net/netfilter/xt_socket.c

   1 /*
   2  * Transparent proxy support for Linux/iptables
   3  *
   4  * Copyright (C) 2007-2008 BalaBit IT Ltd.
   5  * Author: Krisztian Kovacs
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  */
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/netfilter/x_tables.h>
  16 #include <linux/netfilter_ipv4/ip_tables.h>
  17 #include <net/tcp.h>
  18 #include <net/udp.h>
  19 #include <net/icmp.h>
  20 #include <net/sock.h>
  21 #include <net/inet_sock.h>
  22 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  23
  24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  25 #define XT_SOCKET_HAVE_IPV6 1
  26 #include <linux/netfilter_ipv6/ip6_tables.h>
  27 #include <net/inet6_hashtables.h>
  28 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  29 #endif
  30
  31 #include <linux/netfilter/xt_socket.h>
  32
  33 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  34 #define XT_SOCKET_HAVE_CONNTRACK 1
  35 #include <net/netfilter/nf_conntrack.h>
  36 #endif
  37
  38 static int
  39 extract_icmp4_fields(const struct sk_buff *skb,
  40                     u8 *protocol,
  41                     __be32 *raddr,
  42                     __be32 *laddr,
  43                     __be16 *rport,
  44                     __be16 *lport)
  45 {
  46         unsigned int outside_hdrlen = ip_hdrlen(skb);
  47         struct iphdr *inside_iph, _inside_iph;
  48         struct icmphdr *icmph, _icmph;
  49         __be16 *ports, _ports[2];
  50
  51         icmph = skb_header_pointer(skb, outside_hdrlen,
  52                                    sizeof(_icmph), &_icmph);
  53         if (icmph == NULL)
  54                 return 1;
  55
  56         switch (icmph->type) {
  57         case ICMP_DEST_UNREACH:
  58         case ICMP_SOURCE_QUENCH:
  59         case ICMP_REDIRECT:
  60         case ICMP_TIME_EXCEEDED:
  61         case ICMP_PARAMETERPROB:
  62                 break;
  63         default:
  64                 return 1;
  65         }
  66
  67         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  68                                         sizeof(struct icmphdr),
  69                                         sizeof(_inside_iph), &_inside_iph);
  70         if (inside_iph == NULL)
  71                 return 1;
  72
  73         if (inside_iph->protocol != IPPROTO_TCP &&
  74             inside_iph->protocol != IPPROTO_UDP)
  75                 return 1;
  76
  77         ports = skb_header_pointer(skb, outside_hdrlen +
  78                                    sizeof(struct icmphdr) +
  79                                    (inside_iph->ihl << 2),
  80                                    sizeof(_ports), &_ports);
  81         if (ports == NULL)
  82                 return 1;
  83
  84         /* the inside IP packet is the one quoted from our side, thus
  85          * its saddr is the local address */
  86         *protocol = inside_iph->protocol;
  87         *laddr = inside_iph->saddr;
  88         *lport = ports[0];
  89         *raddr = inside_iph->daddr;
  90         *rport = ports[1];
  91
  92         return 0;
  93 }
  94
  95 /* "socket" match based redirection (no specific rule)
  96  * ===================================================
  97  *
  98  * There are connections with dynamic endpoints (e.g. FTP data
  99  * connection) that the user is unable to add explicit rules
 100  * for. These are taken care of by a generic "socket" rule. It is
 101  * assumed that the proxy application is trusted to open such
 102  * connections without explicit iptables rule (except of course the
 103  * generic 'socket' rule). In this case the following sockets are
 104  * matched in preference order:
 105  *
 106  *   - match: if there's a fully established connection matching the
 107  *     _packet_ tuple
 108  *
 109  *   - match: if there's a non-zero bound listener (possibly with a
 110  *     non-local address) We don't accept zero-bound listeners, since
 111  *     then local services could intercept traffic going through the
 112  *     box.
