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         /* Note: ok if len == 0 */
 132 bad:
 133         return;
 134 }
 135 #endif
 136
 137 /**
 138  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
 139  *      @iph: IPv6 header
 140  *      @rthdr: routing header
 141  *
 142  *      Rearrange the destination address in @iph and the addresses in @rthdr
 143  *      so that they appear in the order they will at the final destination.
 144  *      See Appendix A2 of RFC 2402 for details.
 145  */
 146 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
 147 {
 148         int segments, segments_left;
 149         struct in6_addr *addrs;
 150         struct in6_addr final_addr;
 151
 152         segments_left = rthdr->segments_left;
 153         if (segments_left == 0)
 154                 return;
 155         rthdr->segments_left = 0;
 156
 157         /* The value of rthdr->hdrlen has been verified either by the system
 158          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
 159          * packets.  So we can assume that it is even and that segments is
 160          * greater than or equal to segments_left.
 161          *
 162          * For the same reason we can assume that this option is of type 0.
 163          */
 164         segments = rthdr->hdrlen >> 1;
 165
 166         addrs = ((struct rt0_hdr *)rthdr)->addr;
 167         ipv6_addr_copy(&final_addr, addrs + segments - 1);
 168
 169         addrs += segments - segments_left;
 170         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
 171
 172         ipv6_addr_copy(addrs, &iph->daddr);
 173         ipv6_addr_copy(&iph->daddr, &final_addr);
 174 }
 175
 176 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
 177 {
 178         union {
 179                 struct ipv6hdr *iph;
 180                 struct ipv6_opt_hdr *opth;
 181                 struct ipv6_rt_hdr *rth;
 182                 char *raw;
 183         } exthdr = { .iph = iph };
 184         char *end = exthdr.raw + len;
 185         int nexthdr = iph->nexthdr;
 186
 187         exthdr.iph++;
 188
 189         while (exthdr.raw < end) {
 190                 switch (nexthdr) {
 191                 case NEXTHDR_DEST:
 192 #ifdef CONFIG_IPV6_MIP6
 193                         if (dir == XFRM_POLICY_OUT)
 194                                 ipv6_rearrange_destopt(iph, exthdr.opth);
 195 #endif
 196                 case NEXTHDR_HOP:
 197                         if (!zero_out_mutable_opts(exthdr.opth)) {
 198                                 LIMIT_NETDEBUG(
 199                                         KERN_WARNING "overrun %sopts\n",
 200                                         nexthdr == NEXTHDR_HOP ?
 201                                                 "hop" : "dest");
 202                                 return -EINVAL;
 203                         }
 204                         break;
 205
 206                 case NEXTHDR_ROUTING:
 207                         ipv6_rearrange_rthdr(iph, exthdr.rth);
 208                         break;
 209
 210                 default :
 211                         return 0;
 212                 }
 213
 214                 nexthdr = exthdr.opth->nexthdr;
 215                 exthdr.raw += ipv6_optlen(exthdr.opth);
 216         }
 217
 218         return 0;
 219 }
 220
 221 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 222 {
 223         int err;
 224         int extlen;
 225         struct ipv6hdr *top_iph;
 226         struct ip_auth_hdr *ah;
 227         struct ah_data *ahp;
 228         u8 nexthdr;
 229         char tmp_base[8];
 230         struct {
 231 #ifdef CONFIG_IPV6_MIP6
 232                 struct in6_addr saddr;
 233 #endif
 234                 struct in6_addr daddr;
 235                 char hdrs[0];
 236         } *tmp_ext;
 237
 238         top_iph = (struct ipv6hdr *)skb->data;
 239         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 240
 241         nexthdr = *skb_network_header(skb);
 242         *skb_network_header(skb) = IPPROTO_AH;
 243
 244         /* When there are no extension headers, we only need to save the first
 245          * 8 bytes of the base IP header.
