1 /* $NetBSD: hosts_access.c,v 1.24 2021/03/18 01:49:09 christos Exp $ */
2
3 /*
4 * This module implements a simple access control language that is based on
5 * host (or domain) names, NIS (host) netgroup names, IP addresses (or
6 * network numbers) and daemon process names. When a match is found the
7 * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
8 * a list of options is executed or an optional shell command is executed.
9 *
10 * Host and user names are looked up on demand, provided that suitable endpoint
11 * information is available as sockaddr_in structures or TLI netbufs. As a
12 * side effect, the pattern matching process may change the contents of
13 * request structure fields.
14 *
15 * Diagnostics are reported through syslog(3).
16 *
17 * Compile with -DNETGROUP if your library provides support for netgroups.
18 *
19 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
20 */
21
22 #include <sys/cdefs.h>
23 #ifndef lint
24 #if 0
25 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
26 #else
27 __RCSID("$NetBSD: hosts_access.c,v 1.24 2021/03/18 01:49:09 christos Exp $");
28 #endif
29 #endif
30
31 /* System libraries. */
32
33 #include <sys/types.h>
34 #include <sys/param.h>
35 #ifdef INET6
36 #include <sys/socket.h>
37 #endif
38 #include <netinet/in.h>
39 #include <arpa/inet.h>
40 #include <blocklist.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <syslog.h>
44 #include <ctype.h>
45 #include <errno.h>
46 #include <setjmp.h>
47 #include <string.h>
48 #include <netdb.h>
49 #ifdef NETGROUP
50 #include <netgroup.h>
51 #include <rpcsvc/ypclnt.h>
52 #endif
53
54 /* Local stuff. */
55
56 #include "tcpd.h"
57
58 /* Error handling. */
59
60 extern jmp_buf tcpd_buf;
61
62 /* Delimiters for lists of daemons or clients. */
63
64 static char sep[] = ", \t\r\n";
65
66 /* Constants to be used in assignments only, not in comparisons... */
67
68 #define YES 1
69 #define NO 0
70
71 /*
72 * These variables are globally visible so that they can be redirected in
73 * verification mode.
74 */
75
76 const char *hosts_allow_table = HOSTS_ALLOW;
77 const char *hosts_deny_table = HOSTS_DENY;
78 int hosts_access_verbose = 0;
79
80 /*
81 * In a long-running process, we are not at liberty to just go away.
82 */
83
84 int resident = (-1); /* -1, 0: unknown; +1: yes */
85
86 /* Forward declarations. */
87
88 static int table_match(const char *, struct request_info *);
89 static int list_match(char *, struct request_info *,
90 int (*)(char *, struct request_info *));
91 static int server_match(char *, struct request_info *);
92 static int client_match(char *, struct request_info *);
93 static int host_match(char *, struct host_info *);
94 static int hostfile_match(char *, struct host_info *);
95 static int rbl_match(char *, char *);
96 static int string_match(char *, char *);
97 static int masked_match(char *, char *, char *);
98 static int masked_match4(char *, char *, char *);
99 #ifdef INET6
100 static int masked_match6(char *, char *, char *);
101 #endif
102
103 /* Size of logical line buffer. */
104
105 #define BUFLEN 2048
106
107 static void
pfilter_notify(struct request_info * request,int b)108 pfilter_notify(struct request_info *request, int b)
109 {
110 static struct blocklist *blstate;
111 int fd = request->fd != -1 ? request->fd : 3;
112
113 if (blstate == NULL) {
114 blstate = blocklist_open();
115 }
116 if (request->client->sin != NULL) {
117 blocklist_sa_r(blstate, b, fd, request->client->sin,
118 request->client->sin->sa_len, request->daemon);
119 } else {
120 blocklist_r(blstate, b, fd, request->daemon);
121 }
122 }
123
124 /* hosts_access - host access control facility */
125
126 int
hosts_access(struct request_info * request)127 hosts_access(struct request_info *request)
128 {
129 int verdict;
130
131 /*
132 * If the (daemon, client) pair is matched by an entry in the file
133 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
134 * client) pair is matched by an entry in the file /etc/hosts.deny,
135 * access is denied. Otherwise, access is granted. A non-existent
136 * access-control file is treated as an empty file.
