net/ipv4/esp4.c

   1 #include <linux/config.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/pfkeyv2.h>
   9 #include <linux/random.h>
  10 #include <net/icmp.h>
  11 #include <net/udp.h>
  12
  13 /* decapsulation data for use when post-processing */
  14 struct esp_decap_data {
  15         xfrm_address_t  saddr;
  16         __u16           sport;
  17         __u8            proto;
  18 };
  19
  20 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  21 {
  22         int err;
  23         struct iphdr *top_iph;
  24         struct ip_esp_hdr *esph;
  25         struct crypto_tfm *tfm;
  26         struct esp_data *esp;
  27         struct sk_buff *trailer;
  28         int blksize;
  29         int clen;
  30         int alen;
  31         int nfrags;
  32
  33         /* Strip IP+ESP header. */
  34         __skb_pull(skb, skb->h.raw - skb->data);
  35         /* Now skb is pure payload to encrypt */
  36
  37         err = -ENOMEM;
  38
  39         /* Round to block size */
  40         clen = skb->len;
  41
  42         esp = x->data;
  43         alen = esp->auth.icv_trunc_len;
  44         tfm = esp->conf.tfm;
  45         blksize = (crypto_tfm_alg_blocksize(tfm) + 3) & ~3;
  46         clen = (clen + 2 + blksize-1)&~(blksize-1);
  47         if (esp->conf.padlen)
  48                 clen = (clen + esp->conf.padlen-1)&~(esp->conf.padlen-1);
  49
  50         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  51                 goto error;
  52
  53         /* Fill padding... */
  54         do {
  55                 int i;
  56                 for (i=0; i<clen-skb->len - 2; i++)
  57                         *(u8*)(trailer->tail + i) = i+1;
  58         } while (0);
  59         *(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
  60         pskb_put(skb, trailer, clen - skb->len);
  61
  62         __skb_push(skb, skb->data - skb->nh.raw);
  63         top_iph = skb->nh.iph;
  64         esph = (struct ip_esp_hdr *)(skb->nh.raw + top_iph->ihl*4);
  65         top_iph->tot_len = htons(skb->len + alen);
  66         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  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                 u32 *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 - top_iph->ihl*4);
  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 = (u32 *)(uh + 1);
  87                         udpdata32[0] = udpdata32[1] = 0;
  88                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  89                         break;
  90                 }
  91
  92                 top_iph->protocol = IPPROTO_UDP;
  93         } else
  94                 top_iph->protocol = IPPROTO_ESP;
  95
  96         esph->spi = x->id.spi;
  97         esph->seq_no = htonl(++x->replay.oseq);
  98
  99         if (esp->conf.ivlen)
 100                 crypto_cipher_set_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 101
 102         do {
 103                 struct scatterlist *sg = &esp->sgbuf[0];
 104
 105                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 106                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 107                         if (!sg)
 108                                 goto error;
 109                 }
 110                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 111                 crypto_cipher_encrypt(tfm, sg, sg, clen);
 112                 if (unlikely(sg != &esp->sgbuf[0]))
 113                         kfree(sg);
 114         } while (0);
 115
 116         if (esp->conf.ivlen) {
 117                 memcpy(esph->enc_data, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 118                 crypto_cipher_get_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 119         }
 120
 121         if (esp->auth.icv_full_len) {
 122                 esp->auth.icv(esp, skb, (u8*)esph-skb->data,
 123                               sizeof(struct ip_esp_hdr) + esp->conf.ivlen+clen, trailer->tail);
 124                 pskb_put(skb, trailer, alen);
 125         }
 126
 127         ip_send_check(top_iph);
 128
 129         err = 0;
 130
 131 error:
 132         return err;
 133 }
 134
 135 /*
 136  * Note: detecting truncated vs. non-truncated authentication data is very
 137  * expensive, so we only support truncated data, which is the recommended
 138  * and common case.
