1 /* $OpenBSD: dhcpd.c,v 1.57 2019/08/06 11:07:37 krw Exp $ */ 2 3 /* 4 * Copyright (c) 2004 Henning Brauer <henning@cvs.openbsd.org> 5 * Copyright (c) 1995, 1996, 1997, 1998, 1999 6 * The Internet Software Consortium. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of The Internet Software Consortium nor the names 18 * of its contributors may be used to endorse or promote products derived 19 * from this software without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND 22 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 23 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 25 * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR 26 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 27 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 28 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 29 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 30 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * This software has been written for the Internet Software Consortium 36 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie 37 * Enterprises. To learn more about the Internet Software Consortium, 38 * see ``http://www.vix.com/isc''. To learn more about Vixie 39 * Enterprises, see ``http://www.vix.com''. 40 */ 41 42 #include <sys/types.h> 43 #include <sys/socket.h> 44 45 #include <net/if.h> 46 47 #include <arpa/inet.h> 48 49 #include <err.h> 50 #include <netdb.h> 51 #include <pwd.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <string.h> 55 #include <syslog.h> 56 #include <time.h> 57 #include <unistd.h> 58 59 #include "dhcp.h" 60 #include "tree.h" 61 #include "dhcpd.h" 62 #include "log.h" 63 #include "sync.h" 64 65 66 __dead void usage(void); 67 68 time_t cur_time, last_scan; 69 struct group root_group; 70 71 u_int16_t server_port; 72 u_int16_t client_port; 73 74 struct passwd *pw; 75 int log_priority; 76 int pfpipe[2]; 77 int gotpipe = 0; 78 int syncrecv; 79 int syncsend; 80 pid_t pfproc_pid = -1; 81 char *path_dhcpd_conf = _PATH_DHCPD_CONF; 82 char *path_dhcpd_db = _PATH_DHCPD_DB; 83 char *abandoned_tab = NULL; 84 char *changedmac_tab = NULL; 85 char *leased_tab = NULL; 86 87 int 88 main(int argc, char *argv[]) 89 { 90 int ch, cftest = 0, daemonize = 1, rdomain = -1, udpsockmode = 0; 91 char *sync_iface = NULL; 92 char *sync_baddr = NULL; 93 u_short sync_port = 0; 94 struct servent *ent; 95 struct in_addr udpaddr; 96 97 log_init(1, LOG_DAEMON); /* log to stderr until daemonized */ 98 log_setverbose(1); 99 100 opterr = 0; 101 while ((ch = getopt(argc, argv, "A:C:L:c:dfl:nu::Y:y:")) != -1) 102 switch (ch) { 103 case 'Y': 104 syncsend = 1; 105 break; 106 case 'y': 107 syncrecv = 1; 108 break; 109 } 110 if (syncsend || syncrecv) { 111 if ((ent = getservbyname("dhcpd-sync", "udp")) == NULL) 112 errx(1, "Can't find service \"dhcpd-sync\" in " 113 "/etc/services"); 114 sync_port = ntohs(ent->s_port); 115 } 116 117 udpaddr.s_addr = htonl(INADDR_BROADCAST); 118 119 optreset = optind = opterr = 1; 120 while ((ch = getopt(argc, argv, "A:C:L:c:dfl:nu::Y:y:")) != -1) 121 switch (ch) { 122 case 'A': 123 abandoned_tab = optarg; 124 break; 125 case 'C': 126 changedmac_tab = optarg; 127 break; 128 case 'L': 129 leased_tab = optarg; 130 break; 131 case 'c': 132 path_dhcpd_conf = optarg; 133 break; 134 case 'd': 135 daemonize = 0; 136 break; 137 case 'f': 138 daemonize = 0; 139 break; 140 case 'l': 141 path_dhcpd_db = optarg; 142 break; 143 case 'n': 144 daemonize = 0; 145 cftest = 1; 146 break; 147 case 'u': 148 udpsockmode = 1; 149 if (optarg != NULL) { 150 if (inet_aton(optarg, &udpaddr) != 1) 151 errx(1, "Cannot parse binding IP " 152 "address: %s", optarg); 153 } 154 break; 155 case 'Y': 156 if (sync_addhost(optarg, sync_port) != 0) 157 sync_iface = optarg; 158 syncsend = 1; 159 break; 160 case 'y': 161 sync_baddr = optarg; 162 syncrecv = 1; 163 break; 164 default: 165 usage(); 166 } 167 168 argc -= optind; 169 argv += optind; 170 171 while (argc > 0) { 172 struct interface_info *tmp = calloc(1, sizeof(*tmp)); 173 if (!tmp) 174 fatalx("calloc"); 175 strlcpy(tmp->name, argv[0], sizeof(tmp->name)); 176 tmp->next = interfaces; 177 interfaces = tmp; 178 argc--; 179 argv++; 180 } 181 182 /* Default DHCP/BOOTP ports. */ 183 server_port = htons(SERVER_PORT); 184 client_port = htons(CLIENT_PORT); 185 186 tzset(); 187 188 time(&cur_time); 189 if (!readconf()) 190 fatalx("Configuration file errors encountered"); 191 192 if (cftest) 193 exit(0); 194 195 db_startup(); 196 if (!udpsockmode || argc > 0) 197 discover_interfaces(&rdomain); 198 199 if (rdomain != -1) 200 if (setrtable(rdomain) == -1) 201 fatal("setrtable"); 202 203 if (syncsend || syncrecv) { 204 syncfd = sync_init(sync_iface, sync_baddr, sync_port); 205 if (syncfd == -1) 206 