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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> | |
19 | ||
20 | #include <linux/netfilter/x_tables.h> | |
21 | #include <linux/netfilter_ipv4/ip_tables.h> | |
6ad78893 | 22 | #include <linux/netfilter_ipv6/ip6_tables.h> |
e8439270 KK |
23 | #include <linux/netfilter/xt_TPROXY.h> |
24 | ||
25 | #include <net/netfilter/ipv4/nf_defrag_ipv4.h> | |
6ad78893 | 26 | #include <net/netfilter/ipv6/nf_defrag_ipv6.h> |
e8439270 KK |
27 | #include <net/netfilter/nf_tproxy_core.h> |
28 | ||
106e4c26 | 29 | /** |
6ad78893 | 30 | * tproxy_handle_time_wait4() - handle IPv4 TCP TIME_WAIT reopen redirections |
106e4c26 | 31 | * @skb: The skb being processed. |
6ad78893 BS |
32 | * @laddr: IPv4 address to redirect to or zero. |
33 | * @lport: TCP port to redirect to or zero. | |
106e4c26 BS |
34 | * @sk: The TIME_WAIT TCP socket found by the lookup. |
35 | * | |
36 | * We have to handle SYN packets arriving to TIME_WAIT sockets | |
37 | * differently: instead of reopening the connection we should rather | |
38 | * redirect the new connection to the proxy if there's a listener | |
39 | * socket present. | |
40 | * | |
6ad78893 | 41 | * tproxy_handle_time_wait4() consumes the socket reference passed in. |
106e4c26 BS |
42 | * |
43 | * Returns the listener socket if there's one, the TIME_WAIT socket if | |
44 | * no such listener is found, or NULL if the TCP header is incomplete. | |
45 | */ | |
46 | static struct sock * | |
6ad78893 BS |
47 | tproxy_handle_time_wait4(struct sk_buff *skb, __be32 laddr, __be16 lport, |
48 | struct sock *sk) | |
106e4c26 BS |
49 | { |
50 | const struct iphdr *iph = ip_hdr(skb); | |
106e4c26 BS |
51 | struct tcphdr _hdr, *hp; |
52 | ||
53 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
54 | if (hp == NULL) { | |
55 | inet_twsk_put(inet_twsk(sk)); | |
56 | return NULL; | |
57 | } | |
58 | ||
59 | if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { | |
60 | /* SYN to a TIME_WAIT socket, we'd rather redirect it | |
61 | * to a listener socket if there's one */ | |
62 | struct sock *sk2; | |
63 | ||
64 | sk2 = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, | |
6ad78893 BS |
65 | iph->saddr, laddr ? laddr : iph->daddr, |
66 | hp->source, lport ? lport : hp->dest, | |
67 | skb->dev, NFT_LOOKUP_LISTENER); | |
68 | if (sk2) { | |
69 | inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); | |
70 | inet_twsk_put(inet_twsk(sk)); | |
71 | sk = sk2; | |
72 | } | |
73 | } | |
74 | ||
75 | return sk; | |
76 | } | |
77 | ||
78 | /** | |
79 | * tproxy_handle_time_wait6() - handle IPv6 TCP TIME_WAIT reopen redirections | |
80 | * @skb: The skb being processed. | |
81 | * @tproto: Transport protocol. | |
82 | * @thoff: Transport protocol header offset. | |
83 | * @par: Iptables target parameters. | |
84 | * @sk: The TIME_WAIT TCP socket found by the lookup. | |
85 | * | |
86 | * We have to handle SYN packets arriving to TIME_WAIT sockets | |
87 | * differently: instead of reopening the connection we should rather | |
88 | * redirect the new connection to the proxy if there's a listener | |
89 | * socket present. | |
90 | * | |
91 | * tproxy_handle_time_wait6() consumes the socket reference passed in. | |
92 | * | |
93 | * Returns the listener socket if there's one, the TIME_WAIT socket if | |
94 | * no such listener is found, or NULL if the TCP header is incomplete. | |
