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                 if (unlikely(!esp->conf.ivinitted)) {
 100                         get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 101                         esp->conf.ivinitted = 1;
 102                 }
 103                 crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 104         }
 105
 106         do {
 107                 struct scatterlist *sg = &esp->sgbuf[0];
 108
 109                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 110                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 111                         if (!sg)
 112                                 goto error;
 113                 }
 114                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 115                 err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
 116                 if (unlikely(sg != &esp->sgbuf[0]))
 117                         kfree(sg);
 118         } while (0);
 119
 120         if (unlikely(err))
 121                 goto error;
 122
 123         if (esp->conf.ivlen) {
 124                 memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
 125                 crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
 126         }
 127
 128         if (esp->auth.icv_full_len) {
 129                 err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
 130                                      sizeof(*esph) + esp->conf.ivlen + clen);
 131                 memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
 132         }
 133
 134         ip_send_check(top_iph);
 135
 136 error:
 137         return err;
 138 }
 139
 140 /*
 141  * Note: detecting truncated vs. non-truncated authentication data is very
 142  * expensive, so we only support truncated data, which is the recommended
 143  * and common case.
 144  */
 145 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 146 {
 147         struct iphdr *iph;
 148         struct ip_esp_hdr *esph;
 149         struct esp_data *esp = x->data;
 150         struct crypto_blkcipher *tfm = esp->conf.tfm;
 151         struct blkcipher_desc desc = { .tfm = tfm };
 152         struct sk_buff *trailer;
 153         int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
 154         int alen = esp->auth.icv_trunc_len;
 155         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 156         int nfrags;
 157         int ihl;
 158         u8 nexthdr[2];
 159         struct scatterlist *sg;
 160         int padlen;
 161         int err;
 162
 163         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 164                 goto out;
 165
 166         if (elen <= 0 || (elen & (blksize-1)))
 167                 goto out;
 168
 169         /* If integrity check is required, do this. */
 170         if (esp->auth.icv_full_len) {
 171                 u8 sum[alen];
 172
 173                 err = esp_mac_digest(esp, skb, 0, skb->len - alen);
 174                 if (err)
 175                         goto out;
 176
 177                 if (skb_copy_bits(skb, skb->len - alen, sum, alen))
 178                         BUG();
 179
 180                 if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
 181                         x->stats.integrity_failed++;
 182                         goto out;
 183                 }
 184         }
 185
 186         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 187                 goto out;
 188
 189         skb->ip_summed = CHECKSUM_NONE;
 190
 191         esph = (struct ip_esp_hdr*)skb->data;
 192
 193         /* Get ivec. This can be wrong, check against another impls. */
 194         if (esp->conf.ivlen)
 195                 crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
 196
 197         sg = &esp->sgbuf[0];
 198
 199         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 200                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 201                 if (!sg)
 202                         goto out;
 203         }
 204         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 205         err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
 206         if (unlikely(sg != &esp->sgbuf[0]))
 207                 kfree(sg);
 208         if (unlikely(err))
 209                 return err;
 210
 211         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 212                 BUG();
 213
 214         padlen = nexthdr[0];
 215         if (padlen+2 >= elen)
 216                 goto out;
 217
 218         /* ... check padding bits here. Silly. :-) */
 219
 220         iph = skb->nh.iph;
 221         ihl = iph->ihl * 4;
 222
 223         if (x->encap) {
 224                 struct xfrm_encap_tmpl *encap = x->encap;
 225                 struct udphdr *uh = (void *)(skb->nh.raw + ihl);
 226
 227                 /*
 228                  * 1) if the NAT-T peer's IP or port changed then
 229                  *    advertize the change to the keying daemon.
 230                  *    This is an inbound SA, so just compare
 231                  *    SRC ports.
 232                  */
 233                 if (iph->saddr != x->props.saddr.a4 ||
 234                     uh->source != encap->encap_sport) {
 235                         xfrm_address_t ipaddr;
 236
 237                         ipaddr.a4 = iph->saddr;
 238                         km_new_mapping(x, &ipaddr, uh->source);
 239
 240                         /* XXX: perhaps add an extra
 241                          * policy check here, to see
 242                          * if we should allow or
 243                          * reject a packet from a
 244                          * different source
 245                          * address/port.
