2 * Transparent proxy support for Linux/iptables
4 * Copyright (C) 2007-2008 BalaBit IT Ltd.
5 * Author: Krisztian Kovacs
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.
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>
21 #include <net/inet_sock.h>
22 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
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>
31 #include <linux/netfilter/xt_socket.h>
33 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
34 #define XT_SOCKET_HAVE_CONNTRACK 1
35 #include <net/netfilter/nf_conntrack.h>
39 extract_icmp4_fields(const struct sk_buff
*skb
,
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];
51 icmph
= skb_header_pointer(skb
, outside_hdrlen
,
52 sizeof(_icmph
), &_icmph
);
56 switch (icmph
->type
) {
57 case ICMP_DEST_UNREACH
:
58 case ICMP_SOURCE_QUENCH
:
60 case ICMP_TIME_EXCEEDED
:
61 case ICMP_PARAMETERPROB
:
67 inside_iph
= skb_header_pointer(skb
, outside_hdrlen
+
68 sizeof(struct icmphdr
),
69 sizeof(_inside_iph
), &_inside_iph
);
70 if (inside_iph
== NULL
)
73 if (inside_iph
->protocol
!= IPPROTO_TCP
&&
74 inside_iph
->protocol
!= IPPROTO_UDP
)
77 ports
= skb_header_pointer(skb
, outside_hdrlen
+
78 sizeof(struct icmphdr
) +
79 (inside_iph
->ihl
<< 2),
80 sizeof(_ports
), &_ports
);
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
;
89 *raddr
= inside_iph
->daddr
;
95 /* "socket" match based redirection (no specific rule)
96 * ===================================================
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:
106 * - match: if there's a fully established connection matching the
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
115 xt_socket_get_sock_v4(struct net
*net
, const u8 protocol
,
116 const __be32 saddr
, const __be32 daddr
,
117 const __be16 sport
, const __be16 dport
,
118 const struct net_device
*in
)
122 return __inet_lookup(net
, &tcp_hashinfo
,
123 saddr
, sport
, daddr
, dport
,
126 return udp4_lib_lookup(net
, saddr
, sport
, daddr
, dport
,
133 socket_match(const struct sk_buff
*skb
, struct xt_action_param
*par
,
134 const struct xt_socket_mtinfo1
*info
)
136 const struct iphdr
*iph
= ip_hdr(skb
);
137 struct udphdr _hdr
, *hp
= NULL
;
138 struct sock
*sk
= skb
->sk
;
139 __be32
uninitialized_var(daddr
), uninitialized_var(saddr
);
140 __be16
uninitialized_var(dport
), uninitialized_var(sport
);
141 u8
uninitialized_var(protocol
);
142 #ifdef XT_SOCKET_HAVE_CONNTRACK
143 struct nf_conn
const *ct
;
144 enum ip_conntrack_info ctinfo
;
147 if (iph
->protocol
== IPPROTO_UDP
|| iph
->protocol
== IPPROTO_TCP
) {
148 hp
= skb_header_pointer(skb
, ip_hdrlen(skb
),
149 sizeof(_hdr
), &_hdr
);
153 protocol
= iph
->protocol
;
159 } else if (iph
->protocol
== IPPROTO_ICMP
) {
160 if (extract_icmp4_fields(skb
, &protocol
, &saddr
, &daddr
,
167 #ifdef XT_SOCKET_HAVE_CONNTRACK
168 /* Do the lookup with the original socket address in case this is a
169 * reply packet of an established SNAT-ted connection. */
171 ct
= nf_ct_get(skb
, &ctinfo
);
172 if (ct
&& !nf_ct_is_untracked(ct
) &&
173 ((iph
->protocol
!= IPPROTO_ICMP
&&
174 ctinfo
== IP_CT_ESTABLISHED_REPLY
) ||
175 (iph
->protocol
== IPPROTO_ICMP
&&
176 ctinfo
== IP_CT_RELATED_REPLY
)) &&
177 (ct
->status
& IPS_SRC_NAT_DONE
)) {
179 daddr
= ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
.src
.u3
.ip
;
180 dport
= (iph
->protocol
== IPPROTO_TCP
) ?
