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
 159         ahp = x->data;
 160         ahash = ahp->ahash;
 161
 162         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 163                 goto out;
 164         nfrags = err;
 165
 166         skb_push(skb, -skb_network_offset(skb));
 167         ah = ip_auth_hdr(skb);
 168         ihl = ip_hdrlen(skb);
 169
 170         err = -ENOMEM;
 171         iph = ah_alloc_tmp(ahash, nfrags, ihl);
 172         if (!iph)
 173                 goto out;
 174
 175         icv = ah_tmp_icv(ahash, iph, ihl);
 176         req = ah_tmp_req(ahash, icv);
 177         sg = ah_req_sg(ahash, req);
 178
 179         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 180
 181         top_iph = ip_hdr(skb);
 182
 183         iph->tos = top_iph->tos;
 184         iph->ttl = top_iph->ttl;
 185         iph->frag_off = top_iph->frag_off;
 186
 187         if (top_iph->ihl != 5) {
 188                 iph->daddr = top_iph->daddr;
 189                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 190                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 191                 if (err)
 192                         goto out_free;
 193         }
 194
 195         ah->nexthdr = *skb_mac_header(skb);
 196         *skb_mac_header(skb) = IPPROTO_AH;
 197
 198         top_iph->tos = 0;
 199         top_iph->tot_len = htons(skb->len);
 200         top_iph->frag_off = 0;
 201         top_iph->ttl = 0;
 202         top_iph->check = 0;
 203
 204         if (x->props.flags & XFRM_STATE_ALIGN4)
 205                 ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 206         else
 207                 ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 208
 209         ah->reserved = 0;
 210         ah->spi = x->id.spi;
 211         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 212
 213         sg_init_table(sg, nfrags);
 214         skb_to_sgvec(skb, sg, 0, skb->len);
 215
 216         ahash_request_set_crypt(req, sg, icv, skb->len);
 217         ahash_request_set_callback(req, 0, ah_output_done, skb);
 218
 219         AH_SKB_CB(skb)->tmp = iph;
 220
 221         err = crypto_ahash_digest(req);
 222         if (err) {
 223                 if (err == -EINPROGRESS)
 224                         goto out;
 225
 226                 if (err == -EBUSY)
 227                         err = NET_XMIT_DROP;
 228                 goto out_free;
 229         }
 230
 231         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 232
 233         top_iph->tos = iph->tos;
 234         top_iph->ttl = iph->ttl;
 235         top_iph->frag_off = iph->frag_off;
 236         if (top_iph->ihl != 5) {
 237                 top_iph->daddr = iph->daddr;
 238                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 239         }
 240
 241 out_free:
 242         kfree(iph);
 243 out:
 244         return err;
 245 }
 246
 247 static void ah_input_done(struct crypto_async_request *base, int err)
 248 {
 249         u8 *auth_data;
 250         u8 *icv;
 251         struct iphdr *work_iph;
 252         struct sk_buff *skb = base->data;
 253         struct xfrm_state *x = xfrm_input_state(skb);
 254         struct ah_data *ahp = x->data;
 255         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 256         int ihl = ip_hdrlen(skb);
 257         int ah_hlen = (ah->hdrlen + 2) << 2;
 258
 259         work_iph = AH_SKB_CB(skb)->tmp;
 260         auth_data = ah_tmp_auth(work_iph, ihl);
 261         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 262
 263         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 264         if (err)
 265                 goto out;
 266
 267         err = ah->nexthdr;
 268
 269         skb->network_header += ah_hlen;
 270         memcpy(skb_network_header(skb), work_iph, ihl);
 271         __skb_pull(skb, ah_hlen + ihl);
 272         skb_set_transport_header(skb, -ihl);
 273 out:
 274         kfree(AH_SKB_CB(skb)->tmp);
 275         xfrm_input_resume(skb, err);
 276 }
 277
 278 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 279 {
 280         int ah_hlen;
 281         int ihl;
 282         int nexthdr;
 283         int nfrags;
 284         u8 *auth_data;
 285         u8 *icv;
 286         struct sk_buff *trailer;
 287         struct crypto_ahash *ahash;
 288         struct ahash_request *req;
 289         struct scatterlist *sg;
 290         struct iphdr *iph, *work_iph;
 291         struct ip_auth_hdr *ah;
 292         struct ah_data *ahp;
 293         int err = -ENOMEM;
 294
 295         if (!pskb_may_pull(skb, sizeof(*ah)))
 296                 goto out;
 297
 298         ah = (struct ip_auth_hdr *)skb->data;
 299         ahp = x->data;
 300         ahash = ahp->ahash;
 301
 302         nexthdr = ah->nexthdr;
 303         ah_hlen = (ah->hdrlen + 2) << 2;
 304
