net/ipv4/ah4.c

   1 #include <crypto/hash.h>
   2 #include <linux/err.h>
   3 #include <linux/module.h>
   4 #include <net/ip.h>
   5 #include <net/xfrm.h>
   6 #include <net/ah.h>
   7 #include <linux/crypto.h>
   8 #include <linux/pfkeyv2.h>
   9 #include <linux/scatterlist.h>
  10 #include <net/icmp.h>
  11 #include <net/protocol.h>
  12
  13 struct ah_skb_cb {
  14         struct xfrm_skb_cb xfrm;
  15         void *tmp;
  16 };
  17
  18 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
  19
  20 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
  21                           unsigned int size)
  22 {
  23         unsigned int len;
  24
  25         len = size + crypto_ahash_digestsize(ahash) +
  26               (crypto_ahash_alignmask(ahash) &
  27                ~(crypto_tfm_ctx_alignment() - 1));
  28
  29         len = ALIGN(len, crypto_tfm_ctx_alignment());
  30
  31         len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
  32         len = ALIGN(len, __alignof__(struct scatterlist));
  33
  34         len += sizeof(struct scatterlist) * nfrags;
  35
  36         return kmalloc(len, GFP_ATOMIC);
  37 }
  38
  39 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
  40 {
  41         return tmp + offset;
  42 }
  43
  44 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
  45                              unsigned int offset)
  46 {
  47         return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
  48 }
  49
  50 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
  51                                                u8 *icv)
  52 {
  53         struct ahash_request *req;
  54
  55         req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
  56                                 crypto_tfm_ctx_alignment());
  57
  58         ahash_request_set_tfm(req, ahash);
  59
  60         return req;
  61 }
  62
  63 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  64                                              struct ahash_request *req)
  65 {
  66         return (void *)ALIGN((unsigned long)(req + 1) +
  67                              crypto_ahash_reqsize(ahash),
  68                              __alignof__(struct scatterlist));
  69 }
  70
  71 /* Clear mutable options and find final destination to substitute
  72  * into IP header for icv calculation. Options are already checked
  73  * for validity, so paranoia is not required. */
  74
  75 static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
  76 {
  77         unsigned char * optptr = (unsigned char*)(iph+1);
  78         int  l = iph->ihl*4 - sizeof(struct iphdr);
  79         int  optlen;
  80
  81         while (l > 0) {
  82                 switch (*optptr) {
  83                 case IPOPT_END:
  84                         return 0;
  85                 case IPOPT_NOOP:
  86                         l--;
  87                         optptr++;
  88                         continue;
  89                 }
  90                 optlen = optptr[1];
  91                 if (optlen<2 || optlen>l)
  92                         return -EINVAL;
  93                 switch (*optptr) {
  94                 case IPOPT_SEC:
  95                 case 0x85:      /* Some "Extended Security" crap. */
  96                 case IPOPT_CIPSO:
  97                 case IPOPT_RA:
  98                 case 0x80|21:   /* RFC1770 */
  99                         break;
 100                 case IPOPT_LSRR:
 101                 case IPOPT_SSRR:
 102                         if (optlen < 6)
 103                                 return -EINVAL;
 104                         memcpy(daddr, optptr+optlen-4, 4);
 105                         /* Fall through */
 106                 default:
 107                         memset(optptr, 0, optlen);
 108                 }
 109                 l -= optlen;
 110                 optptr += optlen;
 111         }
 112         return 0;
 113 }
 114
 115 static void ah_output_done(struct crypto_async_request *base, int err)
 116 {
 117         u8 *icv;
 118         struct iphdr *iph;
 119         struct sk_buff *skb = base->data;
 120         struct xfrm_state *x = skb_dst(skb)->xfrm;
 121         struct ah_data *ahp = x->data;
 122         struct iphdr *top_iph = ip_hdr(skb);
 123         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 124         int ihl = ip_hdrlen(skb);
 125
 126         iph = AH_SKB_CB(skb)->tmp;
