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
  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 xfrm_decap_state *decap, 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 encap_len = 0;
 146         u8 nexthdr[2];
 147         struct scatterlist *sg;
 148         u8 workbuf[60];
 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         iph = skb->nh.iph;
 180
 181         /* Get ivec. This can be wrong, check against another impls. */
 182         if (esp->conf.ivlen)
 183                 crypto_cipher_set_iv(esp->conf.tfm, esph->enc_data, crypto_tfm_alg_ivsize(esp->conf.tfm));
 184
 185         sg = &esp->sgbuf[0];
 186
 187         if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 188                 sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
 189                 if (!sg)
 190                         goto out;
 191         }
 192         skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
 193         crypto_cipher_decrypt(esp->conf.tfm, sg, sg, elen);
 194         if (unlikely(sg != &esp->sgbuf[0]))
 195                 kfree(sg);
 196
 197         if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
 198                 BUG();
 199
 200         padlen = nexthdr[0];
 201         if (padlen+2 >= elen)
 202                 goto out;
 203
 204         /* ... check padding bits here. Silly. :-) */
 205
 206         if (x->encap) {
 207                 struct xfrm_encap_tmpl *encap = x->encap;
 208                 struct udphdr *uh;
 209
 210                 if (encap->encap_type != decap->decap_type)
 211                         goto out;
 212
 213                 uh = (struct udphdr *)(iph + 1);
 214                 encap_len = (void*)esph - (void*)uh;
 215
 216                 /*
 217                  * 1) if the NAT-T peer's IP or port changed then
 218                  *    advertize the change to the keying daemon.
 219                  *    This is an inbound SA, so just compare
 220                  *    SRC ports.
 221                  */
 222                 if (iph->saddr != x->props.saddr.a4 ||
 223                     uh->source != encap->encap_sport) {
 224                         xfrm_address_t ipaddr;
 225
 226                         ipaddr.a4 = iph->saddr;
 227                         km_new_mapping(x, &ipaddr, uh->source);
 228
 229                         /* XXX: perhaps add an extra
 230                          * policy check here, to see
 231                          * if we should allow or
 232                          * reject a packet from a
 233                          * different source
 234                          * address/port.
 235                          */
 236                 }
 237
 238                 /*
 239                  * 2) ignore UDP/TCP checksums in case
 240                  *    of NAT-T in Transport Mode, or
 241                  *    perform other post-processing fixes
 242                  *    as per draft-ietf-ipsec-udp-encaps-06,
 243                  *    section 3.1.2
 244                  */
 245                 if (!x->props.mode)
 246                         skb->ip_summed = CHECKSUM_UNNECESSARY;
 247         }
 248
 249         iph->protocol = nexthdr[1];
 250         pskb_trim(skb, skb->len - alen - padlen - 2);
 251         memcpy(workbuf, skb->nh.raw, iph->ihl*4);
 252         skb->h.raw = skb_pull(skb, sizeof(struct ip_esp_hdr) + esp->conf.ivlen);
 253         skb->nh.raw += encap_len + sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 254         memcpy(skb->nh.raw, workbuf, iph->ihl*4);
 255         skb->nh.iph->tot_len = htons(skb->len);
 256
 257         return 0;
 258
 259 out:
 260         return -EINVAL;
 261 }
 262
 263 static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 264 {
 265         struct esp_data *esp = x->data;
 266         u32 blksize = ALIGN(crypto_tfm_alg_blocksize(esp->conf.tfm), 4);
 267
 268         if (x->props.mode) {
 269                 mtu = ALIGN(mtu + 2, blksize);
 270         } else {
 271                 /* The worst case. */
 272                 mtu = ALIGN(mtu + 2, 4) + blksize - 4;
 273         }
 274         if (esp->conf.padlen)
 275                 mtu = ALIGN(mtu, esp->conf.padlen);
 276
 277         return mtu + x->props.header_len + esp->auth.icv_trunc_len;
 278 }
 279
 280 static void esp4_err(struct sk_buff *skb, u32 info)
 281 {
 282         struct iphdr *iph = (struct iphdr*)skb->data;
 283         struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
 284         struct xfrm_state *x;
 285
 286         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 287             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 288                 return;
 289
 290         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
 291         if (!x)
 292                 return;
 293         NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
 294                  ntohl(esph->spi), ntohl(iph->daddr));
 295         xfrm_state_put(x);
 296 }
 297
 298 static void esp_destroy(struct xfrm_state *x)
 299 {
 300         struct esp_data *esp = x->data;
 301
 302         if (!esp)
 303                 return;
 304
 305         crypto_free_tfm(esp->conf.tfm);
 306         esp->conf.tfm = NULL;
 307         kfree(esp->conf.ivec);
 308         esp->conf.ivec = NULL;
 309         crypto_free_tfm(esp->auth.tfm);
 310         esp->auth.tfm = NULL;
 311         kfree(esp->auth.work_icv);
 312         esp->auth.work_icv = NULL;
 313         kfree(esp);
 314 }
 315
