bsd/netinet6/ah_output.c

   1 /*
   2  * Copyright (c) 2008-2011 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*      $FreeBSD: src/sys/netinet6/ah_output.c,v 1.1.2.3 2001/07/03 11:01:49 ume Exp $  */
  30 /*      $KAME: ah_output.c,v 1.30 2001/02/21 00:50:53 itojun Exp $      */
  31
  32 /*
  33  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
  34  * All rights reserved.
  35  *
  36  * Redistribution and use in source and binary forms, with or without
  37  * modification, are permitted provided that the following conditions
  38  * are met:
  39  * 1. Redistributions of source code must retain the above copyright
  40  *    notice, this list of conditions and the following disclaimer.
  41  * 2. Redistributions in binary form must reproduce the above copyright
  42  *    notice, this list of conditions and the following disclaimer in the
  43  *    documentation and/or other materials provided with the distribution.
  44  * 3. Neither the name of the project nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61 /*
  62  * RFC1826/2402 authentication header.
  63  */
  64
  65 #define _IP_VHL
  66
  67 #include <sys/param.h>
  68 #include <sys/systm.h>
  69 #include <sys/malloc.h>
  70 #include <sys/mbuf.h>
  71 #include <sys/domain.h>
  72 #include <sys/protosw.h>
  73 #include <sys/socket.h>
  74 #include <sys/socketvar.h>
  75 #include <sys/errno.h>
  76 #include <sys/time.h>
  77 #include <sys/kernel.h>
  78 #include <sys/syslog.h>
  79
  80 #include <net/if.h>
  81 #include <net/route.h>
  82
  83 #include <netinet/in.h>
  84
  85 #include <netinet/in_systm.h>
  86 #include <netinet/ip.h>
  87 #include <netinet/in_var.h>
  88
  89 #if INET6
  90 #include <netinet/ip6.h>
  91 #include <netinet6/ip6_var.h>
  92 #include <netinet/icmp6.h>
  93 #endif
  94
  95 #include <netinet6/ipsec.h>
  96 #if INET6
  97 #include <netinet6/ipsec6.h>
  98 #endif
  99 #include <netinet6/ah.h>
 100 #if INET6
 101 #include <netinet6/ah6.h>
 102 #endif
 103 #include <netkey/key.h>
 104 #include <netkey/keydb.h>
 105
 106 #include <net/net_osdep.h>
 107
 108 #if INET
 109 static struct in_addr *ah4_finaldst(struct mbuf *);
 110 #endif
 111
 112 extern lck_mtx_t *sadb_mutex;
 113
 114 /*
 115  * compute AH header size.
 116  * transport mode only.  for tunnel mode, we should implement
 117  * virtual interface, and control MTU/MSS by the interface MTU.
 118  */
 119 size_t
 120 ah_hdrsiz(isr)
 121         struct ipsecrequest *isr;
 122 {
 123
 124         /* sanity check */
 125         if (isr == NULL)
 126                 panic("ah_hdrsiz: NULL was passed.\n");
 127
 128         if (isr->saidx.proto != IPPROTO_AH)
 129                 panic("unsupported mode passed to ah_hdrsiz");
 130
 131 #if 0
 132         {
 133
 134                 lck_mtx_lock(sadb_mutex);
 135                 const struct ah_algorithm *algo;
 136                 size_t hdrsiz;
 137
 138                 /*%%%%% this needs to change - no sav in ipsecrequest any more */
 139                 if (isr->sav == NULL)
 140                         goto estimate;
 141                 if (isr->sav->state != SADB_SASTATE_MATURE
 142                  && isr->sav->state != SADB_SASTATE_DYING)
 143                         goto estimate;
 144
 145                 /* we need transport mode AH. */
 146                 algo = ah_algorithm_lookup(isr->sav->alg_auth);
 147                 if (!algo)
 148                         goto estimate;
 149
 150                 /*
 151                  * XXX
 152                  * right now we don't calcurate the padding size.  simply
 153                  * treat the padding size as constant, for simplicity.
