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/*
* Transparent proxy support for Linux/iptables
*
* Copyright (C) 2007-2008 BalaBit IT Ltd.
* Author: Krisztian Kovacs
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/sock.h>
#include <net/inet_sock.h>
#include <net/netfilter/nf_tproxy_core.h>
#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
#define XT_SOCKET_HAVE_CONNTRACK 1
#include <net/netfilter/nf_conntrack.h>
#endif
static int
extract_icmp_fields(const struct sk_buff *skb,
u8 *protocol,
__be32 *raddr,
__be32 *laddr,
__be16 *rport,
__be16 *lport)
{
unsigned int outside_hdrlen = ip_hdrlen(skb);
struct iphdr *inside_iph, _inside_iph;
struct icmphdr *icmph, _icmph;
__be16 *ports, _ports[2];
icmph = skb_header_pointer(skb, outside_hdrlen,
sizeof(_icmph), &_icmph);
if (icmph == NULL)
return 1;
switch (icmph->type) {
case ICMP_DEST_UNREACH:
case ICMP_SOURCE_QUENCH:
case ICMP_REDIRECT:
case ICMP_TIME_EXCEEDED:
case ICMP_PARAMETERPROB:
break;
default:
return 1;
}
inside_iph = skb_header_pointer(skb, outside_hdrlen +
sizeof(struct icmphdr),
sizeof(_inside_iph), &_inside_iph);
if (inside_iph == NULL)
return 1;
if (inside_iph->protocol != IPPROTO_TCP &&
inside_iph->protocol != IPPROTO_UDP)
return 1;
ports = skb_header_pointer(skb, outside_hdrlen +
sizeof(struct icmphdr) +
(inside_iph->ihl << 2),
sizeof(_ports), &_ports);
if (ports == NULL)
return 1;
/* the inside IP packet is the one quoted from our side, thus
* its saddr is the local address */
*protocol = inside_iph->protocol;
*laddr = inside_iph->saddr;
*lport = ports[0];
*raddr = inside_iph->daddr;
*rport = ports[1];
return 0;
}
static bool
socket_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
const struct iphdr *iph = ip_hdr(skb);
struct udphdr _hdr, *hp = NULL;
struct sock *sk;
__be32 daddr, saddr;
__be16 dport, sport;
u8 protocol;
#ifdef XT_SOCKET_HAVE_CONNTRACK
struct nf_conn const *ct;
enum ip_conntrack_info ctinfo;
#endif
if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
hp = skb_header_pointer(skb, ip_hdrlen(skb),
sizeof(_hdr), &_hdr);
if (hp == NULL)
return false;
protocol = iph->protocol;
saddr = iph->saddr;
sport = hp->source;
daddr = iph->daddr;
dport = hp->dest;
} else if (iph->protocol == IPPROTO_ICMP) {
if (extract_icmp_fields(skb, &protocol, &saddr, &daddr,
&sport, &dport))
return false;
} else {
return false;
}
#ifdef XT_SOCKET_HAVE_CONNTRACK
/* Do the lookup with the original socket address in case this is a
* reply packet of an established SNAT-ted connection. */
ct = nf_ct_get(skb, &ctinfo);
if (ct && (ct != &nf_conntrack_untracked) &&
((iph->protocol != IPPROTO_ICMP &&
ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
(iph->protocol == IPPROTO_ICMP &&
ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
(ct->status & IPS_SRC_NAT_DONE)) {
daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
dport = (iph->protocol == IPPROTO_TCP) ?
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
}
#endif
sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
saddr, daddr, sport, dport, par->in, false);
if (sk != NULL) {
bool wildcard = (inet_sk(sk)->rcv_saddr == 0);
nf_tproxy_put_sock(sk);
if (wildcard)
sk = NULL;
}
pr_debug("socket match: proto %u %08x:%u -> %08x:%u "
"(orig %08x:%u) sock %p\n",
protocol, ntohl(saddr), ntohs(sport),
ntohl(daddr), ntohs(dport),
ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk);
return (sk != NULL);
}
static struct xt_match socket_mt_reg __read_mostly = {
.name = "socket",
.family = AF_INET,
.match = socket_mt,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
};
static int __init socket_mt_init(void)
{
nf_defrag_ipv4_enable();
return xt_register_match(&socket_mt_reg);
}
static void __exit socket_mt_exit(void)
{
xt_unregister_match(&socket_mt_reg);
}
module_init(socket_mt_init);
module_exit(socket_mt_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
MODULE_DESCRIPTION("x_tables socket match module");
MODULE_ALIAS("ipt_socket");
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