yp_access.c revision 331722 
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: stable/11/usr.sbin/ypserv/yp_access.c 331722 2018-03-29 02:50:57Z eadler $");
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
58extern int debug;
59
60static const char *yp_procs[] = {
61	/* NIS v1 */
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
90struct securenet {
91	struct in_addr net;
92	struct in_addr mask;
93	struct securenet *next;
94};
95
96static struct securenet *securenets;
97
98#define LINEBUFSZ 1024
99
100#ifdef TCP_WRAPPER
101int hosts_ctl(char *, char *, char *, char *);
102#endif
103
104/*
105 * Read /var/yp/securenets file and initialize the securenets
106 * list. If the file doesn't exist, we set up a dummy entry that
107 * allows all hosts to connect.
108 */
109void
110load_securenets(void)
111{
112	FILE *fp;
113	char path[MAXPATHLEN + 2];
114	char linebuf[1024 + 2];
115	struct securenet *tmp;
116
117	/*
118	 * If securenets is not NULL, we are being called to reload
119	 * the list; free the existing list before re-reading the
120	 * securenets file.
121	 */
122	while (securenets) {
123		tmp = securenets->next;
124		free(securenets);
125		securenets = tmp;
126	}
127
128	snprintf(path, MAXPATHLEN, "%s/securenets", yp_dir);
129
130	if ((fp = fopen(path, "r")) == NULL) {
131		if (errno == ENOENT) {
132			securenets = malloc(sizeof(struct securenet));
133			securenets->net.s_addr = INADDR_ANY;
134			securenets->mask.s_addr = INADDR_ANY;
135			securenets->next = NULL;
136			return;
137		} else {
138			yp_error("fopen(%s) failed: %s", path, strerror(errno));
139			exit(1);
140		}
141	}
142
143	securenets = NULL;
144
145	while (fgets(linebuf, LINEBUFSZ, fp)) {
146		char addr1[20], addr2[20];
147
148		if ((linebuf[0] == '#')
149		    || (strspn(linebuf, " \t\r\n") == strlen(linebuf)))
150			continue;
151		if (sscanf(linebuf, "%s %s", addr1, addr2) < 2) {
152			yp_error("badly formatted securenets entry: %s",
153							linebuf);
154			continue;
155		}
156
157		tmp = malloc(sizeof(struct securenet));
158
159		if (!inet_aton((char *)&addr1, (struct in_addr *)&tmp->net)) {
160			yp_error("badly formatted securenets entry: %s", addr1);
161			free(tmp);
162			continue;
163		}
164
165		if (!inet_aton((char *)&addr2, (struct in_addr *)&tmp->mask)) {
166			yp_error("badly formatted securenets entry: %s", addr2);
167			free(tmp);
168			continue;
169		}
170
171		tmp->next = securenets;
172		securenets = tmp;
173	}
174
175	fclose(fp);
176
177}
178
179/*
180 * Access control functions.
181 *
182 * yp_access() checks the mapname and client host address and watches for
183 * the following things:
184 *
185 * - If the client is referencing one of the master.passwd.* or shadow.* maps,
186 *   it must be using a privileged port to make its RPC to us. If it is, then
187 *   we can assume that the caller is root and allow the RPC to succeed. If it
188 *   isn't access is denied.
189 *
190 * - The client's IP address is checked against the securenets rules.
191 *   There are two kinds of securenets support: the built-in support,
192 *   which is very simple and depends on the presence of a
193 *   /var/yp/securenets file, and tcp-wrapper support, which requires
194 *   Wietse Venema's libwrap.a and tcpd.h. (Since the tcp-wrapper
195 *   package does not ship with FreeBSD, we use the built-in support
196 *   by default. Users can recompile the server with the tcp-wrapper library
197 *   if they already have it installed and want to use hosts.allow and
198 *   hosts.deny to control access instead of having a separate securenets
199 *   file.)
200 *
201 *   If no /var/yp/securenets file is present, the host access checks
202 *   are bypassed and all hosts are allowed to connect.
203 *
204 * The yp_validdomain() function checks the domain specified by the caller
205 * to make sure it's actually served by this server. This is more a sanity
206 * check than an a security check, but this seems to be the best place for
207 * it.
