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 manip_addr:
 103         if (maniptype == NF_NAT_MANIP_SRC)
 104                 ipv6h->saddr = target->src.u3.in6;
 105         else
 106                 ipv6h->daddr = target->dst.u3.in6;
 107
 108         return true;
 109 }
 110
 111 static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
 112                                     unsigned int iphdroff, __sum16 *check,
 113                                     const struct nf_conntrack_tuple *t,
 114                                     enum nf_nat_manip_type maniptype)
 115 {
 116         const struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + iphdroff);
 117         const struct in6_addr *oldip, *newip;
 118
 119         if (maniptype == NF_NAT_MANIP_SRC) {
 120                 oldip = &ipv6h->saddr;
 121                 newip = &t->src.u3.in6;
 122         } else {
 123                 oldip = &ipv6h->daddr;
 124                 newip = &t->dst.u3.in6;
 125         }
 126         inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
 127                                   newip->s6_addr32, true);
 128 }
 129
 130 static void nf_nat_ipv6_csum_recalc(struct sk_buff *skb,
 131                                     u8 proto, void *data, __sum16 *check,
 132                                     int datalen, int oldlen)
 133 {
 134         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 135         struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 136
 137         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 138                 if (!(rt->rt6i_flags & RTF_LOCAL) &&
 139                     (!skb->dev || skb->dev->features & NETIF_F_V6_CSUM)) {
 140                         skb->ip_summed = CHECKSUM_PARTIAL;
 141                         skb->csum_start = skb_headroom(skb) +
 142                                           skb_network_offset(skb) +
 143                                           (data - (void *)skb->data);
 144                         skb->csum_offset = (void *)check - data;
 145                         *check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 146                                                   datalen, proto, 0);
 147                 } else {
 148                         *check = 0;
 149                         *check = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 150                                                  datalen, proto,
 151                                                  csum_partial(data, datalen,
 152                                                               0));
 153                         if (proto == IPPROTO_UDP && !*check)
 154                                 *check = CSUM_MANGLED_0;
 155                 }
 156         } else
 157                 inet_proto_csum_replace2(check, skb,
 158                                          htons(oldlen), htons(datalen), true);
 159 }
 160
 161 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 162 static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
 163                                        struct nf_nat_range *range)
 164 {
 165         if (tb[CTA_NAT_V6_MINIP]) {
 166                 nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
 167                            sizeof(struct in6_addr));
 168                 range->flags |= NF_NAT_RANGE_MAP_IPS;
 169         }
 170
 171         if (tb[CTA_NAT_V6_MAXIP])
 172                 nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
 173                            sizeof(struct in6_addr));
 174         else
 175                 range->max_addr = range->min_addr;
 176
 177         return 0;
 178 }
 179 #endif
 180
 181 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
 182         .l3proto                = NFPROTO_IPV6,
 183         .secure_port            = nf_nat_ipv6_secure_port,
 184         .in_range               = nf_nat_ipv6_in_range,
 185         .manip_pkt              = nf_nat_ipv6_manip_pkt,
 186         .csum_update            = nf_nat_ipv6_csum_update,
 187         .csum_recalc            = nf_nat_ipv6_csum_recalc,
 188 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 189         .nlattr_to_range        = nf_nat_ipv6_nlattr_to_range,
 190 #endif
 191 #ifdef CONFIG_XFRM
 192         .decode_session = nf_nat_ipv6_decode_session,
 193 #endif
 194 };
 195
 196 int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 197                                     struct nf_conn *ct,
 198                                     enum ip_conntrack_info ctinfo,
 199                                     unsigned int hooknum,
 200                                     unsigned int hdrlen)
 201 {
 202         struct {
 203                 struct icmp6hdr icmp6;
 204                 struct ipv6hdr  ip6;
 205         } *inside;
 206         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 207         enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 208         const struct nf_nat_l4proto *l4proto;
 209         struct nf_conntrack_tuple target;
 210         unsigned long statusbit;
 211
 212         NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
 213
 214         if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 215                 return 0;
 216         if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
 217                 return 0;
 218
 219         inside = (void *)skb->data + hdrlen;
 220         if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
 221                 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
