net/ipv4/esp4.c

   1 #include <crypto/aead.h>
   2 #include <crypto/authenc.h>
   3 #include <linux/err.h>
   4 #include <linux/module.h>
   5 #include <net/ip.h>
   6 #include <net/xfrm.h>
   7 #include <net/esp.h>
   8 #include <linux/scatterlist.h>
   9 #include <linux/kernel.h>
  10 #include <linux/pfkeyv2.h>
  11 #include <linux/rtnetlink.h>
  12 #include <linux/slab.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/in6.h>
  15 #include <net/icmp.h>
  16 #include <net/protocol.h>
  17 #include <net/udp.h>
  18
  19 struct esp_skb_cb {
  20         struct xfrm_skb_cb xfrm;
  21         void *tmp;
  22 };
  23
  24 #define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))
  25
  26 /*
  27  * Allocate an AEAD request structure with extra space for SG and IV.
  28  *
  29  * For alignment considerations the IV is placed at the front, followed
  30  * by the request and finally the SG list.
  31  *
  32  * TODO: Use spare space in skb for this where possible.
  33  */
  34 static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags)
  35 {
  36         unsigned int len;
  37
  38         len = crypto_aead_ivsize(aead);
  39         if (len) {
  40                 len += crypto_aead_alignmask(aead) &
  41                        ~(crypto_tfm_ctx_alignment() - 1);
  42                 len = ALIGN(len, crypto_tfm_ctx_alignment());
  43         }
  44
  45         len += sizeof(struct aead_givcrypt_request) + crypto_aead_reqsize(aead);
  46         len = ALIGN(len, __alignof__(struct scatterlist));
  47
  48         len += sizeof(struct scatterlist) * nfrags;
  49
  50         return kmalloc(len, GFP_ATOMIC);
  51 }
  52
  53 static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp)
  54 {
  55         return crypto_aead_ivsize(aead) ?
  56                PTR_ALIGN((u8 *)tmp, crypto_aead_alignmask(aead) + 1) : tmp;
  57 }
  58
  59 static inline struct aead_givcrypt_request *esp_tmp_givreq(
  60         struct crypto_aead *aead, u8 *iv)
  61 {
  62         struct aead_givcrypt_request *req;
  63
  64         req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
  65                                 crypto_tfm_ctx_alignment());
  66         aead_givcrypt_set_tfm(req, aead);
  67         return req;
  68 }
  69
  70 static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
  71 {
  72         struct aead_request *req;
  73
  74         req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
  75                                 crypto_tfm_ctx_alignment());
  76         aead_request_set_tfm(req, aead);
  77         return req;
  78 }
  79
  80 static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
  81                                              struct aead_request *req)
  82 {
  83         return (void *)ALIGN((unsigned long)(req + 1) +
  84                              crypto_aead_reqsize(aead),
  85                              __alignof__(struct scatterlist));
  86 }
  87
  88 static inline struct scatterlist *esp_givreq_sg(
  89         struct crypto_aead *aead, struct aead_givcrypt_request *req)
  90 {
  91         return (void *)ALIGN((unsigned long)(req + 1) +
  92                              crypto_aead_reqsize(aead),
  93                              __alignof__(struct scatterlist));
  94 }
  95
  96 static void esp_output_done(struct crypto_async_request *base, int err)
  97 {
  98         struct sk_buff *skb = base->data;
  99
 100         kfree(ESP_SKB_CB(skb)->tmp);
 101         xfrm_output_resume(skb, err);
 102 }
 103
 104 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 105 {
 106         int err;
 107         struct ip_esp_hdr *esph;
 108         struct crypto_aead *aead;
 109         struct aead_givcrypt_request *req;
 110         struct scatterlist *sg;
 111         struct scatterlist *asg;
 112         struct esp_data *esp;
 113         struct sk_buff *trailer;
 114         void *tmp;
 115         u8 *iv;
 116         u8 *tail;
 117         int blksize;
 118         int clen;
 119         int alen;
 120         int nfrags;
 121
 122         /* skb is pure payload to encrypt */
 123
 124         err = -ENOMEM;
 125
 126         /* Round to block size */
 127         clen = skb->len;
 128
 129         esp = x->data;
 130         aead = esp->aead;
 131         alen = crypto_aead_authsize(aead);
 132
 133         blksize = ALIGN(crypto_aead_blocksize(aead), 4);
 134         clen = ALIGN(clen + 2, blksize);
 135         if (esp->padlen)
 136                 clen = ALIGN(clen, esp->padlen);
 137
 138         if ((err = skb_cow_data(skb, clen - skb->len + alen, &trailer)) < 0)
 139                 goto error;
 140         nfrags = err;
