omdtls: Output Module for DTLS Protocol over UDP
Module Name: | omdtls |
Author: | Andre Lorbach <alorbach@adiscon.com> |
Available since: | v8.2402.0 |
Purpose
The omdtls module for rsyslog is designed to securely transmit syslog data over a network using the Datagram Transport Layer Security (DTLS) protocol. This module leverages the robustness and security features of OpenSSL to provide an encrypted transport mechanism for syslog messages via UDP.
DTLS, being an adaptation of TLS for datagram-based protocols, offers integrity, authenticity, and confidentiality for messages in transit. The omdtls module is particularly useful in environments where secure transmission of log data is crucial, such as in compliance-driven industries or when transmitting across untrusted networks.
By operating over UDP, omdtls offers the benefits of lower latency and reduced protocol overhead compared to TCP-based transport, making it well-suited for high-throughput logging scenarios or in networks where connection-oriented protocols may face challenges.
Requirements
To send messages by DTLS you will need to fulfill the following requirements:
OpenSSL 1.0.2 or Higher
Configuration Parameters
Note
Parameter names are case-insensitive.
Module Parameters
Template
type | default | mandatory |
|
|---|---|---|---|
word | RSYSLOG_TraditionalForwardFormat | no |
|
Sets a non-standard default template for this module.
Action Parameters
target
type | default | mandatory |
|
|---|---|---|---|
word | none | no | none |
Specifies the target hostname or IP address to send log messages to.
port
type | default | mandatory |
|
|---|---|---|---|
word | 4433 | yes | none |
Defines the port number on the target host where log messages will be sent. The default port number for DTLS is 4433.
tls.AuthMode
type | default | mandatory |
|
|---|---|---|---|
string | none | no | none |
Sets the mode of authentication to be used. Supported values are either “fingerprint“, “name” or “certvalid“.
Fingerprint: Authentication based on certificate fingerprint. Name: Authentication based on the subjectAltName and, as a fallback, the subject common name. Certvalid: Requires a valid certificate for authentication. Certanon: Anything else will allow anonymous authentication (no client certificate).
tls.cacert
type | default | mandatory |
|
|---|---|---|---|
string | none | no | none |
The CA certificate that is being used to verify the client certificates. Has to be configured if tls.authmode is set to “fingerprint“, “name” or “certvalid“.
tls.mycert
type | default | mandatory |
|
|---|---|---|---|
string | none | no | none |
Specifies the certificate file used by omdtls. This certificate is presented to peers during the DTLS handshake.
tls.myprivkey
type | default | mandatory |
|
|---|---|---|---|
string | none | no | none |
The private key file corresponding to tls.mycert. This key is used for the cryptographic operations in the DTLS handshake.
tls.tlscfgcmd
type | default | mandatory |
|
|---|---|---|---|
string | none | no | none |
Used to pass additional OpenSSL configuration commands. This can be used to fine-tune the OpenSSL settings by passing configuration commands to the openssl libray. OpenSSL Version 1.0.2 or higher is required for this feature. A list of possible commands and their valid values can be found in the documentation: https://www.openssl.org/docs/man1.0.2/man3/SSL_CONF_cmd.html
The setting can be single or multiline, each configuration command is separated by linefeed (n). Command and value are separated by equal sign (=). Here are a few samples:
Example 1
This will allow all protocols except for SSLv2 and SSLv3:
tls.tlscfgcmd="Protocol=ALL,-SSLv2,-SSLv3"
Example 2
This will allow all protocols except for SSLv2, SSLv3 and TLSv1. It will also set the minimum protocol to TLSv1.2
tls.tlscfgcmd="Protocol=ALL,-SSLv2,-SSLv3,-TLSv1
MinProtocol=TLSv1.2"
Template
type | default | mandatory |
|
|---|---|---|---|
word | RSYSLOG_TraditionalForwardFormat | no |
Sets a non-standard default template for this action instance.
Statistic Counter
This plugin maintains global statistics for omdtls that accumulate all action instances. The statistic origin is named “omdtls” with following counters:
submitted - This counter tracks the number of log messages that have been successfully send by the current output instance.
failures - This counter tracks the number of log messages that have been failed to send to the target server.
These statistics counters are updated in real-time by the rsyslog output module as log data is processed, and they provide valuable information about the performance and operation of the input module.
For multiple actions using statistics callback, there will be one record for each action.
Examples
Example 1: Basic
The following sample does the following: - loads the omdtls module - Sends all syslog messages to 192.168.2.1 by DTLS on port 4433.
module(load="omdtls")
action(type="omdtls" name="omdtls" target="192.168.2.1" port="4433")
Example 2: Message throttling
The following sample does the following:
loads the omdtls module
Sends all syslog messages to 192.168.2.1 by DTLS on port 4433.
Slows down sending to avoid package loss due the nature of UDP. In this sample, using dequeueSlowDown 1000 will limit the messages per second to 1000.
module(load="omdtls")
action(type="omdtls"
name="omdtls"
target="192.168.2.1"
port="4433"
queue.type="FixedArray"
queue.size="100000"
queue.dequeueBatchSize="1"
queue.minDequeueBatchSize.timeout="1000"
queue.timeoutWorkerthreadShutdown="1000"
queue.timeoutshutdown="1000"
queue.dequeueSlowDown="1000"
)
See also
Help with configuring/using Rsyslog:
Mailing list - best route for general questions
GitHub: rsyslog source project - detailed questions, reporting issues that are believed to be bugs with
Rsyslog
See also
Contributing to Rsyslog:
Source project: rsyslog project README.
Documentation: rsyslog-doc project README
Copyright 2008-2023 Rainer Gerhards (Großrinderfeld), and Others.