net/ipv4/ah4.c

   1 #define pr_fmt(fmt) "IPsec: " fmt
   2
   3 #include <crypto/algapi.h>
   4 #include <crypto/hash.h>
   5 #include <linux/err.h>
   6 #include <linux/module.h>
   7 #include <linux/slab.h>
   8 #include <net/ip.h>
   9 #include <net/xfrm.h>
  10 #include <net/ah.h>
  11 #include <linux/crypto.h>
  12 #include <linux/pfkeyv2.h>
  13 #include <linux/scatterlist.h>
  14 #include <net/icmp.h>
  15 #include <net/protocol.h>
  16
  17 struct ah_skb_cb {
  18         struct xfrm_skb_cb xfrm;
  19         void *tmp;
  20 };
  21
  22 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
  23
  24 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
  25                           unsigned int size)
  26 {
  27         unsigned int len;
  28
  29         len = size + crypto_ahash_digestsize(ahash) +
  30               (crypto_ahash_alignmask(ahash) &
  31                ~(crypto_tfm_ctx_alignment() - 1));
  32
  33         len = ALIGN(len, crypto_tfm_ctx_alignment());
  34
  35         len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
  36         len = ALIGN(len, __alignof__(struct scatterlist));
  37
  38         len += sizeof(struct scatterlist) * nfrags;
  39
  40         return kmalloc(len, GFP_ATOMIC);
  41 }
  42
  43 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
  44 {
  45         return tmp + offset;
  46 }
  47
  48 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
  49                              unsigned int offset)
  50 {
  51         return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
  52 }
  53
  54 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
  55                                                u8 *icv)
  56 {
  57         struct ahash_request *req;
  58
  59         req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
  60                                 crypto_tfm_ctx_alignment());
  61
  62         ahash_request_set_tfm(req, ahash);
  63
  64         return req;
  65 }
  66
  67 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  68                                              struct ahash_request *req)
  69 {
  70         return (void *)ALIGN((unsigned long)(req + 1) +
  71                              crypto_ahash_reqsize(ahash),
  72                              __alignof__(struct scatterlist));
  73 }
  74
  75 /* Clear mutable options and find final destination to substitute
  76  * into IP header for icv calculation. Options are already checked
  77  * for validity, so paranoia is not required. */
  78
  79 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
  80 {
  81         unsigned char *optptr = (unsigned char *)(iph+1);
  82         int  l = iph->ihl*4 - sizeof(struct iphdr);
  83         int  optlen;
  84
  85         while (l > 0) {
  86                 switch (*optptr) {
  87                 case IPOPT_END:
  88                         return 0;
  89                 case IPOPT_NOOP:
  90                         l--;
  91                         optptr++;
  92                         continue;
  93                 }
  94                 optlen = optptr[1];
  95                 if (optlen<2 || optlen>l)
  96                         return -EINVAL;
  97                 switch (*optptr) {
  98                 case IPOPT_SEC:
  99                 case 0x85:      /* Some "Extended Security" crap. */
 100                 case IPOPT_CIPSO:
 101                 case IPOPT_RA:
 102                 case 0x80|21:   /* RFC1770 */
 103                         break;
 104                 case IPOPT_LSRR:
 105                 case IPOPT_SSRR:
 106                         if (optlen < 6)
 107                                 return -EINVAL;
 108                         memcpy(daddr, optptr+optlen-4, 4);
 109                         /* Fall through */
 110                 default:
 111                         memset(optptr, 0, optlen);
 112                 }
 113                 l -= optlen;
 114                 optptr += optlen;
 115         }
 116         return 0;
 117 }
 118
 119 static void ah_output_done(struct crypto_async_request *base, int err)
 120 {
 121         u8 *icv;
 122         struct iphdr *iph;
 123         struct sk_buff *skb = base->data;
 124         struct xfrm_state *x = skb_dst(skb)->xfrm;
 125         struct ah_data *ahp = x->data;
 126         struct iphdr *top_iph = ip_hdr(skb);
 127         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 128         int ihl = ip_hdrlen(skb);
 129
 130         iph = AH_SKB_CB(skb)->tmp;
 131         icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 132         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 133
 134         top_iph->tos = iph->tos;
 135         top_iph->ttl = iph->ttl;
 136         top_iph->frag_off = iph->frag_off;
 137         if (top_iph->ihl != 5) {
 138                 top_iph->daddr = iph->daddr;
 139                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 140         }
 141
 142         kfree(AH_SKB_CB(skb)->tmp);
 143         xfrm_output_resume(skb, err);
 144 }
 145
 146 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 147 {
 148         int err;
 149         int nfrags;
 150         int ihl;
 151         u8 *icv;
