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/protocol.h>
  37 #include <net/xfrm.h>
  38 #include <asm/scatterlist.h>
  39
  40 static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
  41 {
  42         u8 *opt = (u8 *)opthdr;
  43         int len = ipv6_optlen(opthdr);
  44         int off = 0;
  45         int optlen = 0;
  46
  47         off += 2;
  48         len -= 2;
  49
  50         while (len > 0) {
  51
  52                 switch (opt[off]) {
  53
  54                 case IPV6_TLV_PAD0:
  55                         optlen = 1;
  56                         break;
  57                 default:
  58                         if (len < 2)
  59                                 goto bad;
  60                         optlen = opt[off+1]+2;
  61                         if (len < optlen)
  62                                 goto bad;
  63                         if (opt[off] & 0x20)
  64                                 memset(&opt[off+2], 0, opt[off+1]);
  65                         break;
  66                 }
  67
  68                 off += optlen;
  69                 len -= optlen;
  70         }
  71         if (len == 0)
  72                 return 1;
  73
  74 bad:
  75         return 0;
  76 }
  77
  78 /**
  79  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
  80  *      @iph: IPv6 header
  81  *      @rthdr: routing header
  82  *
  83  *      Rearrange the destination address in @iph and the addresses in @rthdr
  84  *      so that they appear in the order they will at the final destination.
  85  *      See Appendix A2 of RFC 2402 for details.
  86  */
  87 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
  88 {
  89         int segments, segments_left;
  90         struct in6_addr *addrs;
  91         struct in6_addr final_addr;
  92
  93         segments_left = rthdr->segments_left;
  94         if (segments_left == 0)
  95                 return;
  96         rthdr->segments_left = 0;
  97
  98         /* The value of rthdr->hdrlen has been verified either by the system
  99          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
 100          * packets.  So we can assume that it is even and that segments is
 101          * greater than or equal to segments_left.
 102          *
 103          * For the same reason we can assume that this option is of type 0.
 104          */
 105         segments = rthdr->hdrlen >> 1;
 106
 107         addrs = ((struct rt0_hdr *)rthdr)->addr;
 108         ipv6_addr_copy(&final_addr, addrs + segments - 1);
 109
 110         addrs += segments - segments_left;
 111         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
 112
 113         ipv6_addr_copy(addrs, &iph->daddr);
 114         ipv6_addr_copy(&iph->daddr, &final_addr);
 115 }
 116
 117 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len)
 118 {
 119         union {
 120                 struct ipv6hdr *iph;
 121                 struct ipv6_opt_hdr *opth;
 122                 struct ipv6_rt_hdr *rth;
 123                 char *raw;
 124         } exthdr = { .iph = iph };
 125         char *end = exthdr.raw + len;
 126         int nexthdr = iph->nexthdr;
 127
 128         exthdr.iph++;
 129
 130         while (exthdr.raw < end) {
 131                 switch (nexthdr) {
 132                 case NEXTHDR_HOP:
 133                 case NEXTHDR_DEST:
 134                         if (!zero_out_mutable_opts(exthdr.opth)) {
 135                                 LIMIT_NETDEBUG(
 136                                         KERN_WARNING "overrun %sopts\n",
 137                                         nexthdr == NEXTHDR_HOP ?
 138                                                 "hop" : "dest");
 139                                 return -EINVAL;
 140                         }
 141                         break;
 142
 143                 case NEXTHDR_ROUTING:
 144                         ipv6_rearrange_rthdr(iph, exthdr.rth);
 145                         break;
 146
 147                 default :
 148                         return 0;
 149                 }
 150
 151                 nexthdr = exthdr.opth->nexthdr;
 152                 exthdr.raw += ipv6_optlen(exthdr.opth);
 153         }
 154
 155         return 0;
 156 }
 157
 158 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
 159 {
 160         int err;
 161         int extlen;
 162         struct ipv6hdr *top_iph;
 163         struct ip_auth_hdr *ah;
 164         struct ah_data *ahp;
 165         u8 nexthdr;
 166         char tmp_base[8];
 167         struct {
 168                 struct in6_addr daddr;
 169                 char hdrs[0];
 170         } *tmp_ext;
 171
 172         top_iph = (struct ipv6hdr *)skb->data;
 173         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
 174
 175         nexthdr = *skb->nh.raw;
 176         *skb->nh.raw = IPPROTO_AH;
 177
 178         /* When there are no extension headers, we only need to save the first
 179          * 8 bytes of the base IP header.
