net/ipv4/ah4.c

   1 #include <linux/config.h>
   2 #include <linux/module.h>
   3 #include <net/inet_ecn.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 <net/icmp.h>
  10 #include <asm/scatterlist.h>
  11
  12
  13 /* Clear mutable options and find final destination to substitute
  14  * into IP header for icv calculation. Options are already checked
  15  * for validity, so paranoia is not required. */
  16
  17 static int ip_clear_mutable_options(struct iphdr *iph, u32 *daddr)
  18 {
  19         unsigned char * optptr = (unsigned char*)(iph+1);
  20         int  l = iph->ihl*4 - sizeof(struct iphdr);
  21         int  optlen;
  22
  23         while (l > 0) {
  24                 switch (*optptr) {
  25                 case IPOPT_END:
  26                         return 0;
  27                 case IPOPT_NOOP:
  28                         l--;
  29                         optptr++;
  30                         continue;
  31                 }
  32                 optlen = optptr[1];
  33                 if (optlen<2 || optlen>l)
  34                         return -EINVAL;
  35                 switch (*optptr) {
  36                 case IPOPT_SEC:
  37                 case 0x85:      /* Some "Extended Security" crap. */
  38                 case 0x86:      /* Another "Commercial Security" crap. */
  39                 case IPOPT_RA:
  40                 case 0x80|21:   /* RFC1770 */
  41                         break;
  42                 case IPOPT_LSRR:
  43                 case IPOPT_SSRR:
  44                         if (optlen < 6)
  45                                 return -EINVAL;
  46                         memcpy(daddr, optptr+optlen-4, 4);
  47                         /* Fall through */
  48                 default:
  49                         memset(optptr+2, 0, optlen-2);
  50                 }
  51                 l -= optlen;
  52                 optptr += optlen;
  53         }
  54         return 0;
  55 }
  56
  57 static int ah_output(struct sk_buff **pskb)
  58 {
  59         int err;
  60         struct dst_entry *dst = (*pskb)->dst;
  61         struct xfrm_state *x  = dst->xfrm;
  62         struct iphdr *iph, *top_iph;
  63         struct ip_auth_hdr *ah;
  64         struct ah_data *ahp;
  65         union {
  66                 struct iphdr    iph;
  67                 char            buf[60];
  68         } tmp_iph;
  69
  70         if ((*pskb)->ip_summed == CHECKSUM_HW) {
  71                 err = skb_checksum_help(pskb, 0);
  72                 if (err)
  73                         goto error_nolock;
  74         }
  75
  76         spin_lock_bh(&x->lock);
  77         err = xfrm_check_output(x, *pskb, AF_INET);
  78         if (err)
  79                 goto error;
  80
  81         iph = (*pskb)->nh.iph;
  82         if (x->props.mode) {
  83                 top_iph = (struct iphdr*)skb_push(*pskb, x->props.header_len);
  84                 top_iph->ihl = 5;
  85                 top_iph->version = 4;
  86                 top_iph->tos = 0;
  87                 top_iph->tot_len = htons((*pskb)->len);
  88                 top_iph->frag_off = 0;
  89                 if (!(iph->frag_off&htons(IP_DF)))
  90                         __ip_select_ident(top_iph, dst, 0);
  91                 top_iph->ttl = 0;
  92                 top_iph->protocol = IPPROTO_AH;
  93                 top_iph->check = 0;
  94                 top_iph->saddr = x->props.saddr.a4;
  95                 top_iph->daddr = x->id.daddr.a4;
  96                 ah = (struct ip_auth_hdr*)(top_iph+1);
  97                 ah->nexthdr = IPPROTO_IPIP;
  98         } else {
  99                 memcpy(&tmp_iph, (*pskb)->data, iph->ihl*4);
 100                 top_iph = (struct iphdr*)skb_push(*pskb, x->props.header_len);
 101                 memcpy(top_iph, &tmp_iph, iph->ihl*4);
 102                 iph = &tmp_iph.iph;
 103                 top_iph->tos = 0;
 104                 top_iph->tot_len = htons((*pskb)->len);
 105                 top_iph->frag_off = 0;
 106                 top_iph->ttl = 0;
 107                 top_iph->protocol = IPPROTO_AH;
 108                 top_iph->check = 0;
 109                 if (top_iph->ihl != 5) {
 110                         err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 111                         if (err)
 112                                 goto error;
 113                 }
 114                 ah = (struct ip_auth_hdr*)((char*)top_iph+iph->ihl*4);
 115                 ah->nexthdr = iph->protocol;
 116         }
