KOVACS Krisztian | 136cdc7 | 2008-10-08 11:35:12 +0200 | [diff] [blame] | 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 | |
| 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_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) |
| 26 | #define XT_SOCKET_HAVE_CONNTRACK 1 |
| 27 | #include <net/netfilter/nf_conntrack.h> |
| 28 | #endif |
| 29 | |
| 30 | static int |
| 31 | extract_icmp_fields(const struct sk_buff *skb, |
| 32 | u8 *protocol, |
| 33 | __be32 *raddr, |
| 34 | __be32 *laddr, |
| 35 | __be16 *rport, |
| 36 | __be16 *lport) |
| 37 | { |
| 38 | unsigned int outside_hdrlen = ip_hdrlen(skb); |
| 39 | struct iphdr *inside_iph, _inside_iph; |
| 40 | struct icmphdr *icmph, _icmph; |
| 41 | __be16 *ports, _ports[2]; |
| 42 | |
| 43 | icmph = skb_header_pointer(skb, outside_hdrlen, |
| 44 | sizeof(_icmph), &_icmph); |
| 45 | if (icmph == NULL) |
| 46 | return 1; |
| 47 | |
| 48 | switch (icmph->type) { |
| 49 | case ICMP_DEST_UNREACH: |
| 50 | case ICMP_SOURCE_QUENCH: |
| 51 | case ICMP_REDIRECT: |
| 52 | case ICMP_TIME_EXCEEDED: |
| 53 | case ICMP_PARAMETERPROB: |
| 54 | break; |
| 55 | default: |
| 56 | return 1; |
| 57 | } |
| 58 | |
| 59 | inside_iph = skb_header_pointer(skb, outside_hdrlen + |
| 60 | sizeof(struct icmphdr), |
| 61 | sizeof(_inside_iph), &_inside_iph); |
| 62 | if (inside_iph == NULL) |
| 63 | return 1; |
| 64 | |
| 65 | if (inside_iph->protocol != IPPROTO_TCP && |
| 66 | inside_iph->protocol != IPPROTO_UDP) |
| 67 | return 1; |
| 68 | |
| 69 | ports = skb_header_pointer(skb, outside_hdrlen + |
| 70 | sizeof(struct icmphdr) + |
| 71 | (inside_iph->ihl << 2), |
| 72 | sizeof(_ports), &_ports); |
| 73 | if (ports == NULL) |
| 74 | return 1; |
| 75 | |
| 76 | /* the inside IP packet is the one quoted from our side, thus |
| 77 | * its saddr is the local address */ |
| 78 | *protocol = inside_iph->protocol; |
| 79 | *laddr = inside_iph->saddr; |
| 80 | *lport = ports[0]; |
| 81 | *raddr = inside_iph->daddr; |
| 82 | *rport = ports[1]; |
| 83 | |
| 84 | return 0; |
| 85 | } |
| 86 | |
| 87 | |
| 88 | static bool |
Jan Engelhardt | f7108a2 | 2008-10-08 11:35:18 +0200 | [diff] [blame] | 89 | socket_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
KOVACS Krisztian | 136cdc7 | 2008-10-08 11:35:12 +0200 | [diff] [blame] | 90 | { |
| 91 | const struct iphdr *iph = ip_hdr(skb); |
| 92 | struct udphdr _hdr, *hp = NULL; |
| 93 | struct sock *sk; |
| 94 | __be32 daddr, saddr; |
| 95 | __be16 dport, sport; |
| 96 | u8 protocol; |
| 97 | #ifdef XT_SOCKET_HAVE_CONNTRACK |
| 98 | struct nf_conn const *ct; |
| 99 | enum ip_conntrack_info ctinfo; |
| 100 | #endif |
| 101 | |
| 102 | if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { |
| 103 | hp = skb_header_pointer(skb, ip_hdrlen(skb), |
| 104 | sizeof(_hdr), &_hdr); |
| 105 | if (hp == NULL) |
| 106 | return false; |
| 107 | |
| 108 | protocol = iph->protocol; |
| 109 | saddr = iph->saddr; |
| 110 | sport = hp->source; |
