xref: /illumos-gate/usr/src/lib/libwrap/options.c (revision 7c478bd9)
1 /*
2  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
3  * Use is subject to license terms.
4  */
5 
6 #pragma ident	"%Z%%M%	%I%	%E% SMI"
7 
8  /*
9   * General skeleton for adding options to the access control language. The
10   * features offered by this module are documented in the hosts_options(5)
11   * manual page (source file: hosts_options.5, "nroff -man" format).
12   *
13   * Notes and warnings for those who want to add features:
14   *
15   * In case of errors, abort options processing and deny access. There are too
16   * many irreversible side effects to make error recovery feasible. For
17   * example, it makes no sense to continue after we have already changed the
18   * userid.
19   *
20   * In case of errors, do not terminate the process: the routines might be
21   * called from a long-running daemon that should run forever. Instead, call
22   * tcpd_jump() which does a non-local goto back into the hosts_access()
23   * routine.
24   *
25   * In case of severe errors, use clean_exit() instead of directly calling
26   * exit(), or the inetd may loop on an UDP request.
27   *
28   * In verification mode (for example, with the "tcpdmatch" command) the
29   * "dry_run" flag is set. In this mode, an option function should just "say"
30   * what it is going to do instead of really doing it.
31   *
32   * Some option functions do not return (for example, the twist option passes
33   * control to another program). In verification mode (dry_run flag is set)
34   * such options should clear the "dry_run" flag to inform the caller of this
35   * course of action.
36   */
37 
38 #ifndef lint
39 static char sccsid[] = "@(#) options.c 1.17 96/02/11 17:01:31";
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 <stdlib.h>
52 #include <unistd.h>
53 #include <syslog.h>
54 #include <pwd.h>
55 #include <grp.h>
56 #include <ctype.h>
57 #include <setjmp.h>
58 #include <string.h>
59 
60 #ifndef MAXPATHNAMELEN
61 #define MAXPATHNAMELEN  BUFSIZ
62 #endif
63 
64 /* Local stuff. */
65 
66 #include "tcpd.h"
67 
68 /* Options runtime support. */
69 
70 int     dry_run = 0;			/* flag set in verification mode */
71 extern jmp_buf tcpd_buf;		/* tcpd_jump() support */
72 
73 /* Options parser support. */
74 
75 static char whitespace_eq[] = "= \t\r\n";
76 #define whitespace (whitespace_eq + 1)
77 
78 static char *get_field();		/* chew :-delimited field off string */
79 static char *chop_string();		/* strip leading and trailing blanks */
80 
81 /* List of functions that implement the options. Add yours here. */
82 
83 static void user_option();		/* execute "user name.group" option */
84 static void group_option();		/* execute "group name" option */
85 static void umask_option();		/* execute "umask mask" option */
86 static void linger_option();		/* execute "linger time" option */
87 static void keepalive_option();		/* execute "keepalive" option */
88 static void spawn_option();		/* execute "spawn command" option */
89 static void twist_option();		/* execute "twist command" option */
90 static void rfc931_option();		/* execute "rfc931" option */
91 static void setenv_option();		/* execute "setenv name value" */
92 static void nice_option();		/* execute "nice" option */
93 static void severity_option();		/* execute "severity value" */
94 static void allow_option();		/* execute "allow" option */
95 static void deny_option();		/* execute "deny" option */
96 static void banners_option();		/* execute "banners path" option */
97 
98 /* Structure of the options table. */
99 
100 struct option {
101     char   *name;			/* keyword name, case is ignored */
