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