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;
59 if (sk && !net_eq(xt_net(par), sock_net(sk)))
63 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
67 bool transparent = true;
69 /* Ignore sockets listening on INADDR_ANY,
70 * unless XT_SOCKET_NOWILDCARD is set
72 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
74 inet_sk(sk)->inet_rcv_saddr == 0);
76 /* Ignore non-transparent sockets,
77 * if XT_SOCKET_TRANSPARENT is used
79 if (info->flags & XT_SOCKET_TRANSPARENT)
80 transparent = inet_sk_transparent(sk);
82 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
83 transparent && sk_fullsock(sk))
84 pskb->mark = sk->sk_mark;
89 if (wildcard || !transparent)
97 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
99 static struct xt_socket_mtinfo1 xt_info_v0 = {
103 return socket_match(skb, par, &xt_info_v0);
107 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
109 return socket_match(skb, par, par->matchinfo);
112 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
114 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
116 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
117 struct sk_buff *pskb = (struct sk_buff *)skb;
118 struct sock *sk = skb->sk;
120 if (sk && !net_eq(xt_net(par), sock_net(sk)))
124 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
128 bool transparent = true;
130 /* Ignore sockets listening on INADDR_ANY
131 * unless XT_SOCKET_NOWILDCARD is set
133 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
135 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
137 /* Ignore non-transparent sockets,
138 * if XT_SOCKET_TRANSPARENT is used
140 if (info->flags & XT_SOCKET_TRANSPARENT)
141 transparent = inet_sk_transparent(sk);
143 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
144 transparent && sk_fullsock(sk))
145 pskb->mark = sk->sk_mark;
150 if (wildcard || !transparent)
158 static int socket_mt_enable_defrag(struct net *net, int family)
162 return nf_defrag_ipv4_enable(net);
163 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
165 return nf_defrag_ipv6_enable(net);
168 WARN_ONCE(1, "Unknown family %d\n", family);
172 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
174 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
177 err = socket_mt_enable_defrag(par->net, par->family);
181 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
182 pr_info_ratelimited("unknown flags 0x%x\n",
183 info->flags & ~XT_SOCKET_FLAGS_V1);
189 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
191 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
194 err = socket_mt_enable_defrag(par->net, par->family);
198 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
199 pr_info_ratelimited("unknown flags 0x%x\n",
200 info->flags & ~XT_SOCKET_FLAGS_V2);
206 static int socket_mt_v3_check(const struct xt_mtchk_param *par)
208 const struct xt_socket_mtinfo3 *info =
209 (struct xt_socket_mtinfo3 *)par->matchinfo;
212 err = socket_mt_enable_defrag(par->net, par->family);
215 if (info->flags & ~XT_SOCKET_FLAGS_V3) {
216 pr_info_ratelimited("unknown flags 0x%x\n",
217 info->flags & ~XT_SOCKET_FLAGS_V3);
223 static struct xt_match socket_mt_reg[] __read_mostly = {
227 .family = NFPROTO_IPV4,
228 .match = socket_mt4_v0,
229 .hooks = (1 << NF_INET_PRE_ROUTING) |
230 (1 << NF_INET_LOCAL_IN),
236 .family = NFPROTO_IPV4,
237 .match = socket_mt4_v1_v2_v3,
238 .checkentry = socket_mt_v1_check,
239 .matchsize = sizeof(struct xt_socket_mtinfo1),
240 .hooks = (1 << NF_INET_PRE_ROUTING) |
241 (1 << NF_INET_LOCAL_IN),
244 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
248 .family = NFPROTO_IPV6,
249 .match = socket_mt6_v1_v2_v3,
250 .checkentry = socket_mt_v1_check,
251 .matchsize = sizeof(struct xt_socket_mtinfo1),
252 .hooks = (1 << NF_INET_PRE_ROUTING) |
253 (1 << NF_INET_LOCAL_IN),
260 .family = NFPROTO_IPV4,
261 .match = socket_mt4_v1_v2_v3,
262 .checkentry = socket_mt_v2_check,
263 .matchsize = sizeof(struct xt_socket_mtinfo1),
264 .hooks = (1 << NF_INET_PRE_ROUTING) |
265 (1 << NF_INET_LOCAL_IN),
268 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
272 .family = NFPROTO_IPV6,
273 .match = socket_mt6_v1_v2_v3,
274 .checkentry = socket_mt_v2_check,
275 .matchsize = sizeof(struct xt_socket_mtinfo1),
276 .hooks = (1 << NF_INET_PRE_ROUTING) |
277 (1 << NF_INET_LOCAL_IN),
284 .family = NFPROTO_IPV4,
285 .match = socket_mt4_v1_v2_v3,
286 .checkentry = socket_mt_v3_check,
287 .matchsize = sizeof(struct xt_socket_mtinfo1),
288 .hooks = (1 << NF_INET_PRE_ROUTING) |
289 (1 << NF_INET_LOCAL_IN),
292 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
296 .family = NFPROTO_IPV6,
297 .match = socket_mt6_v1_v2_v3,
298 .checkentry = socket_mt_v3_check,
299 .matchsize = sizeof(struct xt_socket_mtinfo1),
300 .hooks = (1 << NF_INET_PRE_ROUTING) |
301 (1 << NF_INET_LOCAL_IN),
307 static int __init socket_mt_init(void)
309 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
312 static void __exit socket_mt_exit(void)
314 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
317 module_init(socket_mt_init);
318 module_exit(socket_mt_exit);
320 MODULE_LICENSE("GPL");
321 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
322 MODULE_DESCRIPTION("x_tables socket match module");
323 MODULE_ALIAS("ipt_socket");
324 MODULE_ALIAS("ip6t_socket");