 113  */
 114 static struct sock *
 115 xt_socket_get_sock_v4(struct net *net, const u8 protocol,
 116                       const __be32 saddr, const __be32 daddr,
 117                       const __be16 sport, const __be16 dport,
 118                       const struct net_device *in)
 119 {
 120         switch (protocol) {
 121         case IPPROTO_TCP:
 122                 return __inet_lookup(net, &tcp_hashinfo,
 123                                      saddr, sport, daddr, dport,
 124                                      in->ifindex);
 125         case IPPROTO_UDP:
 126                 return udp4_lib_lookup(net, saddr, sport, daddr, dport,
 127                                        in->ifindex);
 128         }
 129         return NULL;
 130 }
 131
 132 static bool xt_socket_sk_is_transparent(struct sock *sk)
 133 {
 134         switch (sk->sk_state) {
 135         case TCP_TIME_WAIT:
 136                 return inet_twsk(sk)->tw_transparent;
 137
 138         case TCP_NEW_SYN_RECV:
 139                 return inet_rsk(inet_reqsk(sk))->no_srccheck;
 140
 141         default:
 142                 return inet_sk(sk)->transparent;
 143         }
 144 }
 145
 146 struct sock *xt_socket_lookup_slow_v4(struct net *net,
 147                                              const struct sk_buff *skb,
 148                                              const struct net_device *indev)
 149 {
 150         const struct iphdr *iph = ip_hdr(skb);
 151         struct sock *sk = skb->sk;
 152         __be32 uninitialized_var(daddr), uninitialized_var(saddr);
 153         __be16 uninitialized_var(dport), uninitialized_var(sport);
 154         u8 uninitialized_var(protocol);
 155 #ifdef XT_SOCKET_HAVE_CONNTRACK
 156         struct nf_conn const *ct;
 157         enum ip_conntrack_info ctinfo;
 158 #endif
 159
 160         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 161                 struct udphdr _hdr, *hp;
 162
 163                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 164                                         sizeof(_hdr), &_hdr);
 165                 if (hp == NULL)
 166                         return NULL;
 167
 168                 protocol = iph->protocol;
 169                 saddr = iph->saddr;
 170                 sport = hp->source;
 171                 daddr = iph->daddr;
 172                 dport = hp->dest;
 173
 174         } else if (iph->protocol == IPPROTO_ICMP) {
 175                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 176                                          &sport, &dport))
 177                         return NULL;
 178         } else {
 179                 return NULL;
 180         }
 181
 182 #ifdef XT_SOCKET_HAVE_CONNTRACK
 183         /* Do the lookup with the original socket address in
 184          * case this is a reply packet of an established
 185          * SNAT-ted connection.
 186          */
 187         ct = nf_ct_get(skb, &ctinfo);
 188         if (ct && !nf_ct_is_untracked(ct) &&
 189             ((iph->protocol != IPPROTO_ICMP &&
 190               ctinfo == IP_CT_ESTABLISHED_REPLY) ||
 191              (iph->protocol == IPPROTO_ICMP &&
 192               ctinfo == IP_CT_RELATED_REPLY)) &&
 193             (ct->status & IPS_SRC_NAT_DONE)) {
 194
 195                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 196                 dport = (iph->protocol == IPPROTO_TCP) ?
