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/config.h>
  28 #include <linux/module.h>
  29 #include <net/inet_ecn.h>
  30 #include <net/ip.h>
  31 #include <net/ah.h>
  32 #include <linux/crypto.h>
  33 #include <linux/pfkeyv2.h>
  34 #include <net/icmp.h>
  35 #include <net/ipv6.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 static int ipv6_clear_mutable_options(struct sk_buff *skb, u16 *nh_offset, int dir)
  78 {
  79         u16 offset = sizeof(struct ipv6hdr);
  80         struct ipv6_opt_hdr *exthdr = (struct ipv6_opt_hdr*)(skb->nh.raw + offset);
  81         unsigned int packet_len = skb->tail - skb->nh.raw;
  82         u8 nexthdr = skb->nh.ipv6h->nexthdr;
  83         u8 nextnexthdr = 0;
  84
  85         *nh_offset = ((unsigned char *)&skb->nh.ipv6h->nexthdr) - skb->nh.raw;
  86
  87         while (offset + 1 <= packet_len) {
  88
  89                 switch (nexthdr) {
  90
  91                 case NEXTHDR_HOP:
  92                         *nh_offset = offset;
  93                         offset += ipv6_optlen(exthdr);
  94                         if (!zero_out_mutable_opts(exthdr)) {
  95                                 LIMIT_NETDEBUG(
  96                                 printk(KERN_WARNING "overrun hopopts\n"));
  97                                 return 0;
  98                         }
  99                         nexthdr = exthdr->nexthdr;
 100                         exthdr = (struct ipv6_opt_hdr*)(skb->nh.raw + offset);
 101                         break;
 102
 103                 case NEXTHDR_ROUTING:
 104                         *nh_offset = offset;
 105                         offset += ipv6_optlen(exthdr);
 106                         ((struct ipv6_rt_hdr*)exthdr)->segments_left = 0;
 107                         nexthdr = exthdr->nexthdr;
 108                         exthdr = (struct ipv6_opt_hdr*)(skb->nh.raw + offset);
 109                         break;
 110
 111                 case NEXTHDR_DEST:
 112                         *nh_offset = offset;
 113                         offset += ipv6_optlen(exthdr);
 114                         if (!zero_out_mutable_opts(exthdr))  {
 115                                 LIMIT_NETDEBUG(
 116                                         printk(KERN_WARNING "overrun destopt\n"));
 117                                 return 0;
 118                         }
 119                         nexthdr = exthdr->nexthdr;
 120                         exthdr = (struct ipv6_opt_hdr*)(skb->nh.raw + offset);
 121                         break;
 122
 123                 case NEXTHDR_AUTH:
 124                         if (dir == XFRM_POLICY_OUT) {
 125                                 memset(((struct ipv6_auth_hdr*)exthdr)->auth_data, 0,
 126                                        (((struct ipv6_auth_hdr*)exthdr)->hdrlen - 1) << 2);
 127                         }
 128                         if (exthdr->nexthdr == NEXTHDR_DEST) {
 129                                 offset += (((struct ipv6_auth_hdr*)exthdr)->hdrlen + 2) << 2;
 130                                 exthdr = (struct ipv6_opt_hdr*)(skb->nh.raw + offset);
 131                                 nextnexthdr = exthdr->nexthdr;
 132                                 if (!zero_out_mutable_opts(exthdr)) {
 133                                         LIMIT_NETDEBUG(
 134                                                 printk(KERN_WARNING "overrun destopt\n"));
 135                                         return 0;
 136                                 }
 137                         }
 138                         return nexthdr;
 139                 default :
 140                         return nexthdr;
 141                 }
 142         }
 143
 144         return nexthdr;
 145 }
 146
 147 int ah6_output(struct sk_buff **pskb)
 148 {
 149         int err;
 150         int hdr_len = sizeof(struct ipv6hdr);
 151         struct dst_entry *dst = (*pskb)->dst;
 152         struct xfrm_state *x  = dst->xfrm;
 153         struct ipv6hdr *iph = NULL;
 154         struct ip_auth_hdr *ah;
 155         struct ah_data *ahp;
 156         u16 nh_offset = 0;
 157         u8 nexthdr;
 158
 159         if ((*pskb)->ip_summed == CHECKSUM_HW) {
 160                 err = skb_checksum_help(pskb, 0);
 161                 if (err)
 162                         goto error_nolock;
 163         }
 164
 165         spin_lock_bh(&x->lock);
 166         err = xfrm_check_output(x, *pskb, AF_INET6);
