usr.sbin/ypserv/yp_access.c

   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 static 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
  90 struct securenet {
  91         struct in_addr net;
  92         struct in_addr mask;
  93         struct securenet *next;
  94 };
  95
  96 static struct securenet *securenets;
  97
  98 #define LINEBUFSZ 1024
  99
 100 #ifdef TCP_WRAPPER
 101 int 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  */
 109 void
 110 load_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
 211 int
 212 yp_access(const char *map, const char *domain, const struct svc_req *rqstp)
 213 #else
 214 int
 215 yp_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\" -- \
 253 possible 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 \
 269 not 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
 316 int
 317 yp_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 }