net/ipv4/esp4.c

   1 #include <linux/module.h>
   2 #include <net/ip.h>
   3 #include <net/xfrm.h>
   4 #include <net/esp.h>
   5 #include <asm/scatterlist.h>
   6 #include <linux/crypto.h>
   7 #include <linux/kernel.h>
   8 #include <linux/pfkeyv2.h>
   9 #include <linux/random.h>
  10 #include <net/icmp.h>
  11 #include <net/protocol.h>
  12 #include <net/udp.h>
  13
  14 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  15 {
  16         int err;
  17         struct iphdr *top_iph;
  18         struct ip_esp_hdr *esph;
  19         struct crypto_tfm *tfm;
  20         struct esp_data *esp;
  21         struct sk_buff *trailer;
  22         int blksize;
  23         int clen;
  24         int alen;
  25         int nfrags;
  26
  27         /* Strip IP+ESP header. */
  28         __skb_pull(skb, skb->h.raw - skb->data);
  29         /* Now skb is pure payload to encrypt */
  30
  31         err = -ENOMEM;
  32
  33         /* Round to block size */
  34         clen = skb->len;
  35
  36         esp = x->data;
  37         alen = esp->auth.icv_trunc_len;
  38         tfm = esp->conf.tfm;
  39         blksize = ALIGN(crypto_tfm_alg_blocksize(tfm), 4);
  40         clen = ALIGN(clen + 2, blksize);
  41         if (esp->conf.padlen)
  42                 clen = ALIGN(clen, esp->conf.padlen);
  43
  44         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  45                 goto error;
  46
  47         /* Fill padding... */
  48         do {
  49                 int i;
  50                 for (i=0; i<clen-skb->len - 2; i++)
  51                         *(u8*)(trailer->tail + i) = i+1;
  52         } while (0);
  53         *(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
  54         pskb_put(skb, trailer, clen - skb->len);
  55
  56         __skb_push(skb, skb->data - skb->nh.raw);
  57         top_iph = skb->nh.iph;
  58         esph = (struct ip_esp_hdr *)(skb->nh.raw + top_iph->ihl*4);
  59         top_iph->tot_len = htons(skb->len + alen);
  60         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  61
  62         /* this is non-NULL only with UDP Encapsulation */
  63         if (x->encap) {
  64                 struct xfrm_encap_tmpl *encap = x->encap;
  65                 struct udphdr *uh;
  66                 u32 *udpdata32;
  67
  68                 uh = (struct udphdr *)esph;
  69                 uh->source = encap->encap_sport;
  70                 uh->dest = encap->encap_dport;
  71                 uh->len = htons(skb->len + alen - top_iph->ihl*4);
  72                 uh->check = 0;
  73
  74                 switch (encap->encap_type) {
  75                 default:
  76                 case UDP_ENCAP_ESPINUDP:
  77                         esph = (struct ip_esp_hdr *)(uh + 1);
  78                         break;
  79                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  80                         udpdata32 = (u32 *)(uh + 1);
  81                         udpdata32[0] = udpdata32[1] = 0;
  82                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  83                         break;
  84                 }
  85
  86                 top_iph->protocol = IPPROTO_UDP;
  87         } else
  88                 top_iph->protocol = IPPROTO_ESP;
  89
  90         esph->spi = x->id.spi;
  91         esph->seq_no = htonl(++x->replay.oseq);
  92         xfrm_aevent_doreplay(x);
  93
  94         if (esp->conf.ivlen)
  95                 crypto_cipher_set_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
  96
  97         do {
  98                 struct scatterlist *sg = &esp->sgbuf[0];
  99
 100                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 101                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 102                         if (!sg)
 103                                 goto error;
 104                 }
 105                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 106                 crypto_cipher_encrypt(tfm, sg, sg, clen);
 107                 if (unlikely(sg != &esp->sgbuf[0]))
 108                         kfree(sg);
 109         } while (0);
 110
 111         if (esp->conf.ivlen) {
 112                 memcpy(esph->enc_data, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 113                 crypto_cipher_get_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 114         }
 115
 116         if (esp->auth.icv_full_len) {
 117                 esp->auth.icv(esp, skb, (u8*)esph-skb->data,
 118                               sizeof(struct ip_esp_hdr) + esp->conf.ivlen+clen, trailer->tail);
 119                 pskb_put(skb, trailer, alen);
 120         }
 121
 122         ip_send_check(top_iph);
 123
 124         err = 0;
 125
 126 error:
 127         return err;
 128 }
 129
 130 /*
 131  * Note: detecting truncated vs. non-truncated authentication data is very
 132  * expensive, so we only support truncated data, which is the recommended
 133  * and common case.