 167         if (err)
 168                 goto error;
 169
 170         if (x->props.mode) {
 171                 iph = (*pskb)->nh.ipv6h;
 172                 (*pskb)->nh.ipv6h = (struct ipv6hdr*)skb_push(*pskb, x->props.header_len);
 173                 (*pskb)->nh.ipv6h->version = 6;
 174                 (*pskb)->nh.ipv6h->payload_len = htons((*pskb)->len - sizeof(struct ipv6hdr));
 175                 (*pskb)->nh.ipv6h->nexthdr = IPPROTO_AH;
 176                 ipv6_addr_copy(&(*pskb)->nh.ipv6h->saddr,
 177                                (struct in6_addr *) &x->props.saddr);
 178                 ipv6_addr_copy(&(*pskb)->nh.ipv6h->daddr,
 179                                (struct in6_addr *) &x->id.daddr);
 180                 ah = (struct ip_auth_hdr*)((*pskb)->nh.ipv6h+1);
 181                 ah->nexthdr = IPPROTO_IPV6;
 182         } else {
 183                 hdr_len = (*pskb)->h.raw - (*pskb)->nh.raw;
 184                 iph = kmalloc(hdr_len, GFP_ATOMIC);
 185                 if (!iph) {
 186                         err = -ENOMEM;
 187                         goto error;
 188                 }
 189                 memcpy(iph, (*pskb)->data, hdr_len);
 190                 (*pskb)->nh.ipv6h = (struct ipv6hdr*)skb_push(*pskb, x->props.header_len);
 191                 memcpy((*pskb)->nh.ipv6h, iph, hdr_len);
 192                 nexthdr = ipv6_clear_mutable_options(*pskb, &nh_offset, XFRM_POLICY_OUT);
 193                 if (nexthdr == 0)
 194                         goto error_free_iph;
 195
 196                 (*pskb)->nh.raw[nh_offset] = IPPROTO_AH;
 197                 (*pskb)->nh.ipv6h->payload_len = htons((*pskb)->len - sizeof(struct ipv6hdr));
 198                 ah = (struct ip_auth_hdr*)((*pskb)->nh.raw+hdr_len);
 199                 (*pskb)->h.raw = (unsigned char*) ah;
 200                 ah->nexthdr = nexthdr;
 201         }
 202
 203         (*pskb)->nh.ipv6h->priority    = 0;
 204         (*pskb)->nh.ipv6h->flow_lbl[0] = 0;
 205         (*pskb)->nh.ipv6h->flow_lbl[1] = 0;
 206         (*pskb)->nh.ipv6h->flow_lbl[2] = 0;
 207         (*pskb)->nh.ipv6h->hop_limit    = 0;
 208
 209         ahp = x->data;
 210         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
 211                                    ahp->icv_trunc_len) >> 2) - 2;
 212
 213         ah->reserved = 0;
 214         ah->spi = x->id.spi;
 215         ah->seq_no = htonl(++x->replay.oseq);
 216         ahp->icv(ahp, *pskb, ah->auth_data);
 217
 218         if (x->props.mode) {
 219                 (*pskb)->nh.ipv6h->hop_limit   = iph->hop_limit;
 220                 (*pskb)->nh.ipv6h->priority    = iph->priority;
 221                 (*pskb)->nh.ipv6h->flow_lbl[0] = iph->flow_lbl[0];
 222                 (*pskb)->nh.ipv6h->flow_lbl[1] = iph->flow_lbl[1];
 223                 (*pskb)->nh.ipv6h->flow_lbl[2] = iph->flow_lbl[2];
 224                 if (x->props.flags & XFRM_STATE_NOECN)
 225                         IP6_ECN_clear((*pskb)->nh.ipv6h);
 226         } else {
 227                 memcpy((*pskb)->nh.ipv6h, iph, hdr_len);
 228                 (*pskb)->nh.raw[nh_offset] = IPPROTO_AH;
 229                 (*pskb)->nh.ipv6h->payload_len = htons((*pskb)->len - sizeof(struct ipv6hdr));
 230                 kfree (iph);
 231         }
 232
 233         (*pskb)->nh.raw = (*pskb)->data;
 234
 235         x->curlft.bytes += (*pskb)->len;
 236         x->curlft.packets++;
 237         spin_unlock_bh(&x->lock);
 238         if (((*pskb)->dst = dst_pop(dst)) == NULL) {
 239                 err = -EHOSTUNREACH;
 240                 goto error_nolock;
 241         }
 242         return NET_XMIT_BYPASS;
 243 error_free_iph:
 244         kfree(iph);
 245 error:
 246         spin_unlock_bh(&x->lock);
 247 error_nolock:
 248         kfree_skb(*pskb);
 249         return err;
 250 }
 251
 252 int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 253 {
 254         /*
 255          * Before process AH
 256          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 257          * |<-------------->| hdr_len
 258          * |<------------------------>| cleared_hlen
 259          *
 260          * To erase AH:
 261          * Keeping copy of cleared headers. After AH processing,
 262          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
 263          * header length. Then copy back the copy as long as hdr_len
 264          * If destination header following AH exists, copy it into after [Ext2].
