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 #include <linux/netfilter/xt_socket.h>
  26
  27 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  28 #define XT_SOCKET_HAVE_CONNTRACK 1
  29 #include <net/netfilter/nf_conntrack.h>
  30 #endif
  31
  32 static int
  33 extract_icmp_fields(const struct sk_buff *skb,
  34                     u8 *protocol,
  35                     __be32 *raddr,
  36                     __be32 *laddr,
  37                     __be16 *rport,
  38                     __be16 *lport)
  39 {
  40         unsigned int outside_hdrlen = ip_hdrlen(skb);
  41         struct iphdr *inside_iph, _inside_iph;
  42         struct icmphdr *icmph, _icmph;
  43         __be16 *ports, _ports[2];
  44
  45         icmph = skb_header_pointer(skb, outside_hdrlen,
  46                                    sizeof(_icmph), &_icmph);
  47         if (icmph == NULL)
  48                 return 1;
  49
  50         switch (icmph->type) {
  51         case ICMP_DEST_UNREACH:
  52         case ICMP_SOURCE_QUENCH:
  53         case ICMP_REDIRECT:
  54         case ICMP_TIME_EXCEEDED:
  55         case ICMP_PARAMETERPROB:
  56                 break;
  57         default:
  58                 return 1;
  59         }
  60
  61         inside_iph = skb_header_pointer(skb, outside_hdrlen +
  62                                         sizeof(struct icmphdr),
  63                                         sizeof(_inside_iph), &_inside_iph);
  64         if (inside_iph == NULL)
  65                 return 1;
  66
  67         if (inside_iph->protocol != IPPROTO_TCP &&
  68             inside_iph->protocol != IPPROTO_UDP)
  69                 return 1;
  70
  71         ports = skb_header_pointer(skb, outside_hdrlen +
  72                                    sizeof(struct icmphdr) +
  73                                    (inside_iph->ihl << 2),
  74                                    sizeof(_ports), &_ports);
  75         if (ports == NULL)
  76                 return 1;
  77
  78         /* the inside IP packet is the one quoted from our side, thus
  79          * its saddr is the local address */
  80         *protocol = inside_iph->protocol;
  81         *laddr = inside_iph->saddr;
  82         *lport = ports[0];
  83         *raddr = inside_iph->daddr;
  84         *rport = ports[1];
  85
  86         return 0;
  87 }
  88
  89
  90 static bool
  91 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
  92              const struct xt_socket_mtinfo1 *info)
  93 {
  94         const struct iphdr *iph = ip_hdr(skb);
  95         struct udphdr _hdr, *hp = NULL;
  96         struct sock *sk;
  97         __be32 daddr, saddr;
  98         __be16 dport, sport;
  99         u8 protocol;
 100 #ifdef XT_SOCKET_HAVE_CONNTRACK
 101         struct nf_conn const *ct;
 102         enum ip_conntrack_info ctinfo;
 103 #endif
 104
 105         if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
 106                 hp = skb_header_pointer(skb, ip_hdrlen(skb),
 107                                         sizeof(_hdr), &_hdr);
 108                 if (hp == NULL)
 109                         return false;
 110
 111                 protocol = iph->protocol;
 112                 saddr = iph->saddr;
 113                 sport = hp->source;
 114                 daddr = iph->daddr;
 115                 dport = hp->dest;
 116
 117         } else if (iph->protocol == IPPROTO_ICMP) {
 118                 if (extract_icmp_fields(skb, &protocol, &saddr, &daddr,
 119                                         &sport, &dport))
 120                         return false;
 121         } else {
 122                 return false;
 123         }
 124
 125 #ifdef XT_SOCKET_HAVE_CONNTRACK
 126         /* Do the lookup with the original socket address in case this is a
 127          * reply packet of an established SNAT-ted connection. */
 128
 129         ct = nf_ct_get(skb, &ctinfo);
 130         if (ct && !nf_ct_is_untracked(ct) &&
 131             ((iph->protocol != IPPROTO_ICMP &&
 132               ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
 133              (iph->protocol == IPPROTO_ICMP &&
 134               ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
 135             (ct->status & IPS_SRC_NAT_DONE)) {
 136
 137                 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
 138                 dport = (iph->protocol == IPPROTO_TCP) ?
 139                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
 140                         ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
 141         }
 142 #endif
 143
 144         sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
 145                                    saddr, daddr, sport, dport, par->in, false);
 146         if (sk != NULL) {
 147                 bool wildcard;
 148                 bool transparent = true;
 149
 150                 /* Ignore sockets listening on INADDR_ANY */
 151                 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
 152                             inet_sk(sk)->inet_rcv_saddr == 0);
 153
 154                 /* Ignore non-transparent sockets,
 155                    if XT_SOCKET_TRANSPARENT is used */
 156                 if (info && info->flags & XT_SOCKET_TRANSPARENT)
 157                         transparent = ((sk->sk_state != TCP_TIME_WAIT &&
 158                                         inet_sk(sk)->transparent) ||
 159                                        (sk->sk_state == TCP_TIME_WAIT &&
 160                                         inet_twsk(sk)->tw_transparent));
 161
 162                 nf_tproxy_put_sock(sk);
 163
 164                 if (wildcard || !transparent)
 165                         sk = NULL;
 166         }
 167
 168         pr_debug("proto %u %08x:%u -> %08x:%u (orig %08x:%u) sock %p\n",
 169                  protocol, ntohl(saddr), ntohs(sport),
 170                  ntohl(daddr), ntohs(dport),
 171                  ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk);
 172
 173         return (sk != NULL);
 174 }
 175
 176 static bool
 177 socket_mt_v0(const struct sk_buff *skb, struct xt_action_param *par)
 178 {
 179         return socket_match(skb, par, NULL);
 180 }
 181
 182 static bool
 183 socket_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 184 {
 185         return socket_match(skb, par, par->matchinfo);
 186 }
 187
 188 static struct xt_match socket_mt_reg[] __read_mostly = {
 189         {
 190                 .name           = "socket",
 191                 .revision       = 0,
 192                 .family         = NFPROTO_IPV4,
 193                 .match          = socket_mt_v0,
 194                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 195                                   (1 << NF_INET_LOCAL_IN),
 196                 .me             = THIS_MODULE,
 197         },
 198         {
 199                 .name           = "socket",
 200                 .revision       = 1,
 201                 .family         = NFPROTO_IPV4,
 202                 .match          = socket_mt_v1,
 203                 .matchsize      = sizeof(struct xt_socket_mtinfo1),
 204                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 205                                   (1 << NF_INET_LOCAL_IN),
 206                 .me             = THIS_MODULE,
 207         },
 208 };
 209
 210 static int __init socket_mt_init(void)
 211 {
 212         nf_defrag_ipv4_enable();
 213         return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 214 }
 215
 216 static void __exit socket_mt_exit(void)
 217 {
 218         xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
 219 }
 220
 221 module_init(socket_mt_init);
 222 module_exit(socket_mt_exit);
 223
 224 MODULE_LICENSE("GPL");
 225 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
 226 MODULE_DESCRIPTION("x_tables socket match module");
 227 MODULE_ALIAS("ipt_socket");