 316 static int esp_init_state(struct xfrm_state *x)
 317 {
 318         struct esp_data *esp = NULL;
 319
 320         /* null auth and encryption can have zero length keys */
 321         if (x->aalg) {
 322                 if (x->aalg->alg_key_len > 512)
 323                         goto error;
 324         }
 325         if (x->ealg == NULL)
 326                 goto error;
 327
 328         esp = kmalloc(sizeof(*esp), GFP_KERNEL);
 329         if (esp == NULL)
 330                 return -ENOMEM;
 331
 332         memset(esp, 0, sizeof(*esp));
 333
 334         if (x->aalg) {
 335                 struct xfrm_algo_desc *aalg_desc;
 336
 337                 esp->auth.key = x->aalg->alg_key;
 338                 esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
 339                 esp->auth.tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 340                 if (esp->auth.tfm == NULL)
 341                         goto error;
 342                 esp->auth.icv = esp_hmac_digest;
 343
 344                 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 345                 BUG_ON(!aalg_desc);
 346
 347                 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 348                     crypto_tfm_alg_digestsize(esp->auth.tfm)) {
 349                         NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
 350                                  x->aalg->alg_name,
 351                                  crypto_tfm_alg_digestsize(esp->auth.tfm),
 352                                  aalg_desc->uinfo.auth.icv_fullbits/8);
 353                         goto error;
 354                 }
 355
 356                 esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 357                 esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 358
 359                 esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
 360                 if (!esp->auth.work_icv)
 361                         goto error;
 362         }
 363         esp->conf.key = x->ealg->alg_key;
 364         esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
 365         if (x->props.ealgo == SADB_EALG_NULL)
 366                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_ECB);
 367         else
 368                 esp->conf.tfm = crypto_alloc_tfm(x->ealg->alg_name, CRYPTO_TFM_MODE_CBC);
 369         if (esp->conf.tfm == NULL)
 370                 goto error;
 371         esp->conf.ivlen = crypto_tfm_alg_ivsize(esp->conf.tfm);
 372         esp->conf.padlen = 0;
 373         if (esp->conf.ivlen) {
 374                 esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
 375                 if (unlikely(esp->conf.ivec == NULL))
 376                         goto error;
 377                 get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
 378         }
 379         if (crypto_cipher_setkey(esp->conf.tfm, esp->conf.key, esp->conf.key_len))
 380                 goto error;
 381         x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
 382         if (x->props.mode)
 383                 x->props.header_len += sizeof(struct iphdr);
 384         if (x->encap) {
 385                 struct xfrm_encap_tmpl *encap = x->encap;
 386
 387                 switch (encap->encap_type) {
 388                 default:
 389                         goto error;
 390                 case UDP_ENCAP_ESPINUDP:
 391                         x->props.header_len += sizeof(struct udphdr);
 392                         break;
 393                 case UDP_ENCAP_ESPINUDP_NON_IKE:
 394                         x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
 395                         break;
 396                 }
 397         }
 398         x->data = esp;
 399         x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
 400         return 0;
 401
 402 error:
 403         x->data = esp;
 404         esp_destroy(x);
 405         x->data = NULL;
 406         return -EINVAL;
 407 }
 408
 409 static struct xfrm_type esp_type =
 410 {
 411         .description    = "ESP4",
 412         .owner          = THIS_MODULE,
 413         .proto          = IPPROTO_ESP,
 414         .init_state     = esp_init_state,
 415         .destructor     = esp_destroy,
 416         .get_max_size   = esp4_get_max_size,
 417         .input          = esp_input,
 418         .output         = esp_output
 419 };
 420
 421 static struct net_protocol esp4_protocol = {
 422         .handler        =       xfrm4_rcv,
 423         .err_handler    =       esp4_err,
 424         .no_policy      =       1,
 425 };
 426
 427 static int __init esp4_init(void)
 428 {
 429         if (xfrm_register_type(&esp_type, AF_INET) < 0) {
 430                 printk(KERN_INFO "ip esp init: can't add xfrm type\n");
 431                 return -EAGAIN;
 432         }
 433         if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
 434                 printk(KERN_INFO "ip esp init: can't add protocol\n");
 435                 xfrm_unregister_type(&esp_type, AF_INET);
 436                 return -EAGAIN;
 437         }
 438         return 0;
 439 }
 440
 441 static void __exit esp4_fini(void)
 442 {
 443         if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
 444                 printk(KERN_INFO "ip esp close: can't remove protocol\n");
 445         if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
 446                 printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
 447 }
 448
 449 module_init(esp4_init);
 450 module_exit(esp4_fini);
 451 MODULE_LICENSE("GPL");