 265          *
 266          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 267          * There is offset of AH before IPv6 header after the process.
 268          */
 269
 270         struct ipv6_auth_hdr *ah;
 271         struct ah_data *ahp;
 272         unsigned char *tmp_hdr = NULL;
 273         u16 hdr_len;
 274         u16 ah_hlen;
 275         u16 cleared_hlen;
 276         u16 nh_offset = 0;
 277         u8 nexthdr = 0;
 278         u8 *prevhdr;
 279
 280         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 281                 goto out;
 282
 283         /* We are going to _remove_ AH header to keep sockets happy,
 284          * so... Later this can change. */
 285         if (skb_cloned(skb) &&
 286             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 287                 goto out;
 288
 289         hdr_len = skb->data - skb->nh.raw;
 290         cleared_hlen = hdr_len;
 291         ah = (struct ipv6_auth_hdr*)skb->data;
 292         ahp = x->data;
 293         nexthdr = ah->nexthdr;
 294         ah_hlen = (ah->hdrlen + 2) << 2;
 295         cleared_hlen += ah_hlen;
 296
 297         if (nexthdr == NEXTHDR_DEST) {
 298                 struct ipv6_opt_hdr *dsthdr = (struct ipv6_opt_hdr*)(skb->data + ah_hlen);
 299                 cleared_hlen += ipv6_optlen(dsthdr);
 300         }
 301
 302         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 303             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 304                 goto out;
 305
 306         if (!pskb_may_pull(skb, ah_hlen))
 307                 goto out;
 308
 309         tmp_hdr = kmalloc(cleared_hlen, GFP_ATOMIC);
 310         if (!tmp_hdr)
 311                 goto out;
 312         memcpy(tmp_hdr, skb->nh.raw, cleared_hlen);
 313         ipv6_clear_mutable_options(skb, &nh_offset, XFRM_POLICY_IN);
 314         skb->nh.ipv6h->priority    = 0;
 315         skb->nh.ipv6h->flow_lbl[0] = 0;
 316         skb->nh.ipv6h->flow_lbl[1] = 0;
 317         skb->nh.ipv6h->flow_lbl[2] = 0;
 318         skb->nh.ipv6h->hop_limit   = 0;
 319
 320         {
 321                 u8 auth_data[MAX_AH_AUTH_LEN];
 322
 323                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 324                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 325                 skb_push(skb, skb->data - skb->nh.raw);
 326                 ahp->icv(ahp, skb, ah->auth_data);
 327                 if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
 328                         LIMIT_NETDEBUG(
 329                                 printk(KERN_WARNING "ipsec ah authentication error\n"));
 330                         x->stats.integrity_failed++;
 331                         goto free_out;
 332                 }
 333         }
 334
 335         skb->nh.raw = skb_pull(skb, ah_hlen);
 336         memcpy(skb->nh.raw, tmp_hdr, hdr_len);
 337         if (nexthdr == NEXTHDR_DEST) {
 338                 memcpy(skb->nh.raw + hdr_len,
 339                        tmp_hdr + hdr_len + ah_hlen,
 340                        cleared_hlen - hdr_len - ah_hlen);
 341         }
 342         prevhdr = (u8*)(skb->nh.raw + nh_offset);
 343         *prevhdr = nexthdr;
 344         skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 345         skb_pull(skb, hdr_len);
 346         skb->h.raw = skb->data;
 347
 348
 349         kfree(tmp_hdr);
 350
 351         return nexthdr;
 352
 353 free_out:
 354         kfree(tmp_hdr);
 355 out:
 356         return -EINVAL;
 357 }
 358
 359 void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 360          int type, int code, int offset, __u32 info)
 361 {
 362         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 363         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 364         struct xfrm_state *x;
 365
 366         if (type != ICMPV6_DEST_UNREACH &&
 367             type != ICMPV6_PKT_TOOBIG)
 368                 return;
 369
 370         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 371         if (!x)
 372                 return;
 373
 374         NETDEBUG(printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/"
 375                         "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
 376                ntohl(ah->spi), NIP6(iph->daddr)));
 377
 378         xfrm_state_put(x);
 379 }
 380
 381 static int ah6_init_state(struct xfrm_state *x, void *args)
 382 {
 383         struct ah_data *ahp = NULL;
