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                         xfrm_audit_state_icvfail(x, skb, IPPROTO_ESP);
 195                         err = -EBADMSG;
 196                         goto unlock;
 197                 }
 198         }
 199
 200         esph = (struct ip_esp_hdr *)skb->data;
 201
 202         /* Get ivec. This can be wrong, check against another impls. */
 203         if (esp->conf.ivlen)
 204                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 205
 206         sg = &esp->sgbuf[0];
 207
 208         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 209                 err = -ENOMEM;
 210                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 211                 if (!sg)
 212                         goto unlock;
 213         }
 214         sg_init_table(sg, nfrags);
 215         skb_to_sgvec(skb, sg,
 216                      sizeof(*esph) + esp->conf.ivlen,
 217                      elen);
 218         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 219         if (unlikely(sg != &esp->sgbuf[0]))
 220                 kfree(sg);
 221
 222 unlock:
 223         spin_unlock(&x->lock);
 224
 225         if (unlikely(err))
 226                 goto out;
 227
 228         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 229                 BUG();
 230
 231         err = -EINVAL;
 232         padlen = nexthdr[0];
 233         if (padlen+2 >= elen)
 234                 goto out;
 235
 236         /* ... check padding bits here. Silly. :-) */
 237
 238         /* RFC4303: Drop dummy packets without any error */
 239         if (nexthdr[1] == IPPROTO_NONE)
 240                 goto out;
 241
 242         iph = ip_hdr(skb);
 243         ihl = iph->ihl * 4;
 244
 245         if (x->encap) {
 246                 struct xfrm_encap_tmpl *encap = x->encap;
 247                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 248
 249                 /*
 250                  * 1) if the NAT-T peer's IP or port changed then
 251                  *    advertize the change to the keying daemon.
 252                  *    This is an inbound SA, so just compare
 253                  *    SRC ports.
 254                  */
 255                 if (iph->saddr != x->props.saddr.a4 ||
 256                     uh->source != encap->encap_sport) {
 257                         xfrm_address_t ipaddr;
 258
 259                         ipaddr.a4 = iph->saddr;
 260                         km_new_mapping(x, &ipaddr, uh->source);
 261
 262                         /* XXX: perhaps add an extra
 263                          * policy check here, to see
 264                          * if we should allow or
 265                          * reject a packet from a
 266                          * different source
 267                          * address/port.
 268                          */
 269                 }
 270
 271                 /*
 272                  * 2) ignore UDP/TCP checksums in case
 273                  *    of NAT-T in Transport Mode, or
 274                  *    perform other post-processing fixes
 275                  *    as per draft-ietf-ipsec-udp-encaps-06,
 276                  *    section 3.1.2
 277                  */
 278                 if (x->props.mode == XFRM_MODE_TRANSPORT)
 279                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 280         }
 281
 282         pskb_trim(skb, skb->len - alen - padlen - 2);
 283         __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
 284         skb_set_transport_header(skb, -ihl);
 285
 286         return nexthdr[1];
 287
 288 out:
 289         return err;
 290 }
 291
 292 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 293 {
 294         struct esp_data *esp = x->data;
 295         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 296         u32 align = max_t(u32, blksize, esp->conf.padlen);
 297         u32 rem;
 298
 299         mtu -= x->props.header_len + esp->auth.icv_trunc_len;
 300         rem = mtu & (align - 1);
 301         mtu &= ~(align - 1);
 302
 303         switch (x->props.mode) {
 304         case XFRM_MODE_TUNNEL:
 305                 break;
 306         default:
 307         case XFRM_MODE_TRANSPORT:
 308                 /* The worst case */
 309                 mtu -= blksize - 4;
 310                 mtu += min_t(u32, blksize - 4, rem);
 311                 break;
 312         case XFRM_MODE_BEET:
 313                 /* The worst case. */
 314                 mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
 315                 break;
 316         }
 317
 318         return mtu - 2;
 319 }
 320
 321 static void esp4_err(struct sk_buff *skb, u32 info)
 322 {
 323         struct iphdr *iph = (struct iphdr*)skb->data;
 324         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 325         struct xfrm_state *x;
 326
 327         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 328             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 329                 return;
 330
 331         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 332         if (!x)
 333                 return;
 334         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 335                  ntohl(esph->spi), ntohl(iph->daddr));
 336         xfrm_state_put(x);
 337 }
 338
 339 static void esp_destroy(struct xfrm_state *x)
 340 {
 341         struct esp_data *esp = x->data;
 342
 343         if (!esp)
 344                 return;
 345
 346         crypto_free_blkcipher(esp->conf.tfm);
 347         esp->conf.tfm = NULL;
 348         kfree(esp->conf.ivec);
 349         esp->conf.ivec = NULL;
 350         crypto_free_hash(esp->auth.tfm);
 351         esp->auth.tfm = NULL;
