xref: /freebsd/usr.sbin/ypserv/yp_access.c (revision 0957b409)
1 /*-
2  * SPDX-License-Identifier: BSD-4-Clause
3  *
4  * Copyright (c) 1995
5  *	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed by Bill Paul.
18  * 4. Neither the name of the author nor the names of any co-contributors
19  *    may be used to endorse or promote products derived from this software
20  *    without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED.  IN NO EVENT SHALL Bill Paul OR CONTRIBUTORS BE LIABLE
26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  *
34  */
35 
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38 
39 #include <stdlib.h>
40 #include <rpc/rpc.h>
41 #include <rpcsvc/yp.h>
42 #include <rpcsvc/yppasswd.h>
43 #include <rpcsvc/ypxfrd.h>
44 #include <sys/types.h>
45 #include <limits.h>
46 #include <db.h>
47 #include <sys/socket.h>
48 #include <netinet/in.h>
49 #include <arpa/inet.h>
50 #include <sys/stat.h>
51 #include <sys/fcntl.h>
52 #include <paths.h>
53 #include <errno.h>
54 #include <sys/param.h>
55 #include "yp_extern.h"
56 #ifdef TCP_WRAPPER
57 #include "tcpd.h"
58 #endif
59 
60 extern int debug;
61 
62 static const char *yp_procs[] = {
63 	/* NIS v1 */
64 	"ypoldproc_null",
65 	"ypoldproc_domain",
66 	"ypoldproc_domain_nonack",
67 	"ypoldproc_match",
68 	"ypoldproc_first",
69 	"ypoldproc_next",
70 	"ypoldproc_poll",
71 	"ypoldproc_push",
72 	"ypoldproc_get",
73 	"badproc1", /* placeholder */
74 	"badproc2", /* placeholder */
75 	"badproc3", /* placeholder */
76 
77 	/* NIS v2 */
78 	"ypproc_null",
79 	"ypproc_domain",
80 	"ypproc_domain_nonack",
81 	"ypproc_match",
82 	"ypproc_first",
83 	"ypproc_next",
84 	"ypproc_xfr",
85 	"ypproc_clear",
86 	"ypproc_all",
87 	"ypproc_master",
88 	"ypproc_order",
89 	"ypproc_maplist"
90 };
91 
92 struct securenet {
93 	struct in_addr net;
94 	struct in_addr mask;
95 	struct securenet *next;
96 };
97 
98 static struct securenet *securenets;
99 
100 #define LINEBUFSZ 1024
101 
102 #ifdef TCP_WRAPPER
103 int hosts_ctl(char *, char *, char *, char *);
104 #endif
105 
106 /*
107  * Read /var/yp/securenets file and initialize the securenets
108  * list. If the file doesn't exist, we set up a dummy entry that
109  * allows all hosts to connect.
110  */
111 void
112 load_securenets(void)
113 {
114 	FILE *fp;
115 	char path[MAXPATHLEN + 2];
116 	char linebuf[1024 + 2];
117 	struct securenet *tmp;
118 
119 	/*
120 	 * If securenets is not NULL, we are being called to reload
121 	 * the list; free the existing list before re-reading the
122 	 * securenets file.
123 	 */
124 	while (securenets) {
125 		tmp = securenets->next;
126 		free(securenets);
127 		securenets = tmp;
128 	}
129 
130 	snprintf(path, MAXPATHLEN, "%s/securenets", yp_dir);
131 
132 	if ((fp = fopen(path, "r")) == NULL) {
133 		if (errno == ENOENT) {
134 			securenets = malloc(sizeof(struct securenet));
135 			securenets->net.s_addr = INADDR_ANY;
136 			securenets->mask.s_addr = INADDR_ANY;
137 			securenets->next = NULL;
138 			return;
139 		} else {
140 			yp_error("fopen(%s) failed: %s", path, strerror(errno));
141 			exit(1);
142 		}
143 	}
144 
145 	securenets = NULL;
146 
147 	while (fgets(linebuf, LINEBUFSZ, fp)) {
148 		char addr1[20], addr2[20];
149 
150 		if ((linebuf[0] == '#')
151 		    || (strspn(linebuf, " \t\r\n") == strlen(linebuf)))
152 			continue;
153 		if (sscanf(linebuf, "%s %s", addr1, addr2) < 2) {
154 			yp_error("badly formatted securenets entry: %s",
155 							linebuf);
156 			continue;
157 		}
158 
159 		tmp = malloc(sizeof(struct securenet));
160 
161 		if (!inet_aton((char *)&addr1, (struct in_addr *)&tmp->net)) {
162 			yp_error("badly formatted securenets entry: %s", addr1);
163 			free(tmp);
164 			continue;
165 		}
166 
167 		if (!inet_aton((char *)&addr2, (struct in_addr *)&tmp->mask)) {
168 			yp_error("badly formatted securenets entry: %s", addr2);
169 			free(tmp);
170 			continue;
171 		}
172 
173 		tmp->next = securenets;
174 		securenets = tmp;
175 	}
176 
177 	fclose(fp);
178 
179 }
180 
181 /*
182  * Access control functions.
183  *
184  * yp_access() checks the mapname and client host address and watches for
185  * the following things:
186  *
187  * - If the client is referencing one of the master.passwd.* or shadow.* maps,
188  *   it must be using a privileged port to make its RPC to us. If it is, then
189  *   we can assume that the caller is root and allow the RPC to succeed. If it
190  *   isn't access is denied.
191  *
192  * - The client's IP address is checked against the securenets rules.