 154                  *
 155                  * XXX variable size padding support
 156                  */
 157                 hdrsiz = (((*algo->sumsiz)(isr->sav) + 3) & ~(4 - 1));
 158                 if (isr->sav->flags & SADB_X_EXT_OLD)
 159                         hdrsiz += sizeof(struct ah);
 160                 else
 161                         hdrsiz += sizeof(struct newah);
 162
 163                 lck_mtx_unlock(sadb_mutex);
 164                 return hdrsiz;
 165         }
 166
 167 estimate:
 168 #endif
 169
 170     //lck_mtx_unlock(sadb_mutex);
 171         /* ASSUMING:
 172          *      sizeof(struct newah) > sizeof(struct ah).
 173          *      16 = (16 + 3) & ~(4 - 1).
 174          */
 175         return sizeof(struct newah) + 16;
 176 }
 177
 178 #if INET
 179 /*
 180  * Modify the packet so that it includes the authentication data.
 181  * The mbuf passed must start with IPv4 header.
 182  *
 183  * assumes that the first mbuf contains IPv4 header + option only.
 184  * the function does not modify m.
 185  */
 186 int
 187 ah4_output(m, sav)
 188         struct mbuf *m;
 189         struct secasvar *sav;
 190 {
 191         const struct ah_algorithm *algo;
 192         u_int32_t spi;
 193         u_char *ahdrpos;
 194         u_char *ahsumpos = NULL;
 195         size_t hlen = 0;        /*IP header+option in bytes*/
 196         size_t plen = 0;        /*AH payload size in bytes*/
 197         size_t ahlen = 0;       /*plen + sizeof(ah)*/
 198         struct ip *ip;
 199         struct in_addr dst = { 0 };
 200         struct in_addr *finaldst;
 201         int error;
 202
 203         /* sanity checks */
 204         if ((sav->flags & SADB_X_EXT_OLD) == 0 && !sav->replay) {
 205                 ip = mtod(m, struct ip *);
 206                 ipseclog((LOG_DEBUG, "ah4_output: internal error: "
 207                         "sav->replay is null: %x->%x, SPI=%u\n",
 208                         (u_int32_t)ntohl(ip->ip_src.s_addr),
 209                         (u_int32_t)ntohl(ip->ip_dst.s_addr),
 210                         (u_int32_t)ntohl(sav->spi)));
 211                 IPSEC_STAT_INCREMENT(ipsecstat.out_inval);
 212                 m_freem(m);
 213                 return EINVAL;
 214         }
 215
 216         algo = ah_algorithm_lookup(sav->alg_auth);
 217         if (!algo) {
 218                 ipseclog((LOG_ERR, "ah4_output: unsupported algorithm: "
 219                     "SPI=%u\n", (u_int32_t)ntohl(sav->spi)));
 220                 IPSEC_STAT_INCREMENT(ipsecstat.out_inval);
 221                 m_freem(m);
 222                 return EINVAL;
 223         }
 224         spi = sav->spi;
 225
 226         /*
 227          * determine the size to grow.
 228          */
 229         if (sav->flags & SADB_X_EXT_OLD) {
 230                 /* RFC 1826 */
 231                 plen = ((*algo->sumsiz)(sav) + 3) & ~(4 - 1); /*XXX pad to 8byte?*/
 232                 ahlen = plen + sizeof(struct ah);
 233         } else {
 234                 /* RFC 2402 */
 235                 plen = ((*algo->sumsiz)(sav) + 3) & ~(4 - 1); /*XXX pad to 8byte?*/
 236                 ahlen = plen + sizeof(struct newah);
 237         }
 238
 239         /*
 240          * grow the mbuf to accomodate AH.
