net/ipv6/ah6.c

   1 /*
   2  * Copyright (C)2002 USAGI/WIDE Project
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  *
  18  * Authors
  19  *
  20  *      Mitsuru KANDA @USAGI       : IPv6 Support
  21  *      Kazunori MIYAZAWA @USAGI   :
  22  *      Kunihiro Ishiguro <kunihiro@ipinfusion.com>
  23  *
  24  *      This file is derived from net/ipv4/ah.c.
  25  */
  26
  27 #include <linux/module.h>
  28 #include <net/ip.h>
  29 #include <net/ah.h>
  30 #include <linux/crypto.h>
  31 #include <linux/pfkeyv2.h>
  32 #include <linux/string.h>
  33 #include <net/icmp.h>
  34 #include <net/ipv6.h>
  35 #include <net/protocol.h>
  36 #include <net/xfrm.h>
  37 #include <asm/scatterlist.h>
  38
  39 static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
  40 {
  41         u8 *opt = (u8 *)opthdr;
  42         int len = ipv6_optlen(opthdr);
  43         int off = 0;
  44         int optlen = 0;
  45
  46         off += 2;
  47         len -= 2;
  48
  49         while (len > 0) {
  50
  51                 switch (opt[off]) {
  52
  53                 case IPV6_TLV_PAD0:
  54                         optlen = 1;
  55                         break;
  56                 default:
  57                         if (len < 2)
  58                                 goto bad;
  59                         optlen = opt[off+1]+2;
  60                         if (len < optlen)
  61                                 goto bad;
  62                         if (opt[off] & 0x20)
  63                                 memset(&opt[off+2], 0, opt[off+1]);
  64                         break;
  65                 }
  66
  67                 off += optlen;
  68                 len -= optlen;
  69         }
  70         if (len == 0)
  71                 return 1;
  72
  73 bad:
  74         return 0;
  75 }
  76
  77 #ifdef CONFIG_IPV6_MIP6
  78 /**
  79  *      ipv6_rearrange_destopt - rearrange IPv6 destination options header
  80  *      @iph: IPv6 header
  81  *      @destopt: destionation options header
  82  */
  83 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
  84 {
  85         u8 *opt = (u8 *)destopt;
  86         int len = ipv6_optlen(destopt);
  87         int off = 0;
  88         int optlen = 0;
  89
  90         off += 2;
  91         len -= 2;
  92
  93         while (len > 0) {
  94
  95                 switch (opt[off]) {
  96
  97                 case IPV6_TLV_PAD0:
  98                         optlen = 1;
  99                         break;
 100                 default:
 101                         if (len < 2)
 102                                 goto bad;
 103                         optlen = opt[off+1]+2;
 104                         if (len < optlen)
 105                                 goto bad;
 106
 107                         /* Rearrange the source address in @iph and the
 108                          * addresses in home address option for final source.
 109                          * See 11.3.2 of RFC 3775 for details.
 110                          */
 111                         if (opt[off] == IPV6_TLV_HAO) {
 112                                 struct in6_addr final_addr;
 113                                 struct ipv6_destopt_hao *hao;
 114
 115                                 hao = (struct ipv6_destopt_hao *)&opt[off];
 116                                 if (hao->length != sizeof(hao->addr)) {
 117                                         if (net_ratelimit())
 118                                                 printk(KERN_WARNING "destopt hao: invalid header length: %u\n", hao->length);
 119                                         goto bad;
 120                                 }
 121                                 ipv6_addr_copy(&final_addr, &hao->addr);
 122                                 ipv6_addr_copy(&hao->addr, &iph->saddr);
 123                                 ipv6_addr_copy(&iph->saddr, &final_addr);
 124                         }
 125                         break;
 126                 }
 127
 128                 off += optlen;
 129                 len -= optlen;
 130         }
 131         if (len == 0)
 132                 return;
 133
 134 bad:
 135         return;
 136 }
 137 #endif
 138
 139 /**
 140  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
 141  *      @iph: IPv6 header
 142  *      @rthdr: routing header
 143  *
 144  *      Rearrange the destination address in @iph and the addresses in @rthdr
 145  *      so that they appear in the order they will at the final destination.
 146  *      See Appendix A2 of RFC 2402 for details.
