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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 | |
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 | #include <linux/netfilter/xt_socket.h> |
26 | |
27 | #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) |
28 | #define XT_SOCKET_HAVE_CONNTRACK 1 |
29 | #include <net/netfilter/nf_conntrack.h> |
30 | #endif |
31 | |
32 | static int |
33 | extract_icmp_fields(const struct sk_buff *skb, |
34 | u8 *protocol, |
35 | __be32 *raddr, |
36 | __be32 *laddr, |
37 | __be16 *rport, |
38 | __be16 *lport) |
39 | { |
40 | unsigned int outside_hdrlen = ip_hdrlen(skb); |
41 | struct iphdr *inside_iph, _inside_iph; |
42 | struct icmphdr *icmph, _icmph; |
43 | __be16 *ports, _ports[2]; |
44 | |
45 | icmph = skb_header_pointer(skb, outside_hdrlen, |
46 | sizeof(_icmph), &_icmph); |
47 | if (icmph == NULL) |
48 | return 1; |
49 | |
50 | switch (icmph->type) { |
51 | case ICMP_DEST_UNREACH: |
52 | case ICMP_SOURCE_QUENCH: |
53 | case ICMP_REDIRECT: |
54 | case ICMP_TIME_EXCEEDED: |
55 | case ICMP_PARAMETERPROB: |
56 | break; |
57 | default: |
58 | return 1; |
59 | } |
60 | |
61 | inside_iph = skb_header_pointer(skb, outside_hdrlen + |
62 | sizeof(struct icmphdr), |
63 | sizeof(_inside_iph), &_inside_iph); |
64 | if (inside_iph == NULL) |
65 | return 1; |
66 | |
67 | if (inside_iph->protocol != IPPROTO_TCP && |
68 | inside_iph->protocol != IPPROTO_UDP) |
69 | return 1; |
70 | |
71 | ports = skb_header_pointer(skb, outside_hdrlen + |
72 | sizeof(struct icmphdr) + |
73 | (inside_iph->ihl << 2), |
74 | sizeof(_ports), &_ports); |
75 | if (ports == NULL) |
76 | return 1; |
77 | |
78 | /* the inside IP packet is the one quoted from our side, thus |
79 | * its saddr is the local address */ |
80 | *protocol = inside_iph->protocol; |
81 | *laddr = inside_iph->saddr; |
82 | *lport = ports[0]; |
83 | *raddr = inside_iph->daddr; |
84 | *rport = ports[1]; |
85 | |
86 | return 0; |
87 | } |
88 | |
89 | |
90 | static bool |
91 | socket_match(const struct sk_buff *skb, const struct xt_match_param *par, |
92 | const struct xt_socket_mtinfo1 *info) |
93 | { |
94 | const struct iphdr *iph = ip_hdr(skb); |
95 | struct udphdr _hdr, *hp = NULL; |
96 | struct sock *sk; |
97 | __be32 daddr, saddr; |
98 | __be16 dport, sport; |
99 | u8 protocol; |
100 | #ifdef XT_SOCKET_HAVE_CONNTRACK |
101 | struct nf_conn const *ct; |
102 | enum ip_conntrack_info ctinfo; |
103 | #endif |
104 | |
105 | if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) { |
106 | hp = skb_header_pointer(skb, ip_hdrlen(skb), |
107 | sizeof(_hdr), &_hdr); |
108 | if (hp == NULL) |
109 | return false; |
110 | |
111 | protocol = iph->protocol; |
112 | saddr = iph->saddr; |
113 | sport = hp->source; |
114 | daddr = iph->daddr; |
115 | dport = hp->dest; |
116 | |
117 | } else if (iph->protocol == IPPROTO_ICMP) { |
118 | if (extract_icmp_fields(skb, &protocol, &saddr, &daddr, |
119 | &sport, &dport)) |
120 | return false; |
121 | } else { |
122 | return false; |
123 | } |
124 | |
125 | #ifdef XT_SOCKET_HAVE_CONNTRACK |
126 | /* Do the lookup with the original socket address in case this is a |
127 | * reply packet of an established SNAT-ted connection. */ |
128 | |
129 | ct = nf_ct_get(skb, &ctinfo); |
130 | if (ct && (ct != &nf_conntrack_untracked) && |
