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d2912cb1 1// SPDX-License-Identifier: GPL-2.0-only
136cdc71
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2/*
3 * Transparent proxy support for Linux/iptables
4 *
5 * Copyright (C) 2007-2008 BalaBit IT Ltd.
6 * Author: Krisztian Kovacs
136cdc71 7 */
ff67e4e4 8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
136cdc71
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9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/netfilter/x_tables.h>
12#include <linux/netfilter_ipv4/ip_tables.h>
13#include <net/tcp.h>
14#include <net/udp.h>
15#include <net/icmp.h>
16#include <net/sock.h>
17#include <net/inet_sock.h>
136cdc71 18#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
f6318e55 19
c0cd1156 20#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
f6318e55 21#include <linux/netfilter_ipv6/ip6_tables.h>
93742cf8 22#include <net/inet6_hashtables.h>
b64c9256 23#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
f6318e55 24#endif
136cdc71 25
8db4c5be 26#include <net/netfilter/nf_socket.h>
a31e1ffd
LAT
27#include <linux/netfilter/xt_socket.h>
28
93742cf8
FW
29/* "socket" match based redirection (no specific rule)
30 * ===================================================
31 *
32 * There are connections with dynamic endpoints (e.g. FTP data
33 * connection) that the user is unable to add explicit rules
34 * for. These are taken care of by a generic "socket" rule. It is
35 * assumed that the proxy application is trusted to open such
36 * connections without explicit iptables rule (except of course the
37 * generic 'socket' rule). In this case the following sockets are
38 * matched in preference order:
39 *
40 * - match: if there's a fully established connection matching the
41 * _packet_ tuple
42 *
43 * - match: if there's a non-zero bound listener (possibly with a
44 * non-local address) We don't accept zero-bound listeners, since
45 * then local services could intercept traffic going through the
46 * box.
47 */
d64d80a2
DB
48static bool
49socket_match(const struct sk_buff *skb, struct xt_action_param *par,
50 const struct xt_socket_mtinfo1 *info)
51{
01555e74 52 struct sk_buff *pskb = (struct sk_buff *)skb;
d64d80a2
DB
53 struct sock *sk = skb->sk;
54
40e4f26e 55 if (sk && !net_eq(xt_net(par), sock_net(sk)))
f5646501
FL
56 sk = NULL;
57
00028aa3 58 if (!sk)
613dbd95 59 sk = nf_sk_lookup_slow_v4(xt_net(par), skb, xt_in(par));
f5646501 60
00028aa3 61 if (sk) {
a31e1ffd
LAT
62 bool wildcard;
63 bool transparent = true;
64
681f130f
ED
65 /* Ignore sockets listening on INADDR_ANY,
66 * unless XT_SOCKET_NOWILDCARD is set
67 */
68 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
a9407000 69 sk_fullsock(sk) &&
c720c7e8 70 inet_sk(sk)->inet_rcv_saddr == 0);
a31e1ffd
LAT
71
72 /* Ignore non-transparent sockets,
a9407000
ED
73 * if XT_SOCKET_TRANSPARENT is used
74 */
baf60efa 75 if (info->flags & XT_SOCKET_TRANSPARENT)
8d6e5557 76 transparent = inet_sk_transparent(sk);
136cdc71 77
01555e74 78 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
89fcbb56 79 transparent && sk_fullsock(sk))
01555e74
HH
80 pskb->mark = sk->sk_mark;
81
00028aa3 82 if (sk != skb->sk)
1a8bf6ee 83 sock_gen_put(sk);
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84
85 if (wildcard || !transparent)
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86 sk = NULL;
87 }
88
d64d80a2 89 return sk != NULL;
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90}
91
a31e1ffd 92static bool
b64c9256 93socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
