net/ipv4/ah4.c

   1 #include <linux/err.h>
   2 #include <linux/module.h>
   3 #include <net/ip.h>
   4 #include <net/xfrm.h>
   5 #include <net/ah.h>
   6 #include <linux/crypto.h>
   7 #include <linux/pfkeyv2.h>
   8 #include <linux/spinlock.h>
   9 #include <net/icmp.h>
  10 #include <net/protocol.h>
  11 #include <asm/scatterlist.h>
  12
  13
  14 /* Clear mutable options and find final destination to substitute
  15  * into IP header for icv calculation. Options are already checked
  16  * for validity, so paranoia is not required. */
  17
  18 static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
  19 {
  20         unsigned char * optptr = (unsigned char*)(iph+1);
  21         int  l = iph->ihl*4 - sizeof(struct iphdr);
  22         int  optlen;
  23
  24         while (l > 0) {
  25                 switch (*optptr) {
  26                 case IPOPT_END:
  27                         return 0;
  28                 case IPOPT_NOOP:
  29                         l--;
  30                         optptr++;
  31                         continue;
  32                 }
  33                 optlen = optptr[1];
  34                 if (optlen<2 || optlen>l)
  35                         return -EINVAL;
  36                 switch (*optptr) {
  37                 case IPOPT_SEC:
  38                 case 0x85:      /* Some "Extended Security" crap. */
  39                 case IPOPT_CIPSO:
  40                 case IPOPT_RA:
  41                 case 0x80|21:   /* RFC1770 */
  42                         break;
  43                 case IPOPT_LSRR:
  44                 case IPOPT_SSRR:
  45                         if (optlen < 6)
  46                                 return -EINVAL;
  47                         memcpy(daddr, optptr+optlen-4, 4);
  48                         /* Fall through */
  49                 default:
  50                         memset(optptr, 0, optlen);
  51                 }
  52                 l -= optlen;
  53                 optptr += optlen;
  54         }
  55         return 0;
  56 }
  57
  58 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
  59 {
  60         int err;
  61         struct iphdr *iph, *top_iph;
  62         struct ip_auth_hdr *ah;
  63         struct ah_data *ahp;
  64         union {
  65                 struct iphdr    iph;
  66                 char            buf[60];
  67         } tmp_iph;
  68
  69         skb_push(skb, -skb_network_offset(skb));
  70         top_iph = ip_hdr(skb);
  71         iph = &tmp_iph.iph;
  72
  73         iph->tos = top_iph->tos;
  74         iph->ttl = top_iph->ttl;
  75         iph->frag_off = top_iph->frag_off;
  76
  77         if (top_iph->ihl != 5) {
  78                 iph->daddr = top_iph->daddr;
  79                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
  80                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
  81                 if (err)
  82                         goto error;
  83         }
  84
  85         ah = ip_auth_hdr(skb);
  86         ah->nexthdr = *skb_mac_header(skb);
  87         *skb_mac_header(skb) = IPPROTO_AH;
  88
  89         top_iph->tos = 0;
  90         top_iph->tot_len = htons(skb->len);
  91         top_iph->frag_off = 0;
  92         top_iph->ttl = 0;
  93         top_iph->check = 0;
  94
  95         ahp = x->data;
  96         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
  97
  98         ah->reserved = 0;
  99         ah->spi = x->id.spi;
 100         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
 101
 102         spin_lock_bh(&x->lock);
 103         err = ah_mac_digest(ahp, skb, ah->auth_data);
 104         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
 105         spin_unlock_bh(&x->lock);
 106
 107         if (err)
 108                 goto error;
 109
 110         top_iph->tos = iph->tos;
 111         top_iph->ttl = iph->ttl;
 112         top_iph->frag_off = iph->frag_off;
 113         if (top_iph->ihl != 5) {
 114                 top_iph->daddr = iph->daddr;
 115                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 116         }
 117
 118         ip_send_check(top_iph);
 119
 120         err = 0;
 121
 122 error:
 123         return err;
 124 }
 125
 126 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 127 {
 128         int ah_hlen;
 129         int ihl;
 130         int err = -EINVAL;
 131         struct iphdr *iph;
 132         struct ip_auth_hdr *ah;
 133         struct ah_data *ahp;
 134         char work_buf[60];
 135
 136         if (!pskb_may_pull(skb, sizeof(*ah)))
 137                 goto out;
 138
 139         ah = (struct ip_auth_hdr *)skb->data;
 140         ahp = x->data;
 141         ah_hlen = (ah->hdrlen + 2) << 2;
 142
 143         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
 144             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
 145                 goto out;
 146
 147         if (!pskb_may_pull(skb, ah_hlen))
 148                 goto out;
 149
 150         /* We are going to _remove_ AH header to keep sockets happy,
 151          * so... Later this can change. */
 152         if (skb_cloned(skb) &&
 153             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 154                 goto out;
 155
 156         skb->ip_summed = CHECKSUM_NONE;
 157
 158         ah = (struct ip_auth_hdr *)skb->data;
 159         iph = ip_hdr(skb);
 160
 161         ihl = skb->data - skb_network_header(skb);
 162         memcpy(work_buf, iph, ihl);
 163
 164         iph->ttl = 0;
 165         iph->tos = 0;
 166         iph->frag_off = 0;
 167         iph->check = 0;
 168         if (ihl > sizeof(*iph)) {
 169                 __be32 dummy;
 170                 if (ip_clear_mutable_options(iph, &dummy))
 171                         goto out;
 172         }
 173         {
 174                 u8 auth_data[MAX_AH_AUTH_LEN];
 175
