net/ipv4/esp4.c

   1 #include <linux/config.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_tfm *tfm;
  21         struct esp_data *esp;
  22         struct sk_buff *trailer;
  23         int blksize;
  24         int clen;
  25         int alen;
  26         int nfrags;
  27
  28         /* Strip IP+ESP header. */
  29         __skb_pull(skb, skb->h.raw - skb->data);
  30         /* Now skb is pure payload to encrypt */
  31
  32         err = -ENOMEM;
  33
  34         /* Round to block size */
  35         clen = skb->len;
  36
  37         esp = x->data;
  38         alen = esp->auth.icv_trunc_len;
  39         tfm = esp->conf.tfm;
  40         blksize = ALIGN(crypto_tfm_alg_blocksize(tfm), 4);
  41         clen = ALIGN(clen + 2, blksize);
  42         if (esp->conf.padlen)
  43                 clen = ALIGN(clen, esp->conf.padlen);
  44
  45         if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
  46                 goto error;
  47
  48         /* Fill padding... */
  49         do {
  50                 int i;
  51                 for (i=0; i<clen-skb->len - 2; i++)
  52                         *(u8*)(trailer->tail + i) = i+1;
  53         } while (0);
  54         *(u8*)(trailer->tail + clen-skb->len - 2) = (clen - skb->len)-2;
  55         pskb_put(skb, trailer, clen - skb->len);
  56
  57         __skb_push(skb, skb->data - skb->nh.raw);
  58         top_iph = skb->nh.iph;
  59         esph = (struct ip_esp_hdr *)(skb->nh.raw + top_iph->ihl*4);
  60         top_iph->tot_len = htons(skb->len + alen);
  61         *(u8*)(trailer->tail - 1) = top_iph->protocol;
  62
  63         /* this is non-NULL only with UDP Encapsulation */
  64         if (x->encap) {
  65                 struct xfrm_encap_tmpl *encap = x->encap;
  66                 struct udphdr *uh;
  67                 u32 *udpdata32;
  68
  69                 uh = (struct udphdr *)esph;
  70                 uh->source = encap->encap_sport;
  71                 uh->dest = encap->encap_dport;
  72                 uh->len = htons(skb->len + alen - top_iph->ihl*4);
  73                 uh->check = 0;
  74
  75                 switch (encap->encap_type) {
  76                 default:
  77                 case UDP_ENCAP_ESPINUDP:
  78                         esph = (struct ip_esp_hdr *)(uh + 1);
  79                         break;
  80                 case UDP_ENCAP_ESPINUDP_NON_IKE:
  81                         udpdata32 = (u32 *)(uh + 1);
  82                         udpdata32[0] = udpdata32[1] = 0;
  83                         esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  84                         break;
  85                 }
  86
  87                 top_iph->protocol = IPPROTO_UDP;
  88         } else
  89                 top_iph->protocol = IPPROTO_ESP;
  90
  91         esph->spi = x->id.spi;
  92         esph->seq_no = htonl(++x->replay.oseq);
  93         xfrm_aevent_doreplay(x);
  94
  95         if (esp->conf.ivlen)
  96                 crypto_cipher_set_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
  97
  98         do {
  99                 struct scatterlist *sg = &esp->sgbuf[0];
 100
 101                 if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 102                         sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 103                         if (!sg)
 104                                 goto error;
 105                 }
 106                 skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
 107                 crypto_cipher_encrypt(tfm, sg, sg, clen);
 108                 if (unlikely(sg != &esp->sgbuf[0]))
 109                         kfree(sg);
 110         } while (0);
 111
 112         if (esp->conf.ivlen) {
 113                 memcpy(esph->enc_data, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 114                 crypto_cipher_get_iv(tfm, esp->conf.ivec, crypto_tfm_alg_ivsize(tfm));
 115         }
 116
 117         if (esp->auth.icv_full_len) {
 118                 esp->auth.icv(esp, skb, (u8*)esph-skb->data,
 119                               sizeof(struct ip_esp_hdr) + esp->conf.ivlen+clen, trailer->tail);
 120                 pskb_put(skb, trailer, alen);
 121         }
 122
 123         ip_send_check(top_iph);
 124
 125         err = 0;
 126
 127 error:
 128         return err;
 129 }
 130
 131 /*
 132  * Note: detecting truncated vs. non-truncated authentication data is very
 133  * expensive, so we only support truncated data, which is the recommended
 134  * and common case.
