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         work_iph = AH_SKB_CB(skb)->tmp;
 274         auth_data = ah_tmp_auth(work_iph, ihl);
 275         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 276
 277         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 278         if (err)
 279                 goto out;
 280
 281         err = ah->nexthdr;
 282
 283         skb->network_header += ah_hlen;
 284         memcpy(skb_network_header(skb), work_iph, ihl);
 285         __skb_pull(skb, ah_hlen + ihl);
 286
 287         if (x->props.mode == XFRM_MODE_TUNNEL)
 288                 skb_reset_transport_header(skb);
 289         else
 290                 skb_set_transport_header(skb, -ihl);
 291 out:
 292         kfree(AH_SKB_CB(skb)->tmp);
 293         xfrm_input_resume(skb, err);
 294 }
 295
 296 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 297 {
 298         int ah_hlen;
 299         int ihl;
 300         int nexthdr;
 301         int nfrags;
 302         u8 *auth_data;
 303         u8 *icv;
 304         struct sk_buff *trailer;
 305         struct crypto_ahash *ahash;
 306         struct ahash_request *req;
 307         struct scatterlist *sg;
 308         struct iphdr *iph, *work_iph;
 309         struct ip_auth_hdr *ah;
 310         struct ah_data *ahp;
 311         int err = -ENOMEM;
 312         int seqhi_len = 0;
 313         __be32 *seqhi;
 314         int sglists = 0;
 315         struct scatterlist *seqhisg;
 316
 317         if (!pskb_may_pull(skb, sizeof(*ah)))
 318                 goto out;
 319
 320         ah = (struct ip_auth_hdr *)skb->data;
 321         ahp = x->data;
 322         ahash = ahp->ahash;
 323
 324         nexthdr = ah->nexthdr;
 325         ah_hlen = (ah->hdrlen + 2) << 2;
 326
 327         if (x->props.flags & XFRM_STATE_ALIGN4) {
 328                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 329                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 330                         goto out;
 331         } else {
 332                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 333                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 334                         goto out;
 335         }
 336
 337         if (!pskb_may_pull(skb, ah_hlen))
 338                 goto out;
 339
 340         /* We are going to _remove_ AH header to keep sockets happy,
 341          * so... Later this can change. */
 342         if (skb_unclone(skb, GFP_ATOMIC))
 343                 goto out;
 344
 345         skb->ip_summed = CHECKSUM_NONE;
 346
 347
 348         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 349                 goto out;
 350         nfrags = err;
 351
 352         ah = (struct ip_auth_hdr *)skb->data;
 353         iph = ip_hdr(skb);
 354         ihl = ip_hdrlen(skb);
 355
 356         if (x->props.flags & XFRM_STATE_ESN) {
 357                 sglists = 1;
 358                 seqhi_len = sizeof(*seqhi);
 359         }
 360
 361         work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
 362                                 ahp->icv_trunc_len + seqhi_len);
 363         if (!work_iph)
 364                 goto out;
 365
 366         seqhi = (__be32 *)((char *)work_iph + ihl);
 367         auth_data = ah_tmp_auth(seqhi, seqhi_len);
 368         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 369         req = ah_tmp_req(ahash, icv);
 370         sg = ah_req_sg(ahash, req);
 371         seqhisg = sg + nfrags;
 372
 373         memcpy(work_iph, iph, ihl);
 374         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 375         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 376
 377         iph->ttl = 0;
 378         iph->tos = 0;
 379         iph->frag_off = 0;
 380         iph->check = 0;
 381         if (ihl > sizeof(*iph)) {
 382                 __be32 dummy;
 383                 err = ip_clear_mutable_options(iph, &dummy);
 384                 if (err)
 385                         goto out_free;
 386         }
 387
 388         skb_push(skb, ihl);
 389
 390         sg_init_table(sg, nfrags + sglists);
 391         skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 392
 393         if (x->props.flags & XFRM_STATE_ESN) {
 394                 /* Attach seqhi sg right after packet payload */
 395                 *seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
 396                 sg_set_buf(seqhisg, seqhi, seqhi_len);
 397         }
 398         ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 399         ahash_request_set_callback(req, 0, ah_input_done, skb);
 400
 401         AH_SKB_CB(skb)->tmp = work_iph;
 402
 403         err = crypto_ahash_digest(req);
 404         if (err) {
 405                 if (err == -EINPROGRESS)
 406                         goto out;
 407
 408                 goto out_free;
 409         }
 410
 411         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 412         if (err)
 413                 goto out_free;
 414
 415         skb->network_header += ah_hlen;
 416         memcpy(skb_network_header(skb), work_iph, ihl);
 417         __skb_pull(skb, ah_hlen + ihl);
 418         if (x->props.mode == XFRM_MODE_TUNNEL)
 419                 skb_reset_transport_header(skb);
 420         else
 421                 skb_set_transport_header(skb, -ihl);
 422
 423         err = nexthdr;
 424
 425 out_free:
 426         kfree (work_iph);
 427 out:
 428         return err;
 429 }
 430
 431 static int ah4_err(struct sk_buff *skb, u32 info)
 432 {
 433         struct net *net = dev_net(skb->dev);
