1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1993 5 * The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)ip_icmp.c 8.2 (Berkeley) 1/4/94 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/mbuf.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/time.h> 45 #include <sys/kernel.h> 46 #include <sys/lock.h> 47 #include <sys/sysctl.h> 48 #include <sys/syslog.h> 49 50 #include <net/if.h> 51 #include <net/if_var.h> 52 #include <net/if_types.h> 53 #include <net/route.h> 54 #include <net/route/route_ctl.h> 55 #include <net/route/nhop.h> 56 #include <net/vnet.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_fib.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/in_var.h> 63 #include <netinet/ip.h> 64 #include <netinet/ip_icmp.h> 65 #include <netinet/ip_var.h> 66 #include <netinet/ip_options.h> 67 #include <netinet/sctp.h> 68 #include <netinet/tcp.h> 69 #include <netinet/tcp_var.h> 70 #include <netinet/tcpip.h> 71 #include <netinet/icmp_var.h> 72 73 #ifdef INET 74 75 #include <machine/in_cksum.h> 76 77 #include <security/mac/mac_framework.h> 78 #endif /* INET */ 79 80 /* 81 * ICMP routines: error generation, receive packet processing, and 82 * routines to turnaround packets back to the originator, and 83 * host table maintenance routines. 84 */ 85 VNET_DEFINE_STATIC(int, icmplim) = 200; 86 #define V_icmplim VNET(icmplim) 87 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_VNET | CTLFLAG_RW, 88 &VNET_NAME(icmplim), 0, 89 "Maximum number of ICMP responses per second"); 90 91 VNET_DEFINE_STATIC(int, icmplim_curr_jitter) = 0; 92 #define V_icmplim_curr_jitter VNET(icmplim_curr_jitter) 93 VNET_DEFINE_STATIC(int, icmplim_jitter) = 16; 94 #define V_icmplim_jitter VNET(icmplim_jitter) 95 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_jitter, CTLFLAG_VNET | CTLFLAG_RW, 96 &VNET_NAME(icmplim_jitter), 0, 97 "Random icmplim jitter adjustment limit"); 98 99 VNET_DEFINE_STATIC(int, icmplim_output) = 1; 100 #define V_icmplim_output VNET(icmplim_output) 101 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_VNET | CTLFLAG_RW, 102 &VNET_NAME(icmplim_output), 0, 103 "Enable logging of ICMP response rate limiting"); 104 105 #ifdef INET 106 VNET_PCPUSTAT_DEFINE(struct icmpstat, icmpstat); 107 VNET_PCPUSTAT_SYSINIT(icmpstat); 108 SYSCTL_VNET_PCPUSTAT(_net_inet_icmp, ICMPCTL_STATS, stats, struct icmpstat, 109 icmpstat, "ICMP statistics (struct icmpstat, netinet/icmp_var.h)"); 110 111 #ifdef VIMAGE 112 VNET_PCPUSTAT_SYSUNINIT(icmpstat); 113 #endif /* VIMAGE */ 114 115 VNET_DEFINE_STATIC(int, icmpmaskrepl) = 0; 116 #define V_icmpmaskrepl VNET(icmpmaskrepl) 117 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_VNET | CTLFLAG_RW, 118 &VNET_NAME(icmpmaskrepl), 0, 119 "Reply to ICMP Address Mask Request packets"); 120 121 VNET_DEFINE_STATIC(u_int, icmpmaskfake) = 0; 122 #define V_icmpmaskfake VNET(icmpmaskfake) 123 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_VNET | CTLFLAG_RW, 124 &VNET_NAME(icmpmaskfake), 0, 125 "Fake reply to ICMP Address Mask Request packets"); 126 127 VNET_DEFINE(int, drop_redirect) = 0; 128 #define V_drop_redirect VNET(drop_redirect) 129 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(drop_redirect), 0, 131 "Ignore ICMP redirects"); 132 133 VNET_DEFINE_STATIC(int, log_redirect) = 0; 134 #define V_log_redirect VNET(log_redirect) 135 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_VNET | CTLFLAG_RW, 136 &VNET_NAME(log_redirect), 0, 137 "Log ICMP redirects to the console"); 138 139 VNET_DEFINE_STATIC(int, redirtimeout) = 60 * 10; /* 10 minutes */ 140 #define V_redirtimeout VNET(redirtimeout) 141 SYSCTL_INT(_net_inet_icmp, OID_AUTO, redirtimeout, CTLFLAG_VNET | CTLFLAG_RW, 142 &VNET_NAME(redirtimeout), 0, 143 "Delay in seconds before expiring redirect route"); 144 145 VNET_DEFINE_STATIC(char, reply_src[IFNAMSIZ]); 146 #define V_reply_src VNET(reply_src) 147 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(reply_src), IFNAMSIZ, 149 "ICMP reply source for non-local packets"); 150 151 VNET_DEFINE_STATIC(int, icmp_rfi) = 0; 152 #define V_icmp_rfi VNET(icmp_rfi) 153 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_VNET | CTLFLAG_RW, 154 &VNET_NAME(icmp_rfi), 0, 155 "ICMP reply from incoming interface for non-local packets"); 156 /* Router requirements RFC 1812 section 4.3.2.3 requires 576 - 28. */ 157 VNET_DEFINE_STATIC(int, icmp_quotelen) = 548; 158 #define V_icmp_quotelen VNET(icmp_quotelen) 159 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_VNET | CTLFLAG_RW, 160 &VNET_NAME(icmp_quotelen), 0, 161 "Number of bytes from original packet to quote in ICMP reply"); 162 163 VNET_DEFINE_STATIC(int, icmpbmcastecho) = 0; 164 #define V_icmpbmcastecho VNET(icmpbmcastecho) 165 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_VNET | CTLFLAG_RW, 166 &VNET_NAME(icmpbmcastecho), 0, 167 "Reply to multicast ICMP Echo Request and Timestamp packets"); 168 169 VNET_DEFINE_STATIC(int, icmptstamprepl) = 1; 170 #define V_icmptstamprepl VNET(icmptstamprepl) 171 SYSCTL_INT(_net_inet_icmp, OID_AUTO, tstamprepl, CTLFLAG_VNET | CTLFLAG_RW, 172 &VNET_NAME(icmptstamprepl), 0, 173 "Respond to ICMP Timestamp packets"); 174 175 VNET_DEFINE_STATIC(int, error_keeptags) = 0; 176 #define V_error_keeptags VNET(error_keeptags) 177 SYSCTL_INT(_net_inet_icmp, OID_AUTO, error_keeptags, CTLFLAG_VNET | CTLFLAG_RW, 178 &VNET_NAME(error_keeptags), 0, 179 "ICMP error response keeps copy of mbuf_tags of original packet"); 180 181 #ifdef ICMPPRINTFS 182 int icmpprintfs = 0; 183 #endif 184 185 static void icmp_reflect(struct mbuf *); 186 static void icmp_send(struct mbuf *, struct mbuf *); 187 static int icmp_verify_redirect_gateway(struct sockaddr_in *, 188 struct sockaddr_in *, struct sockaddr_in *, u_int); 189 190 extern struct protosw inetsw[]; 191 192 /* 193 * Kernel module interface for updating icmpstat. The argument is an index 194 * into icmpstat treated as an array of u_long. While this encodes the 195 * general layout of icmpstat into the caller, it doesn't encode its 196 * location, so that future changes to add, for example, per-CPU stats 197 * support won't cause binary compatibility problems for kernel modules. 198 */ 199 void 200 kmod_icmpstat_inc(int statnum) 201 { 202 203 counter_u64_add(VNET(icmpstat)[statnum], 1); 204 } 205 206 /* 207 * Generate an error packet of type error 208 * in response to bad packet ip. 209 */ 210 void 211 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu) 212 { 213 struct ip *oip, *nip; 214 struct icmp *icp; 215 struct mbuf *m; 216 unsigned icmplen, icmpelen, nlen, oiphlen; 217 218 KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type", 219 __func__)); 220 221 if (type != ICMP_REDIRECT) 222 ICMPSTAT_INC(icps_error); 223 /* 224 * Don't send error: 225 * if the original packet was encrypted. 226 * if not the first fragment of message. 227 * in response to a multicast or broadcast packet. 228 * if the old packet protocol was an ICMP error message. 229 */ 230 if (n->m_flags & M_DECRYPTED) 231 goto freeit; 232 if (n->m_flags & (M_BCAST|M_MCAST)) 233 goto freeit; 234 235 /* Drop if IP header plus 8 bytes is not contiguous in first mbuf. */ 236 if (n->m_len < sizeof(struct ip) + ICMP_MINLEN) 237 goto freeit; 238 oip = mtod(n, struct ip *); 239 oiphlen = oip->ip_hl << 2; 240 if (n->m_len < oiphlen + ICMP_MINLEN) 241 goto freeit; 242 #ifdef ICMPPRINTFS 243 if (icmpprintfs) 244 printf("icmp_error(%p, %x, %d)\n", oip, type, code); 245 #endif 246 if (oip->ip_off & htons(~(IP_MF|IP_DF))) 247 goto freeit; 248 if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT && 249 !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + 250 oiphlen))->icmp_type)) { 251 ICMPSTAT_INC(icps_oldicmp); 252 goto freeit; 253 } 254 /* 255 * Calculate length to quote from original packet and 256 * prevent the ICMP mbuf from overflowing. 257 * Unfortunately this is non-trivial since ip_forward() 258 * sends us truncated packets. 