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/spinlock.h>
  33 #include <linux/string.h>
  34 #include <net/icmp.h>
  35 #include <net/ipv6.h>
  36 #include <net/protocol.h>
  37 #include <net/xfrm.h>
  38 #include <asm/scatterlist.h>
  39
  40 static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
  41 {
  42         u8 *opt = (u8 *)opthdr;
  43         int len = ipv6_optlen(opthdr);
  44         int off = 0;
  45         int optlen = 0;
  46
  47         off += 2;
  48         len -= 2;
  49
  50         while (len > 0) {
  51
  52                 switch (opt[off]) {
  53
  54                 case IPV6_TLV_PAD0:
  55                         optlen = 1;
  56                         break;
  57                 default:
  58                         if (len < 2)
  59                                 goto bad;
  60                         optlen = opt[off+1]+2;
  61                         if (len < optlen)
  62                                 goto bad;
  63                         if (opt[off] & 0x20)
  64                                 memset(&opt[off+2], 0, opt[off+1]);
  65                         break;
  66                 }
  67
  68                 off += optlen;
  69                 len -= optlen;
  70         }
  71         if (len == 0)
  72                 return 1;
  73
  74 bad:
  75         return 0;
  76 }
  77
  78 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
  79 /**
  80  *      ipv6_rearrange_destopt - rearrange IPv6 destination options header
  81  *      @iph: IPv6 header
  82  *      @destopt: destionation options header
  83  */
  84 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
  85 {
  86         u8 *opt = (u8 *)destopt;
  87         int len = ipv6_optlen(destopt);
  88         int off = 0;
  89         int optlen = 0;
  90
  91         off += 2;
  92         len -= 2;
  93
  94         while (len > 0) {
  95
  96                 switch (opt[off]) {
  97
  98                 case IPV6_TLV_PAD0:
  99                         optlen = 1;
 100                         break;
 101                 default:
 102                         if (len < 2)
 103                                 goto bad;
 104                         optlen = opt[off+1]+2;
 105                         if (len < optlen)
 106                                 goto bad;
 107
 108                         /* Rearrange the source address in @iph and the
 109                          * addresses in home address option for final source.
 110                          * See 11.3.2 of RFC 3775 for details.
 111                          */
 112                         if (opt[off] == IPV6_TLV_HAO) {
 113                                 struct in6_addr final_addr;
 114                                 struct ipv6_destopt_hao *hao;
 115
 116                                 hao = (struct ipv6_destopt_hao *)&opt[off];
 117                                 if (hao->length != sizeof(hao->addr)) {
 118                                         if (net_ratelimit())
 119                                                 printk(KERN_WARNING "destopt hao: invalid header length: %u\n", hao->length);
 120                                         goto bad;
 121                                 }
 122                                 ipv6_addr_copy(&final_addr, &hao->addr);
 123                                 ipv6_addr_copy(&hao->addr, &iph->saddr);
 124                                 ipv6_addr_copy(&iph->saddr, &final_addr);
 125                         }
 126                         break;
 127                 }
 128
 129                 off += optlen;
 130                 len -= optlen;
 131         }
 132         /* Note: ok if len == 0 */
 133 bad:
 134         return;
 135 }
 136 #else
 137 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt) {}
 138 #endif
 139
 140 /**
 141  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
 142  *      @iph: IPv6 header
 143  *      @rthdr: routing header
 144  *
 145  *      Rearrange the destination address in @iph and the addresses in @rthdr
 146  *      so that they appear in the order they will at the final destination.
 147  *      See Appendix A2 of RFC 2402 for details.
 148  */
 149 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
 150 {
 151         int segments, segments_left;
 152         struct in6_addr *addrs;
 153         struct in6_addr final_addr;
 154
 155         segments_left = rthdr->segments_left;
 156         if (segments_left == 0)
 157                 return;
 158         rthdr->segments_left = 0;
 159
 160         /* The value of rthdr->hdrlen has been verified either by the system
 161          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
 162          * packets.  So we can assume that it is even and that segments is
 163          * greater than or equal to segments_left.
