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 <net/icmp.h>
  12 #include <net/protocol.h>
  13 #include <net/udp.h>
  14
  15 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  16 {
  17         int err;
  18         struct iphdr *top_iph;
  19         struct ip_esp_hdr *esph;
  20         struct crypto_blkcipher *tfm;
  21         struct blkcipher_desc desc;
  22         struct esp_data *esp;
  23         struct sk_buff *trailer;
  24         u8 *tail;
  25         int blksize;
  26         int clen;
  27         int alen;
  28         int nfrags;
  29
  30         /* Strip IP+ESP header. */
  31         __skb_pull(skb, skb_transport_offset(skb));
  32         /* Now skb is pure payload to encrypt */
  33
  34         err = -ENOMEM;
  35
  36         /* Round to block size */
  37         clen = skb->len;
  38
  39         esp = x->data;
  40         alen = esp->auth.icv_trunc_len;
  41         tfm = esp->conf.tfm;
  42         desc.tfm = tfm;
  43         desc.flags = 0;
  44         blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
  45         clen = ALIGN(clen + 2, blksize);
  46         if (esp->conf.padlen)
  47                 clen = ALIGN(clen, esp->conf.padlen);
  48
  49         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  50                 goto error;
  51
  52         /* Fill padding... */
  53         tail = skb_tail_pointer(trailer);
  54         do {
  55                 int i;
  56                 for (i=0; i<clen-skb->len - 2; i++)
  57                         tail[i] = i + 1;
  58         } while (0);
  59         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_network_header(skb));
  63         top_iph = ip_hdr(skb);
  64         esph = (struct ip_esp_hdr *)(skb_network_header(skb) +
  65                                      top_iph->ihl * 4);
  66         top_iph->tot_len = htons(skb->len + alen);
  67         *(skb_tail_pointer(trailer) - 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                 __be32 *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 = (__be32 *)(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         xfrm_aevent_doreplay(x);
 100
 101         if (esp->conf.ivlen) {
 102                 if (unlikely(!esp->conf.ivinitted)) {
 103                         get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 104                         esp->conf.ivinitted = 1;
 105                 }
 106                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 107         }
 108
 109         do {
 110                 struct scatterlist *sg = &esp->sgbuf[0];
 111
 112                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 113                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 114                         if (!sg)
 115                                 goto error;
 116                 }
 117                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 118                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
 119                 if (unlikely(sg != &esp->sgbuf[0]))
 120                         kfree(sg);
 121         } while (0);
 122
 123         if (unlikely(err))
 124                 goto error;
 125
 126         if (esp->conf.ivlen) {
 127                 memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
 128                 crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 129         }
 130
 131         if (esp->auth.icv_full_len) {
 132                 err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
 133                                      sizeof(*esph) + esp->conf.ivlen + clen);
 134                 memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
 135         }
 136
 137         ip_send_check(top_iph);
 138
 139 error:
 140         return err;
 141 }
 142
 143 /*
 144  * Note: detecting truncated vs. non-truncated authentication data is very
 145  * expensive, so we only support truncated data, which is the recommended
 146  * and common case.
 147  */
 148 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 149 {
 150         struct iphdr *iph;
 151         struct ip_esp_hdr *esph;
 152         struct esp_data *esp = x->data;
 153         struct crypto_blkcipher *tfm = esp->conf.tfm;
 154         struct blkcipher_desc desc = { .tfm = tfm };
 155         struct sk_buff *trailer;
 156         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 157         int alen = esp->auth.icv_trunc_len;
 158         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 159         int nfrags;
 160         int ihl;
 161         u8 nexthdr[2];
 162         struct scatterlist *sg;
 163         int padlen;
 164         int err;
 165
 166         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 167                 goto out;
 168
 169         if (elen <= 0 || (elen & (blksize-1)))
 170                 goto out;
 171
 172         /* If integrity check is required, do this. */
 173         if (esp->auth.icv_full_len) {
 174                 u8 sum[alen];
 175
 176                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 177                 if (err)
 178                         goto out;
 179
 180                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 181                         BUG();
 182
 183                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 184                         x->stats.integrity_failed++;
 185                         goto out;
 186                 }
 187         }
 188
 189         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 190                 goto out;
 191
 192         skb->ip_summed = CHECKSUM_NONE;
 193
 194         esph = (struct ip_esp_hdr*)skb->data;
 195
 196         /* Get ivec. This can be wrong, check against another impls. */
 197         if (esp->conf.ivlen)
 198                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 199
 200         sg = &esp->sgbuf[0];
 201
 202         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 203                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 204                 if (!sg)
 205                         goto out;
 206         }
 207         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 208         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 209         if (unlikely(sg != &esp->sgbuf[0]))
 210                 kfree(sg);
 211         if (unlikely(err))
 212                 return err;
 213
 214         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 215                 BUG();
 216
 217         padlen = nexthdr[0];
 218         if (padlen+2 >= elen)
 219                 goto out;
 220
 221         /* ... check padding bits here. Silly. :-) */
 222
 223         iph = ip_hdr(skb);
 224         ihl = iph->ihl * 4;
 225
 226         if (x->encap) {
 227                 struct xfrm_encap_tmpl *encap = x->encap;
 228                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 229
 230                 /*
 231                  * 1) if the NAT-T peer's IP or port changed then
 232                  *    advertize the change to the keying daemon.
