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 extern ipproto_ctlinput_t *ip_ctlprotox[]; 81 82 /* 83 * ICMP routines: error generation, receive packet processing, and 84 * routines to turnaround packets back to the originator, and 85 * host table maintenance routines. 86 */ 87 VNET_DEFINE_STATIC(int, icmplim) = 200; 88 #define V_icmplim VNET(icmplim) 89 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_VNET | CTLFLAG_RW, 90 &VNET_NAME(icmplim), 0, 91 "Maximum number of ICMP responses per second"); 92 93 VNET_DEFINE_STATIC(int, icmplim_curr_jitter) = 0; 94 #define V_icmplim_curr_jitter VNET(icmplim_curr_jitter) 95 VNET_DEFINE_STATIC(int, icmplim_jitter) = 16; 96 #define V_icmplim_jitter VNET(icmplim_jitter) 97 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_jitter, CTLFLAG_VNET | CTLFLAG_RW, 98 &VNET_NAME(icmplim_jitter), 0, 99 "Random icmplim jitter adjustment limit"); 100 101 VNET_DEFINE_STATIC(int, icmplim_output) = 1; 102 #define V_icmplim_output VNET(icmplim_output) 103 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_VNET | CTLFLAG_RW, 104 &VNET_NAME(icmplim_output), 0, 105 "Enable logging of ICMP response rate limiting"); 106 107 #ifdef INET 108 VNET_PCPUSTAT_DEFINE(struct icmpstat, icmpstat); 109 VNET_PCPUSTAT_SYSINIT(icmpstat); 110 SYSCTL_VNET_PCPUSTAT(_net_inet_icmp, ICMPCTL_STATS, stats, struct icmpstat, 111 icmpstat, "ICMP statistics (struct icmpstat, netinet/icmp_var.h)"); 112 113 #ifdef VIMAGE 114 VNET_PCPUSTAT_SYSUNINIT(icmpstat); 115 #endif /* VIMAGE */ 116 117 VNET_DEFINE_STATIC(int, icmpmaskrepl) = 0; 118 #define V_icmpmaskrepl VNET(icmpmaskrepl) 119 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_VNET | CTLFLAG_RW, 120 &VNET_NAME(icmpmaskrepl), 0, 121 "Reply to ICMP Address Mask Request packets"); 122 123 VNET_DEFINE_STATIC(u_int, icmpmaskfake) = 0; 124 #define V_icmpmaskfake VNET(icmpmaskfake) 125 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_VNET | CTLFLAG_RW, 126 &VNET_NAME(icmpmaskfake), 0, 127 "Fake reply to ICMP Address Mask Request packets"); 128 129 VNET_DEFINE(int, drop_redirect) = 0; 130 #define V_drop_redirect VNET(drop_redirect) 131 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_VNET | CTLFLAG_RW, 132 &VNET_NAME(drop_redirect), 0, 133 "Ignore ICMP redirects"); 134 135 VNET_DEFINE_STATIC(int, log_redirect) = 0; 136 #define V_log_redirect VNET(log_redirect) 137 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_VNET | CTLFLAG_RW, 138 &VNET_NAME(log_redirect), 0, 139 "Log ICMP redirects to the console"); 140 141 VNET_DEFINE_STATIC(int, redirtimeout) = 60 * 10; /* 10 minutes */ 142 #define V_redirtimeout VNET(redirtimeout) 143 SYSCTL_INT(_net_inet_icmp, OID_AUTO, redirtimeout, CTLFLAG_VNET | CTLFLAG_RW, 144 &VNET_NAME(redirtimeout), 0, 145 "Delay in seconds before expiring redirect route"); 146 147 VNET_DEFINE_STATIC(char, reply_src[IFNAMSIZ]); 148 #define V_reply_src VNET(reply_src) 149 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_VNET | CTLFLAG_RW, 150 &VNET_NAME(reply_src), IFNAMSIZ, 151 "ICMP reply source for non-local packets"); 152 153 VNET_DEFINE_STATIC(int, icmp_rfi) = 0; 154 #define V_icmp_rfi VNET(icmp_rfi) 