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/nf_tproxy_core.h>
  23 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  24
  25 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
  26 #define XT_SOCKET_HAVE_IPV6 1
  27 #include <linux/netfilter_ipv6/ip6_tables.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 void
  39 xt_socket_put_sk(struct sock *sk)
  40 {
  41         if (sk->sk_state == TCP_TIME_WAIT)
  42                 inet_twsk_put(inet_twsk(sk));
  43         else
  44                 sock_put(sk);
  45 }
  46
  47 static int
  48 extract_icmp4_fields(const struct sk_buff *skb,
  49                     u8 *protocol,
  50                     __be32 *raddr,
  51                     __be32 *laddr,
  52                     __be16 *rport,
  53                     __be16 *lport)
  54 {
  55         unsigned int outside_hdrlen = ip_hdrlen(skb);
  56         struct iphdr *inside_iph, _inside_iph;
  57         struct icmphdr *icmph, _icmph;
  58         __be16 *ports, _ports[2];
  59
  60         icmph = skb_header_pointer(skb, outside_hdrlen,
  61                                    sizeof(_icmph), &_icmph);
  62         if (icmph == NULL)
  63                 return 1;
  64
  65         switch (icmph->type) {
  66         case ICMP_DEST_UNREACH:
  67         case ICMP_SOURCE_QUENCH:
  68         case ICMP_REDIRECT:
  69         case ICMP_TIME_EXCEEDED:
  70         case ICMP_PARAMETERPROB:
  71                 break;
  72         default:
  73                 return 1;
  74         }
  75
  76         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  77                                         sizeof(struct icmphdr),
  78                                         sizeof(_inside_iph), &_inside_iph);
  79         if (inside_iph == NULL)
  80                 return 1;
  81
  82         if (inside_iph->protocol != IPPROTO_TCP &&
  83             inside_iph->protocol != IPPROTO_UDP)
  84                 return 1;
  85
  86         ports = skb_header_pointer(skb, outside_hdrlen +
  87                                    sizeof(struct icmphdr) +
  88                                    (inside_iph->ihl << 2),
  89                                    sizeof(_ports), &_ports);
  90         if (ports == NULL)
  91                 return 1;
  92
  93         /* the inside IP packet is the one quoted from our side, thus
  94          * its saddr is the local address */
  95         *protocol = inside_iph->protocol;
  96         *laddr = inside_iph->saddr;
  97         *lport = ports[0];
  98         *raddr = inside_iph->daddr;
  99         *rport = ports[1];
 100
 101         return 0;
 102 }
 103
 104 static bool
 105 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 106              const struct xt_socket_mtinfo1 *info)
 107 {
 108         const struct iphdr *iph = ip_hdr(skb);
 109         struct udphdr _hdr, *hp = NULL;
 110         struct sock *sk = skb->sk;
 111         __be32 uninitialized_var(daddr), uninitialized_var(saddr);
 112         __be16 uninitialized_var(dport), uninitialized_var(sport);
 113         u8 uninitialized_var(protocol);
 114 #ifdef XT_SOCKET_HAVE_CONNTRACK
 115         struct nf_conn const *ct;
 116         enum ip_conntrack_info ctinfo;
 117 #endif
 118
 119         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 120                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 121                                         sizeof(_hdr), &_hdr);
 122                 if (hp == NULL)
 123                         return false;
 124
 125                 protocol = iph->protocol;
 126                 saddr = iph->saddr;
 127                 sport = hp->source;
 128                 daddr = iph->daddr;
 129                 dport = hp->dest;
 130
 131         } else if (iph->protocol == IPPROTO_ICMP) {
 132                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 133                                         &sport, &dport))
 134                         return false;
 135         } else {
 136                 return false;
 137         }
 138
 139 #ifdef XT_SOCKET_HAVE_CONNTRACK
 140         /* Do the lookup with the original socket address in case this is a
 141          * reply packet of an established SNAT-ted connection. */
 142
 143         ct = nf_ct_get(skb, &ctinfo);
 144         if (ct && !nf_ct_is_untracked(ct) &&
 145             ((iph->protocol != IPPROTO_ICMP &&
 146               ctinfo == IP_CT_ESTABLISHED_REPLY) ||
 147              (iph->protocol == IPPROTO_ICMP &&
 148               ctinfo == IP_CT_RELATED_REPLY)) &&
 149             (ct->status & IPS_SRC_NAT_DONE)) {
 150
 151                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 152                 dport = (iph->protocol == IPPROTO_TCP) ?
