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 ihl;
 147         u8 nexthdr[2];
 148         struct scatterlist *sg;
 149         int padlen;
 150
 151         if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
 152                 goto out;
 153
 154         if (elen <= 0 || (elen & (blksize-1)))
 155                 goto out;
 156
 157         /* If integrity check is required, do this. */
 158         if (esp->auth.icv_full_len) {
 159                 u8 sum[esp->auth.icv_full_len];
 160                 u8 sum1[alen];
 161
 162                 esp->auth.icv(esp, skb, 0, skb->len-alen, sum);
 163
 164                 if (skb_copy_bits(skb, skb->len-alen, sum1, alen))
 165                         BUG();
 166
 167                 if (unlikely(memcmp(sum, sum1, alen))) {
 168                         x->stats.integrity_failed++;
 169                         goto out;
 170                 }
 171         }
 172
 173         if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
 174                 goto out;
 175
 176         skb->ip_summed = CHECKSUM_NONE;
 177
 178         esph = (struct ip_esp_hdr*)skb->data;
 179
 180         /* Get ivec. This can be wrong, check against another impls. */
 181         if (esp->conf.ivlen)
 182                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 183
 184         sg = &esp->sgbuf[0];
 185
 186         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 187                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 188                 if (!sg)
 189                         goto out;
 190         }
 191         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 192         crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 193         if (unlikely(sg != &esp->sgbuf[0]))
 194                 kfree(sg);
 195
 196         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 197                 BUG();
 198
 199         padlen = nexthdr[0];
 200         if (padlen+2 >= elen)
 201                 goto out;
 202
 203         /* ... check padding bits here. Silly. :-) */
 204
 205         iph = skb->nh.iph;
 206         ihl = iph->ihl * 4;
 207
 208         if (x->encap) {
 209                 struct xfrm_encap_tmpl *encap = x->encap;
 210                 struct udphdr *uh = (void *)(skb->nh.raw + ihl);
 211
 212                 /*
 213                  * 1) if the NAT-T peer's IP or port changed then
 214                  *    advertize the change to the keying daemon.
 215                  *    This is an inbound SA, so just compare
 216                  *    SRC ports.
 217                  */
 218                 if (iph->saddr != x->props.saddr.a4 ||
 219                     uh->source != encap->encap_sport) {
 220                         xfrm_address_t ipaddr;
 221
 222                         ipaddr.a4 = iph->saddr;
 223                         km_new_mapping(x, &ipaddr, uh->source);
 224
 225                         /* XXX: perhaps add an extra
 226                          * policy check here, to see
 227                          * if we should allow or
 228                          * reject a packet from a
 229                          * different source
 230                          * address/port.
 231                          */
 232                 }
 233
 234                 /*
 235                  * 2) ignore UDP/TCP checksums in case
 236                  *    of NAT-T in Transport Mode, or
 237                  *    perform other post-processing fixes
 238                  *    as per draft-ietf-ipsec-udp-encaps-06,
 239                  *    section 3.1.2
 240                  */
 241                 if (!x->props.mode)
 242                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 243         }
 244
 245         iph->protocol = nexthdr[1];
 246         pskb_trim(skb, skb->len - alen - padlen - 2);
 247         skb->h.raw = __skb_pull(skb, sizeof(*esph) + esp->conf.ivlen) - ihl;
 248
 249         return 0;
 250
 251 out:
 252         return -EINVAL;
 253 }
 254
 255 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 256 {
 257         struct esp_data *esp = x->data;
 258         u32 blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 259
 260         if (x->props.mode) {
 261                 mtu = ALIGN(mtu + 2, blksize);
 262         } else {
 263                 /* The worst case. */
 264                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 265         }
 266         if (esp->conf.padlen)
 267                 mtu = ALIGN(mtu, esp->conf.padlen);
 268
 269         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 270 }
 271
 272 static void esp4_err(struct sk_buff *skb, u32 info)
 273 {
 274         struct iphdr *iph = (struct iphdr*)skb->data;
 275         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 276         struct xfrm_state *x;
 277
 278         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 279             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 280                 return;
 281
 282         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 283         if (!x)
 284                 return;
 285         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 286                  ntohl(esph->spi), ntohl(iph->daddr));
 287         xfrm_state_put(x);
 288 }
 289
 290 static void esp_destroy(struct xfrm_state *x)
 291 {
 292         struct esp_data *esp = x->data;
 293
 294         if (!esp)
 295                 return;
 296
 297         crypto_free_tfm(esp->conf.tfm);
 298         esp->conf.tfm = NULL;
 299         kfree(esp->conf.ivec);
 300         esp->conf.ivec = NULL;
