net/ipv4/ah4.c

   1 #include <crypto/hash.h>
   2 #include <linux/err.h>
   3 #include <linux/module.h>
   4 #include <linux/slab.h>
   5 #include <net/ip.h>
   6 #include <net/xfrm.h>
   7 #include <net/ah.h>
   8 #include <linux/crypto.h>
   9 #include <linux/pfkeyv2.h>
  10 #include <linux/scatterlist.h>
  11 #include <net/icmp.h>
  12 #include <net/protocol.h>
  13
  14 struct ah_skb_cb {
  15         struct xfrm_skb_cb xfrm;
  16         void *tmp;
  17 };
  18
  19 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
  20
  21 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
  22                           unsigned int size)
  23 {
  24         unsigned int len;
  25
  26         len = size + crypto_ahash_digestsize(ahash) +
  27               (crypto_ahash_alignmask(ahash) &
  28                ~(crypto_tfm_ctx_alignment() - 1));
  29
  30         len = ALIGN(len, crypto_tfm_ctx_alignment());
  31
  32         len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
  33         len = ALIGN(len, __alignof__(struct scatterlist));
  34
  35         len += sizeof(struct scatterlist) * nfrags;
  36
  37         return kmalloc(len, GFP_ATOMIC);
  38 }
  39
  40 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
  41 {
  42         return tmp + offset;
  43 }
  44
  45 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
  46                              unsigned int offset)
  47 {
  48         return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
  49 }
  50
  51 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
  52                                                u8 *icv)
  53 {
  54         struct ahash_request *req;
  55
  56         req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
  57                                 crypto_tfm_ctx_alignment());
  58
  59         ahash_request_set_tfm(req, ahash);
  60
  61         return req;
  62 }
  63
  64 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
  65                                              struct ahash_request *req)
  66 {
  67         return (void *)ALIGN((unsigned long)(req + 1) +
  68                              crypto_ahash_reqsize(ahash),
  69                              __alignof__(struct scatterlist));
  70 }
  71
  72 /* Clear mutable options and find final destination to substitute
  73  * into IP header for icv calculation. Options are already checked
  74  * for validity, so paranoia is not required. */
  75
  76 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
  77 {
  78         unsigned char * optptr = (unsigned char*)(iph+1);
  79         int  l = iph->ihl*4 - sizeof(struct iphdr);
  80         int  optlen;
  81
  82         while (l > 0) {
  83                 switch (*optptr) {
  84                 case IPOPT_END:
  85                         return 0;
  86                 case IPOPT_NOOP:
  87                         l--;
  88                         optptr++;
  89                         continue;
  90                 }
  91                 optlen = optptr[1];
  92                 if (optlen<2 || optlen>l)
  93                         return -EINVAL;
  94                 switch (*optptr) {
  95                 case IPOPT_SEC:
  96                 case 0x85:      /* Some "Extended Security" crap. */
  97                 case IPOPT_CIPSO:
  98                 case IPOPT_RA:
  99                 case 0x80|21:   /* RFC1770 */
 100                         break;
 101                 case IPOPT_LSRR:
 102                 case IPOPT_SSRR:
 103                         if (optlen < 6)
 104                                 return -EINVAL;
 105                         memcpy(daddr, optptr+optlen-4, 4);
 106                         /* Fall through */
 107                 default:
 108                         memset(optptr, 0, optlen);
 109                 }
 110                 l -= optlen;
 111                 optptr += optlen;
 112         }
 113         return 0;
 114 }
 115
 116 static void ah_output_done(struct crypto_async_request *base, int err)
 117 {
 118         u8 *icv;
 119         struct iphdr *iph;
 120         struct sk_buff *skb = base->data;
 121         struct xfrm_state *x = skb_dst(skb)->xfrm;
 122         struct ah_data *ahp = x->data;
 123         struct iphdr *top_iph = ip_hdr(skb);
 124         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 125         int ihl = ip_hdrlen(skb);
 126
 127         iph = AH_SKB_CB(skb)->tmp;
 128         icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 129         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 130
 131         top_iph->tos = iph->tos;