 352         kfree(esp->auth.work_icv);
 353         esp->auth.work_icv = NULL;
 354         kfree(esp);
 355 }
 356
 357 static int esp_init_state(struct xfrm_state *x)
 358 {
 359         struct esp_data *esp = NULL;
 360         struct crypto_blkcipher *tfm;
 361         u32 align;
 362
 363         if (x->ealg == NULL)
 364                 goto error;
 365
 366         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 367         if (esp == NULL)
 368                 return -ENOMEM;
 369
 370         if (x->aalg) {
 371                 struct xfrm_algo_desc *aalg_desc;
 372                 struct crypto_hash *hash;
 373
 374                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 375                                          CRYPTO_ALG_ASYNC);
 376                 if (IS_ERR(hash))
 377                         goto error;
 378
 379                 esp->auth.tfm = hash;
 380                 if (crypto_hash_setkey(hash, x->aalg->alg_key,
 381                                        (x->aalg->alg_key_len + 7) / 8))
 382                         goto error;
 383
 384                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 385                 BUG_ON(!aalg_desc);
 386
 387                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 388                     crypto_hash_digestsize(hash)) {
 389                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 390                                  x->aalg->alg_name,
 391                                  crypto_hash_digestsize(hash),
 392                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 393                         goto error;
 394                 }
 395
 396                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 397                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 398
 399                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 400                 if (!esp->auth.work_icv)
 401                         goto error;
 402         }
 403
 404         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 405         if (IS_ERR(tfm))
 406                 goto error;
 407         esp->conf.tfm = tfm;
 408         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 409         esp->conf.padlen = 0;
 410         if (esp->conf.ivlen) {
 411                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 412                 if (unlikely(esp->conf.ivec == NULL))
 413                         goto error;
 414                 esp->conf.ivinitted = 0;
 415         }
 416         if (crypto_blkcipher_setkey(tfm, x->ealg->alg_key,
 417                                     (x->ealg->alg_key_len + 7) / 8))
 418                 goto error;
 419         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 420         if (x->props.mode == XFRM_MODE_TUNNEL)
 421                 x->props.header_len += sizeof(struct iphdr);
 422         else if (x->props.mode == XFRM_MODE_BEET)
 423                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 424         if (x->encap) {
 425                 struct xfrm_encap_tmpl *encap = x->encap;
 426
 427                 switch (encap->encap_type) {
 428                 default:
 429                         goto error;
 430                 case UDP_ENCAP_ESPINUDP:
 431                         x->props.header_len += sizeof(struct udphdr);
 432                         break;
 433                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 434                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 435                         break;
 436                 }
 437         }
 438         x->data = esp;
 439         align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 440         if (esp->conf.padlen)
 441                 align = max_t(u32, align, esp->conf.padlen);
 442         x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
 443         return 0;
 444
 445 error:
 446         x->data = esp;
 447         esp_destroy(x);
 448         x->data = NULL;
 449         return -EINVAL;
 450 }
 451
 452 static struct xfrm_type esp_type =
 453 {
 454         .description    = "ESP4",
 455         .owner          = THIS_MODULE,
 456         .proto          = IPPROTO_ESP,
 457         .flags          = XFRM_TYPE_REPLAY_PROT,
 458         .init_state     = esp_init_state,
 459         .destructor     = esp_destroy,
 460         .get_mtu        = esp4_get_mtu,
 461         .input          = esp_input,
 462         .output         = esp_output
 463 };
 464
 465 static struct net_protocol esp4_protocol = {
 466         .handler        =       xfrm4_rcv,
 467         .err_handler    =       esp4_err,
 468         .no_policy      =       1,
 469 };
 470
 471 static int __init esp4_init(void)
 472 {
 473         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 474                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 475                 return -EAGAIN;
 476         }
 477         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 478                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 479                 xfrm_unregister_type(&esp_type, AF_INET);
 480                 return -EAGAIN;
 481         }
 482         return 0;
 483 }
 484
 485 static void __exit esp4_fini(void)
 486 {
 487         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 488                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 489         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 490                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 491 }
 492
 493 module_init(esp4_init);
 494 module_exit(esp4_fini);
 495 MODULE_LICENSE("GPL");
 496 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);