net/ipv4/ah4.c

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