1 /*
2 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 #pragma ident "%Z%%M% %I% %E% SMI"
7
8 /*
9 * This module implements a simple access control language that is based on
10 * host (or domain) names, NIS (host) netgroup names, IP addresses (or
11 * network numbers) and daemon process names. When a match is found the
12 * search is terminated, and depending on whether PROCESS_OPTIONS is defined,
13 * a list of options is executed or an optional shell command is executed.
14 *
15 * Host and user names are looked up on demand, provided that suitable endpoint
16 * information is available as sockaddr_in structures or TLI netbufs. As a
17 * side effect, the pattern matching process may change the contents of
18 * request structure fields.
19 *
20 * Diagnostics are reported through syslog(3).
21 *
22 * Compile with -DNETGROUP if your library provides support for netgroups.
23 *
24 * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
25 */
26
27 #ifndef lint
28 static char sccsid[] = "@(#) hosts_access.c 1.21 97/02/12 02:13:22";
29 #endif
30
31 /* System libraries. */
32
33 #include <sys/types.h>
34 #include <sys/param.h>
35 #include <netinet/in.h>
36 #include <arpa/inet.h>
37 #include <rpcsvc/ypclnt.h>
38 #include <netdb.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <unistd.h>
42 #include <syslog.h>
43 #include <ctype.h>
44 #include <errno.h>
45 #include <setjmp.h>
46 #include <string.h>
47
48 extern char *fgets();
49 extern int errno;
50
51 #ifndef INADDR_NONE
52 #define INADDR_NONE (-1) /* XXX should be 0xffffffff */
53 #endif
54
55 /* Local stuff. */
56
57 #include "tcpd.h"
58
59 /* Error handling. */
60
61 extern jmp_buf tcpd_buf;
62
63 /* Delimiters for lists of daemons or clients. */
64
65 static char sep[] = ", \t\r\n";
66
67 /* Constants to be used in assignments only, not in comparisons... */
68
69 #define YES 1
70 #define NO 0
71
72 /*
73 * These variables are globally visible so that they can be redirected in
74 * verification mode.
75 */
76
77 char *hosts_allow_table = HOSTS_ALLOW;
78 char *hosts_deny_table = HOSTS_DENY;
79 int hosts_access_verbose = 0;
80
81 /*
82 * In a long-running process, we are not at liberty to just go away.
83 */
84
85 int resident = (-1); /* -1, 0: unknown; +1: yes */
86
87 /* Forward declarations. */
88
89 static int table_match();
90 static int list_match();
91 static int server_match();
92 static int client_match();
93 static int host_match();
94 static int string_match();
95 static int masked_match();
96 #ifdef HAVE_IPV6
97 static void ipv6_mask();
98 #endif
99
100 /* Size of logical line buffer. */
101
102 #define BUFLEN 2048
103
104 /* hosts_access - host access control facility */
105
hosts_access(request)106 int hosts_access(request)
107 struct request_info *request;
108 {
109 int verdict;
110
111 /*
112 * If the (daemon, client) pair is matched by an entry in the file
113 * /etc/hosts.allow, access is granted. Otherwise, if the (daemon,
114 * client) pair is matched by an entry in the file /etc/hosts.deny,
115 * access is denied. Otherwise, access is granted. A non-existent
116 * access-control file is treated as an empty file.
117 *
118 * After a rule has been matched, the optional language extensions may
119 * decide to grant or refuse service anyway. Or, while a rule is being
120 * processed, a serious error is found, and it seems better to play safe
121 * and deny service. All this is done by jumping back into the
122 * hosts_access() routine, bypassing the regular return from the
123 * table_match() function calls below.
124 */
125
126 if (resident <= 0)
127 resident++;
128 verdict = setjmp(tcpd_buf);
129 if (verdict != 0)
130 return (verdict == AC_PERMIT);
131 if (table_match(hosts_allow_table, request))
132 return (YES);
133 if (table_match(hosts_deny_table, request))
134 return (NO);
135 return (YES);
136 }
137
138 /* table_match - match table entries with (daemon, client) pair */
139
table_match(table,request)140 static int table_match(table, request)
141 char *table;
142 struct request_info *request;
143 {
144 FILE *fp;
145 char sv_list[BUFLEN]; /* becomes list of daemons */
146 char *cl_list; /* becomes list of clients */
147 char *sh_cmd; /* becomes optional shell command */
148 int match = NO;
149 struct tcpd_context saved_context;
150
151 saved_context = tcpd_context; /* stupid compilers */
152
153 /*
154 * Between the fopen() and fclose() calls, avoid jumps that may cause
155 * file descriptor leaks.
