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 <linux/netfilter_ipv6/ip6_tables.h>
  18 #include <net/tcp.h>
  19 #include <net/udp.h>
  20 #include <net/icmp.h>
  21 #include <net/sock.h>
  22 #include <net/inet_sock.h>
  23 #include <net/netfilter/nf_tproxy_core.h>
  24 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  25 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  26
  27 #include <linux/netfilter/xt_socket.h>
  28
  29 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  30 #define XT_SOCKET_HAVE_CONNTRACK 1
  31 #include <net/netfilter/nf_conntrack.h>
  32 #endif
  33
  34 static int
  35 extract_icmp4_fields(const struct sk_buff *skb,
  36                     u8 *protocol,
  37                     __be32 *raddr,
  38                     __be32 *laddr,
  39                     __be16 *rport,
  40                     __be16 *lport)
  41 {
  42         unsigned int outside_hdrlen = ip_hdrlen(skb);
  43         struct iphdr *inside_iph, _inside_iph;
  44         struct icmphdr *icmph, _icmph;
  45         __be16 *ports, _ports[2];
  46
  47         icmph = skb_header_pointer(skb, outside_hdrlen,
  48                                    sizeof(_icmph), &_icmph);
  49         if (icmph == NULL)
  50                 return 1;
  51
  52         switch (icmph->type) {
  53         case ICMP_DEST_UNREACH:
  54         case ICMP_SOURCE_QUENCH:
  55         case ICMP_REDIRECT:
  56         case ICMP_TIME_EXCEEDED:
  57         case ICMP_PARAMETERPROB:
  58                 break;
  59         default:
  60                 return 1;
  61         }
  62
  63         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  64                                         sizeof(struct icmphdr),
  65                                         sizeof(_inside_iph), &_inside_iph);
  66         if (inside_iph == NULL)
  67                 return 1;
  68
  69         if (inside_iph->protocol != IPPROTO_TCP &&
  70             inside_iph->protocol != IPPROTO_UDP)
  71                 return 1;
  72
  73         ports = skb_header_pointer(skb, outside_hdrlen +
  74                                    sizeof(struct icmphdr) +
  75                                    (inside_iph->ihl << 2),
  76                                    sizeof(_ports), &_ports);
  77         if (ports == NULL)
  78                 return 1;
  79
  80         /* the inside IP packet is the one quoted from our side, thus
  81          * its saddr is the local address */
  82         *protocol = inside_iph->protocol;
  83         *laddr = inside_iph->saddr;
  84         *lport = ports[0];
  85         *raddr = inside_iph->daddr;
  86         *rport = ports[1];
  87
  88         return 0;
  89 }
  90
  91 static bool
  92 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
  93              const struct xt_socket_mtinfo1 *info)
  94 {
  95         const struct iphdr *iph = ip_hdr(skb);
  96         struct udphdr _hdr, *hp = NULL;
  97         struct sock *sk;
  98         __be32 daddr, saddr;
  99         __be16 dport, sport;
 100         u8 protocol;
 101 #ifdef XT_SOCKET_HAVE_CONNTRACK
 102         struct nf_conn const *ct;
 103         enum ip_conntrack_info ctinfo;
 104 #endif
 105
 106         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 107                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 108                                         sizeof(_hdr), &_hdr);
 109                 if (hp == NULL)
 110                         return false;
 111
 112                 protocol = iph->protocol;
 113                 saddr = iph->saddr;
 114                 sport = hp->source;
 115                 daddr = iph->daddr;
 116                 dport = hp->dest;
 117
 118         } else if (iph->protocol == IPPROTO_ICMP) {
 119                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 120                                         &sport, &dport))
 121                         return false;
 122         } else {
 123                 return false;
 124         }
 125
 126 #ifdef XT_SOCKET_HAVE_CONNTRACK
 127         /* Do the lookup with the original socket address in case this is a
 128          * reply packet of an established SNAT-ted connection. */
 129
 130         ct = nf_ct_get(skb, &ctinfo);
 131         if (ct && !nf_ct_is_untracked(ct) &&
 132             ((iph->protocol != IPPROTO_ICMP &&
 133               ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
 134              (iph->protocol == IPPROTO_ICMP &&
 135               ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
 136             (ct->status & IPS_SRC_NAT_DONE)) {
 137
 138                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 139                 dport = (iph->protocol == IPPROTO_TCP) ?
