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
  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 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
  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 #else
 136 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt) {}
 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 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
 179 {
 180         union {
 181                 struct ipv6hdr *iph;
 182                 struct ipv6_opt_hdr *opth;
 183                 struct ipv6_rt_hdr *rth;
 184                 char *raw;
 185         } exthdr = { .iph = iph };
 186         char *end = exthdr.raw + len;
 187         int nexthdr = iph->nexthdr;
 188
 189         exthdr.iph++;
 190
 191         while (exthdr.raw < end) {
 192                 switch (nexthdr) {
 193                 case NEXTHDR_DEST:
 194                         if (dir == XFRM_POLICY_OUT)
 195                                 ipv6_rearrange_destopt(iph, exthdr.opth);
 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 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 232                 struct in6_addr saddr;
 233 #endif
 234                 struct in6_addr daddr;
 235                 char hdrs[0];
 236         } *tmp_ext;
 237
 238         skb_push(skb, -skb_network_offset(skb));
 239         top_iph = ipv6_hdr(skb);
 240         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 241
 242         nexthdr = *skb_mac_header(skb);
 243         *skb_mac_header(skb) = IPPROTO_AH;
 244
 245         /* When there are no extension headers, we only need to save the first
 246          * 8 bytes of the base IP header.
 247          */
 248         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 249
 250         tmp_ext = NULL;
 251         extlen = skb_transport_offset(skb) - sizeof(struct ipv6hdr);
 252         if (extlen) {
 253                 extlen += sizeof(*tmp_ext);
 254                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 255                 if (!tmp_ext) {
 256                         err = -ENOMEM;
 257                         goto error;
 258                 }
 259 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 260                 memcpy(tmp_ext, &top_iph->saddr, extlen);
 261 #else
 262                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 263 #endif
 264                 err = ipv6_clear_mutable_options(top_iph,
 265                                                  extlen - sizeof(*tmp_ext) +
 266                                                  sizeof(*top_iph),
 267                                                  XFRM_POLICY_OUT);
 268                 if (err)
 269                         goto error_free_iph;
 270         }
 271
 272         ah = ip_auth_hdr(skb);
 273         ah->nexthdr = nexthdr;
 274
 275         top_iph->priority    = 0;
 276         top_iph->flow_lbl[0] = 0;
 277         top_iph->flow_lbl[1] = 0;
 278         top_iph->flow_lbl[2] = 0;
 279         top_iph->hop_limit   = 0;
 280
 281         ahp = x->data;
 282         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 283
 284         ah->reserved = 0;
 285         ah->spi = x->id.spi;
 286         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
 287
 288         spin_lock_bh(&x->lock);
 289         err = ah_mac_digest(ahp, skb, ah->auth_data);
 290         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 291         spin_unlock_bh(&x->lock);
 292
 293         if (err)
 294                 goto error_free_iph;
 295
 296         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 297         if (tmp_ext) {
 298 #if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 299                 memcpy(&top_iph->saddr, tmp_ext, extlen);
 300 #else
 301                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 302 #endif
 303 error_free_iph:
 304                 kfree(tmp_ext);
 305         }
 306
 307 error:
 308         return err;
 309 }
 310
 311 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 312 {
 313         /*
 314          * Before process AH
 315          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 316          * |<-------------->| hdr_len
 317          *
 318          * To erase AH:
 319          * Keeping copy of cleared headers. After AH processing,
 320          * Moving the pointer of skb->network_header by using skb_pull as long
 321          * as AH header length. Then copy back the copy as long as hdr_len
 322          * If destination header following AH exists, copy it into after [Ext2].
 323          *
 324          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 325          * There is offset of AH before IPv6 header after the process.
