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/ipv4/nf_defrag_ipv4.h>
23
24#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
25#define XT_SOCKET_HAVE_IPV6 1
26#include <linux/netfilter_ipv6/ip6_tables.h>
27#include <net/inet6_hashtables.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 int
39extract_icmp4_fields(const struct sk_buff *skb,
40 u8 *protocol,
41 __be32 *raddr,
42 __be32 *laddr,
43 __be16 *rport,
44 __be16 *lport)
45{
46 unsigned int outside_hdrlen = ip_hdrlen(skb);
47 struct iphdr *inside_iph, _inside_iph;
48 struct icmphdr *icmph, _icmph;
49 __be16 *ports, _ports[2];
50
51 icmph = skb_header_pointer(skb, outside_hdrlen,
52 sizeof(_icmph), &_icmph);
53 if (icmph == NULL)
54 return 1;
55
56 switch (icmph->type) {
57 case ICMP_DEST_UNREACH:
58 case ICMP_SOURCE_QUENCH:
59 case ICMP_REDIRECT:
60 case ICMP_TIME_EXCEEDED:
61 case ICMP_PARAMETERPROB:
62 break;
63 default:
64 return 1;
65 }
66
67 inside_iph = skb_header_pointer(skb, outside_hdrlen +
68 sizeof(struct icmphdr),
69 sizeof(_inside_iph), &_inside_iph);
70 if (inside_iph == NULL)
71 return 1;
72
73 if (inside_iph->protocol != IPPROTO_TCP &&
74 inside_iph->protocol != IPPROTO_UDP)
75 return 1;
76
77 ports = skb_header_pointer(skb, outside_hdrlen +
78 sizeof(struct icmphdr) +
79 (inside_iph->ihl << 2),
80 sizeof(_ports), &_ports);
81 if (ports == NULL)
82 return 1;
83
84 /* the inside IP packet is the one quoted from our side, thus
85 * its saddr is the local address */
86 *protocol = inside_iph->protocol;
87 *laddr = inside_iph->saddr;
88 *lport = ports[0];
89 *raddr = inside_iph->daddr;
90 *rport = ports[1];
91
92 return 0;
93}
94
95/* "socket" match based redirection (no specific rule)
96 * ===================================================
97 *
98 * There are connections with dynamic endpoints (e.g. FTP data
99 * connection) that the user is unable to add explicit rules
100 * for. These are taken care of by a generic "socket" rule. It is
101 * assumed that the proxy application is trusted to open such
102 * connections without explicit iptables rule (except of course the
103 * generic 'socket' rule). In this case the following sockets are
104 * matched in preference order:
105 *
106 * - match: if there's a fully established connection matching the
107 * _packet_ tuple
108 *
109 * - match: if there's a non-zero bound listener (possibly with a
110 * non-local address) We don't accept zero-bound listeners, since
111 * then local services could intercept traffic going through the
112 * box.
113 */
114static struct sock *
115xt_socket_get_sock_v4(struct net *net, struct sk_buff *skb, const int doff,
116 const u8 protocol,
117 const __be32 saddr, const __be32 daddr,
118 const __be16 sport, const __be16 dport,
119 const struct net_device *in)
120{
121 switch (protocol) {
122 case IPPROTO_TCP:
123 return inet_lookup(net, &tcp_hashinfo, skb, doff,
124 saddr, sport, daddr, dport,
125 in->ifindex);
126 case IPPROTO_UDP:
127 return udp4_lib_lookup(net, saddr, sport, daddr, dport,
128 in->ifindex);
129 }
130 return NULL;
131}
132
133static bool xt_socket_sk_is_transparent(struct sock *sk)
134{
135 switch (sk->sk_state) {
136 case TCP_TIME_WAIT:
137 return inet_twsk(sk)->tw_transparent;
138
139 case TCP_NEW_SYN_RECV:
140 return inet_rsk(inet_reqsk(sk))->no_srccheck;
141
142 default:
143 return inet_sk(sk)->transparent;
144 }
145}
146
147static struct sock *xt_socket_lookup_slow_v4(struct net *net,
148 const struct sk_buff *skb,
149 const struct net_device *indev)
150{
151 const struct iphdr *iph = ip_hdr(skb);
152 struct sk_buff *data_skb = NULL;
153 int doff = 0;
154 __be32 uninitialized_var(daddr), uninitialized_var(saddr);
155 __be16 uninitialized_var(dport), uninitialized_var(sport);
156 u8 uninitialized_var(protocol);
157#ifdef XT_SOCKET_HAVE_CONNTRACK
158 struct nf_conn const *ct;
159 enum ip_conntrack_info ctinfo;
160#endif
161
162 if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
163 struct udphdr _hdr, *hp;
164
165 hp = skb_header_pointer(skb, ip_hdrlen(skb),
166 sizeof(_hdr), &_hdr);
167 if (hp == NULL)
168 return NULL;
169
170 protocol = iph->protocol;
171 saddr = iph->saddr;
172 sport = hp->source;
173 daddr = iph->daddr;
174 dport = hp->dest;
175 data_skb = (struct sk_buff *)skb;
176 doff = iph->protocol == IPPROTO_TCP ?
