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 defined(CONFIG_IP6_NF_IPTABLES) || defined(CONFIG_IP6_NF_IPTABLES_MODULE)
  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 defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  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 static bool
  96 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
  97              const struct xt_socket_mtinfo1 *info)
  98 {
  99         const struct iphdr *iph = ip_hdr(skb);
 100         struct udphdr _hdr, *hp = NULL;
 101         struct sock *sk;
 102         __be32 daddr, saddr;
 103         __be16 dport, sport;
 104         u8 protocol;
 105 #ifdef XT_SOCKET_HAVE_CONNTRACK
 106         struct nf_conn const *ct;
 107         enum ip_conntrack_info ctinfo;
 108 #endif
 109
 110         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 111                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 112                                         sizeof(_hdr), &_hdr);
 113                 if (hp == NULL)
 114                         return false;
 115
 116                 protocol = iph->protocol;
 117                 saddr = iph->saddr;
 118                 sport = hp->source;
 119                 daddr = iph->daddr;
 120                 dport = hp->dest;
 121
 122         } else if (iph->protocol == IPPROTO_ICMP) {
 123                 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
 124                                         &sport, &dport))
 125                         return false;
 126         } else {
 127                 return false;
 128         }
 129
 130 #ifdef XT_SOCKET_HAVE_CONNTRACK
 131         /* Do the lookup with the original socket address in case this is a
 132          * reply packet of an established SNAT-ted connection. */
 133
 134         ct = nf_ct_get(skb, &ctinfo);
 135         if (ct && !nf_ct_is_untracked(ct) &&
 136             ((iph->protocol != IPPROTO_ICMP &&
 137               ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
 138              (iph->protocol == IPPROTO_ICMP &&
 139               ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
 140             (ct->status & IPS_SRC_NAT_DONE)) {
 141
 142                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 143                 dport = (iph->protocol == IPPROTO_TCP) ?
 144                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 145                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 146         }
 147 #endif
 148
 149         sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 150                                    saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 151         if (sk != NULL) {
 152                 bool wildcard;
 153                 bool transparent = true;
 154
 155                 /* Ignore sockets listening on INADDR_ANY */
 156                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 157                             inet_sk(sk)->inet_rcv_saddr == 0);
 158
 159                 /* Ignore non-transparent sockets,
 160                    if XT_SOCKET_TRANSPARENT is used */
 161                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 162                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 163                                         inet_sk(sk)->transparent) ||
 164                                        (sk->sk_state == TCP_TIME_WAIT &&
 165                                         inet_twsk(sk)->tw_transparent));
 166
 167                 nf_tproxy_put_sock(sk);
 168
 169                 if (wildcard || !transparent)
 170                         sk = NULL;
 171         }
 172
 173         pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
 174                  protocol, &saddr, ntohs(sport),
 175                  &daddr, ntohs(dport),
 176                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 177
 178         return (sk != NULL);
 179 }
 180
 181 static bool
 182 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
 183 {
 184         return socket_match(skb, par, NULL);
 185 }
 186
 187 static bool
 188 socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
 189 {
 190         return socket_match(skb, par, par->matchinfo);
 191 }
 192
 193 #ifdef XT_SOCKET_HAVE_IPV6
 194
 195 static int
 196 extract_icmp6_fields(const struct sk_buff *skb,
 197                      unsigned int outside_hdrlen,
 198                      int *protocol,
 199                      struct in6_addr **raddr,
 200                      struct in6_addr **laddr,
 201                      __be16 *rport,
 202                      __be16 *lport)
 203 {
 204         struct ipv6hdr *inside_iph, _inside_iph;
 205         struct icmp6hdr *icmph, _icmph;
 206         __be16 *ports, _ports[2];
 207         u8 inside_nexthdr;
 208         int inside_hdrlen;
 209
 210         icmph = skb_header_pointer(skb, outside_hdrlen,
 211                                    sizeof(_icmph), &_icmph);
 212         if (icmph == NULL)
 213                 return 1;
 214
 215         if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
 216                 return 1;
 217
 218         inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
 219         if (inside_iph == NULL)
 220                 return 1;
 221         inside_nexthdr = inside_iph->nexthdr;
 222
 223         inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph), &inside_nexthdr);
 224         if (inside_hdrlen < 0)
 225                 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
 226
 227         if (inside_nexthdr != IPPROTO_TCP &&
 228             inside_nexthdr != IPPROTO_UDP)
