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/kernel.h>
   9 #include <linux/pfkeyv2.h>
  10 #include <linux/random.h>
  11 #include <net/icmp.h>
  12 #include <net/udp.h>
  13
  14 /* decapsulation data for use when post-processing */
  15 struct esp_decap_data {
  16         xfrm_address_t  saddr;
  17         __u16           sport;
  18         __u8            proto;
  19 };
  20
  21 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  22 {
  23         int err;
  24         struct iphdr *top_iph;
  25         struct ip_esp_hdr *esph;
  26         struct crypto_tfm *tfm;
  27         struct esp_data *esp;
  28         struct sk_buff *trailer;
  29         int blksize;
  30         int clen;
  31         int alen;
  32         int nfrags;
  33
  34         /* Strip IP+ESP header. */
  35         __skb_pull(skb, skb->h.raw - skb->data);
  36         /* Now skb is pure payload to encrypt */
  37
  38         err = -ENOMEM;
  39
  40         /* Round to block size */
  41         clen = skb->len;
  42
  43         esp = x->data;
  44         alen = esp->auth.icv_trunc_len;
  45         tfm = esp->conf.tfm;
  46         blksize = ALIGN(crypto_tfm_alg_blocksize(tfm), 4);
  47         clen = ALIGN(clen + 2, blksize);
  48         if (esp->conf.padlen)
  49                 clen = ALIGN(clen, esp->conf.padlen);
  50
  51         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  52                 goto error;
  53
  54         /* Fill padding... */
  55         do {
  56                 int i;
  57                 for (i=0; i<clen-skb->len - 2; i++)
  58                         *(u8*)(trailer->tail + i) = i+1;
  59         } while (0);
  60         *(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
  61         pskb_put(skb, trailer, clen - skb->len);
  62
  63         __skb_push(skb, skb->data - skb->nh.raw);
  64         top_iph = skb->nh.iph;
  65         esph = (struct ip_esp_hdr *)(skb->nh.raw + top_iph->ihl*4);
  66         top_iph->tot_len = htons(skb->len + alen);
  67         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  68
  69         /* this is non-NULL only with UDP Encapsulation */
  70         if (x->encap) {
  71                 struct xfrm_encap_tmpl *encap = x->encap;
  72                 struct udphdr *uh;
  73                 u32 *udpdata32;
  74
  75                 uh = (struct udphdr *)esph;
  76                 uh->source = encap->encap_sport;
  77                 uh->dest = encap->encap_dport;
  78                 uh->len = htons(skb->len + alen - top_iph->ihl*4);
  79                 uh->check = 0;
  80
  81                 switch (encap->encap_type) {
  82                 default:
  83                 case UDP_ENCAP_ESPINUDP:
  84                         esph = (struct ip_esp_hdr *)(uh + 1);
  85                         break;
  86                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  87                         udpdata32 = (u32 *)(uh + 1);
  88                         udpdata32[0] = udpdata32[1] = 0;
  89                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  90                         break;
  91                 }
  92
  93                 top_iph->protocol = IPPROTO_UDP;
  94         } else
  95                 top_iph->protocol = IPPROTO_ESP;
  96
  97         esph->spi = x->id.spi;
  98         esph->seq_no = htonl(++x->replay.oseq);
  99
 100         if (esp->conf.ivlen)
 101                 crypto_cipher_set_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 102
 103         do {
 104                 struct scatterlist *sg = &esp->sgbuf[0];
 105
 106                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 107                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 108                         if (!sg)
 109                                 goto error;
 110                 }
 111                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 112                 crypto_cipher_encrypt(tfm, sg, sg, clen);
 113                 if (unlikely(sg != &esp->sgbuf[0]))
 114                         kfree(sg);
 115         } while (0);
 116
 117         if (esp->conf.ivlen) {
 118                 memcpy(esph->enc_data, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 119                 crypto_cipher_get_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 120         }
 121
 122         if (esp->auth.icv_full_len) {
 123                 esp->auth.icv(esp, skb, (u8*)esph-skb->data,
 124                               sizeof(struct ip_esp_hdr) + esp->conf.ivlen+clen, trailer->tail);
 125                 pskb_put(skb, trailer, alen);
 126         }
 127
 128         ip_send_check(top_iph);
 129
 130         err = 0;
 131
 132 error:
 133         return err;
 134 }
 135
 136 /*
 137  * Note: detecting truncated vs. non-truncated authentication data is very
 138  * expensive, so we only support truncated data, which is the recommended
 139  * and common case.