156 */
157
158 if ((fp = fopen(table, "r")) != 0) {
159 tcpd_context.file = table;
160 tcpd_context.line = 0;
161 while (match == NO && xgets(sv_list, sizeof(sv_list), fp) != 0) {
162 if (sv_list[strlen(sv_list) - 1] != '\n') {
163 tcpd_warn("missing newline or line too long");
164 continue;
165 }
166 if (sv_list[0] == '#' || sv_list[strspn(sv_list, " \t\r\n")] == 0)
167 continue;
168 if ((cl_list = split_at(skip_ipv6_addrs(sv_list), ':')) == 0) {
169 tcpd_warn("missing \":\" separator");
170 continue;
171 }
172 sh_cmd = split_at(skip_ipv6_addrs(cl_list), ':');
173 match = list_match(sv_list, request, server_match)
174 && list_match(cl_list, request, client_match);
175 }
176 (void) fclose(fp);
177 } else if (errno != ENOENT) {
178 tcpd_warn("cannot open %s: %m", table);
179 }
180 if (match) {
181 if (hosts_access_verbose > 1)
182 syslog(LOG_DEBUG, "matched: %s line %d",
183 tcpd_context.file, tcpd_context.line);
184 if (sh_cmd) {
185 #ifdef PROCESS_OPTIONS
186 process_options(sh_cmd, request);
187 #else
188 char cmd[BUFSIZ];
189 shell_cmd(percent_x(cmd, sizeof(cmd), sh_cmd, request));
190 #endif
191 }
192 }
193 tcpd_context = saved_context;
194 return (match);
195 }
196
197 /* list_match - match a request against a list of patterns with exceptions */
198
list_match(list,request,match_fn)199 static int list_match(list, request, match_fn)
200 char *list;
201 struct request_info *request;
202 int (*match_fn) ();
203 {
204 char *tok;
205
206 /*
207 * Process tokens one at a time. We have exhausted all possible matches
208 * when we reach an "EXCEPT" token or the end of the list. If we do find
209 * a match, look for an "EXCEPT" list and recurse to determine whether
210 * the match is affected by any exceptions.
211 */
212
213 for (tok = strtok(list, sep); tok != 0; tok = strtok((char *) 0, sep)) {
214 if (STR_EQ(tok, "EXCEPT")) /* EXCEPT: give up */
215 return (NO);
216 if (match_fn(tok, request)) { /* YES: look for exceptions */
217 while ((tok = strtok((char *) 0, sep)) && STR_NE(tok, "EXCEPT"))
218 /* VOID */ ;
219 return (tok == 0 || list_match((char *) 0, request, match_fn) == 0);
220 }
221 }
222 return (NO);
223 }
224
225 /* server_match - match server information */
226
server_match(tok,request)227 static int server_match(tok, request)
228 char *tok;
229 struct request_info *request;
230 {
231 char *host;
232
233 if ((host = split_at(tok + 1, '@')) == 0) { /* plain daemon */
234 return (string_match(tok, eval_daemon(request)));
235 } else { /* daemon@host */
236 return (string_match(tok, eval_daemon(request))
237 && host_match(host, request->server));
238 }
239 }
240
241 /* client_match - match client information */
242
client_match(tok,request)243 static int client_match(tok, request)
244 char *tok;
245 struct request_info *request;
246 {
247 char *host;
248
249 if ((host = split_at(tok + 1, '@')) == 0) { /* plain host */
250 return (host_match(tok, request->client));
251 } else { /* user@host */
252 return (host_match(host, request->client)
253 && string_match(tok, eval_user(request)));
254 }
255 }
256
257 /* host_match - match host name and/or address against pattern */
258
host_match(tok,host)259 static int host_match(tok, host)
260 char *tok;
261 struct host_info *host;
262 {
263 char *mask;
264
265 /*
266 * This code looks a little hairy because we want to avoid unnecessary
267 * hostname lookups.
268 *
269 * The KNOWN pattern requires that both address AND name be known; some
270 * patterns are specific to host names or to host addresses; all other
271 * patterns are satisfied when either the address OR the name match.
272 */
273
274 if (tok[0] == '@') { /* netgroup: look it up */
275 #ifdef NETGROUP
276 static char *mydomain = 0;
277 if (mydomain == 0)
278 yp_get_default_domain(&mydomain);
279 return (innetgr(tok + 1, eval_hostname(host), (char *) 0, mydomain));
280 #else
281 tcpd_warn("netgroup support is disabled"); /* not tcpd_jump() */
282 return (NO);
283 #endif
284 } else if (STR_EQ(tok, "KNOWN")) { /* check address and name */
285 char *name = eval_hostname(host);
286 return (STR_NE(eval_hostaddr(host), unknown) && HOSTNAME_KNOWN(name));
287 } else if (STR_EQ(tok, "LOCAL")) { /* local: no dots in name */
288 char *name = eval_hostname(host);
289 return (strchr(name, '.') == 0 && HOSTNAME_KNOWN(name));
290 #ifdef HAVE_IPV6
291 } else if (tok[0] == '[') { /* IPv6 address */
292 struct in6_addr in6, hostin6, *hip;
293 char *cbr;
294 char *slash;
295 int mask = IPV6_ABITS;
296
297 /*
298 * In some cases we don't get the sockaddr, only the addr.