177 ip_hdrlen(skb) + __tcp_hdrlen((struct tcphdr *)hp) :
178 ip_hdrlen(skb) + sizeof(*hp);
179
180 } else if (iph->protocol == IPPROTO_ICMP) {
181 if (extract_icmp4_fields(skb, &protocol, &saddr, &daddr,
182 &sport, &dport))
183 return NULL;
184 } else {
185 return NULL;
186 }
187
188#ifdef XT_SOCKET_HAVE_CONNTRACK
189 /* Do the lookup with the original socket address in
190 * case this is a reply packet of an established
191 * SNAT-ted connection.
192 */
193 ct = nf_ct_get(skb, &ctinfo);
194 if (ct && !nf_ct_is_untracked(ct) &&
195 ((iph->protocol != IPPROTO_ICMP &&
196 ctinfo == IP_CT_ESTABLISHED_REPLY) ||
197 (iph->protocol == IPPROTO_ICMP &&
198 ctinfo == IP_CT_RELATED_REPLY)) &&
199 (ct->status & IPS_SRC_NAT_DONE)) {
200
201 daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
202 dport = (iph->protocol == IPPROTO_TCP) ?
203 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
204 ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
205 }
206#endif
207
208 return xt_socket_get_sock_v4(net, data_skb, doff, protocol, saddr,
209 daddr, sport, dport, indev);
210}
211
212static bool
213socket_match(const struct sk_buff *skb, struct xt_action_param *par,
214 const struct xt_socket_mtinfo1 *info)
215{
216 struct sk_buff *pskb = (struct sk_buff *)skb;
217 struct sock *sk = skb->sk;
218
219 if (!sk)
220 sk = xt_socket_lookup_slow_v4(par->net, skb, par->in);
221 if (sk) {
222 bool wildcard;
223 bool transparent = true;
224
225 /* Ignore sockets listening on INADDR_ANY,
226 * unless XT_SOCKET_NOWILDCARD is set
227 */
228 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
229 sk_fullsock(sk) &&
230 inet_sk(sk)->inet_rcv_saddr == 0);
231
232 /* Ignore non-transparent sockets,
233 * if XT_SOCKET_TRANSPARENT is used
234 */
235 if (info->flags & XT_SOCKET_TRANSPARENT)
236 transparent = xt_socket_sk_is_transparent(sk);
237
238 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
239 transparent)
240 pskb->mark = sk->sk_mark;
241
242 if (sk != skb->sk)
243 sock_gen_put(sk);
244
245 if (wildcard || !transparent)
246 sk = NULL;
247 }
248
249 return sk != NULL;
250}
251
252static bool
253socket_mt4_v0(const struct sk_buff *skb, struct xt_action_param *par)
254{
255 static struct xt_socket_mtinfo1 xt_info_v0 = {
256 .flags = 0,
257 };
258
259 return socket_match(skb, par, &xt_info_v0);
260}
261
262static bool
263socket_mt4_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
264{
265 return socket_match(skb, par, par->matchinfo);
266}
267
268#ifdef XT_SOCKET_HAVE_IPV6
269
270static int
271extract_icmp6_fields(const struct sk_buff *skb,
272 unsigned int outside_hdrlen,
273 int *protocol,
274 const struct in6_addr **raddr,
275 const struct in6_addr **laddr,
276 __be16 *rport,
277 __be16 *lport,
278 struct ipv6hdr *ipv6_var)
279{
280 const struct ipv6hdr *inside_iph;
281 struct icmp6hdr *icmph, _icmph;
282 __be16 *ports, _ports[2];
283 u8 inside_nexthdr;
284 __be16 inside_fragoff;
285 int inside_hdrlen;
286
287 icmph = skb_header_pointer(skb, outside_hdrlen,
288 sizeof(_icmph), &_icmph);
289 if (icmph == NULL)
290 return 1;
291
292 if (icmph->icmp6_type & ICMPV6_INFOMSG_MASK)
293 return 1;
294
295 inside_iph = skb_header_pointer(skb, outside_hdrlen + sizeof(_icmph),
296 sizeof(*ipv6_var), ipv6_var);
297 if (inside_iph == NULL)
298 return 1;
299 inside_nexthdr = inside_iph->nexthdr;
300
301 inside_hdrlen = ipv6_skip_exthdr(skb, outside_hdrlen + sizeof(_icmph) +
302 sizeof(*ipv6_var),
303 &inside_nexthdr, &inside_fragoff);
304 if (inside_hdrlen < 0)
305 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
306
