Linux kernel mirror (for testing)
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linux
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/nf_tproxy_core.h>
23#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
24
25#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
26#define XT_SOCKET_HAVE_IPV6 1
27#include <linux/netfilter_ipv6/ip6_tables.h>
28#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
29#endif
30
31#include <linux/netfilter/xt_socket.h>
32
33#if IS_ENABLED(CONFIG_NF_CONNTRACK)
34#define XT_SOCKET_HAVE_CONNTRACK 1
35#include <net/netfilter/nf_conntrack.h>
36#endif
37
38static void
39xt_socket_put_sk(struct sock *sk)
40{
41 if (sk->sk_state == TCP_TIME_WAIT)
42 inet_twsk_put(inet_twsk(sk));
43 else
44 sock_put(sk);
45}
46
47static int
48extract_icmp4_fields(const struct sk_buff *skb,
49 u8 *protocol,
50 __be32 *raddr,
51 __be32 *laddr,
52 __be16 *rport,
53 __be16 *lport)
54{
55 unsigned int outside_hdrlen = ip_hdrlen(skb);
56 struct iphdr *inside_iph, _inside_iph;
57 struct icmphdr *icmph, _icmph;
58 __be16 *ports, _ports[2];
59
60 icmph = skb_header_pointer(skb, outside_hdrlen,
61 sizeof(_icmph), &_icmph);
62 if (icmph == NULL)
63 return 1;
64
65 switch (icmph->type) {
66 case ICMP_DEST_UNREACH:
67 case ICMP_SOURCE_QUENCH:
68 case ICMP_REDIRECT:
69 case ICMP_TIME_EXCEEDED:
70 case ICMP_PARAMETERPROB:
71 break;
72 default:
73 return 1;
74 }
75
76 inside_iph = skb_header_pointer(skb, outside_hdrlen +
77 sizeof(struct icmphdr),
78 sizeof(_inside_iph), &_inside_iph);
79 if (inside_iph == NULL)
80 return 1;
81
82 if (inside_iph->protocol != IPPROTO_TCP &&
83 inside_iph->protocol != IPPROTO_UDP)
84 return 1;
85
86 ports = skb_header_pointer(skb, outside_hdrlen +
87 sizeof(struct icmphdr) +
88 (inside_iph->ihl << 2),
89 sizeof(_ports), &_ports);
90 if (ports == NULL)
91 return 1;
92
93 /* the inside IP packet is the one quoted from our side, thus
94 * its saddr is the local address */
95 *protocol = inside_iph->protocol;
96 *laddr = inside_iph->saddr;
97 *lport = ports[0];
98 *raddr = inside_iph->daddr;
99 *rport = ports[1];
100
101 return 0;
102}
103
104static bool
105socket_match(const struct sk_buff *skb, struct xt_action_param *par,
106 const struct xt_socket_mtinfo1 *info)
107{
108 const struct iphdr *iph = ip_hdr(skb);
109 struct udphdr _hdr, *hp = NULL;
110 struct sock *sk;
111 __be32 daddr, saddr;
112 __be16 dport, sport;
113 u8 protocol;
114#ifdef XT_SOCKET_HAVE_CONNTRACK
115 struct nf_conn const *ct;
116 enum ip_conntrack_info ctinfo;
117#endif
118
119 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
120 hp = skb_header_pointer(skb, ip_hdrlen(skb),
121 sizeof(_hdr), &_hdr);
122 if (hp == NULL)
123 return false;
124
125 protocol = iph->protocol;
126 saddr = iph->saddr;
127 sport = hp->source;
128 daddr = iph->daddr;
129 dport = hp->dest;
130
131 } else if (iph->protocol == IPPROTO_ICMP) {
132 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
133 &sport, &dport))
134 return false;
135 } else {
136 return false;
137 }
138
139#ifdef XT_SOCKET_HAVE_CONNTRACK
140 /* Do the lookup with the original socket address in case this is a
141 * reply packet of an established SNAT-ted connection. */
142
143 ct = nf_ct_get(skb, &ctinfo);
144 if (ct && !nf_ct_is_untracked(ct) &&
145 ((iph->protocol != IPPROTO_ICMP &&
146 ctinfo == IP_CT_ESTABLISHED_REPLY) ||
147 (iph->protocol == IPPROTO_ICMP &&
148 ctinfo == IP_CT_RELATED_REPLY)) &&
149 (ct->status & IPS_SRC_NAT_DONE)) {
150
151 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
152 dport = (iph->protocol == IPPROTO_TCP) ?
