net/ipv4/ah4.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #define pr_fmt(fmt) "IPsec: " fmt
   3
   4 #include <crypto/algapi.h>
   5 #include <crypto/hash.h>
   6 #include <linux/err.h>
   7 #include <linux/module.h>
   8 #include <linux/slab.h>
   9 #include <net/ip.h>
  10 #include <net/xfrm.h>
  11 #include <net/ah.h>
  12 #include <linux/crypto.h>
  13 #include <linux/pfkeyv2.h>
  14 #include <linux/scatterlist.h>
  15 #include <net/icmp.h>
  16 #include <net/protocol.h>
  17
  18 struct ah_skb_cb {
  19         struct xfrm_skb_cb xfrm;
  20         void *tmp;
  21 };
  22
  23 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
  24
  25 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
  26                           unsigned int size)
  27 {
  28         unsigned int len;
  29
  30         len = size + crypto_ahash_digestsize(ahash) +
  31               (crypto_ahash_alignmask(ahash) &
  32                ~(crypto_tfm_ctx_alignment() - 1));
  33
  34         len = ALIGN(len, crypto_tfm_ctx_alignment());
  35
  36         len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
  37         len = ALIGN(len, __alignof__(struct scatterlist));
  38
  39         len += sizeof(struct scatterlist) * nfrags;
  40
  41         return kmalloc(len, GFP_ATOMIC);
  42 }
  43
  44 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
  45 {
  46         return tmp + offset;
  47 }
  48
  49 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
  50                              unsigned int offset)
  51 {
  52         return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
  53 }
  54
  55 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
  56                                                u8 *icv)
  57 {
  58         struct ahash_request *req;
  59
  60         req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
  61                                 crypto_tfm_ctx_alignment());
  62
  63         ahash_request_set_tfm(req, ahash);
  64
  65         return req;
  66 }
  67
  68 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  69                                              struct ahash_request *req)
  70 {
  71         return (void *)ALIGN((unsigned long)(req + 1) +
  72                              crypto_ahash_reqsize(ahash),
  73                              __alignof__(struct scatterlist));
  74 }
  75
  76 /* Clear mutable options and find final destination to substitute
  77  * into IP header for icv calculation. Options are already checked
  78  * for validity, so paranoia is not required. */
  79
  80 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
  81 {
  82         unsigned char *optptr = (unsigned char *)(iph+1);
  83         int  l = iph->ihl*4 - sizeof(struct iphdr);
  84         int  optlen;
  85
  86         while (l > 0) {
  87                 switch (*optptr) {
  88                 case IPOPT_END:
  89                         return 0;
  90                 case IPOPT_NOOP:
  91                         l--;
  92                         optptr++;
  93                         continue;
  94                 }
  95                 optlen = optptr[1];
  96                 if (optlen<2 || optlen>l)
  97                         return -EINVAL;
  98                 switch (*optptr) {
  99                 case IPOPT_SEC:
 100                 case 0x85:      /* Some "Extended Security" crap. */
 101                 case IPOPT_CIPSO:
 102                 case IPOPT_RA:
 103                 case 0x80|21:   /* RFC1770 */
 104                         break;
 105                 case IPOPT_LSRR:
 106                 case IPOPT_SSRR:
 107                         if (optlen < 6)
 108                                 return -EINVAL;
 109                         memcpy(daddr, optptr+optlen-4, 4);
 110                         fallthrough;
 111                 default:
 112                         memset(optptr, 0, optlen);
 113                 }
 114                 l -= optlen;
 115                 optptr += optlen;
 116         }
 117         return 0;
 118 }
 119
 120 static void ah_output_done(struct crypto_async_request *base, int err)
 121 {
 122         u8 *icv;
 123         struct iphdr *iph;
 124         struct sk_buff *skb = base->data;
 125         struct xfrm_state *x = skb_dst(skb)->xfrm;
 126         struct ah_data *ahp = x->data;
 127         struct iphdr *top_iph = ip_hdr(skb);
 128         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 129         int ihl = ip_hdrlen(skb);
 130
 131         iph = AH_SKB_CB(skb)->tmp;
 132         icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 133         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 134
 135         top_iph->tos = iph->tos;
 136         top_iph->ttl = iph->ttl;
 137         top_iph->frag_off = iph->frag_off;
 138         if (top_iph->ihl != 5) {
 139                 top_iph->daddr = iph->daddr;
 140                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 141         }
 142
 143         kfree(AH_SKB_CB(skb)->tmp);
 144         xfrm_output_resume(skb->sk, skb, err);
 145 }
 146
 147 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 148 {
