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