131 | ((iph->protocol != IPPROTO_ICMP && |
132 | ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) || |
133 | (iph->protocol == IPPROTO_ICMP && |
134 | ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) && |
135 | (ct->status & IPS_SRC_NAT_DONE)) { |
136 | |
137 | daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip; |
138 | dport = (iph->protocol == IPPROTO_TCP) ? |
139 | ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port : |
140 | ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port; |
141 | } |
142 | #endif |
143 | |
144 | sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol, |
145 | saddr, daddr, sport, dport, par->in, false); |
146 | if (sk != NULL) { |
147 | bool wildcard; |
148 | bool transparent = true; |
149 | |
150 | /* Ignore sockets listening on INADDR_ANY */ |
151 | wildcard = (sk->sk_state != TCP_TIME_WAIT && |
152 | inet_sk(sk)->inet_rcv_saddr == 0); |
153 | |
154 | /* Ignore non-transparent sockets, |
155 | if XT_SOCKET_TRANSPARENT is used */ |
156 | if (info && info->flags & XT_SOCKET_TRANSPARENT) |
157 | transparent = ((sk->sk_state != TCP_TIME_WAIT && |
158 | inet_sk(sk)->transparent) || |
159 | (sk->sk_state == TCP_TIME_WAIT && |
160 | inet_twsk(sk)->tw_transparent)); |
161 | |
162 | nf_tproxy_put_sock(sk); |
163 | |
164 | if (wildcard || !transparent) |
165 | sk = NULL; |
166 | } |
167 | |
168 | pr_debug("socket match: proto %u %08x:%u -> %08x:%u " |
169 | "(orig %08x:%u) sock %p\n", |
170 | protocol, ntohl(saddr), ntohs(sport), |
171 | ntohl(daddr), ntohs(dport), |
172 | ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk); |
173 | |
174 | return (sk != NULL); |
175 | } |
176 | |
177 | static bool |
178 | socket_mt_v0(const struct sk_buff *skb, const struct xt_match_param *par) |
179 | { |
180 | return socket_match(skb, par, NULL); |
181 | } |
182 | |
183 | static bool |
184 | socket_mt_v1(const struct sk_buff *skb, const struct xt_match_param *par) |
185 | { |
186 | return socket_match(skb, par, par->matchinfo); |
187 | } |
188 | |
189 | static struct xt_match socket_mt_reg[] __read_mostly = { |
190 | { |
191 | .name = "socket", |
192 | .revision = 0, |
193 | .family = NFPROTO_IPV4, |
194 | .match = socket_mt_v0, |
195 | .hooks = (1 << NF_INET_PRE_ROUTING) | |
196 | (1 << NF_INET_LOCAL_IN), |
197 | .me = THIS_MODULE, |
198 | }, |
199 | { |
200 | .name = "socket", |
201 | .revision = 1, |
202 | .family = NFPROTO_IPV4, |
203 | .match = socket_mt_v1, |
204 | .matchsize = sizeof(struct xt_socket_mtinfo1), |
205 | .hooks = (1 << NF_INET_PRE_ROUTING) | |
206 | (1 << NF_INET_LOCAL_IN), |
207 | .me = THIS_MODULE, |
208 | }, |
209 | }; |
210 | |
211 | static int __init socket_mt_init(void) |
212 | { |
213 | nf_defrag_ipv4_enable(); |
214 | return xt_register_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); |
215 | } |
216 | |
217 | static void __exit socket_mt_exit(void) |
218 | { |
219 | xt_unregister_matches(socket_mt_reg, ARRAY_SIZE(socket_mt_reg)); |
220 | } |
221 | |
222 | module_init(socket_mt_init); |
223 | module_exit(socket_mt_exit); |
224 | |
225 | MODULE_LICENSE("GPL"); |
226 | MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler"); |
227 | MODULE_DESCRIPTION("x_tables socket match module"); |
228 | MODULE_ALIAS("ipt_socket"); |
229 |
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