ifdef LOG_ERR
527 { "err", LOG_ERR },
528 #endif
529 #ifdef LOG_WARNING
530 { "warning", LOG_WARNING },
531 #endif
532 #ifdef LOG_NOTICE
533 { "notice", LOG_NOTICE },
534 #endif
535 #ifdef LOG_INFO
536 { "info", LOG_INFO },
537 #endif
538 #ifdef LOG_DEBUG
539 { "debug", LOG_DEBUG },
540 #endif
541 { NULL, 0 }
542 };
543
544 /* severity_map - lookup facility or severity value */
545
546 static int
severity_map(const struct syslog_names * table,char * name)547 severity_map(const struct syslog_names *table, char *name)
548 {
549 const struct syslog_names *t;
550
551 for (t = table; t->name; t++)
552 if (STR_EQ(t->name, name))
553 return (t->value);
554 tcpd_jump("bad syslog facility or severity: \"%s\"", name);
555 /* NOTREACHED */
556 return -1;
557 }
558
559 /* severity_option - change logging severity for this event (Dave Mitchell) */
560
561 /* ARGSUSED */
562
563 static void
severity_option(char * value,struct request_info * request)564 severity_option(char *value, struct request_info *request)
565 {
566 char *level = split_at(value, '.');
567
568 allow_severity = deny_severity = level ?
569 severity_map(log_fac, value) | severity_map(log_sev, level) :
570 severity_map(log_sev, value);
571 }
572
573 /* get_field - return pointer to next field in string */
574
575 static char *
get_field(char * string)576 get_field(char *string)
577 {
578 static char nul = '\0';
579 static char *last = &nul;
580 char *src;
581 char *dst;
582 char *ret;
583 int ch;
584
585 /*
586 * This function returns pointers to successive fields within a given
587 * string. ":" is the field separator; warn if the rule ends in one. It
588 * replaces a "\:" sequence by ":", without treating the result of
589 * substitution as field terminator. A null argument means resume search
590 * where the previous call terminated. This function destroys its
591 * argument.
592 *
593 * Work from explicit source or from memory. While processing \: we
594 * overwrite the input. This way we do not have to maintain buffers for
595 * copies of input fields.
596 */
597
598 src = dst = ret = (string ? string : last);
599 if (src[0] == 0)
600 return (0);
601
602 while ((ch = *src) != '\0') {
603 if (ch == ':') {
604 if (*++src == 0)
605 tcpd_warn("rule ends in \":\"");
606 break;
607 }
608 if (ch == '\\' && src[1] == ':')
609 src++;
610 *dst++ = *src++;
611 }
612 last = src;
613 *dst = 0;
614 return (ret);
615 }
616
617 /* chop_string - strip leading and trailing blanks from string */
618
619 static char *
chop_string(register char * string)620 chop_string(register char *string)
621 {
622 char *start = NULL;
623 char *end = NULL;
624 char *cp;
625
626 for (cp = string; *cp; cp++) {
627 if (!isspace((unsigned char) *cp)) {
628 if (start == 0)
629 start = cp;
630 end = cp;
631 }
632 }
633 return (start ? (end[1] = 0, start) : cp);
634 }
635