137 *
138 * After a rule has been matched, the optional language extensions may
139 * decide to grant or refuse service anyway. Or, while a rule is being
140 * processed, a serious error is found, and it seems better to play safe
141 * and deny service. All this is done by jumping back into the
142 * hosts_access() routine, bypassing the regular return from the
143 * table_match() function calls below.
144 */
145
146 if (resident <= 0)
147 resident++;
148 verdict = setjmp(tcpd_buf);
149 if (verdict != 0) {
150 if (verdict != AC_PERMIT)
151 pfilter_notify(request, BLOCKLIST_AUTH_FAIL);
152 /* XXX pfilter_notify(0)??? */
153 return (verdict == AC_PERMIT);
154 }
155 if (table_match(hosts_allow_table, request)) {
156 /* XXX pfilter_notify(0)??? */
157 return (YES);
158 }
159 if (table_match(hosts_deny_table, request)) {
160 pfilter_notify(request, BLOCKLIST_AUTH_FAIL);
161 return (NO);
162 }
163 /* XXX pfilter_notify(0)??? */
164 return (YES);
165 }
166
167 /* table_match - match table entries with (daemon, client) pair */
168
169 static int
table_match(const char * table,struct request_info * request)170 table_match(const char *table, struct request_info *request)
171 {
172 FILE *fp;
173 char sv_list[BUFLEN]; /* becomes list of daemons */
174 char *cl_list; /* becomes list of clients */
175 char *sh_cmd = NULL; /* becomes optional shell command */
176 int match = NO;
177 struct tcpd_context saved_context;
178
179 saved_context = tcpd_context; /* stupid compilers */
180
181 /*
182 * Between the fopen() and fclose() calls, avoid jumps that may cause
183 * file descriptor leaks.
184 */
185
186 if ((fp = fopen(table, "r")) != 0) {
187 tcpd_context.file = table;
188 tcpd_context.line = 0;
189 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
190 if (sv_list[strlen(sv_list) - 1] != '\n') {
191 tcpd_warn("missing newline or line too long");
192 continue;
193 }
194 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
195 continue;
196 if ((cl_list = split_at(sv_list, ':')) == 0) {
197 tcpd_warn("missing \":\" separator");
198 continue;
199 }
200 sh_cmd = split_at(cl_list, ':');
201 match = list_match(sv_list, request, server_match)
202 && list_match(cl_list, request, client_match);
203 }
204 (void) fclose(fp);
205 } else if (errno != ENOENT) {
206 tcpd_warn("cannot open %s: %m", table);
207 }
208 if (match) {
209 if (hosts_access_verbose > 1)
210 syslog(LOG_DEBUG, "matched: %s line %d",
211 tcpd_context.file, tcpd_context.line);
212 if (sh_cmd) {
213 #ifdef PROCESS_OPTIONS
214 process_options(sh_cmd, request);
215 #else
216 char cmd[BUFSIZ];
217 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
218 #endif
219 }
220 }
221 tcpd_context = saved_context;
222 return (match);
223 }
224
225 /* list_match - match a request against a list of patterns with exceptions */
226
227 static int
list_match(char * list,struct request_info * request,int (* match_fn)(char *,struct request_info *))228 list_match(char *list, struct request_info *request,
229 int (*match_fn)(char *, struct request_info *))
230 {
231 char *tok;
232 static char *last;
233 int l;
234
235 /*
236 * Process tokens one at a time. We have exhausted all possible matches
237 * when we reach an "EXCEPT" token or the end of the list. If we do find
238 * a match, look for an "EXCEPT" list and recurse to determine whether
239 * the match is affected by any exceptions.
