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_range2 *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         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 139                 const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 140
 141                 skb->ip_summed = CHECKSUM_PARTIAL;
 142                 skb->csum_start = skb_headroom(skb) + 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                 inet_proto_csum_replace2(check, skb,
 149                                          htons(oldlen), htons(datalen), true);
 150 }
 151
 152 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 153 static int nf_nat_ipv6_nlattr_to_range(struct nlattr *tb[],
 154                                        struct nf_nat_range2 *range)
 155 {
 156         if (tb[CTA_NAT_V6_MINIP]) {
 157                 nla_memcpy(&range->min_addr.ip6, tb[CTA_NAT_V6_MINIP],
 158                            sizeof(struct in6_addr));
 159                 range->flags |= NF_NAT_RANGE_MAP_IPS;
 160         }
 161
 162         if (tb[CTA_NAT_V6_MAXIP])
 163                 nla_memcpy(&range->max_addr.ip6, tb[CTA_NAT_V6_MAXIP],
 164                            sizeof(struct in6_addr));
 165         else
 166                 range->max_addr = range->min_addr;
 167
 168         return 0;
 169 }
 170 #endif
 171
 172 static const struct nf_nat_l3proto nf_nat_l3proto_ipv6 = {
 173         .l3proto                = NFPROTO_IPV6,
 174         .secure_port            = nf_nat_ipv6_secure_port,
 175         .in_range               = nf_nat_ipv6_in_range,
 176         .manip_pkt              = nf_nat_ipv6_manip_pkt,
 177         .csum_update            = nf_nat_ipv6_csum_update,
 178         .csum_recalc            = nf_nat_ipv6_csum_recalc,
 179 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 180         .nlattr_to_range        = nf_nat_ipv6_nlattr_to_range,
 181 #endif
 182 #ifdef CONFIG_XFRM
 183         .decode_session = nf_nat_ipv6_decode_session,
 184 #endif
 185 };
 186
 187 int nf_nat_icmpv6_reply_translation(struct sk_buff *skb,
 188                                     struct nf_conn *ct,
 189                                     enum ip_conntrack_info ctinfo,
 190                                     unsigned int hooknum,
 191                                     unsigned int hdrlen)
 192 {
 193         struct {
 194                 struct icmp6hdr icmp6;
 195                 struct ipv6hdr  ip6;
 196         } *inside;
 197         enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 198         enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
 199         const struct nf_nat_l4proto *l4proto;
 200         struct nf_conntrack_tuple target;
 201         unsigned long statusbit;
 202
 203         WARN_ON(ctinfo != IP_CT_RELATED && ctinfo != IP_CT_RELATED_REPLY);
 204
 205         if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
 206                 return 0;
 207         if (nf_ip6_checksum(skb, hooknum, hdrlen, IPPROTO_ICMPV6))
 208                 return 0;
 209
 210         inside = (void *)skb->data + hdrlen;
 211         if (inside->icmp6.icmp6_type == NDISC_REDIRECT) {
 212                 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
 213                         return 0;
 214                 if (ct->status & IPS_NAT_MASK)
 215                         return 0;
 216         }
 217
 218         if (manip == NF_NAT_MANIP_SRC)
 219                 statusbit = IPS_SRC_NAT;
 220         else
 221                 statusbit = IPS_DST_NAT;
 222
 223         /* Invert if this is reply direction */
 224         if (dir == IP_CT_DIR_REPLY)
 225                 statusbit ^= IPS_NAT_MASK;
 226
 227         if (!(ct->status & statusbit))
 228                 return 1;
 229
 230         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr);
 231         if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6),
 232                                    l4proto, &ct->tuplehash[!dir].tuple, !manip))
 233                 return 0;
 234
 235         if (skb->ip_summed != CHECKSUM_PARTIAL) {
 236                 struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 237                 inside = (void *)skb->data + hdrlen;
 238                 inside->icmp6.icmp6_cksum = 0;
 239                 inside->icmp6.icmp6_cksum =
 240                         csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 241                                         skb->len - hdrlen, IPPROTO_ICMPV6,
 242                                         skb_checksum(skb, hdrlen,
 243                                                      skb->len - hdrlen, 0));
 244         }
 245
 246         nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
 247         l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6);
 248         if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip))
 249                 return 0;
 250
 251         return 1;
 252 }
 253 EXPORT_SYMBOL_GPL(nf_nat_icmpv6_reply_translation);
 254
 255 static unsigned int
 256 nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
 257                const struct nf_hook_state *state)
 258 {
 259         struct nf_conn *ct;
 260         enum ip_conntrack_info ctinfo;
 261         __be16 frag_off;
 262         int hdrlen;
 263         u8 nexthdr;
 264
 265         ct = nf_ct_get(skb, &ctinfo);
 266         /* Can't track?  It's not due to stress, or conntrack would
 267          * have dropped it.  Hence it's the user's responsibilty to
 268          * packet filter it out, or implement conntrack/NAT for that
 269          * protocol. 8) --RR
 270          */
 271         if (!ct)
 272                 return NF_ACCEPT;
 273
 274         if (ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY) {
 275                 nexthdr = ipv6_hdr(skb)->nexthdr;
 276                 hdrlen = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr),
 277                                           &nexthdr, &frag_off);
 278
 279                 if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
 280                         if (!nf_nat_icmpv6_reply_translation(skb, ct, ctinfo,
 281                                                              state->hook,
 282                                                              hdrlen))