 246                          */
 247                 }
 248
 249                 /*
 250                  * 2) ignore UDP/TCP checksums in case
 251                  *    of NAT-T in Transport Mode, or
 252                  *    perform other post-processing fixes
 253                  *    as per draft-ietf-ipsec-udp-encaps-06,
 254                  *    section 3.1.2
 255                  */
 256                 if (x->props.mode == XFRM_MODE_TRANSPORT)
 257                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 258         }
 259
 260         iph->protocol = nexthdr[1];
 261         pskb_trim(skb, skb->len - alen - padlen - 2);
 262         skb->h.raw = __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen) - ihl;
 263
 264         return 0;
 265
 266 out:
 267         return -EINVAL;
 268 }
 269
 270 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 271 {
 272         struct esp_data *esp = x->data;
 273         u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
 274
 275         if (x->props.mode == XFRM_MODE_TUNNEL) {
 276                 mtu = ALIGN(mtu + 2, blksize);
 277         } else {
 278                 /* The worst case. */
 279                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 280         }
 281         if (esp->conf.padlen)
 282                 mtu = ALIGN(mtu, esp->conf.padlen);
 283
 284         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 285 }
 286
 287 static void esp4_err(struct sk_buff *skb, u32 info)
 288 {
 289         struct iphdr *iph = (struct iphdr*)skb->data;
 290         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 291         struct xfrm_state *x;
 292
 293         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 294             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 295                 return;
 296
 297         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 298         if (!x)
 299                 return;
 300         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 301                  ntohl(esph->spi), ntohl(iph->daddr));
 302         xfrm_state_put(x);
 303 }
 304
 305 static void esp_destroy(struct xfrm_state *x)
 306 {
 307         struct esp_data *esp = x->data;
 308
 309         if (!esp)
 310                 return;
 311
 312         crypto_free_blkcipher(esp->conf.tfm);
 313         esp->conf.tfm = NULL;
 314         kfree(esp->conf.ivec);
 315         esp->conf.ivec = NULL;
 316         crypto_free_hash(esp->auth.tfm);
 317         esp->auth.tfm = NULL;
 318         kfree(esp->auth.work_icv);
 319         esp->auth.work_icv = NULL;
 320         kfree(esp);
 321 }
 322
 323 static int esp_init_state(struct xfrm_state *x)
 324 {
 325         struct esp_data *esp = NULL;
 326         struct crypto_blkcipher *tfm;
 327
 328         /* null auth and encryption can have zero length keys */
 329         if (x->aalg) {
 330                 if (x->aalg->alg_key_len > 512)
 331                         goto error;
 332         }
 333         if (x->ealg == NULL)
 334                 goto error;
 335
 336         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 337         if (esp == NULL)
 338                 return -ENOMEM;
 339
 340         if (x->aalg) {
 341                 struct xfrm_algo_desc *aalg_desc;
 342                 struct crypto_hash *hash;
 343
 344                 esp->auth.key = x->aalg->alg_key;
 345                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 346                 hash = crypto_alloc_hash(x->aalg->alg_name, 0,
 347                                          CRYPTO_ALG_ASYNC);
 348                 if (IS_ERR(hash))
 349                         goto error;
 350
 351                 esp->auth.tfm = hash;
 352                 if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))
 353                         goto error;
 354
 355                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 356                 BUG_ON(!aalg_desc);
 357
 358                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 359                     crypto_hash_digestsize(hash)) {
 360                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 361                                  x->aalg->alg_name,
 362                                  crypto_hash_digestsize(hash),
 363                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 364                         goto error;
 365                 }
 366
 367                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 368                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 369
 370                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 371                 if (!esp->auth.work_icv)
 372                         goto error;
 373         }
 374         esp->conf.key = x->ealg->alg_key;
 375         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 376         tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
 377         if (IS_ERR(tfm))
 378                 goto error;
 379         esp->conf.tfm = tfm;
 380         esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
 381         esp->conf.padlen = 0;
 382         if (esp->conf.ivlen) {
 383                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 384                 if (unlikely(esp->conf.ivec == NULL))
 385                         goto error;
 386                 esp->conf.ivinitted = 0;
 387         }
 388         if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))
 389                 goto error;
 390         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 391         if (x->props.mode == XFRM_MODE_TUNNEL)
 392                 x->props.header_len += sizeof(struct iphdr);
 393         if (x->encap) {
 394                 struct xfrm_encap_tmpl *encap = x->encap;
 395
 396                 switch (encap->encap_type) {
 397                 default:
 398                         goto error;
 399                 case UDP_ENCAP_ESPINUDP:
 400                         x->props.header_len += sizeof(struct udphdr);
 401                         break;
 402                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 403                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 404                         break;
 405                 }
 406         }
 407         x->data = esp;
 408         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 409         return 0;
 410
 411 error:
 412         x->data = esp;
 413         esp_destroy(x);
 414         x->data = NULL;
 415         return -EINVAL;
 416 }
 417
 418 static struct xfrm_type esp_type =
 419 {
 420         .description    = "ESP4",
 421         .owner          = THIS_MODULE,
 422         .proto          = IPPROTO_ESP,
 423         .init_state     = esp_init_state,
 424         .destructor     = esp_destroy,
 425         .get_max_size   = esp4_get_max_size,
 426         .input          = esp_input,
 427         .output         = esp_output
 428 };
 429
 430 static struct net_protocol esp4_protocol = {
 431         .handler        =       xfrm4_rcv,
 432         .err_handler    =       esp4_err,
 433         .no_policy      =       1,
 434 };
 435
 436 static int __init esp4_init(void)
 437 {
 438         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 439                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 440                 return -EAGAIN;
 441         }
 442         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 443                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 444                 xfrm_unregister_type(&esp_type, AF_INET);
 445                 return -EAGAIN;
 446         }
 447         return 0;
 448 }
 449
 450 static void __exit esp4_fini(void)
 451 {
 452         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 453                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 454         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 455                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 456 }
 457
 458 module_init(esp4_init);
 459 module_exit(esp4_fini);
 460 MODULE_LICENSE("GPL");