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