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/ip.h>
  30 #include <net/ah.h>
  31 #include <linux/crypto.h>
  32 #include <linux/pfkeyv2.h>
  33 #include <linux/string.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 /**
  78  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
  79  *      @iph: IPv6 header
  80  *      @rthdr: routing header
  81  *
  82  *      Rearrange the destination address in @iph and the addresses in @rthdr
  83  *      so that they appear in the order they will at the final destination.
  84  *      See Appendix A2 of RFC 2402 for details.
  85  */
  86 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
  87 {
  88         int segments, segments_left;
  89         struct in6_addr *addrs;
  90         struct in6_addr final_addr;
  91
  92         segments_left = rthdr->segments_left;
  93         if (segments_left == 0)
  94                 return;
  95         rthdr->segments_left = 0;
  96
  97         /* The value of rthdr->hdrlen has been verified either by the system
  98          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
  99          * packets.  So we can assume that it is even and that segments is
 100          * greater than or equal to segments_left.
 101          *
 102          * For the same reason we can assume that this option is of type 0.
 103          */
 104         segments = rthdr->hdrlen >> 1;
 105
 106         addrs = ((struct rt0_hdr *)rthdr)->addr;
 107         ipv6_addr_copy(&final_addr, addrs + segments - 1);
 108
 109         addrs += segments - segments_left;
 110         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
 111
 112         ipv6_addr_copy(addrs, &iph->daddr);
 113         ipv6_addr_copy(&iph->daddr, &final_addr);
 114 }
 115
 116 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len)
 117 {
 118         union {
 119                 struct ipv6hdr *iph;
 120                 struct ipv6_opt_hdr *opth;
 121                 struct ipv6_rt_hdr *rth;
 122                 char *raw;
 123         } exthdr = { .iph = iph };
 124         char *end = exthdr.raw + len;
 125         int nexthdr = iph->nexthdr;
 126
 127         exthdr.iph++;
 128
 129         while (exthdr.raw < end) {
 130                 switch (nexthdr) {
 131                 case NEXTHDR_HOP:
 132                 case NEXTHDR_DEST:
 133                         if (!zero_out_mutable_opts(exthdr.opth)) {
 134                                 LIMIT_NETDEBUG(printk(
 135                                         KERN_WARNING "overrun %sopts\n",
 136                                         nexthdr == NEXTHDR_HOP ?
 137                                                 "hop" : "dest"));
 138                                 return -EINVAL;
 139                         }
 140                         break;
 141
 142                 case NEXTHDR_ROUTING:
 143                         ipv6_rearrange_rthdr(iph, exthdr.rth);
 144                         break;
 145
 146                 default :
 147                         return 0;
 148                 }
 149
 150                 nexthdr = exthdr.opth->nexthdr;
 151                 exthdr.raw += ipv6_optlen(exthdr.opth);
 152         }
 153
 154         return 0;
 155 }
 156
 157 static int ah6_output(struct sk_buff *skb)
 158 {
 159         int err;
 160         int extlen;
 161         struct dst_entry *dst = skb->dst;
 162         struct xfrm_state *x  = dst->xfrm;
 163         struct ipv6hdr *top_iph;
 164         struct ip_auth_hdr *ah;
 165         struct ah_data *ahp;
 166         u8 nexthdr;
 167         char tmp_base[8];
 168         struct {
 169                 struct in6_addr daddr;
 170                 char hdrs[0];
 171         } *tmp_ext;
 172
 173         top_iph = (struct ipv6hdr *)skb->data;
 174         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 175
 176         nexthdr = *skb->nh.raw;
 177         *skb->nh.raw = IPPROTO_AH;
 178
 179         /* When there are no extension headers, we only need to save the first
 180          * 8 bytes of the base IP header.