 149         int err;
 150         int nfrags;
 151         int ihl;
 152         u8 *icv;
 153         struct sk_buff *trailer;
 154         struct crypto_ahash *ahash;
 155         struct ahash_request *req;
 156         struct scatterlist *sg;
 157         struct iphdr *iph, *top_iph;
 158         struct ip_auth_hdr *ah;
 159         struct ah_data *ahp;
 160         int seqhi_len = 0;
 161         __be32 *seqhi;
 162         int sglists = 0;
 163         struct scatterlist *seqhisg;
 164
 165         ahp = x->data;
 166         ahash = ahp->ahash;
 167
 168         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 169                 goto out;
 170         nfrags = err;
 171
 172         skb_push(skb, -skb_network_offset(skb));
 173         ah = ip_auth_hdr(skb);
 174         ihl = ip_hdrlen(skb);
 175
 176         if (x->props.flags & XFRM_STATE_ESN) {
 177                 sglists = 1;
 178                 seqhi_len = sizeof(*seqhi);
 179         }
 180         err = -ENOMEM;
 181         iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
 182         if (!iph)
 183                 goto out;
 184         seqhi = (__be32 *)((char *)iph + ihl);
 185         icv = ah_tmp_icv(ahash, seqhi, seqhi_len);
 186         req = ah_tmp_req(ahash, icv);
 187         sg = ah_req_sg(ahash, req);
 188         seqhisg = sg + nfrags;
 189
 190         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 191
 192         top_iph = ip_hdr(skb);
 193
 194         iph->tos = top_iph->tos;
 195         iph->ttl = top_iph->ttl;
 196         iph->frag_off = top_iph->frag_off;
 197
 198         if (top_iph->ihl != 5) {
 199                 iph->daddr = top_iph->daddr;
 200                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 201                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 202                 if (err)
 203                         goto out_free;
 204         }
 205
 206         ah->nexthdr = *skb_mac_header(skb);
 207         *skb_mac_header(skb) = IPPROTO_AH;
 208
 209         top_iph->tos = 0;
 210         top_iph->tot_len = htons(skb->len);
 211         top_iph->frag_off = 0;
 212         top_iph->ttl = 0;
 213         top_iph->check = 0;
 214
 215         if (x->props.flags & XFRM_STATE_ALIGN4)
 216                 ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 217         else
 218                 ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 219
 220         ah->reserved = 0;
 221         ah->spi = x->id.spi;
 222         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 223
 224         sg_init_table(sg, nfrags + sglists);
 225         err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 226         if (unlikely(err < 0))
 227                 goto out_free;
 228
 229         if (x->props.flags & XFRM_STATE_ESN) {
 230                 /* Attach seqhi sg right after packet payload */
 231                 *seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
 232                 sg_set_buf(seqhisg, seqhi, seqhi_len);
 233         }
 234         ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 235         ahash_request_set_callback(req, 0, ah_output_done, skb);
 236
 237         AH_SKB_CB(skb)->tmp = iph;
 238
 239         err = crypto_ahash_digest(req);
 240         if (err) {
 241                 if (err == -EINPROGRESS)
 242                         goto out;
 243
 244                 if (err == -ENOSPC)
 245                         err = NET_XMIT_DROP;
 246                 goto out_free;
 247         }
 248
 249         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 250
 251         top_iph->tos = iph->tos;
 252         top_iph->ttl = iph->ttl;
 253         top_iph->frag_off = iph->frag_off;
 254         if (top_iph->ihl != 5) {
 255                 top_iph->daddr = iph->daddr;
 256                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 257         }
 258
 259 out_free:
 260         kfree(iph);
 261 out:
 262         return err;
 263 }
 264
 265 static void ah_input_done(struct crypto_async_request *base, int err)
 266 {
 267         u8 *auth_data;
 268         u8 *icv;
 269         struct iphdr *work_iph;
 270         struct sk_buff *skb = base->data;
 271         struct xfrm_state *x = xfrm_input_state(skb);
 272         struct ah_data *ahp = x->data;
 273         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 274         int ihl = ip_hdrlen(skb);
 275         int ah_hlen = (ah->hdrlen + 2) << 2;
 276
 277         if (err)
 278                 goto out;
 279
 280         work_iph = AH_SKB_CB(skb)->tmp;
 281         auth_data = ah_tmp_auth(work_iph, ihl);
 282         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 283
 284         err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
 285         if (err)
 286                 goto out;
 287
 288         err = ah->nexthdr;
 289
 290         skb->network_header += ah_hlen;
 291         memcpy(skb_network_header(skb), work_iph, ihl);
 292         __skb_pull(skb, ah_hlen + ihl);
 293
 294         if (x->props.mode == XFRM_MODE_TUNNEL)
 295                 skb_reset_transport_header(skb);
 296         else
 297                 skb_set_transport_header(skb, -ihl);