 141
 142         tmp = esp_alloc_tmp(aead, nfrags + 1);
 143         if (!tmp)
 144                 goto error;
 145
 146         iv = esp_tmp_iv(aead, tmp);
 147         req = esp_tmp_givreq(aead, iv);
 148         asg = esp_givreq_sg(aead, req);
 149         sg = asg + 1;
 150
 151         /* Fill padding... */
 152         tail = skb_tail_pointer(trailer);
 153         do {
 154                 int i;
 155                 for (i=0; i<clen-skb->len - 2; i++)
 156                         tail[i] = i + 1;
 157         } while (0);
 158         tail[clen - skb->len - 2] = (clen - skb->len) - 2;
 159         tail[clen - skb->len - 1] = *skb_mac_header(skb);
 160         pskb_put(skb, trailer, clen - skb->len + alen);
 161
 162         skb_push(skb, -skb_network_offset(skb));
 163         esph = ip_esp_hdr(skb);
 164         *skb_mac_header(skb) = IPPROTO_ESP;
 165
 166         /* this is non-NULL only with UDP Encapsulation */
 167         if (x->encap) {
 168                 struct xfrm_encap_tmpl *encap = x->encap;
 169                 struct udphdr *uh;
 170                 __be32 *udpdata32;
 171                 __be16 sport, dport;
 172                 int encap_type;
 173
 174                 spin_lock_bh(&x->lock);
 175                 sport = encap->encap_sport;
 176                 dport = encap->encap_dport;
 177                 encap_type = encap->encap_type;
 178                 spin_unlock_bh(&x->lock);
 179
 180                 uh = (struct udphdr *)esph;
 181                 uh->source = sport;
 182                 uh->dest = dport;
 183                 uh->len = htons(skb->len - skb_transport_offset(skb));
 184                 uh->check = 0;
 185
 186                 switch (encap_type) {
 187                 default:
 188                 case UDP_ENCAP_ESPINUDP:
 189                         esph = (struct ip_esp_hdr *)(uh + 1);
 190                         break;
 191                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 192                         udpdata32 = (__be32 *)(uh + 1);
 193                         udpdata32[0] = udpdata32[1] = 0;
 194                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
 195                         break;
 196                 }
 197
 198                 *skb_mac_header(skb) = IPPROTO_UDP;
 199         }
 200
 201         esph->spi = x->id.spi;
 202         esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
 203
 204         sg_init_table(sg, nfrags);
 205         skb_to_sgvec(skb, sg,
 206                      esph->enc_data + crypto_aead_ivsize(aead) - skb->data,
 207                      clen + alen);
 208         sg_init_one(asg, esph, sizeof(*esph));
 209
 210         aead_givcrypt_set_callback(req, 0, esp_output_done, skb);
 211         aead_givcrypt_set_crypt(req, sg, sg, clen, iv);
 212         aead_givcrypt_set_assoc(req, asg, sizeof(*esph));
 213         aead_givcrypt_set_giv(req, esph->enc_data,
 214                               XFRM_SKB_CB(skb)->seq.output);
 215
 216         ESP_SKB_CB(skb)->tmp = tmp;
 217         err = crypto_aead_givencrypt(req);
 218         if (err == -EINPROGRESS)
 219                 goto error;
 220
 221         if (err == -EBUSY)
 222                 err = NET_XMIT_DROP;
 223
 224         kfree(tmp);
 225
 226 error:
 227         return err;
 228 }
 229
 230 static int esp_input_done2(struct sk_buff *skb, int err)
 231 {
 232         struct iphdr *iph;
 233         struct xfrm_state *x = xfrm_input_state(skb);
 234         struct esp_data *esp = x->data;
 235         struct crypto_aead *aead = esp->aead;
 236         int alen = crypto_aead_authsize(aead);
 237         int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
 238         int elen = skb->len - hlen;
 239         int ihl;
 240         u8 nexthdr[2];
 241         int padlen;
 242
 243         kfree(ESP_SKB_CB(skb)->tmp);
 244
 245         if (unlikely(err))
 246                 goto out;
 247
 248         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 249                 BUG();
 250
 251         err = -EINVAL;
 252         padlen = nexthdr[0];
 253         if (padlen + 2 + alen >= elen)
 254                 goto out;
 255
 256         /* ... check padding bits here. Silly. :-) */
 257
 258         iph = ip_hdr(skb);
 259         ihl = iph->ihl * 4;
 260
 261         if (x->encap) {
 262                 struct xfrm_encap_tmpl *encap = x->encap;
 263                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 264
 265                 /*
 266                  * 1) if the NAT-T peer's IP or port changed then
 267                  *    advertize the change to the keying daemon.
