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(char *, struct request_info *); /* user name.group */
80 static void group_option(char *, struct request_info *); /* group name */
81 static void umask_option(char *, struct request_info *); /* umask mask */
82 static void linger_option(char *, struct request_info *); /* linger time */
83 static void keepalive_option(char *, struct request_info *); /* keepalive */
84 static void spawn_option(char *, struct request_info *); /* spawn command */
85 static void twist_option(char *, struct request_info *); /* twist command */
86 static void rfc931_option(char *, struct request_info *); /* rfc931 */
87 static void setenv_option(char *, struct request_info *); /* setenv name value */
88 static void nice_option(char *, struct request_info *); /* nice */
89 static void severity_option(char *, struct request_info *); /* severity value */
90 static void allow_option(char *, struct request_info *); /* allow */
91 static void deny_option(char *, struct request_info *); /* deny */
92 static void banners_option(char *, struct request_info *); /* banners path */
93
94 /* Structure of the options table. */
95
96 struct option {
97 char *name; /* keyword name, case is ignored */
98 void (*func) (char *value, struct request_info *request);
99 /* function that does the real work */
100 int flags; /* see below... */
101 };
102
103 #define NEED_ARG (1<<1) /* option requires argument */
104 #define USE_LAST (1<<2) /* option must be last */
105 #define OPT_ARG (1<<3) /* option has optional argument */
106 #define EXPAND_ARG (1<<4) /* do %x expansion on argument */
107
108 #define need_arg(o) ((o)->flags & NEED_ARG)
109 #define opt_arg(o) ((o)->flags & OPT_ARG)
110 #define permit_arg(o) ((o)->flags & (NEED_ARG | OPT_ARG))
111 #define use_last(o) ((o)->flags & USE_LAST)
112 #define expand_arg(o) ((o)->flags & EXPAND_ARG)
113
114 /* List of known keywords. Add yours here. */
115
116 static struct option option_table[] = {
117 "user", user_option, NEED_ARG,
118 "group", group_option, NEED_ARG,
119 "umask", umask_option, NEED_ARG,
120 "linger", linger_option, NEED_ARG,
121 "keepalive", keepalive_option, 0,
122 "spawn", spawn_option, NEED_ARG | EXPAND_ARG,
123 "twist", twist_option, NEED_ARG | EXPAND_ARG | USE_LAST,
124 "rfc931", rfc931_option, OPT_ARG,
125 "setenv", setenv_option, NEED_ARG | EXPAND_ARG,
126 "nice", nice_option, OPT_ARG,
127 "severity", severity_option, NEED_ARG,
128 "allow", allow_option, USE_LAST,
129 "deny", deny_option, USE_LAST,
130 "banners", banners_option, NEED_ARG,
131 0,
132 };
133
134 /* process_options - process access control options */
135
process_options(char * options,struct request_info * request)136 void process_options(char *options, struct request_info *request)
137 {
138 char *key;
139 char *value;
140 char *curr_opt;
141 char *next_opt;
142 struct option *op;
143 char bf[BUFSIZ];
144
145 for (curr_opt = get_field(options); curr_opt; curr_opt = next_opt) {
146 next_opt = get_field((char *) 0);
147
148 /*
149 * Separate the option into name and value parts. For backwards
150 * compatibility we ignore exactly one '=' between name and value.
151 */
152 curr_opt = chop_string(curr_opt);
153 if (*(value = curr_opt + strcspn(curr_opt, whitespace_eq))) {
154 if (*value != '=') {
155 *value++ = 0;
156 value += strspn(value, whitespace);
157 }
158 if (*value == '=') {
159 *value++ = 0;
160 value += strspn(value, whitespace);
161 }
162 }
163 if (*value == 0)
164 value = 0;
165 key = curr_opt;
166
167 /*
168 * Disallow missing option names (and empty option fields).
169 */
170 if (*key == 0)
171 tcpd_jump("missing option name");
172
173 /*
174 * Lookup the option-specific info and do some common error checks.
175 * Delegate option-specific processing to the specific functions.