181 ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
.src
.u
.tcp
.port
:
182 ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
.src
.u
.udp
.port
;
187 sk
= xt_socket_get_sock_v4(dev_net(skb
->dev
), protocol
,
188 saddr
, daddr
, sport
, dport
,
192 bool transparent
= true;
194 /* Ignore sockets listening on INADDR_ANY,
195 * unless XT_SOCKET_NOWILDCARD is set
197 wildcard
= (!(info
->flags
& XT_SOCKET_NOWILDCARD
) &&
198 sk
->sk_state
!= TCP_TIME_WAIT
&&
199 inet_sk(sk
)->inet_rcv_saddr
== 0);
201 /* Ignore non-transparent sockets,
202 if XT_SOCKET_TRANSPARENT is used */
203 if (info
->flags
& XT_SOCKET_TRANSPARENT
)
204 transparent
= ((sk
->sk_state
!= TCP_TIME_WAIT
&&
205 inet_sk(sk
)->transparent
) ||
206 (sk
->sk_state
== TCP_TIME_WAIT
&&
207 inet_twsk(sk
)->tw_transparent
));
212 if (wildcard
|| !transparent
)
216 pr_debug("proto %hhu %pI4:%hu -> %pI4:%hu (orig %pI4:%hu) sock %p\n",
217 protocol
, &saddr
, ntohs(sport
),
218 &daddr
, ntohs(dport
),
219 &iph
->daddr
, hp
? ntohs(hp
->dest
) : 0, sk
);
225 socket_mt4_v0(const struct sk_buff
*skb
, struct xt_action_param
*par
)
227 static struct xt_socket_mtinfo1 xt_info_v0
= {
231 return socket_match(skb
, par
, &xt_info_v0
);
235 socket_mt4_v1_v2(const struct sk_buff
*skb
, struct xt_action_param
*par
)
237 return socket_match(skb
, par
, par
->matchinfo
);
240 #ifdef XT_SOCKET_HAVE_IPV6
243 extract_icmp6_fields(const struct sk_buff
*skb
,
244 unsigned int outside_hdrlen
,
246 const struct in6_addr
**raddr
,
247 const struct in6_addr
**laddr
,
250 struct ipv6hdr
*ipv6_var
)
252 const struct ipv6hdr
*inside_iph
;
253 struct icmp6hdr
*icmph
, _icmph
;
254 __be16
*ports
, _ports
[2];
256 __be16 inside_fragoff
;
259 icmph
= skb_header_pointer(skb
, outside_hdrlen
,
260 sizeof(_icmph
), &_icmph
);
264 if (icmph
->icmp6_type
& ICMPV6_INFOMSG_MASK
)
267 inside_iph
= skb_header_pointer(skb
, outside_hdrlen
+ sizeof(_icmph
),
268 sizeof(*ipv6_var
), ipv6_var
);
269 if (inside_iph
== NULL
)
271 inside_nexthdr
= inside_iph
->nexthdr
;
273 inside_hdrlen
= ipv6_skip_exthdr(skb
, outside_hdrlen
+ sizeof(_icmph
) +
275 &inside_nexthdr
, &inside_fragoff
);
276 if (inside_hdrlen
< 0)
277 return 1; /* hjm: Packet has no/incomplete transport layer headers. */
279 if (inside_nexthdr
!= IPPROTO_TCP
&&
280 inside_nexthdr
!= IPPROTO_UDP
)
283 ports
= skb_header_pointer(skb
, inside_hdrlen
,
284 sizeof(_ports
), &_ports
);
288 /* the inside IP packet is the one quoted from our side, thus
289 * its saddr is the local address */
290 *protocol
= inside_nexthdr
;
291 *laddr
= &inside_iph
->saddr
;
293 *raddr
= &inside_iph
->daddr
;
300 xt_socket_get_sock_v6(struct net
*net
, const u8 protocol
,
301 const struct in6_addr
*saddr
, const struct in6_addr
*daddr
,
302 const __be16 sport
, const __be16 dport
,
303 const struct net_device
*in
)
307 return inet6_lookup(net
, &tcp_hashinfo
,
308 saddr
, sport
, daddr
, dport
,
311 return udp6_lib_lookup(net
, saddr
, sport
, daddr
, dport
,
319 socket_mt6_v1_v2(const struct sk_buff
*skb
, struct xt_action_param
*par
)
321 struct ipv6hdr ipv6_var
, *iph
= ipv6_hdr(skb
);
322 struct udphdr _hdr
, *hp
= NULL
;
323 struct sock
*sk
= skb
->sk
;
324 const struct in6_addr
*daddr
= NULL
, *saddr
= NULL
;
325 __be16
uninitialized_var(dport
), uninitialized_var(sport
);
326 int thoff
= 0, uninitialized_var(tproto
);
327 const struct xt_socket_mtinfo1
*info
= (struct xt_socket_mtinfo1
*) par
->matchinfo
;
329 tproto
= ipv6_find_hdr(skb
, &thoff
, -1, NULL
, NULL
);
