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
|
# Copyright 2017 Robert Gustafsson
# Copyright 2017 Robin Krahl
# Copyright 2017 Andreas Lindhé
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# Example usage:
# bro -b -C -i eth0 modbus.bro Log::default_writer=Log::WRITER_NONE
@load frameworks/communication/listen
@load base/protocols/modbus
module Midbro;
redef Pcap::bufsize = 256;
redef Communication::listen_port = 47760/tcp;
redef Communication::listen_ssl = F;
## Global variables
global verbose=F;
## DATA STRUCTURES
export {
redef enum Log::ID += { LOG };
type Transaction: record {
start_address: count;
quantity: count;
};
type TransactionTable: table[count] of Transaction;
type Info: record {
transactions: TransactionTable &default=TransactionTable();
};
type RegisterData: record {
ip: addr &log;
uid: count &log;
regtype: string &log;
address: count &log;
register: count &log;
};
const enable_filtering : bool = T;
const filter_ip_addr : addr = 192.168.215.66;
const filter_mem_addr : count = 64;
}
redef record connection += {
midbro: Info &default=Info();
};
redef Communication::nodes += {
["midbro"] = [$host = 127.0.0.1, $events = /midbro/, $connect=F, $ssl=F]
};
## CUSTOM EVENTS
event modbus_register_received(data: RegisterData) {
Log::write(Midbro::LOG, data);
if(verbose)
print fmt("Received address=%d, register=%d", data$address, data$register);
}
event modbus_unmatched_response(tid: count) {
if(verbose)
print fmt("Unmatched response: tid=%d", tid);
}
## CUSTOM FUNCTIONS
function modbus_check_filter(ip: addr, start_address: count, quantity: count) : bool {
if (!enable_filtering)
return T;
if (ip != filter_ip_addr)
return F;
if (start_address == 0 && quantity == 0)
return T;
if (start_address > filter_mem_addr)
return F;
return filter_mem_addr < start_address + quantity;
}
function midbro_generate_event(transaction: Transaction, c: connection,
headers: ModbusHeaders, registers: ModbusRegisters, regtype: string,
i: count) {
local data = RegisterData(
$ip=c$id$resp_h,
$uid=headers$uid,
$regtype=regtype,
$address=transaction$start_address + i,
$register=registers[i]
);
event modbus_register_received(data);
}
function midbro_generate_events(transaction: Transaction, c: connection,
headers: ModbusHeaders, registers: ModbusRegisters, regtype: string) {
# TODO: check registers size
if (enable_filtering) {
if(verbose)
print fmt("%d %d %d", filter_mem_addr, transaction$start_address, transaction$quantity);
midbro_generate_event(transaction, c, headers, registers, regtype,
filter_mem_addr - transaction$start_address);
} else {
local i = 0;
while (i < transaction$quantity) {
midbro_generate_event(transaction, c, headers, registers, regtype, i);
++i;
}
}
}
## EVENT HANDLERS
event bro_init() &priority=5 {
Log::create_stream(Midbro::LOG, [$columns=RegisterData, $path="midbro-parsed"]);
}
event modbus_read_holding_registers_request(c: connection,
headers: ModbusHeaders, start_address: count, quantity: count) {
if (!midbro_check_filter(c$id$resp_h, start_address, quantity)) {
if(verbose)
print fmt("Filtered %s/%d/%d", c$id$resp_h, start_address, quantity);
return;
}
local tid = headers$tid;
local transaction = Transaction(
$start_address=start_address,
$quantity=quantity
);
c$midbro$transactions[tid] = transaction;
}
event modbus_read_holding_registers_response(c: connection,
headers: ModbusHeaders, registers: ModbusRegisters) {
if (!midbro_check_filter(c$id$resp_h, 0, 0)) {
if(verbose)
print fmt("Filtered %s", c$id$resp_h);
return;
}
local tid = headers$tid;
if (tid !in c$midbro$transactions) {
event midbro_unmatched_response(tid);
return;
}
local transaction = c$midbro$transactions[tid];
delete c$midbro$transactions[tid];
midbro_generate_events(transaction, c, headers, registers, "h");
}
|