 134  */
 135 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 136 {
 137         struct iphdr *iph;
 138         struct ip_esp_hdr *esph;
 139         struct esp_data *esp = x->data;
 140         struct sk_buff *trailer;
 141         int blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 142         int alen = esp->auth.icv_trunc_len;
 143         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 144         int nfrags;
 145         int ihl;
 146         u8 nexthdr[2];
 147         struct scatterlist *sg;
 148         int padlen;
 149
 150         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 151                 goto out;
 152
 153         if (elen <= 0 || (elen & (blksize-1)))
 154                 goto out;
 155
 156         /* If integrity check is required, do this. */
 157         if (esp->auth.icv_full_len) {
 158                 u8 sum[esp->auth.icv_full_len];
 159                 u8 sum1[alen];
 160
 161                 esp->auth.icv(esp, skb, 0, skb->len-alen, sum);
 162
 163                 if (skb_copy_bits(skb, skb->len-alen, sum1, alen))
 164                         BUG();
 165
 166                 if (unlikely(memcmp(sum, sum1, alen))) {
 167                         x->stats.integrity_failed++;
 168                         goto out;
 169                 }
 170         }
 171
 172         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 173                 goto out;
 174
 175         skb->ip_summed = CHECKSUM_NONE;
 176
 177         esph = (struct ip_esp_hdr*)skb->data;
 178
 179         /* Get ivec. This can be wrong, check against another impls. */
 180         if (esp->conf.ivlen)
 181                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 182
 183         sg = &esp->sgbuf[0];
 184
 185         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 186                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 187                 if (!sg)
 188                         goto out;
 189         }
 190         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 191         crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 192         if (unlikely(sg != &esp->sgbuf[0]))
 193                 kfree(sg);
 194
 195         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 196                 BUG();
 197
 198         padlen = nexthdr[0];
 199         if (padlen+2 >= elen)
 200                 goto out;
 201
 202         /* ... check padding bits here. Silly. :-) */
 203
 204         iph = skb->nh.iph;
 205         ihl = iph->ihl * 4;
 206
 207         if (x->encap) {
 208                 struct xfrm_encap_tmpl *encap = x->encap;
 209                 struct udphdr *uh = (void *)(skb->nh.raw + ihl);
 210
 211                 /*
 212                  * 1) if the NAT-T peer's IP or port changed then
 213                  *    advertize the change to the keying daemon.
 214                  *    This is an inbound SA, so just compare
 215                  *    SRC ports.
 216                  */
 217                 if (iph->saddr != x->props.saddr.a4 ||
 218                     uh->source != encap->encap_sport) {
 219                         xfrm_address_t ipaddr;
 220
 221                         ipaddr.a4 = iph->saddr;
 222                         km_new_mapping(x, &ipaddr, uh->source);
 223
 224                         /* XXX: perhaps add an extra
 225                          * policy check here, to see
 226                          * if we should allow or
 227                          * reject a packet from a
 228                          * different source
 229                          * address/port.
