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/string.h>
  33 #include <net/icmp.h>
  34 #include <net/ipv6.h>
  35 #include <net/protocol.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(
 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 xfrm_state *x, struct sk_buff *skb)
 158 {
 159         int err;
 160         int extlen;
 161         struct ipv6hdr *top_iph;
 162         struct ip_auth_hdr *ah;
 163         struct ah_data *ahp;
 164         u8 nexthdr;
 165         char tmp_base[8];
 166         struct {
 167                 struct in6_addr daddr;
 168                 char hdrs[0];
 169         } *tmp_ext;
 170
 171         top_iph = (struct ipv6hdr *)skb->data;
 172         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 173
 174         nexthdr = *skb->nh.raw;
 175         *skb->nh.raw = IPPROTO_AH;
 176
 177         /* When there are no extension headers, we only need to save the first
 178          * 8 bytes of the base IP header.
 179          */
 180         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 181
 182         tmp_ext = NULL;
 183         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
 184         if (extlen) {
 185                 extlen += sizeof(*tmp_ext);
 186                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 187                 if (!tmp_ext) {
 188                         err = -ENOMEM;
 189                         goto error;
 190                 }
 191                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 192                 err = ipv6_clear_mutable_options(top_iph,
 193                                                  extlen - sizeof(*tmp_ext) +
 194                                                  sizeof(*top_iph));
 195                 if (err)
 196                         goto error_free_iph;
 197         }
 198
 199         ah = (struct ip_auth_hdr *)skb->h.raw;
 200         ah->nexthdr = nexthdr;
 201
 202         top_iph->priority    = 0;
 203         top_iph->flow_lbl[0] = 0;
 204         top_iph->flow_lbl[1] = 0;
 205         top_iph->flow_lbl[2] = 0;
 206         top_iph->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         xfrm_aevent_doreplay(x);
 216         err = ah_mac_digest(ahp, skb, ah->auth_data);
 217         if (err)
 218                 goto error_free_iph;
 219         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 220
 221         err = 0;
 222
 223         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 224         if (tmp_ext) {
 225                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 226 error_free_iph:
 227                 kfree(tmp_ext);
 228         }
 229
 230 error:
 231         return err;
 232 }
 233
 234 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
 235 {
 236         /*
 237          * Before process AH
 238          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 239          * |<-------------->| hdr_len
 240          *
 241          * To erase AH:
 242          * Keeping copy of cleared headers. After AH processing,
 243          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
 244          * header length. Then copy back the copy as long as hdr_len
 245          * If destination header following AH exists, copy it into after [Ext2].
 246          *
 247          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 248          * There is offset of AH before IPv6 header after the process.
 249          */
 250
 251         struct ipv6_auth_hdr *ah;
 252         struct ah_data *ahp;
 253         unsigned char *tmp_hdr = NULL;
 254         u16 hdr_len;
 255         u16 ah_hlen;
 256         int nexthdr;
 257         int err = -EINVAL;
 258
 259         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 260                 goto out;
 261
 262         /* We are going to _remove_ AH header to keep sockets happy,
 263          * so... Later this can change. */
 264         if (skb_cloned(skb) &&
 265             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 266                 goto out;
 267
 268         hdr_len = skb->data - skb->nh.raw;
 269         ah = (struct ipv6_auth_hdr*)skb->data;
 270         ahp = x->data;
 271         nexthdr = ah->nexthdr;
 272         ah_hlen = (ah->hdrlen + 2) << 2;
 273
 274         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 275             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 276                 goto out;
 277
 278         if (!pskb_may_pull(skb, ah_hlen))
 279                 goto out;
 280
 281         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
 282         if (!tmp_hdr)
 283                 goto out;
 284         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
 285         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
 286                 goto free_out;
 287         skb->nh.ipv6h->priority    = 0;
 288         skb->nh.ipv6h->flow_lbl[0] = 0;
 289         skb->nh.ipv6h->flow_lbl[1] = 0;
 290         skb->nh.ipv6h->flow_lbl[2] = 0;
 291         skb->nh.ipv6h->hop_limit   = 0;
 292
 293         {
 294                 u8 auth_data[MAX_AH_AUTH_LEN];
 295
 296                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 297                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 298                 skb_push(skb, hdr_len);
 299                 err = ah_mac_digest(ahp, skb, ah->auth_data);
 300                 if (err)
 301                         goto free_out;
