net/ipv4/ah.c

   1 #include <linux/config.h>
   2 #include <linux/module.h>
   3 #include <net/ip.h>
   4 #include <net/xfrm.h>
   5 #include <linux/crypto.h>
   6 #include <linux/pfkeyv2.h>
   7 #include <net/icmp.h>
   8 #include <asm/scatterlist.h>
   9
  10 struct ah_data
  11 {
  12         u8                      *key;
  13         int                     key_len;
  14         u8                      *work_digest;
  15         int                     digest_len;
  16
  17         void                    (*digest)(struct ah_data*,
  18                                           struct sk_buff *skb,
  19                                           u8 *digest);
  20
  21         struct crypto_tfm       *tfm;
  22 };
  23
  24
  25 /* Clear mutable options and find final destination to substitute
  26  * into IP header for digest calculation. Options are already checked
  27  * for validity, so paranoia is not required. */
  28
  29 int ip_clear_mutable_options(struct iphdr *iph, u32 *daddr)
  30 {
  31         unsigned char * optptr = (unsigned char*)(iph+1);
  32         int  l = iph->ihl*4 - 20;
  33         int  optlen;
  34
  35         while (l > 0) {
  36                 switch (*optptr) {
  37                 case IPOPT_END:
  38                         return 0;
  39                 case IPOPT_NOOP:
  40                         l--;
  41                         optptr++;
  42                         continue;
  43                 }
  44                 optlen = optptr[1];
  45                 if (optlen<2 || optlen>l)
  46                         return -EINVAL;
  47                 switch (*optptr) {
  48                 case IPOPT_SEC:
  49                 case 0x85:      /* Some "Extended Security" crap. */
  50                 case 0x86:      /* Another "Commercial Security" crap. */
  51                 case IPOPT_RA:
  52                 case 0x80|21:   /* RFC1770 */
  53                         break;
  54                 case IPOPT_LSRR:
  55                 case IPOPT_SSRR:
  56                         if (optlen < 6)
  57                                 return -EINVAL;
  58                         memcpy(daddr, optptr+optlen-4, 4);
  59                         /* Fall through */
  60                 default:
  61                         memset(optptr+2, 0, optlen-2);
  62                 }
  63                 l -= optlen;
  64                 optptr += optlen;
  65         }
  66         return 0;
  67 }
  68
  69 void skb_ah_walk(const struct sk_buff *skb, struct crypto_tfm *tfm)
  70 {
  71         int offset = 0;
  72         int len = skb->len;
  73         int start = skb->len - skb->data_len;
  74         int i, copy = start - offset;
  75         struct scatterlist sg;
  76
  77         /* Checksum header. */
  78         if (copy > 0) {
  79                 if (copy > len)
  80                         copy = len;
  81
  82                 sg.page = virt_to_page(skb->data + offset);
  83                 sg.offset = (unsigned long)(skb->data + offset) % PAGE_SIZE;
  84                 sg.length = copy;
  85
  86                 crypto_hmac_update(tfm, &sg, 1);
  87
  88                 if ((len -= copy) == 0)
  89                         return;
  90                 offset += copy;
  91         }
  92
  93         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
  94                 int end;
  95
  96                 BUG_TRAP(start <= offset + len);
  97
  98                 end = start + skb_shinfo(skb)->frags[i].size;
  99                 if ((copy = end - offset) > 0) {
 100                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 101
 102                         if (copy > len)
 103                                 copy = len;
 104
 105                         sg.page = frag->page;
 106                         sg.offset = frag->page_offset + offset-start;
 107                         sg.length = copy;
 108
 109                         crypto_hmac_update(tfm, &sg, 1);
 110
 111                         if (!(len -= copy))
 112                                 return;
 113                         offset += copy;
 114                 }
 115                 start = end;
 116         }
 117
 118         if (skb_shinfo(skb)->frag_list) {
 119                 struct sk_buff *list = skb_shinfo(skb)->frag_list;
 120
 121                 for (; list; list = list->next) {
 122                         int end;
 123
 124                         BUG_TRAP(start <= offset + len);
 125
 126                         end = start + list->len;
 127                         if ((copy = end - offset) > 0) {
 128                                 if (copy > len)
 129                                         copy = len;
 130                                 skb_ah_walk(list, tfm);
 131                                 if ((len -= copy) == 0)
 132                                         return;
 133                                 offset += copy;
 134                         }
 135                         start = end;
 136                 }
 137         }
 138         if (len)
 139                 BUG();
 140 }
 141