153 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
154 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
155 }
156#endif
157
158 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
159 saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
160 if (sk != NULL) {
161 bool wildcard;
162 bool transparent = true;
163
164 /* Ignore sockets listening on INADDR_ANY */
165 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
166 inet_sk(sk)->inet_rcv_saddr == 0);
167
168 /* Ignore non-transparent sockets,
169 if XT_SOCKET_TRANSPARENT is used */
170 if (info && info->flags & XT_SOCKET_TRANSPARENT)
171 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
172 inet_sk(sk)->transparent) ||
173 (sk->sk_state == TCP_TIME_WAIT &&
174 inet_twsk(sk)->tw_transparent));
175
176 xt_socket_put_sk(sk);
177
178 if (wildcard || !transparent)
179 sk = NULL;
180 }
181
182 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
183 protocol, &saddr, ntohs(sport),
184 &daddr, ntohs(dport),
185 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
186
187 return (sk != NULL);
188}
189
190static bool
191socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
192{
193 return socket_match(skb, par, NULL);
194}
195
196static bool
197socket_mt4_v1(const struct sk_buff *skb, struct xt_action_param *par)
198{
199 return socket_match(skb, par, par->matchinfo);
200}
201
202#ifdef XT_SOCKET_HAVE_IPV6
203
204static int
205extract_icmp6_fields(const struct sk_buff *skb,
206 unsigned int outside_hdrlen,
207 int *protocol,
208 struct in6_addr **raddr,
209 struct in6_addr **laddr,
210 __be16 *rport,
211 __be16 *lport)
212{
213 struct ipv6hdr *inside_iph, _inside_iph;
214 struct icmp6hdr *icmph, _icmph;
215 __be16 *ports, _ports[2];
216 u8 inside_nexthdr;
217 __be16 inside_fragoff;
218 int inside_hdrlen;
219
220 icmph = skb_header_pointer(skb, outside_hdrlen,
221 sizeof(_icmph), &_icmph);
222 if (icmph == NULL)
223 return 1;
224
225 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
226 return 1;
227
228 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
229 if (inside_iph == NULL)
230 return 1;
231 inside_nexthdr = inside_iph->nexthdr;
232
233 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
234 &inside_nexthdr, &inside_fragoff);
235 if (inside_hdrlen < 0)
236 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
237
238 if (inside_nexthdr != IPPROTO_TCP &&
239 inside_nexthdr != IPPROTO_UDP)
240 return 1;
241
242 ports = skb_header_pointer(skb, inside_hdrlen,
243 sizeof(_ports), &_ports);
244 if (ports == NULL)
245 return 1;
246
247 /* the inside IP packet is the one quoted from our side, thus
248 * its saddr is the local address */
249 *protocol = inside_nexthdr;
250 *laddr = &inside_iph->saddr;
251 *lport = ports[0];
252 *raddr = &inside_iph->daddr;
253 *rport = ports[1];
254
255 return 0;
256}
257
258static bool
259socket_mt6_v1(const struct sk_buff *skb, struct xt_action_param *par)
260{
261 struct ipv6hdr *iph = ipv6_hdr(skb);
262 struct udphdr _hdr, *hp = NULL;
263 struct sock *sk;
264 struct in6_addr *daddr, *saddr;
265 __be16 dport, sport;
266 int thoff, tproto;
267 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
268
269 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL);
270 if (tproto < 0) {
271 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
272 return NF_DROP;
273 }
274
275 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
276 hp = skb_header_pointer(skb, thoff,
277 sizeof(_hdr), &_hdr);
278 if (hp == NULL)
279 return false;
280
281 saddr = &iph->saddr;
282 sport = hp->source;
283 daddr = &iph->daddr;
284 dport = hp->dest;
285
286 } else if (tproto == IPPROTO_ICMPV6) {
287 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
288 &sport, &dport))
289 return false;
290 } else {
291 return false;
292 }
293
294 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
295 saddr, daddr, sport, dport, par->in, NFT_LOOKUP_ANY);
296 if (sk != NULL) {
297 bool wildcard;
298 bool transparent = true;
299
300 /* Ignore sockets listening on INADDR_ANY */
301 wildcard = (sk->sk_state != TCP_TIME_WAIT &&
302 ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
303
304 /* Ignore non-transparent sockets,
305 if XT_SOCKET_TRANSPARENT is used */
306 if (info && info->flags & XT_SOCKET_TRANSPARENT)
307 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
308 inet_sk(sk)->transparent) ||
309 (sk->sk_state == TCP_TIME_WAIT &&
310 inet_twsk(sk)->tw_transparent));
311
312 xt_socket_put_sk(sk);
313
314 if (wildcard || !transparent)
315 sk = NULL;
316 }
317
318 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
319 "(orig %pI6:%hu) sock %p\n",
320 tproto, saddr, ntohs(sport),
321 daddr, ntohs(dport),
322 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
323
324 return (sk != NULL);
325}
326#endif
327
328static struct xt_match socket_mt_reg[] __read_mostly = {
329 {
330 .name = "socket",
331 .revision = 0,
332 .family = NFPROTO_IPV4,
333 .match = socket_mt4_v0,
334 .hooks = (1 << NF_INET_PRE_ROUTING) |
335 (1 << NF_INET_LOCAL_IN),
336 .me = THIS_MODULE,
337 },
338 {
339 .name = "socket",
340 .revision = 1,
341 .family = NFPROTO_IPV4,
342 .match = socket_mt4_v1,
343 .matchsize = sizeof(struct xt_socket_mtinfo1),
344 .hooks = (1 << NF_INET_PRE_ROUTING) |
345 (1 << NF_INET_LOCAL_IN),
346 .me = THIS_MODULE,
347 },
348#ifdef XT_SOCKET_HAVE_IPV6
349 {
350 .name = "socket",
351 .revision = 1,
352 .family = NFPROTO_IPV6,
353 .match = socket_mt6_v1,
354 .matchsize = sizeof(struct xt_socket_mtinfo1),
355 .hooks = (1 << NF_INET_PRE_ROUTING) |
356 (1 << NF_INET_LOCAL_IN),
357 .me = THIS_MODULE,
358 },
359#endif
360};
361
362static int __init socket_mt_init(void)
363{
364 nf_defrag_ipv4_enable();
365#ifdef XT_SOCKET_HAVE_IPV6
366 nf_defrag_ipv6_enable();
367#endif
368
369 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
370}
371
372static void __exit socket_mt_exit(void)
373{
374 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
375}
376
377module_init(socket_mt_init);
378module_exit(socket_mt_exit);
379
380MODULE_LICENSE("GPL");
381MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
382MODULE_DESCRIPTION("x_tables socket match module");
383MODULE_ALIAS("ipt_socket");
384MODULE_ALIAS("ip6t_socket");