 222                         return 0;
 223                 if (ct->status & IPS_NAT_MASK)
 224                         return 0;
 225         }
 226
 227         if (manip == NF_NAT_MANIP_SRC)
 228                 statusbit = IPS_SRC_NAT;
 229         else
 230                 statusbit = IPS_DST_NAT;
 231
 232         /* Invert if this is reply direction */
 233         if (dir == IP_CT_DIR_REPLY)
 234                 statusbit ^= IPS_NAT_MASK;
 235
 236         if (!(ct->status & statusbit))
 237                 return 1;
 238
 239         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
 240         if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 241                                    l4proto, &ct->tuplehash[!dir].tuple, !manip))
 242                 return 0;
 243
 244         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 245                 struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 246                 inside = (void *)skb->data + hdrlen;
 247                 inside->icmp6.icmp6_cksum = 0;
 248                 inside->icmp6.icmp6_cksum =
 249                         csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 250                                         skb->len - hdrlen, IPPROTO_ICMPV6,
 251                                         csum_partial(&inside->icmp6,
 252                                                      skb->len - hdrlen, 0));
 253         }
 254
 255         nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 256         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
 257         if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 258                 return 0;
 259
 260         return 1;
 261 }
 262 EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);
 263
 264 unsigned int
 265 nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
 266                const struct nf_hook_state *state,
 267                unsigned int (*do_chain)(void *priv,
 268                                         struct sk_buff *skb,
 269                                         const struct nf_hook_state *state,
 270                                         struct nf_conn *ct))
 271 {
 272         struct nf_conn *ct;
 273         enum ip_conntrack_info ctinfo;
 274         struct nf_conn_nat *nat;
 275         enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
 276         __be16 frag_off;
 277         int hdrlen;
 278         u8 nexthdr;
 279
 280         ct = nf_ct_get(skb, &ctinfo);
 281         /* Can't track?  It's not due to stress, or conntrack would
 282          * have dropped it.  Hence it's the user's responsibilty to
 283          * packet filter it out, or implement conntrack/NAT for that
 284          * protocol. 8) --RR
 285          */
 286         if (!ct)
 287                 return NF_ACCEPT;
 288
 289         /* Don't try to NAT if this packet is not conntracked */
 290         if (nf_ct_is_untracked(ct))
 291                 return NF_ACCEPT;
 292
 293         nat = nf_ct_nat_ext_add(ct);
 294         if (nat == NULL)
 295                 return NF_ACCEPT;
 296
 297         switch (ctinfo) {
 298         case IP_CT_RELATED:
 299         case IP_CT_RELATED_REPLY:
 300                 nexthdr = ipv6_hdr(skb)->nexthdr;
 301                 hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
 302                                           &nexthdr, &frag_off);
 303
 304                 if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
 305                         if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
 306                                                              state->hook,
 307                                                              hdrlen))
 308                                 return NF_DROP;
 309                         else
 310                                 return NF_ACCEPT;
 311                 }
 312                 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
 313         case IP_CT_NEW:
 314                 /* Seen it before?  This can happen for loopback, retrans,
 315                  * or local packets.
 316                  */
 317                 if (!nf_nat_initialized(ct, maniptype)) {
 318                         unsigned int ret;
 319
 320                         ret = do_chain(priv, skb, state, ct);
 321                         if (ret != NF_ACCEPT)
 322                                 return ret;
 323
 324                         if (nf_nat_initialized(ct, HOOK2MANIP(state->hook)))
 325                                 break;
 326
 327                         ret = nf_nat_alloc_null_binding(ct, state->hook);
 328                         if (ret != NF_ACCEPT)
 329                                 return ret;
 330                 } else {
 331                         pr_debug("Already setup manip %s for ct %p\n",
 332                                  maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
 333                                  ct);
 334                         if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 335                                 goto oif_changed;
 336                 }
 337                 break;
 338
 339         default:
 340                 /* ESTABLISHED */
 341                 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
 342                              ctinfo == IP_CT_ESTABLISHED_REPLY);
 343                 if (nf_nat_oif_changed(state->hook, ctinfo, nat, state->out))
 344                         goto oif_changed;
 345         }
 346
 347         return nf_nat_packet(ct, ctinfo, state->hook, skb);
