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         err = 0;
 119
 120 error:
 121         return err;
 122 }
 123
 124 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 125 {
 126         int ah_hlen;
 127         int ihl;
 128         int nexthdr;
 129         int err = -EINVAL;
 130         struct iphdr *iph;
 131         struct ip_auth_hdr *ah;
 132         struct ah_data *ahp;
 133         char work_buf[60];
 134
 135         if (!pskb_may_pull(skb, sizeof(*ah)))
 136                 goto out;
 137
 138         ah = (struct ip_auth_hdr *)skb->data;
 139         ahp = x->data;
 140         nexthdr = ah->nexthdr;
 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         skb->network_header += ah_hlen;
 188         memcpy(skb_network_header(skb), work_buf, ihl);
 189         skb->transport_header = skb->network_header;
 190         __skb_pull(skb, ah_hlen + ihl);
 191
 192         return nexthdr;
 193
 194 out:
 195         return err;
 196 }
 197
 198 static void ah4_err(struct sk_buff *skb, u32 info)
 199 {
 200         struct iphdr *iph = (struct iphdr*)skb->data;
 201         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
 202         struct xfrm_state *x;
 203
 204         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
 205             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
 206                 return;
 207
 208         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
 209         if (!x)
 210                 return;
 211         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
 212                ntohl(ah->spi), ntohl(iph->daddr));
 213         xfrm_state_put(x);
 214 }
 215
 216 static int ah_init_state(struct xfrm_state *x)
 217 {
 218         struct ah_data *ahp = NULL;
 219         struct xfrm_algo_desc *aalg_desc;
 220         struct crypto_hash *tfm;
 221
 222         if (!x->aalg)
 223                 goto error;
 224
 225         if (x->encap)
 226                 goto error;
 227
 228         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
 229         if (ahp == NULL)
 230                 return -ENOMEM;
 231
 232         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
 233         if (IS_ERR(tfm))
 234                 goto error;
 235
 236         ahp->tfm = tfm;
 237         if (crypto_hash_setkey(tfm, x->aalg->alg_key,
 238                                (x->aalg->alg_key_len + 7) / 8))
 239                 goto error;
 240
 241         /*
 242          * Lookup the algorithm description maintained by xfrm_algo,
 243          * verify crypto transform properties, and store information
 244          * we need for AH processing.  This lookup cannot fail here
 245          * after a successful crypto_alloc_hash().
 246          */
 247         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
 248         BUG_ON(!aalg_desc);
 249
 250         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 251             crypto_hash_digestsize(tfm)) {
 252                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
 253                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
 254                        aalg_desc->uinfo.auth.icv_fullbits/8);
 255                 goto error;
 256         }
 257
 258         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
 259         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
 260
 261         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
 262
 263         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
 264         if (!ahp->work_icv)
 265                 goto error;
 266
 267         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 268                                           ahp->icv_trunc_len);
 269         if (x->props.mode == XFRM_MODE_TUNNEL)
 270                 x->props.header_len += sizeof(struct iphdr);
 271         x->data = ahp;
 272
 273         return 0;
 274
 275 error:
 276         if (ahp) {
 277                 kfree(ahp->work_icv);
 278                 crypto_free_hash(ahp->tfm);
 279                 kfree(ahp);
 280         }
 281         return -EINVAL;
 282 }
 283
 284 static void ah_destroy(struct xfrm_state *x)
 285 {
 286         struct ah_data *ahp = x->data;
 287
 288         if (!ahp)
 289                 return;
 290
 291         kfree(ahp->work_icv);
 292         ahp->work_icv = NULL;
 293         crypto_free_hash(ahp->tfm);
 294         ahp->tfm = NULL;
 295         kfree(ahp);
 296 }
 297
 298
 299 static struct xfrm_type ah_type =
 300 {
 301         .description    = "AH4",
 302         .owner          = THIS_MODULE,
 303         .proto          = IPPROTO_AH,
 304         .flags          = XFRM_TYPE_REPLAY_PROT,
 305         .init_state     = ah_init_state,
 306         .destructor     = ah_destroy,
 307         .input          = ah_input,
 308         .output         = ah_output
 309 };
 310
 311 static struct net_protocol ah4_protocol = {
 312         .handler        =       xfrm4_rcv,
 313         .err_handler    =       ah4_err,
 314         .no_policy      =       1,
 315 };
 316
 317 static int __init ah4_init(void)
 318 {
 319         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 320                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
 321                 return -EAGAIN;
 322         }
 323         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 324                 printk(KERN_INFO "ip ah init: can't add protocol\n");
 325                 xfrm_unregister_type(&ah_type, AF_INET);
 326                 return -EAGAIN;
 327         }
 328         return 0;
 329 }
 330
 331 static void __exit ah4_fini(void)
 332 {
 333         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 334                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
 335         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 336                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
 337 }
 338
 339 module_init(ah4_init);
 340 module_exit(ah4_fini);
 341 MODULE_LICENSE("GPL");
 342 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);