1 /*
2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 /*
7 * This module implements a simple access control language that is based on
8 * host (or domain) names, NIS (host) netgroup names, IP addresses (or
9 * network numbers) and daemon process names. When a match is found the
10 * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
11 * a list of options is executed or an optional shell command is executed.
12 *
13 * Host and user names are looked up on demand, provided that suitable endpoint
14 * information is available as sockaddr_in structures or TLI netbufs. As a
15 * side effect, the pattern matching process may change the contents of
16 * request structure fields.
17 *
18 * Diagnostics are reported through syslog(3).
19 *
20 * Compile with -DNETGROUP if your library provides support for netgroups.
21 *
22 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
23 */
24
25 #ifndef lint
26 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
27 #endif
28
29 /* System libraries. */
30
31 #include <sys/types.h>
32 #include <sys/param.h>
33 #include <netinet/in.h>
34 #include <arpa/inet.h>
35 #include <rpcsvc/ypclnt.h>
36 #include <netdb.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <unistd.h>
40 #include <syslog.h>
41 #include <ctype.h>
42 #include <errno.h>
43 #include <setjmp.h>
44 #include <string.h>
45
46 extern char *fgets();
47 extern int errno;
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();
88 static int list_match();
89 static int server_match();
90 static int client_match();
91 static int host_match();
92 static int string_match();
93 static int masked_match();
94 #ifdef HAVE_IPV6
95 static void ipv6_mask();
96 #endif
97
98 /* Size of logical line buffer. */
99
100 #define BUFLEN 2048
101
102 /* hosts_access - host access control facility */
103
hosts_access(request)104 int hosts_access(request)
105 struct request_info *request;
106 {
107 int verdict;
108
109 /*
110 * If the (daemon, client) pair is matched by an entry in the file
111 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
112 * client) pair is matched by an entry in the file /etc/hosts.deny,
113 * access is denied. Otherwise, access is granted. A non-existent
114 * access-control file is treated as an empty file.
115 *
116 * After a rule has been matched, the optional language extensions may
117 * decide to grant or refuse service anyway. Or, while a rule is being
118 * processed, a serious error is found, and it seems better to play safe
119 * and deny service. All this is done by jumping back into the
120 * hosts_access() routine, bypassing the regular return from the
121 * table_match() function calls below.
122 */
123
124 if (resident <= 0)
125 resident++;
126 verdict = setjmp(tcpd_buf);
127 if (verdict != 0)
128 return (verdict == AC_PERMIT);
129 if (table_match(hosts_allow_table, request))
130 return (YES);
131 if (table_match(hosts_deny_table, request))
132 return (NO);
133 return (YES);
134 }
135
136 /* table_match - match table entries with (daemon, client) pair */
137
table_match(table,request)138 static int table_match(table, request)
139 char *table;
140 struct request_info *request;
141 {
142 FILE *fp;
143 char sv_list[BUFLEN]; /* becomes list of daemons */
144 char *cl_list; /* becomes list of clients */
145 char *sh_cmd; /* becomes optional shell command */
146 int match = NO;
147 struct tcpd_context saved_context;
148
149 saved_context = tcpd_context; /* stupid compilers */
150
151 /*
152 * Between the fopen() and fclose() calls, avoid jumps that may cause
153 * file descriptor leaks.
154 */
155
156 if ((fp = fopen(table, "r")) != 0) {
157 tcpd_context.file = table;
158 tcpd_context.line = 0;
159 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
160 if (sv_list[strlen(sv_list) - 1] != '\n') {
161 tcpd_warn("missing newline or line too long");
162 continue;
163 }
164 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
165 continue;
166 if ((cl_list = split_at(skip_ipv6_addrs(sv_list), ':')) == 0) {
167 tcpd_warn("missing \":\" separator");
168 continue;
169 }
170 sh_cmd = split_at(skip_ipv6_addrs(cl_list), ':');
171 match = list_match(sv_list, request, server_match)
172 && list_match(cl_list, request, client_match);
173 }
174 (void) fclose(fp);
175 } else if (errno != ENOENT) {
176 tcpd_warn("cannot open %s: %m", table);
177 }
178 if (match) {
179 if (hosts_access_verbose > 1)
180 syslog(LOG_DEBUG, "matched: %s line %d",
181 tcpd_context.file, tcpd_context.line);
182 if (sh_cmd) {
183 #ifdef PROCESS_OPTIONS
184 process_options(sh_cmd, request);
185 #else
186 char cmd[BUFSIZ];
187 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
188 #endif
189 }
190 }
191 tcpd_context = saved_context;
192 return (match);
193 }
194
195 /* list_match - match a request against a list of patterns with exceptions */
196
list_match(list,request,match_fn)197 static int list_match(list, request, match_fn)
198 char *list;
199 struct request_info *request;
200 int (*match_fn) ();
201 {
202 char *tok;
203
204 /*
205 * Process tokens one at a time. We have exhausted all possible matches
206 * when we reach an "EXCEPT" token or the end of the list. If we do find
207 * a match, look for an "EXCEPT" list and recurse to determine whether
208 * the match is affected by any exceptions.