 147  */
 148 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
 149 {
 150         int segments, segments_left;
 151         struct in6_addr *addrs;
 152         struct in6_addr final_addr;
 153
 154         segments_left = rthdr->segments_left;
 155         if (segments_left == 0)
 156                 return;
 157         rthdr->segments_left = 0;
 158
 159         /* The value of rthdr->hdrlen has been verified either by the system
 160          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
 161          * packets.  So we can assume that it is even and that segments is
 162          * greater than or equal to segments_left.
 163          *
 164          * For the same reason we can assume that this option is of type 0.
 165          */
 166         segments = rthdr->hdrlen >> 1;
 167
 168         addrs = ((struct rt0_hdr *)rthdr)->addr;
 169         ipv6_addr_copy(&final_addr, addrs + segments - 1);
 170
 171         addrs += segments - segments_left;
 172         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
 173
 174         ipv6_addr_copy(addrs, &iph->daddr);
 175         ipv6_addr_copy(&iph->daddr, &final_addr);
 176 }
 177
 178 #ifdef CONFIG_IPV6_MIP6
 179 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
 180 #else
 181 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len)
 182 #endif
 183 {
 184         union {
 185                 struct ipv6hdr *iph;
 186                 struct ipv6_opt_hdr *opth;
 187                 struct ipv6_rt_hdr *rth;
 188                 char *raw;
 189         } exthdr = { .iph = iph };
 190         char *end = exthdr.raw + len;
 191         int nexthdr = iph->nexthdr;
 192
 193         exthdr.iph++;
 194
 195         while (exthdr.raw < end) {
 196                 switch (nexthdr) {
 197 #ifdef CONFIG_IPV6_MIP6
 198                 case NEXTHDR_HOP:
 199                         if (!zero_out_mutable_opts(exthdr.opth)) {
 200                                 LIMIT_NETDEBUG(
 201                                         KERN_WARNING "overrun %sopts\n",
 202                                         nexthdr == NEXTHDR_HOP ?
 203                                                 "hop" : "dest");
 204                                 return -EINVAL;
 205                         }
 206                         break;
 207                 case NEXTHDR_DEST:
 208                         if (dir == XFRM_POLICY_OUT)
 209                                 ipv6_rearrange_destopt(iph, exthdr.opth);
 210                         if (!zero_out_mutable_opts(exthdr.opth)) {
 211                                 LIMIT_NETDEBUG(
 212                                         KERN_WARNING "overrun %sopts\n",
 213                                         nexthdr == NEXTHDR_HOP ?
 214                                                 "hop" : "dest");
 215                                 return -EINVAL;
 216                         }
 217                         break;
 218 #else
 219                 case NEXTHDR_HOP:
 220                 case NEXTHDR_DEST:
 221                         if (!zero_out_mutable_opts(exthdr.opth)) {
 222                                 LIMIT_NETDEBUG(
 223                                         KERN_WARNING "overrun %sopts\n",
 224                                         nexthdr == NEXTHDR_HOP ?
 225                                                 "hop" : "dest");
 226                                 return -EINVAL;
 227                         }
 228                         break;
 229 #endif
 230
 231                 case NEXTHDR_ROUTING:
 232                         ipv6_rearrange_rthdr(iph, exthdr.rth);
 233                         break;
 234
 235                 default :
 236                         return 0;
 237                 }
 238
 239                 nexthdr = exthdr.opth->nexthdr;
 240                 exthdr.raw += ipv6_optlen(exthdr.opth);
 241         }
 242
 243         return 0;
 244 }
 245
 246 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 247 {
 248         int err;
 249         int extlen;
 250         struct ipv6hdr *top_iph;
 251         struct ip_auth_hdr *ah;
 252         struct ah_data *ahp;
 253         u8 nexthdr;
 254         char tmp_base[8];
 255         struct {
 256 #ifdef CONFIG_IPV6_MIP6
 257                 struct in6_addr saddr;
 258 #endif
 259                 struct in6_addr daddr;
 260                 char hdrs[0];
 261         } *tmp_ext;
 262
 263         top_iph = (struct ipv6hdr *)skb->data;
 264         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 265
 266         nexthdr = *skb->nh.raw;
 267         *skb->nh.raw = IPPROTO_AH;
 268
 269         /* When there are no extension headers, we only need to save the first
 270          * 8 bytes of the base IP header.