 241          */
 242         ip = mtod(m, struct ip *);
 243 #ifdef _IP_VHL
 244         hlen = IP_VHL_HL(ip->ip_vhl) << 2;
 245 #else
 246         hlen = ip->ip_hl << 2;
 247 #endif
 248
 249         if (m->m_len != hlen)
 250                 panic("ah4_output: assumption failed (first mbuf length)");
 251         if (M_LEADINGSPACE(m->m_next) < ahlen) {
 252                 struct mbuf *n;
 253                 MGET(n, M_DONTWAIT, MT_DATA);
 254                 if (!n) {
 255                         ipseclog((LOG_DEBUG, "ENOBUFS in ah4_output %d\n",
 256                             __LINE__));
 257                         m_freem(m);
 258                         return ENOBUFS;
 259                 }
 260                 n->m_len = ahlen;
 261                 n->m_next = m->m_next;
 262                 m->m_next = n;
 263                 m->m_pkthdr.len += ahlen;
 264                 ahdrpos = mtod(n, u_char *);
 265         } else {
 266                 m->m_next->m_len += ahlen;
 267                 m->m_next->m_data -= ahlen;
 268                 m->m_pkthdr.len += ahlen;
 269                 ahdrpos = mtod(m->m_next, u_char *);
 270         }
 271
 272         ip = mtod(m, struct ip *);      /*just to be sure*/
 273
 274         /*
 275          * initialize AH.
 276          */
 277         if (sav->flags & SADB_X_EXT_OLD) {
 278                 struct ah *ahdr;
 279
 280                 ahdr = (struct ah *)(void *)ahdrpos;
 281                 ahsumpos = (u_char *)(ahdr + 1);
 282                 ahdr->ah_len = plen >> 2;
 283                 ahdr->ah_nxt = ip->ip_p;
 284                 ahdr->ah_reserve = htons(0);
 285                 ahdr->ah_spi = spi;
 286                 bzero(ahdr + 1, plen);
 287         } else {
 288                 struct newah *ahdr;
 289
 290                 ahdr = (struct newah *)(void *)ahdrpos;
 291                 ahsumpos = (u_char *)(ahdr + 1);
 292                 ahdr->ah_len = (plen >> 2) + 1; /* plus one for seq# */
 293                 ahdr->ah_nxt = ip->ip_p;
 294                 ahdr->ah_reserve = htons(0);
 295                 ahdr->ah_spi = spi;
 296                 if (sav->replay->count == ~0) {
 297                         if ((sav->flags & SADB_X_EXT_CYCSEQ) == 0) {
 298                                 /* XXX Is it noisy ? */
 299                                 ipseclog((LOG_WARNING,
 300                                     "replay counter overflowed. %s\n",
 301                                     ipsec_logsastr(sav)));
 302                                 IPSEC_STAT_INCREMENT(ipsecstat.out_inval);
 303                                 m_freem(m);
 304                                 return EINVAL;
 305                         }
 306                 }
 307                 lck_mtx_lock(sadb_mutex);
 308                 sav->replay->count++;
 309                 lck_mtx_unlock(sadb_mutex);
 310                 /*
 311                  * XXX sequence number must not be cycled, if the SA is
 312                  * installed by IKE daemon.
 313                  */
 314                 ahdr->ah_seq = htonl(sav->replay->count);
 315                 bzero(ahdr + 1, plen);
 316         }
 317
 318         /*
 319          * modify IPv4 header.
 320          */
 321         ip->ip_p = IPPROTO_AH;
 322         if (ahlen < (IP_MAXPACKET - ntohs(ip->ip_len)))
 323                 ip->ip_len = htons(ntohs(ip->ip_len) + ahlen);
 324         else {
 325                 ipseclog((LOG_ERR, "IPv4 AH output: size exceeds limit\n"));
 326                 IPSEC_STAT_INCREMENT(ipsecstat.out_inval);
 327                 m_freem(m);
 328                 return EMSGSIZE;
 329         }
 330
 331         /*
 332          * If there is source routing option, update destination field in
 333          * the IPv4 header to the final destination.
 334          * Note that we do not need to update source routing option itself
 335          * (as done in IPv4 AH processing -- see ip6_output()), since
 336          * source routing option is not part of the ICV computation.