 127         icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 128         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 129
 130         top_iph->tos = iph->tos;
 131         top_iph->ttl = iph->ttl;
 132         top_iph->frag_off = iph->frag_off;
 133         if (top_iph->ihl != 5) {
 134                 top_iph->daddr = iph->daddr;
 135                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 136         }
 137
 138         err = ah->nexthdr;
 139
 140         kfree(AH_SKB_CB(skb)->tmp);
 141         xfrm_output_resume(skb, err);
 142 }
 143
 144 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 145 {
 146         int err;
 147         int nfrags;
 148         int ihl;
 149         u8 *icv;
 150         struct sk_buff *trailer;
 151         struct crypto_ahash *ahash;
 152         struct ahash_request *req;
 153         struct scatterlist *sg;
 154         struct iphdr *iph, *top_iph;
 155         struct ip_auth_hdr *ah;
 156         struct ah_data *ahp;
 157
 158         ahp = x->data;
 159         ahash = ahp->ahash;
 160
 161         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 162                 goto out;
 163         nfrags = err;
 164
 165         skb_push(skb, -skb_network_offset(skb));
 166         ah = ip_auth_hdr(skb);
 167         ihl = ip_hdrlen(skb);
 168
 169         err = -ENOMEM;
 170         iph = ah_alloc_tmp(ahash, nfrags, ihl);
 171         if (!iph)
 172                 goto out;
 173
 174         icv = ah_tmp_icv(ahash, iph, ihl);
 175         req = ah_tmp_req(ahash, icv);
 176         sg = ah_req_sg(ahash, req);
 177
 178         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 179
 180         top_iph = ip_hdr(skb);
 181
 182         iph->tos = top_iph->tos;
 183         iph->ttl = top_iph->ttl;
 184         iph->frag_off = top_iph->frag_off;
 185
 186         if (top_iph->ihl != 5) {
 187                 iph->daddr = top_iph->daddr;
 188                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 189                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 190                 if (err)
 191                         goto out_free;
 192         }
 193
 194         ah->nexthdr = *skb_mac_header(skb);
 195         *skb_mac_header(skb) = IPPROTO_AH;
 196
 197         top_iph->tos = 0;
 198         top_iph->tot_len = htons(skb->len);
 199         top_iph->frag_off = 0;
 200         top_iph->ttl = 0;
 201         top_iph->check = 0;
 202
 203         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 204
 205         ah->reserved = 0;
 206         ah->spi = x->id.spi;
 207         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
 208
 209         sg_init_table(sg, nfrags);
 210         skb_to_sgvec(skb, sg, 0, skb->len);
 211
 212         ahash_request_set_crypt(req, sg, icv, skb->len);
 213         ahash_request_set_callback(req, 0, ah_output_done, skb);
 214
 215         AH_SKB_CB(skb)->tmp = iph;
 216
 217         err = crypto_ahash_digest(req);
 218         if (err) {
 219                 if (err == -EINPROGRESS)
 220                         goto out;
 221
 222                 if (err == -EBUSY)
 223                         err = NET_XMIT_DROP;
 224                 goto out_free;
 225         }
 226
 227         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 228
 229         top_iph->tos = iph->tos;
 230         top_iph->ttl = iph->ttl;
 231         top_iph->frag_off = iph->frag_off;
 232         if (top_iph->ihl != 5) {
 233                 top_iph->daddr = iph->daddr;
 234                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 235         }
 236
 237 out_free:
 238         kfree(iph);
 239 out:
 240         return err;
 241 }
 242
 243 static void ah_input_done(struct crypto_async_request *base, int err)
 244 {
 245         u8 *auth_data;
 246         u8 *icv;
 247         struct iphdr *work_iph;
 248         struct sk_buff *skb = base->data;
 249         struct xfrm_state *x = xfrm_input_state(skb);
 250         struct ah_data *ahp = x->data;
 251         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 252         int ihl = ip_hdrlen(skb);
 253         int ah_hlen = (ah->hdrlen + 2) << 2;
 254
 255         work_iph = AH_SKB_CB(skb)->tmp;
 256         auth_data = ah_tmp_auth(work_iph, ihl);
 257         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 258
 259         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 260         if (err)
 261                 goto out;
 262
