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(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         err = ah->nexthdr;
 140
 141         kfree(AH_SKB_CB(skb)->tmp);
 142         xfrm_output_resume(skb, err);
 143 }
 144
 145 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 146 {
 147         int err;
 148         int nfrags;
 149         int ihl;
 150         u8 *icv;
 151         struct sk_buff *trailer;
 152         struct crypto_ahash *ahash;
 153         struct ahash_request *req;
 154         struct scatterlist *sg;
 155         struct iphdr *iph, *top_iph;
 156         struct ip_auth_hdr *ah;
 157         struct ah_data *ahp;
 158
 159         ahp = x->data;
 160         ahash = ahp->ahash;
 161
 162         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 163                 goto out;
 164         nfrags = err;
 165
 166         skb_push(skb, -skb_network_offset(skb));
 167         ah = ip_auth_hdr(skb);
 168         ihl = ip_hdrlen(skb);
 169
 170         err = -ENOMEM;
 171         iph = ah_alloc_tmp(ahash, nfrags, ihl);
 172         if (!iph)
 173                 goto out;
 174
 175         icv = ah_tmp_icv(ahash, iph, ihl);
 176         req = ah_tmp_req(ahash, icv);
 177         sg = ah_req_sg(ahash, req);
 178
 179         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 180
 181         top_iph = ip_hdr(skb);
 182
 183         iph->tos = top_iph->tos;
 184         iph->ttl = top_iph->ttl;
 185         iph->frag_off = top_iph->frag_off;
 186
 187         if (top_iph->ihl != 5) {
 188                 iph->daddr = top_iph->daddr;
 189                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 190                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 191                 if (err)
 192                         goto out_free;
 193         }
 194
 195         ah->nexthdr = *skb_mac_header(skb);
 196         *skb_mac_header(skb) = IPPROTO_AH;
 197
 198         top_iph->tos = 0;
 199         top_iph->tot_len = htons(skb->len);
 200         top_iph->frag_off = 0;
 201         top_iph->ttl = 0;
 202         top_iph->check = 0;
 203
 204         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 205
 206         ah->reserved = 0;
 207         ah->spi = x->id.spi;
 208         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
 209
 210         sg_init_table(sg, nfrags);
 211         skb_to_sgvec(skb, sg, 0, skb->len);
 212
 213         ahash_request_set_crypt(req, sg, icv, skb->len);
 214         ahash_request_set_callback(req, 0, ah_output_done, skb);
 215
 216         AH_SKB_CB(skb)->tmp = iph;
 217
 218         err = crypto_ahash_digest(req);
 219         if (err) {
 220                 if (err == -EINPROGRESS)
 221                         goto out;
 222
 223                 if (err == -EBUSY)
 224                         err = NET_XMIT_DROP;
 225                 goto out_free;
 226         }
 227
 228         memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
 229
 230         top_iph->tos = iph->tos;
 231         top_iph->ttl = iph->ttl;
 232         top_iph->frag_off = iph->frag_off;
 233         if (top_iph->ihl != 5) {
 234                 top_iph->daddr = iph->daddr;
 235                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 236         }
 237
 238 out_free:
 239         kfree(iph);
 240 out:
 241         return err;
 242 }
 243
 244 static void ah_input_done(struct crypto_async_request *base, int err)
 245 {
 246         u8 *auth_data;
 247         u8 *icv;
 248         struct iphdr *work_iph;
 249         struct sk_buff *skb = base->data;
 250         struct xfrm_state *x = xfrm_input_state(skb);
 251         struct ah_data *ahp = x->data;
 252         struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 253         int ihl = ip_hdrlen(skb);
 254         int ah_hlen = (ah->hdrlen + 2) << 2;
 255
 256         work_iph = AH_SKB_CB(skb)->tmp;
 257         auth_data = ah_tmp_auth(work_iph, ihl);
 258         icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
 259
 260         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 261         if (err)
 262                 goto out;
 263
 264         skb->network_header += ah_hlen;
 265         memcpy(skb_network_header(skb), work_iph, ihl);
 266         __skb_pull(skb, ah_hlen + ihl);
 267         skb_set_transport_header(skb, -ihl);
