1 /*
2 * This module implements a simple access control language that is based on
3 * host (or domain) names, NIS (host) netgroup names, IP addresses (or
4 * network numbers) and daemon process names. When a match is found the
5 * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
6 * a list of options is executed or an optional shell command is executed.
7 *
8 * Host and user names are looked up on demand, provided that suitable endpoint
9 * information is available as sockaddr_in structures or TLI netbufs. As a
10 * side effect, the pattern matching process may change the contents of
11 * request structure fields.
12 *
13 * Diagnostics are reported through syslog(3).
14 *
15 * Compile with -DNETGROUP if your library provides support for netgroups.
16 *
17 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
18 *
19 * $FreeBSD$
20 */
21
22 #ifndef lint
23 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
24 #endif
25
26 /* System libraries. */
27
28 #include <sys/types.h>
29 #ifdef INT32_T
30 typedef uint32_t u_int32_t;
31 #endif
32 #include <sys/param.h>
33 #ifdef INET6
34 #include <sys/socket.h>
35 #endif
36 #include <netinet/in.h>
37 #include <arpa/inet.h>
38 #include <stdio.h>
39 #include <syslog.h>
40 #include <ctype.h>
41 #include <errno.h>
42 #include <setjmp.h>
43 #include <string.h>
44 #ifdef INET6
45 #include <netdb.h>
46 #endif
47 #include <stdlib.h>
48
49 extern char *fgets();
50 extern int errno;
51
52 #ifndef INADDR_NONE
53 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */
54 #endif
55
56 /* Local stuff. */
57
58 #include "tcpd.h"
59
60 /* Error handling. */
61
62 extern jmp_buf tcpd_buf;
63
64 /* Delimiters for lists of daemons or clients. */
65
66 static char sep[] = ", \t\r\n";
67
68 /* Constants to be used in assignments only, not in comparisons... */
69
70 #define YES 1
71 #define NO 0
72
73 /*
74 * These variables are globally visible so that they can be redirected in
75 * verification mode.
76 */
77
78 char *hosts_allow_table = HOSTS_ALLOW;
79 char *hosts_deny_table = HOSTS_DENY;
80 int hosts_access_verbose = 0;
81
82 /*
83 * In a long-running process, we are not at liberty to just go away.
84 */
85
86 int resident = (-1); /* -1, 0: unknown; +1: yes */
87
88 /* Forward declarations. */
89
90 static int table_match();
91 static int list_match();
92 static int server_match();
93 static int client_match();
94 static int host_match();
95 static int string_match();
96 static int masked_match();
97 #ifdef INET6
98 static int masked_match4();
99 static int masked_match6();
100 #endif
101
102 /* Size of logical line buffer. */
103
104 #define BUFLEN 2048
105
106 /* definition to be used from workarounds.c */
107 #ifdef NETGROUP
108 int yp_get_default_domain(char **);
109 #endif
110
111 /* hosts_access - host access control facility */
112
hosts_access(request)113 int hosts_access(request)
114 struct request_info *request;
115 {
116 int verdict;
117
118 /*
119 * If the (daemon, client) pair is matched by an entry in the file
120 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
121 * client) pair is matched by an entry in the file /etc/hosts.deny,
122 * access is denied. Otherwise, access is granted. A non-existent
123 * access-control file is treated as an empty file.
124 *
125 * After a rule has been matched, the optional language extensions may
126 * decide to grant or refuse service anyway. Or, while a rule is being
127 * processed, a serious error is found, and it seems better to play safe
128 * and deny service. All this is done by jumping back into the
129 * hosts_access() routine, bypassing the regular return from the
130 * table_match() function calls below.
131 */
132
133 if (resident <= 0)
134 resident++;
135 verdict = setjmp(tcpd_buf);
136 if (verdict != 0)
137 return (verdict == AC_PERMIT);
138 if (table_match(hosts_allow_table, request))
139 return (YES);
140 if (table_match(hosts_deny_table, request))
141 return (NO);
142 return (YES);
143 }
144
145 /* table_match - match table entries with (daemon, client) pair */
146
table_match(table,request)147 static int table_match(table, request)
148 char *table;
149 struct request_info *request;
150 {
151 FILE *fp;
152 char sv_list[BUFLEN]; /* becomes list of daemons */
153 char *cl_list; /* becomes list of clients */
154 char *sh_cmd; /* becomes optional shell command */
155 int match = NO;
156 struct tcpd_context saved_context;
157 char *cp;
158
159 saved_context = tcpd_context; /* stupid compilers */
160
161 /*
162 * Between the fopen() and fclose() calls, avoid jumps that may cause
163 * file descriptor leaks.