 117         ahp = x->data;
 118         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 119                                    ahp->icv_trunc_len) >> 2) - 2;
 120
 121         ah->reserved = 0;
 122         ah->spi = x->id.spi;
 123         ah->seq_no = htonl(++x->replay.oseq);
 124         ahp->icv(ahp, *pskb, ah->auth_data);
 125         top_iph->tos = iph->tos;
 126         top_iph->ttl = iph->ttl;
 127         if (x->props.mode) {
 128                 if (x->props.flags & XFRM_STATE_NOECN)
 129                         IP_ECN_clear(top_iph);
 130                 top_iph->frag_off = iph->frag_off&~htons(IP_MF|IP_OFFSET);
 131                 memset(&(IPCB(*pskb)->opt), 0, sizeof(struct ip_options));
 132         } else {
 133                 top_iph->frag_off = iph->frag_off;
 134                 top_iph->daddr = iph->daddr;
 135                 if (iph->ihl != 5)
 136                         memcpy(top_iph+1, iph+1, iph->ihl*4 - sizeof(struct iphdr));
 137         }
 138         ip_send_check(top_iph);
 139
 140         (*pskb)->nh.raw = (*pskb)->data;
 141
 142         x->curlft.bytes += (*pskb)->len;
 143         x->curlft.packets++;
 144         spin_unlock_bh(&x->lock);
 145         if (((*pskb)->dst = dst_pop(dst)) == NULL) {
 146                 err = -EHOSTUNREACH;
 147                 goto error_nolock;
 148         }
 149         return NET_XMIT_BYPASS;
 150
 151 error:
 152         spin_unlock_bh(&x->lock);
 153 error_nolock:
 154         kfree_skb(*pskb);
 155         return err;
 156 }
 157
 158 int ah_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
 159 {
 160         int ah_hlen;
 161         struct iphdr *iph;
 162         struct ip_auth_hdr *ah;
 163         struct ah_data *ahp;
 164         char work_buf[60];
 165
 166         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 167                 goto out;
 168
 169         ah = (struct ip_auth_hdr*)skb->data;
 170         ahp = x->data;
 171         ah_hlen = (ah->hdrlen + 2) << 2;
 172
 173         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_full_len) &&
 174             ah_hlen != XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_trunc_len))
 175                 goto out;
 176
 177         if (!pskb_may_pull(skb, ah_hlen))
 178                 goto out;
 179
 180         /* We are going to _remove_ AH header to keep sockets happy,
 181          * so... Later this can change. */
 182         if (skb_cloned(skb) &&
 183             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 184                 goto out;
 185
 186         skb->ip_summed = CHECKSUM_NONE;
 187
 188         ah = (struct ip_auth_hdr*)skb->data;
 189         iph = skb->nh.iph;
 190
 191         memcpy(work_buf, iph, iph->ihl*4);
 192
 193         iph->ttl = 0;
 194         iph->tos = 0;
 195         iph->frag_off = 0;
 196         iph->check = 0;
 197         if (iph->ihl != 5) {
 198                 u32 dummy;
 199                 if (ip_clear_mutable_options(iph, &dummy))
 200                         goto out;
 201         }
 202         {
 203                 u8 auth_data[MAX_AH_AUTH_LEN];
 204
 205                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 206                 skb_push(skb, skb->data - skb->nh.raw);
 207                 ahp->icv(ahp, skb, ah->auth_data);
 208                 if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
 209                         x->stats.integrity_failed++;
 210                         goto out;
 211                 }
 212         }
 213         ((struct iphdr*)work_buf)->protocol = ah->nexthdr;
 214         skb->nh.raw = skb_pull(skb, ah_hlen);
 215         memcpy(skb->nh.raw, work_buf, iph->ihl*4);
 216         skb->nh.iph->tot_len = htons(skb->len);
 217         skb_pull(skb, skb->nh.iph->ihl*4);
 218         skb->h.raw = skb->data;
 219
 220         return 0;
 221
 222 out:
 223         return -EINVAL;
 224 }
 225
 226 void ah4_err(struct sk_buff *skb, u32 info)
 227 {
 228         struct iphdr *iph = (struct iphdr*)skb->data;
 229         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
 230         struct xfrm_state *x;
 231
 232         if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
 233             skb->h.icmph->code != ICMP_FRAG_NEEDED)
 234                 return;
 235
 236         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
 237         if (!x)
 238                 return;
 239         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 240                ntohl(ah->spi), ntohl(iph->daddr));