 268
 269         err = ah->nexthdr;
 270 out:
 271         kfree(AH_SKB_CB(skb)->tmp);
 272         xfrm_input_resume(skb, err);
 273 }
 274
 275 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 276 {
 277         int ah_hlen;
 278         int ihl;
 279         int nexthdr;
 280         int nfrags;
 281         u8 *auth_data;
 282         u8 *icv;
 283         struct sk_buff *trailer;
 284         struct crypto_ahash *ahash;
 285         struct ahash_request *req;
 286         struct scatterlist *sg;
 287         struct iphdr *iph, *work_iph;
 288         struct ip_auth_hdr *ah;
 289         struct ah_data *ahp;
 290         int err = -ENOMEM;
 291
 292         if (!pskb_may_pull(skb, sizeof(*ah)))
 293                 goto out;
 294
 295         ah = (struct ip_auth_hdr *)skb->data;
 296         ahp = x->data;
 297         ahash = ahp->ahash;
 298
 299         nexthdr = ah->nexthdr;
 300         ah_hlen = (ah->hdrlen + 2) << 2;
 301
 302         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 303             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 304                 goto out;
 305
 306         if (!pskb_may_pull(skb, ah_hlen))
 307                 goto out;
 308
 309         /* We are going to _remove_ AH header to keep sockets happy,
 310          * so... Later this can change. */
 311         if (skb_cloned(skb) &&
 312             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 313                 goto out;
 314
 315         skb->ip_summed = CHECKSUM_NONE;
 316
 317         ah = (struct ip_auth_hdr *)skb->data;
 318         iph = ip_hdr(skb);
 319         ihl = ip_hdrlen(skb);
 320
 321         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
 322                 goto out;
 323         nfrags = err;
 324
 325         work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
 326         if (!work_iph)
 327                 goto out;
 328
 329         auth_data = ah_tmp_auth(work_iph, ihl);
 330         icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 331         req = ah_tmp_req(ahash, icv);
 332         sg = ah_req_sg(ahash, req);
 333
 334         memcpy(work_iph, iph, ihl);
 335         memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 336         memset(ah->auth_data, 0, ahp->icv_trunc_len);
 337
 338         iph->ttl = 0;
 339         iph->tos = 0;
 340         iph->frag_off = 0;
 341         iph->check = 0;
 342         if (ihl > sizeof(*iph)) {
 343                 __be32 dummy;
 344                 err = ip_clear_mutable_options(iph, &dummy);
 345                 if (err)
 346                         goto out_free;
 347         }
 348
 349         skb_push(skb, ihl);
 350
 351         sg_init_table(sg, nfrags);
 352         skb_to_sgvec(skb, sg, 0, skb->len);
 353
 354         ahash_request_set_crypt(req, sg, icv, skb->len);
 355         ahash_request_set_callback(req, 0, ah_input_done, skb);
 356
 357         AH_SKB_CB(skb)->tmp = work_iph;
 358
 359         err = crypto_ahash_digest(req);
 360         if (err) {
 361                 if (err == -EINPROGRESS)
 362                         goto out;
 363
 364                 if (err == -EBUSY)
 365                         err = NET_XMIT_DROP;
 366                 goto out_free;
 367         }
 368
 369         err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
 370         if (err)
 371                 goto out_free;
 372
 373         skb->network_header += ah_hlen;
 374         memcpy(skb_network_header(skb), work_iph, ihl);
 375         __skb_pull(skb, ah_hlen + ihl);
 376         skb_set_transport_header(skb, -ihl);
 377
 378         err = nexthdr;
 379
 380 out_free:
 381         kfree (work_iph);
 382 out:
 383         return err;
 384 }
 385
 386 static void ah4_err(struct sk_buff *skb, u32 info)
 387 {
 388         struct net *net = dev_net(skb->dev);
 389         struct iphdr *iph = (struct iphdr *)skb->data;
 390         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
 391         struct xfrm_state *x;
 392
 393         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 394             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 395                 return;
 396
 397         x = xfrm_state_lookup(net, skb->mark, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
 398         if (!x)
 399                 return;
