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         int blksize;
  25         int clen;
  26         int alen;
  27         int nfrags;
  28
  29         /* Strip IP+ESP header. */
  30         __skb_pull(skb, skb_transport_offset(skb));
  31         /* Now 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         do {
  53                 int i;
  54                 for (i=0; i<clen-skb->len - 2; i++)
  55                         *(u8*)(trailer->tail + i) = i+1;
  56         } while (0);
  57         *(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
  58         pskb_put(skb, trailer, clen - skb->len);
  59
  60         __skb_push(skb, skb->data - skb_network_header(skb));
  61         top_iph = ip_hdr(skb);
  62         esph = (struct ip_esp_hdr *)(skb_network_header(skb) +
  63                                      top_iph->ihl * 4);
  64         top_iph->tot_len = htons(skb->len + alen);
  65         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  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 - top_iph->ihl*4);
  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                 top_iph->protocol = IPPROTO_UDP;
  92         } else
  93                 top_iph->protocol = IPPROTO_ESP;
  94
  95         esph->spi = x->id.spi;
  96         esph->seq_no = htonl(++x->replay.oseq);
  97         xfrm_aevent_doreplay(x);
  98
  99         if (esp->conf.ivlen) {
 100                 if (unlikely(!esp->conf.ivinitted)) {
 101                         get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 102                         esp->conf.ivinitted = 1;
 103                 }
 104                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 105         }
 106
 107         do {
 108                 struct scatterlist *sg = &esp->sgbuf[0];
 109
 110                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 111                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 112                         if (!sg)
 113                                 goto error;
 114                 }
 115                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 116                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
 117                 if (unlikely(sg != &esp->sgbuf[0]))
 118                         kfree(sg);
 119         } while (0);
 120
 121         if (unlikely(err))
 122                 goto error;
 123
 124         if (esp->conf.ivlen) {
 125                 memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
 126                 crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 127         }
 128
 129         if (esp->auth.icv_full_len) {
 130                 err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
 131                                      sizeof(*esph) + esp->conf.ivlen + clen);
 132                 memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
 133         }
 134
 135         ip_send_check(top_iph);
 136
 137 error:
 138         return err;
 139 }
 140
 141 /*
 142  * Note: detecting truncated vs. non-truncated authentication data is very
 143  * expensive, so we only support truncated data, which is the recommended
 144  * and common case.
 145  */
 146 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 147 {
 148         struct iphdr *iph;
 149         struct ip_esp_hdr *esph;
 150         struct esp_data *esp = x->data;
 151         struct crypto_blkcipher *tfm = esp->conf.tfm;
 152         struct blkcipher_desc desc = { .tfm = tfm };
 153         struct sk_buff *trailer;
 154         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 155         int alen = esp->auth.icv_trunc_len;
 156         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 157         int nfrags;
 158         int ihl;
 159         u8 nexthdr[2];
 160         struct scatterlist *sg;
 161         int padlen;
 162         int err;
 163
 164         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 165                 goto out;
 166
 167         if (elen <= 0 || (elen & (blksize-1)))
 168                 goto out;
 169
 170         /* If integrity check is required, do this. */
 171         if (esp->auth.icv_full_len) {
 172                 u8 sum[alen];
 173
 174                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 175                 if (err)
 176                         goto out;
 177
 178                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 179                         BUG();
 180
 181                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 182                         x->stats.integrity_failed++;
 183                         goto out;
 184                 }
 185         }
 186
 187         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 188                 goto out;
 189
 190         skb->ip_summed = CHECKSUM_NONE;
 191
 192         esph = (struct ip_esp_hdr*)skb->data;
 193
 194         /* Get ivec. This can be wrong, check against another impls. */
 195         if (esp->conf.ivlen)
 196                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 197
 198         sg = &esp->sgbuf[0];
 199
 200         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 201                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 202                 if (!sg)
 203                         goto out;
 204         }
 205         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 206         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 207         if (unlikely(sg != &esp->sgbuf[0]))
 208                 kfree(sg);
 209         if (unlikely(err))
 210                 return err;
 211
 212         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 213                 BUG();
 214
 215         padlen = nexthdr[0];
 216         if (padlen+2 >= elen)
 217                 goto out;
 218
 219         /* ... check padding bits here. Silly. :-) */
 220
 221         iph = ip_hdr(skb);
 222         ihl = iph->ihl * 4;
 223
 224         if (x->encap) {
 225                 struct xfrm_encap_tmpl *encap = x->encap;
 226                 struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
 227
 228                 /*
 229                  * 1) if the NAT-T peer's IP or port changed then
 230                  *    advertize the change to the keying daemon.
 231                  *    This is an inbound SA, so just compare
 232                  *    SRC ports.
 233                  */
 234                 if (iph->saddr != x->props.saddr.a4 ||
 235                     uh->source != encap->encap_sport) {
 236                         xfrm_address_t ipaddr;
 237
 238                         ipaddr.a4 = iph->saddr;
 239                         km_new_mapping(x, &ipaddr, uh->source);
 240
 241                         /* XXX: perhaps add an extra
 242                          * policy check here, to see
 243                          * if we should allow or
 244                          * reject a packet from a
 245                          * different source
 246                          * address/port.