164 */
165
166 if ((fp = fopen(table, "r")) != 0) {
167 tcpd_context.file = table;
168 tcpd_context.line = 0;
169 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
170 if (sv_list[strlen(sv_list) - 1] != '\n') {
171 tcpd_warn("missing newline or line too long");
172 continue;
173 }
174 /* Ignore anything after unescaped # character */
175 for (cp = strchr(sv_list, '#'); cp != NULL;) {
176 if (cp > sv_list && cp[-1] == '\\') {
177 cp = strchr(cp + 1, '#');
178 continue;
179 }
180 *cp = '\0';
181 break;
182 }
183 if (sv_list[strspn(sv_list, " \t\r\n")] == 0)
184 continue;
185 if ((cl_list = split_at(sv_list, ':')) == 0) {
186 tcpd_warn("missing \":\" separator");
187 continue;
188 }
189 sh_cmd = split_at(cl_list, ':');
190 match = list_match(sv_list, request, server_match)
191 && list_match(cl_list, request, client_match);
192 }
193 (void) fclose(fp);
194 } else if (errno != ENOENT) {
195 tcpd_warn("cannot open %s: %m", table);
196 }
197 if (match) {
198 if (hosts_access_verbose > 1)
199 syslog(LOG_DEBUG, "matched: %s line %d",
200 tcpd_context.file, tcpd_context.line);
201 if (sh_cmd) {
202 #ifdef PROCESS_OPTIONS
203 process_options(sh_cmd, request);
204 #else
205 char cmd[BUFSIZ];
206 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
207 #endif
208 }
209 }
210 tcpd_context = saved_context;
211 return (match);
212 }
213
214 /* list_match - match a request against a list of patterns with exceptions */
215
list_match(list,request,match_fn)216 static int list_match(list, request, match_fn)
217 char *list;
218 struct request_info *request;
219 int (*match_fn) ();
220 {
221 char *tok;
222
223 /*
224 * Process tokens one at a time. We have exhausted all possible matches
225 * when we reach an "EXCEPT" token or the end of the list. If we do find
226 * a match, look for an "EXCEPT" list and recurse to determine whether
227 * the match is affected by any exceptions.
228 */
229
230 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
231 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
232 return (NO);
233 if (match_fn(tok, request)) { /* YES: look for exceptions */
234 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
235 /* VOID */ ;
236 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
237 }
238 }
239 return (NO);
240 }
241
242 /* server_match - match server information */
243
server_match(tok,request)244 static int server_match(tok, request)
245 char *tok;
246 struct request_info *request;
247 {
248 char *host;
249
250 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
251 return (string_match(tok, eval_daemon(request)));
252 } else { /* daemon@host */
253 return (string_match(tok, eval_daemon(request))
254 && host_match(host, request->server));
255 }
256 }
257
258 /* client_match - match client information */
259
client_match(tok,request)260 static int client_match(tok, request)
261 char *tok;
262 struct request_info *request;
263 {
264 char *host;
265
266 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
267 return (host_match(tok, request->client));
268 } else { /* user@host */
269 return (host_match(host, request->client)
270 && string_match(tok, eval_user(request)));
271 }
272 }
273
274 /* hostfile_match - look up host patterns from file */
275
hostfile_match(path,host)276 static int hostfile_match(path, host)
277 char *path;
278 struct host_info *host;
279 {
280 char tok[BUFSIZ];
281 int match = NO;
282 FILE *fp;
283
284 if ((fp = fopen(path, "r")) != 0) {
285 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host)))
286 /* void */ ;
287 fclose(fp);
288 } else if (errno != ENOENT) {
289 tcpd_warn("open %s: %m", path);
290 }
291 return (match);
292 }
293
294 /* host_match - match host name and/or address against pattern */
295
host_match(tok,host)296 static int host_match(tok, host)
297 char *tok;
298 struct host_info *host;
299 {
300 char *mask;
301
302 /*
303 * This code looks a little hairy because we want to avoid unnecessary
304 * hostname lookups.
305 *
306 * The KNOWN pattern requires that both address AND name be known; some
307 * patterns are specific to host names or to host addresses; all other
308 * patterns are satisfied when either the address OR the name match.
