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,
132 static bool xt_socket_sk_is_transparent(struct sock *sk)
134 switch (sk->sk_state) {
136 return inet_twsk(sk)->tw_transparent;
138 case TCP_NEW_SYN_RECV:
139 return inet_rsk(inet_reqsk(sk))->no_srccheck;
142 return inet_sk(sk)->transparent;
146 static struct sock *xt_socket_lookup_slow_v4(const struct sk_buff *skb,
147 const struct net_device *indev)
149 const struct iphdr *iph = ip_hdr(skb);
150 __be32 uninitialized_var(daddr), uninitialized_var(saddr);
151 __be16 uninitialized_var(dport), uninitialized_var(sport);
152 u8 uninitialized_var(protocol);
153 #ifdef XT_SOCKET_HAVE_CONNTRACK
154 struct nf_conn const *ct;
155 enum ip_conntrack_info ctinfo;
158 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
159 struct udphdr _hdr, *hp;
161 hp = skb_header_pointer(skb, ip_hdrlen(skb),
162 sizeof(_hdr), &_hdr);
166 protocol = iph->protocol;
172 } else if (iph->protocol == IPPROTO_ICMP) {
173 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
180 #ifdef XT_SOCKET_HAVE_CONNTRACK
181 /* Do the lookup with the original socket address in
182 * case this is a reply packet of an established
183 * SNAT-ted connection.
185 ct = nf_ct_get(skb, &ctinfo);
186 if (ct && !nf_ct_is_untracked(ct) &&
187 ((iph->protocol != IPPROTO_ICMP &&
188 ctinfo == IP_CT_ESTABLISHED_REPLY) ||
189 (iph->protocol == IPPROTO_ICMP &&
190 ctinfo == IP_CT_RELATED_REPLY)) &&
191 (ct->status & IPS_SRC_NAT_DONE)) {
193 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
194 dport = (iph->protocol == IPPROTO_TCP) ?
195 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
196 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
200 return xt_socket_get_sock_v4(dev_net(skb->dev), protocol, saddr, daddr,
201 sport, dport, indev);
205 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
206 const struct xt_socket_mtinfo1 *info)
208 struct sock *sk = skb->sk;
211 sk = xt_socket_lookup_slow_v4(skb, par->in);
214 bool transparent = true;
216 /* Ignore sockets listening on INADDR_ANY,
217 * unless XT_SOCKET_NOWILDCARD is set
219 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
221 inet_sk(sk)->inet_rcv_saddr == 0);
223 /* Ignore non-transparent sockets,
224 * if XT_SOCKET_TRANSPARENT is used
226 if (info->flags & XT_SOCKET_TRANSPARENT)
227 transparent = xt_socket_sk_is_transparent(sk);
232 if (wildcard || !transparent)
240 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
242 static struct xt_socket_mtinfo1 xt_info_v0 = {
246 return socket_match(skb, par, &xt_info_v0);
250 socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
252 return socket_match(skb, par, par->matchinfo);
255 #ifdef XT_SOCKET_HAVE_IPV6
258 extract_icmp6_fields(const struct sk_buff *skb,
259 unsigned int outside_hdrlen,
261 const struct in6_addr **raddr,
262 const struct in6_addr **laddr,
265 struct ipv6hdr *ipv6_var)
267 const struct ipv6hdr *inside_iph;
268 struct icmp6hdr *icmph, _icmph;
269 __be16 *ports, _ports[2];
271 __be16 inside_fragoff;
274 icmph = skb_header_pointer(skb, outside_hdrlen,
275 sizeof(_icmph), &_icmph);
279 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
282 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph),
283 sizeof(*ipv6_var), ipv6_var);
284 if (inside_iph == NULL)
286 inside_nexthdr = inside_iph->nexthdr;
288 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) +
290 &inside_nexthdr, &inside_fragoff);
291 if (inside_hdrlen < 0)
292 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
294 if (inside_nexthdr != IPPROTO_TCP &&
295 inside_nexthdr != IPPROTO_UDP)
298 ports = skb_header_pointer(skb, inside_hdrlen,
299 sizeof(_ports), &_ports);
303 /* the inside IP packet is the one quoted from our side, thus
304 * its saddr is the local address */
305 *protocol = inside_nexthdr;
306 *laddr = &inside_iph->saddr;
308 *raddr = &inside_iph->daddr;
315 xt_socket_get_sock_v6(struct net *net, const u8 protocol,