 241         xfrm_state_put(x);
 242 }
 243
 244 static int ah_init_state(struct xfrm_state *x, void *args)
 245 {
 246         struct ah_data *ahp = NULL;
 247         struct xfrm_algo_desc *aalg_desc;
 248
 249         if (!x->aalg)
 250                 goto error;
 251
 252         /* null auth can use a zero length key */
 253         if (x->aalg->alg_key_len > 512)
 254                 goto error;
 255
 256         ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
 257         if (ahp == NULL)
 258                 return -ENOMEM;
 259
 260         memset(ahp, 0, sizeof(*ahp));
 261
 262         ahp->key = x->aalg->alg_key;
 263         ahp->key_len = (x->aalg->alg_key_len+7)/8;
 264         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
 265         if (!ahp->tfm)
 266                 goto error;
 267         ahp->icv = ah_hmac_digest;
 268
 269         /*
 270          * Lookup the algorithm description maintained by xfrm_algo,
 271          * verify crypto transform properties, and store information
 272          * we need for AH processing.  This lookup cannot fail here
 273          * after a successful crypto_alloc_tfm().
 274          */
 275         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name);
 276         BUG_ON(!aalg_desc);
 277
 278         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 279             crypto_tfm_alg_digestsize(ahp->tfm)) {
 280                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 281                        x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
 282                        aalg_desc->uinfo.auth.icv_fullbits/8);
 283                 goto error;
 284         }
 285
 286         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 287         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 288
 289         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 290
 291         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 292         if (!ahp->work_icv)
 293                 goto error;
 294
 295         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_trunc_len);
 296         if (x->props.mode)
 297                 x->props.header_len += sizeof(struct iphdr);
 298         x->data = ahp;
 299
 300         return 0;
 301
 302 error:
 303         if (ahp) {
 304                 if (ahp->work_icv)
 305                         kfree(ahp->work_icv);
 306                 if (ahp->tfm)
 307                         crypto_free_tfm(ahp->tfm);
 308                 kfree(ahp);
 309         }
 310         return -EINVAL;
 311 }
 312
 313 static void ah_destroy(struct xfrm_state *x)
 314 {
 315         struct ah_data *ahp = x->data;
 316
 317         if (!ahp)
 318                 return;
 319
 320         if (ahp->work_icv) {
 321                 kfree(ahp->work_icv);
 322                 ahp->work_icv = NULL;
 323         }
 324         if (ahp->tfm) {
 325                 crypto_free_tfm(ahp->tfm);
 326                 ahp->tfm = NULL;
 327         }
 328         kfree(ahp);
 329 }
 330
 331
 332 static struct xfrm_type ah_type =
 333 {
 334         .description    = "AH4",
 335         .owner          = THIS_MODULE,
 336         .proto          = IPPROTO_AH,
 337         .init_state     = ah_init_state,
 338         .destructor     = ah_destroy,
 339         .input          = ah_input,
 340         .output         = ah_output
 341 };
 342
 343 static struct inet_protocol ah4_protocol = {
 344         .handler        =       xfrm4_rcv,
 345         .err_handler    =       ah4_err,
 346         .no_policy      =       1,
 347 };
 348
 349 static int __init ah4_init(void)
 350 {
 351         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 352                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 353                 return -EAGAIN;
 354         }
 355         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 356                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 357                 xfrm_unregister_type(&ah_type, AF_INET);
 358                 return -EAGAIN;
 359         }
 360         return 0;
 361 }
 362
 363 static void __exit ah4_fini(void)
 364 {
 365         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 366                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 367         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 368                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 369 }
 370
 371 module_init(ah4_init);
 372 module_exit(ah4_fini);
 373 MODULE_LICENSE("GPL");