2 * Transparent proxy support for Linux/iptables
4 * Copyright (C) 2007-2008 BalaBit IT Ltd.
5 * Author: Krisztian Kovacs
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.
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>
21 #include <net/inet_sock.h>
22 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
24 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
25 #define XT_SOCKET_HAVE_IPV6 1
26 #include <linux/netfilter_ipv6/ip6_tables.h>
27 #include <net/inet6_hashtables.h>
28 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
31 #include <linux/netfilter/xt_socket.h>
33 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
34 #define XT_SOCKET_HAVE_CONNTRACK 1
35 #include <net/netfilter/nf_conntrack.h>
39 extract_icmp4_fields(const struct sk_buff *skb,
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];
51 icmph = skb_header_pointer(skb, outside_hdrlen,
52 sizeof(_icmph), &_icmph);
56 switch (icmph->type) {
57 case ICMP_DEST_UNREACH:
58 case ICMP_SOURCE_QUENCH:
60 case ICMP_TIME_EXCEEDED:
61 case ICMP_PARAMETERPROB:
67 inside_iph = skb_header_pointer(skb, outside_hdrlen +
68 sizeof(struct icmphdr),
69 sizeof(_inside_iph), &_inside_iph);
70 if (inside_iph == NULL)
73 if (inside_iph->protocol != IPPROTO_TCP &&
74 inside_iph->protocol != IPPROTO_UDP)
77 ports = skb_header_pointer(skb, outside_hdrlen +
78 sizeof(struct icmphdr) +
79 (inside_iph->ihl << 2),
80 sizeof(_ports), &_ports);
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;
89 *raddr = inside_iph->daddr;
95 /* "socket" match based redirection (no specific rule)
96 * ===================================================
98 * There are connections with dynamic endpoints (e.g. FTP data
99 * connection) that the user is unable to add explicit rules
100 * for. These are taken care of by a generic "socket" rule. It is
101 * assumed that the proxy application is trusted to open such
102 * connections without explicit iptables rule (except of course the
103 * generic 'socket' rule). In this case the following sockets are
104 * matched in preference order:
106 * - match: if there's a fully established connection matching the
109 * - match: if there's a non-zero bound listener (possibly with a
110 * non-local address) We don't accept zero-bound listeners, since
111 * then local services could intercept traffic going through the
115 xt_socket_get_sock_v4(struct net *net, const u8 protocol,
116 const __be32 saddr, const __be32 daddr,
117 const __be16 sport, const __be16 dport,
118 const struct net_device *in)
122 return __inet_lookup(net, &tcp_hashinfo,
123 saddr, sport, daddr, dport,
126 return udp4_lib_lookup(net, saddr, sport, daddr, dport,
133 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
134 const struct xt_socket_mtinfo1 *info)
136 const struct iphdr *iph = ip_hdr(skb);
137 struct udphdr _hdr, *hp = NULL;
138 struct sock *sk = skb->sk;
139 __be32 uninitialized_var(daddr), uninitialized_var(saddr);
140 __be16 uninitialized_var(dport), uninitialized_var(sport);
141 u8 uninitialized_var(protocol);
142 #ifdef XT_SOCKET_HAVE_CONNTRACK
143 struct nf_conn const *ct;
144 enum ip_conntrack_info ctinfo;
147 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
148 hp = skb_header_pointer(skb, ip_hdrlen(skb),
149 sizeof(_hdr), &_hdr);
153 protocol = iph->protocol;
159 } else if (iph->protocol == IPPROTO_ICMP) {
160 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
167 #ifdef XT_SOCKET_HAVE_CONNTRACK
168 /* Do the lookup with the original socket address in case this is a
169 * reply packet of an established SNAT-ted connection. */
171 ct = nf_ct_get(skb, &ctinfo);
172 if (ct && !nf_ct_is_untracked(ct) &&
173 ((iph->protocol != IPPROTO_ICMP &&
174 ctinfo == IP_CT_ESTABLISHED_REPLY) ||
175 (iph->protocol == IPPROTO_ICMP &&
176 ctinfo == IP_CT_RELATED_REPLY)) &&
177 (ct->status & IPS_SRC_NAT_DONE)) {
179 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
180 dport = (iph->protocol == IPPROTO_TCP) ?
