syslog-ng Open Source Edition 3.25 - Administration Guide

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type:	string
Default:	N/A
Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type:	string
Default:	N/A
Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type:	string
Default:	N/A
Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type:	string
Default:	N/A
Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

osquery: Collect and parse osquery result logs

source: Read, receive, and collect log messages > osquery: Collect and parse osquery result logs

The osquery application allows you to ask questions about your machine using an SQL-like language. For example, you can query running processes, logged in users, installed packages and syslog messages as well. You can make queries on demand, and also schedule them to run regularly.

The osquery() source of syslog-ng OSE allows you read the results of periodical osquery queries (from the /var/log/osquery/osqueryd.results.log file) and automatically parse the messages (if you want to use syslog-ng OSE to send log messages to osquery, read this blogpost). For example, you can:

Create filters from the fields of the messages.
Limit which fields to store, or create additional fields (combine multiple fields into one field, and so on).
Send the messages to a central location, for example, to Elasticsearch, directly from syslog-ng OSE.

The syslog-ng OSE application automatically adds the .osquery. prefix to the name of the fields the extracted from the message.

The osquery() source is available in syslog-ng OSE version 3.10 and later.

Prerequisites:

To use the osquery() driver, the scl.conf file must be included in your syslog-ng OSE configuration:
```
@include "scl.conf"
```
syslog-ng OSE must be compiled with JSON-support enabled.

The osquery() driver is actually a reusable configuration snippet configured to read the osquery log file using the file() driver, and process its JSON contents. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of this configuration snippet on GitHub.

Example: Using the osquery() driver with the default settings

The following syslog-ng OSE configuration sample uses the default settings of the driver, reading osquery result logs from the /var/log/osquery/osqueryd.results.log file, and writes the log messages generated from the traps into a file.

@version: 3.10
@include "scl.conf"
source s_osquery {
    osquery();
};
log {
    source(s_osquery);
    destination {
        file("/var/log/example.log");
    };
};

Filter for messages related to loading Linux kernel modules:

@version: 3.10
@include "scl.conf"
source s_osquery {
    osquery();
};
log {
    source(s_osquery);
    filter f_modules {
        "${.osquery.name}" eq "pack_incident-response_kernel_modules"
    };
    destination {
        file("/var/log/example.log");
    };
};

Example: Using the osquery() driver with custom configuration

The following syslog-ng OSE configuration sample reads osquery result logs from the /tmp/osquery_input.log file, and writes the log messages generated from the traps into a file. Using the format-json template, the outgoing message will be a well-formed JSON message.

Input message:

{"name":"pack_osquery-monitoring_osquery_info","hostIdentifier":"testhost","calendarTime":"Fri Jul 21 10:04:41 2017 UTC","unixTime":"1500631481","decorations":{"host_uuid":"4C4C4544-004D-3610-8043-C2C04F4D3332","username":"myuser"},"columns":{"build_distro":"xenial","build_platform":"ubuntu","config_hash":"43cd1c6a7d0c283e21e026a53e619b2e582e94ee","config_valid":"1","counter":"4","extensions":"active","instance_id":"d0c3eb0d-f8e0-4bea-868b-18a2c61b438d","pid":"19764","resident_size":"26416000","start_time":"1500629552","system_time":"223","user_time":"476","uuid":"4C4C4544-004D-3610-8043-C2C04F4D3332","version":"2.5.0","watcher":"19762"},"action":"added"}

syslog-ng OSE configuration:

@version: 3.10
@include "scl.conf"
source s_osquery {
    osquery(
      file(/tmp/osquery_input.log)
      prefix(.osquery.)
    );
};
destination d_file {
    file(
      "/tmp/output.txt"
      template("$(format_json --key .osquery.*)\n")
    );
};
log {
  source(s_osquery);
  destination(d_file);
  flags(flow-control);
};

Outgoing message:

Outgoing message; message='{"_osquery":{"unixTime":"1500631481","name":"pack_osquery-monitoring_osquery_info","hostIdentifier":"testhost","decorations":{"username":"myuser","host_uuid":"4C4C4544-004D-3610-8043-C2C04F4D3332"},"columns":{"watcher":"19762","version":"2.5.0","uuid":"4C4C4544-004D-3610-8043-C2C04F4D3332","user_time":"476","system_time":"223","start_time":"1500629552","resident_size":"26416000","pid":"19764","instance_id":"d0c3eb0d-f8e0-4bea-868b-18a2c61b438d","extensions":"active","counter":"4","config_valid":"1","config_hash":"43cd1c6a7d0c283e21e026a53e619b2e582e94ee","build_platform":"ubuntu","build_distro":"xenial"},"calendarTime":"Fri Jul 21 10:04:41 2017 UTC","action":"added"}}\x0a'