102     void  (*func) ();			/* function that does the real work */
103     int     flags;			/* see below... */
104 };
105 
106 #define NEED_ARG	(1<<1)		/* option requires argument */
107 #define USE_LAST	(1<<2)		/* option must be last */
108 #define OPT_ARG		(1<<3)		/* option has optional argument */
109 #define EXPAND_ARG	(1<<4)		/* do %x expansion on argument */
110 
111 #define need_arg(o)	((o)->flags & NEED_ARG)
112 #define opt_arg(o)	((o)->flags & OPT_ARG)
113 #define permit_arg(o)	((o)->flags & (NEED_ARG | OPT_ARG))
114 #define use_last(o)	((o)->flags & USE_LAST)
115 #define expand_arg(o)	((o)->flags & EXPAND_ARG)
116 
117 /* List of known keywords. Add yours here. */
118 
119 static struct option option_table[] = {
120     "user", user_option, NEED_ARG,
121     "group", group_option, NEED_ARG,
122     "umask", umask_option, NEED_ARG,
123     "linger", linger_option, NEED_ARG,
124     "keepalive", keepalive_option, 0,
125     "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
126     "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
127     "rfc931", rfc931_option, OPT_ARG,
128     "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
129     "nice", nice_option, OPT_ARG,
130     "severity", severity_option, NEED_ARG,
131     "allow", allow_option, USE_LAST,
132     "deny", deny_option, USE_LAST,
133     "banners", banners_option, NEED_ARG,
134     0,
135 };
136 
137 /* process_options - process access control options */
138 
process_options(options,request)139 void    process_options(options, request)
140 char   *options;
141 struct request_info *request;
142 {
143     char   *key;
144     char   *value;
145     char   *curr_opt;
146     char   *next_opt;
147     struct option *op;
148     char    bf[BUFSIZ];
149 
150     for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
151 	next_opt = get_field((char *) 0);
152 
153 	/*
154 	 * Separate the option into name and value parts. For backwards
155 	 * compatibility we ignore exactly one '=' between name and value.
156 	 */
157 	curr_opt = chop_string(curr_opt);
158 	if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
159 	    if (*value != '=') {
160 		*value++ = 0;
161 		value += strspn(value, whitespace);
162 	    }
163 	    if (*value == '=') {
164 		*value++ = 0;
165 		value += strspn(value, whitespace);
166 	    }
167 	}
168 	if (*value == 0)
169 	    value = 0;
170 	key = curr_opt;
171 
172 	/*
173 	 * Disallow missing option names (and empty option fields).
174 	 */
175 	if (*key == 0)
176 	    tcpd_jump("missing option name");
177 
178 	/*
179 	 * Lookup the option-specific info and do some common error checks.
180 	 * Delegate option-specific processing to the specific functions.
181 	 */
182 
183 	for (op = option_table; op->name && STR_NE(op->name, key); op++)
184 	     /* VOID */ ;
185 	if (op->name == 0)
186 	    tcpd_jump("bad option name: \"%s\"", key);
187 	if (!value && need_arg(op))
188 	    tcpd_jump("option \"%s\" requires value", key);
189 	if (value && !permit_arg(op))
190 	    tcpd_jump("option \"%s\" requires no value", key);
191 	if (next_opt && use_last(op))
192 	    tcpd_jump("option \"%s\" must be at end", key);
193 	if (value && expand_arg(op))
194 	    value = chop_string(percent_x(bf, sizeof(bf), value, request));
195 	if (hosts_access_verbose)
196 	    syslog(LOG_DEBUG, "option:   %s %s", key, value ? value : "");
197 	(*(op->func)) (value, request);
198     }
199 }
200 
201 /* allow_option - grant access */
202 
203 /* ARGSUSED */
204 
allow_option(value,request)205 static void allow_option(value, request)
206 char   *value;
207 struct request_info *request;
208 {
209     longjmp(tcpd_buf, AC_PERMIT);
210 }
211 