 197                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 198                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 199         }
 200 #endif
 201
 202         if (sk)
 203                 atomic_inc(&sk->sk_refcnt);
 204         else
 205                 sk = xt_socket_get_sock_v4(dev_net(skb->dev), protocol,
 206                                            saddr, daddr, sport, dport,
 207                                            indev);
 208
 209         return sk;
 210 }
 211 EXPORT_SYMBOL(xt_socket_lookup_slow_v4);
 212
 213 static bool
 214 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 215              const struct xt_socket_mtinfo1 *info)
 216 {
 217         struct sk_buff *pskb = (struct sk_buff *)skb;
 218         struct sock *sk = skb->sk;
 219
 220         if (!sk)
 221                 sk = xt_socket_lookup_slow_v4(par->net, skb, par->in);
 222         if (sk) {
 223                 bool wildcard;
 224                 bool transparent = true;
 225
 226                 /* Ignore sockets listening on INADDR_ANY,
 227                  * unless XT_SOCKET_NOWILDCARD is set
 228                  */
 229                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 230                             sk_fullsock(sk) &&
 231                             inet_sk(sk)->inet_rcv_saddr == 0);
 232
 233                 /* Ignore non-transparent sockets,
 234                  * if XT_SOCKET_TRANSPARENT is used
 235                  */
 236                 if (info->flags & XT_SOCKET_TRANSPARENT)
 237                         transparent = xt_socket_sk_is_transparent(sk);
 238
 239                 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
 240                     transparent)
 241                         pskb->mark = sk->sk_mark;
 242
 243                 sock_gen_put(sk);
 244
 245                 if (wildcard || !transparent)
 246                         sk = NULL;
 247         }
 248
 249         return sk != NULL;
 250 }
 251
 252 static bool
 253 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 254 {
 255         static struct xt_socket_mtinfo1 xt_info_v0 = {
 256                 .flags = 0,
 257         };
 258
 259         return socket_match(skb, par, &xt_info_v0);
 260 }
 261
 262 static bool
 263 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 264 {
 265         return socket_match(skb, par, par->matchinfo);
 266 }
 267
 268 #ifdef XT_SOCKET_HAVE_IPV6
 269
 270 static int
 271 extract_icmp6_fields(const struct sk_buff *skb,
 272                      unsigned int outside_hdrlen,
 273                      int *protocol,
 274                      const struct in6_addr **raddr,
 275                      const struct in6_addr **laddr,
 276                      __be16 *rport,
 277                      __be16 *lport,
 278                      struct ipv6hdr *ipv6_var)
 279 {
 280         const struct ipv6hdr *inside_iph;
 281         struct icmp6hdr *icmph, _icmph;
 282         __be16 *ports, _ports[2];
 283         u8 inside_nexthdr;
 284         __be16 inside_fragoff;
 285         int inside_hdrlen;
 286
 287         icmph = skb_header_pointer(skb, outside_hdrlen,
 288                                    sizeof(_icmph), &_icmph);
 289         if (icmph == NULL)
 290                 return 1;
 291
 292         if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 293                 return 1;
 294
 295         inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph),
 296                                         sizeof(*ipv6_var), ipv6_var);
 297         if (inside_iph == NULL)
 298                 return 1;
 299         inside_nexthdr = inside_iph->nexthdr;
 300
 301         inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) +
 302                                               sizeof(*ipv6_var),
 303                                          &inside_nexthdr, &inside_fragoff);
 304         if (inside_hdrlen < 0)
 305                 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 306
 307         if (inside_nexthdr != IPPROTO_TCP &&
 308             inside_nexthdr != IPPROTO_UDP)
 309                 return 1;
 310
 311         ports = skb_header_pointer(skb, inside_hdrlen,
 312                                    sizeof(_ports), &_ports);
 313         if (ports == NULL)
 314                 return 1;
 315
 316         /* the inside IP packet is the one quoted from our side, thus
 317          * its saddr is the local address */
 318         *protocol = inside_nexthdr;
 319         *laddr = &inside_iph->saddr;
 320         *lport = ports[0];
 321         *raddr = &inside_iph->daddr;
 322         *rport = ports[1];
 323
 324         return 0;
 325 }
 326
 327 static struct sock *
 328 xt_socket_get_sock_v6(struct net *net, const u8 protocol,
 329                       const struct in6_addr *saddr, const struct in6_addr *daddr,