 233                  *    This is an inbound SA, so just compare
 234                  *    SRC ports.
 235                  */
 236                 if (iph->saddr != x->props.saddr.a4 ||
 237                     uh->source != encap->encap_sport) {
 238                         xfrm_address_t ipaddr;
 239
 240                         ipaddr.a4 = iph->saddr;
 241                         km_new_mapping(x, &ipaddr, uh->source);
 242
 243                         /* XXX: perhaps add an extra
 244                          * policy check here, to see
 245                          * if we should allow or
 246                          * reject a packet from a
 247                          * different source
 248                          * address/port.
 249                          */
 250                 }
 251
 252                 /*
 253                  * 2) ignore UDP/TCP checksums in case
 254                  *    of NAT-T in Transport Mode, or
 255                  *    perform other post-processing fixes
 256                  *    as per draft-ietf-ipsec-udp-encaps-06,
 257                  *    section 3.1.2
 258                  */
 259                 if (x->props.mode == XFRM_MODE_TRANSPORT ||
 260                     x->props.mode == XFRM_MODE_BEET)
 261                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 262         }
 263
 264         iph->protocol = nexthdr[1];
 265         pskb_trim(skb, skb->len - alen - padlen - 2);
 266         __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
 267         skb_set_transport_header(skb, -ihl);
 268
 269         return 0;
 270
 271 out:
 272         return -EINVAL;
 273 }
 274
 275 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 276 {
 277         struct esp_data *esp = x->data;
 278         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 279         u32 align = max_t(u32, blksize, esp->conf.padlen);
 280         u32 rem;
 281
 282         mtu -= x->props.header_len + esp->auth.icv_trunc_len;
 283         rem = mtu & (align - 1);
 284         mtu &= ~(align - 1);
 285
 286         switch (x->props.mode) {
 287         case XFRM_MODE_TUNNEL:
 288                 break;
 289         default:
 290         case XFRM_MODE_TRANSPORT:
 291                 /* The worst case */
 292                 mtu -= blksize - 4;
 293                 mtu += min_t(u32, blksize - 4, rem);
 294                 break;
 295         case XFRM_MODE_BEET:
 296                 /* The worst case. */
 297                 mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
 298                 break;
 299         }
 300
 301         return mtu - 2;
 302 }
 303
 304 static void esp4_err(struct sk_buff *skb, u32 info)
 305 {
 306         struct iphdr *iph = (struct iphdr*)skb->data;
 307         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 308         struct xfrm_state *x;
 309
 310         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 311             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 312                 return;
 313
 314         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 315         if (!x)
 316                 return;
 317         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 318                  ntohl(esph->spi), ntohl(iph->daddr));
 319         xfrm_state_put(x);
 320 }
 321
 322 static void esp_destroy(struct xfrm_state *x)
 323 {
 324         struct esp_data *esp = x->data;
 325
 326         if (!esp)
 327                 return;
 328
 329         crypto_free_blkcipher(esp->conf.tfm);
 330         esp->conf.tfm = NULL;
 331         kfree(esp->conf.ivec);
 332         esp->conf.ivec = NULL;
 333         crypto_free_hash(esp->auth.tfm);
 334         esp->auth.tfm = NULL;
 335         kfree(esp->auth.work_icv);
 336         esp->auth.work_icv = NULL;
 337         kfree(esp);
 338 }
 339
 340 static int esp_init_state(struct xfrm_state *x)
 341 {
 342         struct esp_data *esp = NULL;
 343         struct crypto_blkcipher *tfm;
 344         u32 align;
 345
 346         /* null auth and encryption can have zero length keys */
 347         if (x->aalg) {
 348                 if (x->aalg->alg_key_len > 512)
 349                         goto error;
 350         }
 351         if (x->ealg == NULL)
 352                 goto error;
 353
 354         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 355         if (esp == NULL)
 356                 return -ENOMEM;
 357
 358         if (x->aalg) {
 359                 struct xfrm_algo_desc *aalg_desc;
 360                 struct crypto_hash *hash;
 361
 362                 esp->auth.key = x->aalg->alg_key;
 363                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 364                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 365                                          CRYPTO_ALG_ASYNC);