259 */ 260 nlen = m_length(n, NULL); 261 if (oip->ip_p == IPPROTO_TCP) { 262 struct tcphdr *th; 263 int tcphlen; 264 265 if (oiphlen + sizeof(struct tcphdr) > n->m_len && 266 n->m_next == NULL) 267 goto stdreply; 268 if (n->m_len < oiphlen + sizeof(struct tcphdr) && 269 (n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL) 270 goto freeit; 271 oip = mtod(n, struct ip *); 272 th = mtodo(n, oiphlen); 273 tcphlen = th->th_off << 2; 274 if (tcphlen < sizeof(struct tcphdr)) 275 goto freeit; 276 if (ntohs(oip->ip_len) < oiphlen + tcphlen) 277 goto freeit; 278 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL) 279 goto stdreply; 280 if (n->m_len < oiphlen + tcphlen && 281 (n = m_pullup(n, oiphlen + tcphlen)) == NULL) 282 goto freeit; 283 oip = mtod(n, struct ip *); 284 icmpelen = max(tcphlen, min(V_icmp_quotelen, 285 ntohs(oip->ip_len) - oiphlen)); 286 } else if (oip->ip_p == IPPROTO_SCTP) { 287 struct sctphdr *sh; 288 struct sctp_chunkhdr *ch; 289 290 if (ntohs(oip->ip_len) < oiphlen + sizeof(struct sctphdr)) 291 goto stdreply; 292 if (oiphlen + sizeof(struct sctphdr) > n->m_len && 293 n->m_next == NULL) 294 goto stdreply; 295 if (n->m_len < oiphlen + sizeof(struct sctphdr) && 296 (n = m_pullup(n, oiphlen + sizeof(struct sctphdr))) == NULL) 297 goto freeit; 298 oip = mtod(n, struct ip *); 299 icmpelen = max(sizeof(struct sctphdr), 300 min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen)); 301 sh = mtodo(n, oiphlen); 302 if (ntohl(sh->v_tag) == 0 && 303 ntohs(oip->ip_len) >= oiphlen + 304 sizeof(struct sctphdr) + 8 && 305 (n->m_len >= oiphlen + sizeof(struct sctphdr) + 8 || 306 n->m_next != NULL)) { 307 if (n->m_len < oiphlen + sizeof(struct sctphdr) + 8 && 308 (n = m_pullup(n, oiphlen + 309 sizeof(struct sctphdr) + 8)) == NULL) 310 goto freeit; 311 oip = mtod(n, struct ip *); 312 sh = mtodo(n, oiphlen); 313 ch = (struct sctp_chunkhdr *)(sh + 1); 314 if (ch->chunk_type == SCTP_INITIATION) { 315 icmpelen = max(sizeof(struct sctphdr) + 8, 316 min(V_icmp_quotelen, ntohs(oip->ip_len) - 317 oiphlen)); 318 } 319 } 320 } else 321 stdreply: icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) - 322 oiphlen)); 323 324 icmplen = min(oiphlen + icmpelen, nlen); 325 if (icmplen < sizeof(struct ip)) 326 goto freeit; 327 328 if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen) 329 m = m_gethdr(M_NOWAIT, MT_DATA); 330 else 331 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 332 if (m == NULL) 333 goto freeit; 334 #ifdef MAC 335 mac_netinet_icmp_reply(n, m); 336 #endif 337 icmplen = min(icmplen, M_TRAILINGSPACE(m) - 338 sizeof(struct ip) - ICMP_MINLEN); 339 m_align(m, sizeof(struct ip) + ICMP_MINLEN + icmplen); 340 m->m_data += sizeof(struct ip); 341 m->m_len = ICMP_MINLEN + icmplen; 342 343 /* XXX MRT make the outgoing packet use the same FIB 344 * that was associated with the incoming packet 345 */ 346 M_SETFIB(m, M_GETFIB(n)); 347 icp = mtod(m, struct icmp *); 348 ICMPSTAT_INC(icps_outhist[type]); 349 icp->icmp_type = type; 350 if (type == ICMP_REDIRECT) 351 icp->icmp_gwaddr.s_addr = dest; 352 else { 353 icp->icmp_void = 0; 354 /* 355 * The following assignments assume an overlay with the 356 * just zeroed icmp_void field. 357 */ 358 if (type == ICMP_PARAMPROB) { 359 icp->icmp_pptr = code; 360 code = 0; 361 } else if (type == ICMP_UNREACH && 362 code == ICMP_UNREACH_NEEDFRAG && mtu) { 363 icp->icmp_nextmtu = htons(mtu); 364 } 365 } 366 icp->icmp_code = code; 367 368 /* 369 * Copy the quotation into ICMP message and 370 * convert quoted IP header back to network representation. 371 */ 372 m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip); 373 nip = &icp->icmp_ip; 374 375 /* 376 * Set up ICMP message mbuf and copy old IP header (without options 377 * in front of ICMP message. 378 * If the original mbuf was meant to bypass the firewall, the error 379 * reply should bypass as well. 380 */ 381 m->m_flags |= n->m_flags & M_SKIP_FIREWALL; 382 KASSERT(M_LEADINGSPACE(m) >= sizeof(struct ip), 383 ("insufficient space for ip header")); 384 m->m_data -= sizeof(struct ip); 385 m->m_len += sizeof(struct ip); 386 m->m_pkthdr.len = m->m_len; 387 m->m_pkthdr.rcvif = n->m_pkthdr.rcvif; 388 nip = mtod(m, struct ip *); 389 bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip)); 390 nip->ip_len = htons(m->m_len); 391 nip->ip_v = IPVERSION; 392 nip->ip_hl = 5; 393 nip->ip_p = IPPROTO_ICMP; 394 nip->ip_tos = 0; 395 nip->ip_off = 0; 396 397 if (V_error_keeptags) 398 m_tag_copy_chain(m, n, M_NOWAIT); 399 400 icmp_reflect(m); 401 402 freeit: 403 m_freem(n); 404 } 405 406 /* 407 * Process a received ICMP message. 