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e8439270 KK |
1 | /* |
2 | * Transparent proxy support for Linux/iptables | |
3 | * | |
6ad78893 | 4 | * Copyright (c) 2006-2010 BalaBit IT Ltd. |
e8439270 KK |
5 | * Author: Balazs Scheidler, 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 | */ | |
ff67e4e4 | 12 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
e8439270 KK |
13 | #include <linux/module.h> |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/ip.h> | |
16 | #include <net/checksum.h> | |
17 | #include <net/udp.h> | |
18 | #include <net/inet_sock.h> | |
cc6eb433 | 19 | #include <linux/inetdevice.h> |
e8439270 KK |
20 | #include <linux/netfilter/x_tables.h> |
21 | #include <linux/netfilter_ipv4/ip_tables.h> | |
e8439270 KK |
22 | |
23 | #include <net/netfilter/ipv4/nf_defrag_ipv4.h> | |
f6318e55 | 24 | |
c0cd1156 | 25 | #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) |
f6318e55 | 26 | #define XT_TPROXY_HAVE_IPV6 1 |
cc6eb433 BS |
27 | #include <net/if_inet6.h> |
28 | #include <net/addrconf.h> | |
29 | #include <linux/netfilter_ipv6/ip6_tables.h> | |
6ad78893 | 30 | #include <net/netfilter/ipv6/nf_defrag_ipv6.h> |
cc6eb433 BS |
31 | #endif |
32 | ||
e8439270 | 33 | #include <net/netfilter/nf_tproxy_core.h> |
cc6eb433 BS |
34 | #include <linux/netfilter/xt_TPROXY.h> |
35 | ||
d503b30b FW |
36 | static bool tproxy_sk_is_transparent(struct sock *sk) |
37 | { | |
38 | if (sk->sk_state != TCP_TIME_WAIT) { | |
39 | if (inet_sk(sk)->transparent) | |
40 | return true; | |
41 | sock_put(sk); | |
42 | } else { | |
43 | if (inet_twsk(sk)->tw_transparent) | |
44 | return true; | |
45 | inet_twsk_put(inet_twsk(sk)); | |
46 | } | |
47 | return false; | |
48 | } | |
49 | ||
cc6eb433 BS |
50 | static inline __be32 |
51 | tproxy_laddr4(struct sk_buff *skb, __be32 user_laddr, __be32 daddr) | |
52 | { | |
53 | struct in_device *indev; | |
54 | __be32 laddr; | |
55 | ||
56 | if (user_laddr) | |
57 | return user_laddr; | |
58 | ||
59 | laddr = 0; | |
60 | rcu_read_lock(); | |
61 | indev = __in_dev_get_rcu(skb->dev); | |
62 | for_primary_ifa(indev) { | |
63 | laddr = ifa->ifa_local; | |
64 | break; | |
65 | } endfor_ifa(indev); | |
66 | rcu_read_unlock(); | |
67 | ||
68 | return laddr ? laddr : daddr; | |
69 | } | |
e8439270 | 70 | |
106e4c26 | 71 | /** |
2c53040f | 72 | * tproxy_handle_time_wait4 - handle IPv4 TCP TIME_WAIT reopen redirections |
106e4c26 | 73 | * @skb: The skb being processed. |
6ad78893 BS |
74 | * @laddr: IPv4 address to redirect to or zero. |
75 | * @lport: TCP port to redirect to or zero. | |
106e4c26 BS |
76 | * @sk: The TIME_WAIT TCP socket found by the lookup. |
77 | * | |
78 | * We have to handle SYN packets arriving to TIME_WAIT sockets | |
79 | * differently: instead of reopening the connection we should rather | |
80 | * redirect the new connection to the proxy if there's a listener | |
81 | * socket present. | |
82 | * | |
6ad78893 | 83 | * tproxy_handle_time_wait4() consumes the socket reference passed in. |
106e4c26 BS |
84 | * |
85 | * Returns the listener socket if there's one, the TIME_WAIT socket if | |
86 | * no such listener is found, or NULL if the TCP header is incomplete. | |
87 | */ | |
88 | static struct sock * | |
6ad78893 BS |
89 | tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport, |
90 | struct sock *sk) | |
106e4c26 BS |
91 | { |
92 | const struct iphdr *iph = ip_hdr(skb); | |
106e4c26 BS |
93 | struct tcphdr _hdr, *hp; |
94 | ||
95 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
96 | if (hp == NULL) { | |
97 | inet_twsk_put(inet_twsk(sk)); | |
98 | return NULL; | |
99 | } | |
100 | ||
101 | if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { | |
102 | /* SYN to a TIME_WAIT socket, we'd rather redirect it | |
103 | * to a listener socket if there's one */ | |
104 | struct sock *sk2; | |
105 | ||
106 | sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, | |
6ad78893 BS |
107 | iph->saddr, laddr ? laddr : iph->daddr, |
108 | hp->source, lport ? lport : hp->dest, | |
109 | skb->dev, NFT_LOOKUP_LISTENER); | |
110 | if (sk2) { | |
111 | inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); | |