331 pr_debug("unable to find transport header in IPv6 packet, dropping\n");
335 if (tproto
== IPPROTO_UDP
|| tproto
== IPPROTO_TCP
) {
336 hp
= skb_header_pointer(skb
, thoff
,
337 sizeof(_hdr
), &_hdr
);
346 } else if (tproto
== IPPROTO_ICMPV6
) {
347 if (extract_icmp6_fields(skb
, thoff
, &tproto
, &saddr
, &daddr
,
348 &sport
, &dport
, &ipv6_var
))
355 sk
= xt_socket_get_sock_v6(dev_net(skb
->dev
), tproto
,
356 saddr
, daddr
, sport
, dport
,
360 bool transparent
= true;
362 /* Ignore sockets listening on INADDR_ANY
363 * unless XT_SOCKET_NOWILDCARD is set
365 wildcard
= (!(info
->flags
& XT_SOCKET_NOWILDCARD
) &&
366 sk
->sk_state
!= TCP_TIME_WAIT
&&
367 ipv6_addr_any(&sk
->sk_v6_rcv_saddr
));
369 /* Ignore non-transparent sockets,
370 if XT_SOCKET_TRANSPARENT is used */
371 if (info
->flags
& XT_SOCKET_TRANSPARENT
)
372 transparent
= ((sk
->sk_state
!= TCP_TIME_WAIT
&&
373 inet_sk(sk
)->transparent
) ||
374 (sk
->sk_state
== TCP_TIME_WAIT
&&
375 inet_twsk(sk
)->tw_transparent
));
380 if (wildcard
|| !transparent
)
384 pr_debug("proto %hhd %pI6:%hu -> %pI6:%hu "
385 "(orig %pI6:%hu) sock %p\n",
386 tproto
, saddr
, ntohs(sport
),
388 &iph
->daddr
, hp
? ntohs(hp
->dest
) : 0, sk
);
394 static int socket_mt_v1_check(const struct xt_mtchk_param
*par
)
396 const struct xt_socket_mtinfo1
*info
= (struct xt_socket_mtinfo1
*) par
->matchinfo
;
398 if (info
->flags
& ~XT_SOCKET_FLAGS_V1
) {
399 pr_info("unknown flags 0x%x\n", info
->flags
& ~XT_SOCKET_FLAGS_V1
);
405 static int socket_mt_v2_check(const struct xt_mtchk_param
*par
)
407 const struct xt_socket_mtinfo2
*info
= (struct xt_socket_mtinfo2
*) par
->matchinfo
;
409 if (info
->flags
& ~XT_SOCKET_FLAGS_V2
) {
410 pr_info("unknown flags 0x%x\n", info
->flags
& ~XT_SOCKET_FLAGS_V2
);
416 static struct xt_match socket_mt_reg
[] __read_mostly
= {
420 .family
= NFPROTO_IPV4
,
421 .match
= socket_mt4_v0
,
422 .hooks
= (1 << NF_INET_PRE_ROUTING
) |
423 (1 << NF_INET_LOCAL_IN
),
429 .family
= NFPROTO_IPV4
,
430 .match
= socket_mt4_v1_v2
,
431 .checkentry
= socket_mt_v1_check
,
432 .matchsize
= sizeof(struct xt_socket_mtinfo1
),
433 .hooks
= (1 << NF_INET_PRE_ROUTING
) |
434 (1 << NF_INET_LOCAL_IN
),
437 #ifdef XT_SOCKET_HAVE_IPV6
441 .family
= NFPROTO_IPV6
,
442 .match
= socket_mt6_v1_v2
,
443 .checkentry
= socket_mt_v1_check
,
444 .matchsize
= sizeof(struct xt_socket_mtinfo1
),
445 .hooks
= (1 << NF_INET_PRE_ROUTING
) |
446 (1 << NF_INET_LOCAL_IN
),
453 .family
= NFPROTO_IPV4
,
454 .match
= socket_mt4_v1_v2
,
455 .checkentry
= socket_mt_v2_check
,
456 .matchsize
= sizeof(struct xt_socket_mtinfo1
),
457 .hooks
= (1 << NF_INET_PRE_ROUTING
) |
458 (1 << NF_INET_LOCAL_IN
),
461 #ifdef XT_SOCKET_HAVE_IPV6
465 .family
= NFPROTO_IPV6
,
466 .match
= socket_mt6_v1_v2
,
467 .checkentry
= socket_mt_v2_check
,
468 .matchsize
= sizeof(struct xt_socket_mtinfo1
),
469 .hooks
= (1 << NF_INET_PRE_ROUTING
) |
470 (1 << NF_INET_LOCAL_IN
),
476 static int __init
socket_mt_init(void)
478 nf_defrag_ipv4_enable();
479 #ifdef XT_SOCKET_HAVE_IPV6
480 nf_defrag_ipv6_enable();
483 return xt_register_matches(socket_mt_reg
, ARRAY_SIZE(socket_mt_reg
));
486 static void __exit
socket_mt_exit(void)
488 xt_unregister_matches(socket_mt_reg
, ARRAY_SIZE(socket_mt_reg
));
491 module_init(socket_mt_init
);
492 module_exit(socket_mt_exit
);
494 MODULE_LICENSE("GPL");
495 MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
496 MODULE_DESCRIPTION("x_tables socket match module");
497 MODULE_ALIAS("ipt_socket");
498 MODULE_ALIAS("ip6t_socket");