 176                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 177                 skb_push(skb, ihl);
 178                 err = ah_mac_digest(ahp, skb, ah->auth_data);
 179                 if (err)
 180                         goto out;
 181                 err = -EINVAL;
 182                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 183                         x->stats.integrity_failed++;
 184                         goto out;
 185                 }
 186         }
 187         ((struct iphdr*)work_buf)->protocol = ah->nexthdr;
 188         skb->network_header += ah_hlen;
 189         memcpy(skb_network_header(skb), work_buf, ihl);
 190         skb->transport_header = skb->network_header;
 191         __skb_pull(skb, ah_hlen + ihl);
 192
 193         return 0;
 194
 195 out:
 196         return err;
 197 }
 198
 199 static void ah4_err(struct sk_buff *skb, u32 info)
 200 {
 201         struct iphdr *iph = (struct iphdr*)skb->data;
 202         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
 203         struct xfrm_state *x;
 204
 205         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 206             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 207                 return;
 208
 209         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
 210         if (!x)
 211                 return;
 212         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 213                ntohl(ah->spi), ntohl(iph->daddr));
 214         xfrm_state_put(x);
 215 }
 216
 217 static int ah_init_state(struct xfrm_state *x)
 218 {
 219         struct ah_data *ahp = NULL;
 220         struct xfrm_algo_desc *aalg_desc;
 221         struct crypto_hash *tfm;
 222
 223         if (!x->aalg)
 224                 goto error;
 225
 226         if (x->encap)
 227                 goto error;
 228
 229         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 230         if (ahp == NULL)
 231                 return -ENOMEM;
 232
 233         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 234         if (IS_ERR(tfm))
 235                 goto error;
 236
 237         ahp->tfm = tfm;
 238         if (crypto_hash_setkey(tfm, x->aalg->alg_key,
 239                                (x->aalg->alg_key_len + 7) / 8))
 240                 goto error;
 241
 242         /*
 243          * Lookup the algorithm description maintained by xfrm_algo,
 244          * verify crypto transform properties, and store information
 245          * we need for AH processing.  This lookup cannot fail here
 246          * after a successful crypto_alloc_hash().
 247          */
 248         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 249         BUG_ON(!aalg_desc);
 250
 251         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 252             crypto_hash_digestsize(tfm)) {
 253                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 254                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 255                        aalg_desc->uinfo.auth.icv_fullbits/8);
 256                 goto error;
 257         }
 258
 259         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 260         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 261
 262         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 263
 264         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 265         if (!ahp->work_icv)
 266                 goto error;
 267
 268         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 269                                           ahp->icv_trunc_len);
 270         if (x->props.mode == XFRM_MODE_TUNNEL)
 271                 x->props.header_len += sizeof(struct iphdr);
 272         x->data = ahp;
 273
 274         return 0;
 275
 276 error:
 277         if (ahp) {
 278                 kfree(ahp->work_icv);
 279                 crypto_free_hash(ahp->tfm);
 280                 kfree(ahp);
 281         }
 282         return -EINVAL;
 283 }
 284
 285 static void ah_destroy(struct xfrm_state *x)
 286 {
 287         struct ah_data *ahp = x->data;
 288
 289         if (!ahp)
 290                 return;
 291
 292         kfree(ahp->work_icv);
 293         ahp->work_icv = NULL;
 294         crypto_free_hash(ahp->tfm);
 295         ahp->tfm = NULL;
 296         kfree(ahp);
 297 }
 298
 299
 300 static struct xfrm_type ah_type =
 301 {
 302         .description    = "AH4",
 303         .owner          = THIS_MODULE,
 304         .proto          = IPPROTO_AH,
 305         .flags          = XFRM_TYPE_REPLAY_PROT,
 306         .init_state     = ah_init_state,
 307         .destructor     = ah_destroy,
 308         .input          = ah_input,
 309         .output         = ah_output
 310 };
 311
 312 static struct net_protocol ah4_protocol = {
 313         .handler        =       xfrm4_rcv,
 314         .err_handler    =       ah4_err,
 315         .no_policy      =       1,
 316 };
 317
 318 static int __init ah4_init(void)
 319 {
 320         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 321                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 322                 return -EAGAIN;
 323         }
 324         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 325                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 326                 xfrm_unregister_type(&ah_type, AF_INET);
 327                 return -EAGAIN;
 328         }
 329         return 0;
 330 }
 331
 332 static void __exit ah4_fini(void)
 333 {
 334         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 335                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 336         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 337                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 338 }
 339
 340 module_init(ah4_init);
 341 module_exit(ah4_fini);
 342 MODULE_LICENSE("GPL");
 343 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);