net/ipv4/esp4.c

   1 #include <linux/err.h>
   2 #include <linux/module.h>
   3 #include <net/ip.h>
   4 #include <net/xfrm.h>
   5 #include <net/esp.h>
   6 #include <linux/scatterlist.h>
   7 #include <linux/crypto.h>
   8 #include <linux/kernel.h>
   9 #include <linux/pfkeyv2.h>
  10 #include <linux/random.h>
  11 #include <linux/spinlock.h>
  12 #include <linux/in6.h>
  13 #include <net/icmp.h>
  14 #include <net/protocol.h>
  15 #include <net/udp.h>
  16
  17 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  18 {
  19         int err;
  20         struct ip_esp_hdr *esph;
  21         struct crypto_blkcipher *tfm;
  22         struct blkcipher_desc desc;
  23         struct esp_data *esp;
  24         struct sk_buff *trailer;
  25         u8 *tail;
  26         int blksize;
  27         int clen;
  28         int alen;
  29         int nfrags;
  30
  31         /* skb is pure payload to encrypt */
  32
  33         err = -ENOMEM;
  34
  35         /* Round to block size */
  36         clen = skb->len;
  37
  38         esp = x->data;
  39         alen = esp->auth.icv_trunc_len;
  40         tfm = esp->conf.tfm;
  41         desc.tfm = tfm;
  42         desc.flags = 0;
  43         blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
  44         clen = ALIGN(clen + 2, blksize);
  45         if (esp->conf.padlen)
  46                 clen = ALIGN(clen, esp->conf.padlen);
  47
  48         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  49                 goto error;
  50
  51         /* Fill padding... */
  52         tail = skb_tail_pointer(trailer);
  53         do {
  54                 int i;
  55                 for (i=0; i<clen-skb->len - 2; i++)
  56                         tail[i] = i + 1;
  57         } while (0);
  58         tail[clen - skb->len - 2] = (clen - skb->len) - 2;
  59         pskb_put(skb, trailer, clen - skb->len);
  60
  61         skb_push(skb, -skb_network_offset(skb));
  62         esph = ip_esp_hdr(skb);
  63         *(skb_tail_pointer(trailer) - 1) = *skb_mac_header(skb);
  64         *skb_mac_header(skb) = IPPROTO_ESP;
  65
  66         spin_lock_bh(&x->lock);
  67
  68         /* this is non-NULL only with UDP Encapsulation */
  69         if (x->encap) {
  70                 struct xfrm_encap_tmpl *encap = x->encap;
  71                 struct udphdr *uh;
  72                 __be32 *udpdata32;
  73
  74                 uh = (struct udphdr *)esph;
  75                 uh->source = encap->encap_sport;
  76                 uh->dest = encap->encap_dport;
  77                 uh->len = htons(skb->len + alen - skb_transport_offset(skb));
  78                 uh->check = 0;
  79
  80                 switch (encap->encap_type) {
  81                 default:
  82                 case UDP_ENCAP_ESPINUDP:
  83                         esph = (struct ip_esp_hdr *)(uh + 1);
  84                         break;
  85                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  86                         udpdata32 = (__be32 *)(uh + 1);
  87                         udpdata32[0] = udpdata32[1] = 0;
  88                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  89                         break;
  90                 }
  91
  92                 *skb_mac_header(skb) = IPPROTO_UDP;
  93         }
  94
  95         esph->spi = x->id.spi;
  96         esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
  97
  98         if (esp->conf.ivlen) {
  99                 if (unlikely(!esp->conf.ivinitted)) {
 100                         get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 101                         esp->conf.ivinitted = 1;
 102                 }
 103                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 104         }
 105
 106         do {
 107                 struct scatterlist *sg = &esp->sgbuf[0];
 108
 109                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 110                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 111                         if (!sg)
 112                                 goto unlock;
 113                 }
 114                 sg_init_table(sg, nfrags);
 115                 skb_to_sgvec(skb, sg,
 116                              esph->enc_data +
 117                              esp->conf.ivlen -
 118                              skb->data, clen);
 119                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
 120                 if (unlikely(sg != &esp->sgbuf[0]))
 121                         kfree(sg);
 122         } while (0);
 123
 124         if (unlikely(err))
 125                 goto unlock;
 126
 127         if (esp->conf.ivlen) {
 128                 memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
 129                 crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 130         }
 131
 132         if (esp->auth.icv_full_len) {
 133                 err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
 134                                      sizeof(*esph) + esp->conf.ivlen + clen);
 135                 memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
 136         }
 137
 138 unlock:
 139         spin_unlock_bh(&x->lock);
 140
 141 error:
 142         return err;
 143 }
 144
 145 /*
 146  * Note: detecting truncated vs. non-truncated authentication data is very
 147  * expensive, so we only support truncated data, which is the recommended
 148  * and common case.