408 */ 409 int 410 icmp_input(struct mbuf **mp, int *offp, int proto) 411 { 412 struct icmp *icp; 413 struct in_ifaddr *ia; 414 struct mbuf *m = *mp; 415 struct ip *ip = mtod(m, struct ip *); 416 struct sockaddr_in icmpsrc, icmpdst, icmpgw; 417 int hlen = *offp; 418 int icmplen = ntohs(ip->ip_len) - *offp; 419 int i, code; 420 void (*ctlfunc)(int, struct sockaddr *, void *); 421 int fibnum; 422 423 NET_EPOCH_ASSERT(); 424 425 *mp = NULL; 426 427 /* 428 * Locate icmp structure in mbuf, and check 429 * that not corrupted and of at least minimum length. 430 */ 431 #ifdef ICMPPRINTFS 432 if (icmpprintfs) { 433 char srcbuf[INET_ADDRSTRLEN]; 434 char dstbuf[INET_ADDRSTRLEN]; 435 436 printf("icmp_input from %s to %s, len %d\n", 437 inet_ntoa_r(ip->ip_src, srcbuf), 438 inet_ntoa_r(ip->ip_dst, dstbuf), icmplen); 439 } 440 #endif 441 if (icmplen < ICMP_MINLEN) { 442 ICMPSTAT_INC(icps_tooshort); 443 goto freeit; 444 } 445 i = hlen + min(icmplen, ICMP_ADVLENMIN); 446 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) { 447 ICMPSTAT_INC(icps_tooshort); 448 return (IPPROTO_DONE); 449 } 450 ip = mtod(m, struct ip *); 451 m->m_len -= hlen; 452 m->m_data += hlen; 453 icp = mtod(m, struct icmp *); 454 if (in_cksum(m, icmplen)) { 455 ICMPSTAT_INC(icps_checksum); 456 goto freeit; 457 } 458 m->m_len += hlen; 459 m->m_data -= hlen; 460 461 #ifdef ICMPPRINTFS 462 if (icmpprintfs) 463 printf("icmp_input, type %d code %d\n", icp->icmp_type, 464 icp->icmp_code); 465 #endif 466 467 /* 468 * Message type specific processing. 469 */ 470 if (icp->icmp_type > ICMP_MAXTYPE) 471 goto raw; 472 473 /* Initialize */ 474 bzero(&icmpsrc, sizeof(icmpsrc)); 475 icmpsrc.sin_len = sizeof(struct sockaddr_in); 476 icmpsrc.sin_family = AF_INET; 477 bzero(&icmpdst, sizeof(icmpdst)); 478 icmpdst.sin_len = sizeof(struct sockaddr_in); 479 icmpdst.sin_family = AF_INET; 480 bzero(&icmpgw, sizeof(icmpgw)); 481 icmpgw.sin_len = sizeof(struct sockaddr_in); 482 icmpgw.sin_family = AF_INET; 483 484 ICMPSTAT_INC(icps_inhist[icp->icmp_type]); 485 code = icp->icmp_code; 486 switch (icp->icmp_type) { 487 case ICMP_UNREACH: 488 switch (code) { 489 case ICMP_UNREACH_NET: 490 case ICMP_UNREACH_HOST: 491 case ICMP_UNREACH_SRCFAIL: 492 case ICMP_UNREACH_NET_UNKNOWN: 493 case ICMP_UNREACH_HOST_UNKNOWN: 494 case ICMP_UNREACH_ISOLATED: 495 case ICMP_UNREACH_TOSNET: 496 case ICMP_UNREACH_TOSHOST: 497 case ICMP_UNREACH_HOST_PRECEDENCE: 498 case ICMP_UNREACH_PRECEDENCE_CUTOFF: 499 code = PRC_UNREACH_NET; 500 break; 501 502 case ICMP_UNREACH_NEEDFRAG: 503 code = PRC_MSGSIZE; 504 break; 505 506 /* 507 * RFC 1122, Sections 3.2.2.1 and 4.2.3.9. 508 * Treat subcodes 2,3 as immediate RST 509 */ 510 case ICMP_UNREACH_PROTOCOL: 511 code = PRC_UNREACH_PROTOCOL; 512 break; 513 case ICMP_UNREACH_PORT: 514 code = PRC_UNREACH_PORT; 515 break; 516 517 case ICMP_UNREACH_NET_PROHIB: 518 case ICMP_UNREACH_HOST_PROHIB: 519 case ICMP_UNREACH_FILTER_PROHIB: 520 code = PRC_UNREACH_ADMIN_PROHIB; 521 break; 522 523 default: 524 goto badcode; 525 } 526 goto deliver; 527 528 case ICMP_TIMXCEED: 529 if (code > 1) 530 goto badcode; 531 code += PRC_TIMXCEED_INTRANS; 532 goto deliver; 533 534 case ICMP_PARAMPROB: 535 if (code > 1) 536 goto badcode; 537 code = PRC_PARAMPROB; 538 deliver: 539 /* 540 * Problem with datagram; advise higher level routines. 541 */ 542 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) || 543 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) { 544 ICMPSTAT_INC(icps_badlen); 545 goto freeit; 546 } 547 /* Discard ICMP's in response to multicast packets */ 548 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr))) 549 goto badcode; 550 #ifdef ICMPPRINTFS 551 if (icmpprintfs) 552 printf("deliver to protocol %d\n", icp->icmp_ip.ip_p); 553 #endif 554 icmpsrc.sin_addr = icp->icmp_ip.ip_dst; 555 /* 556 * XXX if the packet contains [IPv4 AH TCP], we can't make a 557 * notification to TCP layer. 558 */ 559 i = sizeof(struct ip) + min(icmplen, ICMP_ADVLENPREF(icp)); 560 ip_stripoptions(m); 561 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) { 562 /* This should actually not happen */ 563 ICMPSTAT_INC(icps_tooshort); 564 return (IPPROTO_DONE); 565 } 566 ip = mtod(m, struct ip *); 567 icp = (struct icmp *)(ip + 1); 568 /* 569 * The upper layer handler can rely on: 570 * - The outer IP header has no options. 