 181          */
 182         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 183
 184         tmp_ext = NULL;
 185         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
 186         if (extlen) {
 187                 extlen += sizeof(*tmp_ext);
 188                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 189                 if (!tmp_ext) {
 190                         err = -ENOMEM;
 191                         goto error;
 192                 }
 193                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 194                 err = ipv6_clear_mutable_options(top_iph,
 195                                                  extlen - sizeof(*tmp_ext) +
 196                                                  sizeof(*top_iph));
 197                 if (err)
 198                         goto error_free_iph;
 199         }
 200
 201         ah = (struct ip_auth_hdr *)skb->h.raw;
 202         ah->nexthdr = nexthdr;
 203
 204         top_iph->priority    = 0;
 205         top_iph->flow_lbl[0] = 0;
 206         top_iph->flow_lbl[1] = 0;
 207         top_iph->flow_lbl[2] = 0;
 208         top_iph->hop_limit   = 0;
 209
 210         ahp = x->data;
 211         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
 212                                    ahp->icv_trunc_len) >> 2) - 2;
 213
 214         ah->reserved = 0;
 215         ah->spi = x->id.spi;
 216         ah->seq_no = htonl(++x->replay.oseq);
 217         ahp->icv(ahp, skb, ah->auth_data);
 218
 219         err = 0;
 220
 221         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 222         if (tmp_ext) {
 223                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 224 error_free_iph:
 225                 kfree(tmp_ext);
 226         }
 227
 228 error:
 229         return err;
 230 }
 231
 232 static int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 233 {
 234         /*
 235          * Before process AH
 236          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 237          * |<-------------->| hdr_len
 238          *
 239          * To erase AH:
 240          * Keeping copy of cleared headers. After AH processing,
 241          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
 242          * header length. Then copy back the copy as long as hdr_len
 243          * If destination header following AH exists, copy it into after [Ext2].
 244          *
 245          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 246          * There is offset of AH before IPv6 header after the process.
 247          */
 248
 249         struct ipv6_auth_hdr *ah;
 250         struct ah_data *ahp;
 251         unsigned char *tmp_hdr = NULL;
 252         u16 hdr_len;
 253         u16 ah_hlen;
 254         int nexthdr;
 255
 256         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 257                 goto out;
 258
 259         /* We are going to _remove_ AH header to keep sockets happy,
 260          * so... Later this can change. */
 261         if (skb_cloned(skb) &&
 262             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 263                 goto out;
 264
 265         hdr_len = skb->data - skb->nh.raw;
 266         ah = (struct ipv6_auth_hdr*)skb->data;
 267         ahp = x->data;
 268         nexthdr = ah->nexthdr;
 269         ah_hlen = (ah->hdrlen + 2) << 2;
 270
 271         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 272             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 273                 goto out;
 274
 275         if (!pskb_may_pull(skb, ah_hlen))
 276                 goto out;
 277
 278         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
 279         if (!tmp_hdr)
 280                 goto out;
 281         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
 282         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
 283                 goto out;
 284         skb->nh.ipv6h->priority    = 0;
 285         skb->nh.ipv6h->flow_lbl[0] = 0;
 286         skb->nh.ipv6h->flow_lbl[1] = 0;
 287         skb->nh.ipv6h->flow_lbl[2] = 0;
 288         skb->nh.ipv6h->hop_limit   = 0;
 289
 290         {
 291                 u8 auth_data[MAX_AH_AUTH_LEN];
 292
 293                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 294                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 295                 skb_push(skb, skb->data - skb->nh.raw);
 296                 ahp->icv(ahp, skb, ah->auth_data);
 297                 if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
 298                         LIMIT_NETDEBUG(
 299                                 printk(KERN_WARNING "ipsec ah authentication error\n"));
 300                         x->stats.integrity_failed++;
 301                         goto free_out;
 302                 }
 303         }
 304
 305         skb->nh.raw = skb_pull(skb, ah_hlen);
 306         memcpy(skb->nh.raw, tmp_hdr, hdr_len);
 307         skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 308         skb_pull(skb, hdr_len);
 309         skb->h.raw = skb->data;
 310
 311
 312         kfree(tmp_hdr);
 313
 314         return nexthdr;
 315
 316 free_out:
 317         kfree(tmp_hdr);
 318 out:
 319         return -EINVAL;
 320 }
 321
 322 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 323                     int type, int code, int offset, __u32 info)