 149  */
 150 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 151 {
 152         struct iphdr *iph;
 153         struct ip_esp_hdr *esph;
 154         struct esp_data *esp = x->data;
 155         struct crypto_blkcipher *tfm = esp->conf.tfm;
 156         struct blkcipher_desc desc = { .tfm = tfm };
 157         struct sk_buff *trailer;
 158         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 159         int alen = esp->auth.icv_trunc_len;
 160         int elen = skb->len - sizeof(*esph) - esp->conf.ivlen - alen;
 161         int nfrags;
 162         int ihl;
 163         u8 nexthdr[2];
 164         struct scatterlist *sg;
 165         int padlen;
 166         int err = -EINVAL;
 167
 168         if (!pskb_may_pull(skb, sizeof(*esph)))
 169                 goto out;
 170
 171         if (elen <= 0 || (elen & (blksize-1)))
 172                 goto out;
 173
 174         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 175                 goto out;
 176         nfrags = err;
 177
 178         skb->ip_summed = CHECKSUM_NONE;
 179
 180         spin_lock(&x->lock);
 181
 182         /* If integrity check is required, do this. */
 183         if (esp->auth.icv_full_len) {
 184                 u8 sum[alen];
 185
 186                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 187                 if (err)
 188                         goto unlock;
 189
 190                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 191                         BUG();
 192
 193                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 194                         err = -EBADMSG;
 195                         goto unlock;
 196                 }
 197         }
 198
 199         esph = (struct ip_esp_hdr *)skb->data;
 200
 201         /* Get ivec. This can be wrong, check against another impls. */
 202         if (esp->conf.ivlen)
 203                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 204
 205         sg = &esp->sgbuf[0];
 206
 207         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 208                 err = -ENOMEM;
 209                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 210                 if (!sg)
 211                         goto unlock;
 212         }
 213         sg_init_table(sg, nfrags);
 214         skb_to_sgvec(skb, sg,
 215                      sizeof(*esph) + esp->conf.ivlen,
 216                      elen);
 217         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 218         if (unlikely(sg != &esp->sgbuf[0]))
 219                 kfree(sg);
 220
 221 unlock:
 222         spin_unlock(&x->lock);
 223
 224         if (unlikely(err))
 225                 goto out;
 226
 227         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 228                 BUG();
 229
 230         err = -EINVAL;
 231         padlen = nexthdr[0];
 232         if (padlen+2 >= elen)
 233                 goto out;
 234
 235         /* ... check padding bits here. Silly. :-) */
 236
 237         /* RFC4303: Drop dummy packets without any error */
 238         if (nexthdr[1] == IPPROTO_NONE)
 239                 goto out;
 240
 241         iph = ip_hdr(skb);
 242         ihl = iph->ihl * 4;
 243
 244         if (x->encap) {
 245                 struct xfrm_encap_tmpl *encap = x->encap;
 246                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 247
 248                 /*
 249                  * 1) if the NAT-T peer's IP or port changed then
 250                  *    advertize the change to the keying daemon.
 251                  *    This is an inbound SA, so just compare
 252                  *    SRC ports.
 253                  */
 254                 if (iph->saddr != x->props.saddr.a4 ||
 255                     uh->source != encap->encap_sport) {
 256                         xfrm_address_t ipaddr;
 257
 258                         ipaddr.a4 = iph->saddr;
 259                         km_new_mapping(x, &ipaddr, uh->source);
 260
 261                         /* XXX: perhaps add an extra
 262                          * policy check here, to see
 263                          * if we should allow or
 264                          * reject a packet from a
 265                          * different source
 266                          * address/port.
 267                          */
 268                 }
 269
 270                 /*
 271                  * 2) ignore UDP/TCP checksums in case
 272                  *    of NAT-T in Transport Mode, or
 273                  *    perform other post-processing fixes
 274                  *    as per draft-ietf-ipsec-udp-encaps-06,
 275                  *    section 3.1.2
 276                  */
 277                 if (x->props.mode == XFRM_MODE_TRANSPORT)
 278                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 279         }
 280
 281         pskb_trim(skb, skb->len - alen - padlen - 2);
 282         __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
 283         skb_set_transport_header(skb, -ihl);
 284
 285         return nexthdr[1];
 286
 287 out:
 288         return err;
 289 }
 290
 291 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 292 {
 293         struct esp_data *esp = x->data;
 294         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 295         u32 align = max_t(u32, blksize, esp->conf.padlen);
 296         u32 rem;
 297
 298         mtu -= x->props.header_len + esp->auth.icv_trunc_len;
 299         rem = mtu & (align - 1);
 300         mtu &= ~(align - 1);
 301
 302         switch (x->props.mode) {
 303         case XFRM_MODE_TUNNEL:
 304                 break;
 305         default:
 306         case XFRM_MODE_TRANSPORT:
 307                 /* The worst case */
 308                 mtu -= blksize - 4;
 309                 mtu += min_t(u32, blksize - 4, rem);
 310                 break;
 311         case XFRM_MODE_BEET:
 312                 /* The worst case. */
 313                 mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
 314                 break;
 315         }
 316
 317         return mtu - 2;
 318 }
 319
 320 static void esp4_err(struct sk_buff *skb, u32 info)
 321 {
 322         struct iphdr *iph = (struct iphdr*)skb->data;
 323         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 324         struct xfrm_state *x;
 325
 326         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 327             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 328                 return;