 132         top_iph->ttl = iph->ttl;
 133         top_iph->frag_off = iph->frag_off;
 134         if (top_iph->ihl != 5) {
 135                 top_iph->daddr = iph->daddr;
 136                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 137         }
 138
 139         kfree(AH_SKB_CB(skb)->tmp);
 140         xfrm_output_resume(skb, err);
 141 }
 142
 143 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 144 {
 145         int err;
 146         int nfrags;
 147         int ihl;
 148         u8 *icv;
 149         struct sk_buff *trailer;
 150         struct crypto_ahash *ahash;
 151         struct ahash_request *req;
 152         struct scatterlist *sg;
 153         struct iphdr *iph, *top_iph;
 154         struct ip_auth_hdr *ah;
 155         struct ah_data *ahp;
 156
 157         ahp = x->data;
 158         ahash = ahp->ahash;
 159
 160         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 161                 goto out;
 162         nfrags = err;
 163
 164         skb_push(skb, -skb_network_offset(skb));
 165         ah = ip_auth_hdr(skb);
 166         ihl = ip_hdrlen(skb);
 167
 168         err = -ENOMEM;
 169         iph = ah_alloc_tmp(ahash, nfrags, ihl);
 170         if (!iph)
 171                 goto out;
 172
 173         icv = ah_tmp_icv(ahash, iph, ihl);
 174         req = ah_tmp_req(ahash, icv);
 175         sg = ah_req_sg(ahash, req);
 176
 177         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 178
 179         top_iph = ip_hdr(skb);
 180
 181         iph->tos = top_iph->tos;
 182         iph->ttl = top_iph->ttl;
 183         iph->frag_off = top_iph->frag_off;
 184
 185         if (top_iph->ihl != 5) {
 186                 iph->daddr = top_iph->daddr;
 187                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 188                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 189                 if (err)
 190                         goto out_free;
 191         }
 192
 193         ah->nexthdr = *skb_mac_header(skb);
 194         *skb_mac_header(skb) = IPPROTO_AH;
 195
 196         top_iph->tos = 0;
 197         top_iph->tot_len = htons(skb->len);
 198         top_iph->frag_off = 0;
 199         top_iph->ttl = 0;
 200         top_iph->check = 0;
 201
 202         if (x->props.flags & XFRM_STATE_ALIGN4)
 203                 ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 204         else
 205                 ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 206
 207         ah->reserved = 0;
 208         ah->spi = x->id.spi;
 209         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
 210
 211         sg_init_table(sg, nfrags);
 212         skb_to_sgvec(skb, sg, 0, skb->len);
 213
 214         ahash_request_set_crypt(req, sg, icv, skb->len);
 215         ahash_request_set_callback(req, 0, ah_output_done, skb);
 216
 217         AH_SKB_CB(skb)->tmp = iph;
 218
 219         err = crypto_ahash_digest(req);
 220         if (err) {
 221                 if (err == -EINPROGRESS)
 222                         goto out;
 223
 224                 if (err == -EBUSY)
 225                         err = NET_XMIT_DROP;
 226                 goto out_free;
 227         }
 228
 229         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 230
 231         top_iph->tos = iph->tos;
 232         top_iph->ttl = iph->ttl;
 233         top_iph->frag_off = iph->frag_off;
 234         if (top_iph->ihl != 5) {
 235                 top_iph->daddr = iph->daddr;
 236                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 237         }
 238
 239 out_free:
 240         kfree(iph);
 241 out:
 242         return err;
 243 }
 244
 245 static void ah_input_done(struct crypto_async_request *base, int err)
 246 {
 247         u8 *auth_data;
 248         u8 *icv;
 249         struct iphdr *work_iph;
 250         struct sk_buff *skb = base->data;
 251         struct xfrm_state *x = xfrm_input_state(skb);
 252         struct ah_data *ahp = x->data;
 253         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 254         int ihl = ip_hdrlen(skb);
 255         int ah_hlen = (ah->hdrlen + 2) << 2;
 256
 257         work_iph = AH_SKB_CB(skb)->tmp;
 258         auth_data = ah_tmp_auth(work_iph, ihl);
 259         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 260
 261         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 262         if (err)
 263                 goto out;
 264
 265         err = ah->nexthdr;
 266
 267         skb->network_header += ah_hlen;
 268         memcpy(skb_network_header(skb), work_iph, ihl);
 269         __skb_pull(skb, ah_hlen + ihl);
