syslog-ng Open Source Edition 3.20 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local e-mail messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP collectd: sending metrics to collectd elasticsearch2: Sending logs directly to Elasticsearch and Kibana 2.0 or higher file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka loggly: Using Loggly logmatic: Using Logmatic.io mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (e-mail) from logs Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng: Forwarding messages and tags to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python Client-side failover
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages db-parser: Process message content with a pattern database (patterndb) Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Third-party contributions Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License About us

map-value-pairs: Rename value-pairs to normalize logs

The map-value-pairs() parser allows you to map existing name-value pairs to a different set of name-value pairs. You can rename them in bulk, making it easy to use for log normalization tasks (for example, when you parse information from different log messages, and want to convert them into a uniform naming scheme). You can use the normal value-pairs expressions, similarly to value-pairs based destinations.

Available in syslog-ng OSE version 3.10 and later.

Declaration:
parser parser_name {
    map-value-pairs(
        <list-of-value-pairs-options>
    );
};
Example: Map name-value pairs

The following example creates a new name-value pair called username, adds the hashed value of the .apache.username to this new name-value pair, then adds the webserver prefix to the name of every name-value pair of the message that starts with .apache

parser p_remap_name_values {
    map-value-pairs(
        pair("username", "'($sha1 $.apache.username)")
        key('.apache.*' rekey(add-prefix("webserver")))
    );
};

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Conditional rewrites

Starting with 3.2, it is possible to apply a rewrite rule to a message only if certain conditions are met. The condition() option effectively embeds a filter expression into the rewrite rule: the message is modified only if the message passes the filter. If the condition is not met, the message is passed to the next element of the log path (that is, the element following the rewrite rule in the log statement, for example, the destination). Any filter expression normally used in filters can be used as a rewrite condition. Existing filter statements can be referenced using the filter() function within the condition. For details on filters, see Filters.

TIP:

Using conditions in rewrite rules can simplify your syslog-ng OSE configuration file, as you do not need to create separate log paths to modify certain messages.

How conditional rewriting works

Purpose:

The following procedure summarizes how conditional rewrite rules (rewrite rules that have the condition() parameter set) work. The following configuration snippet is used to illustrate the procedure:

rewrite r_rewrite_set{
    set(
        "myhost",
        value("HOST")
        condition(program("myapplication"))
    );
};
log {
    source(s1);
    rewrite(r_rewrite_set);
    destination(d1);
};
Steps:
  1. The log path receives a message from the source (s1).

  2. The rewrite rule (r_rewrite_set) evaluates the condition. If the message matches the condition (the PROGRAM field of the message is "myapplication"), syslog-ng OSE rewrites the log message (sets the value of the HOST field to "myhost"), otherwise it is not modified.

  3. The next element of the log path processes the message (d1).

Example: Using conditional rewriting

The following example sets the HOST field of the message to myhost only if the message was sent by the myapplication program.

rewrite r_rewrite_set{set("myhost", value("HOST") condition(program("myapplication")));};

The following example is identical to the previous one, except that the condition references an existing filter template.

filter f_rewritefilter {program("myapplication");};
rewrite r_rewrite_set{set("myhost", value("HOST") condition(filter(f_rewritefilter)));};

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Adding and deleting tags

To add or delete a tag, you can use rewrite rules. To add a tag, use the following syntax:

rewrite <name_of_the_rule> {
    set-tag("<tag-to-add>");
};

To delete a tag, use the following syntax:

rewrite <name_of_the_rule> {
    clear-tag("<tag-to-delete>");
};

You cannot use macros in the tags.


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Anonymizing credit card numbers

Log messages of banking and e-commerce applications might include credit card numbers (Primary Account Number or PAN). According to privacy best practices and the requirements of the Payment Card Industry Data Security Standards (PCI-DSS), PAN must be rendered unreadable. The syslog-ng OSE application uses a regular expression to detect credit card numbers, and provides two ways to accomplish this: you can either mask the credit card numbers, or replace them with a hash. To mask the credit card numbers, use the credit-card-mask() or the credit-card-hash() rewrite rules in a log path.

Declaration:
@include "scl/rewrite/cc-mask.conf"

rewrite {
    credit-card-mask(value("<message-field-to-process>"));
};

By default, these rewrite rules process the MESSAGE part of the log message.

credit-card-hash()
Synopsis: credit-card-hash(value("<message-field-to-process>"))

Description: Process the specified message field (by default, ${MESSAGE}), and replace any credit card numbers (Primary Account Number or PAN) with a 16-character-long hash. This hash is generated by calculating the SHA-1 hash of the credit card number, selecting the first 64 bits of this hash, and representing this 64 bits in 16 characters.

credit-card-mask()
Synopsis: credit-card-mask(value("<message-field-to-process>"))

Description: Process the specified message field (by default, ${MESSAGE}), and replace the 7-12th character of any credit card numbers (Primary Account Number or PAN) with asterisks (*). For example, syslog-ng OSE replaces the number 5542043004559005 with 554204******9005.


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