 229                 return 1;
 230
 231         ports = skb_header_pointer(skb, inside_hdrlen,
 232                                    sizeof(_ports), &_ports);
 233         if (ports == NULL)
 234                 return 1;
 235
 236         /* the inside IP packet is the one quoted from our side, thus
 237          * its saddr is the local address */
 238         *protocol = inside_nexthdr;
 239         *laddr = &inside_iph->saddr;
 240         *lport = ports[0];
 241         *raddr = &inside_iph->daddr;
 242         *rport = ports[1];
 243
 244         return 0;
 245 }
 246
 247 static bool
 248 socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
 249 {
 250         struct ipv6hdr *iph = ipv6_hdr(skb);
 251         struct udphdr _hdr, *hp = NULL;
 252         struct sock *sk;
 253         struct in6_addr *daddr, *saddr;
 254         __be16 dport, sport;
 255         int thoff, tproto;
 256         const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
 257
 258         tproto = ipv6_find_hdr(skb, &thoff, -1, NULL);
 259         if (tproto < 0) {
 260                 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
 261                 return NF_DROP;
 262         }
 263
 264         if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
 265                 hp = skb_header_pointer(skb, thoff,
 266                                         sizeof(_hdr), &_hdr);
 267                 if (hp == NULL)
 268                         return false;
 269
 270                 saddr = &iph->saddr;
 271                 sport = hp->source;
 272                 daddr = &iph->daddr;
 273                 dport = hp->dest;
 274
 275         } else if (tproto == IPPROTO_ICMPV6) {
 276                 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
 277                                          &sport, &dport))
 278                         return false;
 279         } else {
 280                 return false;
 281         }
 282
 283         sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
 284                                    saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
 285         if (sk != NULL) {
 286                 bool wildcard;
 287                 bool transparent = true;
 288
 289                 /* Ignore sockets listening on INADDR_ANY */
 290                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 291                             ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
 292
 293                 /* Ignore non-transparent sockets,
 294                    if XT_SOCKET_TRANSPARENT is used */
 295                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 296                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 297                                         inet_sk(sk)->transparent) ||
 298                                        (sk->sk_state == TCP_TIME_WAIT &&
 299                                         inet_twsk(sk)->tw_transparent));
 300
 301                 nf_tproxy_put_sock(sk);
 302
 303                 if (wildcard || !transparent)
 304                         sk = NULL;
 305         }
 306
 307         pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
 308                  "(orig %pI6:%hu) sock %p\n",
 309                  tproto, saddr, ntohs(sport),
 310                  daddr, ntohs(dport),
 311                  &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
 312
 313         return (sk != NULL);
 314 }
 315 #endif
 316
 317 static struct xt_match socket_mt_reg[] __read_mostly = {
 318         {
 319                 .name           = "socket",
 320                 .revision       = 0,
 321                 .family         = NFPROTO_IPV4,
 322                 .match          = socket_mt4_v0,
 323                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 324                                   (1 << NF_INET_LOCAL_IN),
 325                 .me             = THIS_MODULE,
 326         },
 327         {
 328                 .name           = "socket",
 329                 .revision       = 1,
 330                 .family         = NFPROTO_IPV4,
 331                 .match          = socket_mt4_v1,
 332                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 333                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 334                                   (1 << NF_INET_LOCAL_IN),
 335                 .me             = THIS_MODULE,
 336         },
 337 #ifdef XT_SOCKET_HAVE_IPV6
 338         {
 339                 .name           = "socket",
 340                 .revision       = 1,
 341                 .family         = NFPROTO_IPV6,
 342                 .match          = socket_mt6_v1,
 343                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 344                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 345                                   (1 << NF_INET_LOCAL_IN),
 346                 .me             = THIS_MODULE,
 347         },
 348 #endif
 349 };
 350
 351 static int __init socket_mt_init(void)
 352 {
 353         nf_defrag_ipv4_enable();
 354 #ifdef XT_SOCKET_HAVE_IPV6
 355         nf_defrag_ipv6_enable();
 356 #endif
 357
 358         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 359 }
 360
 361 static void __exit socket_mt_exit(void)
 362 {
 363         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 364 }
 365
 366 module_init(socket_mt_init);
 367 module_exit(socket_mt_exit);
 368
 369 MODULE_LICENSE("GPL");
 370 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 371 MODULE_DESCRIPTION("x_tables socket match module");
 372 MODULE_ALIAS("ipt_socket");
 373 MODULE_ALIAS("ip6t_socket");