1 /*
2 * Transparent proxy support for Linux/iptables
3 *
4 * Copyright (C) 2007-2008 BalaBit IT Ltd.
5 * Author: Krisztian Kovacs
6 *
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.
10 *
11 */
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>
17 #include <net/tcp.h>
18 #include <net/udp.h>
19 #include <net/icmp.h>
20 #include <net/sock.h>
21 #include <net/inet_sock.h>
22 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
23
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>
28 #endif
29
30 #include <net/netfilter/nf_socket.h>
31 #include <linux/netfilter/xt_socket.h>
32
33 /* "socket" match based redirection (no specific rule)
34 * ===================================================
35 *
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:
43 *
44 * - match: if there's a fully established connection matching the
45 * _packet_ tuple
46 *
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
50 * box.
51 */
52 static bool
socket_match(const struct sk_buff * skb,struct xt_action_param * par,const struct xt_socket_mtinfo1 * info)53 socket_match(const struct sk_buff *skb, struct xt_action_param *par,
54 const struct xt_socket_mtinfo1 *info)
55 {
56 struct sk_buff *pskb = (struct sk_buff *)skb;
57 struct sock *sk = skb->sk;
58
59 if (sk && !net_eq(xt_net(par), sock_net(sk)))
60 sk = NULL;
61
62 if (!sk)
63 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
64
65 if (sk) {
66 bool wildcard;
67 bool transparent = true;
68
69 /* Ignore sockets listening on INADDR_ANY,
70 * unless XT_SOCKET_NOWILDCARD is set
71 */
72 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
73 sk_fullsock(sk) &&
74 inet_sk(sk)->inet_rcv_saddr == 0);
75
76 /* Ignore non-transparent sockets,
77 * if XT_SOCKET_TRANSPARENT is used
78 */
79 if (info->flags & XT_SOCKET_TRANSPARENT)
80 transparent = inet_sk_transparent(sk);
81
82 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
83 transparent && sk_fullsock(sk))
84 pskb->mark = sk->sk_mark;
85
86 if (sk != skb->sk)
87 sock_gen_put(sk);
88
89 if (wildcard || !transparent)
90 sk = NULL;
91 }
92
93 return sk != NULL;
94 }
95
96 static bool
socket_mt4_v0(const struct sk_buff * skb,struct xt_action_param * par)97 socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
98 {
99 static struct xt_socket_mtinfo1 xt_info_v0 = {
100 .flags = 0,
101 };
102
103 return socket_match(skb, par, &xt_info_v0);
104 }
105
106 static bool
socket_mt4_v1_v2_v3(const struct sk_buff * skb,struct xt_action_param * par)107 socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
108 {
109 return socket_match(skb, par, par->matchinfo);
110 }
111
112 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
113 static bool
socket_mt6_v1_v2_v3(const struct sk_buff * skb,struct xt_action_param * par)114 socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
115 {
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;
119
120 if (sk && !net_eq(xt_net(par), sock_net(sk)))
121 sk = NULL;
122
123 if (!sk)
124 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
125
126 if (sk) {
127 bool wildcard;
128 bool transparent = true;
129
130 /* Ignore sockets listening on INADDR_ANY
131 * unless XT_SOCKET_NOWILDCARD is set
132 */
133 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
134 sk_fullsock(sk) &&
135 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
136
137 /* Ignore non-transparent sockets,
138 * if XT_SOCKET_TRANSPARENT is used
139 */
140 if (info->flags & XT_SOCKET_TRANSPARENT)
141 transparent = inet_sk_transparent(sk);
142
143 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
144 transparent && sk_fullsock(sk))
145 pskb->mark = sk->sk_mark;
146
147 if (sk != skb->sk)
148 sock_gen_put(sk);
149
150 if (wildcard || !transparent)
151 sk = NULL;
152 }
153
154 return sk != NULL;
155 }
156 #endif
157
socket_mt_enable_defrag(struct net * net,int family)158 static int socket_mt_enable_defrag(struct net *net, int family)
159 {
160 switch (family) {
161 case NFPROTO_IPV4:
162 return nf_defrag_ipv4_enable(net);
163 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
164 case NFPROTO_IPV6:
165 return nf_defrag_ipv6_enable(net);
166 #endif
167 }
168 WARN_ONCE(1, "Unknown family %d\n", family);
169 return 0;
170 }
171
socket_mt_v1_check(const struct xt_mtchk_param * par)172 static int socket_mt_v1_check(const struct xt_mtchk_param *par)
173 {
174 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
175 int err;
176
177 err = socket_mt_enable_defrag(par->net, par->family);
178 if (err)
179 return err;
180
181 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
182 pr_info_ratelimited("unknown flags 0x%x\n",
183 info->flags & ~XT_SOCKET_FLAGS_V1);
184 return -EINVAL;
185 }
186 return 0;
187 }
188
socket_mt_v2_check(const struct xt_mtchk_param * par)189 static int socket_mt_v2_check(const struct xt_mtchk_param *par)
190 {
191 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
192 int err;
193
194 err = socket_mt_enable_defrag(par->net, par->family);
195 if (err)
196 return err;
197
198 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
199 pr_info_ratelimited("unknown flags 0x%x\n",
200 info->flags & ~XT_SOCKET_FLAGS_V2);
201 return -EINVAL;
202 }
203 return 0;
204 }
205
socket_mt_v3_check(const struct xt_mtchk_param * par)206 static int socket_mt_v3_check(const struct xt_mtchk_param *par)
207 {
208 const struct xt_socket_mtinfo3 *info =
209 (struct xt_socket_mtinfo3 *)par->matchinfo;
210 int err;
211
212 err = socket_mt_enable_defrag(par->net, par->family);
213 if (err)
214 return err;
215 if (info->flags & ~XT_SOCKET_FLAGS_V3) {
216 pr_info_ratelimited("unknown flags 0x%x\n",
217 info->flags & ~XT_SOCKET_FLAGS_V3);
218 return -EINVAL;
219 }
220 return 0;
221 }
222
223 static struct xt_match socket_mt_reg[] __read_mostly = {
224 {
225 .name = "socket",
226 .revision = 0,
227 .family = NFPROTO_IPV4,
228 .match = socket_mt4_v0,
229 .hooks = (1 << NF_INET_PRE_ROUTING) |
230 (1 << NF_INET_LOCAL_IN),
231 .me = THIS_MODULE,
232 },
233 {
234 .name = "socket",
235 .revision = 1,
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),
242 .me = THIS_MODULE,
243 },
244 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
245 {
246 .name = "socket",
247 .revision = 1,
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),
254 .me = THIS_MODULE,
255 },
256 #endif
257 {
258 .name = "socket",
259 .revision = 2,
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),
266 .me = THIS_MODULE,
267 },
268 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
269 {
270 .name = "socket",
271 .revision = 2,
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),
278 .me = THIS_MODULE,
279 },
280 #endif
281 {
282 .name = "socket",
283 .revision = 3,
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),
290 .me = THIS_MODULE,
291 },
292 #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
293 {
294 .name = "socket",
295 .revision = 3,
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),
302 .me = THIS_MODULE,
303 },
304 #endif
305 };
306
socket_mt_init(void)307 static int __init socket_mt_init(void)
308 {
309 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
310 }
311
socket_mt_exit(void)312 static void __exit socket_mt_exit(void)
313 {
314 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
315 }
316
317 module_init(socket_mt_init);
318 module_exit(socket_mt_exit);
319
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");
325
