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