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 = (struct ip_esp_hdr *)(skb_network_header(skb) +
  64                                      top_iph->ihl * 4);
  65         top_iph->tot_len = htons(skb->len + alen);
  66         *(skb_tail_pointer(trailer) - 1) = top_iph->protocol;
  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                 top_iph->protocol = IPPROTO_UDP;
  95         } else
  96                 top_iph->protocol = IPPROTO_ESP;
  97
  98         esph->spi = x->id.spi;
  99         esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
 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 unlock;
 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 unlock;
 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 unlock:
 138         spin_unlock_bh(&x->lock);
 139
 140         ip_send_check(top_iph);
 141
 142 error:
 143         return err;
 144 }
 145
 146 /*
 147  * Note: detecting truncated vs. non-truncated authentication data is very
 148  * expensive, so we only support truncated data, which is the recommended
 149  * and common case.
 150  */
 151 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 152 {
 153         struct iphdr *iph;
 154         struct ip_esp_hdr *esph;
 155         struct esp_data *esp = x->data;
 156         struct crypto_blkcipher *tfm = esp->conf.tfm;
 157         struct blkcipher_desc desc = { .tfm = tfm };
 158         struct sk_buff *trailer;
 159         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 160         int alen = esp->auth.icv_trunc_len;
 161         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 162         int nfrags;
 163         int ihl;
 164         u8 nexthdr[2];
 165         struct scatterlist *sg;
 166         int padlen;
 167         int err;
 168
 169         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 170                 goto out;
 171
 172         if (elen <= 0 || (elen & (blksize-1)))
 173                 goto out;
 174
 175         /* If integrity check is required, do this. */
 176         if (esp->auth.icv_full_len) {
 177                 u8 sum[alen];
 178
 179                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 180                 if (err)
 181                         goto out;
 182
 183                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 184                         BUG();
 185
 186                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 187                         x->stats.integrity_failed++;
 188                         goto out;
 189                 }
 190         }
 191
 192         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 193                 goto out;
 194
 195         skb->ip_summed = CHECKSUM_NONE;
 196
 197         esph = (struct ip_esp_hdr*)skb->data;
 198
 199         /* Get ivec. This can be wrong, check against another impls. */
 200         if (esp->conf.ivlen)
 201                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 202
 203         sg = &esp->sgbuf[0];
 204
 205         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 206                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 207                 if (!sg)
 208                         goto out;
 209         }
 210         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 211         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 212         if (unlikely(sg != &esp->sgbuf[0]))
 213                 kfree(sg);
 214         if (unlikely(err))
 215                 return err;
 216
 217         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 218                 BUG();
 219
 220         padlen = nexthdr[0];
 221         if (padlen+2 >= elen)
 222                 goto out;
 223
 224         /* ... check padding bits here. Silly. :-) */
 225
 226         iph = ip_hdr(skb);
 227         ihl = iph->ihl * 4;
 228
 229         if (x->encap) {
 230                 struct xfrm_encap_tmpl *encap = x->encap;
 231                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 232
 233                 /*
 234                  * 1) if the NAT-T peer's IP or port changed then
 235                  *    advertize the change to the keying daemon.
 236                  *    This is an inbound SA, so just compare
 237                  *    SRC ports.
 238                  */
 239                 if (iph->saddr != x->props.saddr.a4 ||
 240                     uh->source != encap->encap_sport) {
 241                         xfrm_address_t ipaddr;
 242
 243                         ipaddr.a4 = iph->saddr;
 244                         km_new_mapping(x, &ipaddr, uh->source);
 245
 246                         /* XXX: perhaps add an extra
 247                          * policy check here, to see
 248                          * if we should allow or
 249                          * reject a packet from a
 250                          * different source
 251                          * address/port.
