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
|
/*
* Copyright (C) 2010 Martin Willi
* Copyright (C) 2010 revosec AG
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
#include "farp_spoofer.h"
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/filter.h>
#include <sys/ioctl.h>
#include <daemon.h>
#include <threading/thread.h>
#include <processing/jobs/callback_job.h>
typedef struct private_farp_spoofer_t private_farp_spoofer_t;
/**
* Private data of an farp_spoofer_t object.
*/
struct private_farp_spoofer_t {
/**
* Public farp_spoofer_t interface.
*/
farp_spoofer_t public;
/**
* Listener that knows active addresses
*/
farp_listener_t *listener;
/**
* RAW socket for ARP requests
*/
int skt;
};
/**
* IP over Ethernet ARP message
*/
typedef struct __attribute__((packed)) {
u_int16_t hardware_type;
u_int16_t protocol_type;
u_int8_t hardware_size;
u_int8_t protocol_size;
u_int16_t opcode;
u_int8_t sender_mac[6];
u_int8_t sender_ip[4];
u_int8_t target_mac[6];
u_int8_t target_ip[4];
} arp_t;
/**
* Send faked ARP response
*/
static void send_arp(private_farp_spoofer_t *this,
arp_t *arp, struct sockaddr_ll *addr)
{
struct ifreq req;
char tmp[4];
req.ifr_ifindex = addr->sll_ifindex;
if (ioctl(this->skt, SIOCGIFNAME, &req) == 0 &&
ioctl(this->skt, SIOCGIFHWADDR, &req) == 0 &&
req.ifr_hwaddr.sa_family == ARPHRD_ETHER)
{
memcpy(arp->target_mac, arp->sender_mac, 6);
memcpy(arp->sender_mac, req.ifr_hwaddr.sa_data, 6);
memcpy(tmp, arp->sender_ip, 4);
memcpy(arp->sender_ip, arp->target_ip, 4);
memcpy(arp->target_ip, tmp, 4);
arp->opcode = htons(ARPOP_REPLY);
sendto(this->skt, arp, sizeof(*arp), 0,
(struct sockaddr*)addr, sizeof(*addr));
}
}
/**
* ARP request receiving
*/
static job_requeue_t receive_arp(private_farp_spoofer_t *this)
{
struct sockaddr_ll addr;
socklen_t addr_len = sizeof(addr);
arp_t arp;
int oldstate;
ssize_t len;
host_t *local, *remote;
oldstate = thread_cancelability(TRUE);
len = recvfrom(this->skt, &arp, sizeof(arp), 0,
(struct sockaddr*)&addr, &addr_len);
thread_cancelability(oldstate);
if (len == sizeof(arp))
{
local = host_create_from_chunk(AF_INET,
chunk_create((char*)&arp.sender_ip, 4), 0);
remote = host_create_from_chunk(AF_INET,
chunk_create((char*)&arp.target_ip, 4), 0);
if (this->listener->has_tunnel(this->listener, local, remote))
{
send_arp(this, &arp, &addr);
}
local->destroy(local);
remote->destroy(remote);
}
return JOB_REQUEUE_DIRECT;
}
METHOD(farp_spoofer_t, destroy, void,
private_farp_spoofer_t *this)
{
close(this->skt);
free(this);
}
/**
* See header
*/
farp_spoofer_t *farp_spoofer_create(farp_listener_t *listener)
{
private_farp_spoofer_t *this;
struct sock_filter arp_request_filter_code[] = {
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, offsetof(arp_t, protocol_type)),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ETH_P_IP, 0, 9),
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, offsetof(arp_t, hardware_size)),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 6, 0, 7),
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, offsetof(arp_t, protocol_size)),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 4, 0, 4),
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, offsetof(arp_t, opcode)),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ARPOP_REQUEST, 0, 3),
BPF_STMT(BPF_LD+BPF_W+BPF_LEN, 0),
BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, sizeof(arp_t), 0, 1),
BPF_STMT(BPF_RET+BPF_K, sizeof(arp_t)),
BPF_STMT(BPF_RET+BPF_K, 0),
};
struct sock_fprog arp_request_filter = {
sizeof(arp_request_filter_code) / sizeof(struct sock_filter),
arp_request_filter_code,
};
INIT(this,
.public = {
.destroy = _destroy,
},
.listener = listener,
);
this->skt = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ARP));
if (this->skt == -1)
{
DBG1(DBG_NET, "opening ARP packet socket failed: %s", strerror(errno));
free(this);
return NULL;
}
if (setsockopt(this->skt, SOL_SOCKET, SO_ATTACH_FILTER,
&arp_request_filter, sizeof(arp_request_filter)) < 0)
{
DBG1(DBG_NET, "installing ARP packet filter failed: %s", strerror(errno));
close(this->skt);
free(this);
return NULL;
}
lib->processor->queue_job(lib->processor,
(job_t*)callback_job_create_with_prio((callback_job_cb_t)receive_arp,
this, NULL, (callback_job_cancel_t)return_false, JOB_PRIO_CRITICAL));
return &this->public;
}
|