 305         if (x->props.flags & XFRM_STATE_ALIGN4) {
 306                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 307                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 308                         goto out;
 309         } else {
 310                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 311                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 312                         goto out;
 313         }
 314
 315         if (!pskb_may_pull(skb, ah_hlen))
 316                 goto out;
 317
 318         /* We are going to _remove_ AH header to keep sockets happy,
 319          * so... Later this can change. */
 320         if (skb_cloned(skb) &&
 321             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 322                 goto out;
 323
 324         skb->ip_summed = CHECKSUM_NONE;
 325
 326
 327         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 328                 goto out;
 329         nfrags = err;
 330
 331         ah = (struct ip_auth_hdr *)skb->data;
 332         iph = ip_hdr(skb);
 333         ihl = ip_hdrlen(skb);
 334
 335         work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
 336         if (!work_iph)
 337                 goto out;
 338
 339         auth_data = ah_tmp_auth(work_iph, ihl);
 340         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 341         req = ah_tmp_req(ahash, icv);
 342         sg = ah_req_sg(ahash, req);
 343
 344         memcpy(work_iph, iph, ihl);
 345         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 346         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 347
 348         iph->ttl = 0;
 349         iph->tos = 0;
 350         iph->frag_off = 0;
 351         iph->check = 0;
 352         if (ihl > sizeof(*iph)) {
 353                 __be32 dummy;
 354                 err = ip_clear_mutable_options(iph, &dummy);
 355                 if (err)
 356                         goto out_free;
 357         }
 358
 359         skb_push(skb, ihl);
 360
 361         sg_init_table(sg, nfrags);
 362         skb_to_sgvec(skb, sg, 0, skb->len);
 363
 364         ahash_request_set_crypt(req, sg, icv, skb->len);
 365         ahash_request_set_callback(req, 0, ah_input_done, skb);
 366
 367         AH_SKB_CB(skb)->tmp = work_iph;
 368
 369         err = crypto_ahash_digest(req);
 370         if (err) {
 371                 if (err == -EINPROGRESS)
 372                         goto out;
 373
 374                 goto out_free;
 375         }
 376
 377         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 378         if (err)
 379                 goto out_free;
 380
 381         skb->network_header += ah_hlen;
 382         memcpy(skb_network_header(skb), work_iph, ihl);
 383         __skb_pull(skb, ah_hlen + ihl);
 384         skb_set_transport_header(skb, -ihl);
 385
 386         err = nexthdr;
 387
 388 out_free:
 389         kfree (work_iph);
 390 out:
 391         return err;
 392 }
 393
 394 static void ah4_err(struct sk_buff *skb, u32 info)
 395 {
 396         struct net *net = dev_net(skb->dev);
 397         const struct iphdr *iph = (const struct iphdr *)skb->data;
 398         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 399         struct xfrm_state *x;
 400
 401         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 402             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 403                 return;
 404
 405         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 406                               ah->spi, IPPROTO_AH, AF_INET);
 407         if (!x)
 408                 return;
 409         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 410                ntohl(ah->spi), ntohl(iph->daddr));
 411         xfrm_state_put(x);
 412 }
 413
 414 static int ah_init_state(struct xfrm_state *x)
 415 {
 416         struct ah_data *ahp = NULL;
 417         struct xfrm_algo_desc *aalg_desc;
 418         struct crypto_ahash *ahash;
 419
 420         if (!x->aalg)
 421                 goto error;
 422
 423         if (x->encap)
 424                 goto error;
 425
 426         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 427         if (!ahp)
 428                 return -ENOMEM;
 429
 430         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 431         if (IS_ERR(ahash))
 432                 goto error;
 433
 434         ahp->ahash = ahash;
 435         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 436                                 (x->aalg->alg_key_len + 7) / 8))
 437                 goto error;
 438
 439         /*
 440          * Lookup the algorithm description maintained by xfrm_algo,
 441          * verify crypto transform properties, and store information
 442          * we need for AH processing.  This lookup cannot fail here
 443          * after a successful crypto_alloc_ahash().