 271          */
 272         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 273
 274         tmp_ext = NULL;
 275         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
 276         if (extlen) {
 277                 extlen += sizeof(*tmp_ext);
 278                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 279                 if (!tmp_ext) {
 280                         err = -ENOMEM;
 281                         goto error;
 282                 }
 283 #ifdef CONFIG_IPV6_MIP6
 284                 memcpy(tmp_ext, &top_iph->saddr, extlen);
 285                 err = ipv6_clear_mutable_options(top_iph,
 286                                                  extlen - sizeof(*tmp_ext) +
 287                                                  sizeof(*top_iph),
 288                                                  XFRM_POLICY_OUT);
 289 #else
 290                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 291                 err = ipv6_clear_mutable_options(top_iph,
 292                                                  extlen - sizeof(*tmp_ext) +
 293                                                  sizeof(*top_iph));
 294 #endif
 295                 if (err)
 296                         goto error_free_iph;
 297         }
 298
 299         ah = (struct ip_auth_hdr *)skb->h.raw;
 300         ah->nexthdr = nexthdr;
 301
 302         top_iph->priority    = 0;
 303         top_iph->flow_lbl[0] = 0;
 304         top_iph->flow_lbl[1] = 0;
 305         top_iph->flow_lbl[2] = 0;
 306         top_iph->hop_limit   = 0;
 307
 308         ahp = x->data;
 309         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
 310                                    ahp->icv_trunc_len) >> 2) - 2;
 311
 312         ah->reserved = 0;
 313         ah->spi = x->id.spi;
 314         ah->seq_no = htonl(++x->replay.oseq);
 315         xfrm_aevent_doreplay(x);
 316         err = ah_mac_digest(ahp, skb, ah->auth_data);
 317         if (err)
 318                 goto error_free_iph;
 319         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 320
 321         err = 0;
 322
 323         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 324         if (tmp_ext) {
 325 #ifdef CONFIG_IPV6_MIP6
 326                 memcpy(&top_iph->saddr, tmp_ext, extlen);
 327 #else
 328                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 329 #endif
 330 error_free_iph:
 331                 kfree(tmp_ext);
 332         }
 333
 334 error:
 335         return err;
 336 }
 337
 338 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 339 {
 340         /*
 341          * Before process AH
 342          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 343          * |<-------------->| hdr_len
 344          *
 345          * To erase AH:
 346          * Keeping copy of cleared headers. After AH processing,
 347          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
 348          * header length. Then copy back the copy as long as hdr_len
 349          * If destination header following AH exists, copy it into after [Ext2].
 350          *
 351          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 352          * There is offset of AH before IPv6 header after the process.
 353          */
 354
 355         struct ipv6_auth_hdr *ah;
 356         struct ah_data *ahp;
 357         unsigned char *tmp_hdr = NULL;
 358         u16 hdr_len;
 359         u16 ah_hlen;
 360         int nexthdr;
 361         int err = -EINVAL;
 362
 363         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 364                 goto out;
 365
 366         /* We are going to _remove_ AH header to keep sockets happy,
 367          * so... Later this can change. */
 368         if (skb_cloned(skb) &&
 369             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 370                 goto out;
 371
 372         hdr_len = skb->data - skb->nh.raw;
 373         ah = (struct ipv6_auth_hdr*)skb->data;
 374         ahp = x->data;
 375         nexthdr = ah->nexthdr;
 376         ah_hlen = (ah->hdrlen + 2) << 2;
 377
 378         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 379             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 380                 goto out;
 381
 382         if (!pskb_may_pull(skb, ah_hlen))
 383                 goto out;
 384
 385         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
 386         if (!tmp_hdr)
 387                 goto out;
 388         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
 389 #ifdef CONFIG_IPV6_MIP6
 390         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len, XFRM_POLICY_IN))
 391                 goto free_out;
 392 #else
 393         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
 394                 goto free_out;
 395 #endif
 396         skb->nh.ipv6h->priority    = 0;
 397         skb->nh.ipv6h->flow_lbl[0] = 0;
 398         skb->nh.ipv6h->flow_lbl[1] = 0;
 399         skb->nh.ipv6h->flow_lbl[2] = 0;
 400         skb->nh.ipv6h->hop_limit   = 0;
 401
 402         {
 403                 u8 auth_data[MAX_AH_AUTH_LEN];
 404
 405                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 406                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 407                 skb_push(skb, hdr_len);
 408                 err = ah_mac_digest(ahp, skb, ah->auth_data);
 409                 if (err)
 410                         goto free_out;
 411                 err = -EINVAL;
 412                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 413                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