 164          *
 165          * For the same reason we can assume that this option is of type 0.
 166          */
 167         segments = rthdr->hdrlen >> 1;
 168
 169         addrs = ((struct rt0_hdr *)rthdr)->addr;
 170         ipv6_addr_copy(&final_addr, addrs + segments - 1);
 171
 172         addrs += segments - segments_left;
 173         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
 174
 175         ipv6_addr_copy(addrs, &iph->daddr);
 176         ipv6_addr_copy(&iph->daddr, &final_addr);
 177 }
 178
 179 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
 180 {
 181         union {
 182                 struct ipv6hdr *iph;
 183                 struct ipv6_opt_hdr *opth;
 184                 struct ipv6_rt_hdr *rth;
 185                 char *raw;
 186         } exthdr = { .iph = iph };
 187         char *end = exthdr.raw + len;
 188         int nexthdr = iph->nexthdr;
 189
 190         exthdr.iph++;
 191
 192         while (exthdr.raw < end) {
 193                 switch (nexthdr) {
 194                 case NEXTHDR_DEST:
 195                         if (dir == XFRM_POLICY_OUT)
 196                                 ipv6_rearrange_destopt(iph, exthdr.opth);
 197                 case NEXTHDR_HOP:
 198                         if (!zero_out_mutable_opts(exthdr.opth)) {
 199                                 LIMIT_NETDEBUG(
 200                                         KERN_WARNING "overrun %sopts\n",
 201                                         nexthdr == NEXTHDR_HOP ?
 202                                                 "hop" : "dest");
 203                                 return -EINVAL;
 204                         }
 205                         break;
 206
 207                 case NEXTHDR_ROUTING:
 208                         ipv6_rearrange_rthdr(iph, exthdr.rth);
 209                         break;
 210
 211                 default :
 212                         return 0;
 213                 }
 214
 215                 nexthdr = exthdr.opth->nexthdr;
 216                 exthdr.raw += ipv6_optlen(exthdr.opth);
 217         }
 218
 219         return 0;
 220 }
 221
 222 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 223 {
 224         int err;
 225         int extlen;
 226         struct ipv6hdr *top_iph;
 227         struct ip_auth_hdr *ah;
 228         struct ah_data *ahp;
 229         u8 nexthdr;
 230         char tmp_base[8];
 231         struct {
 232 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 233                 struct in6_addr saddr;
 234 #endif
 235                 struct in6_addr daddr;
 236                 char hdrs[0];
 237         } *tmp_ext;
 238
 239         skb_push(skb, -skb_network_offset(skb));
 240         top_iph = ipv6_hdr(skb);
 241         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 242
 243         nexthdr = *skb_mac_header(skb);
 244         *skb_mac_header(skb) = IPPROTO_AH;
 245
 246         /* When there are no extension headers, we only need to save the first
 247          * 8 bytes of the base IP header.
 248          */
 249         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 250
 251         tmp_ext = NULL;
 252         extlen = skb_transport_offset(skb) - sizeof(struct ipv6hdr);
 253         if (extlen) {
 254                 extlen += sizeof(*tmp_ext);
 255                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 256                 if (!tmp_ext) {
 257                         err = -ENOMEM;
 258                         goto error;
 259                 }
 260 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 261                 memcpy(tmp_ext, &top_iph->saddr, extlen);
 262 #else
 263                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 264 #endif
 265                 err = ipv6_clear_mutable_options(top_iph,
 266                                                  extlen - sizeof(*tmp_ext) +
 267                                                  sizeof(*top_iph),
 268                                                  XFRM_POLICY_OUT);
 269                 if (err)
 270                         goto error_free_iph;
 271         }
 272
 273         ah = ip_auth_hdr(skb);
 274         ah->nexthdr = nexthdr;
 275
 276         top_iph->priority    = 0;
 277         top_iph->flow_lbl[0] = 0;
 278         top_iph->flow_lbl[1] = 0;
 279         top_iph->flow_lbl[2] = 0;
 280         top_iph->hop_limit   = 0;
 281
 282         ahp = x->data;
 283         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 284
 285         ah->reserved = 0;
 286         ah->spi = x->id.spi;
 287         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
 288
 289         spin_lock_bh(&x->lock);
 290         err = ah_mac_digest(ahp, skb, ah->auth_data);
 291         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 292         spin_unlock_bh(&x->lock);
 293
 294         if (err)
 295                 goto error_free_iph;
 296
 297         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 298         if (tmp_ext) {
 299 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 300                 memcpy(&top_iph->saddr, tmp_ext, extlen);
 301 #else
 302                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 303 #endif
 304 error_free_iph:
 305                 kfree(tmp_ext);
 306         }
 307
 308 error:
 309         return err;
 310 }
 311
 312 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 313 {
 314         /*
 315          * Before process AH
 316          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 317          * |<-------------->| hdr_len
 318          *
 319          * To erase AH:
 320          * Keeping copy of cleared headers. After AH processing,
 321          * Moving the pointer of skb->network_header by using skb_pull as long
 322          * as AH header length. Then copy back the copy as long as hdr_len
 323          * If destination header following AH exists, copy it into after [Ext2].
