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