212 /* deny_option - deny access */
213 
214 /* ARGSUSED */
215 
deny_option(value,request)216 static void deny_option(value, request)
217 char   *value;
218 struct request_info *request;
219 {
220     longjmp(tcpd_buf, AC_DENY);
221 }
222 
223 /* banners_option - expand %<char>, terminate each line with CRLF */
224 
banners_option(value,request)225 static void banners_option(value, request)
226 char   *value;
227 struct request_info *request;
228 {
229     char    path[MAXPATHNAMELEN];
230     char    ibuf[BUFSIZ];
231     char    obuf[2 * BUFSIZ];
232     struct stat st;
233     int     ch;
234     FILE   *fp;
235 
236     sprintf(path, "%s/%s", value, eval_daemon(request));
237     if ((fp = fopen(path, "r")) != 0) {
238 	while ((ch = fgetc(fp)) == 0)
239 	    write(request->fd, "", 1);
240 	ungetc(ch, fp);
241 	while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
242 	    if (split_at(ibuf, '\n'))
243 		strcat(ibuf, "\r\n");
244 	    percent_x(obuf, sizeof(obuf), ibuf, request);
245 	    write(request->fd, obuf, strlen(obuf));
246 	}
247 	fclose(fp);
248     } else if (stat(value, &st) < 0) {
249 	tcpd_warn("%s: %m", value);
250     }
251 }
252 
253 /* group_option - switch group id */
254 
255 /* ARGSUSED */
256 
group_option(value,request)257 static void group_option(value, request)
258 char   *value;
259 struct request_info *request;
260 {
261     struct group *grp;
262     struct group *getgrnam();
263 
264     if ((grp = getgrnam(value)) == 0)
265 	tcpd_jump("unknown group: \"%s\"", value);
266     endgrent();
267 
268     if (dry_run == 0 && setgid(grp->gr_gid))
269 	tcpd_jump("setgid(%s): %m", value);
270 }
271 
272 /* user_option - switch user id */
273 
274 /* ARGSUSED */
275 
user_option(value,request)276 static void user_option(value, request)
277 char   *value;
278 struct request_info *request;
279 {
280     struct passwd *pwd;
281     struct passwd *getpwnam();
282     char   *group;
283 
284     if ((group = split_at(value, '.')) != 0)
285 	group_option(group, request);
286     if ((pwd = getpwnam(value)) == 0)
287 	tcpd_jump("unknown user: \"%s\"", value);
288     endpwent();
289 
290     if (dry_run == 0 && setuid(pwd->pw_uid))
291 	tcpd_jump("setuid(%s): %m", value);
292 }
293 
294 /* umask_option - set file creation mask */
295 
296 /* ARGSUSED */
297 
umask_option(value,request)298 static void umask_option(value, request)
299 char   *value;
300 struct request_info *request;
301 {
302     unsigned mask;
303     char    junk;
304 
305     if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
306 	tcpd_jump("bad umask value: \"%s\"", value);
307     (void) umask(mask);
308 }
309 
310 /* spawn_option - spawn a shell command and wait */
311 
312 /* ARGSUSED */
313 
spawn_option(value,request)314 static void spawn_option(value, request)
315 char   *value;
316 struct request_info *request;
317 {
318     if (dry_run == 0)
319 	shell_cmd(value);
320 }
321 
322 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
323 
324 /* ARGSUSED */
325 
linger_option(value,request)326 static void linger_option(value, request)
327 char   *value;
328 struct request_info *request;
329 {
330     struct linger linger;
331     char    junk;
332 
333     if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
334 	|| linger.l_linger < 0)
335 	tcpd_jump("bad linger value: \"%s\"", value);
336     if (dry_run == 0) {
337 	linger.l_onoff = (linger.l_linger != 0);
338 	if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
339 		       sizeof(linger)) < 0)
340 	    tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
341     }
342 }
343 
344 /* keepalive_option - set the socket keepalive option */
345 
346 /* ARGSUSED */