 283                                 return NF_DROP;
 284                         else
 285                                 return NF_ACCEPT;
 286                 }
 287         }
 288
 289         return nf_nat_inet_fn(priv, skb, state);
 290 }
 291
 292 static unsigned int
 293 nf_nat_ipv6_in(void *priv, struct sk_buff *skb,
 294                const struct nf_hook_state *state)
 295 {
 296         unsigned int ret;
 297         struct in6_addr daddr = ipv6_hdr(skb)->daddr;
 298
 299         ret = nf_nat_ipv6_fn(priv, skb, state);
 300         if (ret != NF_DROP && ret != NF_STOLEN &&
 301             ipv6_addr_cmp(&daddr, &ipv6_hdr(skb)->daddr))
 302                 skb_dst_drop(skb);
 303
 304         return ret;
 305 }
 306
 307 static unsigned int
 308 nf_nat_ipv6_out(void *priv, struct sk_buff *skb,
 309                 const struct nf_hook_state *state)
 310 {
 311 #ifdef CONFIG_XFRM
 312         const struct nf_conn *ct;
 313         enum ip_conntrack_info ctinfo;
 314         int err;
 315 #endif
 316         unsigned int ret;
 317
 318         ret = nf_nat_ipv6_fn(priv, skb, state);
 319 #ifdef CONFIG_XFRM
 320         if (ret != NF_DROP && ret != NF_STOLEN &&
 321             !(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 322             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 323                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 324
 325                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.src.u3,
 326                                       &ct->tuplehash[!dir].tuple.dst.u3) ||
 327                     (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 328                      ct->tuplehash[dir].tuple.src.u.all !=
 329                      ct->tuplehash[!dir].tuple.dst.u.all)) {
 330                         err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 331                         if (err < 0)
 332                                 ret = NF_DROP_ERR(err);
 333                 }
 334         }
 335 #endif
 336         return ret;
 337 }
 338
 339 static unsigned int
 340 nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 341                      const struct nf_hook_state *state)
 342 {
 343         const struct nf_conn *ct;
 344         enum ip_conntrack_info ctinfo;
 345         unsigned int ret;
 346         int err;
 347
 348         ret = nf_nat_ipv6_fn(priv, skb, state);
 349         if (ret != NF_DROP && ret != NF_STOLEN &&
 350             (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
 351                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
 352
 353                 if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
 354                                       &ct->tuplehash[!dir].tuple.src.u3)) {
 355                         err = ip6_route_me_harder(state->net, state->sk, skb);
 356                         if (err < 0)
 357                                 ret = NF_DROP_ERR(err);
 358                 }
 359 #ifdef CONFIG_XFRM
 360                 else if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
 361                          ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMPV6 &&
 362                          ct->tuplehash[dir].tuple.dst.u.all !=
 363                          ct->tuplehash[!dir].tuple.src.u.all) {
 364                         err = nf_xfrm_me_harder(state->net, skb, AF_INET6);
 365                         if (err < 0)
 366                                 ret = NF_DROP_ERR(err);
 367                 }
 368 #endif
 369         }
 370         return ret;
 371 }
 372
 373 static const struct nf_hook_ops nf_nat_ipv6_ops[] = {
 374         /* Before packet filtering, change destination */
 375         {
 376                 .hook           = nf_nat_ipv6_in,
 377                 .pf             = NFPROTO_IPV6,
 378                 .hooknum        = NF_INET_PRE_ROUTING,
 379                 .priority       = NF_IP6_PRI_NAT_DST,
 380         },
 381         /* After packet filtering, change source */
 382         {
 383                 .hook           = nf_nat_ipv6_out,
 384                 .pf             = NFPROTO_IPV6,
 385                 .hooknum        = NF_INET_POST_ROUTING,
 386                 .priority       = NF_IP6_PRI_NAT_SRC,
 387         },
 388         /* Before packet filtering, change destination */
 389         {
 390                 .hook           = nf_nat_ipv6_local_fn,
 391                 .pf             = NFPROTO_IPV6,
 392                 .hooknum        = NF_INET_LOCAL_OUT,
 393                 .priority       = NF_IP6_PRI_NAT_DST,
 394         },
 395         /* After packet filtering, change source */
 396         {
 397                 .hook           = nf_nat_ipv6_fn,
 398                 .pf             = NFPROTO_IPV6,
 399                 .hooknum        = NF_INET_LOCAL_IN,
 400                 .priority       = NF_IP6_PRI_NAT_SRC,
 401         },
 402 };
 403
 404 int nf_nat_l3proto_ipv6_register_fn(struct net *net, const struct nf_hook_ops *ops)
 405 {
 406         return nf_nat_register_fn(net, ops, nf_nat_ipv6_ops, ARRAY_SIZE(nf_nat_ipv6_ops));
 407 }
 408 EXPORT_SYMBOL_GPL(nf_nat_l3proto_ipv6_register_fn);
 409
 410 void nf_nat_l3proto_ipv6_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
 411 {
 412         nf_nat_unregister_fn(net, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
 413 }
 414 EXPORT_SYMBOL_GPL(nf_nat_l3proto_ipv6_unregister_fn);
 415
 416 static int __init nf_nat_l3proto_ipv6_init(void)
 417 {
 418         int err;
 419
 420         err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 421         if (err < 0)
 422                 goto err1;
 423         err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv6);
 424         if (err < 0)
 425                 goto err2;
 426         return err;
 427
 428 err2:
 429         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 430 err1:
 431         return err;
 432 }
 433
 434 static void __exit nf_nat_l3proto_ipv6_exit(void)
 435 {
 436         nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv6);
 437         nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_icmpv6);
 438 }
 439
 440 MODULE_LICENSE("GPL");
 441 MODULE_ALIAS("nf-nat-" __stringify(AF_INET6));
 442
 443 module_init(nf_nat_l3proto_ipv6_init);
 444 module_exit(nf_nat_l3proto_ipv6_exit);