208 */
209
210#ifdef DB_CACHE
211int
212yp_access(const char *map, const char *domain, const struct svc_req *rqstp)
213#else
214int
215yp_access(const char *map, const struct svc_req *rqstp)
216#endif
217{
218	struct sockaddr_in *rqhost;
219	int status_securenets = 0;
220#ifdef TCP_WRAPPER
221	int status_tcpwrap;
222#endif
223	static unsigned long oldaddr = 0;
224	struct securenet *tmp;
225	const char *yp_procedure = NULL;
226	char procbuf[50];
227
228	if (rqstp->rq_prog != YPPASSWDPROG && rqstp->rq_prog != YPPROG) {
229		snprintf(procbuf, sizeof(procbuf), "#%lu/#%lu",
230		    (unsigned long)rqstp->rq_prog,
231		    (unsigned long)rqstp->rq_proc);
232		yp_procedure = (char *)&procbuf;
233	} else {
234		yp_procedure = rqstp->rq_prog == YPPASSWDPROG ?
235		"yppasswdprog_update" :
236		yp_procs[rqstp->rq_proc + (12 * (rqstp->rq_vers - 1))];
237	}
238
239	rqhost = svc_getcaller(rqstp->rq_xprt);
240
241	if (debug) {
242		yp_error("procedure %s called from %s:%d", yp_procedure,
243			inet_ntoa(rqhost->sin_addr),
244			ntohs(rqhost->sin_port));
245		if (map != NULL)
246			yp_error("client is referencing map \"%s\".", map);
247	}
248
249	/* Check the map name if one was supplied. */
250	if (map != NULL) {
251		if (strchr(map, '/')) {
252			yp_error("embedded slash in map name \"%s\" -- \
253possible spoof attempt from %s:%d",
254				map, inet_ntoa(rqhost->sin_addr),
255				ntohs(rqhost->sin_port));
256			return(1);
257		}
258#ifdef DB_CACHE
259		if ((yp_testflag((char *)map, (char *)domain, YP_SECURE) ||
260#else
261		if ((strstr(map, "master.passwd.") || strstr(map, "shadow.") ||
262#endif
263		    (rqstp->rq_prog == YPPROG &&
264		     rqstp->rq_proc == YPPROC_XFR) ||
265		    (rqstp->rq_prog == YPXFRD_FREEBSD_PROG &&
266		     rqstp->rq_proc == YPXFRD_GETMAP)) &&
267		     ntohs(rqhost->sin_port) >= IPPORT_RESERVED) {
268			yp_error("access to %s denied -- client %s:%d \
269not privileged", map, inet_ntoa(rqhost->sin_addr), ntohs(rqhost->sin_port));
270			return(1);
271		}
272	}
273
274#ifdef TCP_WRAPPER
275	status_tcpwrap = hosts_ctl("ypserv", STRING_UNKNOWN,
276			   inet_ntoa(rqhost->sin_addr), "");
277#endif
278	tmp = securenets;
279	while (tmp) {
280		if (((rqhost->sin_addr.s_addr & ~tmp->mask.s_addr)
281		    | tmp->net.s_addr) == rqhost->sin_addr.s_addr) {
282			status_securenets = 1;
283			break;
284		}
285		tmp = tmp->next;
286	}
287
288#ifdef TCP_WRAPPER
289	if (status_securenets == 0 || status_tcpwrap == 0) {
290#else
291	if (status_securenets == 0) {
292#endif
293	/*
294	 * One of the following two events occurred:
295	 *
296	 * (1) The /var/yp/securenets exists and the remote host does not
297	 *     match any of the networks specified in it.
298	 * (2) The hosts.allow file has denied access and TCP_WRAPPER is
299	 *     defined.
300	 *
301	 * In either case deny access.
302	 */
303		if (rqhost->sin_addr.s_addr != oldaddr) {
304			yp_error("connect from %s:%d to procedure %s refused",
305					inet_ntoa(rqhost->sin_addr),
306					ntohs(rqhost->sin_port),
307					yp_procedure);
308			oldaddr = rqhost->sin_addr.s_addr;
309		}
310		return(1);
311	}
312	return(0);
313
314}
315
316int
317yp_validdomain(const char *domain)
318{
319	struct stat statbuf;
320	char dompath[MAXPATHLEN + 2];
321
322	if (domain == NULL || strstr(domain, "binding") ||
323	    !strcmp(domain, ".") || !strcmp(domain, "..") ||
324	    strchr(domain, '/') || strlen(domain) > YPMAXDOMAIN)
325		return(1);
326
327	snprintf(dompath, sizeof(dompath), "%s/%s", yp_dir, domain);
328
329	if (stat(dompath, &statbuf) < 0 || !S_ISDIR(statbuf.st_mode))
330		return(1);
331
332
333	return(0);
334}
335