 268                  *    This is an inbound SA, so just compare
 269                  *    SRC ports.
 270                  */
 271                 if (iph->saddr != x->props.saddr.a4 ||
 272                     uh->source != encap->encap_sport) {
 273                         xfrm_address_t ipaddr;
 274
 275                         ipaddr.a4 = iph->saddr;
 276                         km_new_mapping(x, &ipaddr, uh->source);
 277
 278                         /* XXX: perhaps add an extra
 279                          * policy check here, to see
 280                          * if we should allow or
 281                          * reject a packet from a
 282                          * different source
 283                          * address/port.
 284                          */
 285                 }
 286
 287                 /*
 288                  * 2) ignore UDP/TCP checksums in case
 289                  *    of NAT-T in Transport Mode, or
 290                  *    perform other post-processing fixes
 291                  *    as per draft-ietf-ipsec-udp-encaps-06,
 292                  *    section 3.1.2
 293                  */
 294                 if (x->props.mode == XFRM_MODE_TRANSPORT)
 295                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 296         }
 297
 298         pskb_trim(skb, skb->len - alen - padlen - 2);
 299         __skb_pull(skb, hlen);
 300         skb_set_transport_header(skb, -ihl);
 301
 302         err = nexthdr[1];
 303
 304         /* RFC4303: Drop dummy packets without any error */
 305         if (err == IPPROTO_NONE)
 306                 err = -EINVAL;
 307
 308 out:
 309         return err;
 310 }
 311
 312 static void esp_input_done(struct crypto_async_request *base, int err)
 313 {
 314         struct sk_buff *skb = base->data;
 315
 316         xfrm_input_resume(skb, esp_input_done2(skb, err));
 317 }
 318
 319 /*
 320  * Note: detecting truncated vs. non-truncated authentication data is very
 321  * expensive, so we only support truncated data, which is the recommended
 322  * and common case.
 323  */
 324 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 325 {
 326         struct ip_esp_hdr *esph;
 327         struct esp_data *esp = x->data;
 328         struct crypto_aead *aead = esp->aead;
 329         struct aead_request *req;
 330         struct sk_buff *trailer;
 331         int elen = skb->len - sizeof(*esph) - crypto_aead_ivsize(aead);
 332         int nfrags;
 333         void *tmp;
 334         u8 *iv;
 335         struct scatterlist *sg;
 336         struct scatterlist *asg;
 337         int err = -EINVAL;
 338
 339         if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
 340                 goto out;
 341
 342         if (elen <= 0)
 343                 goto out;
 344
 345         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 346                 goto out;
 347         nfrags = err;
 348
 349         err = -ENOMEM;
 350         tmp = esp_alloc_tmp(aead, nfrags + 1);
 351         if (!tmp)
 352                 goto out;
 353
 354         ESP_SKB_CB(skb)->tmp = tmp;
 355         iv = esp_tmp_iv(aead, tmp);
 356         req = esp_tmp_req(aead, iv);
 357         asg = esp_req_sg(aead, req);
 358         sg = asg + 1;
 359
 360         skb->ip_summed = CHECKSUM_NONE;
 361
 362         esph = (struct ip_esp_hdr *)skb->data;
 363
 364         /* Get ivec. This can be wrong, check against another impls. */
 365         iv = esph->enc_data;
 366
 367         sg_init_table(sg, nfrags);
 368         skb_to_sgvec(skb, sg, sizeof(*esph) + crypto_aead_ivsize(aead), elen);
 369         sg_init_one(asg, esph, sizeof(*esph));
 370
 371         aead_request_set_callback(req, 0, esp_input_done, skb);
 372         aead_request_set_crypt(req, sg, sg, elen, iv);
 373         aead_request_set_assoc(req, asg, sizeof(*esph));
 374
 375         err = crypto_aead_decrypt(req);
 376         if (err == -EINPROGRESS)
 377                 goto out;
 378
 379         err = esp_input_done2(skb, err);
 380
 381 out:
 382         return err;
 383 }
 384
 385 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 386 {
 387         struct esp_data *esp = x->data;
 388         u32 blksize = ALIGN(crypto_aead_blocksize(esp->aead), 4);
 389         u32 align = max_t(u32, blksize, esp->padlen);
 390         u32 rem;
 391
 392         mtu -= x->props.header_len + crypto_aead_authsize(esp->aead);
 393         rem = mtu & (align - 1);