209 */
210
211 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
212 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
213 return (NO);
214 if (match_fn(tok, request)) { /* YES: look for exceptions */
215 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
216 /* VOID */ ;
217 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
218 }
219 }
220 return (NO);
221 }
222
223 /* server_match - match server information */
224
server_match(tok,request)225 static int server_match(tok, request)
226 char *tok;
227 struct request_info *request;
228 {
229 char *host;
230
231 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
232 return (string_match(tok, eval_daemon(request)));
233 } else { /* daemon@host */
234 return (string_match(tok, eval_daemon(request))
235 && host_match(host, request->server));
236 }
237 }
238
239 /* client_match - match client information */
240
client_match(tok,request)241 static int client_match(tok, request)
242 char *tok;
243 struct request_info *request;
244 {
245 char *host;
246
247 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
248 return (host_match(tok, request->client));
249 } else { /* user@host */
250 return (host_match(host, request->client)
251 && string_match(tok, eval_user(request)));
252 }
253 }
254
255 /* host_match - match host name and/or address against pattern */
256
host_match(tok,host)257 static int host_match(tok, host)
258 char *tok;
259 struct host_info *host;
260 {
261 char *mask;
262
263 /*
264 * This code looks a little hairy because we want to avoid unnecessary
265 * hostname lookups.
266 *
267 * The KNOWN pattern requires that both address AND name be known; some
268 * patterns are specific to host names or to host addresses; all other
269 * patterns are satisfied when either the address OR the name match.
270 */
271
272 if (tok[0] == '@') { /* netgroup: look it up */
273 #ifdef NETGROUP
274 static char *mydomain = 0;
275 if (mydomain == 0)
276 yp_get_default_domain(&mydomain);
277 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
278 #else
279 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
280 return (NO);
281 #endif
282 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
283 char *name = eval_hostname(host);
284 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
285 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
286 char *name = eval_hostname(host);
287 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
288 #ifdef HAVE_IPV6
289 } else if (tok[0] == '[') { /* IPv6 address */
290 struct in6_addr in6, hostin6, *hip;
291 char *cbr;
292 char *slash;
293 int mask = IPV6_ABITS;
294
295 /*
296 * In some cases we don't get the sockaddr, only the addr.
297 * We use inet_pton to convert it to its binary representation
298 * and match against that.
299 */
300 if (host->sin == NULL) {
301 if (inet_pton(AF_INET6, host->addr, &hostin6) != 1) {
302 return (NO);
303 }
304 hip = &hostin6;
305 } else {
306 if (SGFAM(host->sin) != AF_INET6)
307 return (NO);
308 hip = &host->sin->sg_sin6.sin6_addr;
309 }
310
311 if (cbr = strchr(tok, ']'))
312 *cbr = '\0';
313
314 /*
315 * A /nnn prefix specifies how many bits of the address we
316 * need to check.
317 */
318 if (slash = strchr(tok, '/')) {
319 *slash = '\0';
320 mask = atoi(slash+1);
321 if (mask < 0 || mask > IPV6_ABITS) {
322 tcpd_warn("bad IP6 prefix specification");
323 return (NO);
324 }
325 /* Copy, because we need to modify it below */
326 if (host->sin != NULL) {
327 hostin6 = host->sin->sg_sin6.sin6_addr;
328 hip = &hostin6;
329 }
330 }
331
332 if (cbr == NULL || inet_pton(AF_INET6, tok+1, &in6) != 1) {
333 tcpd_warn("bad IP6 address specification");
334 return (NO);
335 }
336 /*
337 * Zero the bits we're not interested in in both addresses
338 * then compare. Note that we take a copy of the host info
339 * in that case.
340 */
341 if (mask != IPV6_ABITS) {
342 ipv6_mask(&in6, mask);
343 ipv6_mask(hip, mask);
344 }
345 if (memcmp(&in6, hip, sizeof(in6)) == 0)
346 return (YES);
347 return (NO);
348 #endif
349 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
350 return (masked_match(tok, mask, eval_hostaddr(host)));
351 } else { /* anything else */
352 return (string_match(tok, eval_hostaddr(host))
353 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
354 }
355 }
356
357 /* string_match - match string against pattern */
358
string_match(tok,string)359 static int string_match(tok, string)
360 char *tok;
361 char *string;
362 {
363 int n;
364
365 if (tok[0] == '.') { /* suffix */
366 n = strlen(string) - strlen(tok);
367 return (n > 0 && STR_EQ(tok, string + n));
368 } else if (STR_EQ(tok, "ALL")) { /* all: match any */
369 return (YES);
370 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
371 return (STR_NE(string, unknown));
372 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
373 return (STRN_EQ(tok, string, n));
374 } else { /* exact match */
375 return (STR_EQ(tok, string));
376 }
377 }
378
379 /* masked_match - match address against netnumber/netmask */
380
masked_match(net_tok,mask_tok,string)381 static int masked_match(net_tok, mask_tok, string)
382 char *net_tok;
383 char *mask_tok;
384 char *string;
385 {
386 unsigned long net;
387 unsigned long mask;
388 unsigned long addr;
389
390 /*
391 * Disallow forms other than dotted quad: the treatment that inet_addr()
392 * gives to forms with less than four components is inconsistent with the
393 * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
394 */
395
396 if ((addr = dot_quad_addr(string)) == INADDR_NONE)
397 return (NO);
398 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
399 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
400 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
401 return (NO); /* not tcpd_jump() */
402 }
403 return ((addr & mask) == net);
404 }
405
406 #ifdef HAVE_IPV6
407 /*
408 * Function that zeros all but the first "maskbits" bits of the IPV6 address
409 * This function can be made generic by specifying an address length as
410 * extra parameter. (So Wietse can implement 1.2.3.4/16)
411 */
ipv6_mask(in6p,maskbits)412 static void ipv6_mask(in6p, maskbits)
413 struct in6_addr *in6p;
414 int maskbits;
415 {
416 uchar_t *p = (uchar_t*) in6p;
417
418 if (maskbits < 0 || maskbits >= IPV6_ABITS)
419 return;
420
421 p += maskbits / 8;
422 maskbits %= 8;
423
424 if (maskbits != 0)
425 *p++ &= 0xff << (8 - maskbits);
426
427 while (p < (((uchar_t*) in6p)) + sizeof(*in6p))
428 *p++ = 0;
429 }
430 #endif
431