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 <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 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         /* skb is pure payload to encrypt */
  31
  32         err = -ENOMEM;
  33
  34         /* Round to block size */
  35         clen = skb->len;
  36
  37         esp = x->data;
  38         alen = esp->auth.icv_trunc_len;
  39         tfm = esp->conf.tfm;
  40         desc.tfm = tfm;
  41         desc.flags = 0;
  42         blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
  43         clen = ALIGN(clen + 2, blksize);
  44         if (esp->conf.padlen)
  45                 clen = ALIGN(clen, esp->conf.padlen);
  46
  47         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  48                 goto error;
  49
  50         /* Fill padding... */
  51         tail = skb_tail_pointer(trailer);
  52         do {
  53                 int i;
  54                 for (i=0; i<clen-skb->len - 2; i++)
  55                         tail[i] = i + 1;
  56         } while (0);
  57         tail[clen - skb->len - 2] = (clen - skb->len) - 2;
  58         pskb_put(skb, trailer, clen - skb->len);
  59
  60         skb_push(skb, -skb_network_offset(skb));
  61         esph = ip_esp_hdr(skb);
  62         *(skb_tail_pointer(trailer) - 1) = *skb_mac_header(skb);
  63         *skb_mac_header(skb) = IPPROTO_ESP;
  64
  65         spin_lock_bh(&x->lock);
  66
  67         /* this is non-NULL only with UDP Encapsulation */
  68         if (x->encap) {
  69                 struct xfrm_encap_tmpl *encap = x->encap;
  70                 struct udphdr *uh;
  71                 __be32 *udpdata32;
  72
  73                 uh = (struct udphdr *)esph;
  74                 uh->source = encap->encap_sport;
  75                 uh->dest = encap->encap_dport;
  76                 uh->len = htons(skb->len + alen - skb_transport_offset(skb));
  77                 uh->check = 0;
  78
  79                 switch (encap->encap_type) {
  80                 default:
  81                 case UDP_ENCAP_ESPINUDP:
  82                         esph = (struct ip_esp_hdr *)(uh + 1);
  83                         break;
  84                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  85                         udpdata32 = (__be32 *)(uh + 1);
  86                         udpdata32[0] = udpdata32[1] = 0;
  87                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  88                         break;
  89                 }
  90
  91                 *skb_mac_header(skb) = IPPROTO_UDP;
  92         }
  93
  94         esph->spi = x->id.spi;
  95         esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
  96
  97         if (esp->conf.ivlen) {
  98                 if (unlikely(!esp->conf.ivinitted)) {
  99                         get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 100                         esp->conf.ivinitted = 1;
 101                 }
 102                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 103         }
 104
 105         do {
 106                 struct scatterlist *sg = &esp->sgbuf[0];
 107
 108                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 109                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 110                         if (!sg)
 111                                 goto unlock;
 112                 }
 113                 sg_init_table(sg, nfrags);
 114                 sg_mark_end(sg, skb_to_sgvec(skb, sg, esph->enc_data +
 115                                                       esp->conf.ivlen -
 116                                                       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 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(*esph) - 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(*esph)))
 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         sg_init_table(sg, nfrags);
 208         sg_mark_end(sg, skb_to_sgvec(skb, sg, sizeof(*esph) + esp->conf.ivlen,
 209                                      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         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 nexthdr[1];
 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         if (x->ealg == NULL)
 347                 goto error;
 348
 349         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 350         if (esp == NULL)
 351                 return -ENOMEM;
 352
 353         if (x->aalg) {
 354                 struct xfrm_algo_desc *aalg_desc;
 355                 struct crypto_hash *hash;
 356
 357                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 358                                          CRYPTO_ALG_ASYNC);
 359                 if (IS_ERR(hash))
 360                         goto error;
 361
 362                 esp->auth.tfm = hash;
 363                 if (crypto_hash_setkey(hash, x->aalg->alg_key,
 364                                        (x->aalg->alg_key_len + 7) / 8))
 365                         goto error;
 366
 367                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 368                 BUG_ON(!aalg_desc);
 369
 370                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 371                     crypto_hash_digestsize(hash)) {
 372                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 373                                  x->aalg->alg_name,
 374                                  crypto_hash_digestsize(hash),
 375                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 376                         goto error;
 377                 }
 378
 379                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 380                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 381
 382                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 383                 if (!esp->auth.work_icv)
 384                         goto error;
 385         }
 386
 387         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 388         if (IS_ERR(tfm))
 389                 goto error;
 390         esp->conf.tfm = tfm;
 391         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 392         esp->conf.padlen = 0;
 393         if (esp->conf.ivlen) {
 394                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 395                 if (unlikely(esp->conf.ivec == NULL))
 396                         goto error;
 397                 esp->conf.ivinitted = 0;
 398         }
 399         if (crypto_blkcipher_setkey(tfm, x->ealg->alg_key,
 400                                     (x->ealg->alg_key_len + 7) / 8))
 401                 goto error;
 402         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 403         if (x->props.mode == XFRM_MODE_TUNNEL)
 404                 x->props.header_len += sizeof(struct iphdr);
 405         else if (x->props.mode == XFRM_MODE_BEET)
 406                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 407         if (x->encap) {
 408                 struct xfrm_encap_tmpl *encap = x->encap;
 409
 410                 switch (encap->encap_type) {
 411                 default:
 412                         goto error;
 413                 case UDP_ENCAP_ESPINUDP:
 414                         x->props.header_len += sizeof(struct udphdr);
 415                         break;
 416                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 417                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 418                         break;
 419                 }
 420         }
 421         x->data = esp;
 422         align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 423         if (esp->conf.padlen)
 424                 align = max_t(u32, align, esp->conf.padlen);
 425         x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
 426         return 0;
 427
 428 error:
 429         x->data = esp;
 430         esp_destroy(x);
 431         x->data = NULL;
 432         return -EINVAL;
 433 }
 434
 435 static struct xfrm_type esp_type =
 436 {
 437         .description    = "ESP4",
 438         .owner          = THIS_MODULE,
 439         .proto          = IPPROTO_ESP,
 440         .flags          = XFRM_TYPE_REPLAY_PROT,
 441         .init_state     = esp_init_state,
 442         .destructor     = esp_destroy,
 443         .get_mtu        = esp4_get_mtu,
 444         .input          = esp_input,
 445         .output         = esp_output
 446 };
 447
 448 static struct net_protocol esp4_protocol = {
 449         .handler        =       xfrm4_rcv,
 450         .err_handler    =       esp4_err,
 451         .no_policy      =       1,
 452 };
 453
 454 static int __init esp4_init(void)
 455 {
 456         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 457                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 458                 return -EAGAIN;
 459         }
 460         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 461                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 462                 xfrm_unregister_type(&esp_type, AF_INET);
 463                 return -EAGAIN;
 464         }
 465         return 0;
 466 }
 467
 468 static void __exit esp4_fini(void)
 469 {
 470         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 471                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 472         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 473                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 474 }
 475
 476 module_init(esp4_init);
 477 module_exit(esp4_fini);
 478 MODULE_LICENSE("GPL");
 479 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);