 153                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 154                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 155         }
 156 #endif
 157
 158         if (!sk)
 159                 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 160                                            saddr, daddr, sport, dport,
 161                                            par->in, NFT_LOOKUP_ANY);
 162         if (sk) {
 163                 bool wildcard;
 164                 bool transparent = true;
 165
 166                 /* Ignore sockets listening on INADDR_ANY,
 167                  * unless XT_SOCKET_NOWILDCARD is set
 168                  */
 169                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 170                             sk->sk_state != TCP_TIME_WAIT &&
 171                             inet_sk(sk)->inet_rcv_saddr == 0);
 172
 173                 /* Ignore non-transparent sockets,
 174                    if XT_SOCKET_TRANSPARENT is used */
 175                 if (info->flags & XT_SOCKET_TRANSPARENT)
 176                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 177                                         inet_sk(sk)->transparent) ||
 178                                        (sk->sk_state == TCP_TIME_WAIT &&
 179                                         inet_twsk(sk)->tw_transparent));
 180
 181                 if (sk != skb->sk)
 182                         xt_socket_put_sk(sk);
 183
 184                 if (wildcard || !transparent)
 185                         sk = NULL;
 186         }
 187
 188         pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 189                  protocol, &saddr, ntohs(sport),
 190                  &daddr, ntohs(dport),
 191                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 192
 193         return (sk != NULL);
 194 }
 195
 196 static bool
 197 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 198 {
 199         static struct xt_socket_mtinfo1 xt_info_v0 = {
 200                 .flags = 0,
 201         };
 202
 203         return socket_match(skb, par, &xt_info_v0);
 204 }
 205
 206 static bool
 207 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
 208 {
 209         return socket_match(skb, par, par->matchinfo);
 210 }
 211
 212 #ifdef XT_SOCKET_HAVE_IPV6
 213
 214 static int
 215 extract_icmp6_fields(const struct sk_buff *skb,
 216                      unsigned int outside_hdrlen,
 217                      int *protocol,
 218                      struct in6_addr **raddr,
 219                      struct in6_addr **laddr,
 220                      __be16 *rport,
 221                      __be16 *lport)
 222 {
 223         struct ipv6hdr *inside_iph, _inside_iph;
 224         struct icmp6hdr *icmph, _icmph;
 225         __be16 *ports, _ports[2];
 226         u8 inside_nexthdr;
 227         __be16 inside_fragoff;
 228         int inside_hdrlen;
 229
 230         icmph = skb_header_pointer(skb, outside_hdrlen,
 231                                    sizeof(_icmph), &_icmph);
 232         if (icmph == NULL)
 233                 return 1;
 234
 235         if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 236                 return 1;
 237
 238         inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 239         if (inside_iph == NULL)
 240                 return 1;
 241         inside_nexthdr = inside_iph->nexthdr;
 242
 243         inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
 244                                          &inside_nexthdr, &inside_fragoff);
 245         if (inside_hdrlen < 0)
 246                 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 247
 248         if (inside_nexthdr != IPPROTO_TCP &&
 249             inside_nexthdr != IPPROTO_UDP)
 250                 return 1;
 251
 252         ports = skb_header_pointer(skb, inside_hdrlen,
 253                                    sizeof(_ports), &_ports);
 254         if (ports == NULL)
 255                 return 1;
 256
 257         /* the inside IP packet is the one quoted from our side, thus
 258          * its saddr is the local address */
 259         *protocol = inside_nexthdr;
 260         *laddr = &inside_iph->saddr;
 261         *lport = ports[0];
 262         *raddr = &inside_iph->daddr;
 263         *rport = ports[1];
 264
 265         return 0;
 266 }
 267
 268 static bool
 269 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
 270 {
 271         struct ipv6hdr *iph = ipv6_hdr(skb);
 272         struct udphdr _hdr, *hp = NULL;
 273         struct sock *sk = skb->sk;
 274         struct in6_addr *daddr = NULL, *saddr = NULL;
 275         __be16 uninitialized_var(dport), uninitialized_var(sport);
 276         int thoff = 0, uninitialized_var(tproto);
 277         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 278
 279         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
 280         if (tproto < 0) {
 281                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 282                 return NF_DROP;
 283         }
 284
 285         if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 286                 hp = skb_header_pointer(skb, thoff,
 287                                         sizeof(_hdr), &_hdr);
 288                 if (hp == NULL)
 289                         return false;
 290
 291                 saddr = &iph->saddr;
 292                 sport = hp->source;
 293                 daddr = &iph->daddr;
 294                 dport = hp->dest;
 295
 296         } else if (tproto == IPPROTO_ICMPV6) {
 297                 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 298                                          &sport, &dport))
 299                         return false;
 300         } else {
 301                 return false;
 302         }
 303
 304         if (!sk)
