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 #ifndef INADDR_NONE
50 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */
51 #endif
52
53 /* Local stuff. */
54
55 #include "tcpd.h"
56
57 /* Error handling. */
58
59 extern jmp_buf tcpd_buf;
60
61 /* Delimiters for lists of daemons or clients. */
62
63 static char sep[] = ", \t\r\n";
64
65 /* Constants to be used in assignments only, not in comparisons... */
66
67 #define YES 1
68 #define NO 0
69
70 /*
71 * These variables are globally visible so that they can be redirected in
72 * verification mode.
73 */
74
75 char *hosts_allow_table = HOSTS_ALLOW;
76 char *hosts_deny_table = HOSTS_DENY;
77 int hosts_access_verbose = 0;
78
79 /*
80 * In a long-running process, we are not at liberty to just go away.
81 */
82
83 int resident = (-1); /* -1, 0: unknown; +1: yes */
84
85 /* Forward declarations. */
86
87 static int table_match(char *table, struct request_info *request);
88 static int list_match(char *list, struct request_info *request,
89 int (*match_fn)(char *, struct request_info *));
90 static int server_match(char *tok, struct request_info *request);
91 static int client_match(char *tok, struct request_info *request);
92 static int host_match(char *tok, struct host_info *host);
93 static int string_match(char *tok, char *string);
94 static int masked_match(char *net_tok, char *mask_tok, char *string);
95 #ifdef INET6
96 static int masked_match4(char *net_tok, char *mask_tok, char *string);
97 static int masked_match6(char *net_tok, char *mask_tok, char *string);
98 #endif
99
100 /* Size of logical line buffer. */
101
102 #define BUFLEN 2048
103
104 /* definition to be used from workarounds.c */
105 #ifdef NETGROUP
106 int yp_get_default_domain(char **);
107 #endif
108
109 /* hosts_access - host access control facility */
110
hosts_access(struct request_info * request)111 int hosts_access(struct request_info *request)
112 {
113 int verdict;
114
115 /*
116 * If the (daemon, client) pair is matched by an entry in the file
117 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
118 * client) pair is matched by an entry in the file /etc/hosts.deny,
119 * access is denied. Otherwise, access is granted. A non-existent
120 * access-control file is treated as an empty file.
121 *
122 * After a rule has been matched, the optional language extensions may
123 * decide to grant or refuse service anyway. Or, while a rule is being
124 * processed, a serious error is found, and it seems better to play safe
125 * and deny service. All this is done by jumping back into the
126 * hosts_access() routine, bypassing the regular return from the
127 * table_match() function calls below.
128 */
129
130 if (resident <= 0)
131 resident++;
132 verdict = setjmp(tcpd_buf);
133 if (verdict != 0)
134 return (verdict == AC_PERMIT);
135 if (table_match(hosts_allow_table, request))
136 return (YES);
137 if (table_match(hosts_deny_table, request))
138 return (NO);
139 return (YES);
140 }
141
142 /* table_match - match table entries with (daemon, client) pair */
143
table_match(char * table,struct request_info * request)144 static int table_match(char *table, struct request_info *request)
145 {
146 FILE *fp;
147 char sv_list[BUFLEN]; /* becomes list of daemons */
148 char *cl_list; /* becomes list of clients */
149 char *sh_cmd; /* becomes optional shell command */
150 int match = NO;
151 struct tcpd_context saved_context;
152 char *cp;
153
154 saved_context = tcpd_context; /* stupid compilers */
155
156 /*
157 * Between the fopen() and fclose() calls, avoid jumps that may cause
158 * file descriptor leaks.
159 */
160
161 if ((fp = fopen(table, "r")) != 0) {
162 tcpd_context.file = table;
163 tcpd_context.line = 0;
164 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
165 if (sv_list[strlen(sv_list) - 1] != '\n') {
166 tcpd_warn("missing newline or line too long");
167 continue;
168 }
169 /* Ignore anything after unescaped # character */
170 for (cp = strchr(sv_list, '#'); cp != NULL;) {
171 if (cp > sv_list && cp[-1] == '\\') {
172 cp = strchr(cp + 1, '#');
173 continue;
174 }
175 *cp = '\0';
176 break;
177 }
178 if (sv_list[strspn(sv_list, " \t\r\n")] == 0)
179 continue;
180 if ((cl_list = split_at(sv_list, ':')) == 0) {
181 tcpd_warn("missing \":\" separator");
182 continue;
183 }
184 sh_cmd = split_at(cl_list, ':');
185 match = list_match(sv_list, request, server_match)
186 && list_match(cl_list, request, client_match);
187 }
188 (void) fclose(fp);
189 } else if (errno != ENOENT) {
190 tcpd_warn("cannot open %s: %m", table);
191 }
192 if (match) {
193 if (hosts_access_verbose > 1)
194 syslog(LOG_DEBUG, "matched: %s line %d",
195 tcpd_context.file, tcpd_context.line);
196 if (sh_cmd) {
197 #ifdef PROCESS_OPTIONS
198 process_options(sh_cmd, request);
199 #else
200 char cmd[BUFSIZ];
201 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
202 #endif
203 }
204 }
205 tcpd_context = saved_context;
206 return (match);
207 }
208
209 /* list_match - match a request against a list of patterns with exceptions */
210
list_match(char * list,struct request_info * request,int (* match_fn)(char *,struct request_info *))211 static int list_match(char *list, struct request_info *request,
212 int (*match_fn)(char *, struct request_info *))
213 {
214 char *tok;
215
216 /*
217 * Process tokens one at a time. We have exhausted all possible matches
218 * when we reach an "EXCEPT" token or the end of the list. If we do find
219 * a match, look for an "EXCEPT" list and recurse to determine whether
220 * the match is affected by any exceptions.