 329
 330         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 331         if (!x)
 332                 return;
 333         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 334                  ntohl(esph->spi), ntohl(iph->daddr));
 335         xfrm_state_put(x);
 336 }
 337
 338 static void esp_destroy(struct xfrm_state *x)
 339 {
 340         struct esp_data *esp = x->data;
 341
 342         if (!esp)
 343                 return;
 344
 345         crypto_free_blkcipher(esp->conf.tfm);
 346         esp->conf.tfm = NULL;
 347         kfree(esp->conf.ivec);
 348         esp->conf.ivec = NULL;
 349         crypto_free_hash(esp->auth.tfm);
 350         esp->auth.tfm = NULL;
 351         kfree(esp->auth.work_icv);
 352         esp->auth.work_icv = NULL;
 353         kfree(esp);
 354 }
 355
 356 static int esp_init_state(struct xfrm_state *x)
 357 {
 358         struct esp_data *esp = NULL;
 359         struct crypto_blkcipher *tfm;
 360         u32 align;
 361
 362         if (x->ealg == NULL)
 363                 goto error;
 364
 365         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 366         if (esp == NULL)
 367                 return -ENOMEM;
 368
 369         if (x->aalg) {
 370                 struct xfrm_algo_desc *aalg_desc;
 371                 struct crypto_hash *hash;
 372
 373                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 374                                          CRYPTO_ALG_ASYNC);
 375                 if (IS_ERR(hash))
 376                         goto error;
 377
 378                 esp->auth.tfm = hash;
 379                 if (crypto_hash_setkey(hash, x->aalg->alg_key,
 380                                        (x->aalg->alg_key_len + 7) / 8))
 381                         goto error;
 382
 383                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 384                 BUG_ON(!aalg_desc);
 385
 386                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 387                     crypto_hash_digestsize(hash)) {
 388                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 389                                  x->aalg->alg_name,
 390                                  crypto_hash_digestsize(hash),
 391                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 392                         goto error;
 393                 }
 394
 395                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 396                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 397
 398                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 399                 if (!esp->auth.work_icv)
 400                         goto error;
 401         }
 402
 403         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 404         if (IS_ERR(tfm))
 405                 goto error;
 406         esp->conf.tfm = tfm;
 407         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 408         esp->conf.padlen = 0;
 409         if (esp->conf.ivlen) {
 410                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 411                 if (unlikely(esp->conf.ivec == NULL))
 412                         goto error;
 413                 esp->conf.ivinitted = 0;
 414         }
 415         if (crypto_blkcipher_setkey(tfm, x->ealg->alg_key,
 416                                     (x->ealg->alg_key_len + 7) / 8))
 417                 goto error;
 418         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 419         if (x->props.mode == XFRM_MODE_TUNNEL)
 420                 x->props.header_len += sizeof(struct iphdr);
 421         else if (x->props.mode == XFRM_MODE_BEET)
 422                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 423         if (x->encap) {
 424                 struct xfrm_encap_tmpl *encap = x->encap;
 425
 426                 switch (encap->encap_type) {
 427                 default:
 428                         goto error;
 429                 case UDP_ENCAP_ESPINUDP:
 430                         x->props.header_len += sizeof(struct udphdr);
 431                         break;
 432                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 433                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 434                         break;
 435                 }
 436         }
 437         x->data = esp;
 438         align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 439         if (esp->conf.padlen)
 440                 align = max_t(u32, align, esp->conf.padlen);
 441         x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
 442         return 0;
 443
 444 error:
 445         x->data = esp;
 446         esp_destroy(x);
 447         x->data = NULL;
 448         return -EINVAL;
 449 }
 450
 451 static struct xfrm_type esp_type =
 452 {
 453         .description    = "ESP4",
 454         .owner          = THIS_MODULE,
 455         .proto          = IPPROTO_ESP,
 456         .flags          = XFRM_TYPE_REPLAY_PROT,
 457         .init_state     = esp_init_state,
 458         .destructor     = esp_destroy,
 459         .get_mtu        = esp4_get_mtu,
 460         .input          = esp_input,
 461         .output         = esp_output
 462 };
 463
 464 static struct net_protocol esp4_protocol = {
 465         .handler        =       xfrm4_rcv,
 466         .err_handler    =       esp4_err,
 467         .no_policy      =       1,
 468 };
 469
 470 static int __init esp4_init(void)
 471 {
 472         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 473                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 474                 return -EAGAIN;
 475         }
 476         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 477                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 478                 xfrm_unregister_type(&esp_type, AF_INET);
 479                 return -EAGAIN;
 480         }
 481         return 0;
 482 }
 483
 484 static void __exit esp4_fini(void)
 485 {
 486         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 487                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 488         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 489                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 490 }
 491
 492 module_init(esp4_init);
 493 module_exit(esp4_fini);
 494 MODULE_LICENSE("GPL");
 495 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);