307 if (inside_nexthdr != IPPROTO_TCP &&
308 inside_nexthdr != IPPROTO_UDP)
309 return 1;
310
311 ports = skb_header_pointer(skb, inside_hdrlen,
312 sizeof(_ports), &_ports);
313 if (ports == NULL)
314 return 1;
315
316 /* the inside IP packet is the one quoted from our side, thus
317 * its saddr is the local address */
318 *protocol = inside_nexthdr;
319 *laddr = &inside_iph->saddr;
320 *lport = ports[0];
321 *raddr = &inside_iph->daddr;
322 *rport = ports[1];
323
324 return 0;
325}
326
327static struct sock *
328xt_socket_get_sock_v6(struct net *net, struct sk_buff *skb, int doff,
329 const u8 protocol,
330 const struct in6_addr *saddr, const struct in6_addr *daddr,
331 const __be16 sport, const __be16 dport,
332 const struct net_device *in)
333{
334 switch (protocol) {
335 case IPPROTO_TCP:
336 return inet6_lookup(net, &tcp_hashinfo, skb, doff,
337 saddr, sport, daddr, dport,
338 in->ifindex);
339 case IPPROTO_UDP:
340 return udp6_lib_lookup(net, saddr, sport, daddr, dport,
341 in->ifindex);
342 }
343
344 return NULL;
345}
346
347static struct sock *xt_socket_lookup_slow_v6(struct net *net,
348 const struct sk_buff *skb,
349 const struct net_device *indev)
350{
351 __be16 uninitialized_var(dport), uninitialized_var(sport);
352 const struct in6_addr *daddr = NULL, *saddr = NULL;
353 struct ipv6hdr *iph = ipv6_hdr(skb);
354 struct sk_buff *data_skb = NULL;
355 int doff = 0;
356 int thoff = 0, tproto;
357
358 tproto = ipv6_find_hdr(skb, &thoff, -1, NULL, NULL);
359 if (tproto < 0) {
360 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
361 return NULL;
362 }
363
364 if (tproto == IPPROTO_UDP || tproto == IPPROTO_TCP) {
365 struct udphdr _hdr, *hp;
366
367 hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
368 if (hp == NULL)
369 return NULL;
370
371 saddr = &iph->saddr;
372 sport = hp->source;
373 daddr = &iph->daddr;
374 dport = hp->dest;
375 data_skb = (struct sk_buff *)skb;
376 doff = tproto == IPPROTO_TCP ?
377 thoff + __tcp_hdrlen((struct tcphdr *)hp) :
378 thoff + sizeof(*hp);
379
380 } else if (tproto == IPPROTO_ICMPV6) {
381 struct ipv6hdr ipv6_var;
382
383 if (extract_icmp6_fields(skb, thoff, &tproto, &saddr, &daddr,
384 &sport, &dport, &ipv6_var))
385 return NULL;
386 } else {
387 return NULL;
388 }
389
390 return xt_socket_get_sock_v6(net, data_skb, doff, tproto, saddr, daddr,
391 sport, dport, indev);
392}
393
394static bool
395socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
396{
397 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
398 struct sk_buff *pskb = (struct sk_buff *)skb;
399 struct sock *sk = skb->sk;
400
401 if (!sk)
402 sk = xt_socket_lookup_slow_v6(par->net, skb, par->in);
403 if (sk) {
404 bool wildcard;
405 bool transparent = true;
406
407 /* Ignore sockets listening on INADDR_ANY
408 * unless XT_SOCKET_NOWILDCARD is set
409 */
410 wildcard = (!(info->flags & XT_SOCKET_NOWILDCARD) &&
411 sk_fullsock(sk) &&
412 ipv6_addr_any(&sk->sk_v6_rcv_saddr));
413
414 /* Ignore non-transparent sockets,
415 * if XT_SOCKET_TRANSPARENT is used
416 */
417 if (info->flags & XT_SOCKET_TRANSPARENT)
418 transparent = xt_socket_sk_is_transparent(sk);
419
420 if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
421 transparent)
422 pskb->mark = sk->sk_mark;
423
424 if (sk != skb->sk)
425 sock_gen_put(sk);
426
427 if (wildcard || !transparent)
428 sk = NULL;
429 }
430
431 return sk != NULL;
432}
433#endif
434
435static int socket_mt_v1_check(const struct xt_mtchk_param *par)
436{
437 const struct xt_socket_mtinfo1 *info = (struct xt_socket_mtinfo1 *) par->matchinfo;
438
439 if (info->flags & ~XT_SOCKET_FLAGS_V1) {