 330                       const __be16 sport, const __be16 dport,
 331                       const struct net_device *in)
 332 {
 333         switch (protocol) {
 334         case IPPROTO_TCP:
 335                 return inet6_lookup(net, &tcp_hashinfo,
 336                                     saddr, sport, daddr, dport,
 337                                     in->ifindex);
 338         case IPPROTO_UDP:
 339                 return udp6_lib_lookup(net, saddr, sport, daddr, dport,
 340                                        in->ifindex);
 341         }
 342
 343         return NULL;
 344 }
 345
 346 struct sock *xt_socket_lookup_slow_v6(struct net *net,
 347                                              const struct sk_buff *skb,
 348                                              const struct net_device *indev)
 349 {
 350         struct sock *sk = skb->sk;
 351         __be16 uninitialized_var(dport), uninitialized_var(sport);
 352         const struct in6_addr *daddr = NULL, *saddr = NULL;
 353         struct ipv6hdr *iph = ipv6_hdr(skb);
 354         int thoff = 0, tproto;
 355
 356         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 357         if (tproto < 0) {
 358                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 359                 return NULL;
 360         }
 361
 362         if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 363                 struct udphdr _hdr, *hp;
 364
 365                 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
 366                 if (hp == NULL)
 367                         return NULL;
 368
 369                 saddr = &iph->saddr;
 370                 sport = hp->source;
 371                 daddr = &iph->daddr;
 372                 dport = hp->dest;
 373
 374         } else if (tproto == IPPROTO_ICMPV6) {
 375                 struct ipv6hdr ipv6_var;
 376
 377                 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 378                                          &sport, &dport, &ipv6_var))
 379                         return NULL;
 380         } else {
 381                 return NULL;
 382         }
 383
 384         if (sk)
 385                 atomic_inc(&sk->sk_refcnt);
 386         else
 387                 sk = xt_socket_get_sock_v6(dev_net(skb->dev), tproto,
 388                                            saddr, daddr, sport, dport,
 389                                            indev);
 390
 391         return sk;
 392 }
 393 EXPORT_SYMBOL(xt_socket_lookup_slow_v6);
 394
 395 static bool
 396 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 397 {
 398         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 399         struct sk_buff *pskb = (struct sk_buff *)skb;
 400         struct sock *sk = skb->sk;
 401
 402         if (!sk)
 403                 sk = xt_socket_lookup_slow_v6(par->net, skb, par->in);
 404         if (sk) {
 405                 bool wildcard;
 406                 bool transparent = true;
 407
 408                 /* Ignore sockets listening on INADDR_ANY
 409                  * unless XT_SOCKET_NOWILDCARD is set
 410                  */
 411                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 412                             sk_fullsock(sk) &&
 413                             ipv6_addr_any(&sk->sk_v6_rcv_saddr));
 414
 415                 /* Ignore non-transparent sockets,
 416                  * if XT_SOCKET_TRANSPARENT is used
 417                  */
 418                 if (info->flags & XT_SOCKET_TRANSPARENT)
 419                         transparent = xt_socket_sk_is_transparent(sk);
 420
 421                 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
 422                     transparent)
 423                         pskb->mark = sk->sk_mark;
 424
 425                 if (sk != skb->sk)
 426                         sock_gen_put(sk);
 427
 428                 if (wildcard || !transparent)
 429                         sk = NULL;
 430         }
 431
 432         return sk != NULL;
 433 }
 434 #endif
 435
 436 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
 437 {
 438         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 439
 440         if (info->flags & ~XT_SOCKET_FLAGS_V1) {
 441                 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
 442                 return -EINVAL;
 443         }
 444         return 0;
 445 }
 446
 447 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
 448 {
 449         const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
 450
 451         if (info->flags & ~XT_SOCKET_FLAGS_V2) {
 452                 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
 453                 return -EINVAL;
 454         }
 455         return 0;
 456 }
 457
 458 static int socket_mt_v3_check(const struct xt_mtchk_param *par)
 459 {
 460         const struct xt_socket_mtinfo3 *info =
 461                                     (struct xt_socket_mtinfo3 *)par->matchinfo;