309 */
310
311 if (tok[0] == '@') { /* netgroup: look it up */
312 #ifdef NETGROUP
313 static char *mydomain = 0;
314 if (mydomain == 0)
315 yp_get_default_domain(&mydomain);
316 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
317 #else
318 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
319 return (NO);
320 #endif
321 } else if (tok[0] == '/') { /* /file hack */
322 return (hostfile_match(tok, host));
323 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
324 char *name = eval_hostname(host);
325 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
326 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
327 char *name = eval_hostname(host);
328 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
329 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
330 return (masked_match(tok, mask, eval_hostaddr(host)));
331 } else { /* anything else */
332 return (string_match(tok, eval_hostaddr(host))
333 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
334 }
335 }
336
337 /* string_match - match string against pattern */
338
string_match(tok,string)339 static int string_match(tok, string)
340 char *tok;
341 char *string;
342 {
343 int n;
344
345 #ifdef INET6
346 /* convert IPv4 mapped IPv6 address to IPv4 address */
347 if (STRN_EQ(string, "::ffff:", 7)
348 && dot_quad_addr(string + 7) != INADDR_NONE) {
349 string += 7;
350 }
351 #endif
352 if (tok[0] == '.') { /* suffix */
353 n = strlen(string) - strlen(tok);
354 return (n > 0 && STR_EQ(tok, string + n));
355 } else if (STR_EQ(tok, "ALL")) { /* all: match any */
356 return (YES);
357 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
358 return (STR_NE(string, unknown));
359 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
360 return (STRN_EQ(tok, string, n));
361 } else { /* exact match */
362 #ifdef INET6
363 struct addrinfo hints, *res;
364 struct sockaddr_in6 pat, addr;
365 int len, ret;
366 char ch;
367
368 len = strlen(tok);
369 if (*tok == '[' && tok[len - 1] == ']') {
370 ch = tok[len - 1];
371 tok[len - 1] = '\0';
372 memset(&hints, 0, sizeof(hints));
373 hints.ai_family = AF_INET6;
374 hints.ai_socktype = SOCK_STREAM;
375 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
376 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) {
377 memcpy(&pat, res->ai_addr, sizeof(pat));
378 freeaddrinfo(res);
379 }
380 tok[len - 1] = ch;
381 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0)
382 return NO;
383 memcpy(&addr, res->ai_addr, sizeof(addr));
384 freeaddrinfo(res);
385 if (pat.sin6_scope_id != 0 &&
386 addr.sin6_scope_id != pat.sin6_scope_id)
387 return NO;
388 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr,
389 sizeof(struct in6_addr)));
390 return (ret);
391 }
392 #endif
393 return (STR_EQ(tok, string));
394 }
395 }
396
397 /* masked_match - match address against netnumber/netmask */
398
399 #ifdef INET6
masked_match(net_tok,mask_tok,string)400 static int masked_match(net_tok, mask_tok, string)
401 char *net_tok;
402 char *mask_tok;
403 char *string;
404 {
405 return (masked_match4(net_tok, mask_tok, string) ||
406 masked_match6(net_tok, mask_tok, string));
407 }
408
masked_match4(net_tok,mask_tok,string)409 static int masked_match4(net_tok, mask_tok, string)
410 #else
411 static int masked_match(net_tok, mask_tok, string)
412 #endif
413 char *net_tok;
414 char *mask_tok;
415 char *string;
416 {
417 #ifdef INET6
418 u_int32_t net;
419 u_int32_t mask;
420 u_int32_t addr;
421 #else
422 unsigned long net;
423 unsigned long mask;
424 unsigned long addr;
425 #endif
426
427 /*
428 * Disallow forms other than dotted quad: the treatment that inet_addr()
429 * gives to forms with less than four components is inconsistent with the
430 * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
431 */
432
433 if ((addr = dot_quad_addr(string)) == INADDR_NONE)
434 return (NO);
435 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
436 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
437 #ifndef INET6
438 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
439 #endif
440 return (NO); /* not tcpd_jump() */
441 }
442 return ((addr & mask) == net);
443 }
444
445 #ifdef INET6
masked_match6(net_tok,mask_tok,string)446 static int masked_match6(net_tok, mask_tok, string)
447 char *net_tok;
448 char *mask_tok;
449 char *string;
450 {
451 struct addrinfo hints, *res;
452 struct sockaddr_in6 net, addr;
453 u_int32_t mask;
454 int len, mask_len, i = 0;
455 char ch;
456
457 memset(&hints, 0, sizeof(hints));
458 hints.ai_family = AF_INET6;
459 hints.ai_socktype = SOCK_STREAM;
460 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
461 if (getaddrinfo(string, NULL, &hints, &res) != 0)
462 return NO;
463 memcpy(&addr, res->ai_addr, sizeof(addr));
464 freeaddrinfo(res);
465
466 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) {
467 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE
468 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE)
469 return (NO);
470 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]);
471 }
472
473 /* match IPv6 address against netnumber/prefixlen */
474 len = strlen(net_tok);
475 if (*net_tok != '[' || net_tok[len - 1] != ']')
476 return NO;
477 ch = net_tok[len - 1];
478 net_tok[len - 1] = '\0';
479 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) {
480 net_tok[len - 1] = ch;
481 return NO;
482 }
483 memcpy(&net, res->ai_addr, sizeof(net));
484 freeaddrinfo(res);
485 net_tok[len - 1] = ch;
486 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128)
487 return NO;
488
489 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id)
490 return NO;
491 while (mask_len > 0) {
492 if (mask_len < 32) {
493 mask = htonl(~(0xffffffff >> mask_len));
494 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask))
495 return NO;
496 break;
497 }
498 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i])
499 return NO;
500 i += 4;
501 mask_len -= 32;
502 }
503 return YES;
504 }
505 #endif /* INET6 */
506