 400         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 401                ntohl(ah->spi), ntohl(iph->daddr));
 402         xfrm_state_put(x);
 403 }
 404
 405 static int ah_init_state(struct xfrm_state *x)
 406 {
 407         struct ah_data *ahp = NULL;
 408         struct xfrm_algo_desc *aalg_desc;
 409         struct crypto_ahash *ahash;
 410
 411         if (!x->aalg)
 412                 goto error;
 413
 414         if (x->encap)
 415                 goto error;
 416
 417         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 418         if (!ahp)
 419                 return -ENOMEM;
 420
 421         ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
 422         if (IS_ERR(ahash))
 423                 goto error;
 424
 425         ahp->ahash = ahash;
 426         if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
 427                                 (x->aalg->alg_key_len + 7) / 8))
 428                 goto error;
 429
 430         /*
 431          * Lookup the algorithm description maintained by xfrm_algo,
 432          * verify crypto transform properties, and store information
 433          * we need for AH processing.  This lookup cannot fail here
 434          * after a successful crypto_alloc_ahash().
 435          */
 436         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 437         BUG_ON(!aalg_desc);
 438
 439         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 440             crypto_ahash_digestsize(ahash)) {
 441                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 442                        x->aalg->alg_name, crypto_ahash_digestsize(ahash),
 443                        aalg_desc->uinfo.auth.icv_fullbits/8);
 444                 goto error;
 445         }
 446
 447         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 448         ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
 449
 450         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 451
 452         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 453                                           ahp->icv_trunc_len);
 454         if (x->props.mode == XFRM_MODE_TUNNEL)
 455                 x->props.header_len += sizeof(struct iphdr);
 456         x->data = ahp;
 457
 458         return 0;
 459
 460 error:
 461         if (ahp) {
 462                 crypto_free_ahash(ahp->ahash);
 463                 kfree(ahp);
 464         }
 465         return -EINVAL;
 466 }
 467
 468 static void ah_destroy(struct xfrm_state *x)
 469 {
 470         struct ah_data *ahp = x->data;
 471
 472         if (!ahp)
 473                 return;
 474
 475         crypto_free_ahash(ahp->ahash);
 476         kfree(ahp);
 477 }
 478
 479
 480 static const struct xfrm_type ah_type =
 481 {
 482         .description    = "AH4",
 483         .owner          = THIS_MODULE,
 484         .proto          = IPPROTO_AH,
 485         .flags          = XFRM_TYPE_REPLAY_PROT,
 486         .init_state     = ah_init_state,
 487         .destructor     = ah_destroy,
 488         .input          = ah_input,
 489         .output         = ah_output
 490 };
 491
 492 static const struct net_protocol ah4_protocol = {
 493         .handler        =       xfrm4_rcv,
 494         .err_handler    =       ah4_err,
 495         .no_policy      =       1,
 496         .netns_ok       =       1,
 497 };
 498
 499 static int __init ah4_init(void)
 500 {
 501         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 502                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 503                 return -EAGAIN;
 504         }
 505         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 506                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 507                 xfrm_unregister_type(&ah_type, AF_INET);
 508                 return -EAGAIN;
 509         }
 510         return 0;
 511 }
 512
 513 static void __exit ah4_fini(void)
 514 {
 515         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 516                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 517         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 518                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 519 }
 520
 521 module_init(ah4_init);
 522 module_exit(ah4_fini);
 523 MODULE_LICENSE("GPL");
 524 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);