 135  */
 136 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 137 {
 138         struct iphdr *iph;
 139         struct ip_esp_hdr *esph;
 140         struct esp_data *esp = x->data;
 141         struct sk_buff *trailer;
 142         int blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 143         int alen = esp->auth.icv_trunc_len;
 144         int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
 145         int nfrags;
 146         int encap_len = 0;
 147         u8 nexthdr[2];
 148         struct scatterlist *sg;
 149         u8 workbuf[60];
 150         int padlen;
 151
 152         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 153                 goto out;
 154
 155         if (elen <= 0 || (elen & (blksize-1)))
 156                 goto out;
 157
 158         /* If integrity check is required, do this. */
 159         if (esp->auth.icv_full_len) {
 160                 u8 sum[esp->auth.icv_full_len];
 161                 u8 sum1[alen];
 162
 163                 esp->auth.icv(esp, skb, 0, skb->len-alen, sum);
 164
 165                 if (skb_copy_bits(skb, skb->len-alen, sum1, alen))
 166                         BUG();
 167
 168                 if (unlikely(memcmp(sum, sum1, alen))) {
 169                         x->stats.integrity_failed++;
 170                         goto out;
 171                 }
 172         }
 173
 174         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 175                 goto out;
 176
 177         skb->ip_summed = CHECKSUM_NONE;
 178
 179         esph = (struct ip_esp_hdr*)skb->data;
 180         iph = skb->nh.iph;
 181
 182         /* Get ivec. This can be wrong, check against another impls. */
 183         if (esp->conf.ivlen)
 184                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 185
 186         sg = &esp->sgbuf[0];
 187
 188         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 189                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 190                 if (!sg)
 191                         goto out;
 192         }
 193         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 194         crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 195         if (unlikely(sg != &esp->sgbuf[0]))
 196                 kfree(sg);
 197
 198         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 199                 BUG();
 200
 201         padlen = nexthdr[0];
 202         if (padlen+2 >= elen)
 203                 goto out;
 204
 205         /* ... check padding bits here. Silly. :-) */
 206
 207         if (x->encap) {
 208                 struct xfrm_encap_tmpl *encap = x->encap;
 209                 struct udphdr *uh;
 210
 211                 uh = (struct udphdr *)(iph + 1);
 212                 encap_len = (void*)esph - (void*)uh;
 213
 214                 /*
 215                  * 1) if the NAT-T peer's IP or port changed then
 216                  *    advertize the change to the keying daemon.
 217                  *    This is an inbound SA, so just compare
 218                  *    SRC ports.
 219                  */
 220                 if (iph->saddr != x->props.saddr.a4 ||
 221                     uh->source != encap->encap_sport) {
 222                         xfrm_address_t ipaddr;
 223
 224                         ipaddr.a4 = iph->saddr;
 225                         km_new_mapping(x, &ipaddr, uh->source);
 226
 227                         /* XXX: perhaps add an extra
 228                          * policy check here, to see
 229                          * if we should allow or
 230                          * reject a packet from a
 231                          * different source
 232                          * address/port.
 233                          */
 234                 }
 235
 236                 /*
 237                  * 2) ignore UDP/TCP checksums in case
 238                  *    of NAT-T in Transport Mode, or
 239                  *    perform other post-processing fixes
 240                  *    as per draft-ietf-ipsec-udp-encaps-06,
 241                  *    section 3.1.2
 242                  */
 243                 if (!x->props.mode)
 244                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 245         }
 246
 247         iph->protocol = nexthdr[1];
 248         pskb_trim(skb, skb->len - alen - padlen - 2);
 249         memcpy(workbuf, skb->nh.raw, iph->ihl*4);
 250         skb->h.raw = skb_pull(skb, sizeof(struct ip_esp_hdr) + esp->conf.ivlen);
 251         skb->nh.raw += encap_len + sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 252         memcpy(skb->nh.raw, workbuf, iph->ihl*4);
 253         skb->nh.iph->tot_len = htons(skb->len);
 254
 255         return 0;
 256
 257 out:
 258         return -EINVAL;
 259 }
 260
 261 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 262 {
 263         struct esp_data *esp = x->data;
 264         u32 blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 265
 266         if (x->props.mode) {
 267                 mtu = ALIGN(mtu + 2, blksize);
 268         } else {
 269                 /* The worst case. */
 270                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 271         }
 272         if (esp->conf.padlen)
 273                 mtu = ALIGN(mtu, esp->conf.padlen);
 274
 275         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 276 }
 277
 278 static void esp4_err(struct sk_buff *skb, u32 info)
 279 {
 280         struct iphdr *iph = (struct iphdr*)skb->data;
 281         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 282         struct xfrm_state *x;
 283
 284         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 285             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 286                 return;
 287
 288         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 289         if (!x)
 290                 return;
 291         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 292                  ntohl(esph->spi), ntohl(iph->daddr));