155 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_VNET | CTLFLAG_RW, 156 &VNET_NAME(icmp_rfi), 0, 157 "ICMP reply from incoming interface for non-local packets"); 158 /* Router requirements RFC 1812 section 4.3.2.3 requires 576 - 28. */ 159 VNET_DEFINE_STATIC(int, icmp_quotelen) = 548; 160 #define V_icmp_quotelen VNET(icmp_quotelen) 161 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_VNET | CTLFLAG_RW, 162 &VNET_NAME(icmp_quotelen), 0, 163 "Number of bytes from original packet to quote in ICMP reply"); 164 165 VNET_DEFINE_STATIC(int, icmpbmcastecho) = 0; 166 #define V_icmpbmcastecho VNET(icmpbmcastecho) 167 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(icmpbmcastecho), 0, 169 "Reply to multicast ICMP Echo Request and Timestamp packets"); 170 171 VNET_DEFINE_STATIC(int, icmptstamprepl) = 1; 172 #define V_icmptstamprepl VNET(icmptstamprepl) 173 SYSCTL_INT(_net_inet_icmp, OID_AUTO, tstamprepl, CTLFLAG_VNET | CTLFLAG_RW, 174 &VNET_NAME(icmptstamprepl), 0, 175 "Respond to ICMP Timestamp packets"); 176 177 VNET_DEFINE_STATIC(int, error_keeptags) = 0; 178 #define V_error_keeptags VNET(error_keeptags) 179 SYSCTL_INT(_net_inet_icmp, OID_AUTO, error_keeptags, CTLFLAG_VNET | CTLFLAG_RW, 180 &VNET_NAME(error_keeptags), 0, 181 "ICMP error response keeps copy of mbuf_tags of original packet"); 182 183 #ifdef ICMPPRINTFS 184 int icmpprintfs = 0; 185 #endif 186 187 static void icmp_reflect(struct mbuf *); 188 static void icmp_send(struct mbuf *, struct mbuf *); 189 static int icmp_verify_redirect_gateway(struct sockaddr_in *, 190 struct sockaddr_in *, struct sockaddr_in *, u_int); 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 int fibnum; 421 422 NET_EPOCH_ASSERT(); 423 424 *mp = NULL; 425 426 /* 427 * Locate icmp structure in mbuf, and check 428 * that not corrupted and of at least minimum length. 429 */ 430 #ifdef ICMPPRINTFS 431 if (icmpprintfs) { 432 char srcbuf[INET_ADDRSTRLEN]; 433 char dstbuf[INET_ADDRSTRLEN]; 434 435 printf("icmp_input from %s to %s, len %d\n", 436 inet_ntoa_r(ip->ip_src, srcbuf), 437 inet_ntoa_r(ip->ip_dst, dstbuf), icmplen); 438 } 439 #endif 440 if (icmplen < ICMP_MINLEN) { 441 ICMPSTAT_INC(icps_tooshort); 442 goto freeit; 443 } 444 i = hlen + min(icmplen, ICMP_ADVLENMIN); 445 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) { 446 ICMPSTAT_INC(icps_tooshort); 447 return (IPPROTO_DONE); 448 } 449 ip = mtod(m, struct ip *); 450 m->m_len -= hlen; 451 m->m_data += hlen; 452 icp = mtod(m, struct icmp *); 453 if (in_cksum(m, icmplen)) { 454 ICMPSTAT_INC(icps_checksum); 455 goto freeit; 456 } 457 m->m_len += hlen; 458 m->m_data -= hlen; 459 460 #ifdef ICMPPRINTFS 461 if (icmpprintfs) 462 printf("icmp_input, type %d code %d\n", icp->icmp_type, 463 icp->icmp_code); 464 #endif 465 466 /* 467 * Message type specific processing. 