 142 static void
 143 ah_hmac_digest(struct ah_data *ahp, struct sk_buff *skb, u8 *auth_data)
 144 {
 145         struct crypto_tfm *tfm = ahp->tfm;
 146
 147         memset(auth_data, 0, ahp->digest_len);
 148         crypto_hmac_init(tfm, ahp->key, &ahp->key_len);
 149         skb_ah_walk(skb, tfm);
 150         crypto_hmac_final(tfm, ahp->key, &ahp->key_len, ahp->work_digest);
 151         memcpy(auth_data, ahp->work_digest, ahp->digest_len);
 152 }
 153
 154 int ah_output(struct sk_buff *skb)
 155 {
 156         int err;
 157         struct dst_entry *dst = skb->dst;
 158         struct xfrm_state *x  = dst->xfrm;
 159         struct iphdr *iph, *top_iph;
 160         struct ip_auth_hdr *ah;
 161         struct ah_data *ahp;
 162         union {
 163                 struct iphdr    iph;
 164                 char            buf[60];
 165         } tmp_iph;
 166
 167         if (skb->ip_summed == CHECKSUM_HW && skb_checksum_help(skb) == NULL)
 168                 return -EINVAL;
 169
 170         spin_lock_bh(&x->lock);
 171         if ((err = xfrm_state_check_expire(x)) != 0)
 172                 goto error;
 173         if ((err = xfrm_state_check_space(x, skb)) != 0)
 174                 goto error;
 175
 176         iph = skb->nh.iph;
 177         if (x->props.mode) {
 178                 top_iph = (struct iphdr*)skb_push(skb, x->props.header_len);
 179                 top_iph->ihl = 5;
 180                 top_iph->version = 4;
 181                 top_iph->tos = 0;
 182                 top_iph->tot_len = htons(skb->len);
 183                 top_iph->frag_off = 0;
 184                 if (!(iph->frag_off&htons(IP_DF)))
 185                         __ip_select_ident(top_iph, dst, 0);
 186                 top_iph->ttl = 0;
 187                 top_iph->protocol = IPPROTO_AH;
 188                 top_iph->check = 0;
 189                 top_iph->saddr = x->props.saddr.xfrm4_addr;
 190                 top_iph->daddr = x->id.daddr.xfrm4_addr;
 191                 ah = (struct ip_auth_hdr*)(top_iph+1);
 192                 ah->nexthdr = IPPROTO_IPIP;
 193         } else {
 194                 memcpy(&tmp_iph, skb->data, iph->ihl*4);
 195                 top_iph = (struct iphdr*)skb_push(skb, x->props.header_len);
 196                 memcpy(top_iph, &tmp_iph, iph->ihl*4);
 197                 iph = &tmp_iph.iph;
 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->protocol = IPPROTO_AH;
 203                 top_iph->check = 0;
 204                 if (top_iph->ihl != 5) {
 205                         err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 206                         if (err)
 207                                 goto error;
 208                 }
 209                 ah = (struct ip_auth_hdr*)((char*)top_iph+iph->ihl*4);
 210                 ah->nexthdr = iph->protocol;
 211         }
 212         ahp = x->data;
 213         ah->hdrlen  = (((ahp->digest_len + 12 + 7)&~7)>>2)-2;
 214         ah->reserved = 0;
 215         ah->spi = x->id.spi;
 216         ah->seq_no = htonl(++x->replay.oseq);
 217         ahp->digest(ahp, skb, ah->auth_data);
 218         top_iph->tos = iph->tos;
 219         top_iph->ttl = iph->ttl;
 220         if (x->props.mode) {
 221                 top_iph->frag_off = iph->frag_off&~htons(IP_MF|IP_OFFSET);
 222                 memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
 223         } else {
 224                 top_iph->frag_off = iph->frag_off;
 225                 top_iph->daddr = iph->daddr;
 226                 if (iph->ihl != 5)
 227                         memcpy(top_iph+1, iph+1, iph->ihl*5 - 20);
 228         }
 229         ip_send_check(top_iph);
 230
 231         skb->nh.raw = skb->data;
 232
 233         x->curlft.bytes += skb->len;
 234         x->curlft.packets++;
 235         spin_unlock_bh(&x->lock);
 236         if ((skb->dst = dst_pop(dst)) == NULL)
 237                 goto error;
 238         return NET_XMIT_BYPASS;
 239
 240 error:
 241         spin_unlock_bh(&x->lock);
 242         kfree_skb(skb);
 243         return err;
 244 }
 245
 246 int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 247 {
 248         struct iphdr *iph;
 249         struct ip_auth_hdr *ah;
 250         struct ah_data *ahp;
 251         char work_buf[60];
 252
 253         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 254                 goto out;
 255
 256         ah = (struct ip_auth_hdr*)skb->data;
 257
 258         ahp = x->data;
 259
 260         if (((ah->hdrlen+2)<<2) != ((ahp->digest_len + 12 + 7)&~7))
 261                 goto out;
 262
 263         if (!pskb_may_pull(skb, (ah->hdrlen+2)<<2))
 264                 goto out;
 265
 266         /* We are going to _remove_ AH header to keep sockets happy,
 267          * so... Later this can change. */
 268         if (skb_cloned(skb) &&
 269             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 270                 goto out;
 271
 272         ah = (struct ip_auth_hdr*)skb->data;
 273         iph = skb->nh.iph;
 274
 275         memcpy(work_buf, iph, iph->ihl*4);
 276
 277         iph->ttl = 0;
 278         iph->tos = 0;