a31e1ffd 94{
baf60efa
ED
95 static struct xt_socket_mtinfo1 xt_info_v0 = {
96 .flags = 0,
97 };
98
99 return socket_match(skb, par, &xt_info_v0);
a31e1ffd
LAT
100}
101
102static bool
01555e74 103socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
a31e1ffd
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104{
105 return socket_match(skb, par, par->matchinfo);
106}
107
8db4c5be 108#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
d64d80a2 109static bool
01555e74 110socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
d64d80a2
DB
111{
112 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
01555e74 113 struct sk_buff *pskb = (struct sk_buff *)skb;
d64d80a2
DB
114 struct sock *sk = skb->sk;
115
40e4f26e 116 if (sk && !net_eq(xt_net(par), sock_net(sk)))
f5646501
FL
117 sk = NULL;
118
00028aa3 119 if (!sk)
613dbd95 120 sk = nf_sk_lookup_slow_v6(xt_net(par), skb, xt_in(par));
f5646501 121
00028aa3 122 if (sk) {
b64c9256
BS
123 bool wildcard;
124 bool transparent = true;
125
681f130f
ED
126 /* Ignore sockets listening on INADDR_ANY
127 * unless XT_SOCKET_NOWILDCARD is set
128 */
129 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
a9407000 130 sk_fullsock(sk) &&
efe4208f 131 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
b64c9256
BS
132
133 /* Ignore non-transparent sockets,
a9407000
ED
134 * if XT_SOCKET_TRANSPARENT is used
135 */
baf60efa 136 if (info->flags & XT_SOCKET_TRANSPARENT)
8d6e5557 137 transparent = inet_sk_transparent(sk);
b64c9256 138
01555e74 139 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
89fcbb56 140 transparent && sk_fullsock(sk))
01555e74
HH
141 pskb->mark = sk->sk_mark;
142
00028aa3 143 if (sk != skb->sk)
1a8bf6ee 144 sock_gen_put(sk);
b64c9256
BS
145
146 if (wildcard || !transparent)
147 sk = NULL;
148 }
149
d64d80a2 150 return sk != NULL;
b64c9256
BS
151}
152#endif
153
834184b1
FW
154static int socket_mt_enable_defrag(struct net *net, int family)
155{
156 switch (family) {
157 case NFPROTO_IPV4:
158 return nf_defrag_ipv4_enable(net);
6bd3d192 159#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
834184b1
FW
160 case NFPROTO_IPV6:
161 return nf_defrag_ipv6_enable(net);
162#endif
163 }
164 WARN_ONCE(1, "Unknown family %d\n", family);
165 return 0;
166}
167
681f130f
ED
168static int socket_mt_v1_check(const struct xt_mtchk_param *par)
169{
170 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
834184b1
FW
171 int err;
172
173 err = socket_mt_enable_defrag(par->net, par->family);
174 if (err)
175 return err;
681f130f
ED
176
177 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
b2606644
FW
178 pr_info_ratelimited("unknown flags 0x%x\n",
179 info->flags & ~XT_SOCKET_FLAGS_V1);
681f130f
ED
180 return -EINVAL;
181 }
182 return 0;
183}
184
185static int socket_mt_v2_check(const struct xt_mtchk_param *par)
186{
187 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
834184b1
FW
188 int err;
189
190 err = socket_mt_enable_defrag(par->net, par->family);
191 if (err)
192 return err;
681f130f
ED
193
194 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
b2606644
FW
195 pr_info_ratelimited("unknown flags 0x%x\n",
196 info->flags & ~XT_SOCKET_FLAGS_V2);
681f130f
ED
197 return -EINVAL;
198 }
199 return 0;
200}
201
01555e74
HH
202static int socket_mt_v3_check(const struct xt_mtchk_param *par)
203{
204 const struct xt_socket_mtinfo3 *info =
205 (struct xt_socket_mtinfo3 *)par->matchinfo;
834184b1 206 int err;
01555e74 207
834184b1
FW
208 err = socket_mt_enable_defrag(par->net, par->family);
209 if (err)
210 return err;