176 */
177
178 for (op = option_table; op->name && STR_NE(op->name, key); op++)
179 /* VOID */ ;
180 if (op->name == 0)
181 tcpd_jump("bad option name: \"%s\"", key);
182 if (!value && need_arg(op))
183 tcpd_jump("option \"%s\" requires value", key);
184 if (value && !permit_arg(op))
185 tcpd_jump("option \"%s\" requires no value", key);
186 if (next_opt && use_last(op))
187 tcpd_jump("option \"%s\" must be at end", key);
188 if (value && expand_arg(op))
189 value = chop_string(percent_x(bf, sizeof(bf), value, request));
190 if (hosts_access_verbose)
191 syslog(LOG_DEBUG, "option: %s %s", key, value ? value : "");
192 (*(op->func)) (value, request);
193 }
194 }
195
196 /* allow_option - grant access */
197
198 /* ARGSUSED */
199
allow_option(char * value,struct request_info * request)200 static void allow_option(char *value, struct request_info *request)
201 {
202 longjmp(tcpd_buf, AC_PERMIT);
203 }
204
205 /* deny_option - deny access */
206
207 /* ARGSUSED */
208
deny_option(char * value,struct request_info * request)209 static void deny_option(char *value, struct request_info *request)
210 {
211 longjmp(tcpd_buf, AC_DENY);
212 }
213
214 /* banners_option - expand %<char>, terminate each line with CRLF */
215
banners_option(char * value,struct request_info * request)216 static void banners_option(char *value, struct request_info *request)
217 {
218 char path[MAXPATHNAMELEN];
219 char ibuf[BUFSIZ];
220 char obuf[2 * BUFSIZ];
221 struct stat st;
222 int ch;
223 FILE *fp;
224
225 sprintf(path, "%s/%s", value, eval_daemon(request));
226 if ((fp = fopen(path, "r")) != 0) {
227 while ((ch = fgetc(fp)) == 0)
228 write(request->fd, "", 1);
229 ungetc(ch, fp);
230 while (fgets(ibuf, sizeof(ibuf) - 1, fp)) {
231 if (split_at(ibuf, '\n'))
232 strcat(ibuf, "\r\n");
233 percent_x(obuf, sizeof(obuf), ibuf, request);
234 write(request->fd, obuf, strlen(obuf));
235 }
236 fclose(fp);
237 } else if (stat(value, &st) < 0) {
238 tcpd_warn("%s: %m", value);
239 }
240 }
241
242 /* group_option - switch group id */
243
244 /* ARGSUSED */
245
group_option(char * value,struct request_info * request)246 static void group_option(char *value, struct request_info *request)
247 {
248 struct group *grp;
249
250 if ((grp = getgrnam(value)) == 0)
251 tcpd_jump("unknown group: \"%s\"", value);
252 endgrent();
253
254 if (dry_run == 0 && setgid(grp->gr_gid))
255 tcpd_jump("setgid(%s): %m", value);
256 }
257
258 /* user_option - switch user id */
259
260 /* ARGSUSED */
261
user_option(char * value,struct request_info * request)262 static void user_option(char *value, struct request_info *request)
263 {
264 struct passwd *pwd;
265 char *group;
266
267 if ((group = split_at(value, '.')) != 0)
268 group_option(group, request);
269 if ((pwd = getpwnam(value)) == 0)
270 tcpd_jump("unknown user: \"%s\"", value);
271 endpwent();
272
273 if (dry_run == 0 && setuid(pwd->pw_uid))
274 tcpd_jump("setuid(%s): %m", value);
275 }
276
277 /* umask_option - set file creation mask */
278
279 /* ARGSUSED */
280
umask_option(char * value,struct request_info * request)281 static void umask_option(char *value, struct request_info *request)
282 {
283 unsigned mask;
284 char junk;
285
286 if (sscanf(value, "%o%c", &mask, &junk) != 1 || (mask & 0777) != mask)
287 tcpd_jump("bad umask value: \"%s\"", value);
288 (void) umask(mask);
289 }
290
291 /* spawn_option - spawn a shell command and wait */
292
293 /* ARGSUSED */
294
spawn_option(char * value,struct request_info * request)295 static void spawn_option(char *value, struct request_info *request)
296 {
297 if (dry_run == 0)
298 shell_cmd(value);
299 }
300
301 /* linger_option - set the socket linger time (Marc Boucher <marc@cam.org>) */
302
303 /* ARGSUSED */
304
linger_option(char * value,struct request_info * request)305 static void linger_option(char *value, struct request_info *request)
306 {
307 struct linger linger;
308 char junk;
309
310 if (sscanf(value, "%d%c", &linger.l_linger, &junk) != 1
311 || linger.l_linger < 0)
312 tcpd_jump("bad linger value: \"%s\"", value);
313 if (dry_run == 0) {
314 linger.l_onoff = (linger.l_linger != 0);
315 if (setsockopt(request->fd, SOL_SOCKET, SO_LINGER, (char *) &linger,
316 sizeof(linger)) < 0)
317 tcpd_warn("setsockopt SO_LINGER %d: %m", linger.l_linger);
318 }
319 }
320
321 /* keepalive_option - set the socket keepalive option */
322
323 /* ARGSUSED */
324
keepalive_option(char * value,struct request_info * request)325 static void keepalive_option(char *value, struct request_info *request)
326 {
327 static int on = 1;
328
329 if (dry_run == 0 && setsockopt(request->fd, SOL_SOCKET, SO_KEEPALIVE,
330 (char *) &on, sizeof(on)) < 0)
331 tcpd_warn("setsockopt SO_KEEPALIVE: %m");
332 }
333
334 /* nice_option - set nice value */
335
336 /* ARGSUSED */