 139  */
 140 static int esp_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 141 {
 142         struct iphdr *iph;
 143         struct ip_esp_hdr *esph;
 144         struct esp_data *esp = x->data;
 145         struct sk_buff *trailer;
 146         int blksize = crypto_tfm_alg_blocksize(esp->conf.tfm);
 147         int alen = esp->auth.icv_trunc_len;
 148         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 149         int nfrags;
 150         int encap_len = 0;
 151
 152         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 153                 goto out;
 154
 155         if (elen <= 0 || (elen & (blksize-1)))
 156                 goto out;
 157
 158         /* If integrity check is required, do this. */
 159         if (esp->auth.icv_full_len) {
 160                 u8 sum[esp->auth.icv_full_len];
 161                 u8 sum1[alen];
 162
 163                 esp->auth.icv(esp, skb, 0, skb->len-alen, sum);
 164
 165                 if (skb_copy_bits(skb, skb->len-alen, sum1, alen))
 166                         BUG();
 167
 168                 if (unlikely(memcmp(sum, sum1, alen))) {
 169                         x->stats.integrity_failed++;
 170                         goto out;
 171                 }
 172         }
 173
 174         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 175                 goto out;
 176
 177         skb->ip_summed = CHECKSUM_NONE;
 178
 179         esph = (struct ip_esp_hdr*)skb->data;
 180         iph = skb->nh.iph;
 181
 182         /* Get ivec. This can be wrong, check against another impls. */
 183         if (esp->conf.ivlen)
 184                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 185
 186         {
 187                 u8 nexthdr[2];
 188                 struct scatterlist *sg = &esp->sgbuf[0];
 189                 u8 workbuf[60];
 190                 int padlen;
 191
 192                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 193                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 194                         if (!sg)
 195                                 goto out;
 196                 }
 197                 skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 198                 crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 199                 if (unlikely(sg != &esp->sgbuf[0]))
 200                         kfree(sg);
 201
 202                 if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 203                         BUG();
 204
 205                 padlen = nexthdr[0];
 206                 if (padlen+2 >= elen)
 207                         goto out;
 208
 209                 /* ... check padding bits here. Silly. :-) */
 210
 211                 if (x->encap && decap && decap->decap_type) {
 212                         struct esp_decap_data *encap_data;
 213                         struct udphdr *uh = (struct udphdr *) (iph+1);
 214
 215                         encap_data = (struct esp_decap_data *) (decap->decap_data);
 216                         encap_data->proto = 0;
 217
 218                         switch (decap->decap_type) {
 219                         case UDP_ENCAP_ESPINUDP:
 220                         case UDP_ENCAP_ESPINUDP_NON_IKE:
 221                                 encap_data->proto = AF_INET;
 222                                 encap_data->saddr.a4 = iph->saddr;
 223                                 encap_data->sport = uh->source;
 224                                 encap_len = (void*)esph - (void*)uh;
 225                                 break;
 226
 227                         default:
 228                                 goto out;
 229                         }
 230                 }
 231
 232                 iph->protocol = nexthdr[1];
 233                 pskb_trim(skb, skb->len - alen - padlen - 2);
 234                 memcpy(workbuf, skb->nh.raw, iph->ihl*4);
 235                 skb->h.raw = skb_pull(skb, sizeof(struct ip_esp_hdr) + esp->conf.ivlen);
 236                 skb->nh.raw += encap_len + sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 237                 memcpy(skb->nh.raw, workbuf, iph->ihl*4);
 238                 skb->nh.iph->tot_len = htons(skb->len);
 239         }
 240
 241         return 0;
 242
 243 out:
 244         return -EINVAL;
 245 }
 246
 247 static int esp_post_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 248 {
 249
 250         if (x->encap) {
 251                 struct xfrm_encap_tmpl *encap;
 252                 struct esp_decap_data *decap_data;
 253
 254                 encap = x->encap;
 255                 decap_data = (struct esp_decap_data *)(decap->decap_data);
 256
 257                 /* first, make sure that the decap type == the encap type */
 258                 if (encap->encap_type != decap->decap_type)
 259                         return -EINVAL;
 260
 261                 switch (encap->encap_type) {
 262                 default:
 263                 case UDP_ENCAP_ESPINUDP:
 264                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 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 (decap_data->proto == AF_INET &&
 272                             (decap_data->saddr.a4 != x->props.saddr.a4 ||
 273                              decap_data->sport != encap->encap_sport)) {
 274                                 xfrm_address_t ipaddr;
 275
 276                                 ipaddr.a4 = decap_data->saddr.a4;
 277                                 km_new_mapping(x, &ipaddr, decap_data->sport);
 278
 279                                 /* XXX: perhaps add an extra
 280                                  * policy check here, to see
 281                                  * if we should allow or
 282                                  * reject a packet from a
 283                                  * different source
 284                                  * address/port.