 298 out:
 299         kfree(AH_SKB_CB(skb)->tmp);
 300         xfrm_input_resume(skb, err);
 301 }
 302
 303 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 304 {
 305         int ah_hlen;
 306         int ihl;
 307         int nexthdr;
 308         int nfrags;
 309         u8 *auth_data;
 310         u8 *icv;
 311         struct sk_buff *trailer;
 312         struct crypto_ahash *ahash;
 313         struct ahash_request *req;
 314         struct scatterlist *sg;
 315         struct iphdr *iph, *work_iph;
 316         struct ip_auth_hdr *ah;
 317         struct ah_data *ahp;
 318         int err = -ENOMEM;
 319         int seqhi_len = 0;
 320         __be32 *seqhi;
 321         int sglists = 0;
 322         struct scatterlist *seqhisg;
 323
 324         if (!pskb_may_pull(skb, sizeof(*ah)))
 325                 goto out;
 326
 327         ah = (struct ip_auth_hdr *)skb->data;
 328         ahp = x->data;
 329         ahash = ahp->ahash;
 330
 331         nexthdr = ah->nexthdr;
 332         ah_hlen = (ah->hdrlen + 2) << 2;
 333
 334         if (x->props.flags & XFRM_STATE_ALIGN4) {
 335                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 336                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 337                         goto out;
 338         } else {
 339                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 340                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 341                         goto out;
 342         }
 343
 344         if (!pskb_may_pull(skb, ah_hlen))
 345                 goto out;
 346
 347         /* We are going to _remove_ AH header to keep sockets happy,
 348          * so... Later this can change. */
 349         if (skb_unclone(skb, GFP_ATOMIC))
 350                 goto out;
 351
 352         skb->ip_summed = CHECKSUM_NONE;
 353
 354
 355         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 356                 goto out;
 357         nfrags = err;
 358
 359         ah = (struct ip_auth_hdr *)skb->data;
 360         iph = ip_hdr(skb);
 361         ihl = ip_hdrlen(skb);
 362
 363         if (x->props.flags & XFRM_STATE_ESN) {
 364                 sglists = 1;
 365                 seqhi_len = sizeof(*seqhi);
 366         }
 367
 368         work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
 369                                 ahp->icv_trunc_len + seqhi_len);
 370         if (!work_iph) {
 371                 err = -ENOMEM;
 372                 goto out;
 373         }
 374
 375         seqhi = (__be32 *)((char *)work_iph + ihl);
 376         auth_data = ah_tmp_auth(seqhi, seqhi_len);
 377         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 378         req = ah_tmp_req(ahash, icv);
 379         sg = ah_req_sg(ahash, req);
 380         seqhisg = sg + nfrags;
 381
 382         memcpy(work_iph, iph, ihl);
 383         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 384         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 385
 386         iph->ttl = 0;
 387         iph->tos = 0;
 388         iph->frag_off = 0;
 389         iph->check = 0;
 390         if (ihl > sizeof(*iph)) {
 391                 __be32 dummy;
 392                 err = ip_clear_mutable_options(iph, &dummy);
 393                 if (err)
 394                         goto out_free;
 395         }
 396
 397         skb_push(skb, ihl);
 398
 399         sg_init_table(sg, nfrags + sglists);
 400         err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 401         if (unlikely(err < 0))
 402                 goto out_free;
 403
 404         if (x->props.flags & XFRM_STATE_ESN) {
 405                 /* Attach seqhi sg right after packet payload */
 406                 *seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
 407                 sg_set_buf(seqhisg, seqhi, seqhi_len);
 408         }
 409         ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 410         ahash_request_set_callback(req, 0, ah_input_done, skb);
 411
 412         AH_SKB_CB(skb)->tmp = work_iph;
 413
 414         err = crypto_ahash_digest(req);
 415         if (err) {
 416                 if (err == -EINPROGRESS)
 417                         goto out;
 418
 419                 goto out_free;
 420         }
 421
 422         err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
 423         if (err)
 424                 goto out_free;
 425
 426         skb->network_header += ah_hlen;
 427         memcpy(skb_network_header(skb), work_iph, ihl);
 428         __skb_pull(skb, ah_hlen + ihl);
 429         if (x->props.mode == XFRM_MODE_TUNNEL)
 430                 skb_reset_transport_header(skb);
 431         else
 432                 skb_set_transport_header(skb, -ihl);
 433
 434         err = nexthdr;
 435
 436 out_free:
 437         kfree (work_iph);
 438 out:
 439         return err;
 440 }
 441
 442 static int ah4_err(struct sk_buff *skb, u32 info)
 443 {
 444         struct net *net = dev_net(skb->dev);
 445         const struct iphdr *iph = (const struct iphdr *)skb->data;
 446         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 447         struct xfrm_state *x;