 270         skb_set_transport_header(skb, -ihl);
 271 out:
 272         kfree(AH_SKB_CB(skb)->tmp);
 273         xfrm_input_resume(skb, err);
 274 }
 275
 276 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 277 {
 278         int ah_hlen;
 279         int ihl;
 280         int nexthdr;
 281         int nfrags;
 282         u8 *auth_data;
 283         u8 *icv;
 284         struct sk_buff *trailer;
 285         struct crypto_ahash *ahash;
 286         struct ahash_request *req;
 287         struct scatterlist *sg;
 288         struct iphdr *iph, *work_iph;
 289         struct ip_auth_hdr *ah;
 290         struct ah_data *ahp;
 291         int err = -ENOMEM;
 292
 293         if (!pskb_may_pull(skb, sizeof(*ah)))
 294                 goto out;
 295
 296         ah = (struct ip_auth_hdr *)skb->data;
 297         ahp = x->data;
 298         ahash = ahp->ahash;
 299
 300         nexthdr = ah->nexthdr;
 301         ah_hlen = (ah->hdrlen + 2) << 2;
 302
 303         if (x->props.flags & XFRM_STATE_ALIGN4) {
 304                 if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 305                     ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 306                         goto out;
 307         } else {
 308                 if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 309                     ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 310                         goto out;
 311         }
 312
 313         if (!pskb_may_pull(skb, ah_hlen))
 314                 goto out;
 315
 316         /* We are going to _remove_ AH header to keep sockets happy,
 317          * so... Later this can change. */
 318         if (skb_cloned(skb) &&
 319             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 320                 goto out;
 321
 322         skb->ip_summed = CHECKSUM_NONE;
 323
 324
 325         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 326                 goto out;
 327         nfrags = err;
 328
 329         ah = (struct ip_auth_hdr *)skb->data;
 330         iph = ip_hdr(skb);
 331         ihl = ip_hdrlen(skb);
 332
 333         work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
 334         if (!work_iph)
 335                 goto out;
 336
 337         auth_data = ah_tmp_auth(work_iph, ihl);
 338         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 339         req = ah_tmp_req(ahash, icv);
 340         sg = ah_req_sg(ahash, req);
 341
 342         memcpy(work_iph, iph, ihl);
 343         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 344         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 345
 346         iph->ttl = 0;
 347         iph->tos = 0;
 348         iph->frag_off = 0;
 349         iph->check = 0;
 350         if (ihl > sizeof(*iph)) {
 351                 __be32 dummy;
 352                 err = ip_clear_mutable_options(iph, &dummy);
 353                 if (err)
 354                         goto out_free;
 355         }
 356
 357         skb_push(skb, ihl);
 358
 359         sg_init_table(sg, nfrags);
 360         skb_to_sgvec(skb, sg, 0, skb->len);
 361
 362         ahash_request_set_crypt(req, sg, icv, skb->len);
 363         ahash_request_set_callback(req, 0, ah_input_done, skb);
 364
 365         AH_SKB_CB(skb)->tmp = work_iph;
 366
 367         err = crypto_ahash_digest(req);
 368         if (err) {
 369                 if (err == -EINPROGRESS)
 370                         goto out;
 371
 372                 goto out_free;
 373         }
 374
 375         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 376         if (err)
 377                 goto out_free;
 378
 379         skb->network_header += ah_hlen;
 380         memcpy(skb_network_header(skb), work_iph, ihl);
 381         __skb_pull(skb, ah_hlen + ihl);
 382         skb_set_transport_header(skb, -ihl);
 383
 384         err = nexthdr;
 385
 386 out_free:
 387         kfree (work_iph);
 388 out:
 389         return err;
 390 }
 391
 392 static void ah4_err(struct sk_buff *skb, u32 info)
 393 {
 394         struct net *net = dev_net(skb->dev);
 395         const struct iphdr *iph = (const struct iphdr *)skb->data;
 396         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 397         struct xfrm_state *x;
 398
 399         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 400             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 401                 return;
 402
 403         x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
 404                               ah->spi, IPPROTO_AH, AF_INET);
 405         if (!x)
 406                 return;