err(1, "sync init"); 207 } 208 209 if (daemonize) 210 daemon(0, 0); 211 212 log_init(0, LOG_DAEMON); /* stop logging to stderr */ 213 log_setverbose(0); 214 215 if ((pw = getpwnam("_dhcp")) == NULL) 216 fatalx("user \"_dhcp\" not found"); 217 218 /* don't go near /dev/pf unless we actually intend to use it */ 219 if ((abandoned_tab != NULL) || 220 (changedmac_tab != NULL) || 221 (leased_tab != NULL)){ 222 if (pipe(pfpipe) == -1) 223 fatal("pipe"); 224 switch (pfproc_pid = fork()){ 225 case -1: 226 fatal("fork"); 227 /* NOTREACHED */ 228 exit(1); 229 case 0: 230 /* child process. start up table engine */ 231 close(pfpipe[1]); 232 pftable_handler(); 233 /* NOTREACHED */ 234 exit(1); 235 default: 236 close(pfpipe[0]); 237 gotpipe = 1; 238 break; 239 } 240 } 241 242 if (udpsockmode) 243 udpsock_startup(udpaddr); 244 245 icmp_startup(1, lease_pinged); 246 247 if (chroot(pw->pw_dir) == -1) 248 fatal("chroot %s", pw->pw_dir); 249 if (chdir("/") == -1) 250 fatal("chdir(\"/\")"); 251 if (setgroups(1, &pw->pw_gid) || 252 setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) || 253 setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid)) 254 fatal("can't drop privileges"); 255 256 if (udpsockmode) { 257 if (pledge("stdio inet route sendfd", NULL) == -1) 258 err(1, "pledge"); 259 } else { 260 if (pledge("stdio inet sendfd", NULL) == -1) 261 err(1, "pledge"); 262 } 263 264 add_timeout(cur_time + 5, periodic_scan, NULL); 265 dispatch(); 266 267 /* not reached */ 268 exit(0); 269 } 270 271 __dead void 272 usage(void) 273 { 274 extern char *__progname; 275 276 fprintf(stderr, "usage: %s [-dfn] [-A abandoned_ip_table]", 277 __progname); 278 fprintf(stderr, " [-C changed_ip_table]\n"); 279 fprintf(stderr, "\t[-c config-file] [-L leased_ip_table]"); 280 fprintf(stderr, " [-l lease-file] [-u[bind_address]]\n"); 281 fprintf(stderr, "\t[-Y synctarget] [-y synclisten] [if0 [... ifN]]\n"); 282 exit(1); 283 } 284 285 void 286 lease_pinged(struct iaddr from, u_int8_t *packet, int length) 287 { 288 struct lease *lp; 289 290 /* 291 * Don't try to look up a pinged lease if we aren't trying to 292 * ping one - otherwise somebody could easily make us churn by 293 * just forging repeated ICMP EchoReply packets for us to look 294 * up. 295 */ 296 if (!outstanding_pings) 297 return; 298 299 lp = find_lease_by_ip_addr(from); 300 301 if (!lp) { 302 log_info("unexpected ICMP Echo Reply from %s", piaddr(from)); 303 return; 304 } 305 306 if (!lp->state && !lp->releasing) { 307 log_warnx("ICMP Echo Reply for %s arrived late or is " 308 "spurious.", piaddr(from)); 309 return; 310 } 311 312 /* At this point it looks like we pinged a lease and got a 313 * response, which shouldn't have happened. 314 * if it did it's either one of two two cases: 315 * 1 - we pinged this lease before offering it and 316 * something answered, so we abandon it. 317 * 2 - we pinged this lease before releasing it 318 * and something answered, so we don't release it. 319 */ 320 if (lp->releasing) { 321 log_warnx("IP address %s answers a ping after sending a " 322 "release", piaddr(lp->ip_addr)); 323 log_warnx("Possible release spoof - Not releasing address %s", 324 piaddr(lp->ip_addr)); 325 lp->releasing = 0; 326 } else { 327 free_lease_state(lp->state, "lease_pinged"); 328 lp->state = NULL; 329 abandon_lease(lp, "pinged before offer"); 330 } 331 cancel_timeout(lease_ping_timeout, lp); 332 --outstanding_pings; 333 } 334 335 void 336 lease_ping_timeout(void *vlp) 337 { 338 struct lease *lp = vlp; 339 340 --outstanding_pings; 341 if (lp->releasing) { 342 lp->releasing = 0; 343 release_lease(lp); 344 } else 345 dhcp_reply(lp); 346 } 347 348 /* from memory.c - needed to be able to walk the lease table */ 349 extern struct subnet *subnets; 350 351 #define MINIMUM(a,b) (((a)<(b))?(a):(b)) 352 353 void 354 periodic_scan(void *p) 355 { 356 time_t x, y; 357 struct subnet *n; 358 struct group *g; 359 struct shared_network *s; 360 struct lease *l; 361 362 /* find the shortest lease this server gives out */ 363 x = MINIMUM(root_group.default_lease_time, root_group.max_lease_time); 364 for (n = subnets; n; n = n->next_subnet) 365 for (g = n->group; g; g = g->next) 366 x = MINIMUM(x, g->default_lease_time); 367 368 /* use half of the shortest lease as the scan interval */ 369 y = x / 2; 370 if (y < 1) 371 y = 1; 372 373 /* walk across all leases to find the exired ones */ 374 for (n = subnets; n; n = n->next_subnet) 375 for (g = n->group; g; g = g->next) 376 for (s = g->shared_network; s; s = s->next) 377 for (l = s->leases; l && l->ends; l = l->next) 378 if (cur_time >= l->ends) 379 if (l->ends > last_scan) 380 pfmsg('R', l); 381 382 last_scan = cur_time; 383 add_timeout(cur_time + y, periodic_scan, NULL); 384 } 385