 293         xfrm_state_put(x);
 294 }
 295
 296 static void esp_destroy(struct xfrm_state *x)
 297 {
 298         struct esp_data *esp = x->data;
 299
 300         if (!esp)
 301                 return;
 302
 303         crypto_free_tfm(esp->conf.tfm);
 304         esp->conf.tfm = NULL;
 305         kfree(esp->conf.ivec);
 306         esp->conf.ivec = NULL;
 307         crypto_free_tfm(esp->auth.tfm);
 308         esp->auth.tfm = NULL;
 309         kfree(esp->auth.work_icv);
 310         esp->auth.work_icv = NULL;
 311         kfree(esp);
 312 }
 313
 314 static int esp_init_state(struct xfrm_state *x)
 315 {
 316         struct esp_data *esp = NULL;
 317
 318         /* null auth and encryption can have zero length keys */
 319         if (x->aalg) {
 320                 if (x->aalg->alg_key_len > 512)
 321                         goto error;
 322         }
 323         if (x->ealg == NULL)
 324                 goto error;
 325
 326         esp = kmalloc(sizeof(*esp), GFP_KERNEL);
 327         if (esp == NULL)
 328                 return -ENOMEM;
 329
 330         memset(esp, 0, sizeof(*esp));
 331
 332         if (x->aalg) {
 333                 struct xfrm_algo_desc *aalg_desc;
 334
 335                 esp->auth.key = x->aalg->alg_key;
 336                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 337                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 338                 if (esp->auth.tfm == NULL)
 339                         goto error;
 340                 esp->auth.icv = esp_hmac_digest;
 341
 342                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 343                 BUG_ON(!aalg_desc);
 344
 345                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 346                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 347                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 348                                  x->aalg->alg_name,
 349                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 350                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 351                         goto error;
 352                 }
 353
 354                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 355                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 356
 357                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 358                 if (!esp->auth.work_icv)
 359                         goto error;
 360         }
 361         esp->conf.key = x->ealg->alg_key;
 362         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 363         if (x->props.ealgo == SADB_EALG_NULL)
 364                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 365         else
 366                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 367         if (esp->conf.tfm == NULL)
 368                 goto error;
 369         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 370         esp->conf.padlen = 0;
 371         if (esp->conf.ivlen) {
 372                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 373                 if (unlikely(esp->conf.ivec == NULL))
 374                         goto error;
 375                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 376         }
 377         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 378                 goto error;
 379         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 380         if (x->props.mode)
 381                 x->props.header_len += sizeof(struct iphdr);
 382         if (x->encap) {
 383                 struct xfrm_encap_tmpl *encap = x->encap;
 384
 385                 switch (encap->encap_type) {
 386                 default:
 387                         goto error;
 388                 case UDP_ENCAP_ESPINUDP:
 389                         x->props.header_len += sizeof(struct udphdr);
 390                         break;
 391                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 392                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 393                         break;
 394                 }
 395         }
 396         x->data = esp;
 397         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 398         return 0;
 399
 400 error:
 401         x->data = esp;
 402         esp_destroy(x);
 403         x->data = NULL;
 404         return -EINVAL;
 405 }
 406
 407 static struct xfrm_type esp_type =
 408 {
 409         .description    = "ESP4",
 410         .owner          = THIS_MODULE,
 411         .proto          = IPPROTO_ESP,
 412         .init_state     = esp_init_state,
 413         .destructor     = esp_destroy,
 414         .get_max_size   = esp4_get_max_size,
 415         .input          = esp_input,
 416         .output         = esp_output
 417 };
 418
 419 static struct net_protocol esp4_protocol = {
 420         .handler        =       xfrm4_rcv,
 421         .err_handler    =       esp4_err,
 422         .no_policy      =       1,
 423 };
 424
 425 static int __init esp4_init(void)
 426 {
 427         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 428                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 429                 return -EAGAIN;
 430         }
 431         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 432                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 433                 xfrm_unregister_type(&esp_type, AF_INET);
 434                 return -EAGAIN;
 435         }
 436         return 0;
 437 }
 438
 439 static void __exit esp4_fini(void)
 440 {
 441         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 442                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 443         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 444                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 445 }
 446
 447 module_init(esp4_init);
 448 module_exit(esp4_fini);
 449 MODULE_LICENSE("GPL");