 337          */
 338         finaldst = ah4_finaldst(m);
 339         if (finaldst) {
 340                 dst.s_addr = ip->ip_dst.s_addr;
 341                 ip->ip_dst.s_addr = finaldst->s_addr;
 342         }
 343
 344         /*
 345          * calcurate the checksum, based on security association
 346          * and the algorithm specified.
 347          */
 348         error = ah4_calccksum(m, (caddr_t)ahsumpos, plen, algo, sav);
 349         if (error) {
 350                 ipseclog((LOG_ERR,
 351                     "error after ah4_calccksum, called from ah4_output"));
 352                 m_freem(m);
 353                 m = NULL;
 354                 IPSEC_STAT_INCREMENT(ipsecstat.out_inval);
 355                 return error;
 356         }
 357
 358         if (finaldst) {
 359                 ip = mtod(m, struct ip *);      /*just to make sure*/
 360                 ip->ip_dst.s_addr = dst.s_addr;
 361         }
 362         lck_mtx_lock(sadb_stat_mutex);
 363         ipsecstat.out_success++;
 364         ipsecstat.out_ahhist[sav->alg_auth]++;
 365         lck_mtx_unlock(sadb_stat_mutex);
 366         key_sa_recordxfer(sav, m);
 367
 368         return 0;
 369 }
 370 #endif
 371
 372 /* Calculate AH length */
 373 int
 374 ah_hdrlen(sav)
 375         struct secasvar *sav;
 376 {
 377         const struct ah_algorithm *algo;
 378         int plen, ahlen;
 379
 380         algo = ah_algorithm_lookup(sav->alg_auth);
 381         if (!algo)
 382                 return 0;
 383         if (sav->flags & SADB_X_EXT_OLD) {
 384                 /* RFC 1826 */
 385                 plen = ((*algo->sumsiz)(sav) + 3) & ~(4 - 1);   /*XXX pad to 8byte?*/
 386                 ahlen = plen + sizeof(struct ah);
 387         } else {
 388                 /* RFC 2402 */
 389                 plen = ((*algo->sumsiz)(sav) + 3) & ~(4 - 1);   /*XXX pad to 8byte?*/
 390                 ahlen = plen + sizeof(struct newah);
 391         }
 392
 393         return(ahlen);
 394 }
 395
 396 #if INET6
 397 /*
 398  * Fill in the Authentication Header and calculate checksum.
 399  */
 400 int
 401 ah6_output(m, nexthdrp, md, sav)
 402         struct mbuf *m;
 403         u_char *nexthdrp;
 404         struct mbuf *md;
 405         struct secasvar *sav;
 406 {
 407         struct mbuf *mprev;
 408         struct mbuf *mah;
 409         const struct ah_algorithm *algo;
 410         u_int32_t spi;
 411         u_char *ahsumpos = NULL;
 412         size_t plen;    /*AH payload size in bytes*/
 413         int error = 0;
 414         int ahlen;
 415         struct ip6_hdr *ip6;
 416
 417         if (m->m_len < sizeof(struct ip6_hdr)) {
 418                 ipseclog((LOG_DEBUG, "ah6_output: first mbuf too short\n"));
 419                 m_freem(m);
 420                 return EINVAL;
 421         }
 422
 423         ahlen = ah_hdrlen(sav);
 424         if (ahlen == 0)
 425                 return 0;
 426
 427         for (mprev = m; mprev && mprev->m_next != md; mprev = mprev->m_next)
 428                 ;
 429         if (!mprev || mprev->m_next != md) {
 430                 ipseclog((LOG_DEBUG, "ah6_output: md is not in chain\n"));
 431                 m_freem(m);
 432                 return EINVAL;
 433         }
 434
 435         MGET(mah, M_DONTWAIT, MT_DATA);
 436         if (!mah) {
 437                 m_freem(m);
 438                 return ENOBUFS;
 439         }
 440         if (ahlen > MLEN) {
 441                 MCLGET(mah, M_DONTWAIT);
 442                 if ((mah->m_flags & M_EXT) == 0) {
 443                         m_free(mah);
 444                         m_freem(m);
 445                         return ENOBUFS;
 446                 }