468 */ 469 if (icp->icmp_type > ICMP_MAXTYPE) 470 goto raw; 471 472 /* Initialize */ 473 bzero(&icmpsrc, sizeof(icmpsrc)); 474 icmpsrc.sin_len = sizeof(struct sockaddr_in); 475 icmpsrc.sin_family = AF_INET; 476 bzero(&icmpdst, sizeof(icmpdst)); 477 icmpdst.sin_len = sizeof(struct sockaddr_in); 478 icmpdst.sin_family = AF_INET; 479 bzero(&icmpgw, sizeof(icmpgw)); 480 icmpgw.sin_len = sizeof(struct sockaddr_in); 481 icmpgw.sin_family = AF_INET; 482 483 ICMPSTAT_INC(icps_inhist[icp->icmp_type]); 484 code = icp->icmp_code; 485 switch (icp->icmp_type) { 486 case ICMP_UNREACH: 487 switch (code) { 488 case ICMP_UNREACH_NET: 489 case ICMP_UNREACH_HOST: 490 case ICMP_UNREACH_SRCFAIL: 491 case ICMP_UNREACH_NET_UNKNOWN: 492 case ICMP_UNREACH_HOST_UNKNOWN: 493 case ICMP_UNREACH_ISOLATED: 494 case ICMP_UNREACH_TOSNET: 495 case ICMP_UNREACH_TOSHOST: 496 case ICMP_UNREACH_HOST_PRECEDENCE: 497 case ICMP_UNREACH_PRECEDENCE_CUTOFF: 498 code = PRC_UNREACH_NET; 499 break; 500 501 case ICMP_UNREACH_NEEDFRAG: 502 code = PRC_MSGSIZE; 503 break; 504 505 /* 506 * RFC 1122, Sections 3.2.2.1 and 4.2.3.9. 507 * Treat subcodes 2,3 as immediate RST 508 */ 509 case ICMP_UNREACH_PROTOCOL: 510 code = PRC_UNREACH_PROTOCOL; 511 break; 512 case ICMP_UNREACH_PORT: 513 code = PRC_UNREACH_PORT; 514 break; 515 516 case ICMP_UNREACH_NET_PROHIB: 517 case ICMP_UNREACH_HOST_PROHIB: 518 case ICMP_UNREACH_FILTER_PROHIB: 519 code = PRC_UNREACH_ADMIN_PROHIB; 520 break; 521 522 default: 523 goto badcode; 524 } 525 goto deliver; 526 527 case ICMP_TIMXCEED: 528 if (code > 1) 529 goto badcode; 530 code += PRC_TIMXCEED_INTRANS; 531 goto deliver; 532 533 case ICMP_PARAMPROB: 534 if (code > 1) 535 goto badcode; 536 code = PRC_PARAMPROB; 537 deliver: 538 /* 539 * Problem with datagram; advise higher level routines. 540 */ 541 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) || 542 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) { 543 ICMPSTAT_INC(icps_badlen); 544 goto freeit; 545 } 546 /* Discard ICMP's in response to multicast packets */ 547 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr))) 548 goto badcode; 549 #ifdef ICMPPRINTFS 550 if (icmpprintfs) 551 printf("deliver to protocol %d\n", icp->icmp_ip.ip_p); 552 #endif 553 icmpsrc.sin_addr = icp->icmp_ip.ip_dst; 554 /* 555 * XXX if the packet contains [IPv4 AH TCP], we can't make a 556 * notification to TCP layer. 557 */ 558 i = sizeof(struct ip) + min(icmplen, ICMP_ADVLENPREF(icp)); 559 ip_stripoptions(m); 560 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) { 561 /* This should actually not happen */ 562 ICMPSTAT_INC(icps_tooshort); 563 return (IPPROTO_DONE); 564 } 565 ip = mtod(m, struct ip *); 566 icp = (struct icmp *)(ip + 1); 567 /* 568 * The upper layer handler can rely on: 569 * - The outer IP header has no options. 570 * - The outer IP header, the ICMP header, the inner IP header, 571 * and the first n bytes of the inner payload are contiguous. 572 * n is at least 8, but might be larger based on 573 * ICMP_ADVLENPREF. See its definition in ip_icmp.h. 574 */ 575 if (ip_ctlprotox[icp->icmp_ip.ip_p] != NULL) 576 ip_ctlprotox[icp->icmp_ip.ip_p](code, 577 (struct sockaddr *)&icmpsrc, &icp->icmp_ip); 578 break; 579 580 badcode: 581 ICMPSTAT_INC(icps_badcode); 582 break; 583 584 case ICMP_ECHO: 585 if (!V_icmpbmcastecho 586 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { 587 ICMPSTAT_INC(icps_bmcastecho); 588 break; 589 } 590 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0) 591 goto freeit; 592 