 444          */
 445         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 446         BUG_ON(!aalg_desc);
 447
 448         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 449             crypto_ahash_digestsize(ahash)) {
 450                 pr_info("%s: %s digestsize %u != %hu\n",
 451                         __func__, x->aalg->alg_name,
 452                         crypto_ahash_digestsize(ahash),
 453                         aalg_desc->uinfo.auth.icv_fullbits / 8);
 454                 goto error;
 455         }
 456
 457         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 458         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 459
 460         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 461
 462         if (x->props.flags & XFRM_STATE_ALIGN4)
 463                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 464                                                   ahp->icv_trunc_len);
 465         else
 466                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 467                                                   ahp->icv_trunc_len);
 468         if (x->props.mode == XFRM_MODE_TUNNEL)
 469                 x->props.header_len += sizeof(struct iphdr);
 470         x->data = ahp;
 471
 472         return 0;
 473
 474 error:
 475         if (ahp) {
 476                 crypto_free_ahash(ahp->ahash);
 477                 kfree(ahp);
 478         }
 479         return -EINVAL;
 480 }
 481
 482 static void ah_destroy(struct xfrm_state *x)
 483 {
 484         struct ah_data *ahp = x->data;
 485
 486         if (!ahp)
 487                 return;
 488
 489         crypto_free_ahash(ahp->ahash);
 490         kfree(ahp);
 491 }
 492
 493
 494 static const struct xfrm_type ah_type =
 495 {
 496         .description    = "AH4",
 497         .owner          = THIS_MODULE,
 498         .proto          = IPPROTO_AH,
 499         .flags          = XFRM_TYPE_REPLAY_PROT,
 500         .init_state     = ah_init_state,
 501         .destructor     = ah_destroy,
 502         .input          = ah_input,
 503         .output         = ah_output
 504 };
 505
 506 static const struct net_protocol ah4_protocol = {
 507         .handler        =       xfrm4_rcv,
 508         .err_handler    =       ah4_err,
 509         .no_policy      =       1,
 510         .netns_ok       =       1,
 511 };
 512
 513 static int __init ah4_init(void)
 514 {
 515         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 516                 pr_info("%s: can't add xfrm type\n", __func__);
 517                 return -EAGAIN;
 518         }
 519         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 520                 pr_info("%s: can't add protocol\n", __func__);
 521                 xfrm_unregister_type(&ah_type, AF_INET);
 522                 return -EAGAIN;
 523         }
 524         return 0;
 525 }
 526
 527 static void __exit ah4_fini(void)
 528 {
 529         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 530                 pr_info("%s: can't remove protocol\n", __func__);
 531         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 532                 pr_info("%s: can't remove xfrm type\n", __func__);
 533 }
 534
 535 module_init(ah4_init);
 536 module_exit(ah4_fini);
 537 MODULE_LICENSE("GPL");
 538 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);