 230                          */
 231                 }
 232
 233                 /*
 234                  * 2) ignore UDP/TCP checksums in case
 235                  *    of NAT-T in Transport Mode, or
 236                  *    perform other post-processing fixes
 237                  *    as per draft-ietf-ipsec-udp-encaps-06,
 238                  *    section 3.1.2
 239                  */
 240                 if (!x->props.mode)
 241                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 242         }
 243
 244         iph->protocol = nexthdr[1];
 245         pskb_trim(skb, skb->len - alen - padlen - 2);
 246         skb->h.raw = __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen) - ihl;
 247
 248         return 0;
 249
 250 out:
 251         return -EINVAL;
 252 }
 253
 254 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 255 {
 256         struct esp_data *esp = x->data;
 257         u32 blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 258
 259         if (x->props.mode) {
 260                 mtu = ALIGN(mtu + 2, blksize);
 261         } else {
 262                 /* The worst case. */
 263                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 264         }
 265         if (esp->conf.padlen)
 266                 mtu = ALIGN(mtu, esp->conf.padlen);
 267
 268         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 269 }
 270
 271 static void esp4_err(struct sk_buff *skb, u32 info)
 272 {
 273         struct iphdr *iph = (struct iphdr*)skb->data;
 274         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 275         struct xfrm_state *x;
 276
 277         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 278             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 279                 return;
 280
 281         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 282         if (!x)
 283                 return;
 284         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 285                  ntohl(esph->spi), ntohl(iph->daddr));
 286         xfrm_state_put(x);
 287 }
 288
 289 static void esp_destroy(struct xfrm_state *x)
 290 {
 291         struct esp_data *esp = x->data;
 292
 293         if (!esp)
 294                 return;
 295
 296         crypto_free_tfm(esp->conf.tfm);
 297         esp->conf.tfm = NULL;
 298         kfree(esp->conf.ivec);
 299         esp->conf.ivec = NULL;
 300         crypto_free_tfm(esp->auth.tfm);
 301         esp->auth.tfm = NULL;
 302         kfree(esp->auth.work_icv);
 303         esp->auth.work_icv = NULL;
 304         kfree(esp);
 305 }
 306
 307 static int esp_init_state(struct xfrm_state *x)
 308 {
 309         struct esp_data *esp = NULL;
 310
 311         /* null auth and encryption can have zero length keys */
 312         if (x->aalg) {
 313                 if (x->aalg->alg_key_len > 512)
 314                         goto error;
 315         }
 316         if (x->ealg == NULL)
 317                 goto error;
 318
 319         esp = kzalloc(sizeof(*esp), GFP_KERNEL);
 320         if (esp == NULL)
 321                 return -ENOMEM;
 322
 323         if (x->aalg) {
 324                 struct xfrm_algo_desc *aalg_desc;
 325
 326                 esp->auth.key = x->aalg->alg_key;
 327                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 328                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 329                 if (esp->auth.tfm == NULL)
 330                         goto error;
 331                 esp->auth.icv = esp_hmac_digest;
 332
 333                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 334                 BUG_ON(!aalg_desc);
 335
 336                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 337                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 338                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 339                                  x->aalg->alg_name,
 340                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 341                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 342                         goto error;
 343                 }
 344
 345                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 346                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 347
 348                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 349                 if (!esp->auth.work_icv)
 350                         goto error;
 351         }
 352         esp->conf.key = x->ealg->alg_key;
 353         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 354         if (x->props.ealgo == SADB_EALG_NULL)
 355                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 356         else
 357                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 358         if (esp->conf.tfm == NULL)
 359                 goto error;
 360         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 361         esp->conf.padlen = 0;
 362         if (esp->conf.ivlen) {
 363                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 364                 if (unlikely(esp->conf.ivec == NULL))
 365                         goto error;
 366                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 367         }
 368         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 369                 goto error;
 370         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 371         if (x->props.mode)
 372                 x->props.header_len += sizeof(struct iphdr);
 373         if (x->encap) {
 374                 struct xfrm_encap_tmpl *encap = x->encap;
 375
 376                 switch (encap->encap_type) {
 377                 default:
 378                         goto error;
 379                 case UDP_ENCAP_ESPINUDP:
 380                         x->props.header_len += sizeof(struct udphdr);
 381                         break;
 382                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 383                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 384                         break;
 385                 }
 386         }
 387         x->data = esp;
 388         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 389         return 0;
 390
 391 error:
 392         x->data = esp;
 393         esp_destroy(x);
 394         x->data = NULL;
 395         return -EINVAL;
 396 }
 397
 398 static struct xfrm_type esp_type =
 399 {
 400         .description    = "ESP4",
 401         .owner          = THIS_MODULE,
 402         .proto          = IPPROTO_ESP,
 403         .init_state     = esp_init_state,
 404         .destructor     = esp_destroy,
 405         .get_max_size   = esp4_get_max_size,
 406         .input          = esp_input,
 407         .output         = esp_output
 408 };
 409
 410 static struct net_protocol esp4_protocol = {
 411         .handler        =       xfrm4_rcv,
 412         .err_handler    =       esp4_err,
 413         .no_policy      =       1,
 414 };
 415
 416 static int __init esp4_init(void)
 417 {
 418         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 419                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 420                 return -EAGAIN;
 421         }
 422         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 423                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 424                 xfrm_unregister_type(&esp_type, AF_INET);
 425                 return -EAGAIN;
 426         }
 427         return 0;
 428 }
 429
 430 static void __exit esp4_fini(void)
 431 {
 432         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 433                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 434         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 435                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 436 }
 437
 438 module_init(esp4_init);
 439 module_exit(esp4_fini);
 440 MODULE_LICENSE("GPL");