 302                 err = -EINVAL;
 303                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 304                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
 305                         x->stats.integrity_failed++;
 306                         goto free_out;
 307                 }
 308         }
 309
 310         skb->h.raw = memcpy(skb->nh.raw += ah_hlen, tmp_hdr, hdr_len);
 311         __skb_pull(skb, ah_hlen + hdr_len);
 312
 313         kfree(tmp_hdr);
 314
 315         return nexthdr;
 316
 317 free_out:
 318         kfree(tmp_hdr);
 319 out:
 320         return err;
 321 }
 322
 323 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 324                     int type, int code, int offset, __u32 info)
 325 {
 326         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 327         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 328         struct xfrm_state *x;
 329
 330         if (type != ICMPV6_DEST_UNREACH &&
 331             type != ICMPV6_PKT_TOOBIG)
 332                 return;
 333
 334         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 335         if (!x)
 336                 return;
 337
 338         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\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)
 345 {
 346         struct ah_data *ahp = NULL;
 347         struct xfrm_algo_desc *aalg_desc;
 348         struct crypto_hash *tfm;
 349
 350         if (!x->aalg)
 351                 goto error;
 352
 353         /* null auth can use a zero length key */
 354         if (x->aalg->alg_key_len > 512)
 355                 goto error;
 356
 357         if (x->encap)
 358                 goto error;
 359
 360         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 361         if (ahp == NULL)
 362                 return -ENOMEM;
 363
 364         ahp->key = x->aalg->alg_key;
 365         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 366         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 367         if (IS_ERR(tfm))
 368                 goto error;
 369
 370         ahp->tfm = tfm;
 371         if (crypto_hash_setkey(tfm, ahp->key, ahp->key_len))
 372                 goto error;
 373
 374         /*
 375          * Lookup the algorithm description maintained by xfrm_algo,
 376          * verify crypto transform properties, and store information
 377          * we need for AH processing.  This lookup cannot fail here
 378          * after a successful crypto_alloc_hash().
 379          */
 380         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 381         BUG_ON(!aalg_desc);
 382
 383         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 384             crypto_hash_digestsize(tfm)) {
 385                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 386                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 387                        aalg_desc->uinfo.auth.icv_fullbits/8);
 388                 goto error;
 389         }
 390
 391         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 392         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 393
 394         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 395
 396         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 397         if (!ahp->work_icv)
 398                 goto error;
 399
 400         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 401         if (x->props.mode)
 402                 x->props.header_len += sizeof(struct ipv6hdr);
 403         x->data = ahp;
 404
 405         return 0;
 406
 407 error:
 408         if (ahp) {
 409                 kfree(ahp->work_icv);
 410                 crypto_free_hash(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         kfree(ahp->work_icv);
 424         ahp->work_icv = NULL;
 425         crypto_free_hash(ahp->tfm);
 426         ahp->tfm = NULL;
 427         kfree(ahp);
 428 }
 429
 430 static struct xfrm_type ah6_type =
 431 {
 432         .description    = "AH6",
 433         .owner          = THIS_MODULE,
 434         .proto          = IPPROTO_AH,
 435         .init_state     = ah6_init_state,
 436         .destructor     = ah6_destroy,
 437         .input          = ah6_input,
 438         .output         = ah6_output
 439 };
 440
 441 static struct inet6_protocol ah6_protocol = {
 442         .handler        =       xfrm6_rcv,
 443         .err_handler    =       ah6_err,
 444         .flags          =       INET6_PROTO_NOPOLICY,
 445 };
 446
 447 static int __init ah6_init(void)
 448 {
 449         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 450                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 451                 return -EAGAIN;
 452         }
 453
 454         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 455                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 456                 xfrm_unregister_type(&ah6_type, AF_INET6);
 457                 return -EAGAIN;
 458         }
 459
 460         return 0;
 461 }
 462
 463 static void __exit ah6_fini(void)
 464 {
 465         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 466                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 467
 468         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 469                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 470
 471 }
 472
 473 module_init(ah6_init);
 474 module_exit(ah6_fini);
 475
 476 MODULE_LICENSE("GPL");