 414                         x->stats.integrity_failed++;
 415                         goto free_out;
 416                 }
 417         }
 418
 419         skb->h.raw = memcpy(skb->nh.raw += ah_hlen, tmp_hdr, hdr_len);
 420         __skb_pull(skb, ah_hlen + hdr_len);
 421
 422         kfree(tmp_hdr);
 423
 424         return nexthdr;
 425
 426 free_out:
 427         kfree(tmp_hdr);
 428 out:
 429         return err;
 430 }
 431
 432 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 433                     int type, int code, int offset, __u32 info)
 434 {
 435         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 436         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 437         struct xfrm_state *x;
 438
 439         if (type != ICMPV6_DEST_UNREACH &&
 440             type != ICMPV6_PKT_TOOBIG)
 441                 return;
 442
 443         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 444         if (!x)
 445                 return;
 446
 447         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
 448                  ntohl(ah->spi), NIP6(iph->daddr));
 449
 450         xfrm_state_put(x);
 451 }
 452
 453 static int ah6_init_state(struct xfrm_state *x)
 454 {
 455         struct ah_data *ahp = NULL;
 456         struct xfrm_algo_desc *aalg_desc;
 457         struct crypto_hash *tfm;
 458
 459         if (!x->aalg)
 460                 goto error;
 461
 462         /* null auth can use a zero length key */
 463         if (x->aalg->alg_key_len > 512)
 464                 goto error;
 465
 466         if (x->encap)
 467                 goto error;
 468
 469         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 470         if (ahp == NULL)
 471                 return -ENOMEM;
 472
 473         ahp->key = x->aalg->alg_key;
 474         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 475         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 476         if (IS_ERR(tfm))
 477                 goto error;
 478
 479         ahp->tfm = tfm;
 480         if (crypto_hash_setkey(tfm, ahp->key, ahp->key_len))
 481                 goto error;
 482
 483         /*
 484          * Lookup the algorithm description maintained by xfrm_algo,
 485          * verify crypto transform properties, and store information
 486          * we need for AH processing.  This lookup cannot fail here
 487          * after a successful crypto_alloc_hash().
 488          */
 489         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 490         BUG_ON(!aalg_desc);
 491
 492         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 493             crypto_hash_digestsize(tfm)) {
 494                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 495                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 496                        aalg_desc->uinfo.auth.icv_fullbits/8);
 497                 goto error;
 498         }
 499
 500         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 501         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 502
 503         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 504
 505         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 506         if (!ahp->work_icv)
 507                 goto error;
 508
 509         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 510         if (x->props.mode == XFRM_MODE_TUNNEL)
 511                 x->props.header_len += sizeof(struct ipv6hdr);
 512         x->data = ahp;
 513
 514         return 0;
 515
 516 error:
 517         if (ahp) {
 518                 kfree(ahp->work_icv);
 519                 crypto_free_hash(ahp->tfm);
 520                 kfree(ahp);
 521         }
 522         return -EINVAL;
 523 }
 524
 525 static void ah6_destroy(struct xfrm_state *x)
 526 {
 527         struct ah_data *ahp = x->data;
 528
 529         if (!ahp)
 530                 return;
 531
 532         kfree(ahp->work_icv);
 533         ahp->work_icv = NULL;
 534         crypto_free_hash(ahp->tfm);
 535         ahp->tfm = NULL;
 536         kfree(ahp);
 537 }
 538
 539 static struct xfrm_type ah6_type =
 540 {
 541         .description    = "AH6",
 542         .owner          = THIS_MODULE,
 543         .proto          = IPPROTO_AH,
 544         .init_state     = ah6_init_state,
 545         .destructor     = ah6_destroy,
 546         .input          = ah6_input,
 547         .output         = ah6_output,
 548         .hdr_offset     = xfrm6_find_1stfragopt,
 549 };
 550
 551 static struct inet6_protocol ah6_protocol = {
 552         .handler        =       xfrm6_rcv,
 553         .err_handler    =       ah6_err,
 554         .flags          =       INET6_PROTO_NOPOLICY,
 555 };
 556
 557 static int __init ah6_init(void)
 558 {
 559         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 560                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 561                 return -EAGAIN;
 562         }
 563
 564         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 565                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 566                 xfrm_unregister_type(&ah6_type, AF_INET6);
 567                 return -EAGAIN;
 568         }
 569
 570         return 0;
 571 }
 572
 573 static void __exit ah6_fini(void)
 574 {
 575         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 576                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 577
 578         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 579                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 580
 581 }
 582
 583 module_init(ah6_init);
 584 module_exit(ah6_fini);
 585
 586 MODULE_LICENSE("GPL");