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 #include <linux/netfilter_ipv6/ip6_tables.h>
26 #include <net/inet6_hashtables.h>
27 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
30 #include <net/netfilter/nf_socket.h>
31 #include <linux/netfilter/xt_socket.h>
33 /* "socket" match based redirection (no specific rule)
34 * ===================================================
36 * There are connections with dynamic endpoints (e.g. FTP data
37 * connection) that the user is unable to add explicit rules
38 * for. These are taken care of by a generic "socket" rule. It is
39 * assumed that the proxy application is trusted to open such
40 * connections without explicit iptables rule (except of course the
41 * generic 'socket' rule). In this case the following sockets are
42 * matched in preference order:
44 * - match: if there's a fully established connection matching the
47 * - match: if there's a non-zero bound listener (possibly with a
48 * non-local address) We don't accept zero-bound listeners, since
49 * then local services could intercept traffic going through the
53 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
54 const struct xt_socket_mtinfo1 *info)
56 struct sk_buff *pskb = (struct sk_buff *)skb;
57 struct sock *sk = skb->sk;
60 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
63 bool transparent = true;
65 /* Ignore sockets listening on INADDR_ANY,
66 * unless XT_SOCKET_NOWILDCARD is set
68 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
70 inet_sk(sk)->inet_rcv_saddr == 0);
72 /* Ignore non-transparent sockets,
73 * if XT_SOCKET_TRANSPARENT is used
75 if (info->flags & XT_SOCKET_TRANSPARENT)
76 transparent = nf_sk_is_transparent(sk);
78 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
80 pskb->mark = sk->sk_mark;
85 if (wildcard || !transparent)
93 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
95 static struct xt_socket_mtinfo1 xt_info_v0 = {
99 return socket_match(skb, par, &xt_info_v0);
103 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
105 return socket_match(skb, par, par->matchinfo);
108 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
110 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
112 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
113 struct sk_buff *pskb = (struct sk_buff *)skb;
114 struct sock *sk = skb->sk;
117 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
120 bool transparent = true;
122 /* Ignore sockets listening on INADDR_ANY
123 * unless XT_SOCKET_NOWILDCARD is set
125 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
127 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
129 /* Ignore non-transparent sockets,
130 * if XT_SOCKET_TRANSPARENT is used
132 if (info->flags & XT_SOCKET_TRANSPARENT)
133 transparent = nf_sk_is_transparent(sk);
135 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
137 pskb->mark = sk->sk_mark;
142 if (wildcard || !transparent)
150 static int socket_mt_enable_defrag(struct net *net, int family)
154 return nf_defrag_ipv4_enable(net);
155 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
157 return nf_defrag_ipv6_enable(net);
160 WARN_ONCE(1, "Unknown family %d\n", family);
164 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
166 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
169 err = socket_mt_enable_defrag(par->net, par->family);
173 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
174 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
180 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
182 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
185 err = socket_mt_enable_defrag(par->net, par->family);
189 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
190 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
196 static int socket_mt_v3_check(const struct xt_mtchk_param *par)
198 const struct xt_socket_mtinfo3 *info =
199 (struct xt_socket_mtinfo3 *)par->matchinfo;
202 err = socket_mt_enable_defrag(par->net, par->family);
205 if (info->flags & ~XT_SOCKET_FLAGS_V3) {
206 pr_info("unknown flags 0x%x\n",
207 info->flags & ~XT_SOCKET_FLAGS_V3);
213 static struct xt_match socket_mt_reg[] __read_mostly = {
217 .family = NFPROTO_IPV4,
218 .match = socket_mt4_v0,
219 .hooks = (1 << NF_INET_PRE_ROUTING) |
220 (1 << NF_INET_LOCAL_IN),
226 .family = NFPROTO_IPV4,
227 .match = socket_mt4_v1_v2_v3,
228 .checkentry = socket_mt_v1_check,
229 .matchsize = sizeof(struct xt_socket_mtinfo1),
230 .hooks = (1 << NF_INET_PRE_ROUTING) |
231 (1 << NF_INET_LOCAL_IN),
234 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
238 .family = NFPROTO_IPV6,
239 .match = socket_mt6_v1_v2_v3,
240 .checkentry = socket_mt_v1_check,
241 .matchsize = sizeof(struct xt_socket_mtinfo1),
242 .hooks = (1 << NF_INET_PRE_ROUTING) |
243 (1 << NF_INET_LOCAL_IN),
250 .family = NFPROTO_IPV4,
251 .match = socket_mt4_v1_v2_v3,
252 .checkentry = socket_mt_v2_check,
253 .matchsize = sizeof(struct xt_socket_mtinfo1),
254 .hooks = (1 << NF_INET_PRE_ROUTING) |
255 (1 << NF_INET_LOCAL_IN),
258 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
262 .family = NFPROTO_IPV6,
263 .match = socket_mt6_v1_v2_v3,
264 .checkentry = socket_mt_v2_check,
265 .matchsize = sizeof(struct xt_socket_mtinfo1),
266 .hooks = (1 << NF_INET_PRE_ROUTING) |
267 (1 << NF_INET_LOCAL_IN),
274 .family = NFPROTO_IPV4,
275 .match = socket_mt4_v1_v2_v3,
276 .checkentry = socket_mt_v3_check,
277 .matchsize = sizeof(struct xt_socket_mtinfo1),
278 .hooks = (1 << NF_INET_PRE_ROUTING) |
279 (1 << NF_INET_LOCAL_IN),
282 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
286 .family = NFPROTO_IPV6,
287 .match = socket_mt6_v1_v2_v3,
288 .checkentry = socket_mt_v3_check,
289 .matchsize = sizeof(struct xt_socket_mtinfo1),
290 .hooks = (1 << NF_INET_PRE_ROUTING) |
291 (1 << NF_INET_LOCAL_IN),
297 static int __init socket_mt_init(void)
299 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
302 static void __exit socket_mt_exit(void)
304 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
307 module_init(socket_mt_init);
308 module_exit(socket_mt_exit);
310 MODULE_LICENSE("GPL");
311 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
312 MODULE_DESCRIPTION("x_tables socket match module");
313 MODULE_ALIAS("ipt_socket");
314 MODULE_ALIAS("ip6t_socket");