icp->icmp_type = ICMP_ECHOREPLY; 593 goto reflect; 594 595 case ICMP_TSTAMP: 596 if (V_icmptstamprepl == 0) 597 break; 598 if (!V_icmpbmcastecho 599 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) { 600 ICMPSTAT_INC(icps_bmcasttstamp); 601 break; 602 } 603 if (icmplen < ICMP_TSLEN) { 604 ICMPSTAT_INC(icps_badlen); 605 break; 606 } 607 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0) 608 goto freeit; 609 icp->icmp_type = ICMP_TSTAMPREPLY; 610 icp->icmp_rtime = iptime(); 611 icp->icmp_ttime = icp->icmp_rtime; /* bogus, do later! */ 612 goto reflect; 613 614 case ICMP_MASKREQ: 615 if (V_icmpmaskrepl == 0) 616 break; 617 /* 618 * We are not able to respond with all ones broadcast 619 * unless we receive it over a point-to-point interface. 620 */ 621 if (icmplen < ICMP_MASKLEN) 622 break; 623 switch (ip->ip_dst.s_addr) { 624 case INADDR_BROADCAST: 625 case INADDR_ANY: 626 icmpdst.sin_addr = ip->ip_src; 627 break; 628 629 default: 630 icmpdst.sin_addr = ip->ip_dst; 631 } 632 ia = (struct in_ifaddr *)ifaof_ifpforaddr( 633 (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif); 634 if (ia == NULL) 635 break; 636 if (ia->ia_ifp == NULL) 637 break; 638 icp->icmp_type = ICMP_MASKREPLY; 639 if (V_icmpmaskfake == 0) 640 icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr; 641 else 642 icp->icmp_mask = V_icmpmaskfake; 643 if (ip->ip_src.s_addr == 0) { 644 if (ia->ia_ifp->if_flags & IFF_BROADCAST) 645 ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr; 646 else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT) 647 ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr; 648 } 649 reflect: 650 ICMPSTAT_INC(icps_reflect); 651 ICMPSTAT_INC(icps_outhist[icp->icmp_type]); 652 icmp_reflect(m); 653 return (IPPROTO_DONE); 654 655 case ICMP_REDIRECT: 656 if (V_log_redirect) { 657 u_long src, dst, gw; 658 659 src = ntohl(ip->ip_src.s_addr); 660 dst = ntohl(icp->icmp_ip.ip_dst.s_addr); 661 gw = ntohl(icp->icmp_gwaddr.s_addr); 662 printf("icmp redirect from %d.%d.%d.%d: " 663 "%d.%d.%d.%d => %d.%d.%d.%d\n", 664 (int)(src >> 24), (int)((src >> 16) & 0xff), 665 (int)((src >> 8) & 0xff), (int)(src & 0xff), 666 (int)(dst >> 24), (int)((dst >> 16) & 0xff), 667 (int)((dst >> 8) & 0xff), (int)(dst & 0xff), 668 (int)(gw >> 24), (int)((gw >> 16) & 0xff), 669 (int)((gw >> 8) & 0xff), (int)(gw & 0xff)); 670 } 671 /* 672 * RFC1812 says we must ignore ICMP redirects if we 673 * are acting as router. 674 */ 675 if (V_drop_redirect || V_ipforwarding) 676 break; 677 if (code > 3) 678 goto badcode; 679 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) || 680 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) { 681 ICMPSTAT_INC(icps_badlen); 682 break; 683 } 684 /* 685 * Short circuit routing redirects to force 686 * immediate change in the kernel's routing 687 * tables. The message is also handed to anyone 688 * listening on a raw socket (e.g. the routing 689 * daemon for use in updating its tables). 