 152         struct sk_buff *trailer;
 153         struct crypto_ahash *ahash;
 154         struct ahash_request *req;
 155         struct scatterlist *sg;
 156         struct iphdr *iph, *top_iph;
 157         struct ip_auth_hdr *ah;
 158         struct ah_data *ahp;
 159         int seqhi_len = 0;
 160         __be32 *seqhi;
 161         int sglists = 0;
 162         struct scatterlist *seqhisg;
 163
 164         ahp = x->data;
 165         ahash = ahp->ahash;
 166
 167         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 168                 goto out;
 169         nfrags = err;
 170
 171         skb_push(skb, -skb_network_offset(skb));
 172         ah = ip_auth_hdr(skb);
 173         ihl = ip_hdrlen(skb);
 174
 175         if (x->props.flags & XFRM_STATE_ESN) {
 176                 sglists = 1;
 177                 seqhi_len = sizeof(*seqhi);
 178         }
 179         err = -ENOMEM;
 180         iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
 181         if (!iph)
 182                 goto out;
 183         seqhi = (__be32 *)((char *)iph + ihl);
 184         icv = ah_tmp_icv(ahash, seqhi, seqhi_len);
 185         req = ah_tmp_req(ahash, icv);
 186         sg = ah_req_sg(ahash, req);
 187         seqhisg = sg + nfrags;
 188
 189         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 190
 191         top_iph = ip_hdr(skb);
 192
 193         iph->tos = top_iph->tos;
 194         iph->ttl = top_iph->ttl;
 195         iph->frag_off = top_iph->frag_off;
 196
 197         if (top_iph->ihl != 5) {
 198                 iph->daddr = top_iph->daddr;
 199                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 200                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 201                 if (err)
 202                         goto out_free;
 203         }
 204
 205         ah->nexthdr = *skb_mac_header(skb);
 206         *skb_mac_header(skb) = IPPROTO_AH;
 207
 208         top_iph->tos = 0;
 209         top_iph->tot_len = htons(skb->len);
 210         top_iph->frag_off = 0;
 211         top_iph->ttl = 0;
 212         top_iph->check = 0;
 213
 214         if (x->props.flags & XFRM_STATE_ALIGN4)
 215                 ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 216         else
 217                 ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 218
 219         ah->reserved = 0;
 220         ah->spi = x->id.spi;
 221         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 222
 223         sg_init_table(sg, nfrags + sglists);
 224         err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 225         if (unlikely(err < 0))
 226                 goto out_free;
 227
 228         if (x->props.flags & XFRM_STATE_ESN) {
 229                 /* Attach seqhi sg right after packet payload */
 230                 *seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
 231                 sg_set_buf(seqhisg, seqhi, seqhi_len);
 232         }
 233         ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 234         ahash_request_set_callback(req, 0, ah_output_done, skb);
 235
 236         AH_SKB_CB(skb)->tmp = iph;
 237
 238         err = crypto_ahash_digest(req);
 239         if (err) {
 240                 if (err == -EINPROGRESS)
 241                         goto out;
 242
 243                 if (err == -ENOSPC)
 244                         err = NET_XMIT_DROP;
 245                 goto out_free;
 246         }
 247
 248         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 249
 250         top_iph->tos = iph->tos;
 251         top_iph->ttl = iph->ttl;
 252         top_iph->frag_off = iph->frag_off;
 253         if (top_iph->ihl != 5) {
 254                 top_iph->daddr = iph->daddr;
 255                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 256         }
 257
 258 out_free:
 259         kfree(iph);
 260 out:
 261         return err;
 262 }
 263
 264 static void ah_input_done(struct crypto_async_request *base, int err)
 265 {
 266         u8 *auth_data;
 267         u8 *icv;
 268         struct iphdr *work_iph;
 269         struct sk_buff *skb = base->data;
 270         struct xfrm_state *x = xfrm_input_state(skb);
 271         struct ah_data *ahp = x->data;
 272         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 273         int ihl = ip_hdrlen(skb);
 274         int ah_hlen = (ah->hdrlen + 2) << 2;
 275
 276         if (err)
 277                 goto out;
 278
 279         work_iph = AH_SKB_CB(skb)->tmp;
 280         auth_data = ah_tmp_auth(work_iph, ihl);
 281         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 282
 283         err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
 284         if (err)
 285                 goto out;
 286
 287         err = ah->nexthdr;
 288
 289         skb->network_header += ah_hlen;
 290         memcpy(skb_network_header(skb), work_iph, ihl);
 291         __skb_pull(skb, ah_hlen + ihl);
 292
 293         if (x->props.mode == XFRM_MODE_TUNNEL)
 294                 skb_reset_transport_header(skb);
 295         else
 296                 skb_set_transport_header(skb, -ihl);
 297 out:
 298         kfree(AH_SKB_CB(skb)->tmp);
 299         xfrm_input_resume(skb, err);
 300 }
 301
