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->h.raw - skb->data);
  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->nh.raw);
  61         top_iph = skb->nh.iph;
  62         esph = (struct ip_esp_hdr *)(skb->nh.raw + top_iph->ihl*4);
  63         top_iph->tot_len = htons(skb->len + alen);
  64         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  65
  66         /* this is non-NULL only with UDP Encapsulation */
  67         if (x->encap) {
  68                 struct xfrm_encap_tmpl *encap = x->encap;
  69                 struct udphdr *uh;
  70                 u32 *udpdata32;
  71
  72                 uh = (struct udphdr *)esph;
  73                 uh->source = encap->encap_sport;
  74                 uh->dest = encap->encap_dport;
  75                 uh->len = htons(skb->len + alen - top_iph->ihl*4);
  76                 uh->check = 0;
  77
  78                 switch (encap->encap_type) {
  79                 default:
  80                 case UDP_ENCAP_ESPINUDP:
  81                         esph = (struct ip_esp_hdr *)(uh + 1);
  82                         break;
  83                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  84                         udpdata32 = (u32 *)(uh + 1);
  85                         udpdata32[0] = udpdata32[1] = 0;
  86                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  87                         break;
  88                 }
  89
  90                 top_iph->protocol = IPPROTO_UDP;
  91         } else
  92                 top_iph->protocol = IPPROTO_ESP;
  93
  94         esph->spi = x->id.spi;
  95         esph->seq_no = htonl(++x->replay.oseq);
  96         xfrm_aevent_doreplay(x);
  97
  98         if (esp->conf.ivlen)
  99                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 100
 101         do {
 102                 struct scatterlist *sg = &esp->sgbuf[0];
 103
 104                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 105                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 106                         if (!sg)
 107                                 goto error;
 108                 }
 109                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 110                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
 111                 if (unlikely(sg != &esp->sgbuf[0]))
 112                         kfree(sg);
 113         } while (0);
 114
 115         if (unlikely(err))
 116                 goto error;
 117
 118         if (esp->conf.ivlen) {
 119                 memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
 120                 crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 121         }
 122
 123         if (esp->auth.icv_full_len) {
 124                 err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
 125                                      sizeof(*esph) + esp->conf.ivlen + clen);
 126                 memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
 127         }
 128
 129         ip_send_check(top_iph);
 130
 131 error:
 132         return err;
 133 }
 134
 135 /*
 136  * Note: detecting truncated vs. non-truncated authentication data is very
 137  * expensive, so we only support truncated data, which is the recommended
 138  * and common case.
 139  */
 140 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 141 {
 142         struct iphdr *iph;
 143         struct ip_esp_hdr *esph;
 144         struct esp_data *esp = x->data;
 145         struct crypto_blkcipher *tfm = esp->conf.tfm;
 146         struct blkcipher_desc desc = { .tfm = tfm };
 147         struct sk_buff *trailer;
 148         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 149         int alen = esp->auth.icv_trunc_len;
 150         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 151         int nfrags;
 152         int ihl;
 153         u8 nexthdr[2];
 154         struct scatterlist *sg;
 155         int padlen;
 156         int err;
 157
 158         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 159                 goto out;
 160
 161         if (elen <= 0 || (elen & (blksize-1)))
 162                 goto out;
 163
 164         /* If integrity check is required, do this. */
 165         if (esp->auth.icv_full_len) {
 166                 u8 sum[alen];
 167
 168                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 169                 if (err)
 170                         goto out;
 171
 172                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 173                         BUG();
 174
 175                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 176                         x->stats.integrity_failed++;
 177                         goto out;
 178                 }
 179         }
 180
 181         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 182                 goto out;
 183
 184         skb->ip_summed = CHECKSUM_NONE;
 185
 186         esph = (struct ip_esp_hdr*)skb->data;
 187
 188         /* Get ivec. This can be wrong, check against another impls. */
 189         if (esp->conf.ivlen)
 190                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 191
 192         sg = &esp->sgbuf[0];
 193
 194         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 195                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 196                 if (!sg)
 197                         goto out;
 198         }
 199         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 200         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 201         if (unlikely(sg != &esp->sgbuf[0]))
 202                 kfree(sg);
 203         if (unlikely(err))
 204                 return err;
 205
 206         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 207                 BUG();
 208
 209         padlen = nexthdr[0];
 210         if (padlen+2 >= elen)
 211                 goto out;
 212
 213         /* ... check padding bits here. Silly. :-) */
 214
 215         iph = skb->nh.iph;
 216         ihl = iph->ihl * 4;
 217
 218         if (x->encap) {
 219                 struct xfrm_encap_tmpl *encap = x->encap;
 220                 struct udphdr *uh = (void *)(skb->nh.raw + ihl);
 221
 222                 /*
 223                  * 1) if the NAT-T peer's IP or port changed then
 224                  *    advertize the change to the keying daemon.
 225                  *    This is an inbound SA, so just compare
 226                  *    SRC ports.
 227                  */
 228                 if (iph->saddr != x->props.saddr.a4 ||
 229                     uh->source != encap->encap_sport) {
 230                         xfrm_address_t ipaddr;
 231
 232                         ipaddr.a4 = iph->saddr;
 233                         km_new_mapping(x, &ipaddr, uh->source);
 234
 235                         /* XXX: perhaps add an extra
 236                          * policy check here, to see
 237                          * if we should allow or
 238                          * reject a packet from a
 239                          * different source
 240                          * address/port.