 140  */
 141 static int esp_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 142 {
 143         struct iphdr *iph;
 144         struct ip_esp_hdr *esph;
 145         struct esp_data *esp = x->data;
 146         struct sk_buff *trailer;
 147         int blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 148         int alen = esp->auth.icv_trunc_len;
 149         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 150         int nfrags;
 151         int encap_len = 0;
 152
 153         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 154                 goto out;
 155
 156         if (elen <= 0 || (elen & (blksize-1)))
 157                 goto out;
 158
 159         /* If integrity check is required, do this. */
 160         if (esp->auth.icv_full_len) {
 161                 u8 sum[esp->auth.icv_full_len];
 162                 u8 sum1[alen];
 163
 164                 esp->auth.icv(esp, skb, 0, skb->len-alen, sum);
 165
 166                 if (skb_copy_bits(skb, skb->len-alen, sum1, alen))
 167                         BUG();
 168
 169                 if (unlikely(memcmp(sum, sum1, alen))) {
 170                         x->stats.integrity_failed++;
 171                         goto out;
 172                 }
 173         }
 174
 175         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 176                 goto out;
 177
 178         skb->ip_summed = CHECKSUM_NONE;
 179
 180         esph = (struct ip_esp_hdr*)skb->data;
 181         iph = skb->nh.iph;
 182
 183         /* Get ivec. This can be wrong, check against another impls. */
 184         if (esp->conf.ivlen)
 185                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 186
 187         {
 188                 u8 nexthdr[2];
 189                 struct scatterlist *sg = &esp->sgbuf[0];
 190                 u8 workbuf[60];
 191                 int padlen;
 192
 193                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 194                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 195                         if (!sg)
 196                                 goto out;
 197                 }
 198                 skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 199                 crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 200                 if (unlikely(sg != &esp->sgbuf[0]))
 201                         kfree(sg);
 202
 203                 if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 204                         BUG();
 205
 206                 padlen = nexthdr[0];
 207                 if (padlen+2 >= elen)
 208                         goto out;
 209
 210                 /* ... check padding bits here. Silly. :-) */
 211
 212                 if (x->encap && decap && decap->decap_type) {
 213                         struct esp_decap_data *encap_data;
 214                         struct udphdr *uh = (struct udphdr *) (iph+1);
 215
 216                         encap_data = (struct esp_decap_data *) (decap->decap_data);
 217                         encap_data->proto = 0;
 218
 219                         switch (decap->decap_type) {
 220                         case UDP_ENCAP_ESPINUDP:
 221                         case UDP_ENCAP_ESPINUDP_NON_IKE:
 222                                 encap_data->proto = AF_INET;
 223                                 encap_data->saddr.a4 = iph->saddr;
 224                                 encap_data->sport = uh->source;
 225                                 encap_len = (void*)esph - (void*)uh;
 226                                 break;
 227
 228                         default:
 229                                 goto out;
 230                         }
 231                 }
 232
 233                 iph->protocol = nexthdr[1];
 234                 pskb_trim(skb, skb->len - alen - padlen - 2);
 235                 memcpy(workbuf, skb->nh.raw, iph->ihl*4);
 236                 skb->h.raw = skb_pull(skb, sizeof(struct ip_esp_hdr) + esp->conf.ivlen);
 237                 skb->nh.raw += encap_len + sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 238                 memcpy(skb->nh.raw, workbuf, iph->ihl*4);
 239                 skb->nh.iph->tot_len = htons(skb->len);
 240         }
 241
 242         return 0;
 243
 244 out:
 245         return -EINVAL;
 246 }
 247
 248 static int esp_post_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 249 {
 250
 251         if (x->encap) {
 252                 struct xfrm_encap_tmpl *encap;
 253                 struct esp_decap_data *decap_data;
 254
 255                 encap = x->encap;
 256                 decap_data = (struct esp_decap_data *)(decap->decap_data);
 257
 258                 /* first, make sure that the decap type == the encap type */
 259                 if (encap->encap_type != decap->decap_type)
 260                         return -EINVAL;
 261
 262                 switch (encap->encap_type) {
 263                 default:
 264                 case UDP_ENCAP_ESPINUDP:
 265                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 266                         /*
 267                          * 1) if the NAT-T peer's IP or port changed then
 268                          *    advertize the change to the keying daemon.
 269                          *    This is an inbound SA, so just compare
 270                          *    SRC ports.
 271                          */
 272                         if (decap_data->proto == AF_INET &&
 273                             (decap_data->saddr.a4 != x->props.saddr.a4 ||
 274                              decap_data->sport != encap->encap_sport)) {
 275                                 xfrm_address_t ipaddr;
 276
 277                                 ipaddr.a4 = decap_data->saddr.a4;
 278                                 km_new_mapping(x, &ipaddr, decap_data->sport);
 279
 280                                 /* XXX: perhaps add an extra
 281                                  * policy check here, to see
 282                                  * if we should allow or
 283                                  * reject a packet from a
 284                                  * different source
 285                                  * address/port.