240 */
241
242 for (tok = strtok_r(list, sep, &last); tok != 0;
243 tok = strtok_r(NULL, sep, &last)) {
244 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
245 return (NO);
246 l = strlen(tok);
247 if (*tok == '[' && tok[l - 1] == ']') {
248 tok[l - 1] = '\0';
249 tok++;
250 }
251 if (match_fn(tok, request)) { /* YES: look for exceptions */
252 while ((tok = strtok_r(NULL, sep, &last)) && STR_NE(tok, "EXCEPT"))
253 /* VOID */ ;
254 return (tok == 0 || list_match(NULL, request, match_fn) == 0);
255 }
256 }
257 return (NO);
258 }
259
260 /* server_match - match server information */
261
262 static int
server_match(char * tok,struct request_info * request)263 server_match(char *tok, struct request_info *request)
264 {
265 char *host;
266
267 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
268 return (string_match(tok, eval_daemon(request)));
269 } else { /* daemon@host */
270 return (string_match(tok, eval_daemon(request))
271 && host_match(host, request->server));
272 }
273 }
274
275 /* client_match - match client information */
276
277 static int
client_match(char * tok,struct request_info * request)278 client_match(char *tok, struct request_info *request)
279 {
280 char *host;
281
282 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
283 return (host_match(tok, request->client));
284 } else { /* user@host */
285 return (host_match(host, request->client)
286 && string_match(tok, eval_user(request)));
287 }
288 }
289
290 /* host_match - match host name and/or address against pattern */
291
292 static int
host_match(char * tok,struct host_info * host)293 host_match(char *tok, struct host_info *host)
294 {
295 char *mask;
296
297 /*
298 * This code looks a little hairy because we want to avoid unnecessary
299 * hostname lookups.
300 *
301 * The KNOWN pattern requires that both address AND name be known; some
302 * patterns are specific to host names or to host addresses; all other
303 * patterns are satisfied when either the address OR the name match.
304 */
305
306 if (tok[0] == '@') { /* netgroup: look it up */
307 #ifdef NETGROUP
308 static char *mydomain = 0;
309 if (mydomain == 0)
310 yp_get_default_domain(&mydomain);
311 return (innetgr(tok + 1, eval_hostname(host), NULL, mydomain));
312 #else
313 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
314 return (NO);
315 #endif
316 } else if (tok[0] == '/') { /* /file hack */
317 return (hostfile_match(tok, host));
318 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
319 char *name = eval_hostname(host);
320 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
321 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
322 char *name = eval_hostname(host);
323 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
324 } else if (strncmp(tok, "{RBL}.", 6) == 0) { /* RBL lookup in domain */
325 return rbl_match(tok+6, eval_hostaddr(host));
326 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
327 return (masked_match(tok, mask, eval_hostaddr(host)));
328 } else { /* anything else */
329 return (string_match(tok, eval_hostaddr(host))
330 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
331 }
332 }
333
334 /* hostfile_match - look up host patterns from file */
335
336 static int
hostfile_match(char * path,struct host_info * host)337 hostfile_match(char *path, struct host_info *host)
338 {
339 char tok[512];
340 int match = NO;
341 FILE *fp;
342
343 if ((fp = fopen(path, "r")) != 0) {
344 while (fscanf(fp, "%511s", tok) == 1 && !(match = host_match(tok, host)))
345 /* void */ ;
346 fclose(fp);
347 } else if (errno != ENOENT) {
348 tcpd_warn("open %s: %m", path);
349 }
350 return (match);
351 }
352
