net/ipv6/netfilter/nf_nat_l3proto_ipv6.c

   1 /*
   2  * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Development of IPv6 NAT funded by Astaro.
   9  */
  10 #include <linux/types.h>
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ipv6.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter_ipv6.h>
  16 #include <net/secure_seq.h>
  17 #include <net/checksum.h>
  18 #include <net/ip6_checksum.h>
  19 #include <net/ip6_route.h>
  20 #include <net/ipv6.h>
  21
  22 #include <net/netfilter/nf_conntrack_core.h>
  23 #include <net/netfilter/nf_conntrack.h>
  24 #include <net/netfilter/nf_nat_core.h>
  25 #include <net/netfilter/nf_nat_l3proto.h>
  26 #include <net/netfilter/nf_nat_l4proto.h>
  27
  28 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6;
  29
  30 #ifdef CONFIG_XFRM
  31 static void nf_nat_ipv6_decode_session(struct sk_buff *skb,
  32                                        const struct nf_conn *ct,
  33                                        enum ip_conntrack_dir dir,
  34                                        unsigned long statusbit,
  35                                        struct flowi *fl)
  36 {
  37         const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
  38         struct flowi6 *fl6 = &fl->u.ip6;
  39
  40         if (ct->status & statusbit) {
  41                 fl6->daddr = t->dst.u3.in6;
  42                 if (t->dst.protonum == IPPROTO_TCP ||
  43                     t->dst.protonum == IPPROTO_UDP ||
  44                     t->dst.protonum == IPPROTO_UDPLITE ||
  45                     t->dst.protonum == IPPROTO_DCCP ||
  46                     t->dst.protonum == IPPROTO_SCTP)
  47                         fl6->fl6_dport = t->dst.u.all;
  48         }
  49
  50         statusbit ^= IPS_NAT_MASK;
  51
  52         if (ct->status & statusbit) {
  53                 fl6->saddr = t->src.u3.in6;
  54                 if (t->dst.protonum == IPPROTO_TCP ||
  55                     t->dst.protonum == IPPROTO_UDP ||
  56                     t->dst.protonum == IPPROTO_UDPLITE ||
  57                     t->dst.protonum == IPPROTO_DCCP ||
  58                     t->dst.protonum == IPPROTO_SCTP)
  59                         fl6->fl6_sport = t->src.u.all;
  60         }
  61 }
  62 #endif
  63
  64 static bool nf_nat_ipv6_in_range(const struct nf_conntrack_tuple *t,
  65                                  const struct nf_nat_range *range)
  66 {
  67         return ipv6_addr_cmp(&t->src.u3.in6, &range->min_addr.in6) >= 0 &&
  68                ipv6_addr_cmp(&t->src.u3.in6, &range->max_addr.in6) <= 0;
  69 }
  70
  71 static u32 nf_nat_ipv6_secure_port(const struct nf_conntrack_tuple *t,
  72                                    __be16 dport)
  73 {
  74         return secure_ipv6_port_ephemeral(t->src.u3.ip6, t->dst.u3.ip6, dport);
  75 }
  76
  77 static bool nf_nat_ipv6_manip_pkt(struct sk_buff *skb,
  78                                   unsigned int iphdroff,
  79                                   const struct nf_nat_l4proto *l4proto,
  80                                   const struct nf_conntrack_tuple *target,
  81                                   enum nf_nat_manip_type maniptype)
  82 {
  83         struct ipv6hdr *ipv6h;
  84         __be16 frag_off;
  85         int hdroff;
  86         u8 nexthdr;
  87
  88         if (!skb_make_writable(skb, iphdroff + sizeof(*ipv6h)))
  89                 return false;
  90
  91         ipv6h = (void *)skb->data + iphdroff;
  92         nexthdr = ipv6h->nexthdr;
  93         hdroff = ipv6_skip_exthdr(skb, iphdroff + sizeof(*ipv6h),
  94                                   &nexthdr, &frag_off);
  95         if (hdroff < 0)
  96                 goto manip_addr;
  97
  98         if ((frag_off & htons(~0x7)) == 0 &&
  99             !l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
 100                                 target, maniptype))
 101                 return false;
 102
 103         /* must reload, offset might have changed */
 104         ipv6h = (void *)skb->data + iphdroff;
 105
 106 manip_addr:
 107         if (maniptype == NF_NAT_MANIP_SRC)
 108                 ipv6h->saddr = target->src.u3.in6;
 109         else
 110                 ipv6h->daddr = target->dst.u3.in6;
 111
 112         return true;
 113 }
 114
 115 static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
 116                                     unsigned int iphdroff, __sum16 *check,
 117                                     const struct nf_conntrack_tuple *t,
 118                                     enum nf_nat_manip_type maniptype)