112 | inet_twsk_put(inet_twsk(sk)); | |
113 | sk = sk2; | |
114 | } | |
115 | } | |
116 | ||
117 | return sk; | |
118 | } | |
119 | ||
e8439270 | 120 | static unsigned int |
6ad78893 BS |
121 | tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport, |
122 | u_int32_t mark_mask, u_int32_t mark_value) | |
e8439270 KK |
123 | { |
124 | const struct iphdr *iph = ip_hdr(skb); | |
e8439270 KK |
125 | struct udphdr _hdr, *hp; |
126 | struct sock *sk; | |
127 | ||
128 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
129 | if (hp == NULL) | |
130 | return NF_DROP; | |
131 | ||
6ad78893 BS |
132 | /* check if there's an ongoing connection on the packet |
133 | * addresses, this happens if the redirect already happened | |
134 | * and the current packet belongs to an already established | |
135 | * connection */ | |
e8439270 | 136 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
106e4c26 BS |
137 | iph->saddr, iph->daddr, |
138 | hp->source, hp->dest, | |
6ad78893 | 139 | skb->dev, NFT_LOOKUP_ESTABLISHED); |
106e4c26 | 140 | |
cc6eb433 BS |
141 | laddr = tproxy_laddr4(skb, laddr, iph->daddr); |
142 | if (!lport) | |
143 | lport = hp->dest; | |
144 | ||
106e4c26 BS |
145 | /* UDP has no TCP_TIME_WAIT state, so we never enter here */ |
146 | if (sk && sk->sk_state == TCP_TIME_WAIT) | |
6ad78893 BS |
147 | /* reopening a TIME_WAIT connection needs special handling */ |
148 | sk = tproxy_handle_time_wait4(skb, laddr, lport, sk); | |
106e4c26 | 149 | else if (!sk) |
6ad78893 BS |
150 | /* no, there's no established connection, check if |
151 | * there's a listener on the redirected addr/port */ | |
106e4c26 | 152 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
cc6eb433 BS |
153 | iph->saddr, laddr, |
154 | hp->source, lport, | |
6ad78893 BS |
155 | skb->dev, NFT_LOOKUP_LISTENER); |
156 | ||
157 | /* NOTE: assign_sock consumes our sk reference */ | |
d503b30b | 158 | if (sk && tproxy_sk_is_transparent(sk)) { |
6ad78893 BS |
159 | /* This should be in a separate target, but we don't do multiple |
160 | targets on the same rule yet */ | |
161 | skb->mark = (skb->mark & ~mark_mask) ^ mark_value; | |
162 | ||
163 | pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", | |
164 | iph->protocol, &iph->daddr, ntohs(hp->dest), | |
165 | &laddr, ntohs(lport), skb->mark); | |
d503b30b FW |
166 | |
167 | nf_tproxy_assign_sock(skb, sk); | |
6ad78893 BS |
168 | return NF_ACCEPT; |
169 | } | |
170 | ||
cc6eb433 BS |
171 | pr_debug("no socket, dropping: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", |
172 | iph->protocol, &iph->saddr, ntohs(hp->source), | |
173 | &iph->daddr, ntohs(hp->dest), skb->mark); | |
6ad78893 BS |
174 | return NF_DROP; |
175 | } | |
176 | ||
177 | static unsigned int | |
178 | tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) | |
179 | { | |
180 | const struct xt_tproxy_target_info *tgi = par->targinfo; | |
181 | ||
182 | return tproxy_tg4(skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value); | |
183 | } | |
184 | ||
185 | static unsigned int | |
186 | tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) | |
187 | { | |
188 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
189 | ||
190 | return tproxy_tg4(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value); | |
191 | } | |
192 | ||
f6318e55 | 193 | #ifdef XT_TPROXY_HAVE_IPV6 |
cc6eb433 BS |
194 | |
195 | static inline const struct in6_addr * | |
196 | tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr, | |
197 | const struct in6_addr *daddr) | |
198 | { | |
199 | struct inet6_dev *indev; | |
200 | struct inet6_ifaddr *ifa; | |
201 | struct in6_addr *laddr; | |
202 | ||
203 | if (!ipv6_addr_any(user_laddr)) | |
204 | return user_laddr; | |
205 | laddr = NULL; | |
206 | ||
207 | rcu_read_lock(); | |
208 | indev = __in6_dev_get(skb->dev); | |
209 | if (indev) | |
210 | list_for_each_entry(ifa, &indev->addr_list, if_list) { | |
211 | if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED)) | |
212 | continue; | |
213 | ||
214 | laddr = &ifa->addr; | |
215 | break; | |
216 | } | |
217 | rcu_read_unlock(); | |
218 | ||
219 | return laddr ? laddr : daddr; | |