01555e74 211 if (info->flags & ~XT_SOCKET_FLAGS_V3) {
b2606644
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212 pr_info_ratelimited("unknown flags 0x%x\n",
213 info->flags & ~XT_SOCKET_FLAGS_V3);
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214 return -EINVAL;
215 }
216 return 0;
217}
218
a31e1ffd
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219static struct xt_match socket_mt_reg[] __read_mostly = {
220 {
221 .name = "socket",
222 .revision = 0,
223 .family = NFPROTO_IPV4,
b64c9256 224 .match = socket_mt4_v0,
aa3c487f
JE
225 .hooks = (1 << NF_INET_PRE_ROUTING) |
226 (1 << NF_INET_LOCAL_IN),
a31e1ffd
LAT
227 .me = THIS_MODULE,
228 },
229 {
230 .name = "socket",
231 .revision = 1,
232 .family = NFPROTO_IPV4,
01555e74 233 .match = socket_mt4_v1_v2_v3,
681f130f 234 .checkentry = socket_mt_v1_check,
a31e1ffd 235 .matchsize = sizeof(struct xt_socket_mtinfo1),
aa3c487f
JE
236 .hooks = (1 << NF_INET_PRE_ROUTING) |
237 (1 << NF_INET_LOCAL_IN),
a31e1ffd
LAT
238 .me = THIS_MODULE,
239 },
8db4c5be 240#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
b64c9256
BS
241 {
242 .name = "socket",
243 .revision = 1,
244 .family = NFPROTO_IPV6,
01555e74 245 .match = socket_mt6_v1_v2_v3,
681f130f
ED
246 .checkentry = socket_mt_v1_check,
247 .matchsize = sizeof(struct xt_socket_mtinfo1),
248 .hooks = (1 << NF_INET_PRE_ROUTING) |
249 (1 << NF_INET_LOCAL_IN),
250 .me = THIS_MODULE,
251 },
252#endif
253 {
254 .name = "socket",
255 .revision = 2,
256 .family = NFPROTO_IPV4,
01555e74 257 .match = socket_mt4_v1_v2_v3,
681f130f
ED
258 .checkentry = socket_mt_v2_check,
259 .matchsize = sizeof(struct xt_socket_mtinfo1),
260 .hooks = (1 << NF_INET_PRE_ROUTING) |
261 (1 << NF_INET_LOCAL_IN),
262 .me = THIS_MODULE,
263 },
8db4c5be 264#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
681f130f
ED
265 {
266 .name = "socket",
267 .revision = 2,
268 .family = NFPROTO_IPV6,
01555e74 269 .match = socket_mt6_v1_v2_v3,
681f130f 270 .checkentry = socket_mt_v2_check,
b64c9256
BS
271 .matchsize = sizeof(struct xt_socket_mtinfo1),
272 .hooks = (1 << NF_INET_PRE_ROUTING) |
273 (1 << NF_INET_LOCAL_IN),
274 .me = THIS_MODULE,
275 },
01555e74
HH
276#endif
277 {
278 .name = "socket",
279 .revision = 3,
280 .family = NFPROTO_IPV4,
281 .match = socket_mt4_v1_v2_v3,
282 .checkentry = socket_mt_v3_check,
283 .matchsize = sizeof(struct xt_socket_mtinfo1),
284 .hooks = (1 << NF_INET_PRE_ROUTING) |
285 (1 << NF_INET_LOCAL_IN),
286 .me = THIS_MODULE,
287 },
8db4c5be 288#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
01555e74
HH
289 {
290 .name = "socket",
291 .revision = 3,
292 .family = NFPROTO_IPV6,
293 .match = socket_mt6_v1_v2_v3,
294 .checkentry = socket_mt_v3_check,
295 .matchsize = sizeof(struct xt_socket_mtinfo1),
296 .hooks = (1 << NF_INET_PRE_ROUTING) |
297 (1 << NF_INET_LOCAL_IN),
298 .me = THIS_MODULE,
299 },
b64c9256 300#endif
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301};
302
303static int __init socket_mt_init(void)
304{
a31e1ffd 305 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
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306}
307
308static void __exit socket_mt_exit(void)
309{
a31e1ffd 310 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
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311}
312
313module_init(socket_mt_init);
314module_exit(socket_mt_exit);
315
316MODULE_LICENSE("GPL");
317MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
318MODULE_DESCRIPTION("x_tables socket match module");
319MODULE_ALIAS("ipt_socket");
b64c9256 320MODULE_ALIAS("ip6t_socket");