 384         struct xfrm_algo_desc *aalg_desc;
 385
 386         if (!x->aalg)
 387                 goto error;
 388
 389         /* null auth can use a zero length key */
 390         if (x->aalg->alg_key_len > 512)
 391                 goto error;
 392
 393         ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
 394         if (ahp == NULL)
 395                 return -ENOMEM;
 396
 397         memset(ahp, 0, sizeof(*ahp));
 398
 399         ahp->key = x->aalg->alg_key;
 400         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 401         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 402         if (!ahp->tfm)
 403                 goto error;
 404         ahp->icv = ah_hmac_digest;
 405
 406         /*
 407          * Lookup the algorithm description maintained by xfrm_algo,
 408          * verify crypto transform properties, and store information
 409          * we need for AH processing.  This lookup cannot fail here
 410          * after a successful crypto_alloc_tfm().
 411          */
 412         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name);
 413         BUG_ON(!aalg_desc);
 414
 415         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 416             crypto_tfm_alg_digestsize(ahp->tfm)) {
 417                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 418                        x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
 419                        aalg_desc->uinfo.auth.icv_fullbits/8);
 420                 goto error;
 421         }
 422
 423         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 424         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 425
 426         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 427
 428         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 429         if (!ahp->work_icv)
 430                 goto error;
 431
 432         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 433         if (x->props.mode)
 434                 x->props.header_len += sizeof(struct ipv6hdr);
 435         x->data = ahp;
 436
 437         return 0;
 438
 439 error:
 440         if (ahp) {
 441                 if (ahp->work_icv)
 442                         kfree(ahp->work_icv);
 443                 if (ahp->tfm)
 444                         crypto_free_tfm(ahp->tfm);
 445                 kfree(ahp);
 446         }
 447         return -EINVAL;
 448 }
 449
 450 static void ah6_destroy(struct xfrm_state *x)
 451 {
 452         struct ah_data *ahp = x->data;
 453
 454         if (!ahp)
 455                 return;
 456
 457         if (ahp->work_icv) {
 458                 kfree(ahp->work_icv);
 459                 ahp->work_icv = NULL;
 460         }
 461         if (ahp->tfm) {
 462                 crypto_free_tfm(ahp->tfm);
 463                 ahp->tfm = NULL;
 464         }
 465         kfree(ahp);
 466 }
 467
 468 static struct xfrm_type ah6_type =
 469 {
 470         .description    = "AH6",
 471         .owner          = THIS_MODULE,
 472         .proto          = IPPROTO_AH,
 473         .init_state     = ah6_init_state,
 474         .destructor     = ah6_destroy,
 475         .input          = ah6_input,
 476         .output         = ah6_output
 477 };
 478
 479 static struct inet6_protocol ah6_protocol = {
 480         .handler        =       xfrm6_rcv,
 481         .err_handler    =       ah6_err,
 482         .flags          =       INET6_PROTO_NOPOLICY,
 483 };
 484
 485 int __init ah6_init(void)
 486 {
 487         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 488                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 489                 return -EAGAIN;
 490         }
 491
 492         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 493                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 494                 xfrm_unregister_type(&ah6_type, AF_INET6);
 495                 return -EAGAIN;
 496         }
 497
 498         return 0;
 499 }
 500
 501 static void __exit ah6_fini(void)
 502 {
 503         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 504                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 505
 506         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 507                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 508
 509 }
 510
 511 module_init(ah6_init);
 512 module_exit(ah6_fini);
 513
 514 MODULE_LICENSE("GPL");