181 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
182 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
187 sk = xt_socket_get_sock_v4(dev_net(skb->dev), protocol,
188 saddr, daddr, sport, dport,
192 bool transparent = true;
194 /* Ignore sockets listening on INADDR_ANY,
195 * unless XT_SOCKET_NOWILDCARD is set
197 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
198 sk->sk_state != TCP_TIME_WAIT &&
199 inet_sk(sk)->inet_rcv_saddr == 0);
201 /* Ignore non-transparent sockets,
202 if XT_SOCKET_TRANSPARENT is used */
203 if (info->flags & XT_SOCKET_TRANSPARENT)
204 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
205 inet_sk(sk)->transparent) ||
206 (sk->sk_state == TCP_TIME_WAIT &&
207 inet_twsk(sk)->tw_transparent));
212 if (wildcard || !transparent)
216 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
217 protocol, &saddr, ntohs(sport),
218 &daddr, ntohs(dport),
219 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
225 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
227 static struct xt_socket_mtinfo1 xt_info_v0 = {
231 return socket_match(skb, par, &xt_info_v0);
235 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
237 return socket_match(skb, par, par->matchinfo);
240 #ifdef XT_SOCKET_HAVE_IPV6
243 extract_icmp6_fields(const struct sk_buff *skb,
244 unsigned int outside_hdrlen,
246 struct in6_addr **raddr,
247 struct in6_addr **laddr,
251 struct ipv6hdr *inside_iph, _inside_iph;
252 struct icmp6hdr *icmph, _icmph;
253 __be16 *ports, _ports[2];
255 __be16 inside_fragoff;
258 icmph = skb_header_pointer(skb, outside_hdrlen,
259 sizeof(_icmph), &_icmph);
263 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
266 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
267 if (inside_iph == NULL)
269 inside_nexthdr = inside_iph->nexthdr;
271 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
272 &inside_nexthdr, &inside_fragoff);
273 if (inside_hdrlen < 0)
274 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
276 if (inside_nexthdr != IPPROTO_TCP &&
277 inside_nexthdr != IPPROTO_UDP)
280 ports = skb_header_pointer(skb, inside_hdrlen,
281 sizeof(_ports), &_ports);
285 /* the inside IP packet is the one quoted from our side, thus
286 * its saddr is the local address */
287 *protocol = inside_nexthdr;
288 *laddr = &inside_iph->saddr;
290 *raddr = &inside_iph->daddr;
297 xt_socket_get_sock_v6(struct net *net, const u8 protocol,
298 const struct in6_addr *saddr, const struct in6_addr *daddr,
299 const __be16 sport, const __be16 dport,
300 const struct net_device *in)
304 return inet6_lookup(net, &tcp_hashinfo,
305 saddr, sport, daddr, dport,
308 return udp6_lib_lookup(net, saddr, sport, daddr, dport,
316 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
318 struct ipv6hdr *iph = ipv6_hdr(skb);
319 struct udphdr _hdr, *hp = NULL;
320 struct sock *sk = skb->sk;
321 struct in6_addr *daddr = NULL, *saddr = NULL;
322 __be16 uninitialized_var(dport), uninitialized_var(sport);
323 int thoff = 0, uninitialized_var(tproto);
324 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
326 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
328 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
332 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
333 hp = skb_header_pointer(skb, thoff,
334 sizeof(_hdr), &_hdr);
343 } else if (tproto == IPPROTO_ICMPV6) {
344 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
352 sk = xt_socket_get_sock_v6(dev_net(skb->dev), tproto,
353 saddr, daddr, sport, dport,
357 bool transparent = true;
359 /* Ignore sockets listening on INADDR_ANY
360 * unless XT_SOCKET_NOWILDCARD is set
362 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
363 sk->sk_state != TCP_TIME_WAIT &&
364 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
366 /* Ignore non-transparent sockets,
367 if XT_SOCKET_TRANSPARENT is used */
368 if (info->flags & XT_SOCKET_TRANSPARENT)
369 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
370 inet_sk(sk)->transparent) ||
371 (sk->sk_state == TCP_TIME_WAIT &&
372 inet_twsk(sk)->tw_transparent));
377 if (wildcard || !transparent)
381 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
382 "(orig %pI6:%hu) sock %p\n",
383 tproto, saddr, ntohs(sport),
385 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
391 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
393 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
395 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
396 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
402 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
404 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
406 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
407 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
413 static struct xt_match socket_mt_reg[] __read_mostly = {
417 .family = NFPROTO_IPV4,
418 .match = socket_mt4_v0,
419 .hooks = (1 << NF_INET_PRE_ROUTING) |
420 (1 << NF_INET_LOCAL_IN),
426 .family = NFPROTO_IPV4,
427 .match = socket_mt4_v1_v2,
428 .checkentry = socket_mt_v1_check,
429 .matchsize = sizeof(struct xt_socket_mtinfo1),
430 .hooks = (1 << NF_INET_PRE_ROUTING) |
431 (1 << NF_INET_LOCAL_IN),
434 #ifdef XT_SOCKET_HAVE_IPV6
438 .family = NFPROTO_IPV6,
439 .match = socket_mt6_v1_v2,
440 .checkentry = socket_mt_v1_check,
441 .matchsize = sizeof(struct xt_socket_mtinfo1),
442 .hooks = (1 << NF_INET_PRE_ROUTING) |
443 (1 << NF_INET_LOCAL_IN),
450 .family = NFPROTO_IPV4,
451 .match = socket_mt4_v1_v2,
452 .checkentry = socket_mt_v2_check,
453 .matchsize = sizeof(struct xt_socket_mtinfo1),
454 .hooks = (1 << NF_INET_PRE_ROUTING) |
455 (1 << NF_INET_LOCAL_IN),
458 #ifdef XT_SOCKET_HAVE_IPV6
462 .family = NFPROTO_IPV6,
463 .match = socket_mt6_v1_v2,
464 .checkentry = socket_mt_v2_check,
465 .matchsize = sizeof(struct xt_socket_mtinfo1),
466 .hooks = (1 << NF_INET_PRE_ROUTING) |
467 (1 << NF_INET_LOCAL_IN),
473 static int __init socket_mt_init(void)
475 nf_defrag_ipv4_enable();
476 #ifdef XT_SOCKET_HAVE_IPV6
477 nf_defrag_ipv6_enable();
480 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
483 static void __exit socket_mt_exit(void)
485 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
488 module_init(socket_mt_init);
489 module_exit(socket_mt_exit);
491 MODULE_LICENSE("GPL");
492 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
493 MODULE_DESCRIPTION("x_tables socket match module");
494 MODULE_ALIAS("ipt_socket");
495 MODULE_ALIAS("ip6t_socket");