 246          */
 247         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 248
 249         tmp_ext = NULL;
 250         extlen = skb_transport_offset(skb) + sizeof(struct ipv6hdr);
 251         if (extlen) {
 252                 extlen += sizeof(*tmp_ext);
 253                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 254                 if (!tmp_ext) {
 255                         err = -ENOMEM;
 256                         goto error;
 257                 }
 258 #ifdef CONFIG_IPV6_MIP6
 259                 memcpy(tmp_ext, &top_iph->saddr, extlen);
 260 #else
 261                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 262 #endif
 263                 err = ipv6_clear_mutable_options(top_iph,
 264                                                  extlen - sizeof(*tmp_ext) +
 265                                                  sizeof(*top_iph),
 266                                                  XFRM_POLICY_OUT);
 267                 if (err)
 268                         goto error_free_iph;
 269         }
 270
 271         ah = (struct ip_auth_hdr *)skb_transport_header(skb);
 272         ah->nexthdr = nexthdr;
 273
 274         top_iph->priority    = 0;
 275         top_iph->flow_lbl[0] = 0;
 276         top_iph->flow_lbl[1] = 0;
 277         top_iph->flow_lbl[2] = 0;
 278         top_iph->hop_limit   = 0;
 279
 280         ahp = x->data;
 281         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
 282                                    ahp->icv_trunc_len) >> 2) - 2;
 283
 284         ah->reserved = 0;
 285         ah->spi = x->id.spi;
 286         ah->seq_no = htonl(++x->replay.oseq);
 287         xfrm_aevent_doreplay(x);
 288         err = ah_mac_digest(ahp, skb, ah->auth_data);
 289         if (err)
 290                 goto error_free_iph;
 291         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 292
 293         err = 0;
 294
 295         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 296         if (tmp_ext) {
 297 #ifdef CONFIG_IPV6_MIP6
 298                 memcpy(&top_iph->saddr, tmp_ext, extlen);
 299 #else
 300                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 301 #endif
 302 error_free_iph:
 303                 kfree(tmp_ext);
 304         }
 305
 306 error:
 307         return err;
 308 }
 309
 310 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 311 {
 312         /*
 313          * Before process AH
 314          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 315          * |<-------------->| hdr_len
 316          *
 317          * To erase AH:
 318          * Keeping copy of cleared headers. After AH processing,
 319          * Moving the pointer of skb->network_header by using skb_pull as long
 320          * as AH header length. Then copy back the copy as long as hdr_len
 321          * If destination header following AH exists, copy it into after [Ext2].
 322          *
 323          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 324          * There is offset of AH before IPv6 header after the process.
 325          */
 326
 327         struct ipv6_auth_hdr *ah;
 328         struct ipv6hdr *ip6h;
 329         struct ah_data *ahp;
 330         unsigned char *tmp_hdr = NULL;
 331         u16 hdr_len;
 332         u16 ah_hlen;
 333         int nexthdr;
 334         int err = -EINVAL;
 335
 336         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 337                 goto out;
 338
 339         /* We are going to _remove_ AH header to keep sockets happy,
 340          * so... Later this can change. */
 341         if (skb_cloned(skb) &&
 342             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 343                 goto out;
 344
 345         hdr_len = skb->data - skb_network_header(skb);
 346         ah = (struct ipv6_auth_hdr*)skb->data;
 347         ahp = x->data;
 348         nexthdr = ah->nexthdr;
 349         ah_hlen = (ah->hdrlen + 2) << 2;
 350
 351         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 352             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 353                 goto out;
 354
 355         if (!pskb_may_pull(skb, ah_hlen))
 356                 goto out;
 357
 358         tmp_hdr = kmemdup(skb_network_header(skb), hdr_len, GFP_ATOMIC);
 359         if (!tmp_hdr)
 360                 goto out;
 361         ip6h = ipv6_hdr(skb);
 362         if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
 363                 goto free_out;
 364         ip6h->priority    = 0;
 365         ip6h->flow_lbl[0] = 0;
 366         ip6h->flow_lbl[1] = 0;
 367         ip6h->flow_lbl[2] = 0;
 368         ip6h->hop_limit   = 0;
 369
 370         {
 371                 u8 auth_data[MAX_AH_AUTH_LEN];
 372
 373                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 374                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 375                 skb_push(skb, hdr_len);
 376                 err = ah_mac_digest(ahp, skb, ah->auth_data);
 377                 if (err)
 378                         goto free_out;
 379                 err = -EINVAL;
 380                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 381                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
 382                         x->stats.integrity_failed++;
 383                         goto free_out;
 384                 }
 385         }
 386