 263         skb->network_header += ah_hlen;
 264         memcpy(skb_network_header(skb), work_iph, ihl);
 265         __skb_pull(skb, ah_hlen + ihl);
 266         skb_set_transport_header(skb, -ihl);
 267
 268         err = ah->nexthdr;
 269 out:
 270         kfree(AH_SKB_CB(skb)->tmp);
 271         xfrm_input_resume(skb, err);
 272 }
 273
 274 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 275 {
 276         int ah_hlen;
 277         int ihl;
 278         int nexthdr;
 279         int nfrags;
 280         u8 *auth_data;
 281         u8 *icv;
 282         struct sk_buff *trailer;
 283         struct crypto_ahash *ahash;
 284         struct ahash_request *req;
 285         struct scatterlist *sg;
 286         struct iphdr *iph, *work_iph;
 287         struct ip_auth_hdr *ah;
 288         struct ah_data *ahp;
 289         int err = -ENOMEM;
 290
 291         if (!pskb_may_pull(skb, sizeof(*ah)))
 292                 goto out;
 293
 294         ah = (struct ip_auth_hdr *)skb->data;
 295         ahp = x->data;
 296         ahash = ahp->ahash;
 297
 298         nexthdr = ah->nexthdr;
 299         ah_hlen = (ah->hdrlen + 2) << 2;
 300
 301         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 302             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 303                 goto out;
 304
 305         if (!pskb_may_pull(skb, ah_hlen))
 306                 goto out;
 307
 308         /* We are going to _remove_ AH header to keep sockets happy,
 309          * so... Later this can change. */
 310         if (skb_cloned(skb) &&
 311             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 312                 goto out;
 313
 314         skb->ip_summed = CHECKSUM_NONE;
 315
 316         ah = (struct ip_auth_hdr *)skb->data;
 317         iph = ip_hdr(skb);
 318         ihl = ip_hdrlen(skb);
 319
 320         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 321                 goto out;
 322         nfrags = err;
 323
 324         work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
 325         if (!work_iph)
 326                 goto out;
 327
 328         auth_data = ah_tmp_auth(work_iph, ihl);
 329         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 330         req = ah_tmp_req(ahash, icv);
 331         sg = ah_req_sg(ahash, req);
 332
 333         memcpy(work_iph, iph, ihl);
 334         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 335         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 336
 337         iph->ttl = 0;
 338         iph->tos = 0;
 339         iph->frag_off = 0;
 340         iph->check = 0;
 341         if (ihl > sizeof(*iph)) {
 342                 __be32 dummy;
 343                 err = ip_clear_mutable_options(iph, &dummy);
 344                 if (err)
 345                         goto out_free;
 346         }
 347
 348         skb_push(skb, ihl);
 349
 350         sg_init_table(sg, nfrags);
 351         skb_to_sgvec(skb, sg, 0, skb->len);
 352
 353         ahash_request_set_crypt(req, sg, icv, skb->len);
 354         ahash_request_set_callback(req, 0, ah_input_done, skb);
 355
 356         AH_SKB_CB(skb)->tmp = work_iph;
 357
 358         err = crypto_ahash_digest(req);
 359         if (err) {
 360                 if (err == -EINPROGRESS)
 361                         goto out;
 362
 363                 if (err == -EBUSY)
 364                         err = NET_XMIT_DROP;
 365                 goto out_free;
 366         }
 367
 368         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 369         if (err)
 370                 goto out_free;
 371
 372         skb->network_header += ah_hlen;
 373         memcpy(skb_network_header(skb), work_iph, ihl);
 374         __skb_pull(skb, ah_hlen + ihl);
 375         skb_set_transport_header(skb, -ihl);
 376
 377         err = nexthdr;
 378
 379 out_free:
 380         kfree (work_iph);
 381 out:
 382         return err;
 383 }
 384
 385 static void ah4_err(struct sk_buff *skb, u32 info)
 386 {
 387         struct net *net = dev_net(skb->dev);
 388         struct iphdr *iph = (struct iphdr *)skb->data;
 389         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 390         struct xfrm_state *x;
 391
 392         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 393             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 394                 return;
 395
 396         x = xfrm_state_lookup(net, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