353 /* rbl_match() - match host by looking up in RBL domain */
354
355 static int
rbl_match(char * rbl_domain,char * rbl_hostaddr)356 rbl_match(
357 char *rbl_domain, /* RBL domain */
358 char *rbl_hostaddr) /* hostaddr */
359 {
360 char *rbl_name;
361 unsigned long host_address;
362 int ret = NO;
363 size_t len = strlen(rbl_domain) + (4 * 4) + 2;
364
365 if (dot_quad_addr(rbl_hostaddr, &host_address) != 0) {
366 tcpd_warn("unable to convert %s to address", rbl_hostaddr);
367 return (NO);
368 }
369 host_address = ntohl(host_address);
370 /* construct the rbl name to look up */
371 if ((rbl_name = malloc(len)) == NULL) {
372 tcpd_jump("not enough memory to build RBL name for %s in %s", rbl_hostaddr, rbl_domain);
373 /* NOTREACHED */
374 }
375 snprintf(rbl_name, len, "%u.%u.%u.%u.%s",
376 (unsigned int) ((host_address) & 0xff),
377 (unsigned int) ((host_address >> 8) & 0xff),
378 (unsigned int) ((host_address >> 16) & 0xff),
379 (unsigned int) ((host_address >> 24) & 0xff),
380 rbl_domain);
381 /* look it up */
382 if (gethostbyname(rbl_name) != NULL) {
383 /* successful lookup - they're on the RBL list */
384 ret = YES;
385 }
386 free(rbl_name);
387
388 return ret;
389 }
390
391 /* string_match - match string against pattern */
392
393 static int
string_match(char * tok,char * string)394 string_match(char *tok, char *string)
395 {
396 int n;
397
398 if (tok[0] == '.') { /* suffix */
399 n = strlen(string) - strlen(tok);
400 return (n > 0 && STR_EQ(tok, string + n));
401 } else if (STR_EQ(tok, "ALL")) { /* all: match any */
402 return (YES);
403 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
404 return (STR_NE(string, unknown));
405 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
406 return (STRN_EQ(tok, string, n));
407 } else { /* exact match */
408 return (STR_EQ(tok, string));
409 }
410 }
411
412 /* masked_match - match address against netnumber/netmask */
413
414 static int
masked_match(char * net_tok,char * mask_tok,char * string)415 masked_match(char *net_tok, char *mask_tok, char *string)
416 {
417 #ifndef INET6
418 return masked_match4(net_tok, mask_tok, string);
419 #else
420 /*
421 * masked_match4() is kept just for supporting shortened IPv4 address form.
422 * If we could get rid of shortened IPv4 form, we could just always use
423 * masked_match6().
424 */
425 if (dot_quad_addr(net_tok, NULL) != -1 &&
426 dot_quad_addr(mask_tok, NULL) != -1 &&
427 dot_quad_addr(string, NULL) != -1) {
428 return masked_match4(net_tok, mask_tok, string);
429 } else
430 return masked_match6(net_tok, mask_tok, string);
431 #endif
432 }
433
434 static int
masked_match4(char * net_tok,char * mask_tok,char * string)435 masked_match4(char *net_tok, char *mask_tok, char *string)
436 {
437 unsigned long net;
438 unsigned long mask;
439 unsigned long addr;
440
441 /*
442 * Disallow forms other than dotted quad: the treatment that inet_addr()
443 * gives to forms with less than four components is inconsistent with the
444 * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
445 */
446
447 if (dot_quad_addr(string, &addr) != 0)
448 return (NO);
449 if (dot_quad_addr(net_tok, &net) != 0 ||
450 dot_quad_addr(mask_tok, &mask) != 0) {
451 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
452 return (NO); /* not tcpd_jump() */
453 }
454
455 if ((net & ~mask) != 0)
456 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
457
458 return ((addr & mask) == net);
459 }
460
461 #ifdef INET6
462 static int
masked_match6(char * net_tok,char * mask_tok,char * string)463 masked_match6(char *net_tok, char *mask_tok, char *string)
464 {
465 union {
466 struct sockaddr sa;
467 struct sockaddr_in sin;
468 struct sockaddr_in6 sin6;