571 * - The outer IP header, the ICMP header, the inner IP header, 572 * and the first n bytes of the inner payload are contiguous. 573 * n is at least 8, but might be larger based on 574 * ICMP_ADVLENPREF. See its definition in ip_icmp.h. 575 */ 576 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput; 577 if (ctlfunc) 578 (*ctlfunc)(code, (struct sockaddr *)&icmpsrc, 579 (void *)&icp->icmp_ip); 580 break; 581 582 badcode: 583 ICMPSTAT_INC(icps_badcode); 584 break; 585 586 case ICMP_ECHO: 587 if (!V_icmpbmcastecho 588 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { 589 ICMPSTAT_INC(icps_bmcastecho); 590 break; 591 } 592 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0) 593 goto freeit; 594 icp->icmp_type = ICMP_ECHOREPLY; 595 goto reflect; 596 597 case ICMP_TSTAMP: 598 if (V_icmptstamprepl == 0) 599 break; 600 if (!V_icmpbmcastecho 601 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { 602 ICMPSTAT_INC(icps_bmcasttstamp); 603 break; 604 } 605 if (icmplen < ICMP_TSLEN) { 606 ICMPSTAT_INC(icps_badlen); 607 break; 608 } 609 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0) 610 goto freeit; 611 icp->icmp_type = ICMP_TSTAMPREPLY; 612 icp->icmp_rtime = iptime(); 613 icp->icmp_ttime = icp->icmp_rtime; /* bogus, do later! */ 614 goto reflect; 615 616 case ICMP_MASKREQ: 617 if (V_icmpmaskrepl == 0) 618 break; 619 /* 620 * We are not able to respond with all ones broadcast 621 * unless we receive it over a point-to-point interface. 622 */ 623 if (icmplen < ICMP_MASKLEN) 624 break; 625 switch (ip->ip_dst.s_addr) { 626 case INADDR_BROADCAST: 627 case INADDR_ANY: 628 icmpdst.sin_addr = ip->ip_src; 629 break; 630 631 default: 632 icmpdst.sin_addr = ip->ip_dst; 633 } 634 ia = (struct in_ifaddr *)ifaof_ifpforaddr( 635 (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif); 636 if (ia == NULL) 637 break; 638 if (ia->ia_ifp == NULL) 639 break; 640 icp->icmp_type = ICMP_MASKREPLY; 641 if (V_icmpmaskfake == 0) 642 icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr; 643 else 644 icp->icmp_mask = V_icmpmaskfake; 645 if (ip->ip_src.s_addr == 0) { 646 if (ia->ia_ifp->if_flags & IFF_BROADCAST) 647 ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr; 648 else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT) 649 ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr; 650 } 651 reflect: 652 ICMPSTAT_INC(icps_reflect); 653 ICMPSTAT_INC(icps_outhist[icp->icmp_type]); 654 icmp_reflect(m); 655 return (IPPROTO_DONE); 656 657 case ICMP_REDIRECT: 658 if (V_log_redirect) { 659 u_long src, dst, gw; 660 661 src = ntohl(ip->ip_src.s_addr); 662 dst = ntohl(icp->icmp_ip.ip_dst.s_addr); 663 gw = ntohl(icp->icmp_gwaddr.s_addr); 664 printf("icmp redirect from %d.%d.%d.%d: " 665 "%d.%d.%d.%d => %d.%d.%d.%d\n", 666 (int)(src >> 24), (int)((src >> 16) & 0xff), 667 (int)((src >> 8) & 0xff), (int)(src & 0xff), 668 (int)(dst >> 24), (int)((dst >> 16) & 0xff), 669 (int)((dst >> 8) & 0xff), (int)(dst & 0xff), 670 (int)(gw >> 24), (int)((gw >> 16) & 0xff), 671 (int)((gw >> 8) & 0xff), (int)(gw & 0xff)); 672 } 673 /* 674 * RFC1812 says we must ignore ICMP redirects if we 675 * are acting as router. 676 */ 677 if (V_drop_redirect || V_ipforwarding) 678 break; 679 if (code > 3) 680 goto badcode; 681 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) || 682 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) { 683 ICMPSTAT_INC(icps_badlen); 684 break; 685 } 686 /* 687 * Short circuit routing redirects to force 688 * immediate change in the kernel's routing 689 * tables. The message is also handed to anyone 690 * listening on a raw socket (e.g. the routing 691 * daemon for use in updating its tables). 692 */ 693 icmpgw.sin_addr = ip->ip_src; 694 icmpdst.sin_addr = icp->icmp_gwaddr; 695 #ifdef ICMPPRINTFS 696 if (icmpprintfs) { 697 char dstbuf[INET_ADDRSTRLEN]; 698 char gwbuf[INET_ADDRSTRLEN]; 699 700 printf("redirect dst %s to %s\n", 701 inet_ntoa_r(icp->icmp_ip.ip_dst, dstbuf), 702 inet_ntoa_r(icp->icmp_gwaddr, gwbuf)); 703 } 704 #endif 705 icmpsrc.sin_addr = icp->icmp_ip.ip_dst; 706 707 /* 708 * RFC 1122 says network (code 0,2) redirects SHOULD 709 * be treated identically to the host redirects. 