 119 {
 120         const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
 121         const struct in6_addr *oldip, *newip;
 122
 123         if (maniptype == NF_NAT_MANIP_SRC) {
 124                 oldip = &ipv6h->saddr;
 125                 newip = &t->src.u3.in6;
 126         } else {
 127                 oldip = &ipv6h->daddr;
 128                 newip = &t->dst.u3.in6;
 129         }
 130         inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
 131                                   newip->s6_addr32, true);
 132 }
 133
 134 static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
 135                                     u8 proto, void *data, __sum16 *check,
 136                                     int datalen, int oldlen)
 137 {
 138         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 139         struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 140
 141         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 142                 if (!(rt->rt6i_flags & RTF_LOCAL) &&
 143                     (!skb->dev || skb->dev->features & NETIF_F_V6_CSUM)) {
 144                         skb->ip_summed = CHECKSUM_PARTIAL;
 145                         skb->csum_start = skb_headroom(skb) +
 146                                           skb_network_offset(skb) +
 147                                           (data - (void *)skb->data);
 148                         skb->csum_offset = (void *)check - data;
 149                         *check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 150                                                   datalen, proto, 0);
 151                 } else {
 152                         *check = 0;
 153                         *check = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 154                                                  datalen, proto,
 155                                                  csum_partial(data, datalen,
 156                                                               0));
 157                         if (proto == IPPROTO_UDP && !*check)
 158                                 *check = CSUM_MANGLED_0;
 159                 }
 160         } else
 161                 inet_proto_csum_replace2(check, skb,
 162                                          htons(oldlen), htons(datalen), true);
 163 }
 164
 165 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 166 static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
 167                                        struct nf_nat_range *range)
 168 {
 169         if (tb[CTA_NAT_V6_MINIP]) {
 170                 nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
 171                            sizeof(struct in6_addr));
 172                 range->flags |= NF_NAT_RANGE_MAP_IPS;
 173         }
 174
 175         if (tb[CTA_NAT_V6_MAXIP])
 176                 nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
 177                            sizeof(struct in6_addr));
 178         else
 179                 range->max_addr = range->min_addr;
 180
 181         return 0;
 182 }
 183 #endif
 184
 185 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
 186         .l3proto                = NFPROTO_IPV6,
 187         .secure_port            = nf_nat_ipv6_secure_port,
 188         .in_range               = nf_nat_ipv6_in_range,
 189         .manip_pkt              = nf_nat_ipv6_manip_pkt,
 190         .csum_update            = nf_nat_ipv6_csum_update,
 191         .csum_recalc            = nf_nat_ipv6_csum_recalc,
 192 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 193         .nlattr_to_range        = nf_nat_ipv6_nlattr_to_range,
 194 #endif
 195 #ifdef CONFIG_XFRM
 196         .decode_session = nf_nat_ipv6_decode_session,
 197 #endif
 198 };
 199
 200 int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 201                                     struct nf_conn *ct,
 202                                     enum ip_conntrack_info ctinfo,
 203                                     unsigned int hooknum,
 204                                     unsigned int hdrlen)
 205 {
 206         struct {
 207                 struct icmp6hdr icmp6;
 208                 struct ipv6hdr  ip6;
 209         } *inside;
 210         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 211         enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 212         const struct nf_nat_l4proto *l4proto;
 213         struct nf_conntrack_tuple target;
 214         unsigned long statusbit;
 215