299 * We use inet_pton to convert it to its binary representation
300 * and match against that.
301 */
302 if (host->sin == NULL) {
303 if (host->addr == NULL ||
304 inet_pton(AF_INET6, host->addr, &hostin6) != 1) {
305 return (NO);
306 }
307 hip = &hostin6;
308 } else {
309 if (SGFAM(host->sin) != AF_INET6)
310 return (NO);
311 hip = &host->sin->sg_sin6.sin6_addr;
312 }
313
314 if (cbr = strchr(tok, ']'))
315 *cbr = '\0';
316
317 /*
318 * A /nnn prefix specifies how many bits of the address we
319 * need to check.
320 */
321 if (slash = strchr(tok, '/')) {
322 *slash = '\0';
323 mask = atoi(slash+1);
324 if (mask < 0 || mask > IPV6_ABITS) {
325 tcpd_warn("bad IP6 prefix specification");
326 return (NO);
327 }
328 /* Copy, because we need to modify it below */
329 if (host->sin != NULL) {
330 hostin6 = host->sin->sg_sin6.sin6_addr;
331 hip = &hostin6;
332 }
333 }
334
335 if (cbr == NULL || inet_pton(AF_INET6, tok+1, &in6) != 1) {
336 tcpd_warn("bad IP6 address specification");
337 return (NO);
338 }
339 /*
340 * Zero the bits we're not interested in in both addresses
341 * then compare. Note that we take a copy of the host info
342 * in that case.
343 */
344 if (mask != IPV6_ABITS) {
345 ipv6_mask(&in6, mask);
346 ipv6_mask(hip, mask);
347 }
348 if (memcmp(&in6, hip, sizeof(in6)) == 0)
349 return (YES);
350 return (NO);
351 #endif
352 } else if ((mask = split_at(tok, '/')) != 0) { /* net/mask */
353 return (masked_match(tok, mask, eval_hostaddr(host)));
354 } else { /* anything else */
355 return (string_match(tok, eval_hostaddr(host))
356 || (NOT_INADDR(tok) && string_match(tok, eval_hostname(host))));
357 }
358 }
359
360 /* string_match - match string against pattern */
361
string_match(tok,string)362 static int string_match(tok, string)
363 char *tok;
364 char *string;
365 {
366 int n;
367
368 if (tok[0] == '.') { /* suffix */
369 n = strlen(string) - strlen(tok);
370 return (n > 0 && STR_EQ(tok, string + n));
371 } else if (STR_EQ(tok, "ALL")) { /* all: match any */
372 return (YES);
373 } else if (STR_EQ(tok, "KNOWN")) { /* not unknown */
374 return (STR_NE(string, unknown));
375 } else if (tok[(n = strlen(tok)) - 1] == '.') { /* prefix */
376 return (STRN_EQ(tok, string, n));
377 } else { /* exact match */
378 return (STR_EQ(tok, string));
379 }
380 }
381
382 /* masked_match - match address against netnumber/netmask */
383
masked_match(net_tok,mask_tok,string)384 static int masked_match(net_tok, mask_tok, string)
385 char *net_tok;
386 char *mask_tok;
387 char *string;
388 {
389 unsigned long net;
390 unsigned long mask;
391 unsigned long addr;
392
393 /*
394 * Disallow forms other than dotted quad: the treatment that inet_addr()
395 * gives to forms with less than four components is inconsistent with the
396 * access control language. John P. Rouillard <rouilj@cs.umb.edu>.
397 */
398
399 if ((addr = dot_quad_addr(string)) == INADDR_NONE)
400 return (NO);
401 if ((net = dot_quad_addr(net_tok)) == INADDR_NONE
402 || (mask = dot_quad_addr(mask_tok)) == INADDR_NONE) {
403 tcpd_warn("bad net/mask expression: %s/%s", net_tok, mask_tok);
404 return (NO); /* not tcpd_jump() */
405 }
406 return ((addr & mask) == net);
407 }
408
409 #ifdef HAVE_IPV6
410 /*
411 * Function that zeros all but the first "maskbits" bits of the IPV6 address
412 * This function can be made generic by specifying an address length as
413 * extra parameter. (So Wietse can implement 1.2.3.4/16)
414 */
ipv6_mask(in6p,maskbits)415 static void ipv6_mask(in6p, maskbits)
416 struct in6_addr *in6p;
417 int maskbits;
418 {
419 uchar_t *p = (uchar_t*) in6p;
420
421 if (maskbits < 0 || maskbits >= IPV6_ABITS)
422 return;
423
424 p += maskbits / 8;
425 maskbits %= 8;
426
427 if (maskbits != 0)
428 *p++ &= 0xff << (8 - maskbits);
429
430 while (p < (((uchar_t*) in6p)) + sizeof(*in6p))
431 *p++ = 0;
432 }
433 #endif
434