316 const struct in6_addr *saddr, const struct in6_addr *daddr,
317 const __be16 sport, const __be16 dport,
318 const struct net_device *in)
322 return inet6_lookup(net, &tcp_hashinfo,
323 saddr, sport, daddr, dport,
326 return udp6_lib_lookup(net, saddr, sport, daddr, dport,
333 static struct sock *xt_socket_lookup_slow_v6(const struct sk_buff *skb,
334 const struct net_device *indev)
336 __be16 uninitialized_var(dport), uninitialized_var(sport);
337 const struct in6_addr *daddr = NULL, *saddr = NULL;
338 struct ipv6hdr *iph = ipv6_hdr(skb);
339 int thoff = 0, tproto;
341 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
343 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
347 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
348 struct udphdr _hdr, *hp;
350 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
359 } else if (tproto == IPPROTO_ICMPV6) {
360 struct ipv6hdr ipv6_var;
362 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
363 &sport, &dport, &ipv6_var))
369 return xt_socket_get_sock_v6(dev_net(skb->dev), tproto, saddr, daddr,
370 sport, dport, indev);
374 socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
376 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
377 struct sock *sk = skb->sk;
380 sk = xt_socket_lookup_slow_v6(skb, par->in);
383 bool transparent = true;
385 /* Ignore sockets listening on INADDR_ANY
386 * unless XT_SOCKET_NOWILDCARD is set
388 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
390 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
392 /* Ignore non-transparent sockets,
393 * if XT_SOCKET_TRANSPARENT is used
395 if (info->flags & XT_SOCKET_TRANSPARENT)
396 transparent = xt_socket_sk_is_transparent(sk);
401 if (wildcard || !transparent)
409 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
411 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
413 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
414 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
420 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
422 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
424 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
425 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
431 static struct xt_match socket_mt_reg[] __read_mostly = {
435 .family = NFPROTO_IPV4,
436 .match = socket_mt4_v0,
437 .hooks = (1 << NF_INET_PRE_ROUTING) |
438 (1 << NF_INET_LOCAL_IN),
444 .family = NFPROTO_IPV4,
445 .match = socket_mt4_v1_v2,
446 .checkentry = socket_mt_v1_check,
447 .matchsize = sizeof(struct xt_socket_mtinfo1),
448 .hooks = (1 << NF_INET_PRE_ROUTING) |
449 (1 << NF_INET_LOCAL_IN),
452 #ifdef XT_SOCKET_HAVE_IPV6
456 .family = NFPROTO_IPV6,
457 .match = socket_mt6_v1_v2,
458 .checkentry = socket_mt_v1_check,
459 .matchsize = sizeof(struct xt_socket_mtinfo1),
460 .hooks = (1 << NF_INET_PRE_ROUTING) |
461 (1 << NF_INET_LOCAL_IN),
468 .family = NFPROTO_IPV4,
469 .match = socket_mt4_v1_v2,
470 .checkentry = socket_mt_v2_check,
471 .matchsize = sizeof(struct xt_socket_mtinfo1),
472 .hooks = (1 << NF_INET_PRE_ROUTING) |
473 (1 << NF_INET_LOCAL_IN),
476 #ifdef XT_SOCKET_HAVE_IPV6
480 .family = NFPROTO_IPV6,
481 .match = socket_mt6_v1_v2,
482 .checkentry = socket_mt_v2_check,
483 .matchsize = sizeof(struct xt_socket_mtinfo1),
484 .hooks = (1 << NF_INET_PRE_ROUTING) |
485 (1 << NF_INET_LOCAL_IN),
491 static int __init socket_mt_init(void)
493 nf_defrag_ipv4_enable();
494 #ifdef XT_SOCKET_HAVE_IPV6
495 nf_defrag_ipv6_enable();
498 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
501 static void __exit socket_mt_exit(void)
503 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
506 module_init(socket_mt_init);
507 module_exit(socket_mt_exit);
509 MODULE_LICENSE("GPL");
510 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
511 MODULE_DESCRIPTION("x_tables socket match module");
512 MODULE_ALIAS("ipt_socket");
513 MODULE_ALIAS("ip6t_socket");