220 | } | |
221 | ||
222 | /** | |
2c53040f | 223 | * tproxy_handle_time_wait6 - handle IPv6 TCP TIME_WAIT reopen redirections |
cc6eb433 BS |
224 | * @skb: The skb being processed. |
225 | * @tproto: Transport protocol. | |
226 | * @thoff: Transport protocol header offset. | |
227 | * @par: Iptables target parameters. | |
228 | * @sk: The TIME_WAIT TCP socket found by the lookup. | |
229 | * | |
230 | * We have to handle SYN packets arriving to TIME_WAIT sockets | |
231 | * differently: instead of reopening the connection we should rather | |
232 | * redirect the new connection to the proxy if there's a listener | |
233 | * socket present. | |
234 | * | |
235 | * tproxy_handle_time_wait6() consumes the socket reference passed in. | |
236 | * | |
237 | * Returns the listener socket if there's one, the TIME_WAIT socket if | |
238 | * no such listener is found, or NULL if the TCP header is incomplete. | |
239 | */ | |
240 | static struct sock * | |
241 | tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff, | |
242 | const struct xt_action_param *par, | |
243 | struct sock *sk) | |
244 | { | |
245 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
246 | struct tcphdr _hdr, *hp; | |
247 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
248 | ||
249 | hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); | |
250 | if (hp == NULL) { | |
251 | inet_twsk_put(inet_twsk(sk)); | |
252 | return NULL; | |
253 | } | |
254 | ||
255 | if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { | |
256 | /* SYN to a TIME_WAIT socket, we'd rather redirect it | |
257 | * to a listener socket if there's one */ | |
258 | struct sock *sk2; | |
259 | ||
260 | sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
261 | &iph->saddr, | |
262 | tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr), | |
263 | hp->source, | |
264 | tgi->lport ? tgi->lport : hp->dest, | |
265 | skb->dev, NFT_LOOKUP_LISTENER); | |
266 | if (sk2) { | |
267 | inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); | |
268 | inet_twsk_put(inet_twsk(sk)); | |
269 | sk = sk2; | |
270 | } | |
271 | } | |
272 | ||
273 | return sk; | |
274 | } | |
275 | ||
6ad78893 BS |
276 | static unsigned int |
277 | tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) | |
278 | { | |
279 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
280 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
281 | struct udphdr _hdr, *hp; | |
282 | struct sock *sk; | |
cc6eb433 BS |
283 | const struct in6_addr *laddr; |
284 | __be16 lport; | |
84018f55 | 285 | int thoff = 0; |
6ad78893 BS |
286 | int tproto; |
287 | ||
84018f55 | 288 | tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL); |
6ad78893 BS |
289 | if (tproto < 0) { |
290 | pr_debug("unable to find transport header in IPv6 packet, dropping\n"); | |
291 | return NF_DROP; | |
292 | } | |
293 | ||
294 | hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); | |
295 | if (hp == NULL) { | |
296 | pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); | |
297 | return NF_DROP; | |
298 | } | |
299 | ||
300 | /* check if there's an ongoing connection on the packet | |
301 | * addresses, this happens if the redirect already happened | |
302 | * and the current packet belongs to an already established | |
303 | * connection */ | |
304 | sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
305 | &iph->saddr, &iph->daddr, | |
306 | hp->source, hp->dest, | |
307 | par->in, NFT_LOOKUP_ESTABLISHED); | |
308 | ||
cc6eb433 BS |
309 | laddr = tproxy_laddr6(skb, &tgi->laddr.in6, &iph->daddr); |
310 | lport = tgi->lport ? tgi->lport : hp->dest; | |
311 | ||
6ad78893 BS |
312 | /* UDP has no TCP_TIME_WAIT state, so we never enter here */ |
313 | if (sk && sk->sk_state == TCP_TIME_WAIT) | |
314 | /* reopening a TIME_WAIT connection needs special handling */ | |
315 | sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk); | |
316 | else if (!sk) | |
317 | /* no there's no established connection, check if | |
318 | * there's a listener on the redirected addr/port */ | |
319 | sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
cc6eb433 BS |