690 */ 691 icmpgw.sin_addr = ip->ip_src; 692 icmpdst.sin_addr = icp->icmp_gwaddr; 693 #ifdef ICMPPRINTFS 694 if (icmpprintfs) { 695 char dstbuf[INET_ADDRSTRLEN]; 696 char gwbuf[INET_ADDRSTRLEN]; 697 698 printf("redirect dst %s to %s\n", 699 inet_ntoa_r(icp->icmp_ip.ip_dst, dstbuf), 700 inet_ntoa_r(icp->icmp_gwaddr, gwbuf)); 701 } 702 #endif 703 icmpsrc.sin_addr = icp->icmp_ip.ip_dst; 704 705 /* 706 * RFC 1122 says network (code 0,2) redirects SHOULD 707 * be treated identically to the host redirects. 708 * Given that, ignore network masks. 709 */ 710 711 /* 712 * Variable values: 713 * icmpsrc: route destination 714 * icmpdst: route gateway 715 * icmpgw: message source 716 */ 717 718 if (icmp_verify_redirect_gateway(&icmpgw, &icmpsrc, &icmpdst, 719 M_GETFIB(m)) != 0) { 720 /* TODO: increment bad redirects here */ 721 break; 722 } 723 724 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) { 725 rib_add_redirect(fibnum, (struct sockaddr *)&icmpsrc, 726 (struct sockaddr *)&icmpdst, 727 (struct sockaddr *)&icmpgw, m->m_pkthdr.rcvif, 728 RTF_GATEWAY, V_redirtimeout); 729 } 730 break; 731 732 /* 733 * No kernel processing for the following; 734 * just fall through to send to raw listener. 735 */ 736 case ICMP_ECHOREPLY: 737 case ICMP_ROUTERADVERT: 738 case ICMP_ROUTERSOLICIT: 739 case ICMP_TSTAMPREPLY: 740 case ICMP_IREQREPLY: 741 case ICMP_MASKREPLY: 742 case ICMP_SOURCEQUENCH: 743 default: 744 break; 745 } 746 747 raw: 748 *mp = m; 749 rip_input(mp, offp, proto); 750 return (IPPROTO_DONE); 751 752 freeit: 753 m_freem(m); 754 return (IPPROTO_DONE); 755 } 756 757 /* 758 * Reflect the ip packet back to the source 759 */ 760 static void 761 icmp_reflect(struct mbuf *m) 762 { 763 struct ip *ip = mtod(m, struct ip *); 764 struct ifaddr *ifa; 765 struct ifnet *ifp; 766 struct in_ifaddr *ia; 767 struct in_addr t; 768 struct nhop_object *nh; 769 struct mbuf *opts = NULL; 770 int optlen = (ip->ip_hl << 2) - sizeof(struct ip); 771 772 NET_EPOCH_ASSERT(); 773 774 if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 775 (IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) && !V_ip_allow_net240) || 776 (IN_ZERONET(ntohl(ip->ip_src.s_addr)) && !V_ip_allow_net0) ) { 777 m_freem(m); /* Bad return address */ 778 ICMPSTAT_INC(icps_badaddr); 779 goto done; /* Ip_output() will check for broadcast */ 780 } 781 782 t = ip->ip_dst; 783 ip->ip_dst = ip->ip_src; 784 785 /* 786 * Source selection for ICMP replies: 787 * 788 * If the incoming packet was addressed directly to one of our 789 * own addresses, use dst as the src for the reply. 790 */ 791 CK_LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) { 792 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) { 793 t = IA_SIN(ia)->sin_addr; 794 goto match; 795 } 796 } 797 798 /* 799 * If the incoming packet was addressed to one of our broadcast 800 * addresses, use the first non-broadcast address which corresponds 801 * to the incoming interface. 802 */ 803 ifp = m->m_pkthdr.rcvif; 804 if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) { 805 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 806 if (ifa->ifa_addr->sa_family != AF_INET) 807 continue; 808 ia = ifatoia(ifa); 809 if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr == 810 t.s_addr) { 811 t = IA_SIN(ia)->sin_addr; 812 goto match; 813 } 814 } 815 } 816 /* 817 * If the packet was transiting through us, use the address of 818 * the interface the packet came through in. If that interface 819 * doesn't have a suitable IP address, the normal selection 820 * criteria apply. 