 286                                  */
 287                         }
 288
 289                         /*
 290                          * 2) ignore UDP/TCP checksums in case
 291                          *    of NAT-T in Transport Mode, or
 292                          *    perform other post-processing fixes
 293                          *    as per * draft-ietf-ipsec-udp-encaps-06,
 294                          *    section 3.1.2
 295                          */
 296                         if (!x->props.mode)
 297                                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 298
 299                         break;
 300                 }
 301         }
 302         return 0;
 303 }
 304
 305 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 306 {
 307         struct esp_data *esp = x->data;
 308         u32 blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 309
 310         if (x->props.mode) {
 311                 mtu = ALIGN(mtu + 2, blksize);
 312         } else {
 313                 /* The worst case. */
 314                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 315         }
 316         if (esp->conf.padlen)
 317                 mtu = ALIGN(mtu, esp->conf.padlen);
 318
 319         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 320 }
 321
 322 static void esp4_err(struct sk_buff *skb, u32 info)
 323 {
 324         struct iphdr *iph = (struct iphdr*)skb->data;
 325         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 326         struct xfrm_state *x;
 327
 328         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 329             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 330                 return;
 331
 332         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 333         if (!x)
 334                 return;
 335         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 336                  ntohl(esph->spi), ntohl(iph->daddr));
 337         xfrm_state_put(x);
 338 }
 339
 340 static void esp_destroy(struct xfrm_state *x)
 341 {
 342         struct esp_data *esp = x->data;
 343
 344         if (!esp)
 345                 return;
 346
 347         crypto_free_tfm(esp->conf.tfm);
 348         esp->conf.tfm = NULL;
 349         kfree(esp->conf.ivec);
 350         esp->conf.ivec = NULL;
 351         crypto_free_tfm(esp->auth.tfm);
 352         esp->auth.tfm = NULL;
 353         kfree(esp->auth.work_icv);
 354         esp->auth.work_icv = NULL;
 355         kfree(esp);
 356 }
 357
 358 static int esp_init_state(struct xfrm_state *x)
 359 {
 360         struct esp_data *esp = NULL;
 361
 362         /* null auth and encryption can have zero length keys */
 363         if (x->aalg) {
 364                 if (x->aalg->alg_key_len > 512)
 365                         goto error;
 366         }
 367         if (x->ealg == NULL)
 368                 goto error;
 369
 370         esp = kmalloc(sizeof(*esp), GFP_KERNEL);
 371         if (esp == NULL)
 372                 return -ENOMEM;
 373
 374         memset(esp, 0, sizeof(*esp));
 375
 376         if (x->aalg) {
 377                 struct xfrm_algo_desc *aalg_desc;
 378
 379                 esp->auth.key = x->aalg->alg_key;
 380                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 381                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 382                 if (esp->auth.tfm == NULL)
 383                         goto error;
 384                 esp->auth.icv = esp_hmac_digest;
 385
 386                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 387                 BUG_ON(!aalg_desc);
 388
 389                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 390                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 391                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 392                                  x->aalg->alg_name,
 393                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 394                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 395                         goto error;
 396                 }
 397
 398                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 399                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 400
 401                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 402                 if (!esp->auth.work_icv)
 403                         goto error;
 404         }
 405         esp->conf.key = x->ealg->alg_key;
 406         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 407         if (x->props.ealgo == SADB_EALG_NULL)
 408                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 409         else
 410                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 411         if (esp->conf.tfm == NULL)
 412                 goto error;
 413         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 414         esp->conf.padlen = 0;
 415         if (esp->conf.ivlen) {
 416                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 417                 if (unlikely(esp->conf.ivec == NULL))
 418                         goto error;
 419                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 420         }
 421         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 422                 goto error;
 423         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 424         if (x->props.mode)
 425                 x->props.header_len += sizeof(struct iphdr);
 426         if (x->encap) {
 427                 struct xfrm_encap_tmpl *encap = x->encap;
 428
 429                 switch (encap->encap_type) {
 430                 default:
 431                         goto error;
 432                 case UDP_ENCAP_ESPINUDP:
 433                         x->props.header_len += sizeof(struct udphdr);
 434                         break;
 435                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 436                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 437                         break;
 438                 }
 439         }
 440         x->data = esp;
 441         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_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         .init_state     = esp_init_state,
 457         .destructor     = esp_destroy,
 458         .get_max_size   = esp4_get_max_size,
 459         .input          = esp_input,
 460         .post_input     = esp_post_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         struct xfrm_decap_state decap;
 473
 474         if (sizeof(struct esp_decap_data)  >
 475             sizeof(decap.decap_data)) {
 476                 extern void decap_data_too_small(void);
 477
 478                 decap_data_too_small();
 479         }
 480
 481         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 482                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 483                 return -EAGAIN;
 484         }
 485         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 486                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 487                 xfrm_unregister_type(&esp_type, AF_INET);
 488                 return -EAGAIN;
 489         }
 490         return 0;
 491 }
 492
 493 static void __exit esp4_fini(void)
 494 {
 495         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 496                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 497         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 498                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 499 }
 500
 501 module_init(esp4_init);
 502 module_exit(esp4_fini);
 503 MODULE_LICENSE("GPL");