347 
keepalive_option(value,request)348 static void keepalive_option(value, request)
349 char   *value;
350 struct request_info *request;
351 {
352     static int on = 1;
353 
354     if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
355 				   (char *) &on, sizeof(on)) < 0)
356 	tcpd_warn("setsockopt SO_KEEPALIVE: %m");
357 }
358 
359 /* nice_option - set nice value */
360 
361 /* ARGSUSED */
362 
nice_option(value,request)363 static void nice_option(value, request)
364 char   *value;
365 struct request_info *request;
366 {
367     int     niceval = 10;
368     char    junk;
369 
370     if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
371 	tcpd_jump("bad nice value: \"%s\"", value);
372     if (dry_run == 0 && nice(niceval) < 0)
373 	tcpd_warn("nice(%d): %m", niceval);
374 }
375 
376 /* twist_option - replace process by shell command */
377 
twist_option(value,request)378 static void twist_option(value, request)
379 char   *value;
380 struct request_info *request;
381 {
382     char   *error;
383 
384     if (dry_run != 0) {
385 	dry_run = 0;
386     } else {
387 	if (resident > 0)
388 	    tcpd_jump("twist option in resident process");
389 
390 	syslog(deny_severity, "twist %s to %s", eval_client(request), value);
391 
392 	/* Before switching to the shell, set up stdin, stdout and stderr. */
393 
394 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
395 
396 	if (maybe_dup2(request->fd, 0) != 0 ||
397 	    maybe_dup2(request->fd, 1) != 1 ||
398 	    maybe_dup2(request->fd, 2) != 2) {
399 	    error = "twist_option: dup: %m";
400 	} else {
401 	    if (request->fd > 2)
402 		close(request->fd);
403 	    (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
404 	    error = "twist_option: /bin/sh: %m";
405 	}
406 
407 	/* Something went wrong: we MUST terminate the process. */
408 
409 	tcpd_warn(error);
410 	clean_exit(request);
411     }
412 }
413 
414 /* rfc931_option - look up remote user name */
415 
rfc931_option(value,request)416 static void rfc931_option(value, request)
417 char   *value;
418 struct request_info *request;
419 {
420     int     timeout;
421     char    junk;
422 
423     if (value != 0) {
424 	if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
425 	    tcpd_jump("bad rfc931 timeout: \"%s\"", value);
426 	rfc931_timeout = timeout;
427     }
428     (void) eval_user(request);
429 }
430 
431 /* setenv_option - set environment variable */
432 
433 /* ARGSUSED */
434 
setenv_option(value,request)435 static void setenv_option(value, request)
436 char   *value;
437 struct request_info *request;
438 {
439     extern int setenv(const char *, const char *, int);
440     char   *var_value;
441 
442     if (*(var_value = value + strcspn(value, whitespace)))
443 	*var_value++ = 0;
444     if (setenv(chop_string(value), chop_string(var_value), 1))
445 	tcpd_jump("memory allocation failure");
446 }
447 
448  /*
449   * The severity option goes last because it comes with a huge amount of ugly
450   * #ifdefs and tables.
451   */
452 
453 struct syslog_names {
454     char   *name;
455     int     value;
456 };
457 
458 static struct syslog_names log_fac[] = {
459 #ifdef LOG_KERN
460     "kern", LOG_KERN,
461 #endif
462 #ifdef LOG_USER
463     "user", LOG_USER,
464 #endif
465 #ifdef LOG_MAIL
466     "mail", LOG_MAIL,
467 #endif
468 #ifdef LOG_DAEMON
469     "daemon", LOG_DAEMON,
470 #endif
471 #ifdef LOG_AUTH
472     "auth", LOG_AUTH,
473 #endif
474 #ifdef LOG_LPR
475     "lpr", LOG_LPR,
476 #endif
477 #ifdef LOG_NEWS
478     "news", LOG_NEWS,
479 #endif
480 #ifdef LOG_UUCP
481     "uucp", LOG_UUCP,
482 #endif
483 #ifdef LOG_CRON
484     "cron", LOG_CRON,
485 #endif
486 #ifdef LOG_LOCAL0