 324          *
 325          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 326          * There is offset of AH before IPv6 header after the process.
 327          */
 328
 329         struct ip_auth_hdr *ah;
 330         struct ipv6hdr *ip6h;
 331         struct ah_data *ahp;
 332         unsigned char *tmp_hdr = NULL;
 333         u16 hdr_len;
 334         u16 ah_hlen;
 335         int nexthdr;
 336         int err = -EINVAL;
 337
 338         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 339                 goto out;
 340
 341         /* We are going to _remove_ AH header to keep sockets happy,
 342          * so... Later this can change. */
 343         if (skb_cloned(skb) &&
 344             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 345                 goto out;
 346
 347         skb->ip_summed = CHECKSUM_NONE;
 348
 349         hdr_len = skb->data - skb_network_header(skb);
 350         ah = (struct ip_auth_hdr *)skb->data;
 351         ahp = x->data;
 352         nexthdr = ah->nexthdr;
 353         ah_hlen = (ah->hdrlen + 2) << 2;
 354
 355         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 356             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 357                 goto out;
 358
 359         if (!pskb_may_pull(skb, ah_hlen))
 360                 goto out;
 361
 362         tmp_hdr = kmemdup(skb_network_header(skb), hdr_len, GFP_ATOMIC);
 363         if (!tmp_hdr)
 364                 goto out;
 365         ip6h = ipv6_hdr(skb);
 366         if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
 367                 goto free_out;
 368         ip6h->priority    = 0;
 369         ip6h->flow_lbl[0] = 0;
 370         ip6h->flow_lbl[1] = 0;
 371         ip6h->flow_lbl[2] = 0;
 372         ip6h->hop_limit   = 0;
 373
 374         {
 375                 u8 auth_data[MAX_AH_AUTH_LEN];
 376
 377                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 378                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 379                 skb_push(skb, hdr_len);
 380                 err = ah_mac_digest(ahp, skb, ah->auth_data);
 381                 if (err)
 382                         goto free_out;
 383                 err = -EINVAL;
 384                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 385                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
 386                         x->stats.integrity_failed++;
 387                         goto free_out;
 388                 }
 389         }
 390
 391         skb->network_header += ah_hlen;
 392         memcpy(skb_network_header(skb), tmp_hdr, hdr_len);
 393         skb->transport_header = skb->network_header;
 394         __skb_pull(skb, ah_hlen + hdr_len);
 395
 396         kfree(tmp_hdr);
 397
 398         return nexthdr;
 399
 400 free_out:
 401         kfree(tmp_hdr);
 402 out:
 403         return err;
 404 }
 405
 406 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 407                     int type, int code, int offset, __be32 info)
 408 {
 409         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 410         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 411         struct xfrm_state *x;
 412
 413         if (type != ICMPV6_DEST_UNREACH &&
 414             type != ICMPV6_PKT_TOOBIG)
 415                 return;
 416
 417         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 418         if (!x)
 419                 return;
 420
 421         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
 422                  ntohl(ah->spi), NIP6(iph->daddr));
 423
 424         xfrm_state_put(x);
 425 }
 426
 427 static int ah6_init_state(struct xfrm_state *x)
 428 {
 429         struct ah_data *ahp = NULL;
 430         struct xfrm_algo_desc *aalg_desc;
 431         struct crypto_hash *tfm;
 432
 433         if (!x->aalg)
 434                 goto error;
 435
 436         if (x->encap)
 437                 goto error;
 438
 439         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 440         if (ahp == NULL)
 441                 return -ENOMEM;
 442
 443         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 444         if (IS_ERR(tfm))
 445                 goto error;
 446
 447         ahp->tfm = tfm;
 448         if (crypto_hash_setkey(tfm, x->aalg->alg_key,
 449                                (x->aalg->alg_key_len + 7) / 8))
 450                 goto error;
 451
 452         /*
 453          * Lookup the algorithm description maintained by xfrm_algo,
 454          * verify crypto transform properties, and store information
 455          * we need for AH processing.  This lookup cannot fail here
 456          * after a successful crypto_alloc_hash().