To configure a destination to send the log messages to Elasticsearch, see elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED). For other destinations, see destination: Forward, send, and store log messages.

osquery() source options

source: Read, receive, and collect log messages > osquery: Collect and parse osquery result logs > osquery() source options

The osquery() driver has the following options.

file()

Type:	path
Default:	/var/log/osquery/osqueryd.results.log

Description: The log file of osquery that stores the results of periodic queries. The syslog-ng OSE application reads the messages from this file.

hook-commands()

Using the hook-commands() when syslog-ng OSE starts or stops

To execute an external program when syslog-ng OSE starts or stops, use the following options:

startup()
Type:	string
Default:	N/A
Description: Defines the external program that is executed as syslog-ng OSE starts.

shutdown()
Type:	string
Default:	N/A
Description: Defines the external program that is executed as syslog-ng OSE stops.

Using the hook-commands() when syslog-ng OSE reloads

To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:

setup()
Type:	string
Default:	N/A
Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload.

teardown()
Type:	string
Default:	N/A
Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.

source {
   network(transport(udp)
	hook-commands(
          startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
          shutdown("iptables -D LOGCHAIN 1")
        )
     );
};

prefix()

Synopsis:

prefix()

Description: Insert a prefix before the name part of the parsed name-value pairs to help further processing. For example:

To insert the my-parsed-data. prefix, use the prefix(my-parsed-data.) option.
To refer to a particular data that has a prefix, use the prefix in the name of the macro, for example, ${my-parsed-data.name}.
If you forward the parsed messages using the IETF-syslog protocol, you can insert all the parsed data into the SDATA part of the message using the prefix(.SDATA.my-parsed-data.) option.

Names starting with a dot (for example, .example) are reserved for use by syslog-ng OSE. If you use such a macro name as the name of a parsed value, it will attempt to replace the original value of the macro (note that only soft macros can be overwritten, see Hard versus soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example, prefix(my-parsed-data.)

Default value:

.osquery. option.

pipe: Collecting messages from named pipes

source: Read, receive, and collect log messages > pipe: Collecting messages from named pipes

The pipe driver opens a named pipe with the specified name and listens for messages. It is used as the native message delivery protocol on HP-UX.

The pipe driver has a single required parameter, specifying the filename of the pipe to open. For the list of available optional parameters, see pipe() source options.

Declaration:

pipe(filename);

NOTE:

As of syslog-ng Open Source Edition 3.0.2, pipes are created automatically. In earlier versions, you had to create the pipe using the mkfifo(1) command.

Pipe is very similar to the file() driver, but there are a few differences, for example, pipe() opens its argument in read-write mode, therefore it is not recommended to be used on special files like /proc/kmsg.

Caution:

It is not recommended to use pipe() on anything else than real pipes.
By default, syslog-ng OSE uses the flags(no-hostname) option for pipes, meaning that syslog-ng OSE assumes that the log messages received from the pipe do not contain the hostname field. If your messages do contain the hostname field, use flags(expect-hostname). For details, see flags().

Example: Using the pipe() driver

source s_pipe {
    pipe("/dev/pipe" pad-size(2048));
};

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syslog-ng Open Source Edition 3.25 - Administration Guide

mbox() source options

hook-commands()

Using the hook-commands() when syslog-ng OSE starts or stops

Using the hook-commands() when syslog-ng OSE reloads

Example: Using the hook-commands() with a network source

osquery: Collect and parse osquery result logs

Prerequisites:

Example: Using the osquery() driver with the default settings

Example: Using the osquery() driver with custom configuration

Input message:

syslog-ng OSE configuration:

Outgoing message:

osquery() source options

file()

hook-commands()

Using the hook-commands() when syslog-ng OSE starts or stops

Using the hook-commands() when syslog-ng OSE reloads

Example: Using the hook-commands() with a network source

prefix()

Default value:

pipe: Collecting messages from named pipes

Declaration:

Example: Using the pipe() driver