 326          */
 327
 328         struct ip_auth_hdr *ah;
 329         struct ipv6hdr *ip6h;
 330         struct ah_data *ahp;
 331         unsigned char *tmp_hdr = NULL;
 332         u16 hdr_len;
 333         u16 ah_hlen;
 334         int nexthdr;
 335         int err = -EINVAL;
 336
 337         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 338                 goto out;
 339
 340         /* We are going to _remove_ AH header to keep sockets happy,
 341          * so... Later this can change. */
 342         if (skb_cloned(skb) &&
 343             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 344                 goto out;
 345
 346         skb->ip_summed = CHECKSUM_NONE;
 347
 348         hdr_len = skb->data - skb_network_header(skb);
 349         ah = (struct ip_auth_hdr *)skb->data;
 350         ahp = x->data;
 351         nexthdr = ah->nexthdr;
 352         ah_hlen = (ah->hdrlen + 2) << 2;
 353
 354         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 355             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 356                 goto out;
 357
 358         if (!pskb_may_pull(skb, ah_hlen))
 359                 goto out;
 360
 361         tmp_hdr = kmemdup(skb_network_header(skb), hdr_len, GFP_ATOMIC);
 362         if (!tmp_hdr)
 363                 goto out;
 364         ip6h = ipv6_hdr(skb);
 365         if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
 366                 goto free_out;
 367         ip6h->priority    = 0;
 368         ip6h->flow_lbl[0] = 0;
 369         ip6h->flow_lbl[1] = 0;
 370         ip6h->flow_lbl[2] = 0;
 371         ip6h->hop_limit   = 0;
 372
 373         spin_lock(&x->lock);
 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 unlock;
 383                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len))
 384                         err = -EBADMSG;
 385         }
 386 unlock:
 387         spin_unlock(&x->lock);
 388
 389         if (err)
 390                 goto free_out;
 391
 392         skb->network_header += ah_hlen;
 393         memcpy(skb_network_header(skb), tmp_hdr, hdr_len);
 394         skb->transport_header = skb->network_header;
 395         __skb_pull(skb, ah_hlen + hdr_len);
 396
 397         kfree(tmp_hdr);
 398
 399         return nexthdr;
 400
 401 free_out:
 402         kfree(tmp_hdr);
 403 out:
 404         return err;
 405 }
 406
 407 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 408                     int type, int code, int offset, __be32 info)
 409 {
 410         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 411         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 412         struct xfrm_state *x;
 413
 414         if (type != ICMPV6_DEST_UNREACH &&
 415             type != ICMPV6_PKT_TOOBIG)
 416                 return;
 417
 418         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 419         if (!x)
 420                 return;
 421
 422         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
 423                  ntohl(ah->spi), NIP6(iph->daddr));
 424
 425         xfrm_state_put(x);
 426 }
 427
 428 static int ah6_init_state(struct xfrm_state *x)
 429 {
 430         struct ah_data *ahp = NULL;
 431         struct xfrm_algo_desc *aalg_desc;
 432         struct crypto_hash *tfm;
 433
 434         if (!x->aalg)
 435                 goto error;
 436
 437         if (x->encap)
 438                 goto error;
 439
 440         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 441         if (ahp == NULL)
 442                 return -ENOMEM;
 443
 444         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 445         if (IS_ERR(tfm))
 446                 goto error;
 447
 448         ahp->tfm = tfm;
 449         if (crypto_hash_setkey(tfm, x->aalg->alg_key,
 450                                (x->aalg->alg_key_len + 7) / 8))
 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 ip_auth_hdr) +
 480                                           ahp->icv_trunc_len);
 481         switch (x->props.mode) {
 482         case XFRM_MODE_BEET:
 483         case XFRM_MODE_TRANSPORT:
 484                 break;
 485         case XFRM_MODE_TUNNEL:
 486                 x->props.header_len += sizeof(struct ipv6hdr);
 487                 break;
 488         default:
 489                 goto error;
 490         }
 491         x->data = ahp;
 492
 493         return 0;
 494
 495 error:
 496         if (ahp) {
 497                 kfree(ahp->work_icv);
 498                 crypto_free_hash(ahp->tfm);
 499                 kfree(ahp);
 500         }
 501         return -EINVAL;
 502 }
 503
 504 static void ah6_destroy(struct xfrm_state *x)
 505 {
 506         struct ah_data *ahp = x->data;
 507
 508         if (!ahp)
 509                 return;
 510
 511         kfree(ahp->work_icv);
 512         ahp->work_icv = NULL;
 513         crypto_free_hash(ahp->tfm);
 514         ahp->tfm = NULL;
 515         kfree(ahp);
 516 }
 517
 518 static const struct xfrm_type ah6_type =
 519 {
 520         .description    = "AH6",
 521         .owner          = THIS_MODULE,
 522         .proto          = IPPROTO_AH,
 523         .flags          = XFRM_TYPE_REPLAY_PROT,
 524         .init_state     = ah6_init_state,
 525         .destructor     = ah6_destroy,
 526         .input          = ah6_input,
 527         .output         = ah6_output,
 528         .hdr_offset     = xfrm6_find_1stfragopt,
 529 };
 530
 531 static struct inet6_protocol ah6_protocol = {
 532         .handler        =       xfrm6_rcv,
 533         .err_handler    =       ah6_err,
 534         .flags          =       INET6_PROTO_NOPOLICY,
 535 };
 536
 537 static int __init ah6_init(void)
 538 {
 539         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 540                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 541                 return -EAGAIN;
 542         }
 543
 544         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 545                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 546                 xfrm_unregister_type(&ah6_type, AF_INET6);
 547                 return -EAGAIN;
 548         }
 549
 550         return 0;
 551 }
 552
 553 static void __exit ah6_fini(void)
 554 {
 555         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 556                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 557
 558         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 559                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 560
 561 }
 562
 563 module_init(ah6_init);
 564 module_exit(ah6_fini);
 565
 566 MODULE_LICENSE("GPL");
 567 MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_AH);