 447         }
 448         mah->m_len = ahlen;
 449         mah->m_next = md;
 450         mprev->m_next = mah;
 451         m->m_pkthdr.len += ahlen;
 452
 453         /* fix plen */
 454         if (m->m_pkthdr.len - sizeof(struct ip6_hdr) > IPV6_MAXPACKET) {
 455                 ipseclog((LOG_ERR,
 456                     "ip6_output: AH with IPv6 jumbogram is not supported\n"));
 457                 m_freem(m);
 458                 return EINVAL;
 459         }
 460         ip6 = mtod(m, struct ip6_hdr *);
 461         ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));
 462
 463         if ((sav->flags & SADB_X_EXT_OLD) == 0 && !sav->replay) {
 464                 ipseclog((LOG_DEBUG, "ah6_output: internal error: "
 465                           "sav->replay is null: SPI=%u\n",
 466                           (u_int32_t)ntohl(sav->spi)));
 467                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 468                 m_freem(m);
 469                 return EINVAL;
 470         }
 471
 472         algo = ah_algorithm_lookup(sav->alg_auth);
 473         if (!algo) {
 474                 ipseclog((LOG_ERR, "ah6_output: unsupported algorithm: "
 475                     "SPI=%u\n", (u_int32_t)ntohl(sav->spi)));
 476                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 477                 m_freem(m);
 478                 return EINVAL;
 479         }
 480         spi = sav->spi;
 481
 482         /*
 483          * initialize AH.
 484          */
 485         if (sav->flags & SADB_X_EXT_OLD) {
 486                 struct ah *ahdr = mtod(mah, struct ah *);
 487
 488                 plen = mah->m_len - sizeof(struct ah);
 489                 ahsumpos = (u_char *)(ahdr + 1);
 490                 ahdr->ah_nxt = *nexthdrp;
 491                 *nexthdrp = IPPROTO_AH;
 492                 ahdr->ah_len = plen >> 2;
 493                 ahdr->ah_reserve = htons(0);
 494                 ahdr->ah_spi = spi;
 495                 bzero(ahdr + 1, plen);
 496         } else {
 497                 struct newah *ahdr = mtod(mah, struct newah *);
 498
 499                 plen = mah->m_len - sizeof(struct newah);
 500                 ahsumpos = (u_char *)(ahdr + 1);
 501                 ahdr->ah_nxt = *nexthdrp;
 502                 *nexthdrp = IPPROTO_AH;
 503                 ahdr->ah_len = (plen >> 2) + 1; /* plus one for seq# */
 504                 ahdr->ah_reserve = htons(0);
 505                 ahdr->ah_spi = spi;
 506                 if (sav->replay->count == ~0) {
 507                         if ((sav->flags & SADB_X_EXT_CYCSEQ) == 0) {
 508                                 /* XXX Is it noisy ? */
 509                                 ipseclog((LOG_WARNING,
 510                                      "replay counter overflowed. %s\n",
 511                                     ipsec_logsastr(sav)));
 512                                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 513                                 m_freem(m);
 514                                 return EINVAL;
 515                         }
 516                 }
 517                 lck_mtx_lock(sadb_mutex);
 518                 sav->replay->count++;
 519                 lck_mtx_unlock(sadb_mutex);
 520                 /*
 521                  * XXX sequence number must not be cycled, if the SA is
 522                  * installed by IKE daemon.
 523                  */
 524                 ahdr->ah_seq = htonl(sav->replay->count);
 525                 bzero(ahdr + 1, plen);
 526         }
 527
 528         /*
 529          * calcurate the checksum, based on security association
 530          * and the algorithm specified.
