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