 324 {
 325         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 326         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 327         struct xfrm_state *x;
 328
 329         if (type != ICMPV6_DEST_UNREACH &&
 330             type != ICMPV6_PKT_TOOBIG)
 331                 return;
 332
 333         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 334         if (!x)
 335                 return;
 336
 337         NETDEBUG(printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/"
 338                         "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
 339                ntohl(ah->spi), NIP6(iph->daddr)));
 340
 341         xfrm_state_put(x);
 342 }
 343
 344 static int ah6_init_state(struct xfrm_state *x, void *args)
 345 {
 346         struct ah_data *ahp = NULL;
 347         struct xfrm_algo_desc *aalg_desc;
 348
 349         if (!x->aalg)
 350                 goto error;
 351
 352         /* null auth can use a zero length key */
 353         if (x->aalg->alg_key_len > 512)
 354                 goto error;
 355
 356         if (x->encap)
 357                 goto error;
 358
 359         ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
 360         if (ahp == NULL)
 361                 return -ENOMEM;
 362
 363         memset(ahp, 0, sizeof(*ahp));
 364
 365         ahp->key = x->aalg->alg_key;
 366         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 367         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 368         if (!ahp->tfm)
 369                 goto error;
 370         ahp->icv = ah_hmac_digest;
 371
 372         /*
 373          * Lookup the algorithm description maintained by xfrm_algo,
 374          * verify crypto transform properties, and store information
 375          * we need for AH processing.  This lookup cannot fail here
 376          * after a successful crypto_alloc_tfm().
 377          */
 378         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name);
 379         BUG_ON(!aalg_desc);
 380
 381         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 382             crypto_tfm_alg_digestsize(ahp->tfm)) {
 383                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 384                        x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
 385                        aalg_desc->uinfo.auth.icv_fullbits/8);
 386                 goto error;
 387         }
 388
 389         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 390         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 391
 392         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 393
 394         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 395         if (!ahp->work_icv)
 396                 goto error;
 397
 398         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 399         if (x->props.mode)
 400                 x->props.header_len += sizeof(struct ipv6hdr);
 401         x->data = ahp;
 402
 403         return 0;
 404
 405 error:
 406         if (ahp) {
 407                 if (ahp->work_icv)
 408                         kfree(ahp->work_icv);
 409                 if (ahp->tfm)
 410                         crypto_free_tfm(ahp->tfm);
 411                 kfree(ahp);
 412         }
 413         return -EINVAL;
 414 }
 415
 416 static void ah6_destroy(struct xfrm_state *x)
 417 {
 418         struct ah_data *ahp = x->data;
 419
 420         if (!ahp)
 421                 return;
 422
 423         if (ahp->work_icv) {
 424                 kfree(ahp->work_icv);
 425                 ahp->work_icv = NULL;
 426         }
 427         if (ahp->tfm) {
 428                 crypto_free_tfm(ahp->tfm);
 429                 ahp->tfm = NULL;
 430         }
 431         kfree(ahp);
 432 }
 433
 434 static struct xfrm_type ah6_type =
 435 {
 436         .description    = "AH6",
 437         .owner          = THIS_MODULE,
 438         .proto          = IPPROTO_AH,
 439         .init_state     = ah6_init_state,
 440         .destructor     = ah6_destroy,
 441         .input          = ah6_input,
 442         .output         = ah6_output
 443 };
 444
 445 static struct inet6_protocol ah6_protocol = {
 446         .handler        =       xfrm6_rcv,
 447         .err_handler    =       ah6_err,
 448         .flags          =       INET6_PROTO_NOPOLICY,
 449 };
 450
 451 static int __init ah6_init(void)
 452 {
 453         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 454                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 455                 return -EAGAIN;
 456         }
 457
 458         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 459                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 460                 xfrm_unregister_type(&ah6_type, AF_INET6);
 461                 return -EAGAIN;
 462         }
 463
 464         return 0;
 465 }
 466
 467 static void __exit ah6_fini(void)
 468 {
 469         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 470                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 471
 472         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 473                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 474
 475 }
 476
 477 module_init(ah6_init);
 478 module_exit(ah6_fini);
 479
 480 MODULE_LICENSE("GPL");