821 */ 822 if (V_icmp_rfi && ifp != NULL) { 823 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 824 if (ifa->ifa_addr->sa_family != AF_INET) 825 continue; 826 ia = ifatoia(ifa); 827 t = IA_SIN(ia)->sin_addr; 828 goto match; 829 } 830 } 831 /* 832 * If the incoming packet was not addressed directly to us, use 833 * designated interface for icmp replies specified by sysctl 834 * net.inet.icmp.reply_src (default not set). Otherwise continue 835 * with normal source selection. 836 */ 837 if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) { 838 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { 839 if (ifa->ifa_addr->sa_family != AF_INET) 840 continue; 841 ia = ifatoia(ifa); 842 t = IA_SIN(ia)->sin_addr; 843 goto match; 844 } 845 } 846 /* 847 * If the packet was transiting through us, use the address of 848 * the interface that is the closest to the packet source. 849 * When we don't have a route back to the packet source, stop here 850 * and drop the packet. 851 */ 852 nh = fib4_lookup(M_GETFIB(m), ip->ip_dst, 0, NHR_NONE, 0); 853 if (nh == NULL) { 854 m_freem(m); 855 ICMPSTAT_INC(icps_noroute); 856 goto done; 857 } 858 t = IA_SIN(ifatoia(nh->nh_ifa))->sin_addr; 859 match: 860 #ifdef MAC 861 mac_netinet_icmp_replyinplace(m); 862 #endif 863 ip->ip_src = t; 864 ip->ip_ttl = V_ip_defttl; 865 866 if (optlen > 0) { 867 u_char *cp; 868 int opt, cnt; 869 u_int len; 870 871 /* 872 * Retrieve any source routing from the incoming packet; 873 * add on any record-route or timestamp options. 874 */ 875 cp = (u_char *) (ip + 1); 876 if ((opts = ip_srcroute(m)) == NULL && 877 (opts = m_gethdr(M_NOWAIT, MT_DATA))) { 878 opts->m_len = sizeof(struct in_addr); 879 mtod(opts, struct in_addr *)->s_addr = 0; 880 } 881 if (opts) { 882 #ifdef ICMPPRINTFS 883 if (icmpprintfs) 884 printf("icmp_reflect optlen %d rt %d => ", 885 optlen, opts->m_len); 886 #endif 887 for (cnt = optlen; cnt > 0; cnt -= len, cp += len) { 888 opt = cp[IPOPT_OPTVAL]; 889 if (opt == IPOPT_EOL) 890 break; 891 if (opt == IPOPT_NOP) 892 len = 1; 893 else { 894 if (cnt < IPOPT_OLEN + sizeof(*cp)) 895 break; 896 len = cp[IPOPT_OLEN]; 897 if (len < IPOPT_OLEN + sizeof(*cp) || 898 len > cnt) 899 break; 900 } 901 /* 902 * Should check for overflow, but it "can't happen" 903 */ 904 if (opt == IPOPT_RR || opt == IPOPT_TS || 905 opt == IPOPT_SECURITY) { 906 bcopy((caddr_t)cp, 907 mtod(opts, caddr_t) + opts->m_len, len); 908 opts->m_len += len; 909 } 910 } 911 /* Terminate & pad, if necessary */ 912 cnt = opts->m_len % 4; 913 if (cnt) { 914 for (; cnt < 4; cnt++) { 915 *(mtod(opts, caddr_t) + opts->m_len) = 916 IPOPT_EOL; 917 opts->m_len++; 918 } 919 } 920 #ifdef ICMPPRINTFS 921 if (icmpprintfs) 922 printf("%d\n", opts->m_len); 923 #endif 924 } 925 ip_stripoptions(m); 926 } 927 m_tag_delete_nonpersistent(m); 928 m->m_flags &= ~(M_BCAST|M_MCAST); 929 icmp_send(m, opts); 930 done: 931 if (opts) 932 (void)m_free(opts); 933 } 934 935 /* 936 * Verifies if redirect message is valid, according to RFC 1122 937 * 938 * @src: sockaddr with address of redirect originator 939 * @dst: sockaddr with destination in question 940 * @gateway: new proposed gateway 941 * 942 * Returns 0 on success. 