710 * Given that, ignore network masks. 711 */ 712 713 /* 714 * Variable values: 715 * icmpsrc: route destination 716 * icmpdst: route gateway 717 * icmpgw: message source 718 */ 719 720 if (icmp_verify_redirect_gateway(&icmpgw, &icmpsrc, &icmpdst, 721 M_GETFIB(m)) != 0) { 722 /* TODO: increment bad redirects here */ 723 break; 724 } 725 726 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) { 727 rib_add_redirect(fibnum, (struct sockaddr *)&icmpsrc, 728 (struct sockaddr *)&icmpdst, 729 (struct sockaddr *)&icmpgw, m->m_pkthdr.rcvif, 730 RTF_GATEWAY, V_redirtimeout); 731 } 732 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc); 733 break; 734 735 /* 736 * No kernel processing for the following; 737 * just fall through to send to raw listener. 738 */ 739 case ICMP_ECHOREPLY: 740 case ICMP_ROUTERADVERT: 741 case ICMP_ROUTERSOLICIT: 742 case ICMP_TSTAMPREPLY: 743 case ICMP_IREQREPLY: 744 case ICMP_MASKREPLY: 745 case ICMP_SOURCEQUENCH: 746 default: 747 break; 748 } 749 750 raw: 751 *mp = m; 752 rip_input(mp, offp, proto); 753 return (IPPROTO_DONE); 754 755 freeit: 756 m_freem(m); 757 return (IPPROTO_DONE); 758 } 759 760 /* 761 * Reflect the ip packet back to the source 762 */ 763 static void 764 icmp_reflect(struct mbuf *m) 765 { 766 struct ip *ip = mtod(m, struct ip *); 767 struct ifaddr *ifa; 768 struct ifnet *ifp; 769 struct in_ifaddr *ia; 770 struct in_addr t; 771 struct nhop_object *nh; 772 struct mbuf *opts = NULL; 773 int optlen = (ip->ip_hl << 2) - sizeof(struct ip); 774 775 NET_EPOCH_ASSERT(); 776 777 if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 778 IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) || 779 IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) { 780 m_freem(m); /* Bad return address */ 781 ICMPSTAT_INC(icps_badaddr); 782 goto done; /* Ip_output() will check for broadcast */ 783 } 784 785 t = ip->ip_dst; 786 ip->ip_dst = ip->ip_src; 787 788 /* 789 * Source selection for ICMP replies: 790 * 791 * If the incoming packet was addressed directly to one of our 792 * own addresses, use dst as the src for the reply. 793 */ 794 CK_LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) { 795 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) { 796 t = IA_SIN(ia)->sin_addr; 797 goto match; 798 } 799 } 800 801 /* 802 * If the incoming packet was addressed to one of our broadcast 803 * addresses, use the first non-broadcast address which corresponds 804 * to the incoming interface. 805 */ 806 ifp = m->m_pkthdr.rcvif; 807 if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) { 808 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 809 if (ifa->ifa_addr->sa_family != AF_INET) 810 continue; 811 ia = ifatoia(ifa); 812 if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr == 813 t.s_addr) { 814 t = IA_SIN(ia)->sin_addr; 815 goto match; 816 } 817 } 818 } 819 /* 820 * If the packet was transiting through us, use the address of 821 * the interface the packet came through in. If that interface 822 * doesn't have a suitable IP address, the normal selection 823 * criteria apply. 824 */ 825 if (V_icmp_rfi && ifp != NULL) { 826 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 827 if (ifa->ifa_addr->sa_family != AF_INET) 828 continue; 829 ia = ifatoia(ifa); 830 t = IA_SIN(ia)->sin_addr; 831 goto match; 832 } 833 } 834 /* 835 * If the incoming packet was not addressed directly to us, use 836 * designated interface for icmp replies specified by sysctl 837 * net.inet.icmp.reply_src (default not set). Otherwise continue 838 * with normal source selection. 839 */ 840 if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) { 841 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 842 if (ifa->ifa_addr->sa_family != AF_INET) 843 continue; 844 ia = ifatoia(ifa); 845 t = IA_SIN(ia)->sin_addr; 846 goto match; 847 } 848 } 849 /* 850 * If the packet was transiting through us, use the address of 851 * the interface that is the closest to the packet source. 852 * When we don't have a route back to the packet source, stop here 853 * and drop the packet. 