469 } net, mask, addr;
470 struct addrinfo hints, *res;
471 unsigned long masklen;
472 char *ep;
473 size_t i;
474 char *np, *mp, *ap;
475 size_t alen;
476
477 memset(&hints, 0, sizeof(hints));
478 hints.ai_family = PF_UNSPEC;
479 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
480 hints.ai_flags = AI_NUMERICHOST;
481 if (getaddrinfo(net_tok, "0", &hints, &res) == 0) {
482 if (res->ai_addrlen > sizeof(net) || res->ai_next) {
483 freeaddrinfo(res);
484 return NO;
485 }
486 memcpy(&net, res->ai_addr, res->ai_addrlen);
487 freeaddrinfo(res);
488 } else
489 return NO;
490
491 memset(&hints, 0, sizeof(hints));
492 hints.ai_family = net.sa.sa_family;
493 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
494 hints.ai_flags = AI_NUMERICHOST;
495 ep = NULL;
496 if (getaddrinfo(mask_tok, "0", &hints, &res) == 0) {
497 if (res->ai_family == AF_INET6 &&
498 ((struct sockaddr_in6 *)res->ai_addr)->sin6_scope_id) {
499 freeaddrinfo(res);
500 return NO;
501 }
502 if (res->ai_addrlen > sizeof(mask) || res->ai_next) {
503 freeaddrinfo(res);
504 return NO;
505 }
506 memcpy(&mask, res->ai_addr, res->ai_addrlen);
507 freeaddrinfo(res);
508 } else {
509 ep = NULL;
510 masklen = strtoul(mask_tok, &ep, 10);
511 if (ep && !*ep) {
512 memset(&mask, 0, sizeof(mask));
513 mask.sa.sa_family = net.sa.sa_family;
514 mask.sa.sa_len = net.sa.sa_len;
515 switch (mask.sa.sa_family) {
516 case AF_INET:
517 mp = (char *)&mask.sin.sin_addr;
518 alen = sizeof(mask.sin.sin_addr);
519 break;
520 case AF_INET6:
521 mp = (char *)&mask.sin6.sin6_addr;
522 alen = sizeof(mask.sin6.sin6_addr);
523 break;
524 default:
525 return NO;
526 }
527 if (masklen / 8 > alen)
528 return NO;
529 memset(mp, 0xff, masklen / 8);
530 if (masklen % 8)
531 mp[masklen / 8] = 0xff00 >> (masklen % 8);
532 } else
533 return NO;
534 }
535
536 memset(&hints, 0, sizeof(hints));
537 hints.ai_family = PF_UNSPEC;
538 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
539 hints.ai_flags = AI_NUMERICHOST;
540 if (getaddrinfo(string, "0", &hints, &res) == 0) {
541 if (res->ai_addrlen > sizeof(addr) || res->ai_next) {
542 freeaddrinfo(res);
543 return NO;
544 }
545 /* special case - IPv4 mapped address */
546 if (net.sa.sa_family == AF_INET && res->ai_family == AF_INET6 &&
547 IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)res->ai_addr)->sin6_addr)) {
548 memset(&addr, 0, sizeof(addr));
549 addr.sa.sa_family = net.sa.sa_family;
550 addr.sa.sa_len = net.sa.sa_len;
551 memcpy(&addr.sin.sin_addr,
552 &((struct sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr[12],
553 sizeof(addr.sin.sin_addr));
554 } else
555 memcpy(&addr, res->ai_addr, res->ai_addrlen);
556 freeaddrinfo(res);
557 } else
558 return NO;
559
560 if (net.sa.sa_family != mask.sa.sa_family ||
561 net.sa.sa_family != addr.sa.sa_family) {
562 return NO;
563 }
564
565 switch (net.sa.sa_family) {
566 case AF_INET:
567 np = (char *)&net.sin.sin_addr;
568 mp = (char *)&mask.sin.sin_addr;
569 ap = (char *)&addr.sin.sin_addr;
570 alen = sizeof(net.sin.sin_addr);
571 break;
572 case AF_INET6:
573 np = (char *)&net.sin6.sin6_addr;
574 mp = (char *)&mask.sin6.sin6_addr;
575 ap = (char *)&addr.sin6.sin6_addr;
576 alen = sizeof(net.sin6.sin6_addr);
577 break;
578 default:
579 return NO;
580 }
581
582 for (i = 0; i < alen; i++)
583 if (np[i] & ~mp[i]) {
584 tcpd_warn("host bits not all zero in %s/%s", net_tok, mask_tok);
585 break;
586 }
587
588 for (i = 0; i < alen; i++)
589 ap[i] &= mp[i];
590
591 if (addr.sa.sa_family == AF_INET6 && net.sin6.sin6_scope_id &&
592 addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
593 return NO;
594 return (memcmp(ap, np, alen) == 0);
595 }
596 #endif
597