 301         crypto_free_tfm(esp->auth.tfm);
 302         esp->auth.tfm = NULL;
 303         kfree(esp->auth.work_icv);
 304         esp->auth.work_icv = NULL;
 305         kfree(esp);
 306 }
 307
 308 static int esp_init_state(struct xfrm_state *x)
 309 {
 310         struct esp_data *esp = NULL;
 311
 312         /* null auth and encryption can have zero length keys */
 313         if (x->aalg) {
 314                 if (x->aalg->alg_key_len > 512)
 315                         goto error;
 316         }
 317         if (x->ealg == NULL)
 318                 goto error;
 319
 320         esp = kmalloc(sizeof(*esp), GFP_KERNEL);
 321         if (esp == NULL)
 322                 return -ENOMEM;
 323
 324         memset(esp, 0, sizeof(*esp));
 325
 326         if (x->aalg) {
 327                 struct xfrm_algo_desc *aalg_desc;
 328
 329                 esp->auth.key = x->aalg->alg_key;
 330                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 331                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 332                 if (esp->auth.tfm == NULL)
 333                         goto error;
 334                 esp->auth.icv = esp_hmac_digest;
 335
 336                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 337                 BUG_ON(!aalg_desc);
 338
 339                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 340                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 341                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 342                                  x->aalg->alg_name,
 343                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 344                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 345                         goto error;
 346                 }
 347
 348                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 349                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 350
 351                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 352                 if (!esp->auth.work_icv)
 353                         goto error;
 354         }
 355         esp->conf.key = x->ealg->alg_key;
 356         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 357         if (x->props.ealgo == SADB_EALG_NULL)
 358                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 359         else
 360                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 361         if (esp->conf.tfm == NULL)
 362                 goto error;
 363         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 364         esp->conf.padlen = 0;
 365         if (esp->conf.ivlen) {
 366                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 367                 if (unlikely(esp->conf.ivec == NULL))
 368                         goto error;
 369                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 370         }
 371         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 372                 goto error;
 373         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 374         if (x->props.mode)
 375                 x->props.header_len += sizeof(struct iphdr);
 376         if (x->encap) {
 377                 struct xfrm_encap_tmpl *encap = x->encap;
 378
 379                 switch (encap->encap_type) {
 380                 default:
 381                         goto error;
 382                 case UDP_ENCAP_ESPINUDP:
 383                         x->props.header_len += sizeof(struct udphdr);
 384                         break;
 385                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 386                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 387                         break;
 388                 }
 389         }
 390         x->data = esp;
 391         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 392         return 0;
 393
 394 error:
 395         x->data = esp;
 396         esp_destroy(x);
 397         x->data = NULL;
 398         return -EINVAL;
 399 }
 400
 401 static struct xfrm_type esp_type =
 402 {
 403         .description    = "ESP4",
 404         .owner          = THIS_MODULE,
 405         .proto          = IPPROTO_ESP,
 406         .init_state     = esp_init_state,
 407         .destructor     = esp_destroy,
 408         .get_max_size   = esp4_get_max_size,
 409         .input          = esp_input,
 410         .output         = esp_output
 411 };
 412
 413 static struct net_protocol esp4_protocol = {
 414         .handler        =       xfrm4_rcv,
 415         .err_handler    =       esp4_err,
 416         .no_policy      =       1,
 417 };
 418
 419 static int __init esp4_init(void)
 420 {
 421         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 422                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 423                 return -EAGAIN;
 424         }
 425         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 426                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 427                 xfrm_unregister_type(&esp_type, AF_INET);
 428                 return -EAGAIN;
 429         }
 430         return 0;
 431 }
 432
 433 static void __exit esp4_fini(void)
 434 {
 435         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 436                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 437         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 438                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 439 }
 440
 441 module_init(esp4_init);
 442 module_exit(esp4_fini);
 443 MODULE_LICENSE("GPL");