 531          */
 532         error = ah6_calccksum(m, (caddr_t)ahsumpos, plen, algo, sav);
 533         if (error) {
 534                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 535                 m_freem(m);
 536         } else {
 537                 IPSEC_STAT_INCREMENT(ipsec6stat.out_success);
 538                 key_sa_recordxfer(sav, m);
 539         }
 540         IPSEC_STAT_INCREMENT(ipsec6stat.out_ahhist[sav->alg_auth]);
 541
 542         return(error);
 543 }
 544 #endif
 545
 546 #if INET
 547 /*
 548  * Find the final destination if there is loose/strict source routing option.
 549  * Returns NULL if there's no source routing options.
 550  * Returns NULL on errors too.
 551  * Note that this function will return a pointer INTO the given parameter,
 552  * struct mbuf *m.
 553  * The mbuf must be pulled up toward, at least, ip option part.
 554  */
 555 static struct in_addr *
 556 ah4_finaldst(m)
 557         struct mbuf *m;
 558 {
 559         struct ip *ip;
 560         int optlen;
 561         u_char *q;
 562         int i;
 563         int hlen;
 564
 565         if (!m)
 566                 panic("ah4_finaldst: m == NULL");
 567         ip = mtod(m, struct ip *);
 568 #ifdef _IP_VHL
 569         hlen = IP_VHL_HL(ip->ip_vhl) << 2;
 570 #else
 571         hlen = ip->ip_hl << 2;
 572 #endif
 573
 574         if (m->m_len < hlen) {
 575                 ipseclog((LOG_DEBUG,
 576                     "ah4_finaldst: parameter mbuf wrong (not pulled up)\n"));
 577                 return NULL;
 578         }
 579
 580         if (hlen == sizeof(struct ip))
 581                 return NULL;
 582
 583         optlen = hlen - sizeof(struct ip);
 584         if (optlen < 0) {
 585                 ipseclog((LOG_DEBUG, "ah4_finaldst: wrong optlen %d\n",
 586                     optlen));
 587                 return NULL;
 588         }
 589
 590         q = (u_char *)(ip + 1);
 591         i = 0;
 592         while (i < optlen) {
 593                 if (i + IPOPT_OPTVAL >= optlen)
 594                         return NULL;
 595                 if (q[i + IPOPT_OPTVAL] == IPOPT_EOL ||
 596                     q[i + IPOPT_OPTVAL] == IPOPT_NOP ||
 597                     i + IPOPT_OLEN < optlen)
 598                         ;
 599                 else
 600                         return NULL;
 601
 602                 switch (q[i + IPOPT_OPTVAL]) {
 603                 case IPOPT_EOL:
 604                         i = optlen;     /* bye */
 605                         break;
 606                 case IPOPT_NOP:
 607                         i++;
 608                         break;
 609                 case IPOPT_LSRR:
 610                 case IPOPT_SSRR:
 611                         if (q[i + IPOPT_OLEN] < 2 + sizeof(struct in_addr) ||
 612                             optlen - i < q[i + IPOPT_OLEN]) {
 613                                 ipseclog((LOG_ERR,
 614                                     "ip_finaldst: invalid IP option "
 615                                     "(code=%02x len=%02x)\n",
 616                                     q[i + IPOPT_OPTVAL], q[i + IPOPT_OLEN]));
 617                                 return NULL;
 618                         }
 619                         i += q[i + IPOPT_OLEN] - sizeof(struct in_addr);
 620                         return (struct in_addr *)(void *)(q + i);
 621                 default:
 622                         if (q[i + IPOPT_OLEN] < 2 ||
 623                             optlen - i < q[i + IPOPT_OLEN]) {
 624                                 ipseclog((LOG_ERR,
 625                                     "ip_finaldst: invalid IP option "
 626                                     "(code=%02x len=%02x)\n",
 627                                     q[i + IPOPT_OPTVAL], q[i + IPOPT_OLEN]));
 628                                 return NULL;
 629                         }
 630                         i += q[i + IPOPT_OLEN];
 631                         break;
 632                 }
 633         }
 634         return NULL;
 635 }
 636 #endif