 302 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 303 {
 304         int ah_hlen;
 305         int ihl;
 306         int nexthdr;
 307         int nfrags;
 308         u8 *auth_data;
 309         u8 *icv;
 310         struct sk_buff *trailer;
 311         struct crypto_ahash *ahash;
 312         struct ahash_request *req;
 313         struct scatterlist *sg;
 314         struct iphdr *iph, *work_iph;
 315         struct ip_auth_hdr *ah;
 316         struct ah_data *ahp;
 317         int err = -ENOMEM;
 318         int seqhi_len = 0;
 319         __be32 *seqhi;
 320         int sglists = 0;
 321         struct scatterlist *seqhisg;
 322
 323         if (!pskb_may_pull(skb, sizeof(*ah)))
 324                 goto out;
 325
 326         ah = (struct ip_auth_hdr *)skb->data;
 327         ahp = x->data;
 328         ahash = ahp->ahash;
 329
 330         nexthdr = ah->nexthdr;
 331         ah_hlen = (ah->hdrlen + 2) << 2;
 332
 333         if (x->props.flags & XFRM_STATE_ALIGN4) {
 334                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 335                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 336                         goto out;
 337         } else {
 338                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 339                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 340                         goto out;
 341         }
 342
 343         if (!pskb_may_pull(skb, ah_hlen))
 344                 goto out;
 345
 346         /* We are going to _remove_ AH header to keep sockets happy,
 347          * so... Later this can change. */
 348         if (skb_unclone(skb, GFP_ATOMIC))
 349                 goto out;
 350
 351         skb->ip_summed = CHECKSUM_NONE;
 352
 353
 354         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 355                 goto out;
 356         nfrags = err;
 357
 358         ah = (struct ip_auth_hdr *)skb->data;
 359         iph = ip_hdr(skb);
 360         ihl = ip_hdrlen(skb);
 361
 362         if (x->props.flags & XFRM_STATE_ESN) {
 363                 sglists = 1;
 364                 seqhi_len = sizeof(*seqhi);
 365         }
 366
 367         work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
 368                                 ahp->icv_trunc_len + seqhi_len);
 369         if (!work_iph) {
 370                 err = -ENOMEM;
 371                 goto out;
 372         }
 373
 374         seqhi = (__be32 *)((char *)work_iph + ihl);
 375         auth_data = ah_tmp_auth(seqhi, seqhi_len);
 376         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 377         req = ah_tmp_req(ahash, icv);
 378         sg = ah_req_sg(ahash, req);
 379         seqhisg = sg + nfrags;
 380
 381         memcpy(work_iph, iph, ihl);
 382         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 383         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 384
 385         iph->ttl = 0;
 386         iph->tos = 0;
 387         iph->frag_off = 0;
 388         iph->check = 0;
 389         if (ihl > sizeof(*iph)) {
 390                 __be32 dummy;
 391                 err = ip_clear_mutable_options(iph, &dummy);
 392                 if (err)
 393                         goto out_free;
 394         }
 395
 396         skb_push(skb, ihl);
 397
 398         sg_init_table(sg, nfrags + sglists);
 399         err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 400         if (unlikely(err < 0))
 401                 goto out_free;
 402
 403         if (x->props.flags & XFRM_STATE_ESN) {
 404                 /* Attach seqhi sg right after packet payload */
 405                 *seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
 406                 sg_set_buf(seqhisg, seqhi, seqhi_len);
 407         }
 408         ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 409         ahash_request_set_callback(req, 0, ah_input_done, skb);
 410
 411         AH_SKB_CB(skb)->tmp = work_iph;
 412
 413         err = crypto_ahash_digest(req);
 414         if (err) {
 415                 if (err == -EINPROGRESS)
 416                         goto out;
 417
 418                 goto out_free;
 419         }
 420
 421         err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
 422         if (err)
 423                 goto out_free;
 424
 425         skb->network_header += ah_hlen;
 426         memcpy(skb_network_header(skb), work_iph, ihl);
 427         __skb_pull(skb, ah_hlen + ihl);
 428         if (x->props.mode == XFRM_MODE_TUNNEL)
 429                 skb_reset_transport_header(skb);
 430         else
 431                 skb_set_transport_header(skb, -ihl);
 432
 433         err = nexthdr;
 434
 435 out_free:
 436         kfree (work_iph);
 437 out:
 438         return err;
 439 }
 440
 441 static int ah4_err(struct sk_buff *skb, u32 info)
 442 {
 443         struct net *net = dev_net(skb->dev);
 444         const struct iphdr *iph = (const struct iphdr *)skb->data;
 445         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 446         struct xfrm_state *x;
 447
 448         switch (icmp_hdr(skb)->type) {
 449         case ICMP_DEST_UNREACH:
 450                 if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 451                         return 0;
