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