95 | */ | |
96 | static struct sock * | |
97 | tproxy_handle_time_wait6(struct sk_buff *skb, int tproto, int thoff, | |
98 | const struct xt_action_param *par, | |
99 | struct sock *sk) | |
100 | { | |
101 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
102 | struct tcphdr _hdr, *hp; | |
103 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
104 | ||
105 | hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); | |
106 | if (hp == NULL) { | |
107 | inet_twsk_put(inet_twsk(sk)); | |
108 | return NULL; | |
109 | } | |
110 | ||
111 | if (hp->syn && !hp->rst && !hp->ack && !hp->fin) { | |
112 | /* SYN to a TIME_WAIT socket, we'd rather redirect it | |
113 | * to a listener socket if there's one */ | |
114 | struct sock *sk2; | |
115 | ||
116 | sk2 = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
117 | &iph->saddr, | |
118 | !ipv6_addr_any(&tgi->laddr.in6) ? &tgi->laddr.in6 : &iph->daddr, | |
119 | hp->source, | |
120 | tgi->lport ? tgi->lport : hp->dest, | |
121 | skb->dev, NFT_LOOKUP_LISTENER); | |
106e4c26 | 122 | if (sk2) { |
106e4c26 BS |
123 | inet_twsk_deschedule(inet_twsk(sk), &tcp_death_row); |
124 | inet_twsk_put(inet_twsk(sk)); | |
125 | sk = sk2; | |
126 | } | |
127 | } | |
128 | ||
129 | return sk; | |
130 | } | |
131 | ||
e8439270 | 132 | static unsigned int |
6ad78893 BS |
133 | tproxy_tg4(struct sk_buff *skb, __be32 laddr, __be16 lport, |
134 | u_int32_t mark_mask, u_int32_t mark_value) | |
e8439270 KK |
135 | { |
136 | const struct iphdr *iph = ip_hdr(skb); | |
e8439270 KK |
137 | struct udphdr _hdr, *hp; |
138 | struct sock *sk; | |
139 | ||
140 | hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr); | |
141 | if (hp == NULL) | |
142 | return NF_DROP; | |
143 | ||
6ad78893 BS |
144 | /* check if there's an ongoing connection on the packet |
145 | * addresses, this happens if the redirect already happened | |
146 | * and the current packet belongs to an already established | |
147 | * connection */ | |
e8439270 | 148 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
106e4c26 BS |
149 | iph->saddr, iph->daddr, |
150 | hp->source, hp->dest, | |
6ad78893 | 151 | skb->dev, NFT_LOOKUP_ESTABLISHED); |
106e4c26 BS |
152 | |
153 | /* UDP has no TCP_TIME_WAIT state, so we never enter here */ | |
154 | if (sk && sk->sk_state == TCP_TIME_WAIT) | |
6ad78893 BS |
155 | /* reopening a TIME_WAIT connection needs special handling */ |
156 | sk = tproxy_handle_time_wait4(skb, laddr, lport, sk); | |
106e4c26 | 157 | else if (!sk) |
6ad78893 BS |
158 | /* no, there's no established connection, check if |
159 | * there's a listener on the redirected addr/port */ | |
106e4c26 | 160 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol, |
6ad78893 BS |
161 | iph->saddr, laddr ? laddr : iph->daddr, |
162 | hp->source, lport ? lport : hp->dest, | |
163 | skb->dev, NFT_LOOKUP_LISTENER); | |
164 | ||
165 | /* NOTE: assign_sock consumes our sk reference */ | |
166 | if (sk && nf_tproxy_assign_sock(skb, sk)) { | |
167 | /* This should be in a separate target, but we don't do multiple | |
168 | targets on the same rule yet */ | |
169 | skb->mark = (skb->mark & ~mark_mask) ^ mark_value; | |
170 | ||
171 | pr_debug("redirecting: proto %hhu %pI4:%hu -> %pI4:%hu, mark: %x\n", | |
172 | iph->protocol, &iph->daddr, ntohs(hp->dest), | |
173 | &laddr, ntohs(lport), skb->mark); | |
174 | return NF_ACCEPT; | |
175 | } | |
176 | ||
