xref: /freebsd/usr.sbin/ypserv/yp_access.c (revision ba00ec3d539f213abbda3a45ef8c539306cac098)
1 /*
2  * Copyright (c) 1995
3  *	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by Bill Paul.
16  * 4. Neither the name of the author nor the names of any co-contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL Bill Paul OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  *
32  */
33 
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36 
37 #include <stdlib.h>
38 #include <rpc/rpc.h>
39 #include <rpcsvc/yp.h>
40 #include <rpcsvc/yppasswd.h>
41 #include <rpcsvc/ypxfrd.h>
42 #include <sys/types.h>
43 #include <limits.h>
44 #include <db.h>
45 #include <sys/socket.h>
46 #include <netinet/in.h>
47 #include <arpa/inet.h>
48 #include <sys/stat.h>
49 #include <sys/fcntl.h>
50 #include <paths.h>
51 #include <errno.h>
52 #include <sys/param.h>
53 #include "yp_extern.h"
54 #ifdef TCP_WRAPPER
55 #include "tcpd.h"
56 #endif
57 
58 extern int debug;
59 
60 			/* NIS v1 */
61 const char *yp_procs[] = {
62 	"ypoldproc_null",
63 	"ypoldproc_domain",
64 	"ypoldproc_domain_nonack",
65 	"ypoldproc_match",
66 	"ypoldproc_first",
67 	"ypoldproc_next",
68 	"ypoldproc_poll",
69 	"ypoldproc_push",
70 	"ypoldproc_get",
71 	"badproc1", /* placeholder */
72 	"badproc2", /* placeholder */
73 	"badproc3", /* placeholder */
74 
75 	/* NIS v2 */
76 	"ypproc_null",
77 	"ypproc_domain",
78 	"ypproc_domain_nonack",
79 	"ypproc_match",
80 	"ypproc_first",
81 	"ypproc_next",
82 	"ypproc_xfr",
83 	"ypproc_clear",
84 	"ypproc_all",
85 	"ypproc_master",
86 	"ypproc_order",
87 	"ypproc_maplist"
88 };
89 
90 struct securenet {
91 	struct in_addr net;
92 	struct in_addr mask;
93 	struct securenet *next;
94 };
95 
96 struct securenet *securenets;
97 
98 #define LINEBUFSZ 1024
99 
100 /*
101  * Read /var/yp/securenets file and initialize the securenets
102  * list. If the file doesn't exist, we set up a dummy entry that
103  * allows all hosts to connect.
104  */
105 void
106 load_securenets(void)
107 {
108 	FILE *fp;
109 	char path[MAXPATHLEN + 2];
110 	char linebuf[1024 + 2];
111 	struct securenet *tmp;
112 
113 	/*
114 	 * If securenets is not NULL, we are being called to reload
115 	 * the list; free the existing list before re-reading the
116 	 * securenets file.
117 	 */
118 	while (securenets) {
119 		tmp = securenets->next;
120 		free(securenets);
121 		securenets = tmp;
122 	}
123 
124 	snprintf(path, MAXPATHLEN, "%s/securenets", yp_dir);
125 
126 	if ((fp = fopen(path, "r")) == NULL) {
127 		if (errno == ENOENT) {
128 			securenets = (struct securenet *)malloc(sizeof(struct securenet));
129 			securenets->net.s_addr = INADDR_ANY;
130 			securenets->mask.s_addr = INADDR_ANY;
131 			securenets->next = NULL;
132 			return;
133 		} else {
134 			yp_error("fopen(%s) failed: %s", path, strerror(errno));
135 			exit(1);
136 		}
137 	}
138 
139 	securenets = NULL;
140 
141 	while (fgets(linebuf, LINEBUFSZ, fp)) {
142 		char addr1[20], addr2[20];
143 
144 		if ((linebuf[0] == '#')
145 		    || (strspn(linebuf, " \t\r\n") == strlen(linebuf)))
146 			continue;
147 		if (sscanf(linebuf, "%s %s", addr1, addr2) < 2) {
148 			yp_error("badly formatted securenets entry: %s",
149 							linebuf);
150 			continue;
151 		}
152 
153 		tmp = (struct securenet *)malloc(sizeof(struct securenet));
154 
155 		if (!inet_aton((char *)&addr1, (struct in_addr *)&tmp->net)) {
156 			yp_error("badly formatted securenets entry: %s", addr1);
157 			free(tmp);
158 			continue;
159 		}
160 
161 		if (!inet_aton((char *)&addr2, (struct in_addr *)&tmp->mask)) {
162 			yp_error("badly formatted securenets entry: %s", addr2);
163 			free(tmp);
164 			continue;
165 		}
166 
167 		tmp->next = securenets;
168 		securenets = tmp;
169 	}
170 
171 	fclose(fp);
172 
173 }
174 
175 /*
176  * Access control functions.
177  *
178  * yp_access() checks the mapname and client host address and watches for
179  * the following things:
180  *
181  * - If the client is referencing one of the master.passwd.* or shadow.* maps,
182  *   it must be using a privileged port to make its RPC to us. If it is, then
183  *   we can assume that the caller is root and allow the RPC to succeed. If it
184  *   isn't access is denied.
185  *
186  * - The client's IP address is checked against the securenets rules.
187  *   There are two kinds of securenets support: the built-in support,
188  *   which is very simple and depends on the presence of a
189  *   /var/yp/securenets file, and tcp-wrapper support, which requires
190  *   Wietse Venema's libwrap.a and tcpd.h. (Since the tcp-wrapper
191  *   package does not ship with FreeBSD, we use the built-in support
192  *   by default. Users can recompile the server with the tcp-wrapper library
193  *   if they already have it installed and want to use hosts.allow and
194  *   hosts.deny to control access instead of having a separate securenets
195  *   file.)