 452         case ICMP_REDIRECT:
 453                 break;
 454         default:
 455                 return 0;
 456         }
 457
 458         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 459                               ah->spi, IPPROTO_AH, AF_INET);
 460         if (!x)
 461                 return 0;
 462
 463         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
 464                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_AH, 0);
 465         else
 466                 ipv4_redirect(skb, net, 0, 0, IPPROTO_AH, 0);
 467         xfrm_state_put(x);
 468
 469         return 0;
 470 }
 471
 472 static int ah_init_state(struct xfrm_state *x)
 473 {
 474         struct ah_data *ahp = NULL;
 475         struct xfrm_algo_desc *aalg_desc;
 476         struct crypto_ahash *ahash;
 477
 478         if (!x->aalg)
 479                 goto error;
 480
 481         if (x->encap)
 482                 goto error;
 483
 484         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 485         if (!ahp)
 486                 return -ENOMEM;
 487
 488         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 489         if (IS_ERR(ahash))
 490                 goto error;
 491
 492         ahp->ahash = ahash;
 493         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 494                                 (x->aalg->alg_key_len + 7) / 8))
 495                 goto error;
 496
 497         /*
 498          * Lookup the algorithm description maintained by xfrm_algo,
 499          * verify crypto transform properties, and store information
 500          * we need for AH processing.  This lookup cannot fail here
 501          * after a successful crypto_alloc_ahash().
 502          */
 503         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 504         BUG_ON(!aalg_desc);
 505
 506         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 507             crypto_ahash_digestsize(ahash)) {
 508                 pr_info("%s: %s digestsize %u != %hu\n",
 509                         __func__, x->aalg->alg_name,
 510                         crypto_ahash_digestsize(ahash),
 511                         aalg_desc->uinfo.auth.icv_fullbits / 8);
 512                 goto error;
 513         }
 514
 515         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 516         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 517
 518         if (x->props.flags & XFRM_STATE_ALIGN4)
 519                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 520                                                   ahp->icv_trunc_len);
 521         else
 522                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 523                                                   ahp->icv_trunc_len);
 524         if (x->props.mode == XFRM_MODE_TUNNEL)
 525                 x->props.header_len += sizeof(struct iphdr);
 526         x->data = ahp;
 527
 528         return 0;
 529
 530 error:
 531         if (ahp) {
 532                 crypto_free_ahash(ahp->ahash);
 533                 kfree(ahp);
 534         }
 535         return -EINVAL;
 536 }
 537
 538 static void ah_destroy(struct xfrm_state *x)
 539 {
 540         struct ah_data *ahp = x->data;
 541
 542         if (!ahp)
 543                 return;
 544
 545         crypto_free_ahash(ahp->ahash);
 546         kfree(ahp);
 547 }
 548
 549 static int ah4_rcv_cb(struct sk_buff *skb, int err)
 550 {
 551         return 0;
 552 }
 553
 554 static const struct xfrm_type ah_type =
 555 {
 556         .description    = "AH4",
 557         .owner          = THIS_MODULE,
 558         .proto          = IPPROTO_AH,
 559         .flags          = XFRM_TYPE_REPLAY_PROT,
 560         .init_state     = ah_init_state,
 561         .destructor     = ah_destroy,
 562         .input          = ah_input,
 563         .output         = ah_output
 564 };
 565
 566 static struct xfrm4_protocol ah4_protocol = {
 567         .handler        =       xfrm4_rcv,
 568         .input_handler  =       xfrm_input,
 569         .cb_handler     =       ah4_rcv_cb,
 570         .err_handler    =       ah4_err,
 571         .priority       =       0,
 572 };
 573
 574 static int __init ah4_init(void)
 575 {
 576         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 577                 pr_info("%s: can't add xfrm type\n", __func__);
 578                 return -EAGAIN;
 579         }
 580         if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
 581                 pr_info("%s: can't add protocol\n", __func__);
 582                 xfrm_unregister_type(&ah_type, AF_INET);
 583                 return -EAGAIN;
 584         }
 585         return 0;
 586 }
 587
 588 static void __exit ah4_fini(void)
 589 {
 590         if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
 591                 pr_info("%s: can't remove protocol\n", __func__);
 592         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 593                 pr_info("%s: can't remove xfrm type\n", __func__);
 594 }
 595
 596 module_init(ah4_init);
 597 module_exit(ah4_fini);
 598 MODULE_LICENSE("GPL");
 599 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);