177 | pr_debug("no socket, dropping: proto %hhu %08x:%hu -> %08x:%hu, mark: %x\n", | |
178 | iph->protocol, ntohl(iph->daddr), ntohs(hp->dest), | |
179 | ntohl(laddr), ntohs(lport), skb->mark); | |
180 | return NF_DROP; | |
181 | } | |
182 | ||
183 | static unsigned int | |
184 | tproxy_tg4_v0(struct sk_buff *skb, const struct xt_action_param *par) | |
185 | { | |
186 | const struct xt_tproxy_target_info *tgi = par->targinfo; | |
187 | ||
188 | return tproxy_tg4(skb, tgi->laddr, tgi->lport, tgi->mark_mask, tgi->mark_value); | |
189 | } | |
190 | ||
191 | static unsigned int | |
192 | tproxy_tg4_v1(struct sk_buff *skb, const struct xt_action_param *par) | |
193 | { | |
194 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
195 | ||
196 | return tproxy_tg4(skb, tgi->laddr.ip, tgi->lport, tgi->mark_mask, tgi->mark_value); | |
197 | } | |
198 | ||
199 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
200 | static unsigned int | |
201 | tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) | |
202 | { | |
203 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
204 | const struct xt_tproxy_target_info_v1 *tgi = par->targinfo; | |
205 | struct udphdr _hdr, *hp; | |
206 | struct sock *sk; | |
207 | int thoff; | |
208 | int tproto; | |
209 | ||
210 | tproto = ipv6_find_hdr(skb, &thoff, -1, NULL); | |
211 | if (tproto < 0) { | |
212 | pr_debug("unable to find transport header in IPv6 packet, dropping\n"); | |
213 | return NF_DROP; | |
214 | } | |
215 | ||
216 | hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr); | |
217 | if (hp == NULL) { | |
218 | pr_debug("unable to grab transport header contents in IPv6 packet, dropping\n"); | |
219 | return NF_DROP; | |
220 | } | |
221 | ||
222 | /* check if there's an ongoing connection on the packet | |
223 | * addresses, this happens if the redirect already happened | |
224 | * and the current packet belongs to an already established | |
225 | * connection */ | |
226 | sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
227 | &iph->saddr, &iph->daddr, | |
228 | hp->source, hp->dest, | |
229 | par->in, NFT_LOOKUP_ESTABLISHED); | |
230 | ||
231 | /* UDP has no TCP_TIME_WAIT state, so we never enter here */ | |
232 | if (sk && sk->sk_state == TCP_TIME_WAIT) | |
233 | /* reopening a TIME_WAIT connection needs special handling */ | |
234 | sk = tproxy_handle_time_wait6(skb, tproto, thoff, par, sk); | |
235 | else if (!sk) | |
236 | /* no there's no established connection, check if | |
237 | * there's a listener on the redirected addr/port */ | |
238 | sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto, | |
239 | &iph->saddr, | |
240 | !ipv6_addr_any(&tgi->laddr.in6) ? &tgi->laddr.in6 : &iph->daddr, | |
241 | hp->source, | |
242 | tgi->lport ? tgi->lport : hp->dest, | |
106e4c26 | 243 | par->in, NFT_LOOKUP_LISTENER); |
e8439270 KK |
244 | |
245 | /* NOTE: assign_sock consumes our sk reference */ | |
246 | if (sk && nf_tproxy_assign_sock(skb, sk)) { | |
247 | /* This should be in a separate target, but we don't do multiple | |
248 | targets on the same rule yet */ | |
249 | skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; | |
250 | ||
6ad78893 BS |
251 | pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", |
252 | tproto, &iph->saddr, ntohs(hp->dest), | |
253 | &tgi->laddr.in6, ntohs(tgi->lport), skb->mark); | |
e8439270 KK |
254 | return NF_ACCEPT; |
255 | } | |
256 | ||