 448
 449         switch (icmp_hdr(skb)->type) {
 450         case ICMP_DEST_UNREACH:
 451                 if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 452                         return 0;
 453                 break;
 454         case ICMP_REDIRECT:
 455                 break;
 456         default:
 457                 return 0;
 458         }
 459
 460         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 461                               ah->spi, IPPROTO_AH, AF_INET);
 462         if (!x)
 463                 return 0;
 464
 465         if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
 466                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_AH);
 467         else
 468                 ipv4_redirect(skb, net, 0, IPPROTO_AH);
 469         xfrm_state_put(x);
 470
 471         return 0;
 472 }
 473
 474 static int ah_init_state(struct xfrm_state *x)
 475 {
 476         struct ah_data *ahp = NULL;
 477         struct xfrm_algo_desc *aalg_desc;
 478         struct crypto_ahash *ahash;
 479
 480         if (!x->aalg)
 481                 goto error;
 482
 483         if (x->encap)
 484                 goto error;
 485
 486         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 487         if (!ahp)
 488                 return -ENOMEM;
 489
 490         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 491         if (IS_ERR(ahash))
 492                 goto error;
 493
 494         ahp->ahash = ahash;
 495         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 496                                 (x->aalg->alg_key_len + 7) / 8))
 497                 goto error;
 498
 499         /*
 500          * Lookup the algorithm description maintained by xfrm_algo,
 501          * verify crypto transform properties, and store information
 502          * we need for AH processing.  This lookup cannot fail here
 503          * after a successful crypto_alloc_ahash().
 504          */
 505         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 506         BUG_ON(!aalg_desc);
 507
 508         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 509             crypto_ahash_digestsize(ahash)) {
 510                 pr_info("%s: %s digestsize %u != %hu\n",
 511                         __func__, x->aalg->alg_name,
 512                         crypto_ahash_digestsize(ahash),
 513                         aalg_desc->uinfo.auth.icv_fullbits / 8);
 514                 goto error;
 515         }
 516
 517         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 518         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 519
 520         if (x->props.flags & XFRM_STATE_ALIGN4)
 521                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 522                                                   ahp->icv_trunc_len);
 523         else
 524                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 525                                                   ahp->icv_trunc_len);
 526         if (x->props.mode == XFRM_MODE_TUNNEL)
 527                 x->props.header_len += sizeof(struct iphdr);
 528         x->data = ahp;
 529
 530         return 0;
 531
 532 error:
 533         if (ahp) {
 534                 crypto_free_ahash(ahp->ahash);
 535                 kfree(ahp);
 536         }
 537         return -EINVAL;
 538 }
 539
 540 static void ah_destroy(struct xfrm_state *x)
 541 {
 542         struct ah_data *ahp = x->data;
 543
 544         if (!ahp)
 545                 return;
 546
 547         crypto_free_ahash(ahp->ahash);
 548         kfree(ahp);
 549 }
 550
 551 static int ah4_rcv_cb(struct sk_buff *skb, int err)
 552 {
 553         return 0;
 554 }
 555
 556 static const struct xfrm_type ah_type =
 557 {
 558         .owner          = THIS_MODULE,
 559         .proto          = IPPROTO_AH,
 560         .flags          = XFRM_TYPE_REPLAY_PROT,
 561         .init_state     = ah_init_state,
 562         .destructor     = ah_destroy,
 563         .input          = ah_input,
 564         .output         = ah_output
 565 };
 566
 567 static struct xfrm4_protocol ah4_protocol = {
 568         .handler        =       xfrm4_rcv,
 569         .input_handler  =       xfrm_input,
 570         .cb_handler     =       ah4_rcv_cb,
 571         .err_handler    =       ah4_err,
 572         .priority       =       0,
 573 };
 574
 575 static int __init ah4_init(void)
 576 {
 577         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 578                 pr_info("%s: can't add xfrm type\n", __func__);
 579                 return -EAGAIN;
 580         }
 581         if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
 582                 pr_info("%s: can't add protocol\n", __func__);
 583                 xfrm_unregister_type(&ah_type, AF_INET);
 584                 return -EAGAIN;
 585         }
 586         return 0;
 587 }
 588
 589 static void __exit ah4_fini(void)
 590 {
 591         if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
 592                 pr_info("%s: can't remove protocol\n", __func__);
 593         xfrm_unregister_type(&ah_type, AF_INET);
 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);