193  *   There are two kinds of securenets support: the built-in support,
194  *   which is very simple and depends on the presence of a
195  *   /var/yp/securenets file, and tcp-wrapper support, which requires
196  *   Wietse Venema's libwrap.a and tcpd.h. (Since the tcp-wrapper
197  *   package does not ship with FreeBSD, we use the built-in support
198  *   by default. Users can recompile the server with the tcp-wrapper library
199  *   if they already have it installed and want to use hosts.allow and
200  *   hosts.deny to control access instead of having a separate securenets
201  *   file.)
202  *
203  *   If no /var/yp/securenets file is present, the host access checks
204  *   are bypassed and all hosts are allowed to connect.
205  *
206  * The yp_validdomain() function checks the domain specified by the caller
207  * to make sure it's actually served by this server. This is more a sanity
208  * check than an a security check, but this seems to be the best place for
209  * it.
210  */
211 
212 #ifdef DB_CACHE
213 int
214 yp_access(const char *map, const char *domain, const struct svc_req *rqstp)
215 #else
216 int
217 yp_access(const char *map, const struct svc_req *rqstp)
218 #endif
219 {
220 	struct sockaddr_in *rqhost;
221 	int status_securenets = 0;
222 #ifdef TCP_WRAPPER
223 	int status_tcpwrap;
224 #endif
225 	static unsigned long oldaddr = 0;
226 	struct securenet *tmp;
227 	const char *yp_procedure = NULL;
228 	char procbuf[50];
229 
230 	if (rqstp->rq_prog != YPPASSWDPROG && rqstp->rq_prog != YPPROG) {
231 		snprintf(procbuf, sizeof(procbuf), "#%lu/#%lu",
232 		    (unsigned long)rqstp->rq_prog,
233 		    (unsigned long)rqstp->rq_proc);
234 		yp_procedure = (char *)&procbuf;
235 	} else {
236 		yp_procedure = rqstp->rq_prog == YPPASSWDPROG ?
237 		"yppasswdprog_update" :
238 		yp_procs[rqstp->rq_proc + (12 * (rqstp->rq_vers - 1))];
239 	}
240 
241 	rqhost = svc_getcaller(rqstp->rq_xprt);
242 
243 	if (debug) {
244 		yp_error("procedure %s called from %s:%d", yp_procedure,
245 			inet_ntoa(rqhost->sin_addr),
246 			ntohs(rqhost->sin_port));
247 		if (map != NULL)
248 			yp_error("client is referencing map \"%s\".", map);
249 	}
250 
251 	/* Check the map name if one was supplied. */
252 	if (map != NULL) {
253 		if (strchr(map, '/')) {
254 			yp_error("embedded slash in map name \"%s\" -- \
255 possible spoof attempt from %s:%d",
256 				map, inet_ntoa(rqhost->sin_addr),
257 				ntohs(rqhost->sin_port));
258 			return(1);
259 		}
260 #ifdef DB_CACHE
261 		if ((yp_testflag((char *)map, (char *)domain, YP_SECURE) ||
262 #else
263 		if ((strstr(map, "master.passwd.") || strstr(map, "shadow.") ||
264 #endif
265 		    (rqstp->rq_prog == YPPROG &&
266 		     rqstp->rq_proc == YPPROC_XFR) ||
267 		    (rqstp->rq_prog == YPXFRD_FREEBSD_PROG &&
268 		     rqstp->rq_proc == YPXFRD_GETMAP)) &&
269 		     ntohs(rqhost->sin_port) >= IPPORT_RESERVED) {
270 			yp_error("access to %s denied -- client %s:%d \
271 not privileged", map, inet_ntoa(rqhost->sin_addr), ntohs(rqhost->sin_port));
272 			return(1);
273 		}
274 	}
275 
276 #ifdef TCP_WRAPPER
277 	status_tcpwrap = hosts_ctl("ypserv", STRING_UNKNOWN,
278 			   inet_ntoa(rqhost->sin_addr), "");
279 #endif
280 	tmp = securenets;
281 	while (tmp) {
282 		if (((rqhost->sin_addr.s_addr & ~tmp->mask.s_addr)
283 		    | tmp->net.s_addr) == rqhost->sin_addr.s_addr) {
284 			status_securenets = 1;
285 			break;
286 		}
287 		tmp = tmp->next;
288 	}
289 
290 #ifdef TCP_WRAPPER
291 	if (status_securenets == 0 || status_tcpwrap == 0) {
292 #else
293 	if (status_securenets == 0) {
294 #endif
295 	/*
296 	 * One of the following two events occurred:
297 	 *
298 	 * (1) The /var/yp/securenets exists and the remote host does not
299 	 *     match any of the networks specified in it.
300 	 * (2) The hosts.allow file has denied access and TCP_WRAPPER is
301 	 *     defined.
302 	 *
303 	 * In either case deny access.
304 	 */
305 		if (rqhost->sin_addr.s_addr != oldaddr) {
306 			yp_error("connect from %s:%d to procedure %s refused",
307 					inet_ntoa(rqhost->sin_addr),
308 					ntohs(rqhost->sin_port),
309 					yp_procedure);
310 			oldaddr = rqhost->sin_addr.s_addr;
311 		}
312 		return(1);
313 	}
314 	return(0);
315 
316 }
317 
318 int
319 yp_validdomain(const char *domain)
320 {
321 	struct stat statbuf;
322 	char dompath[MAXPATHLEN + 2];
323 
324 	if (domain == NULL || strstr(domain, "binding") ||
325 	    !strcmp(domain, ".") || !strcmp(domain, "..") ||
326 	    strchr(domain, '/') || strlen(domain) > YPMAXDOMAIN)
327 		return(1);
328 
329 	snprintf(dompath, sizeof(dompath), "%s/%s", yp_dir, domain);
330 
331 	if (stat(dompath, &statbuf) < 0 || !S_ISDIR(statbuf.st_mode))
332 		return(1);
333 
334 
335 	return(0);
336 }
337