| 111 | daddr = iph->daddr; |
| 112 | dport = hp->dest; |
| 113 | |
| 114 | } else if (iph->protocol == IPPROTO_ICMP) { |
| 115 | if (extract_icmp_fields(skb, &protocol, &saddr, &daddr, |
| 116 | &sport, &dport)) |
| 117 | return false; |
| 118 | } else { |
| 119 | return false; |
| 120 | } |
| 121 | |
| 122 | #ifdef XT_SOCKET_HAVE_CONNTRACK |
| 123 | /* Do the lookup with the original socket address in case this is a |
| 124 | * reply packet of an established SNAT-ted connection. */ |
| 125 | |
| 126 | ct = nf_ct_get(skb, &ctinfo); |
| 127 | if (ct && (ct != &nf_conntrack_untracked) && |
| 128 | ((iph->protocol != IPPROTO_ICMP && |
| 129 | ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) || |
| 130 | (iph->protocol == IPPROTO_ICMP && |
| 131 | ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) && |
| 132 | (ct->status & IPS_SRC_NAT_DONE)) { |
| 133 | |
| 134 | daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; |
| 135 | dport = (iph->protocol == IPPROTO_TCP) ? |
| 136 | ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : |
| 137 | ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; |
| 138 | } |
| 139 | #endif |
| 140 | |
| 141 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol, |
Jan Engelhardt | f7108a2 | 2008-10-08 11:35:18 +0200 | [diff] [blame] | 142 | saddr, daddr, sport, dport, par->in, false); |
KOVACS Krisztian | 136cdc7 | 2008-10-08 11:35:12 +0200 | [diff] [blame] | 143 | if (sk != NULL) { |
Balazs Scheidler | c49b9f2 | 2008-12-07 23:53:46 -0800 | [diff] [blame] | 144 | bool wildcard = (sk->sk_state != TCP_TIME_WAIT && inet_sk(sk)->rcv_saddr == 0); |
KOVACS Krisztian | 136cdc7 | 2008-10-08 11:35:12 +0200 | [diff] [blame] | 145 | |
| 146 | nf_tproxy_put_sock(sk); |
| 147 | if (wildcard) |
| 148 | sk = NULL; |
| 149 | } |
| 150 | |
| 151 | pr_debug("socket match: proto %u %08x:%u -> %08x:%u " |
| 152 | "(orig %08x:%u) sock %p\n", |
| 153 | protocol, ntohl(saddr), ntohs(sport), |
| 154 | ntohl(daddr), ntohs(dport), |
| 155 | ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk); |
| 156 | |
| 157 | return (sk != NULL); |
| 158 | } |
| 159 | |
| 160 | static struct xt_match socket_mt_reg __read_mostly = { |
| 161 | .name = "socket", |
| 162 | .family = AF_INET, |
| 163 | .match = socket_mt, |
| 164 | .hooks = 1 << NF_INET_PRE_ROUTING, |
| 165 | .me = THIS_MODULE, |
| 166 | }; |
| 167 | |
| 168 | static int __init socket_mt_init(void) |
| 169 | { |
| 170 | nf_defrag_ipv4_enable(); |
| 171 | return xt_register_match(&socket_mt_reg); |
| 172 | } |
| 173 | |
| 174 | static void __exit socket_mt_exit(void) |
| 175 | { |
| 176 | xt_unregister_match(&socket_mt_reg); |
| 177 | } |
| 178 | |
| 179 | module_init(socket_mt_init); |
| 180 | module_exit(socket_mt_exit); |
| 181 | |
| 182 | MODULE_LICENSE("GPL"); |
| 183 | MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); |
| 184 | MODULE_DESCRIPTION("x_tables socket match module"); |
| 185 | MODULE_ALIAS("ipt_socket"); |