Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
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 = skb->sk;
111 __be32 uninitialized_var(daddr), uninitialized_var(saddr);
112 __be16 uninitialized_var(dport), uninitialized_var(sport);
113 u8 uninitialized_var(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 if (!sk)
159 sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
160 saddr, daddr, sport, dport,
161 par->in, NFT_LOOKUP_ANY);
162 if (sk) {
163 bool wildcard;
164 bool transparent = true;
165
166 /* Ignore sockets listening on INADDR_ANY,
167 * unless XT_SOCKET_NOWILDCARD is set
168 */
169 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
170 sk->sk_state != TCP_TIME_WAIT &&
171 inet_sk(sk)->inet_rcv_saddr == 0);
172
173 /* Ignore non-transparent sockets,
174 if XT_SOCKET_TRANSPARENT is used */
175 if (info->flags & XT_SOCKET_TRANSPARENT)
176 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
177 inet_sk(sk)->transparent) ||
178 (sk->sk_state == TCP_TIME_WAIT &&
179 inet_twsk(sk)->tw_transparent));
180
181 if (sk != skb->sk)
182 xt_socket_put_sk(sk);
183
184 if (wildcard || !transparent)
185 sk = NULL;
186 }
187
188 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
189 protocol, &saddr, ntohs(sport),
190 &daddr, ntohs(dport),
191 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
192
193 return (sk != NULL);
194}
195
196static bool
197socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
198{
199 static struct xt_socket_mtinfo1 xt_info_v0 = {
200 .flags = 0,
201 };
202
203 return socket_match(skb, par, &xt_info_v0);
204}
205
206static bool
207socket_mt4_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
208{
209 return socket_match(skb, par, par->matchinfo);
210}
211
212#ifdef XT_SOCKET_HAVE_IPV6
213
214static int
215extract_icmp6_fields(const struct sk_buff *skb,
216 unsigned int outside_hdrlen,
217 int *protocol,
218 struct in6_addr **raddr,
219 struct in6_addr **laddr,
220 __be16 *rport,
221 __be16 *lport)
222{
223 struct ipv6hdr *inside_iph, _inside_iph;
224 struct icmp6hdr *icmph, _icmph;
225 __be16 *ports, _ports[2];
226 u8 inside_nexthdr;
227 __be16 inside_fragoff;
228 int inside_hdrlen;
229
230 icmph = skb_header_pointer(skb, outside_hdrlen,
231 sizeof(_icmph), &_icmph);
232 if (icmph == NULL)
233 return 1;
234
235 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
236 return 1;
237
238 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph), sizeof(_inside_iph), &_inside_iph);
239 if (inside_iph == NULL)
240 return 1;
241 inside_nexthdr = inside_iph->nexthdr;
242
243 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) + sizeof(_inside_iph),
244 &inside_nexthdr, &inside_fragoff);
245 if (inside_hdrlen < 0)
246 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
247
248 if (inside_nexthdr != IPPROTO_TCP &&
249 inside_nexthdr != IPPROTO_UDP)
250 return 1;
251
252 ports = skb_header_pointer(skb, inside_hdrlen,
253 sizeof(_ports), &_ports);
254 if (ports == NULL)
255 return 1;
256
257 /* the inside IP packet is the one quoted from our side, thus
258 * its saddr is the local address */
259 *protocol = inside_nexthdr;
260 *laddr = &inside_iph->saddr;
261 *lport = ports[0];
262 *raddr = &inside_iph->daddr;
263 *rport = ports[1];
264
265 return 0;
266}
267
268static bool
269socket_mt6_v1_v2(const struct sk_buff *skb, struct xt_action_param *par)
270{
271 struct ipv6hdr *iph = ipv6_hdr(skb);
272 struct udphdr _hdr, *hp = NULL;
273 struct sock *sk = skb->sk;
274 struct in6_addr *daddr = NULL, *saddr = NULL;
275 __be16 uninitialized_var(dport), uninitialized_var(sport);
276 int thoff = 0, uninitialized_var(tproto);
277 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
278
279 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
280 if (tproto < 0) {
281 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
282 return NF_DROP;
283 }
284
285 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
286 hp = skb_header_pointer(skb, thoff,
287 sizeof(_hdr), &_hdr);
288 if (hp == NULL)
289 return false;
290
291 saddr = &iph->saddr;
292 sport = hp->source;