 407         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 408                ntohl(ah->spi), ntohl(iph->daddr));
 409         xfrm_state_put(x);
 410 }
 411
 412 static int ah_init_state(struct xfrm_state *x)
 413 {
 414         struct ah_data *ahp = NULL;
 415         struct xfrm_algo_desc *aalg_desc;
 416         struct crypto_ahash *ahash;
 417
 418         if (!x->aalg)
 419                 goto error;
 420
 421         if (x->encap)
 422                 goto error;
 423
 424         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 425         if (!ahp)
 426                 return -ENOMEM;
 427
 428         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 429         if (IS_ERR(ahash))
 430                 goto error;
 431
 432         ahp->ahash = ahash;
 433         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 434                                 (x->aalg->alg_key_len + 7) / 8))
 435                 goto error;
 436
 437         /*
 438          * Lookup the algorithm description maintained by xfrm_algo,
 439          * verify crypto transform properties, and store information
 440          * we need for AH processing.  This lookup cannot fail here
 441          * after a successful crypto_alloc_ahash().
 442          */
 443         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 444         BUG_ON(!aalg_desc);
 445
 446         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 447             crypto_ahash_digestsize(ahash)) {
 448                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 449                        x->aalg->alg_name, crypto_ahash_digestsize(ahash),
 450                        aalg_desc->uinfo.auth.icv_fullbits/8);
 451                 goto error;
 452         }
 453
 454         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 455         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 456
 457         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 458
 459         if (x->props.flags & XFRM_STATE_ALIGN4)
 460                 x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 461                                                   ahp->icv_trunc_len);
 462         else
 463                 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 464                                                   ahp->icv_trunc_len);
 465         if (x->props.mode == XFRM_MODE_TUNNEL)
 466                 x->props.header_len += sizeof(struct iphdr);
 467         x->data = ahp;
 468
 469         return 0;
 470
 471 error:
 472         if (ahp) {
 473                 crypto_free_ahash(ahp->ahash);
 474                 kfree(ahp);
 475         }
 476         return -EINVAL;
 477 }
 478
 479 static void ah_destroy(struct xfrm_state *x)
 480 {
 481         struct ah_data *ahp = x->data;
 482
 483         if (!ahp)
 484                 return;
 485
 486         crypto_free_ahash(ahp->ahash);
 487         kfree(ahp);
 488 }
 489
 490
 491 static const struct xfrm_type ah_type =
 492 {
 493         .description    = "AH4",
 494         .owner          = THIS_MODULE,
 495         .proto          = IPPROTO_AH,
 496         .flags          = XFRM_TYPE_REPLAY_PROT,
 497         .init_state     = ah_init_state,
 498         .destructor     = ah_destroy,
 499         .input          = ah_input,
 500         .output         = ah_output
 501 };
 502
 503 static const struct net_protocol ah4_protocol = {
 504         .handler        =       xfrm4_rcv,
 505         .err_handler    =       ah4_err,
 506         .no_policy      =       1,
 507         .netns_ok       =       1,
 508 };
 509
 510 static int __init ah4_init(void)
 511 {
 512         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 513                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 514                 return -EAGAIN;
 515         }
 516         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 517                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 518                 xfrm_unregister_type(&ah_type, AF_INET);
 519                 return -EAGAIN;
 520         }
 521         return 0;
 522 }
 523
 524 static void __exit ah4_fini(void)
 525 {
 526         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 527                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 528         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 529                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 530 }
 531
 532 module_init(ah4_init);
 533 module_exit(ah4_fini);
 534 MODULE_LICENSE("GPL");
 535 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);