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