 241                          */
 242                 }
 243
 244                 /*
 245                  * 2) ignore UDP/TCP checksums in case
 246                  *    of NAT-T in Transport Mode, or
 247                  *    perform other post-processing fixes
 248                  *    as per draft-ietf-ipsec-udp-encaps-06,
 249                  *    section 3.1.2
 250                  */
 251                 if (!x->props.mode)
 252                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 253         }
 254
 255         iph->protocol = nexthdr[1];
 256         pskb_trim(skb, skb->len - alen - padlen - 2);
 257         skb->h.raw = __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen) - ihl;
 258
 259         return 0;
 260
 261 out:
 262         return -EINVAL;
 263 }
 264
 265 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 266 {
 267         struct esp_data *esp = x->data;
 268         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 269
 270         if (x->props.mode) {
 271                 mtu = ALIGN(mtu + 2, blksize);
 272         } else {
 273                 /* The worst case. */
 274                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 275         }
 276         if (esp->conf.padlen)
 277                 mtu = ALIGN(mtu, esp->conf.padlen);
 278
 279         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 280 }
 281
 282 static void esp4_err(struct sk_buff *skb, u32 info)
 283 {
 284         struct iphdr *iph = (struct iphdr*)skb->data;
 285         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 286         struct xfrm_state *x;
 287
 288         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 289             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 290                 return;
 291
 292         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 293         if (!x)
 294                 return;
 295         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 296                  ntohl(esph->spi), ntohl(iph->daddr));
 297         xfrm_state_put(x);
 298 }
 299
 300 static void esp_destroy(struct xfrm_state *x)
 301 {
 302         struct esp_data *esp = x->data;
 303
 304         if (!esp)
 305                 return;
 306
 307         crypto_free_blkcipher(esp->conf.tfm);
 308         esp->conf.tfm = NULL;
 309         kfree(esp->conf.ivec);
 310         esp->conf.ivec = NULL;
 311         crypto_free_hash(esp->auth.tfm);
 312         esp->auth.tfm = NULL;
 313         kfree(esp->auth.work_icv);
 314         esp->auth.work_icv = NULL;
 315         kfree(esp);
 316 }
 317
 318 static int esp_init_state(struct xfrm_state *x)
 319 {
 320         struct esp_data *esp = NULL;
 321         struct crypto_blkcipher *tfm;
 322
 323         /* null auth and encryption can have zero length keys */
 324         if (x->aalg) {
 325                 if (x->aalg->alg_key_len > 512)
 326                         goto error;
 327         }
 328         if (x->ealg == NULL)
 329                 goto error;
 330
 331         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 332         if (esp == NULL)
 333                 return -ENOMEM;
 334
 335         if (x->aalg) {
 336                 struct xfrm_algo_desc *aalg_desc;
 337                 struct crypto_hash *hash;
 338
 339                 esp->auth.key = x->aalg->alg_key;
 340                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 341                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 342                                          CRYPTO_ALG_ASYNC);
 343                 if (IS_ERR(hash))
 344                         goto error;
 345
 346                 esp->auth.tfm = hash;
 347                 if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))
 348                         goto error;
 349
 350                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 351                 BUG_ON(!aalg_desc);
 352
 353                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 354                     crypto_hash_digestsize(hash)) {
 355                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 356                                  x->aalg->alg_name,
 357                                  crypto_hash_digestsize(hash),
 358                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 359                         goto error;
 360                 }
 361
 362                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 363                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 364
 365                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 366                 if (!esp->auth.work_icv)
 367                         goto error;
 368         }
 369         esp->conf.key = x->ealg->alg_key;
 370         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 371         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 372         if (IS_ERR(tfm))
 373                 goto error;
 374         esp->conf.tfm = tfm;
 375         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 376         esp->conf.padlen = 0;
 377         if (esp->conf.ivlen) {
 378                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 379                 if (unlikely(esp->conf.ivec == NULL))
 380                         goto error;
 381                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 382         }
 383         if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))
 384                 goto error;
 385         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 386         if (x->props.mode)
 387                 x->props.header_len += sizeof(struct iphdr);
 388         if (x->encap) {
 389                 struct xfrm_encap_tmpl *encap = x->encap;
 390
 391                 switch (encap->encap_type) {
 392                 default:
 393                         goto error;
 394                 case UDP_ENCAP_ESPINUDP:
 395                         x->props.header_len += sizeof(struct udphdr);
 396                         break;
 397                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 398                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 399                         break;
 400                 }
 401         }
 402         x->data = esp;
 403         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 404         return 0;
 405
 406 error:
 407         x->data = esp;
 408         esp_destroy(x);
 409         x->data = NULL;
 410         return -EINVAL;
 411 }
 412
 413 static struct xfrm_type esp_type =
 414 {
 415         .description    = "ESP4",
 416         .owner          = THIS_MODULE,
 417         .proto          = IPPROTO_ESP,
 418         .init_state     = esp_init_state,
 419         .destructor     = esp_destroy,
 420         .get_max_size   = esp4_get_max_size,
 421         .input          = esp_input,
 422         .output         = esp_output
 423 };
 424
 425 static struct net_protocol esp4_protocol = {
 426         .handler        =       xfrm4_rcv,
 427         .err_handler    =       esp4_err,
 428         .no_policy      =       1,
 429 };
 430
 431 static int __init esp4_init(void)
 432 {
 433         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 434                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 435                 return -EAGAIN;
 436         }
 437         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 438                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 439                 xfrm_unregister_type(&esp_type, AF_INET);
 440                 return -EAGAIN;
 441         }
 442         return 0;
 443 }
 444
 445 static void __exit esp4_fini(void)
 446 {
 447         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 448                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 449         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 450                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 451 }
 452
 453 module_init(esp4_init);
 454 module_exit(esp4_fini);
 455 MODULE_LICENSE("GPL");