 216         NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
 217
 218         if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 219                 return 0;
 220         if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
 221                 return 0;
 222
 223         inside = (void *)skb->data + hdrlen;
 224         if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
 225                 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
 226                         return 0;
 227                 if (ct->status & IPS_NAT_MASK)
 228                         return 0;
 229         }
 230
 231         if (manip == NF_NAT_MANIP_SRC)
 232                 statusbit = IPS_SRC_NAT;
 233         else
 234                 statusbit = IPS_DST_NAT;
 235
 236         /* Invert if this is reply direction */
 237         if (dir == IP_CT_DIR_REPLY)
 238                 statusbit ^= IPS_NAT_MASK;
 239
 240         if (!(ct->status & statusbit))
 241                 return 1;
 242
 243         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
 244         if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 245                                    l4proto, &ct->tuplehash[!dir].tuple, !manip))
 246                 return 0;
 247
 248         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 249                 struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 250                 inside = (void *)skb->data + hdrlen;
 251                 inside->icmp6.icmp6_cksum = 0;
 252                 inside->icmp6.icmp6_cksum =
 253                         csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 254                                         skb->len - hdrlen, IPPROTO_ICMPV6,
 255                                         csum_partial(&inside->icmp6,
 256                                                      skb->len - hdrlen, 0));
 257         }
 258
 259         nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 260         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
 261         if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 262                 return 0;
 263
 264         return 1;
 265 }
 266 EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);
 267
 268 unsigned int
 269 nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
 270                const struct nf_hook_state *state,
 271                unsigned int (*do_chain)(void *priv,
 272                                         struct sk_buff *skb,
 273                                         const struct nf_hook_state *state,
 274                                         struct nf_conn *ct))
 275 {
 276         struct nf_conn *ct;
 277         enum ip_conntrack_info ctinfo;
 278         struct nf_conn_nat *nat;
 279         enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
 280         __be16 frag_off;
 281         int hdrlen;
 282         u8 nexthdr;
 283
 284         ct = nf_ct_get(skb, &ctinfo);
 285         /* Can't track?  It's not due to stress, or conntrack would
 286          * have dropped it.  Hence it's the user's responsibilty to
 287          * packet filter it out, or implement conntrack/NAT for that
 288          * protocol. 8) --RR
 289          */
 290         if (!ct)
 291                 return NF_ACCEPT;
 292
 293         /* Don't try to NAT if this packet is not conntracked */
 294         if (nf_ct_is_untracked(ct))
 295                 return NF_ACCEPT;
 296
 297         nat = nf_ct_nat_ext_add(ct);
 298         if (nat == NULL)
 299                 return NF_ACCEPT;
 300
 301         switch (ctinfo) {
 302         case IP_CT_RELATED:
 303         case IP_CT_RELATED_REPLY:
 304                 nexthdr = ipv6_hdr(skb)->nexthdr;
 305                 hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
 306                                           &nexthdr, &frag_off);
 307
 308                 if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
 309                         if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
 310                                                              state->hook,
 311                                                              hdrlen))
 312                                 return NF_DROP;
 313                         else
 314                                 return NF_ACCEPT;
 315                 }
 316                 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 317         case IP_CT_NEW:
 318                 /* Seen it before?  This can happen for loopback, retrans,
 319                  * or local packets.