221 */
222
223 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
224 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
225 return (NO);
226 if (match_fn(tok, request)) { /* YES: look for exceptions */
227 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
228 /* VOID */ ;
229 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
230 }
231 }
232 return (NO);
233 }
234
235 /* server_match - match server information */
236
server_match(char * tok,struct request_info * request)237 static int server_match(char *tok, struct request_info *request)
238 {
239 char *host;
240
241 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
242 return (string_match(tok, eval_daemon(request)));
243 } else { /* daemon@host */
244 return (string_match(tok, eval_daemon(request))
245 && host_match(host, request->server));
246 }
247 }
248
249 /* client_match - match client information */
250
client_match(char * tok,struct request_info * request)251 static int client_match(char *tok, struct request_info *request)
252 {
253 char *host;
254
255 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
256 return (host_match(tok, request->client));
257 } else { /* user@host */
258 return (host_match(host, request->client)
259 && string_match(tok, eval_user(request)));
260 }
261 }
262
263 /* hostfile_match - look up host patterns from file */
264
hostfile_match(char * path,struct host_info * host)265 static int hostfile_match(char *path, struct host_info *host)
266 {
267 char tok[BUFSIZ];
268 int match = NO;
269 FILE *fp;
270
271 if ((fp = fopen(path, "r")) != 0) {
272 while (fscanf(fp, "%s", tok) == 1 && !(match = host_match(tok, host)))
273 /* void */ ;
274 fclose(fp);
275 } else if (errno != ENOENT) {
276 tcpd_warn("open %s: %m", path);
277 }
278 return (match);
279 }
280
281 /* host_match - match host name and/or address against pattern */
282
host_match(char * tok,struct host_info * host)283 static int host_match(char *tok, struct host_info *host)
284 {
285 char *mask;
286
287 /*
288 * This code looks a little hairy because we want to avoid unnecessary
289 * hostname lookups.
290 *
291 * The KNOWN pattern requires that both address AND name be known; some
292 * patterns are specific to host names or to host addresses; all other
293 * patterns are satisfied when either the address OR the name match.
294 */
295
296 if (tok[0] == '@') { /* netgroup: look it up */
297 #ifdef NETGROUP
298 static char *mydomain = 0;
299 if (mydomain == 0)
300 yp_get_default_domain(&mydomain);
301 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
302 #else
303 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
304 return (NO);
305 #endif
306 } else if (tok[0] == '/') { /* /file hack */
307 return (hostfile_match(tok, host));
308 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
309 char *name = eval_hostname(host);
310 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
311 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
312 char *name = eval_hostname(host);
313 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
314 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
315 return (masked_match(tok, mask, eval_hostaddr(host)));
316 } else { /* anything else */
317 return (string_match(tok, eval_hostaddr(host))
318 || (NOT_INADDR(tok) && NOT_INADDR6(tok)
319 && string_match(tok, eval_hostname(host))));
320 }
321 }
322
323 /* string_match - match string against pattern */
324
string_match(char * tok,char * string)325 static int string_match(char *tok, char *string)
326 {
327 int n;
328
329 #ifdef INET6
330 /* convert IPv4 mapped IPv6 address to IPv4 address */
331 if (STRN_EQ(string, "::ffff:", 7)
332 && dot_quad_addr(string + 7) != INADDR_NONE) {
333 string += 7;
334 }
335 #endif
336 if (tok[0] == '.') { /* suffix */
337 n = strlen(string) - strlen(tok);
338 return (n > 0 && STR_EQ(tok, string + n));
339 } else if (STR_EQ(tok, "ALL")) { /* all: match any */
340 return (YES);
341 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
342 return (STR_NE(string, unknown));
343 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
344 return (STRN_EQ(tok, string, n));
345 } else { /* exact match */
346 #ifdef INET6
347 struct addrinfo hints, *res;