440 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V1);
441 return -EINVAL;
442 }
443 return 0;
444}
445
446static int socket_mt_v2_check(const struct xt_mtchk_param *par)
447{
448 const struct xt_socket_mtinfo2 *info = (struct xt_socket_mtinfo2 *) par->matchinfo;
449
450 if (info->flags & ~XT_SOCKET_FLAGS_V2) {
451 pr_info("unknown flags 0x%x\n", info->flags & ~XT_SOCKET_FLAGS_V2);
452 return -EINVAL;
453 }
454 return 0;
455}
456
457static int socket_mt_v3_check(const struct xt_mtchk_param *par)
458{
459 const struct xt_socket_mtinfo3 *info =
460 (struct xt_socket_mtinfo3 *)par->matchinfo;
461
462 if (info->flags & ~XT_SOCKET_FLAGS_V3) {
463 pr_info("unknown flags 0x%x\n",
464 info->flags & ~XT_SOCKET_FLAGS_V3);
465 return -EINVAL;
466 }
467 return 0;
468}
469
470static struct xt_match socket_mt_reg[] __read_mostly = {
471 {
472 .name = "socket",
473 .revision = 0,
474 .family = NFPROTO_IPV4,
475 .match = socket_mt4_v0,
476 .hooks = (1 << NF_INET_PRE_ROUTING) |
477 (1 << NF_INET_LOCAL_IN),
478 .me = THIS_MODULE,
479 },
480 {
481 .name = "socket",
482 .revision = 1,
483 .family = NFPROTO_IPV4,
484 .match = socket_mt4_v1_v2_v3,
485 .checkentry = socket_mt_v1_check,
486 .matchsize = sizeof(struct xt_socket_mtinfo1),
487 .hooks = (1 << NF_INET_PRE_ROUTING) |
488 (1 << NF_INET_LOCAL_IN),
489 .me = THIS_MODULE,
490 },
491#ifdef XT_SOCKET_HAVE_IPV6
492 {
493 .name = "socket",
494 .revision = 1,
495 .family = NFPROTO_IPV6,
496 .match = socket_mt6_v1_v2_v3,
497 .checkentry = socket_mt_v1_check,
498 .matchsize = sizeof(struct xt_socket_mtinfo1),
499 .hooks = (1 << NF_INET_PRE_ROUTING) |
500 (1 << NF_INET_LOCAL_IN),
501 .me = THIS_MODULE,
502 },
503#endif
504 {
505 .name = "socket",
506 .revision = 2,
507 .family = NFPROTO_IPV4,
508 .match = socket_mt4_v1_v2_v3,
509 .checkentry = socket_mt_v2_check,
510 .matchsize = sizeof(struct xt_socket_mtinfo1),
511 .hooks = (1 << NF_INET_PRE_ROUTING) |
512 (1 << NF_INET_LOCAL_IN),
513 .me = THIS_MODULE,
514 },
515#ifdef XT_SOCKET_HAVE_IPV6
516 {
517 .name = "socket",
518 .revision = 2,
519 .family = NFPROTO_IPV6,
520 .match = socket_mt6_v1_v2_v3,
521 .checkentry = socket_mt_v2_check,
522 .matchsize = sizeof(struct xt_socket_mtinfo1),
523 .hooks = (1 << NF_INET_PRE_ROUTING) |
524 (1 << NF_INET_LOCAL_IN),
525 .me = THIS_MODULE,
526 },
527#endif
528 {
529 .name = "socket",
530 .revision = 3,
531 .family = NFPROTO_IPV4,
532 .match = socket_mt4_v1_v2_v3,
533 .checkentry = socket_mt_v3_check,
534 .matchsize = sizeof(struct xt_socket_mtinfo1),
535 .hooks = (1 << NF_INET_PRE_ROUTING) |
536 (1 << NF_INET_LOCAL_IN),
537 .me = THIS_MODULE,
538 },
539#ifdef XT_SOCKET_HAVE_IPV6
540 {
541 .name = "socket",
542 .revision = 3,
543 .family = NFPROTO_IPV6,
544 .match = socket_mt6_v1_v2_v3,
545 .checkentry = socket_mt_v3_check,
546 .matchsize = sizeof(struct xt_socket_mtinfo1),
547 .hooks = (1 << NF_INET_PRE_ROUTING) |
548 (1 << NF_INET_LOCAL_IN),
549 .me = THIS_MODULE,
550 },
551#endif
552};
553
554static int __init socket_mt_init(void)
555{
556 nf_defrag_ipv4_enable();
557#ifdef XT_SOCKET_HAVE_IPV6
558 nf_defrag_ipv6_enable();
559#endif
560
561 return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
562}
563
564static void __exit socket_mt_exit(void)
565{
566 xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg));
567}
568
569module_init(socket_mt_init);
570module_exit(socket_mt_exit);
571
572MODULE_LICENSE("GPL");
573MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
574MODULE_DESCRIPTION("x_tables socket match module");
575MODULE_ALIAS("ipt_socket");
576MODULE_ALIAS("ip6t_socket");