943 */ 944 static int 945 icmp_verify_redirect_gateway(struct sockaddr_in *src, struct sockaddr_in *dst, 946 struct sockaddr_in *gateway, u_int fibnum) 947 { 948 struct nhop_object *nh; 949 struct ifaddr *ifa; 950 951 NET_EPOCH_ASSERT(); 952 953 /* Verify the gateway is directly reachable. */ 954 if ((ifa = ifa_ifwithnet((struct sockaddr *)gateway, 0, fibnum))==NULL) 955 return (ENETUNREACH); 956 957 /* TODO: fib-aware. */ 958 if (ifa_ifwithaddr_check((struct sockaddr *)gateway)) 959 return (EHOSTUNREACH); 960 961 nh = fib4_lookup(fibnum, dst->sin_addr, 0, NHR_NONE, 0); 962 if (nh == NULL) 963 return (EINVAL); 964 965 /* 966 * If the redirect isn't from our current router for this dst, 967 * it's either old or wrong. If it redirects us to ourselves, 968 * we have a routing loop, perhaps as a result of an interface 969 * going down recently. 970 */ 971 if (!sa_equal((struct sockaddr *)src, &nh->gw_sa)) 972 return (EINVAL); 973 if (nh->nh_ifa != ifa && ifa->ifa_addr->sa_family != AF_LINK) 974 return (EINVAL); 975 976 /* If host route already exists, ignore redirect. */ 977 if (nh->nh_flags & NHF_HOST) 978 return (EEXIST); 979 980 /* If the prefix is directly reachable, ignore redirect. */ 981 if (!(nh->nh_flags & NHF_GATEWAY)) 982 return (EEXIST); 983 984 return (0); 985 } 986 987 /* 988 * Send an icmp packet back to the ip level, 989 * after supplying a checksum. 990 */ 991 static void 992 icmp_send(struct mbuf *m, struct mbuf *opts) 993 { 994 struct ip *ip = mtod(m, struct ip *); 995 int hlen; 996 struct icmp *icp; 997 998 hlen = ip->ip_hl << 2; 999 m->m_data += hlen; 1000 m->m_len -= hlen; 1001 icp = mtod(m, struct icmp *); 1002 icp->icmp_cksum = 0; 1003 icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen); 1004 m->m_data -= hlen; 1005 m->m_len += hlen; 1006 m->m_pkthdr.rcvif = (struct ifnet *)0; 1007 #ifdef ICMPPRINTFS 1008 if (icmpprintfs) { 1009 char dstbuf[INET_ADDRSTRLEN]; 1010 char srcbuf[INET_ADDRSTRLEN]; 1011 1012 printf("icmp_send dst %s src %s\n", 1013 inet_ntoa_r(ip->ip_dst, dstbuf), 1014 inet_ntoa_r(ip->ip_src, srcbuf)); 1015 } 1016 #endif 1017 (void) ip_output(m, opts, NULL, 0, NULL, NULL); 1018 } 1019 1020 /* 1021 * Return milliseconds since 00:00 UTC in network format. 1022 */ 1023 uint32_t 1024 iptime(void) 1025 { 1026 struct timeval atv; 1027 u_long t; 1028 1029 getmicrotime(&atv); 1030 t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000; 1031 return (htonl(t)); 1032 } 1033 1034 /* 1035 * Return the next larger or smaller MTU plateau (table from RFC 1191) 1036 * given current value MTU. If DIR is less than zero, a larger plateau 1037 * is returned; otherwise, a smaller value is returned. 