293 daddr = &iph->daddr;
294 dport = hp->dest;
295
296 } else if (tproto == IPPROTO_ICMPV6) {
297 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
298 &sport, &dport))
299 return false;
300 } else {
301 return false;
302 }
303
304 if (!sk)
305 sk = nf_tproxy_get_sock_v6(dev_net(skb->dev), tproto,
306 saddr, daddr, sport, dport,
307 par->in, NFT_LOOKUP_ANY);
308 if (sk) {
309 bool wildcard;
310 bool transparent = true;
311
312 /* Ignore sockets listening on INADDR_ANY
313 * unless XT_SOCKET_NOWILDCARD is set
314 */
315 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
316 sk->sk_state != TCP_TIME_WAIT &&
317 ipv6_addr_any(&inet6_sk(sk)->rcv_saddr));
318
319 /* Ignore non-transparent sockets,
320 if XT_SOCKET_TRANSPARENT is used */
321 if (info->flags & XT_SOCKET_TRANSPARENT)
322 transparent = ((sk->sk_state != TCP_TIME_WAIT &&
323 inet_sk(sk)->transparent) ||
324 (sk->sk_state == TCP_TIME_WAIT &&
325 inet_twsk(sk)->tw_transparent));
326
327 if (sk != skb->sk)
328 xt_socket_put_sk(sk);
329
330 if (wildcard || !transparent)
331 sk = NULL;
332 }
333
334 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
335 "(orig %pI6:%hu) sock %p\n",
336 tproto, saddr, ntohs(sport),
337 daddr, ntohs(dport),
338 &iph->daddr, hp ? ntohs(hp->dest) : 0, sk);
339
340 return (sk != NULL);
341}
342#endif
343
344static int socket_mt_v1_check(const struct xt_mtchk_param *par)
345{
346 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
347
348 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
349 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
350 return -EINVAL;
351 }
352 return 0;
353}
354
355static int socket_mt_v2_check(const struct xt_mtchk_param *par)
356{
357 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
358
359 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
360 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
361 return -EINVAL;
362 }
363 return 0;
364}
365
366static struct xt_match socket_mt_reg[] __read_mostly = {
367 {
368 .name = "socket",
369 .revision = 0,
370 .family = NFPROTO_IPV4,
371 .match = socket_mt4_v0,
372 .hooks = (1 << NF_INET_PRE_ROUTING) |
373 (1 << NF_INET_LOCAL_IN),
374 .me = THIS_MODULE,
375 },
376 {
377 .name = "socket",
378 .revision = 1,
379 .family = NFPROTO_IPV4,
380 .match = socket_mt4_v1_v2,
381 .checkentry = socket_mt_v1_check,
382 .matchsize = sizeof(struct xt_socket_mtinfo1),
383 .hooks = (1 << NF_INET_PRE_ROUTING) |
384 (1 << NF_INET_LOCAL_IN),
385 .me = THIS_MODULE,
386 },
387#ifdef XT_SOCKET_HAVE_IPV6
388 {
389 .name = "socket",
390 .revision = 1,
391 .family = NFPROTO_IPV6,
392 .match = socket_mt6_v1_v2,
393 .checkentry = socket_mt_v1_check,
394 .matchsize = sizeof(struct xt_socket_mtinfo1),
395 .hooks = (1 << NF_INET_PRE_ROUTING) |
396 (1 << NF_INET_LOCAL_IN),
397 .me = THIS_MODULE,
398 },
399#endif
400 {
401 .name = "socket",
402 .revision = 2,
403 .family = NFPROTO_IPV4,
404 .match = socket_mt4_v1_v2,
405 .checkentry = socket_mt_v2_check,
406 .matchsize = sizeof(struct xt_socket_mtinfo1),
407 .hooks = (1 << NF_INET_PRE_ROUTING) |
408 (1 << NF_INET_LOCAL_IN),
409 .me = THIS_MODULE,
410 },
411#ifdef XT_SOCKET_HAVE_IPV6
412 {
413 .name = "socket",
414 .revision = 2,
415 .family = NFPROTO_IPV6,
416 .match = socket_mt6_v1_v2,
417 .checkentry = socket_mt_v2_check,
418 .matchsize = sizeof(struct xt_socket_mtinfo1),
419 .hooks = (1 << NF_INET_PRE_ROUTING) |
420 (1 << NF_INET_LOCAL_IN),
421 .me = THIS_MODULE,
422 },
423#endif
424};
425
426static int __init socket_mt_init(void)
427{
428 nf_defrag_ipv4_enable();
429#ifdef XT_SOCKET_HAVE_IPV6
430 nf_defrag_ipv6_enable();
431#endif
432
433 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
434}
435
436static void __exit socket_mt_exit(void)
437{
438 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
439}
440
441module_init(socket_mt_init);
442module_exit(socket_mt_exit);
443
444MODULE_LICENSE("GPL");
445MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
446MODULE_DESCRIPTION("x_tables socket match module");
447MODULE_ALIAS("ipt_socket");
448MODULE_ALIAS("ip6t_socket");