1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
/*
* Transparent proxy support for Linux/iptables
*
* Copyright (C) 2007-2008 BalaBit IT Ltd.
* Author: Krisztian Kovacs
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <net/sock.h>
#include <net/inet_sock.h>
#include <net/netfilter/nf_tproxy_core.h>
#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
#define XT_SOCKET_HAVE_CONNTRACK 1
#include <net/netfilter/nf_conntrack.h>
#endif
static int
extract_icmp_fields(const struct sk_buff *skb,
u8 *protocol,
__be32 *raddr,
__be32 *laddr,
__be16 *rport,
__be16 *lport)
{
unsigned int outside_hdrlen = ip_hdrlen(skb);
struct iphdr *inside_iph, _inside_iph;
struct icmphdr *icmph, _icmph;
__be16 *ports, _ports[2];
icmph = skb_header_pointer(skb, outside_hdrlen,
sizeof(_icmph), &_icmph);
if (icmph == NULL)
return 1;
switch (icmph->type) {
case ICMP_DEST_UNREACH:
case ICMP_SOURCE_QUENCH:
case ICMP_REDIRECT:
case ICMP_TIME_EXCEEDED:
case ICMP_PARAMETERPROB:
break;
default:
return 1;
}
inside_iph = skb_header_pointer(skb, outside_hdrlen +
sizeof(struct icmphdr),
sizeof(_inside_iph), &_inside_iph);
if (inside_iph == NULL)
return 1;
if (inside_iph->protocol != IPPROTO_TCP &&
inside_iph->protocol != IPPROTO_UDP)
return 1;
ports = skb_header_pointer(skb, outside_hdrlen +
sizeof(struct icmphdr) +
(inside_iph->ihl << 2),
sizeof(_ports), &_ports);
if (ports == NULL)
return 1;
/* the inside IP packet is the one quoted from our side, thus
* its saddr is the local address */
*protocol = inside_iph->protocol;
*laddr = inside_iph->saddr;
*lport = ports[0];
*raddr = inside_iph->daddr;
*rport = ports[1];
return 0;
}
static bool
socket_mt(const struct sk_buff *skb,
const struct net_device *in,
const struct net_device *out,
const struct xt_match *match,
const void *matchinfo,
int offset,
unsigned int protoff,
bool *hotdrop)
{
const struct iphdr *iph = ip_hdr(skb);
struct udphdr _hdr, *hp = NULL;
struct sock *sk;
__be32 daddr, saddr;
__be16 dport, sport;
u8 protocol;
#ifdef XT_SOCKET_HAVE_CONNTRACK
struct nf_conn const *ct;
enum ip_conntrack_info ctinfo;
#endif
if (iph->protocol == IPPROTO_UDP || iph->protocol == IPPROTO_TCP) {
hp = skb_header_pointer(skb, ip_hdrlen(skb),
sizeof(_hdr), &_hdr);
if (hp == NULL)
return false;
protocol = iph->protocol;
saddr = iph->saddr;
sport = hp->source;
daddr = iph->daddr;
dport = hp->dest;
} else if (iph->protocol == IPPROTO_ICMP) {
if (extract_icmp_fields(skb, &protocol, &saddr, &daddr,
&sport, &dport))
return false;
} else {
return false;
}
#ifdef XT_SOCKET_HAVE_CONNTRACK
/* Do the lookup with the original socket address in case this is a
* reply packet of an established SNAT-ted connection. */
ct = nf_ct_get(skb, &ctinfo);
if (ct && (ct != &nf_conntrack_untracked) &&
((iph->protocol != IPPROTO_ICMP &&
ctinfo == IP_CT_IS_REPLY + IP_CT_ESTABLISHED) ||
(iph->protocol == IPPROTO_ICMP &&
ctinfo == IP_CT_IS_REPLY + IP_CT_RELATED)) &&
(ct->status & IPS_SRC_NAT_DONE)) {
daddr = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip;
dport = (iph->protocol == IPPROTO_TCP) ?
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.tcp.port :
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
}
#endif
sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), protocol,
saddr, daddr, sport, dport, in, false);
if (sk != NULL) {
bool wildcard = (inet_sk(sk)->rcv_saddr == 0);
nf_tproxy_put_sock(sk);
if (wildcard)
sk = NULL;
}
pr_debug("socket match: proto %u %08x:%u -> %08x:%u "
"(orig %08x:%u) sock %p\n",
protocol, ntohl(saddr), ntohs(sport),
ntohl(daddr), ntohs(dport),
ntohl(iph->daddr), hp ? ntohs(hp->dest) : 0, sk);
return (sk != NULL);
}
static struct xt_match socket_mt_reg __read_mostly = {
.name = "socket",
.family = AF_INET,
.match = socket_mt,
.hooks = 1 << NF_INET_PRE_ROUTING,
.me = THIS_MODULE,
};
static int __init socket_mt_init(void)
{
nf_defrag_ipv4_enable();
return xt_register_match(&socket_mt_reg);
}
static void __exit socket_mt_exit(void)
{
xt_unregister_match(&socket_mt_reg);
}
module_init(socket_mt_init);
module_exit(socket_mt_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Krisztian Kovacs, Balazs Scheidler");
MODULE_DESCRIPTION("x_tables socket match module");
MODULE_ALIAS("ipt_socket");
|