854 */ 855 nh = fib4_lookup(M_GETFIB(m), ip->ip_dst, 0, NHR_NONE, 0); 856 if (nh == NULL) { 857 m_freem(m); 858 ICMPSTAT_INC(icps_noroute); 859 goto done; 860 } 861 t = IA_SIN(ifatoia(nh->nh_ifa))->sin_addr; 862 match: 863 #ifdef MAC 864 mac_netinet_icmp_replyinplace(m); 865 #endif 866 ip->ip_src = t; 867 ip->ip_ttl = V_ip_defttl; 868 869 if (optlen > 0) { 870 u_char *cp; 871 int opt, cnt; 872 u_int len; 873 874 /* 875 * Retrieve any source routing from the incoming packet; 876 * add on any record-route or timestamp options. 877 */ 878 cp = (u_char *) (ip + 1); 879 if ((opts = ip_srcroute(m)) == NULL && 880 (opts = m_gethdr(M_NOWAIT, MT_DATA))) { 881 opts->m_len = sizeof(struct in_addr); 882 mtod(opts, struct in_addr *)->s_addr = 0; 883 } 884 if (opts) { 885 #ifdef ICMPPRINTFS 886 if (icmpprintfs) 887 printf("icmp_reflect optlen %d rt %d => ", 888 optlen, opts->m_len); 889 #endif 890 for (cnt = optlen; cnt > 0; cnt -= len, cp += len) { 891 opt = cp[IPOPT_OPTVAL]; 892 if (opt == IPOPT_EOL) 893 break; 894 if (opt == IPOPT_NOP) 895 len = 1; 896 else { 897 if (cnt < IPOPT_OLEN + sizeof(*cp)) 898 break; 899 len = cp[IPOPT_OLEN]; 900 if (len < IPOPT_OLEN + sizeof(*cp) || 901 len > cnt) 902 break; 903 } 904 /* 905 * Should check for overflow, but it "can't happen" 906 */ 907 if (opt == IPOPT_RR || opt == IPOPT_TS || 908 opt == IPOPT_SECURITY) { 909 bcopy((caddr_t)cp, 910 mtod(opts, caddr_t) + opts->m_len, len); 911 opts->m_len += len; 912 } 913 } 914 /* Terminate & pad, if necessary */ 915 cnt = opts->m_len % 4; 916 if (cnt) { 917 for (; cnt < 4; cnt++) { 918 *(mtod(opts, caddr_t) + opts->m_len) = 919 IPOPT_EOL; 920 opts->m_len++; 921 } 922 } 923 #ifdef ICMPPRINTFS 924 if (icmpprintfs) 925 printf("%d\n", opts->m_len); 926 #endif 927 } 928 ip_stripoptions(m); 929 } 930 m_tag_delete_nonpersistent(m); 931 m->m_flags &= ~(M_BCAST|M_MCAST); 932 icmp_send(m, opts); 933 done: 934 if (opts) 935 (void)m_free(opts); 936 } 937 938 /* 939 * Verifies if redirect message is valid, according to RFC 1122 940 * 941 * @src: sockaddr with address of redirect originator 942 * @dst: sockaddr with destination in question 943 * @gateway: new proposed gateway 944 * 945 * Returns 0 on success. 946 */ 947 static int 948 icmp_verify_redirect_gateway(struct sockaddr_in *src, struct sockaddr_in *dst, 949 struct sockaddr_in *gateway, u_int fibnum) 950 { 951 struct nhop_object *nh; 952 struct ifaddr *ifa; 953 954 NET_EPOCH_ASSERT(); 955 956 /* Verify the gateway is directly reachable. */ 957 if ((ifa = ifa_ifwithnet((struct sockaddr *)gateway, 0, fibnum))==NULL) 958 return (ENETUNREACH); 959 960 /* TODO: fib-aware. */ 961 if (ifa_ifwithaddr_check((struct sockaddr *)gateway)) 962 return (EHOSTUNREACH); 963 964 nh = fib4_lookup(fibnum, dst->sin_addr, 0, NHR_NONE, 0); 965 if (nh == NULL) 966 return (EINVAL); 967 968 /* 969 * If the redirect isn't from our current router for this dst, 970 * it's either old or wrong. If it redirects us to ourselves, 971 * we have a routing loop, perhaps as a result of an interface 972 * going down recently. 973 */ 974 if (!sa_equal((struct sockaddr *)src, &nh->gw_sa)) 975 return (EINVAL); 976 if (nh->nh_ifa != ifa && ifa->ifa_addr->sa_family != AF_LINK) 977 return (EINVAL); 978 979 /* If host route already exists, ignore redirect. */ 980 if (nh->nh_flags & NHF_HOST) 981 return (EEXIST); 982 983 /* If the prefix is directly reachable, ignore redirect. */ 984 if (!(nh->nh_flags & NHF_GATEWAY)) 985 return (EEXIST); 986 987 return (0); 988 } 989 990 /* 991 * Send an icmp packet back to the ip level, 992 * after supplying a checksum. 993 */ 994 static void 995 icmp_send(struct mbuf *m, struct mbuf *opts) 996 { 997 struct ip *ip = mtod(m, struct ip *); 998 int hlen; 999 struct icmp *icp; 1000 1001 hlen = ip->ip_hl << 2; 1002 m->m_data += hlen; 1003 m->m_len -= hlen; 1004 icp = mtod(m, struct icmp *); 1005 icp->icmp_cksum = 0; 1006 icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen); 1007 m->m_data -= hlen; 1008 m->m_len += hlen; 1009 m->m_pkthdr.rcvif = (struct ifnet *)0; 1010 #ifdef ICMPPRINTFS 1011 if (icmpprintfs) { 1012 char dstbuf[INET_ADDRSTRLEN]; 1013 char srcbuf[INET_ADDRSTRLEN]; 1014 1015 printf("icmp_send dst %s src %s\n", 1016 inet_ntoa_r(ip->ip_dst, dstbuf), 1017 inet_ntoa_r(ip->ip_src, srcbuf)); 1018 } 1019 #endif 1020 (void) ip_output(m, opts, NULL, 0, NULL, NULL); 1021 } 1022 1023 /* 1024 * Return milliseconds since 00:00 UTC in network format. 