337
nice_option(char * value,struct request_info * request)338 static void nice_option(char *value, struct request_info *request)
339 {
340 int niceval = 10;
341 char junk;
342
343 if (value != 0 && sscanf(value, "%d%c", &niceval, &junk) != 1)
344 tcpd_jump("bad nice value: \"%s\"", value);
345 if (dry_run == 0 && nice(niceval) < 0)
346 tcpd_warn("nice(%d): %m", niceval);
347 }
348
349 /* twist_option - replace process by shell command */
350
twist_option(char * value,struct request_info * request)351 static void twist_option(char *value, struct request_info *request)
352 {
353 char *error;
354
355 if (dry_run != 0) {
356 dry_run = 0;
357 } else {
358 if (resident > 0)
359 tcpd_jump("twist option in resident process");
360
361 syslog(deny_severity, "twist %s to %s", eval_client(request), value);
362
363 /* Before switching to the shell, set up stdin, stdout and stderr. */
364
365 #define maybe_dup2(from, to) ((from == to) ? to : (close(to), dup(from)))
366
367 if (maybe_dup2(request->fd, 0) != 0 ||
368 maybe_dup2(request->fd, 1) != 1 ||
369 maybe_dup2(request->fd, 2) != 2) {
370 error = "twist_option: dup: %m";
371 } else {
372 if (request->fd > 2)
373 close(request->fd);
374 (void) execl("/bin/sh", "sh", "-c", value, (char *) 0);
375 error = "twist_option: /bin/sh: %m";
376 }
377
378 /* Something went wrong: we MUST terminate the process. */
379
380 tcpd_warn(error);
381 clean_exit(request);
382 }
383 }
384
385 /* rfc931_option - look up remote user name */
386
rfc931_option(char * value,struct request_info * request)387 static void rfc931_option(char *value, struct request_info *request)
388 {
389 int timeout;
390 char junk;
391
392 if (value != 0) {
393 if (sscanf(value, "%d%c", &timeout, &junk) != 1 || timeout <= 0)
394 tcpd_jump("bad rfc931 timeout: \"%s\"", value);
395 rfc931_timeout = timeout;
396 }
397 (void) eval_user(request);
398 }
399
400 /* setenv_option - set environment variable */
401
402 /* ARGSUSED */
403
setenv_option(char * value,struct request_info * request)404 static void setenv_option(char *value, struct request_info *request)
405 {
406 char *var_value;
407
408 if (*(var_value = value + strcspn(value, whitespace)))
409 *var_value++ = 0;
410 if (setenv(chop_string(value), chop_string(var_value), 1))
411 tcpd_jump("memory allocation failure");
412 }
413
414 /* severity_map - lookup facility or severity value */
415
severity_map(const CODE * table,char * name)416 static int severity_map(const CODE *table, char *name)
417 {
418 const CODE *t;
419 int ret = -1;
420
421 for (t = table; t->c_name; t++)
422 if (STR_EQ(t->c_name, name)) {
423 ret = t->c_val;
424 break;
425 }
426 if (ret == -1)
427 tcpd_jump("bad syslog facility or severity: \"%s\"", name);
428
429 return (ret);
430 }
431
432 /* severity_option - change logging severity for this event (Dave Mitchell) */
433
434 /* ARGSUSED */
435
severity_option(char * value,struct request_info * request)436 static void severity_option(char *value, struct request_info *request)
437 {
438 char *level = split_at(value, '.');
439
440 allow_severity = deny_severity = level ?
441 severity_map(facilitynames, value) | severity_map(prioritynames, level)
442 : severity_map(prioritynames, value);
443 }
444
445 /* get_field - return pointer to next field in string */
446
get_field(char * string)447 static char *get_field(char *string)
448 {
449 static char *last = "";
450 char *src;
451 char *dst;
452 char *ret;
453 int ch;
454
455 /*
456 * This function returns pointers to successive fields within a given
457 * string. ":" is the field separator; warn if the rule ends in one. It
458 * replaces a "\:" sequence by ":", without treating the result of
459 * substitution as field terminator. A null argument means resume search
460 * where the previous call terminated. This function destroys its
461 * argument.
462 *
463 * Work from explicit source or from memory. While processing \: we
464 * overwrite the input. This way we do not have to maintain buffers for
465 * copies of input fields.
466 */
467
468 src = dst = ret = (string ? string : last);
469 if (src[0] == 0)
470 return (0);
471
472 while (ch = *src) {
473 if (ch == ':') {
474 if (*++src == 0)
475 tcpd_warn("rule ends in \":\"");
476 break;
477 }
478 if (ch == '\\' && src[1] == ':')
479 src++;
480 *dst++ = *src++;
481 }
482 last = src;
483 *dst = 0;
484 return (ret);
485 }
486
487 /* chop_string - strip leading and trailing blanks from string */
488
chop_string(register char * string)489 static char *chop_string(register char *string)
490 {
491 char *start = 0;
492 char *end;
493 char *cp;
494
495 for (cp = string; *cp; cp++) {
496 if (!isspace(*cp)) {
497 if (start == 0)
498 start = cp;
499 end = cp;
500 }
501 }
502 return (start ? (end[1] = 0, start) : cp);
503 }
504