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# 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 midbro_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$quantity) {
midbro_generate_event(transaction, c, headers, registers, regtype, i);
++i;
}
}
}
function midbro_handle_read_request(c: connection, headers: ModbusHeaders,
start_address: count, quantity: count) {
if (!midbro_check_filter(c$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$transactions[tid] = transaction;
}
function midbro_handle_read_response(c: connection, headers: ModbusHeaders,
registers: ModbusRegisters, regtype: string) {
if (!midbro_check_filter(c$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 modbus_unmatched_response(tid);
return;
}
local transaction = c$midbro$transactions[tid];
delete c$midbro$transactions[tid];
midbro_generate_events(transaction, c, headers, registers, regtype);
}
function midbro_handle_write_request(c: connection, headers: ModbusHeaders,
start_address: count, registers: ModbusRegisters, regtype: string) {
local quantity = |registers|;
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 transaction = Transaction(
$start_address=start_address,
$quantity=quantity
);
midbro_generate_events(transaction, c, headers, registers, regtype);
}
## EVENT HANDLERS
event bro_init() &priority=5 {
Log::create_stream(Midbro::LOG, [$columns=RegisterData, $path="midbro-parsed"]);
}
event modbus_read_holding_registers_request(c: connection,
headers: ModbusHeaders, start_address: count, quantity: count) {
midbro_handle_read_request(c, headers, start_address, quantity);
}
event modbus_read_holding_registers_response(c: connection,
headers: ModbusHeaders, registers: ModbusRegisters) {
midbro_handle_read_response(c, headers, registers, "h");
}
event modbus_read_input_registers_request(c: connection,
headers: ModbusHeaders, start_address: count, quantity: count) {
midbro_handle_read_request(c, headers, start_address, quantity);
}
event modbus_read_input_registers_response(c: connection,
headers: ModbusHeaders, registers: ModbusRegisters) {
midbro_handle_read_response(c, headers, registers, "i");
}
event modbus_write_multiple_registers_request(c: connection, headers: ModbusHeaders,
start_address: count, registers: ModbusRegisters) {
midbro_handle_write_request(c, headers, start_address, registers, "i");
}
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