 394         mtu &= ~(align - 1);
 395
 396         switch (x->props.mode) {
 397         case XFRM_MODE_TUNNEL:
 398                 break;
 399         default:
 400         case XFRM_MODE_TRANSPORT:
 401                 /* The worst case */
 402                 mtu -= blksize - 4;
 403                 mtu += min_t(u32, blksize - 4, rem);
 404                 break;
 405         case XFRM_MODE_BEET:
 406                 /* The worst case. */
 407                 mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
 408                 break;
 409         }
 410
 411         return mtu - 2;
 412 }
 413
 414 static void esp4_err(struct sk_buff *skb, u32 info)
 415 {
 416         struct net *net = dev_net(skb->dev);
 417         struct iphdr *iph = (struct iphdr *)skb->data;
 418         struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
 419         struct xfrm_state *x;
 420
 421         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 422             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 423                 return;
 424
 425         x = xfrm_state_lookup(net, (xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 426         if (!x)
 427                 return;
 428         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 429                  ntohl(esph->spi), ntohl(iph->daddr));
 430         xfrm_state_put(x);
 431 }
 432
 433 static void esp_destroy(struct xfrm_state *x)
 434 {
 435         struct esp_data *esp = x->data;
 436
 437         if (!esp)
 438                 return;
 439
 440         crypto_free_aead(esp->aead);
 441         kfree(esp);
 442 }
 443
 444 static int esp_init_aead(struct xfrm_state *x)
 445 {
 446         struct esp_data *esp = x->data;
 447         struct crypto_aead *aead;
 448         int err;
 449
 450         aead = crypto_alloc_aead(x->aead->alg_name, 0, 0);
 451         err = PTR_ERR(aead);
 452         if (IS_ERR(aead))
 453                 goto error;
 454
 455         esp->aead = aead;
 456
 457         err = crypto_aead_setkey(aead, x->aead->alg_key,
 458                                  (x->aead->alg_key_len + 7) / 8);
 459         if (err)
 460                 goto error;
 461
 462         err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
 463         if (err)
 464                 goto error;
 465
 466 error:
 467         return err;
 468 }
 469
 470 static int esp_init_authenc(struct xfrm_state *x)
 471 {
 472         struct esp_data *esp = x->data;
 473         struct crypto_aead *aead;
 474         struct crypto_authenc_key_param *param;
 475         struct rtattr *rta;
 476         char *key;
 477         char *p;
 478         char authenc_name[CRYPTO_MAX_ALG_NAME];
 479         unsigned int keylen;
 480         int err;
 481
 482         err = -EINVAL;
 483         if (x->ealg == NULL)
 484                 goto error;
 485
 486         err = -ENAMETOOLONG;
 487         if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME, "authenc(%s,%s)",
 488                      x->aalg ? x->aalg->alg_name : "digest_null",
 489                      x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
 490                 goto error;
 491
 492         aead = crypto_alloc_aead(authenc_name, 0, 0);
 493         err = PTR_ERR(aead);
 494         if (IS_ERR(aead))
 495                 goto error;
 496
 497         esp->aead = aead;
 498
 499         keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
 500                  (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
 501         err = -ENOMEM;
 502         key = kmalloc(keylen, GFP_KERNEL);
 503         if (!key)
 504                 goto error;
 505
 506         p = key;
 507         rta = (void *)p;
 508         rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
 509         rta->rta_len = RTA_LENGTH(sizeof(*param));
 510         param = RTA_DATA(rta);
 511         p += RTA_SPACE(sizeof(*param));
 512
 513         if (x->aalg) {
 514                 struct xfrm_algo_desc *aalg_desc;
 515
 516                 memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
 517                 p += (x->aalg->alg_key_len + 7) / 8;
 518
 519                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 520                 BUG_ON(!aalg_desc);
 521
 522                 err = -EINVAL;
 523                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 524                     crypto_aead_authsize(aead)) {