196  *
197  *   If no /var/yp/securenets file is present, the host access checks
198  *   are bypassed and all hosts are allowed to connect.
199  *
200  * The yp_validdomain() function checks the domain specified by the caller
201  * to make sure it's actually served by this server. This is more a sanity
202  * check than an a security check, but this seems to be the best place for
203  * it.
204  */
205 
206 #ifdef DB_CACHE
207 int
208 yp_access(const char *map, const char *domain, const struct svc_req *rqstp)
209 #else
210 int
211 yp_access(const char *map, const struct svc_req *rqstp)
212 #endif
213 {
214 	struct sockaddr_in *rqhost;
215 	int status_securenets = 0;
216 #ifdef TCP_WRAPPER
217 	int status_tcpwrap;
218 #endif
219 	static unsigned long oldaddr = 0;
220 	struct securenet *tmp;
221 	const char *yp_procedure = NULL;
222 	char procbuf[50];
223 
224 	if (rqstp->rq_prog != YPPASSWDPROG && rqstp->rq_prog != YPPROG) {
225 		snprintf(procbuf, sizeof(procbuf), "#%lu/#%lu",
226 		    (unsigned long)rqstp->rq_prog,
227 		    (unsigned long)rqstp->rq_proc);
228 		yp_procedure = (char *)&procbuf;
229 	} else {
230 		yp_procedure = rqstp->rq_prog == YPPASSWDPROG ?
231 		"yppasswdprog_update" :
232 		yp_procs[rqstp->rq_proc + (12 * (rqstp->rq_vers - 1))];
233 	}
234 
235 	rqhost = svc_getcaller(rqstp->rq_xprt);
236 
237 	if (debug) {
238 		yp_error("procedure %s called from %s:%d", yp_procedure,
239 			inet_ntoa(rqhost->sin_addr),
240 			ntohs(rqhost->sin_port));
241 		if (map != NULL)
242 			yp_error("client is referencing map \"%s\".", map);
243 	}
244 
245 	/* Check the map name if one was supplied. */
246 	if (map != NULL) {
247 		if (strchr(map, '/')) {
248 			yp_error("embedded slash in map name \"%s\" -- \
249 possible spoof attempt from %s:%d",
250 				map, inet_ntoa(rqhost->sin_addr),
251 				ntohs(rqhost->sin_port));
252 			return(1);
253 		}
254 #ifdef DB_CACHE
255 		if ((yp_testflag((char *)map, (char *)domain, YP_SECURE) ||
256 #else
257 		if ((strstr(map, "master.passwd.") || strstr(map, "shadow.") ||
258 #endif
259 		    (rqstp->rq_prog == YPPROG &&
260 		     rqstp->rq_proc == YPPROC_XFR) ||
261 		    (rqstp->rq_prog == YPXFRD_FREEBSD_PROG &&
262 		     rqstp->rq_proc == YPXFRD_GETMAP)) &&
263 		     ntohs(rqhost->sin_port) >= IPPORT_RESERVED) {
264 			yp_error("access to %s denied -- client %s:%d \
265 not privileged", map, inet_ntoa(rqhost->sin_addr), ntohs(rqhost->sin_port));
266 			return(1);
267 		}
268 	}
269 
270 #ifdef TCP_WRAPPER
271 	status_tcpwrap = hosts_ctl("ypserv", STRING_UNKNOWN,
272 			   inet_ntoa(rqhost->sin_addr), "");
273 #endif
274 	tmp = securenets;
275 	while (tmp) {
276 		if (((rqhost->sin_addr.s_addr & ~tmp->mask.s_addr)
277 		    | tmp->net.s_addr) == rqhost->sin_addr.s_addr) {
278 			status_securenets = 1;
279 			break;
280 		}
281 		tmp = tmp->next;
282 	}
283 
284 #ifdef TCP_WRAPPER
285 	if (status_securenets == 0 || status_tcpwrap == 0) {
286 #else
287 	if (status_securenets == 0) {
288 #endif
289 	/*
290 	 * One of the following two events occurred:
291 	 *
292 	 * (1) The /var/yp/securenets exists and the remote host does not
293 	 *     match any of the networks specified in it.
294 	 * (2) The hosts.allow file has denied access and TCP_WRAPPER is
295 	 *     defined.
296 	 *
297 	 * In either case deny access.
298 	 */
299 		if (rqhost->sin_addr.s_addr != oldaddr) {
300 			yp_error("connect from %s:%d to procedure %s refused",
301 					inet_ntoa(rqhost->sin_addr),
302 					ntohs(rqhost->sin_port),
303 					yp_procedure);
304 			oldaddr = rqhost->sin_addr.s_addr;
305 		}
306 		return(1);
307 	}
308 	return(0);
309 
310 }
311 
312 int
313 yp_validdomain(const char *domain)
314 {
315 	struct stat statbuf;
316 	char dompath[MAXPATHLEN + 2];
317 
318 	if (domain == NULL || strstr(domain, "binding") ||
319 	    !strcmp(domain, ".") || !strcmp(domain, "..") ||
320 	    strchr(domain, '/') || strlen(domain) > YPMAXDOMAIN)
321 		return(1);
322 
323 	snprintf(dompath, sizeof(dompath), "%s/%s", yp_dir, domain);
324 
325 	if (stat(dompath, &statbuf) < 0 || !S_ISDIR(statbuf.st_mode))
326 		return(1);
327 
328 
329 	return(0);
330 }
331