6ad78893 BS |
257 | pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", |
258 | tproto, &iph->saddr, ntohs(hp->dest), | |
259 | &tgi->laddr.in6, ntohs(tgi->lport), skb->mark); | |
e8439270 KK |
260 | return NF_DROP; |
261 | } | |
262 | ||
6ad78893 BS |
263 | static int tproxy_tg6_check(const struct xt_tgchk_param *par) |
264 | { | |
265 | const struct ip6t_ip6 *i = par->entryinfo; | |
266 | ||
267 | if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) | |
268 | && !(i->flags & IP6T_INV_PROTO)) | |
269 | return 0; | |
270 | ||
271 | pr_info("Can be used only in combination with " | |
272 | "either -p tcp or -p udp\n"); | |
273 | return -EINVAL; | |
274 | } | |
275 | #endif | |
276 | ||
277 | static int tproxy_tg4_check(const struct xt_tgchk_param *par) | |
e8439270 | 278 | { |
af5d6dc2 | 279 | const struct ipt_ip *i = par->entryinfo; |
e8439270 KK |
280 | |
281 | if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP) | |
282 | && !(i->invflags & IPT_INV_PROTO)) | |
d6b00a53 | 283 | return 0; |
e8439270 | 284 | |
ff67e4e4 | 285 | pr_info("Can be used only in combination with " |
e8439270 | 286 | "either -p tcp or -p udp\n"); |
d6b00a53 | 287 | return -EINVAL; |
e8439270 KK |
288 | } |
289 | ||
6ad78893 BS |
290 | static struct xt_target tproxy_tg_reg[] __read_mostly = { |
291 | { | |
292 | .name = "TPROXY", | |
293 | .family = NFPROTO_IPV4, | |
294 | .table = "mangle", | |
295 | .target = tproxy_tg4_v0, | |
296 | .revision = 0, | |
297 | .targetsize = sizeof(struct xt_tproxy_target_info), | |
298 | .checkentry = tproxy_tg4_check, | |
299 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
300 | .me = THIS_MODULE, | |
301 | }, | |
302 | { | |
303 | .name = "TPROXY", | |
304 | .family = NFPROTO_IPV4, | |
305 | .table = "mangle", | |
306 | .target = tproxy_tg4_v1, | |
307 | .revision = 1, | |
308 | .targetsize = sizeof(struct xt_tproxy_target_info_v1), | |
309 | .checkentry = tproxy_tg4_check, | |
310 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
311 | .me = THIS_MODULE, | |
312 | }, | |
313 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) | |
314 | { | |
315 | .name = "TPROXY", | |
316 | .family = NFPROTO_IPV6, | |
317 | .table = "mangle", | |
318 | .target = tproxy_tg6_v1, | |
319 | .revision = 1, | |
320 | .targetsize = sizeof(struct xt_tproxy_target_info_v1), | |
321 | .checkentry = tproxy_tg6_check, | |
322 | .hooks = 1 << NF_INET_PRE_ROUTING, | |
323 | .me = THIS_MODULE, | |
324 | }, | |
325 | #endif | |
326 | ||
e8439270 KK |
327 | }; |
328 | ||
329 | static int __init tproxy_tg_init(void) | |
330 | { | |
331 | nf_defrag_ipv4_enable(); | |
6ad78893 BS |
332 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) |
333 | nf_defrag_ipv6_enable(); | |
334 | #endif | |
335 | ||
336 | return xt_register_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); | |
e8439270 KK |
337 | } |
338 | ||
339 | static void __exit tproxy_tg_exit(void) | |
340 | { | |
6ad78893 | 341 | xt_unregister_targets(tproxy_tg_reg, ARRAY_SIZE(tproxy_tg_reg)); |
e8439270 KK |
342 | } |
343 | ||
344 | module_init(tproxy_tg_init); | |
345 | module_exit(tproxy_tg_exit); | |
346 | MODULE_LICENSE("GPL"); | |
6ad78893 | 347 | MODULE_AUTHOR("Balazs Scheidler, Krisztian Kovacs"); |
e8439270 KK |
348 | MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module."); |
349 | MODULE_ALIAS("ipt_TPROXY"); | |
6ad78893 | 350 | MODULE_ALIAS("ip6t_TPROXY"); |