 366                 if (IS_ERR(hash))
 367                         goto error;
 368
 369                 esp->auth.tfm = hash;
 370                 if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))
 371                         goto error;
 372
 373                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 374                 BUG_ON(!aalg_desc);
 375
 376                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 377                     crypto_hash_digestsize(hash)) {
 378                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 379                                  x->aalg->alg_name,
 380                                  crypto_hash_digestsize(hash),
 381                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 382                         goto error;
 383                 }
 384
 385                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 386                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 387
 388                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 389                 if (!esp->auth.work_icv)
 390                         goto error;
 391         }
 392         esp->conf.key = x->ealg->alg_key;
 393         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 394         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 395         if (IS_ERR(tfm))
 396                 goto error;
 397         esp->conf.tfm = tfm;
 398         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 399         esp->conf.padlen = 0;
 400         if (esp->conf.ivlen) {
 401                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 402                 if (unlikely(esp->conf.ivec == NULL))
 403                         goto error;
 404                 esp->conf.ivinitted = 0;
 405         }
 406         if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))
 407                 goto error;
 408         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 409         if (x->props.mode == XFRM_MODE_TUNNEL)
 410                 x->props.header_len += sizeof(struct iphdr);
 411         else if (x->props.mode == XFRM_MODE_BEET)
 412                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 413         if (x->encap) {
 414                 struct xfrm_encap_tmpl *encap = x->encap;
 415
 416                 switch (encap->encap_type) {
 417                 default:
 418                         goto error;
 419                 case UDP_ENCAP_ESPINUDP:
 420                         x->props.header_len += sizeof(struct udphdr);
 421                         break;
 422                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 423                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 424                         break;
 425                 }
 426         }
 427         x->data = esp;
 428         align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 429         if (esp->conf.padlen)
 430                 align = max_t(u32, align, esp->conf.padlen);
 431         x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
 432         return 0;
 433
 434 error:
 435         x->data = esp;
 436         esp_destroy(x);
 437         x->data = NULL;
 438         return -EINVAL;
 439 }
 440
 441 static struct xfrm_type esp_type =
 442 {
 443         .description    = "ESP4",
 444         .owner          = THIS_MODULE,
 445         .proto          = IPPROTO_ESP,
 446         .init_state     = esp_init_state,
 447         .destructor     = esp_destroy,
 448         .get_mtu        = esp4_get_mtu,
 449         .input          = esp_input,
 450         .output         = esp_output
 451 };
 452
 453 static struct net_protocol esp4_protocol = {
 454         .handler        =       xfrm4_rcv,
 455         .err_handler    =       esp4_err,
 456         .no_policy      =       1,
 457 };
 458
 459 static int __init esp4_init(void)
 460 {
 461         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 462                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 463                 return -EAGAIN;
 464         }
 465         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 466                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 467                 xfrm_unregister_type(&esp_type, AF_INET);
 468                 return -EAGAIN;
 469         }
 470         return 0;
 471 }
 472
 473 static void __exit esp4_fini(void)
 474 {
 475         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 476                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 477         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 478                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 479 }
 480
 481 module_init(esp4_init);
 482 module_exit(esp4_fini);
 483 MODULE_LICENSE("GPL");
 484 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);