1025 */ 1026 uint32_t 1027 iptime(void) 1028 { 1029 struct timeval atv; 1030 u_long t; 1031 1032 getmicrotime(&atv); 1033 t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000; 1034 return (htonl(t)); 1035 } 1036 1037 /* 1038 * Return the next larger or smaller MTU plateau (table from RFC 1191) 1039 * given current value MTU. If DIR is less than zero, a larger plateau 1040 * is returned; otherwise, a smaller value is returned. 1041 */ 1042 int 1043 ip_next_mtu(int mtu, int dir) 1044 { 1045 static int mtutab[] = { 1046 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508, 1047 296, 68, 0 1048 }; 1049 int i, size; 1050 1051 size = (sizeof mtutab) / (sizeof mtutab[0]); 1052 if (dir >= 0) { 1053 for (i = 0; i < size; i++) 1054 if (mtu > mtutab[i]) 1055 return mtutab[i]; 1056 } else { 1057 for (i = size - 1; i >= 0; i--) 1058 if (mtu < mtutab[i]) 1059 return mtutab[i]; 1060 if (mtu == mtutab[0]) 1061 return mtutab[0]; 1062 } 1063 return 0; 1064 } 1065 #endif /* INET */ 1066 1067 /* 1068 * badport_bandlim() - check for ICMP bandwidth limit 1069 * 1070 * Return 0 if it is ok to send an ICMP error response, -1 if we have 1071 * hit our bandwidth limit and it is not ok. 1072 * 1073 * If icmplim is <= 0, the feature is disabled and 0 is returned. 1074 * 1075 * For now we separate the TCP and UDP subsystems w/ different 'which' 1076 * values. We may eventually remove this separation (and simplify the 1077 * code further). 1078 * 1079 * Note that the printing of the error message is delayed so we can 1080 * properly print the icmp error rate that the system was trying to do 1081 * (i.e. 22000/100 pps, etc...). This can cause long delays in printing 1082 * the 'final' error, but it doesn't make sense to solve the printing 1083 * delay with more complex code. 1084 */ 1085 struct icmp_rate { 1086 const char *descr; 1087 struct counter_rate cr; 1088 }; 1089 VNET_DEFINE_STATIC(struct icmp_rate, icmp_rates[BANDLIM_MAX]) = { 1090 { "icmp unreach response" }, 1091 { "icmp ping response" }, 1092 { "icmp tstamp response" }, 1093 { "closed port RST response" }, 1094 { "open port RST response" }, 1095 { "icmp6 unreach response" }, 1096 { "sctp ootb response" } 1097 }; 1098 #define V_icmp_rates VNET(icmp_rates) 1099 1100 static void 1101 icmp_bandlimit_init(void) 1102 { 1103 1104 for (int i = 0; i < BANDLIM_MAX; i++) { 1105 V_icmp_rates[i].cr.cr_rate = counter_u64_alloc(M_WAITOK); 1106 V_icmp_rates[i].cr.cr_ticks = ticks; 1107 } 1108 } 1109 VNET_SYSINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY, 1110 icmp_bandlimit_init, NULL); 1111 1112 static void 1113 icmp_bandlimit_uninit(void) 1114 { 1115 1116 for (int i = 0; i < BANDLIM_MAX; i++) 1117 counter_u64_free(V_icmp_rates[i].cr.cr_rate); 1118 } 1119 VNET_SYSUNINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD, 1120 icmp_bandlimit_uninit, NULL); 1121 1122 int 1123 badport_bandlim(int which) 1124 { 1125 int64_t pps; 1126 1127 if (V_icmplim == 0 || which == BANDLIM_UNLIMITED) 1128 return (0); 1129 1130 KASSERT(which >= 0 && which < BANDLIM_MAX, 1131 ("%s: which %d", __func__, which)); 1132 1133 if ((V_icmplim + V_icmplim_curr_jitter) <= 0) 1134 V_icmplim_curr_jitter = -V_icmplim + 1; 1135 1136 pps = counter_ratecheck(&V_icmp_rates[which].cr, V_icmplim + 1137 V_icmplim_curr_jitter); 1138 if (pps > 0) { 1139 /* 1140 * Adjust limit +/- to jitter the measurement to deny a 1141 * side-channel port scan as in CVE-2020-25705 1142 */ 1143 if (V_icmplim_jitter > 0) { 1144 int32_t inc = 1145 arc4random_uniform(V_icmplim_jitter * 2 +1) 1146 - V_icmplim_jitter; 1147 1148 V_icmplim_curr_jitter = inc; 1149 } 1150 } 1151 if (pps == -1) 1152 return (-1); 1153 if (pps > 0 && V_icmplim_output) 1154 log(LOG_NOTICE, "Limiting %s from %jd to %d packets/sec\n", 1155 V_icmp_rates[which].descr, (intmax_t )pps, V_icmplim + 1156 V_icmplim_curr_jitter); 1157 return (0); 1158 } 1159