320 | &iph->saddr, laddr, |
321 | hp->source, lport, | |
106e4c26 | 322 | par->in, NFT_LOOKUP_LISTENER); |
e8439270 KK |
323 | |
324 | /* NOTE: assign_sock consumes our sk reference */ | |
d503b30b | 325 | if (sk && tproxy_sk_is_transparent(sk)) { |
e8439270 KK |
326 | /* This should be in a separate target, but we don't do multiple |
327 | targets on the same rule yet */ | |
328 | skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; | |
329 | ||
6ad78893 | 330 | pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", |
cc6eb433 BS |
331 | tproto, &iph->saddr, ntohs(hp->source), |
332 | laddr, ntohs(lport), skb->mark); | |
d503b30b FW |
333 | |
334 | nf_tproxy_assign_sock(skb, sk); | |
e8439270 KK |
335 | return NF_ACCEPT; |
336 | } | |
337 | ||
6ad78893 | 338 | pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", |
cc6eb433 BS |
339 | tproto, &iph->saddr, ntohs(hp->source), |
340 | &iph->daddr, ntohs(hp->dest), skb->mark); | |
341 | ||
e8439270 KK |
342 | return NF_DROP; |
343 | } | |
344 | ||
6ad78893 BS |
345 | static int tproxy_tg6_check(const struct xt_tgchk_param *par) |
346 | { | |
347 | const struct ip6t_ip6 *i = par->entryinfo; | |
348 | ||
349 | if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) | |
350 | && !(i->flags & IP6T_INV_PROTO)) | |
351 | return 0; | |
352 | ||
353 | pr_info("Can be used only in combination with " | |
354 | "either -p tcp or -p udp\n"); | |
355 | return -EINVAL; | |
356 | } | |
357 | #endif | |
358 | ||
359 | static int tproxy_tg4_check(const struct xt_tgchk_param *par) | |
e8439270 | 360 | { |
af5d6dc2 | 361 | const struct ipt_ip *i = par->entryinfo; |
e8439270 KK |
362 | |
363 | if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) | |
364 | && !(i->invflags & IPT_INV_PROTO)) | |
d6b00a53 | 365 | return 0; |
e8439270 | 366 | |
ff67e4e4 | 367 | pr_info("Can be used only in combination with " |
e8439270 | 368 | "either -p tcp or -p udp\n"); |
d6b00a53 | 369 | return -EINVAL; |
e8439270 KK |
370 | } |
371 | ||
6ad78893 BS |
372 | static struct xt_target tproxy_tg_reg[] __read_mostly = { |
373 | { | |
374 | .name = "TPROXY", | |
375 | .family = NFPROTO_IPV4, | |
376 | .table = "mangle", | |
377 | .target = tproxy_tg4_v0, | |
378 | .revision = 0, | |
379 | .targetsize = sizeof(struct xt_tproxy_target_info), | |
380 | .checkentry = tproxy_tg4_check, | |
381 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
382 | .me = THIS_MODULE, | |
383 | }, | |
384 | { | |
385 | .name = "TPROXY", | |
386 | .family = NFPROTO_IPV4, | |
387 | .table = "mangle", | |
388 | .target = tproxy_tg4_v1, | |
389 | .revision = 1, | |
390 | .targetsize = sizeof(struct xt_tproxy_target_info_v1), | |
391 | .checkentry = tproxy_tg4_check, | |
392 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
393 | .me = THIS_MODULE, | |
394 | }, | |
f6318e55 | 395 | #ifdef XT_TPROXY_HAVE_IPV6 |
6ad78893 BS |
396 | { |
397 | .name = "TPROXY", | |
398 | .family = NFPROTO_IPV6, | |
399 | .table = "mangle", | |
400 | .target = tproxy_tg6_v1, | |
401 | .revision = 1, | |
402 | .targetsize = sizeof(struct xt_tproxy_target_info_v1), | |
403 | .checkentry = tproxy_tg6_check, | |
404 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
405 | .me = THIS_MODULE, | |
406 | }, | |
407 | #endif | |
408 | ||
e8439270 KK |
409 | }; |
410 | ||
411 | static int __init tproxy_tg_init(void) | |
412 | { | |
413 | nf_defrag_ipv4_enable(); | |
f6318e55 | 414 | #ifdef XT_TPROXY_HAVE_IPV6 |
6ad78893 BS |
415 | nf_defrag_ipv6_enable(); |
416 | #endif | |
417 | ||
418 | return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); | |
e8439270 KK |
419 | } |
420 | ||
421 | static void __exit tproxy_tg_exit(void) | |
422 | { | |
6ad78893 | 423 | xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); |
e8439270 KK |
424 | } |
425 | ||
426 | module_init(tproxy_tg_init); | |
427 | module_exit(tproxy_tg_exit); | |
428 | MODULE_LICENSE("GPL"); | |
6ad78893 | 429 | MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); |
e8439270 KK |
430 | MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); |
431 | MODULE_ALIAS("ipt_TPROXY"); | |
6ad78893 | 432 | MODULE_ALIAS("ip6t_TPROXY"); |