487     "local0", LOG_LOCAL0,
488 #endif
489 #ifdef LOG_LOCAL1
490     "local1", LOG_LOCAL1,
491 #endif
492 #ifdef LOG_LOCAL2
493     "local2", LOG_LOCAL2,
494 #endif
495 #ifdef LOG_LOCAL3
496     "local3", LOG_LOCAL3,
497 #endif
498 #ifdef LOG_LOCAL4
499     "local4", LOG_LOCAL4,
500 #endif
501 #ifdef LOG_LOCAL5
502     "local5", LOG_LOCAL5,
503 #endif
504 #ifdef LOG_LOCAL6
505     "local6", LOG_LOCAL6,
506 #endif
507 #ifdef LOG_LOCAL7
508     "local7", LOG_LOCAL7,
509 #endif
510     0,
511 };
512 
513 static struct syslog_names log_sev[] = {
514 #ifdef LOG_EMERG
515     "emerg", LOG_EMERG,
516 #endif
517 #ifdef LOG_ALERT
518     "alert", LOG_ALERT,
519 #endif
520 #ifdef LOG_CRIT
521     "crit", LOG_CRIT,
522 #endif
523 #ifdef LOG_ERR
524     "err", LOG_ERR,
525 #endif
526 #ifdef LOG_WARNING
527     "warning", LOG_WARNING,
528 #endif
529 #ifdef LOG_NOTICE
530     "notice", LOG_NOTICE,
531 #endif
532 #ifdef LOG_INFO
533     "info", LOG_INFO,
534 #endif
535 #ifdef LOG_DEBUG
536     "debug", LOG_DEBUG,
537 #endif
538     0,
539 };
540 
541 /* severity_map - lookup facility or severity value */
542 
severity_map(table,name)543 static int severity_map(table, name)
544 struct syslog_names *table;
545 char   *name;
546 {
547     struct syslog_names *t;
548 
549     for (t = table; t->name; t++)
550 	if (STR_EQ(t->name, name))
551 	    return (t->value);
552     tcpd_jump("bad syslog facility or severity: \"%s\"", name);
553     /* NOTREACHED */
554 }
555 
556 /* severity_option - change logging severity for this event (Dave Mitchell) */
557 
558 /* ARGSUSED */
559 
severity_option(value,request)560 static void severity_option(value, request)
561 char   *value;
562 struct request_info *request;
563 {
564     char   *level = split_at(value, '.');
565 
566     allow_severity = deny_severity = level ?
567 	severity_map(log_fac, value) | severity_map(log_sev, level) :
568 	severity_map(log_sev, value);
569 }
570 
571 /* get_field - return pointer to next field in string */
572 
get_field(string)573 static char *get_field(string)
574 char   *string;
575 {
576     static char *last = "";
577     char   *src;
578     char   *dst;
579     char   *ret;
580     int     ch;
581 
582     /*
583      * This function returns pointers to successive fields within a given
584      * string. ":" is the field separator; warn if the rule ends in one. It
585      * replaces a "\:" sequence by ":", without treating the result of
586      * substitution as field terminator. A null argument means resume search
587      * where the previous call terminated. This function destroys its
588      * argument.
589      *
590      * Work from explicit source or from memory. While processing \: we
591      * overwrite the input. This way we do not have to maintain buffers for
592      * copies of input fields.
593      */
594 
595     src = dst = ret = (string ? string : last);
596     if (src[0] == 0)
597 	return (0);
598 
599     while (ch = *src) {
600 	if (ch == ':') {
601 	    if (*++src == 0)
602 		tcpd_warn("rule ends in \":\"");
603 	    break;
604 	}
605 	if (ch == '\\' && src[1] == ':')
606 	    src++;
607 	*dst++ = *src++;
608     }
609     last = src;
610     *dst = 0;
611     return (ret);
612 }
613 
614 /* chop_string - strip leading and trailing blanks from string */
615 
chop_string(string)616 static char *chop_string(string)
617 register char *string;
618 {
619     char   *start = 0;
620     char   *end;
621     char   *cp;
622 
623     for (cp = string; *cp; cp++) {
624 	if (!isspace(*cp)) {
625 	    if (start == 0)
626 		start = cp;
627 	    end = cp;
628 	}
629     }
630     return (start ? (end[1] = 0, start) : cp);
631 }
632