 434         const struct iphdr *iph = (const struct iphdr *)skb->data;
 435         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 436         struct xfrm_state *x;
 437
 438         switch (icmp_hdr(skb)->type) {
 439         case ICMP_DEST_UNREACH:
 440                 if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 441                         return 0;
 442         case ICMP_REDIRECT:
 443                 break;
 444         default:
 445                 return 0;
 446         }
 447
 448         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 449                               ah->spi, IPPROTO_AH, AF_INET);
 450         if (!x)
 451                 return 0;
 452
 453         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
 454                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_AH, 0);
 455         else
 456                 ipv4_redirect(skb, net, 0, 0, IPPROTO_AH, 0);
 457         xfrm_state_put(x);
 458
 459         return 0;
 460 }
 461
 462 static int ah_init_state(struct xfrm_state *x)
 463 {
 464         struct ah_data *ahp = NULL;
 465         struct xfrm_algo_desc *aalg_desc;
 466         struct crypto_ahash *ahash;
 467
 468         if (!x->aalg)
 469                 goto error;
 470
 471         if (x->encap)
 472                 goto error;
 473
 474         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 475         if (!ahp)
 476                 return -ENOMEM;
 477
 478         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 479         if (IS_ERR(ahash))
 480                 goto error;
 481
 482         ahp->ahash = ahash;
 483         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 484                                 (x->aalg->alg_key_len + 7) / 8))
 485                 goto error;
 486
 487         /*
 488          * Lookup the algorithm description maintained by xfrm_algo,
 489          * verify crypto transform properties, and store information
 490          * we need for AH processing.  This lookup cannot fail here
 491          * after a successful crypto_alloc_ahash().
 492          */
 493         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 494         BUG_ON(!aalg_desc);
 495
 496         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 497             crypto_ahash_digestsize(ahash)) {
 498                 pr_info("%s: %s digestsize %u != %hu\n",
 499                         __func__, x->aalg->alg_name,
 500                         crypto_ahash_digestsize(ahash),
 501                         aalg_desc->uinfo.auth.icv_fullbits / 8);
 502                 goto error;
 503         }
 504
 505         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 506         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 507
 508         if (x->props.flags & XFRM_STATE_ALIGN4)
 509                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 510                                                   ahp->icv_trunc_len);
 511         else
 512                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 513                                                   ahp->icv_trunc_len);
 514         if (x->props.mode == XFRM_MODE_TUNNEL)
 515                 x->props.header_len += sizeof(struct iphdr);
 516         x->data = ahp;
 517
 518         return 0;
 519
 520 error:
 521         if (ahp) {
 522                 crypto_free_ahash(ahp->ahash);
 523                 kfree(ahp);
 524         }
 525         return -EINVAL;
 526 }
 527
 528 static void ah_destroy(struct xfrm_state *x)
 529 {
 530         struct ah_data *ahp = x->data;
 531
 532         if (!ahp)
 533                 return;
 534
 535         crypto_free_ahash(ahp->ahash);
 536         kfree(ahp);
 537 }
 538
 539 static int ah4_rcv_cb(struct sk_buff *skb, int err)
 540 {
 541         return 0;
 542 }
 543
 544 static const struct xfrm_type ah_type =
 545 {
 546         .description    = "AH4",
 547         .owner          = THIS_MODULE,
 548         .proto          = IPPROTO_AH,
 549         .flags          = XFRM_TYPE_REPLAY_PROT,
 550         .init_state     = ah_init_state,
 551         .destructor     = ah_destroy,
 552         .input          = ah_input,
 553         .output         = ah_output
 554 };
 555
 556 static struct xfrm4_protocol ah4_protocol = {
 557         .handler        =       xfrm4_rcv,
 558         .input_handler  =       xfrm_input,
 559         .cb_handler     =       ah4_rcv_cb,
 560         .err_handler    =       ah4_err,
 561         .priority       =       0,
 562 };
 563
 564 static int __init ah4_init(void)
 565 {
 566         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 567                 pr_info("%s: can't add xfrm type\n", __func__);
 568                 return -EAGAIN;
 569         }
 570         if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
 571                 pr_info("%s: can't add protocol\n", __func__);
 572                 xfrm_unregister_type(&ah_type, AF_INET);
 573                 return -EAGAIN;
 574         }
 575         return 0;
 576 }
 577
 578 static void __exit ah4_fini(void)
 579 {
 580         if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
 581                 pr_info("%s: can't remove protocol\n", __func__);
 582         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 583                 pr_info("%s: can't remove xfrm type\n", __func__);
 584 }
 585
 586 module_init(ah4_init);
 587 module_exit(ah4_fini);
 588 MODULE_LICENSE("GPL");
 589 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);