 320                  */
 321                 if (!nf_nat_initialized(ct, maniptype)) {
 322                         unsigned int ret;
 323
 324                         ret = do_chain(priv, skb, state, ct);
 325                         if (ret != NF_ACCEPT)
 326                                 return ret;
 327
 328                         if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
 329                                 break;
 330
 331                         ret = nf_nat_alloc_null_binding(ct, state->hook);
 332                         if (ret != NF_ACCEPT)
 333                                 return ret;
 334                 } else {
 335                         pr_debug("Already setup manip %s for ct %p\n",
 336                                  maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
 337                                  ct);
 338                         if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 339                                 goto oif_changed;
 340                 }
 341                 break;
 342
 343         default:
 344                 /* ESTABLISHED */
 345                 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
 346                              ctinfo == IP_CT_ESTABLISHED_REPLY);
 347                 if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 348                         goto oif_changed;
 349         }
 350
 351         return nf_nat_packet(ct, ctinfo, state->hook, skb);
 352
 353 oif_changed:
 354         nf_ct_kill_acct(ct, ctinfo, skb);
 355         return NF_DROP;
 356 }
 357 EXPORT_SYMBOL_GPL(nf_nat_ipv6_fn);
 358
 359 unsigned int
 360 nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
 361                const struct nf_hook_state *state,
 362                unsigned int (*do_chain)(void *priv,
 363                                         struct sk_buff *skb,
 364                                         const struct nf_hook_state *state,
 365                                         struct nf_conn *ct))
 366 {
 367         unsigned int ret;
 368         struct in6_addr daddr = ipv6_hdr(skb)->daddr;
 369
 370         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 371         if (ret != NF_DROP && ret != NF_STOLEN &&
 372             ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
 373                 skb_dst_drop(skb);
 374
 375         return ret;
 376 }
 377 EXPORT_SYMBOL_GPL(nf_nat_ipv6_in);
 378
 379 unsigned int
 380 nf_nat_ipv6_out(void *priv, struct sk_buff *skb,
 381                 const struct nf_hook_state *state,
 382                 unsigned int (*do_chain)(void *priv,
 383                                          struct sk_buff *skb,
 384                                          const struct nf_hook_state *state,
 385                                          struct nf_conn *ct))
 386 {
 387 #ifdef CONFIG_XFRM
 388         const struct nf_conn *ct;
 389         enum ip_conntrack_info ctinfo;
 390         int err;
 391 #endif
 392         unsigned int ret;
 393
 394         /* root is playing with raw sockets. */
 395         if (skb->len < sizeof(struct ipv6hdr))
 396                 return NF_ACCEPT;
 397
 398         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 399 #ifdef CONFIG_XFRM
 400         if (ret != NF_DROP && ret != NF_STOLEN &&
 401             !(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 402             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 403                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 404
 405                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 406                                       &ct->tuplehash[!dir].tuple.dst.u3) ||
 407                     (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 408                      ct->tuplehash[dir].tuple.src.u.all !=
 409                      ct->tuplehash[!dir].tuple.dst.u.all)) {
 410                         err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 411                         if (err < 0)
 412                                 ret = NF_DROP_ERR(err);
 413                 }
 414         }
 415 #endif
 416         return ret;
 417 }
 418 EXPORT_SYMBOL_GPL(nf_nat_ipv6_out);
 419
 420 unsigned int
 421 nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 422                      const struct nf_hook_state *state,
 423                      unsigned int (*do_chain)(void *priv,
 424                                               struct sk_buff *skb,
 425                                               const struct nf_hook_state *state,
 426                                               struct nf_conn *ct))
 427 {
 428         const struct nf_conn *ct;
 429         enum ip_conntrack_info ctinfo;
 430         unsigned int ret;
 431         int err;
 432
 433         /* root is playing with raw sockets. */
 434         if (skb->len < sizeof(struct ipv6hdr))
 435                 return NF_ACCEPT;
 436
 437         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 438         if (ret != NF_DROP && ret != NF_STOLEN &&
 439             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 440                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 441
 442                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
 443                                       &ct->tuplehash[!dir].tuple.src.u3)) {
 444                         err = ip6_route_me_harder(state->net, skb);
 445                         if (err < 0)
 446                                 ret = NF_DROP_ERR(err);
 447                 }
 448 #ifdef CONFIG_XFRM
 449                 else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 450                          ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 451                          ct->tuplehash[dir].tuple.dst.u.all !=
 452                          ct->tuplehash[!dir].tuple.src.u.all) {
 453                         err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 454                         if (err < 0)
 455                                 ret = NF_DROP_ERR(err);
 456                 }
 457 #endif
 458         }
 459         return ret;
 460 }
 461 EXPORT_SYMBOL_GPL(nf_nat_ipv6_local_fn);
 462
 463 static int __init nf_nat_l3proto_ipv6_init(void)
 464 {
 465         int err;
 466
 467         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 468         if (err < 0)
 469                 goto err1;
 470         err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
 471         if (err < 0)
 472                 goto err2;
 473         return err;
 474
 475 err2:
 476         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 477 err1:
 478         return err;
 479 }
 480
 481 static void __exit nf_nat_l3proto_ipv6_exit(void)
 482 {
 483         nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
 484         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 485 }
 486
 487 MODULE_LICENSE("GPL");
 488 MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));
 489
 490 module_init(nf_nat_l3proto_ipv6_init);
 491 module_exit(nf_nat_l3proto_ipv6_exit);