 397         if (!x)
 398                 return;
 399         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 400                ntohl(ah->spi), ntohl(iph->daddr));
 401         xfrm_state_put(x);
 402 }
 403
 404 static int ah_init_state(struct xfrm_state *x)
 405 {
 406         struct ah_data *ahp = NULL;
 407         struct xfrm_algo_desc *aalg_desc;
 408         struct crypto_ahash *ahash;
 409
 410         if (!x->aalg)
 411                 goto error;
 412
 413         if (x->encap)
 414                 goto error;
 415
 416         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 417         if (!ahp)
 418                 return -ENOMEM;
 419
 420         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 421         if (IS_ERR(ahash))
 422                 goto error;
 423
 424         ahp->ahash = ahash;
 425         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 426                                 (x->aalg->alg_key_len + 7) / 8))
 427                 goto error;
 428
 429         /*
 430          * Lookup the algorithm description maintained by xfrm_algo,
 431          * verify crypto transform properties, and store information
 432          * we need for AH processing.  This lookup cannot fail here
 433          * after a successful crypto_alloc_ahash().
 434          */
 435         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 436         BUG_ON(!aalg_desc);
 437
 438         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 439             crypto_ahash_digestsize(ahash)) {
 440                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 441                        x->aalg->alg_name, crypto_ahash_digestsize(ahash),
 442                        aalg_desc->uinfo.auth.icv_fullbits/8);
 443                 goto error;
 444         }
 445
 446         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 447         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 448
 449         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 450
 451         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 452                                           ahp->icv_trunc_len);
 453         if (x->props.mode == XFRM_MODE_TUNNEL)
 454                 x->props.header_len += sizeof(struct iphdr);
 455         x->data = ahp;
 456
 457         return 0;
 458
 459 error:
 460         if (ahp) {
 461                 crypto_free_ahash(ahp->ahash);
 462                 kfree(ahp);
 463         }
 464         return -EINVAL;
 465 }
 466
 467 static void ah_destroy(struct xfrm_state *x)
 468 {
 469         struct ah_data *ahp = x->data;
 470
 471         if (!ahp)
 472                 return;
 473
 474         crypto_free_ahash(ahp->ahash);
 475         kfree(ahp);
 476 }
 477
 478
 479 static const struct xfrm_type ah_type =
 480 {
 481         .description    = "AH4",
 482         .owner          = THIS_MODULE,
 483         .proto          = IPPROTO_AH,
 484         .flags          = XFRM_TYPE_REPLAY_PROT,
 485         .init_state     = ah_init_state,
 486         .destructor     = ah_destroy,
 487         .input          = ah_input,
 488         .output         = ah_output
 489 };
 490
 491 static const struct net_protocol ah4_protocol = {
 492         .handler        =       xfrm4_rcv,
 493         .err_handler    =       ah4_err,
 494         .no_policy      =       1,
 495         .netns_ok       =       1,
 496 };
 497
 498 static int __init ah4_init(void)
 499 {
 500         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 501                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 502                 return -EAGAIN;
 503         }
 504         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 505                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 506                 xfrm_unregister_type(&ah_type, AF_INET);
 507                 return -EAGAIN;
 508         }
 509         return 0;
 510 }
 511
 512 static void __exit ah4_fini(void)
 513 {
 514         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 515                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 516         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 517                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 518 }
 519
 520 module_init(ah4_init);
 521 module_exit(ah4_fini);
 522 MODULE_LICENSE("GPL");
 523 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);