 305                 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 306                                            saddr, daddr, sport, dport,
 307                                            par->in, NFT_LOOKUP_ANY);
 308         if (sk) {
 309                 bool wildcard;
 310                 bool transparent = true;
 311
 312                 /* Ignore sockets listening on INADDR_ANY
 313                  * unless XT_SOCKET_NOWILDCARD is set
 314                  */
 315                 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
 316                             sk->sk_state != TCP_TIME_WAIT &&
 317                             ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 318
 319                 /* Ignore non-transparent sockets,
 320                    if XT_SOCKET_TRANSPARENT is used */
 321                 if (info->flags & XT_SOCKET_TRANSPARENT)
 322                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 323                                         inet_sk(sk)->transparent) ||
 324                                        (sk->sk_state == TCP_TIME_WAIT &&
 325                                         inet_twsk(sk)->tw_transparent));
 326
 327                 if (sk != skb->sk)
 328                         xt_socket_put_sk(sk);
 329
 330                 if (wildcard || !transparent)
 331                         sk = NULL;
 332         }
 333
 334         pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
 335                  "(orig %pI6:%hu) sock %p\n",
 336                  tproto, saddr, ntohs(sport),
 337                  daddr, ntohs(dport),
 338                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 339
 340         return (sk != NULL);
 341 }
 342 #endif
 343
 344 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
 345 {
 346         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 347
 348         if (info->flags & ~XT_SOCKET_FLAGS_V1) {
 349                 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
 350                 return -EINVAL;
 351         }
 352         return 0;
 353 }
 354
 355 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
 356 {
 357         const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
 358
 359         if (info->flags & ~XT_SOCKET_FLAGS_V2) {
 360                 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
 361                 return -EINVAL;
 362         }
 363         return 0;
 364 }
 365
 366 static struct xt_match socket_mt_reg[] __read_mostly = {
 367         {
 368                 .name           = "socket",
 369                 .revision       = 0,
 370                 .family         = NFPROTO_IPV4,
 371                 .match          = socket_mt4_v0,
 372                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 373                                   (1 << NF_INET_LOCAL_IN),
 374                 .me             = THIS_MODULE,
 375         },
 376         {
 377                 .name           = "socket",
 378                 .revision       = 1,
 379                 .family         = NFPROTO_IPV4,
 380                 .match          = socket_mt4_v1_v2,
 381                 .checkentry     = socket_mt_v1_check,
 382                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 383                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 384                                   (1 << NF_INET_LOCAL_IN),
 385                 .me             = THIS_MODULE,
 386         },
 387 #ifdef XT_SOCKET_HAVE_IPV6
 388         {
 389                 .name           = "socket",
 390                 .revision       = 1,
 391                 .family         = NFPROTO_IPV6,
 392                 .match          = socket_mt6_v1_v2,
 393                 .checkentry     = socket_mt_v1_check,
 394                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 395                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 396                                   (1 << NF_INET_LOCAL_IN),
 397                 .me             = THIS_MODULE,
 398         },
 399 #endif
 400         {
 401                 .name           = "socket",
 402                 .revision       = 2,
 403                 .family         = NFPROTO_IPV4,
 404                 .match          = socket_mt4_v1_v2,
 405                 .checkentry     = socket_mt_v2_check,
 406                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 407                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 408                                   (1 << NF_INET_LOCAL_IN),
 409                 .me             = THIS_MODULE,
 410         },
 411 #ifdef XT_SOCKET_HAVE_IPV6
 412         {
 413                 .name           = "socket",
 414                 .revision       = 2,
 415                 .family         = NFPROTO_IPV6,
 416                 .match          = socket_mt6_v1_v2,
 417                 .checkentry     = socket_mt_v2_check,
 418                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 419                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 420                                   (1 << NF_INET_LOCAL_IN),
 421                 .me             = THIS_MODULE,
 422         },
 423 #endif
 424 };
 425
 426 static int __init socket_mt_init(void)
 427 {
 428         nf_defrag_ipv4_enable();
 429 #ifdef XT_SOCKET_HAVE_IPV6
 430         nf_defrag_ipv6_enable();
 431 #endif
 432
 433         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 434 }
 435
 436 static void __exit socket_mt_exit(void)
 437 {
 438         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 439 }
 440
 441 module_init(socket_mt_init);
 442 module_exit(socket_mt_exit);
 443
 444 MODULE_LICENSE("GPL");
 445 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 446 MODULE_DESCRIPTION("x_tables socket match module");
 447 MODULE_ALIAS("ipt_socket");
 448 MODULE_ALIAS("ip6t_socket");