 525                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 526                                  x->aalg->alg_name,
 527                                  crypto_aead_authsize(aead),
 528                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 529                         goto free_key;
 530                 }
 531
 532                 err = crypto_aead_setauthsize(
 533                         aead, aalg_desc->uinfo.auth.icv_truncbits / 8);
 534                 if (err)
 535                         goto free_key;
 536         }
 537
 538         param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
 539         memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);
 540
 541         err = crypto_aead_setkey(aead, key, keylen);
 542
 543 free_key:
 544         kfree(key);
 545
 546 error:
 547         return err;
 548 }
 549
 550 static int esp_init_state(struct xfrm_state *x)
 551 {
 552         struct esp_data *esp;
 553         struct crypto_aead *aead;
 554         u32 align;
 555         int err;
 556
 557         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 558         if (esp == NULL)
 559                 return -ENOMEM;
 560
 561         x->data = esp;
 562
 563         if (x->aead)
 564                 err = esp_init_aead(x);
 565         else
 566                 err = esp_init_authenc(x);
 567
 568         if (err)
 569                 goto error;
 570
 571         aead = esp->aead;
 572
 573         esp->padlen = 0;
 574
 575         x->props.header_len = sizeof(struct ip_esp_hdr) +
 576                               crypto_aead_ivsize(aead);
 577         if (x->props.mode == XFRM_MODE_TUNNEL)
 578                 x->props.header_len += sizeof(struct iphdr);
 579         else if (x->props.mode == XFRM_MODE_BEET && x->sel.family != AF_INET6)
 580                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 581         if (x->encap) {
 582                 struct xfrm_encap_tmpl *encap = x->encap;
 583
 584                 switch (encap->encap_type) {
 585                 default:
 586                         goto error;
 587                 case UDP_ENCAP_ESPINUDP:
 588                         x->props.header_len += sizeof(struct udphdr);
 589                         break;
 590                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 591                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 592                         break;
 593                 }
 594         }
 595
 596         align = ALIGN(crypto_aead_blocksize(aead), 4);
 597         if (esp->padlen)
 598                 align = max_t(u32, align, esp->padlen);
 599         x->props.trailer_len = align + 1 + crypto_aead_authsize(esp->aead);
 600
 601 error:
 602         return err;
 603 }
 604
 605 static const struct xfrm_type esp_type =
 606 {
 607         .description    = "ESP4",
 608         .owner          = THIS_MODULE,
 609         .proto          = IPPROTO_ESP,
 610         .flags          = XFRM_TYPE_REPLAY_PROT,
 611         .init_state     = esp_init_state,
 612         .destructor     = esp_destroy,
 613         .get_mtu        = esp4_get_mtu,
 614         .input          = esp_input,
 615         .output         = esp_output
 616 };
 617
 618 static const struct net_protocol esp4_protocol = {
 619         .handler        =       xfrm4_rcv,
 620         .err_handler    =       esp4_err,
 621         .no_policy      =       1,
 622         .netns_ok       =       1,
 623 };
 624
 625 static int __init esp4_init(void)
 626 {
 627         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 628                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 629                 return -EAGAIN;
 630         }
 631         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 632                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 633                 xfrm_unregister_type(&esp_type, AF_INET);
 634                 return -EAGAIN;
 635         }
 636         return 0;
 637 }
 638
 639 static void __exit esp4_fini(void)
 640 {
 641         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 642                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 643         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 644                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 645 }
 646
 647 module_init(esp4_init);
 648 module_exit(esp4_fini);
 649 MODULE_LICENSE("GPL");
 650 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);