 285                                  */
 286                         }
 287
 288                         /*
 289                          * 2) ignore UDP/TCP checksums in case
 290                          *    of NAT-T in Transport Mode, or
 291                          *    perform other post-processing fixes
 292                          *    as per * draft-ietf-ipsec-udp-encaps-06,
 293                          *    section 3.1.2
 294                          */
 295                         if (!x->props.mode)
 296                                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 297
 298                         break;
 299                 }
 300         }
 301         return 0;
 302 }
 303
 304 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 305 {
 306         struct esp_data *esp = x->data;
 307         u32 blksize = crypto_tfm_alg_blocksize(esp->conf.tfm);
 308
 309         if (x->props.mode) {
 310                 mtu = (mtu + 2 + blksize-1)&~(blksize-1);
 311         } else {
 312                 /* The worst case. */
 313                 mtu += 2 + blksize;
 314         }
 315         if (esp->conf.padlen)
 316                 mtu = (mtu + esp->conf.padlen-1)&~(esp->conf.padlen-1);
 317
 318         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 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 (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 328             skb->h.icmph->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_tfm(esp->conf.tfm);
 347         esp->conf.tfm = NULL;
 348         kfree(esp->conf.ivec);
 349         esp->conf.ivec = NULL;
 350         crypto_free_tfm(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
 361         /* null auth and encryption can have zero length keys */
 362         if (x->aalg) {
 363                 if (x->aalg->alg_key_len > 512)
 364                         goto error;
 365         }
 366         if (x->ealg == NULL)
 367                 goto error;
 368
 369         esp = kmalloc(sizeof(*esp), GFP_KERNEL);
 370         if (esp == NULL)
 371                 return -ENOMEM;
 372
 373         memset(esp, 0, sizeof(*esp));
 374
 375         if (x->aalg) {
 376                 struct xfrm_algo_desc *aalg_desc;
 377
 378                 esp->auth.key = x->aalg->alg_key;
 379                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 380                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 381                 if (esp->auth.tfm == NULL)
 382                         goto error;
 383                 esp->auth.icv = esp_hmac_digest;
 384
 385                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 386                 BUG_ON(!aalg_desc);
 387
 388                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 389                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 390                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 391                                  x->aalg->alg_name,
 392                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 393                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 394                         goto error;
 395                 }
 396
 397                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 398                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 399
 400                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 401                 if (!esp->auth.work_icv)
 402                         goto error;
 403         }
 404         esp->conf.key = x->ealg->alg_key;
 405         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 406         if (x->props.ealgo == SADB_EALG_NULL)
 407                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 408         else
 409                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 410         if (esp->conf.tfm == NULL)
 411                 goto error;
 412         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 413         esp->conf.padlen = 0;
 414         if (esp->conf.ivlen) {
 415                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 416                 if (unlikely(esp->conf.ivec == NULL))
 417                         goto error;
 418                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 419         }
 420         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 421                 goto error;
 422         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 423         if (x->props.mode)
 424                 x->props.header_len += sizeof(struct iphdr);
 425         if (x->encap) {
 426                 struct xfrm_encap_tmpl *encap = x->encap;
 427
 428                 switch (encap->encap_type) {
 429                 default:
 430                         goto error;
 431                 case UDP_ENCAP_ESPINUDP:
 432                         x->props.header_len += sizeof(struct udphdr);
 433                         break;
 434                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 435                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 436                         break;
 437                 }
 438         }
 439         x->data = esp;
 440         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 441         return 0;
 442
 443 error:
 444         x->data = esp;
 445         esp_destroy(x);
 446         x->data = NULL;
 447         return -EINVAL;
 448 }
 449
 450 static struct xfrm_type esp_type =
 451 {
 452         .description    = "ESP4",
 453         .owner          = THIS_MODULE,
 454         .proto          = IPPROTO_ESP,
 455         .init_state     = esp_init_state,
 456         .destructor     = esp_destroy,
 457         .get_max_size   = esp4_get_max_size,
 458         .input          = esp_input,
 459         .post_input     = esp_post_input,
 460         .output         = esp_output
 461 };
 462
 463 static struct net_protocol esp4_protocol = {
 464         .handler        =       xfrm4_rcv,
 465         .err_handler    =       esp4_err,
 466         .no_policy      =       1,
 467 };
 468
 469 static int __init esp4_init(void)
 470 {
 471         struct xfrm_decap_state decap;
 472
 473         if (sizeof(struct esp_decap_data)  >
 474             sizeof(decap.decap_data)) {
 475                 extern void decap_data_too_small(void);
 476
 477                 decap_data_too_small();
 478         }
 479
 480         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 481                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 482                 return -EAGAIN;
 483         }
 484         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 485                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 486                 xfrm_unregister_type(&esp_type, AF_INET);
 487                 return -EAGAIN;
 488         }
 489         return 0;
 490 }
 491
 492 static void __exit esp4_fini(void)
 493 {
 494         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 495                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 496         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 497                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 498 }
 499
 500 module_init(esp4_init);
 501 module_exit(esp4_fini);
 502 MODULE_LICENSE("GPL");