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Add a field to Modbus/TCP log to indicate the Modbus PDU type

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Add the `pdu_type` field to Modbus over TCP logs to indicate whether the Modbus
message was a request or a response. Due to the client/server nature of Modbus
over TCP/IP, all messages from the TCP session originator are requests, while
all messages from the TCP session responder are responses.

Adding this information to the default log surfaces protocol metadata in a way
that doesn't require users to understand the Modbus over TCP protocol.
This commit is contained in:
Michael Torres 2022-07-17 21:18:50 +00:00
parent bab2036aa4
commit b85801aa7e
4 changed files with 40000 additions and 39995 deletions
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5
scripts/base/protocols/modbus/main.zeek
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@ -22,6 +22,8 @@ export {
unit: count &log &optional;
## The name of the function message that was sent.
func: string &log &optional;
## Whether this PDU was a response ("RESP") or request ("REQ")
pdu_type: string &log &optional;
## The exception if the response was a failure.
exception: string &log &optional;
};
@ -55,6 +57,9 @@ event modbus_message(c: connection, headers: ModbusHeaders, is_orig: bool) &prio
c$modbus$tid = headers$tid;
c$modbus$unit = headers$uid;
c$modbus$func = function_codes[headers$function_code];
## If this message is from the TCP originator, it is a request. Otherwise,
## it is a response.
c$modbus$pdu_type = is_orig ? "REQ" : "RESP";
}
event modbus_message(c: connection, headers: ModbusHeaders, is_orig: bool) &priority=-5