 462
 463         if (info->flags & ~XT_SOCKET_FLAGS_V3) {
 464                 pr_info("unknown flags 0x%x\n",
 465                         info->flags & ~XT_SOCKET_FLAGS_V3);
 466                 return -EINVAL;
 467         }
 468         return 0;
 469 }
 470
 471 static struct xt_match socket_mt_reg[] __read_mostly = {
 472         {
 473                 .name           = "socket",
 474                 .revision       = 0,
 475                 .family         = NFPROTO_IPV4,
 476                 .match          = socket_mt4_v0,
 477                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 478                                   (1 << NF_INET_LOCAL_IN),
 479                 .me             = THIS_MODULE,
 480         },
 481         {
 482                 .name           = "socket",
 483                 .revision       = 1,
 484                 .family         = NFPROTO_IPV4,
 485                 .match          = socket_mt4_v1_v2_v3,
 486                 .checkentry     = socket_mt_v1_check,
 487                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 488                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 489                                   (1 << NF_INET_LOCAL_IN),
 490                 .me             = THIS_MODULE,
 491         },
 492 #ifdef XT_SOCKET_HAVE_IPV6
 493         {
 494                 .name           = "socket",
 495                 .revision       = 1,
 496                 .family         = NFPROTO_IPV6,
 497                 .match          = socket_mt6_v1_v2_v3,
 498                 .checkentry     = socket_mt_v1_check,
 499                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 500                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 501                                   (1 << NF_INET_LOCAL_IN),
 502                 .me             = THIS_MODULE,
 503         },
 504 #endif
 505         {
 506                 .name           = "socket",
 507                 .revision       = 2,
 508                 .family         = NFPROTO_IPV4,
 509                 .match          = socket_mt4_v1_v2_v3,
 510                 .checkentry     = socket_mt_v2_check,
 511                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 512                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 513                                   (1 << NF_INET_LOCAL_IN),
 514                 .me             = THIS_MODULE,
 515         },
 516 #ifdef XT_SOCKET_HAVE_IPV6
 517         {
 518                 .name           = "socket",
 519                 .revision       = 2,
 520                 .family         = NFPROTO_IPV6,
 521                 .match          = socket_mt6_v1_v2_v3,
 522                 .checkentry     = socket_mt_v2_check,
 523                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 524                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 525                                   (1 << NF_INET_LOCAL_IN),
 526                 .me             = THIS_MODULE,
 527         },
 528 #endif
 529         {
 530                 .name           = "socket",
 531                 .revision       = 3,
 532                 .family         = NFPROTO_IPV4,
 533                 .match          = socket_mt4_v1_v2_v3,
 534                 .checkentry     = socket_mt_v3_check,
 535                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 536                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 537                                   (1 << NF_INET_LOCAL_IN),
 538                 .me             = THIS_MODULE,
 539         },
 540 #ifdef XT_SOCKET_HAVE_IPV6
 541         {
 542                 .name           = "socket",
 543                 .revision       = 3,
 544                 .family         = NFPROTO_IPV6,
 545                 .match          = socket_mt6_v1_v2_v3,
 546                 .checkentry     = socket_mt_v3_check,
 547                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 548                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 549                                   (1 << NF_INET_LOCAL_IN),
 550                 .me             = THIS_MODULE,
 551         },
 552 #endif
 553 };
 554
 555 static int __init socket_mt_init(void)
 556 {
 557         nf_defrag_ipv4_enable();
 558 #ifdef XT_SOCKET_HAVE_IPV6
 559         nf_defrag_ipv6_enable();
 560 #endif
 561
 562         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 563 }
 564
 565 static void __exit socket_mt_exit(void)
 566 {
 567         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 568 }
 569
 570 module_init(socket_mt_init);
 571 module_exit(socket_mt_exit);
 572
 573 MODULE_LICENSE("GPL");
 574 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 575 MODULE_DESCRIPTION("x_tables socket match module");
 576 MODULE_ALIAS("ipt_socket");
 577 MODULE_ALIAS("ip6t_socket");