348 struct sockaddr_in6 pat, addr;
349 int len, ret;
350 char ch;
351
352 len = strlen(tok);
353 if (*tok == '[' && tok[len - 1] == ']') {
354 ch = tok[len - 1];
355 tok[len - 1] = '\0';
356 memset(&hints, 0, sizeof(hints));
357 hints.ai_family = AF_INET6;
358 hints.ai_socktype = SOCK_STREAM;
359 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
360 if ((ret = getaddrinfo(tok + 1, NULL, &hints, &res)) == 0) {
361 memcpy(&pat, res->ai_addr, sizeof(pat));
362 freeaddrinfo(res);
363 }
364 tok[len - 1] = ch;
365 if (ret != 0 || getaddrinfo(string, NULL, &hints, &res) != 0)
366 return NO;
367 memcpy(&addr, res->ai_addr, sizeof(addr));
368 freeaddrinfo(res);
369 if (pat.sin6_scope_id != 0 &&
370 addr.sin6_scope_id != pat.sin6_scope_id)
371 return NO;
372 return (!memcmp(&pat.sin6_addr, &addr.sin6_addr,
373 sizeof(struct in6_addr)));
374 return (ret);
375 }
376 #endif
377 return (STR_EQ(tok, string));
378 }
379 }
380
381 /* masked_match - match address against netnumber/netmask */
382
383 #ifdef INET6
masked_match(char * net_tok,char * mask_tok,char * string)384 static int masked_match(char *net_tok, char *mask_tok, char *string)
385 {
386 return (masked_match4(net_tok, mask_tok, string) ||
387 masked_match6(net_tok, mask_tok, string));
388 }
389
masked_match4(char * net_tok,char * mask_tok,char * string)390 static int masked_match4(char *net_tok, char *mask_tok, char *string)
391 #else
392 static int masked_match(char *net_tok, char *mask_tok, char *string)
393 #endif
394 {
395 #ifdef INET6
396 u_int32_t net;
397 u_int32_t mask;
398 u_int32_t addr;
399 #else
400 unsigned long net;
401 unsigned long mask;
402 unsigned long addr;
403 #endif
404
405 /*
406 * Disallow forms other than dotted quad: the treatment that inet_addr()
407 * gives to forms with less than four components is inconsistent with the
408 * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
409 */
410
411 if ((addr = dot_quad_addr(string)) == INADDR_NONE)
412 return (NO);
413 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
414 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
415 #ifndef INET6
416 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
417 #endif
418 return (NO); /* not tcpd_jump() */
419 }
420 return ((addr & mask) == net);
421 }
422
423 #ifdef INET6
masked_match6(char * net_tok,char * mask_tok,char * string)424 static int masked_match6(char *net_tok, char *mask_tok, char *string)
425 {
426 struct addrinfo hints, *res;
427 struct sockaddr_in6 net, addr;
428 u_int32_t mask;
429 int len, mask_len, i = 0;
430 char ch;
431
432 memset(&hints, 0, sizeof(hints));
433 hints.ai_family = AF_INET6;
434 hints.ai_socktype = SOCK_STREAM;
435 hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;
436 if (getaddrinfo(string, NULL, &hints, &res) != 0)
437 return NO;
438 memcpy(&addr, res->ai_addr, sizeof(addr));
439 freeaddrinfo(res);
440
441 if (IN6_IS_ADDR_V4MAPPED(&addr.sin6_addr)) {
442 if ((*(u_int32_t *)&net.sin6_addr.s6_addr[12] = dot_quad_addr(net_tok)) == INADDR_NONE
443 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE)
444 return (NO);
445 return ((*(u_int32_t *)&addr.sin6_addr.s6_addr[12] & mask) == *(u_int32_t *)&net.sin6_addr.s6_addr[12]);
446 }
447
448 /* match IPv6 address against netnumber/prefixlen */
449 len = strlen(net_tok);
450 if (*net_tok != '[' || net_tok[len - 1] != ']')
451 return NO;
452 ch = net_tok[len - 1];
453 net_tok[len - 1] = '\0';
454 if (getaddrinfo(net_tok + 1, NULL, &hints, &res) != 0) {
455 net_tok[len - 1] = ch;
456 return NO;
457 }
458 memcpy(&net, res->ai_addr, sizeof(net));
459 freeaddrinfo(res);
460 net_tok[len - 1] = ch;
461 if ((mask_len = atoi(mask_tok)) < 0 || mask_len > 128)
462 return NO;
463
464 if (net.sin6_scope_id != 0 && addr.sin6_scope_id != net.sin6_scope_id)
465 return NO;
466 while (mask_len > 0) {
467 if (mask_len < 32) {
468 mask = htonl(~(0xffffffff >> mask_len));
469 if ((*(u_int32_t *)&addr.sin6_addr.s6_addr[i] & mask) != (*(u_int32_t *)&net.sin6_addr.s6_addr[i] & mask))
470 return NO;
471 break;
472 }
473 if (*(u_int32_t *)&addr.sin6_addr.s6_addr[i] != *(u_int32_t *)&net.sin6_addr.s6_addr[i])
474 return NO;
475 i += 4;
476 mask_len -= 32;
477 }
478 return YES;
479 }
480 #endif /* INET6 */
481