 387         skb->network_header += ah_hlen;
 388         memcpy(skb_network_header(skb), tmp_hdr, hdr_len);
 389         skb->transport_header = skb->network_header;
 390         __skb_pull(skb, ah_hlen + hdr_len);
 391
 392         kfree(tmp_hdr);
 393
 394         return nexthdr;
 395
 396 free_out:
 397         kfree(tmp_hdr);
 398 out:
 399         return err;
 400 }
 401
 402 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 403                     int type, int code, int offset, __be32 info)
 404 {
 405         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 406         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 407         struct xfrm_state *x;
 408
 409         if (type != ICMPV6_DEST_UNREACH &&
 410             type != ICMPV6_PKT_TOOBIG)
 411                 return;
 412
 413         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 414         if (!x)
 415                 return;
 416
 417         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
 418                  ntohl(ah->spi), NIP6(iph->daddr));
 419
 420         xfrm_state_put(x);
 421 }
 422
 423 static int ah6_init_state(struct xfrm_state *x)
 424 {
 425         struct ah_data *ahp = NULL;
 426         struct xfrm_algo_desc *aalg_desc;
 427         struct crypto_hash *tfm;
 428
 429         if (!x->aalg)
 430                 goto error;
 431
 432         /* null auth can use a zero length key */
 433         if (x->aalg->alg_key_len > 512)
 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         ahp->key = x->aalg->alg_key;
 444         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 445         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 446         if (IS_ERR(tfm))
 447                 goto error;
 448
 449         ahp->tfm = tfm;
 450         if (crypto_hash_setkey(tfm, ahp->key, ahp->key_len))
 451                 goto error;
 452
 453         /*
 454          * Lookup the algorithm description maintained by xfrm_algo,
 455          * verify crypto transform properties, and store information
 456          * we need for AH processing.  This lookup cannot fail here
 457          * after a successful crypto_alloc_hash().
 458          */
 459         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 460         BUG_ON(!aalg_desc);
 461
 462         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 463             crypto_hash_digestsize(tfm)) {
 464                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 465                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 466                        aalg_desc->uinfo.auth.icv_fullbits/8);
 467                 goto error;
 468         }
 469
 470         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 471         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 472
 473         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 474
 475         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 476         if (!ahp->work_icv)
 477                 goto error;
 478
 479         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 480         if (x->props.mode == XFRM_MODE_TUNNEL)
 481                 x->props.header_len += sizeof(struct ipv6hdr);
 482         x->data = ahp;
 483
 484         return 0;
 485
 486 error:
 487         if (ahp) {
 488                 kfree(ahp->work_icv);
 489                 crypto_free_hash(ahp->tfm);
 490                 kfree(ahp);
 491         }
 492         return -EINVAL;
 493 }
 494
 495 static void ah6_destroy(struct xfrm_state *x)
 496 {
 497         struct ah_data *ahp = x->data;
 498
 499         if (!ahp)
 500                 return;
 501
 502         kfree(ahp->work_icv);
 503         ahp->work_icv = NULL;
 504         crypto_free_hash(ahp->tfm);
 505         ahp->tfm = NULL;
 506         kfree(ahp);
 507 }
 508
 509 static struct xfrm_type ah6_type =
 510 {
 511         .description    = "AH6",
 512         .owner          = THIS_MODULE,
 513         .proto          = IPPROTO_AH,
 514         .init_state     = ah6_init_state,
 515         .destructor     = ah6_destroy,
 516         .input          = ah6_input,
 517         .output         = ah6_output,
 518         .hdr_offset     = xfrm6_find_1stfragopt,
 519 };
 520
 521 static struct inet6_protocol ah6_protocol = {
 522         .handler        =       xfrm6_rcv,
 523         .err_handler    =       ah6_err,
 524         .flags          =       INET6_PROTO_NOPOLICY,
 525 };
 526
 527 static int __init ah6_init(void)
 528 {
 529         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 530                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 531                 return -EAGAIN;
 532         }
 533
 534         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 535                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 536                 xfrm_unregister_type(&ah6_type, AF_INET6);
 537                 return -EAGAIN;
 538         }
 539
 540         return 0;
 541 }
 542
 543 static void __exit ah6_fini(void)
 544 {
 545         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 546                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 547
 548         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 549                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 550
 551 }
 552
 553 module_init(ah6_init);
 554 module_exit(ah6_fini);
 555
 556 MODULE_LICENSE("GPL");