1038 */ 1039 int 1040 ip_next_mtu(int mtu, int dir) 1041 { 1042 static int mtutab[] = { 1043 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508, 1044 296, 68, 0 1045 }; 1046 int i, size; 1047 1048 size = (sizeof mtutab) / (sizeof mtutab[0]); 1049 if (dir >= 0) { 1050 for (i = 0; i < size; i++) 1051 if (mtu > mtutab[i]) 1052 return mtutab[i]; 1053 } else { 1054 for (i = size - 1; i >= 0; i--) 1055 if (mtu < mtutab[i]) 1056 return mtutab[i]; 1057 if (mtu == mtutab[0]) 1058 return mtutab[0]; 1059 } 1060 return 0; 1061 } 1062 #endif /* INET */ 1063 1064 /* 1065 * badport_bandlim() - check for ICMP bandwidth limit 1066 * 1067 * Return 0 if it is ok to send an ICMP error response, -1 if we have 1068 * hit our bandwidth limit and it is not ok. 1069 * 1070 * If icmplim is <= 0, the feature is disabled and 0 is returned. 1071 * 1072 * For now we separate the TCP and UDP subsystems w/ different 'which' 1073 * values. We may eventually remove this separation (and simplify the 1074 * code further). 1075 * 1076 * Note that the printing of the error message is delayed so we can 1077 * properly print the icmp error rate that the system was trying to do 1078 * (i.e. 22000/100 pps, etc...). This can cause long delays in printing 1079 * the 'final' error, but it doesn't make sense to solve the printing 1080 * delay with more complex code. 1081 */ 1082 struct icmp_rate { 1083 const char *descr; 1084 struct counter_rate cr; 1085 }; 1086 VNET_DEFINE_STATIC(struct icmp_rate, icmp_rates[BANDLIM_MAX]) = { 1087 { "icmp unreach response" }, 1088 { "icmp ping response" }, 1089 { "icmp tstamp response" }, 1090 { "closed port RST response" }, 1091 { "open port RST response" }, 1092 { "icmp6 unreach response" }, 1093 { "sctp ootb response" } 1094 }; 1095 #define V_icmp_rates VNET(icmp_rates) 1096 1097 static void 1098 icmp_bandlimit_init(void) 1099 { 1100 1101 for (int i = 0; i < BANDLIM_MAX; i++) { 1102 V_icmp_rates[i].cr.cr_rate = counter_u64_alloc(M_WAITOK); 1103 V_icmp_rates[i].cr.cr_ticks = ticks; 1104 } 1105 } 1106 VNET_SYSINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY, 1107 icmp_bandlimit_init, NULL); 1108 1109 static void 1110 icmp_bandlimit_uninit(void) 1111 { 1112 1113 for (int i = 0; i < BANDLIM_MAX; i++) 1114 counter_u64_free(V_icmp_rates[i].cr.cr_rate); 1115 } 1116 VNET_SYSUNINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD, 1117 icmp_bandlimit_uninit, NULL); 1118 1119 int 1120 badport_bandlim(int which) 1121 { 1122 int64_t pps; 1123 1124 if (V_icmplim == 0 || which == BANDLIM_UNLIMITED) 1125 return (0); 1126 1127 KASSERT(which >= 0 && which < BANDLIM_MAX, 1128 ("%s: which %d", __func__, which)); 1129 1130 if ((V_icmplim + V_icmplim_curr_jitter) <= 0) 1131 V_icmplim_curr_jitter = -V_icmplim + 1; 1132 1133 pps = counter_ratecheck(&V_icmp_rates[which].cr, V_icmplim + 1134 V_icmplim_curr_jitter); 1135 if (pps > 0) { 1136 /* 1137 * Adjust limit +/- to jitter the measurement to deny a 1138 * side-channel port scan as in CVE-2020-25705 1139 */ 1140 if (V_icmplim_jitter > 0) { 1141 int32_t inc = 1142 arc4random_uniform(V_icmplim_jitter * 2 +1) 1143 - V_icmplim_jitter; 1144 1145 V_icmplim_curr_jitter = inc; 1146 } 1147 } 1148 if (pps == -1) 1149 return (-1); 1150 if (pps > 0 && V_icmplim_output) 1151 log(LOG_NOTICE, "Limiting %s from %jd to %d packets/sec\n", 1152 V_icmp_rates[which].descr, (intmax_t )pps, V_icmplim + 1153 V_icmplim_curr_jitter); 1154 return (0); 1155 } 1156