 140                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 141                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 142         }
 143 #endif
 144
 145         sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 146                                    saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 147         if (sk != NULL) {
 148                 bool wildcard;
 149                 bool transparent = true;
 150
 151                 /* Ignore sockets listening on INADDR_ANY */
 152                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 153                             inet_sk(sk)->inet_rcv_saddr == 0);
 154
 155                 /* Ignore non-transparent sockets,
 156                    if XT_SOCKET_TRANSPARENT is used */
 157                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 158                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 159                                         inet_sk(sk)->transparent) ||
 160                                        (sk->sk_state == TCP_TIME_WAIT &&
 161                                         inet_twsk(sk)->tw_transparent));
 162
 163                 nf_tproxy_put_sock(sk);
 164
 165                 if (wildcard || !transparent)
 166                         sk = NULL;
 167         }
 168
 169         pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 170                  protocol, &saddr, ntohs(sport),
 171                  &daddr, ntohs(dport),
 172                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 173
 174         return (sk != NULL);
 175 }
 176
 177 static bool
 178 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 179 {
 180         return socket_match(skb, par, NULL);
 181 }
 182
 183 static bool
 184 socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
 185 {
 186         return socket_match(skb, par, par->matchinfo);
 187 }
 188
 189 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 190
 191 static int
 192 extract_icmp6_fields(const struct sk_buff *skb,
 193                      unsigned int outside_hdrlen,
 194                      u8 *protocol,
 195                      struct in6_addr **raddr,
 196                      struct in6_addr **laddr,
 197                      __be16 *rport,
 198                      __be16 *lport)
 199 {
 200         struct ipv6hdr *inside_iph, _inside_iph;
 201         struct icmp6hdr *icmph, _icmph;
 202         __be16 *ports, _ports[2];
 203         u8 inside_nexthdr;
 204         int inside_hdrlen;
 205
 206         icmph = skb_header_pointer(skb, outside_hdrlen,
 207                                    sizeof(_icmph), &_icmph);
 208         if (icmph == NULL)
 209                 return 1;
 210
 211         if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 212                 return 1;
 213
 214         inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 215         if (inside_iph == NULL)
 216                 return 1;
 217         inside_nexthdr = inside_iph->nexthdr;
 218
 219         inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph), &inside_nexthdr);
 220         if (inside_hdrlen < 0)
 221                 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 222
 223         if (inside_nexthdr != IPPROTO_TCP &&
 224             inside_nexthdr != IPPROTO_UDP)
 225                 return 1;
 226
 227         ports = skb_header_pointer(skb, inside_hdrlen,
 228                                    sizeof(_ports), &_ports);
 229         if (ports == NULL)
 230                 return 1;
 231
 232         /* the inside IP packet is the one quoted from our side, thus
 233          * its saddr is the local address */
 234         *protocol = inside_nexthdr;
 235         *laddr = &inside_iph->saddr;
 236         *lport = ports[0];
 237         *raddr = &inside_iph->daddr;
 238         *rport = ports[1];
 239
 240         return 0;
 241 }
 242
 243 static bool
 244 socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
 245 {
 246         struct ipv6hdr *iph = ipv6_hdr(skb);
 247         struct udphdr _hdr, *hp = NULL;
 248         struct sock *sk;
 249         struct in6_addr *daddr, *saddr;
 250         __be16 dport, sport;
 251         int thoff;
 252         u8 tproto;
 253         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 254
 255         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL);
 256         if (tproto < 0) {
 257                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 258                 return NF_DROP;
 259         }
 260
 261         if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 262                 hp = skb_header_pointer(skb, thoff,
 263                                         sizeof(_hdr), &_hdr);
 264                 if (hp == NULL)
 265                         return false;
 266
 267                 saddr = &iph->saddr;
 268                 sport = hp->source;
 269                 daddr = &iph->daddr;
 270                 dport = hp->dest;
 271
 272         } else if (tproto == IPPROTO_ICMPV6) {
 273                 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 274                                          &sport, &dport))
 275                         return false;
 276         } else {
 277                 return false;
 278         }
 279
 280         sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 281                                    saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 282         if (sk != NULL) {
 283                 bool wildcard;
 284                 bool transparent = true;
 285
 286                 /* Ignore sockets listening on INADDR_ANY */
 287                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 288                             ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 289
 290                 /* Ignore non-transparent sockets,
 291                    if XT_SOCKET_TRANSPARENT is used */
 292                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 293                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 294                                         inet_sk(sk)->transparent) ||
 295                                        (sk->sk_state == TCP_TIME_WAIT &&
 296                                         inet_twsk(sk)->tw_transparent));
 297
 298                 nf_tproxy_put_sock(sk);
 299
 300                 if (wildcard || !transparent)
 301                         sk = NULL;
 302         }
 303
 304         pr_debug("proto %hhu %pI6:%hu -> %pI6:%hu "
 305                  "(orig %pI6:%hu) sock %p\n",
 306                  tproto, saddr, ntohs(sport),
 307                  daddr, ntohs(dport),
 308                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 309
 310         return (sk != NULL);
 311 }
 312 #endif
 313
 314 static struct xt_match socket_mt_reg[] __read_mostly = {
 315         {
 316                 .name           = "socket",
 317                 .revision       = 0,
 318                 .family         = NFPROTO_IPV4,
 319                 .match          = socket_mt4_v0,
 320                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 321                                   (1 << NF_INET_LOCAL_IN),
 322                 .me             = THIS_MODULE,
 323         },
 324         {
 325                 .name           = "socket",
 326                 .revision       = 1,
 327                 .family         = NFPROTO_IPV4,
 328                 .match          = socket_mt4_v1,
 329                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 330                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 331                                   (1 << NF_INET_LOCAL_IN),
 332                 .me             = THIS_MODULE,
 333         },
 334 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 335         {
 336                 .name           = "socket",
 337                 .revision       = 1,
 338                 .family         = NFPROTO_IPV6,
 339                 .match          = socket_mt6_v1,
 340                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 341                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 342                                   (1 << NF_INET_LOCAL_IN),
 343                 .me             = THIS_MODULE,
 344         },
 345 #endif
 346 };
 347
 348 static int __init socket_mt_init(void)
 349 {
 350         nf_defrag_ipv4_enable();
 351 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 352         nf_defrag_ipv6_enable();
 353 #endif
 354
 355         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 356 }
 357
 358 static void __exit socket_mt_exit(void)
 359 {
 360         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 361 }
 362
 363 module_init(socket_mt_init);
 364 module_exit(socket_mt_exit);
 365
 366 MODULE_LICENSE("GPL");
 367 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 368 MODULE_DESCRIPTION("x_tables socket match module");
 369 MODULE_ALIAS("ipt_socket");
 370 MODULE_ALIAS("ip6t_socket");