 252                          */
 253                 }
 254
 255                 /*
 256                  * 2) ignore UDP/TCP checksums in case
 257                  *    of NAT-T in Transport Mode, or
 258                  *    perform other post-processing fixes
 259                  *    as per draft-ietf-ipsec-udp-encaps-06,
 260                  *    section 3.1.2
 261                  */
 262                 if (x->props.mode == XFRM_MODE_TRANSPORT)
 263                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 264         }
 265
 266         iph->protocol = nexthdr[1];
 267         pskb_trim(skb, skb->len - alen - padlen - 2);
 268         __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
 269         skb_set_transport_header(skb, -ihl);
 270
 271         return 0;
 272
 273 out:
 274         return -EINVAL;
 275 }
 276
 277 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
 278 {
 279         struct esp_data *esp = x->data;
 280         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 281         u32 align = max_t(u32, blksize, esp->conf.padlen);
 282         u32 rem;
 283
 284         mtu -= x->props.header_len + esp->auth.icv_trunc_len;
 285         rem = mtu & (align - 1);
 286         mtu &= ~(align - 1);
 287
 288         switch (x->props.mode) {
 289         case XFRM_MODE_TUNNEL:
 290                 break;
 291         default:
 292         case XFRM_MODE_TRANSPORT:
 293                 /* The worst case */
 294                 mtu -= blksize - 4;
 295                 mtu += min_t(u32, blksize - 4, rem);
 296                 break;
 297         case XFRM_MODE_BEET:
 298                 /* The worst case. */
 299                 mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
 300                 break;
 301         }
 302
 303         return mtu - 2;
 304 }
 305
 306 static void esp4_err(struct sk_buff *skb, u32 info)
 307 {
 308         struct iphdr *iph = (struct iphdr*)skb->data;
 309         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 310         struct xfrm_state *x;
 311
 312         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 313             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 314                 return;
 315
 316         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 317         if (!x)
 318                 return;
 319         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 320                  ntohl(esph->spi), ntohl(iph->daddr));
 321         xfrm_state_put(x);
 322 }
 323
 324 static void esp_destroy(struct xfrm_state *x)
 325 {
 326         struct esp_data *esp = x->data;
 327
 328         if (!esp)
 329                 return;
 330
 331         crypto_free_blkcipher(esp->conf.tfm);
 332         esp->conf.tfm = NULL;
 333         kfree(esp->conf.ivec);
 334         esp->conf.ivec = NULL;
 335         crypto_free_hash(esp->auth.tfm);
 336         esp->auth.tfm = NULL;
 337         kfree(esp->auth.work_icv);
 338         esp->auth.work_icv = NULL;
 339         kfree(esp);
 340 }
 341
 342 static int esp_init_state(struct xfrm_state *x)
 343 {
 344         struct esp_data *esp = NULL;
 345         struct crypto_blkcipher *tfm;
 346         u32 align;
 347
 348         if (x->ealg == NULL)
 349                 goto error;
 350
 351         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 352         if (esp == NULL)
 353                 return -ENOMEM;
 354
 355         if (x->aalg) {
 356                 struct xfrm_algo_desc *aalg_desc;
 357                 struct crypto_hash *hash;
 358
 359                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 360                                          CRYPTO_ALG_ASYNC);
 361                 if (IS_ERR(hash))
 362                         goto error;
 363
 364                 esp->auth.tfm = hash;
 365                 if (crypto_hash_setkey(hash, x->aalg->alg_key,
 366                                        (x->aalg->alg_key_len + 7) / 8))
 367                         goto error;
 368
 369                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 370                 BUG_ON(!aalg_desc);
 371
 372                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 373                     crypto_hash_digestsize(hash)) {
 374                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 375                                  x->aalg->alg_name,
 376                                  crypto_hash_digestsize(hash),
 377                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 378                         goto error;
 379                 }
 380
 381                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 382                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 383
 384                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 385                 if (!esp->auth.work_icv)
 386                         goto error;
 387         }
 388
 389         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 390         if (IS_ERR(tfm))
 391                 goto error;
 392         esp->conf.tfm = tfm;
 393         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 394         esp->conf.padlen = 0;
 395         if (esp->conf.ivlen) {
 396                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 397                 if (unlikely(esp->conf.ivec == NULL))
 398                         goto error;
 399                 esp->conf.ivinitted = 0;
 400         }
 401         if (crypto_blkcipher_setkey(tfm, x->ealg->alg_key,
 402                                     (x->ealg->alg_key_len + 7) / 8))
 403                 goto error;
 404         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 405         if (x->props.mode == XFRM_MODE_TUNNEL)
 406                 x->props.header_len += sizeof(struct iphdr);
 407         else if (x->props.mode == XFRM_MODE_BEET)
 408                 x->props.header_len += IPV4_BEET_PHMAXLEN;
 409         if (x->encap) {
 410                 struct xfrm_encap_tmpl *encap = x->encap;
 411
 412                 switch (encap->encap_type) {
 413                 default:
 414                         goto error;
 415                 case UDP_ENCAP_ESPINUDP:
 416                         x->props.header_len += sizeof(struct udphdr);
 417                         break;
 418                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 419                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 420                         break;
 421                 }
 422         }
 423         x->data = esp;
 424         align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 425         if (esp->conf.padlen)
 426                 align = max_t(u32, align, esp->conf.padlen);
 427         x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
 428         return 0;
 429
 430 error:
 431         x->data = esp;
 432         esp_destroy(x);
 433         x->data = NULL;
 434         return -EINVAL;
 435 }
 436
 437 static struct xfrm_type esp_type =
 438 {
 439         .description    = "ESP4",
 440         .owner          = THIS_MODULE,
 441         .proto          = IPPROTO_ESP,
 442         .flags          = XFRM_TYPE_REPLAY_PROT,
 443         .init_state     = esp_init_state,
 444         .destructor     = esp_destroy,
 445         .get_mtu        = esp4_get_mtu,
 446         .input          = esp_input,
 447         .output         = esp_output
 448 };
 449
 450 static struct net_protocol esp4_protocol = {
 451         .handler        =       xfrm4_rcv,
 452         .err_handler    =       esp4_err,
 453         .no_policy      =       1,
 454 };
 455
 456 static int __init esp4_init(void)
 457 {
 458         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 459                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 460                 return -EAGAIN;
 461         }
 462         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 463                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 464                 xfrm_unregister_type(&esp_type, AF_INET);
 465                 return -EAGAIN;
 466         }
 467         return 0;
 468 }
 469
 470 static void __exit esp4_fini(void)
 471 {
 472         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 473                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 474         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 475                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 476 }
 477
 478 module_init(esp4_init);
 479 module_exit(esp4_fini);
 480 MODULE_LICENSE("GPL");
 481 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);