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