 279         iph->frag_off = 0;
 280         iph->check = 0;
 281         if (iph->ihl != 5) {
 282                 u32 dummy;
 283                 if (ip_clear_mutable_options(iph, &dummy))
 284                         goto out;
 285         }
 286         {
 287                 u8 auth_data[ahp->digest_len];
 288                 memcpy(auth_data, ah->auth_data, ahp->digest_len);
 289                 skb_push(skb, skb->data - skb->nh.raw);
 290                 ahp->digest(ahp, skb, ah->auth_data);
 291                 if (memcmp(ah->auth_data, auth_data, ahp->digest_len)) {
 292                         x->stats.integrity_failed++;
 293                         goto out;
 294                 }
 295         }
 296         ((struct iphdr*)work_buf)->protocol = ah->nexthdr;
 297         skb->nh.raw = skb_pull(skb, (ah->hdrlen+2)<<2);
 298         memcpy(skb->nh.raw, work_buf, iph->ihl*4);
 299         skb->nh.iph->tot_len = htons(skb->len);
 300         skb_pull(skb, skb->nh.iph->ihl*4);
 301         skb->h.raw = skb->data;
 302
 303         return 0;
 304
 305 out:
 306         return -EINVAL;
 307 }
 308
 309 void ah4_err(struct sk_buff *skb, u32 info)
 310 {
 311         struct iphdr *iph = (struct iphdr*)skb->data;
 312         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
 313         struct xfrm_state *x;
 314
 315         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 316             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 317                 return;
 318
 319         x = xfrm_state_lookup(iph->daddr, ah->spi, IPPROTO_AH);
 320         if (!x)
 321                 return;
 322         printk(KERN_DEBUG "pmtu discvovery on SA AH/%08x/%08x\n",
 323                ntohl(ah->spi), ntohl(iph->daddr));
 324         xfrm_state_put(x);
 325 }
 326
 327 int ah_init_state(struct xfrm_state *x, void *args)
 328 {
 329         struct ah_data *ahp = NULL;
 330
 331         if (x->aalg == NULL || x->aalg->alg_key_len == 0 ||
 332             x->aalg->alg_key_len > 512)
 333                 goto error;
 334
 335         ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
 336         if (ahp == NULL)
 337                 return -ENOMEM;
 338
 339         memset(ahp, 0, sizeof(*ahp));
 340
 341         ahp->key = x->aalg->alg_key;
 342         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 343         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 344         if (!ahp->tfm)
 345                 goto error;
 346         ahp->digest = ah_hmac_digest;
 347         ahp->digest_len = 12;
 348         ahp->work_digest = kmalloc(crypto_tfm_alg_digestsize(ahp->tfm),
 349                                    GFP_KERNEL);
 350         if (!ahp->work_digest)
 351                 goto error;
 352         x->props.header_len = (12 + ahp->digest_len + 7)&~7;
 353         if (x->props.mode)
 354                 x->props.header_len += 20;
 355         x->data = ahp;
 356
 357         return 0;
 358
 359 error:
 360         if (ahp) {
 361                 if (ahp->work_digest)
 362                         kfree(ahp->work_digest);
 363                 if (ahp->tfm)
 364                         crypto_free_tfm(ahp->tfm);
 365                 kfree(ahp);
 366         }
 367         return -EINVAL;
 368 }
 369
 370 void ah_destroy(struct xfrm_state *x)
 371 {
 372         struct ah_data *ahp = x->data;
 373
 374         if (ahp->work_digest) {
 375                 kfree(ahp->work_digest);
 376                 ahp->work_digest = NULL;
 377         }
 378         if (ahp->tfm) {
 379                 crypto_free_tfm(ahp->tfm);
 380                 ahp->tfm = NULL;
 381         }
 382 }
 383
 384
 385 static struct xfrm_type ah_type =
 386 {
 387         .description    = "AH4",
 388         .proto          = IPPROTO_AH,
 389         .init_state     = ah_init_state,
 390         .destructor     = ah_destroy,
 391         .input          = ah_input,
 392         .output         = ah_output
 393 };
 394
 395 static struct inet_protocol ah4_protocol = {
 396         .handler        =       xfrm4_rcv,
 397         .err_handler    =       ah4_err,
 398         .no_policy      =       1,
 399 };
 400
 401 int __init ah4_init(void)
 402 {
 403         SET_MODULE_OWNER(&ah_type);
 404         if (xfrm_register_type(&ah_type) < 0) {
 405                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 406                 return -EAGAIN;
 407         }
 408         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 409                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 410                 xfrm_unregister_type(&ah_type);
 411                 return -EAGAIN;
 412         }
 413         return 0;
 414 }
 415
 416 static void __exit ah4_fini(void)
 417 {
 418         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 419                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 420         if (xfrm_unregister_type(&ah_type) < 0)
 421                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 422 }
 423
 424 module_init(ah4_init);
 425 module_exit(ah4_fini);
 426 MODULE_LICENSE("GPL");