 247                          */
 248                 }
 249
 250                 /*
 251                  * 2) ignore UDP/TCP checksums in case
 252                  *    of NAT-T in Transport Mode, or
 253                  *    perform other post-processing fixes
 254                  *    as per draft-ietf-ipsec-udp-encaps-06,
 255                  *    section 3.1.2
 256                  */
 257                 if (x->props.mode == XFRM_MODE_TRANSPORT ||
 258                     x->props.mode == XFRM_MODE_BEET)
 259                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 260         }
 261
 262         iph->protocol = nexthdr[1];
 263         pskb_trim(skb, skb->len - alen - padlen - 2);
 264         __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
 265         skb_set_transport_header(skb, -ihl);
 266
 267         return 0;
 268
 269 out:
 270         return -EINVAL;
 271 }
 272
 273 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 274 {
 275         struct esp_data *esp = x->data;
 276         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 277         int enclen = 0;
 278
 279         switch (x->props.mode) {
 280         case XFRM_MODE_TUNNEL:
 281                 mtu = ALIGN(mtu +2, blksize);
 282                 break;
 283         default:
 284         case XFRM_MODE_TRANSPORT:
 285                 /* The worst case */
 286                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 287                 break;
 288         case XFRM_MODE_BEET:
 289                 /* The worst case. */
 290                 enclen = IPV4_BEET_PHMAXLEN;
 291                 mtu = ALIGN(mtu + enclen + 2, blksize);
 292                 break;
 293         }
 294
 295         if (esp->conf.padlen)
 296                 mtu = ALIGN(mtu, esp->conf.padlen);
 297
 298         return mtu + x->props.header_len + esp->auth.icv_trunc_len - enclen;
 299 }
 300
 301 static void esp4_err(struct sk_buff *skb, u32 info)
 302 {
 303         struct iphdr *iph = (struct iphdr*)skb->data;
 304         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 305         struct xfrm_state *x;
 306
 307         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 308             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 309                 return;
 310
 311         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 312         if (!x)
 313                 return;
 314         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 315                  ntohl(esph->spi), ntohl(iph->daddr));
 316         xfrm_state_put(x);
 317 }
 318
 319 static void esp_destroy(struct xfrm_state *x)
 320 {
 321         struct esp_data *esp = x->data;
 322
 323         if (!esp)
 324                 return;
 325
 326         crypto_free_blkcipher(esp->conf.tfm);
 327         esp->conf.tfm = NULL;
 328         kfree(esp->conf.ivec);
 329         esp->conf.ivec = NULL;
 330         crypto_free_hash(esp->auth.tfm);
 331         esp->auth.tfm = NULL;
 332         kfree(esp->auth.work_icv);
 333         esp->auth.work_icv = NULL;
 334         kfree(esp);
 335 }
 336
 337 static int esp_init_state(struct xfrm_state *x)
 338 {
 339         struct esp_data *esp = NULL;
 340         struct crypto_blkcipher *tfm;
 341
 342         /* null auth and encryption can have zero length keys */
 343         if (x->aalg) {
 344                 if (x->aalg->alg_key_len > 512)
 345                         goto error;
 346         }
 347         if (x->ealg == NULL)
 348                 goto error;
 349
 350         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 351         if (esp == NULL)
 352                 return -ENOMEM;
 353
 354         if (x->aalg) {
 355                 struct xfrm_algo_desc *aalg_desc;
 356                 struct crypto_hash *hash;
 357
 358                 esp->auth.key = x->aalg->alg_key;
 359                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 360                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 361                                          CRYPTO_ALG_ASYNC);
 362                 if (IS_ERR(hash))
 363                         goto error;
 364
 365                 esp->auth.tfm = hash;
 366                 if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))
 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         esp->conf.key = x->ealg->alg_key;
 389         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 390         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 391         if (IS_ERR(tfm))
 392                 goto error;
 393         esp->conf.tfm = tfm;
 394         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 395         esp->conf.padlen = 0;
 396         if (esp->conf.ivlen) {
 397                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 398                 if (unlikely(esp->conf.ivec == NULL))
 399                         goto error;
 400                 esp->conf.ivinitted = 0;
 401         }
 402         if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))
 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         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         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 423         return 0;
 424
 425 error:
 426         x->data = esp;
 427         esp_destroy(x);
 428         x->data = NULL;
 429         return -EINVAL;
 430 }
 431
 432 static struct xfrm_type esp_type =
 433 {
 434         .description    = "ESP4",
 435         .owner          = THIS_MODULE,
 436         .proto          = IPPROTO_ESP,
 437         .init_state     = esp_init_state,
 438         .destructor     = esp_destroy,
 439         .get_max_size   = esp4_get_max_size,
 440         .input          = esp_input,
 441         .output         = esp_output
 442 };
 443
 444 static struct net_protocol esp4_protocol = {
 445         .handler        =       xfrm4_rcv,
 446         .err_handler    =       esp4_err,
 447         .no_policy      =       1,
 448 };
 449
 450 static int __init esp4_init(void)
 451 {
 452         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 453                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 454                 return -EAGAIN;
 455         }
 456         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 457                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 458                 xfrm_unregister_type(&esp_type, AF_INET);
 459                 return -EAGAIN;
 460         }
 461         return 0;
 462 }
 463
 464 static void __exit esp4_fini(void)
 465 {
 466         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 467                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 468         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 469                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 470 }
 471
 472 module_init(esp4_init);
 473 module_exit(esp4_fini);
 474 MODULE_LICENSE("GPL");