 180          */
 181         memcpy(tmp_base, top_iph, sizeof(tmp_base));
 182
 183         tmp_ext = NULL;
 184         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
 185         if (extlen) {
 186                 extlen += sizeof(*tmp_ext);
 187                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
 188                 if (!tmp_ext) {
 189                         err = -ENOMEM;
 190                         goto error;
 191                 }
 192                 memcpy(tmp_ext, &top_iph->daddr, extlen);
 193                 err = ipv6_clear_mutable_options(top_iph,
 194                                                  extlen - sizeof(*tmp_ext) +
 195                                                  sizeof(*top_iph));
 196                 if (err)
 197                         goto error_free_iph;
 198         }
 199
 200         ah = (struct ip_auth_hdr *)skb->h.raw;
 201         ah->nexthdr = nexthdr;
 202
 203         top_iph->priority    = 0;
 204         top_iph->flow_lbl[0] = 0;
 205         top_iph->flow_lbl[1] = 0;
 206         top_iph->flow_lbl[2] = 0;
 207         top_iph->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, skb, ah->auth_data);
 217
 218         err = 0;
 219
 220         memcpy(top_iph, tmp_base, sizeof(tmp_base));
 221         if (tmp_ext) {
 222                 memcpy(&top_iph->daddr, tmp_ext, extlen);
 223 error_free_iph:
 224                 kfree(tmp_ext);
 225         }
 226
 227 error:
 228         return err;
 229 }
 230
 231 static int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 232 {
 233         /*
 234          * Before process AH
 235          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
 236          * |<-------------->| hdr_len
 237          *
 238          * To erase AH:
 239          * Keeping copy of cleared headers. After AH processing,
 240          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
 241          * header length. Then copy back the copy as long as hdr_len
 242          * If destination header following AH exists, copy it into after [Ext2].
 243          *
 244          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
 245          * There is offset of AH before IPv6 header after the process.
 246          */
 247
 248         struct ipv6_auth_hdr *ah;
 249         struct ah_data *ahp;
 250         unsigned char *tmp_hdr = NULL;
 251         u16 hdr_len;
 252         u16 ah_hlen;
 253         int nexthdr;
 254
 255         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 256                 goto out;
 257
 258         /* We are going to _remove_ AH header to keep sockets happy,
 259          * so... Later this can change. */
 260         if (skb_cloned(skb) &&
 261             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 262                 goto out;
 263
 264         hdr_len = skb->data - skb->nh.raw;
 265         ah = (struct ipv6_auth_hdr*)skb->data;
 266         ahp = x->data;
 267         nexthdr = ah->nexthdr;
 268         ah_hlen = (ah->hdrlen + 2) << 2;
 269
 270         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
 271             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
 272                 goto out;
 273
 274         if (!pskb_may_pull(skb, ah_hlen))
 275                 goto out;
 276
 277         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
 278         if (!tmp_hdr)
 279                 goto out;
 280         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
 281         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
 282                 goto out;
 283         skb->nh.ipv6h->priority    = 0;
 284         skb->nh.ipv6h->flow_lbl[0] = 0;
 285         skb->nh.ipv6h->flow_lbl[1] = 0;
 286         skb->nh.ipv6h->flow_lbl[2] = 0;
 287         skb->nh.ipv6h->hop_limit   = 0;
 288
 289         {
 290                 u8 auth_data[MAX_AH_AUTH_LEN];
 291
 292                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 293                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
 294                 skb_push(skb, skb->data - skb->nh.raw);
 295                 ahp->icv(ahp, skb, ah->auth_data);
 296                 if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
 297                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
 298                         x->stats.integrity_failed++;
 299                         goto free_out;
 300                 }
 301         }
 302
 303         skb->nh.raw = skb_pull(skb, ah_hlen);
 304         memcpy(skb->nh.raw, tmp_hdr, hdr_len);
 305         skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 306         skb_pull(skb, hdr_len);
 307         skb->h.raw = skb->data;
 308
 309
 310         kfree(tmp_hdr);
 311
 312         return nexthdr;
 313
 314 free_out:
 315         kfree(tmp_hdr);
 316 out:
 317         return -EINVAL;
 318 }
 319
 320 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 321                     int type, int code, int offset, __u32 info)