 348
 349 oif_changed:
 350         nf_ct_kill_acct(ct, ctinfo, skb);
 351         return NF_DROP;
 352 }
 353 EXPORT_SYMBOL_GPL(nf_nat_ipv6_fn);
 354
 355 unsigned int
 356 nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
 357                const struct nf_hook_state *state,
 358                unsigned int (*do_chain)(void *priv,
 359                                         struct sk_buff *skb,
 360                                         const struct nf_hook_state *state,
 361                                         struct nf_conn *ct))
 362 {
 363         unsigned int ret;
 364         struct in6_addr daddr = ipv6_hdr(skb)->daddr;
 365
 366         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 367         if (ret != NF_DROP && ret != NF_STOLEN &&
 368             ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
 369                 skb_dst_drop(skb);
 370
 371         return ret;
 372 }
 373 EXPORT_SYMBOL_GPL(nf_nat_ipv6_in);
 374
 375 unsigned int
 376 nf_nat_ipv6_out(void *priv, struct sk_buff *skb,
 377                 const struct nf_hook_state *state,
 378                 unsigned int (*do_chain)(void *priv,
 379                                          struct sk_buff *skb,
 380                                          const struct nf_hook_state *state,
 381                                          struct nf_conn *ct))
 382 {
 383 #ifdef CONFIG_XFRM
 384         const struct nf_conn *ct;
 385         enum ip_conntrack_info ctinfo;
 386         int err;
 387 #endif
 388         unsigned int ret;
 389
 390         /* root is playing with raw sockets. */
 391         if (skb->len < sizeof(struct ipv6hdr))
 392                 return NF_ACCEPT;
 393
 394         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 395 #ifdef CONFIG_XFRM
 396         if (ret != NF_DROP && ret != NF_STOLEN &&
 397             !(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 398             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 399                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 400
 401                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 402                                       &ct->tuplehash[!dir].tuple.dst.u3) ||
 403                     (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 404                      ct->tuplehash[dir].tuple.src.u.all !=
 405                      ct->tuplehash[!dir].tuple.dst.u.all)) {
 406                         err = nf_xfrm_me_harder(skb, AF_INET6);
 407                         if (err < 0)
 408                                 ret = NF_DROP_ERR(err);
 409                 }
 410         }
 411 #endif
 412         return ret;
 413 }
 414 EXPORT_SYMBOL_GPL(nf_nat_ipv6_out);
 415
 416 unsigned int
 417 nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 418                      const struct nf_hook_state *state,
 419                      unsigned int (*do_chain)(void *priv,
 420                                               struct sk_buff *skb,
 421                                               const struct nf_hook_state *state,
 422                                               struct nf_conn *ct))
 423 {
 424         const struct nf_conn *ct;
 425         enum ip_conntrack_info ctinfo;
 426         unsigned int ret;
 427         int err;
 428
 429         /* root is playing with raw sockets. */
 430         if (skb->len < sizeof(struct ipv6hdr))
 431                 return NF_ACCEPT;
 432
 433         ret = nf_nat_ipv6_fn(priv, skb, state, do_chain);
 434         if (ret != NF_DROP && ret != NF_STOLEN &&
 435             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 436                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 437
 438                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
 439                                       &ct->tuplehash[!dir].tuple.src.u3)) {
 440                         err = ip6_route_me_harder(skb);
 441                         if (err < 0)
 442                                 ret = NF_DROP_ERR(err);
 443                 }
 444 #ifdef CONFIG_XFRM
 445                 else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 446                          ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 447                          ct->tuplehash[dir].tuple.dst.u.all !=
 448                          ct->tuplehash[!dir].tuple.src.u.all) {
 449                         err = nf_xfrm_me_harder(skb, AF_INET6);
 450                         if (err < 0)
 451                                 ret = NF_DROP_ERR(err);
 452                 }
 453 #endif
 454         }
 455         return ret;
 456 }
 457 EXPORT_SYMBOL_GPL(nf_nat_ipv6_local_fn);
 458
 459 static int __init nf_nat_l3proto_ipv6_init(void)
 460 {
 461         int err;
 462
 463         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 464         if (err < 0)
 465                 goto err1;
 466         err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
 467         if (err < 0)
 468                 goto err2;
 469         return err;
 470
 471 err2:
 472         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 473 err1:
 474         return err;
 475 }
 476
 477 static void __exit nf_nat_l3proto_ipv6_exit(void)
 478 {
 479         nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
 480         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 481 }
 482
 483 MODULE_LICENSE("GPL");
 484 MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));
 485
 486 module_init(nf_nat_l3proto_ipv6_init);
 487 module_exit(nf_nat_l3proto_ipv6_exit);