 457          */
 458         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 459         BUG_ON(!aalg_desc);
 460
 461         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 462             crypto_hash_digestsize(tfm)) {
 463                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 464                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 465                        aalg_desc->uinfo.auth.icv_fullbits/8);
 466                 goto error;
 467         }
 468
 469         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 470         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 471
 472         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 473
 474         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 475         if (!ahp->work_icv)
 476                 goto error;
 477
 478         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 479                                           ahp->icv_trunc_len);
 480         switch (x->props.mode) {
 481         case XFRM_MODE_BEET:
 482         case XFRM_MODE_TRANSPORT:
 483                 break;
 484         case XFRM_MODE_TUNNEL:
 485                 x->props.header_len += sizeof(struct ipv6hdr);
 486         default:
 487                 goto error;
 488         }
 489         x->data = ahp;
 490
 491         return 0;
 492
 493 error:
 494         if (ahp) {
 495                 kfree(ahp->work_icv);
 496                 crypto_free_hash(ahp->tfm);
 497                 kfree(ahp);
 498         }
 499         return -EINVAL;
 500 }
 501
 502 static void ah6_destroy(struct xfrm_state *x)
 503 {
 504         struct ah_data *ahp = x->data;
 505
 506         if (!ahp)
 507                 return;
 508
 509         kfree(ahp->work_icv);
 510         ahp->work_icv = NULL;
 511         crypto_free_hash(ahp->tfm);
 512         ahp->tfm = NULL;
 513         kfree(ahp);
 514 }
 515
 516 static struct xfrm_type ah6_type =
 517 {
 518         .description    = "AH6",
 519         .owner          = THIS_MODULE,
 520         .proto          = IPPROTO_AH,
 521         .flags          = XFRM_TYPE_REPLAY_PROT,
 522         .init_state     = ah6_init_state,
 523         .destructor     = ah6_destroy,
 524         .input          = ah6_input,
 525         .output         = ah6_output,
 526         .hdr_offset     = xfrm6_find_1stfragopt,
 527 };
 528
 529 static struct inet6_protocol ah6_protocol = {
 530         .handler        =       xfrm6_rcv,
 531         .err_handler    =       ah6_err,
 532         .flags          =       INET6_PROTO_NOPOLICY,
 533 };
 534
 535 static int __init ah6_init(void)
 536 {
 537         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 538                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 539                 return -EAGAIN;
 540         }
 541
 542         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 543                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 544                 xfrm_unregister_type(&ah6_type, AF_INET6);
 545                 return -EAGAIN;
 546         }
 547
 548         return 0;
 549 }
 550
 551 static void __exit ah6_fini(void)
 552 {
 553         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 554                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 555
 556         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 557                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 558
 559 }
 560
 561 module_init(ah6_init);
 562 module_exit(ah6_fini);
 563
 564 MODULE_LICENSE("GPL");
 565 MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_AH);