 322 {
 323         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
 324         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 325         struct xfrm_state *x;
 326
 327         if (type != ICMPV6_DEST_UNREACH &&
 328             type != ICMPV6_PKT_TOOBIG)
 329                 return;
 330
 331         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
 332         if (!x)
 333                 return;
 334
 335         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
 336                  ntohl(ah->spi), NIP6(iph->daddr));
 337
 338         xfrm_state_put(x);
 339 }
 340
 341 static int ah6_init_state(struct xfrm_state *x)
 342 {
 343         struct ah_data *ahp = NULL;
 344         struct xfrm_algo_desc *aalg_desc;
 345
 346         if (!x->aalg)
 347                 goto error;
 348
 349         /* null auth can use a zero length key */
 350         if (x->aalg->alg_key_len > 512)
 351                 goto error;
 352
 353         if (x->encap)
 354                 goto error;
 355
 356         ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
 357         if (ahp == NULL)
 358                 return -ENOMEM;
 359
 360         memset(ahp, 0, sizeof(*ahp));
 361
 362         ahp->key = x->aalg->alg_key;
 363         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 364         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 365         if (!ahp->tfm)
 366                 goto error;
 367         ahp->icv = ah_hmac_digest;
 368
 369         /*
 370          * Lookup the algorithm description maintained by xfrm_algo,
 371          * verify crypto transform properties, and store information
 372          * we need for AH processing.  This lookup cannot fail here
 373          * after a successful crypto_alloc_tfm().
 374          */
 375         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 376         BUG_ON(!aalg_desc);
 377
 378         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 379             crypto_tfm_alg_digestsize(ahp->tfm)) {
 380                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 381                        x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
 382                        aalg_desc->uinfo.auth.icv_fullbits/8);
 383                 goto error;
 384         }
 385
 386         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 387         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 388
 389         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 390
 391         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 392         if (!ahp->work_icv)
 393                 goto error;
 394
 395         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
 396         if (x->props.mode)
 397                 x->props.header_len += sizeof(struct ipv6hdr);
 398         x->data = ahp;
 399
 400         return 0;
 401
 402 error:
 403         if (ahp) {
 404                 kfree(ahp->work_icv);
 405                 crypto_free_tfm(ahp->tfm);
 406                 kfree(ahp);
 407         }
 408         return -EINVAL;
 409 }
 410
 411 static void ah6_destroy(struct xfrm_state *x)
 412 {
 413         struct ah_data *ahp = x->data;
 414
 415         if (!ahp)
 416                 return;
 417
 418         kfree(ahp->work_icv);
 419         ahp->work_icv = NULL;
 420         crypto_free_tfm(ahp->tfm);
 421         ahp->tfm = NULL;
 422         kfree(ahp);
 423 }
 424
 425 static struct xfrm_type ah6_type =
 426 {
 427         .description    = "AH6",
 428         .owner          = THIS_MODULE,
 429         .proto          = IPPROTO_AH,
 430         .init_state     = ah6_init_state,
 431         .destructor     = ah6_destroy,
 432         .input          = ah6_input,
 433         .output         = ah6_output
 434 };
 435
 436 static struct inet6_protocol ah6_protocol = {
 437         .handler        =       xfrm6_rcv,
 438         .err_handler    =       ah6_err,
 439         .flags          =       INET6_PROTO_NOPOLICY,
 440 };
 441
 442 static int __init ah6_init(void)
 443 {
 444         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
 445                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
 446                 return -EAGAIN;
 447         }
 448
 449         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
 450                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
 451                 xfrm_unregister_type(&ah6_type, AF_INET6);
 452                 return -EAGAIN;
 453         }
 454
 455         return 0;
 456 }
 457
 458 static void __exit ah6_fini(void)
 459 {
 460         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
 461                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
 462
 463         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
 464                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
 465
 466 }
 467
 468 module_init(ah6_init);
 469 module_exit(ah6_fini);
 470
 471 MODULE_LICENSE("GPL");