syslog-ng Open Source Edition 3.22 - Administration Guide

Linux audit parser

The Linux audit parser can parse the log messages of the Linux Audit subsystem (auditd). The syslog-ng OSE application can separate these log messages to name-value pairs. For details on using value-pairs in syslog-ng OSE see Structuring macros, metadata, and other value-pairs. The following is a sample log message of auditd:

type=SYSCALL msg=audit(1441988805.991:239): arch=c000003e syscall=59 success=yes exit=0 a0=7fe49a6d0e98 a1=7fe49a6d0e40 a2=7fe49a6d0e80 a3=2 items=2 ppid=3652 pid=3660 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=5 comm="dumpe2fs" exe="/sbin/dumpe2fs" key=(null)
type=EXECVE msg=audit(1441988805.991:239): argc=3 a0="dumpe2fs" a1="-h" a2="/dev/sda1"
type=CWD msg=audit(1441988805.991:239):  cwd="/"
type=PATH msg=audit(1441988805.991:239): item=0 name="/sbin/dumpe2fs" inode=137078 dev=08:01 mode=0100755 ouid=0 ogid=0 rdev=00:00 nametype=NORMAL
type=PATH msg=audit(1441988805.991:239): item=1 name="/lib64/ld-linux-x86-64.so.2" inode=5243184 dev=08:01 mode=0100755 ouid=0 ogid=0 rdev=00:00 nametype=NORMAL
type=PROCTITLE msg=audit(1441988805.991:239): proctitle=64756D7065326673002D68002F6465762F73646131

Certain fields of the audit log can be encoded in hexadecimal format, for example, the arch field, or the a<number> fields in the previous example. The syslog-ng OSE application automatically decodes these fields (for example, the c000003e value becomes x86_64).

The syslog-ng OSE application extracts every field into name-value pairs. It automatically decodes the following fields:

• name

• proctitle

• path

• dir

• comm

• ocomm

• data

• old

• new

To parse the log messages of the Linux Audit subsystem, define a parser that has the linux-audit-parser() option. By default, the parser will process the ${MESSAGE} part of the log message. To process other parts of a log message, use the template() option. You can also define the parser inline in the log path.

parser parser_name {
    linux-audit-parser(
        prefix()
        template()
    );
};

source s_auditd {
    file(/var/log/audit/audit.log flags(no-parse));
};

destination d_json {
    file(
        "/tmp/test.json"
        template("$(format-json .auditd.*)\n")
    );
};

parser p_auditd {
    linux-audit-parser (prefix(".auditd."));
};

log {
    source(s_auditd);
    parser(p_auditd);
    destination(d_json);
};

source s_auditd {
    file(/var/log/audit/audit.log);
};

destination d_json {
    file(
        "/tmp/test.json"
        template("$(format-json .auditd.*)\n")
    );
};

log {
    source(s_auditd);
    parser {
        linux-audit-parser (prefix(".auditd."));
    };
    destination(d_json);
};

Options of linux-audit-parser() parsers

The linux-audit-parser() has the following options.

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 vs. soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example, prefix(my-parsed-data.)

template()

Description: The macro that contains the part of the message that the parser will process. It can also be a macro created by a previous parser of the log path. By default, the parser processes the entire message (${MESSAGE}).

Cisco parser

The Cisco parser can parse the log messages of various Cisco devices. The messages of these devices often do not completely comply with the syslog RFCs, making them difficult to parse. The cisco-parser() of syslog-ng OSE solves this problem, and can separate these log messages to name-value pairs, extracting also the Cisco-specific values, for example, the mnemonic. For details on using value-pairs in syslog-ng OSE see Structuring macros, metadata, and other value-pairs. The parser can parse variations of the following message format:

<pri>(sequence: )?(origin-id: )?(timestamp? timezone?: )?%msg

For example:

<189>29: foo: *Apr 29 13:58:40.411: %SYS-5-CONFIG_I: Configured from console by console
<190>30: foo: *Apr 29 13:58:46.411: %SYS-6-LOGGINGHOST_STARTSTOP: Logging to host 192.168.1.239 stopped - CLI initiated
<190>31: foo: *Apr 29 13:58:46.411: %SYS-6-LOGGINGHOST_STARTSTOP: Logging to host 192.168.1.239 started - CLI initiated
<189>32: 0.0.0.0: *Apr 29 13:59:12.491: %SYS-5-CONFIG_I: Configured from console by console
<189>32: foo: *Apr 29 13:58:46.411: %SYSMGR-STANDBY-3-SHUTDOWN_START: The System Manager has started the shutdown procedure.

Note that not every Cisco log message conforms to this format. If you find a message that the cisco-parser() cannot properly parse, open a GitHub issue so we can improve the parser.

The syslog-ng OSE application normalizes the parsed log messages into the following format:

${MESSAGE}=%FAC-SEV-MNEMONIC: message
${HOST}=origin-id

By default, the Cisco-specific fields are extracted into the following name-value pairs:${.cisco.facility}, ${.cisco.severity}, ${.cisco.mnemonic}. You can change the prefix using the prefix option.

@version: 3.22
@include "scl.conf"
log {
    source { udp(flags(no-parse)); };
    parser { cisco-parser(); };
    destination { ... };
};

Note that you have to disable message parsing in the source using the flags(no-parse) option for the parser to work.

The cisco-parser() is actually a reusable configuration snippet configured to parse Cisco messages. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of this configuration snippet on GitHub.

parser {
    cisco-parser(prefix("myprefix."));
};

Parsing enterprise-wide message model (EWMM) messages

The ewmm-parser() can be used to parse messages sent by another syslog-ng host using the enterprise-wide message model (EWMM) format. Available in version 3.16 and later. Note that usually you do not have to use this parser directly, because the default-network-drivers() source automatically parses such messages.

parser parser_name {
    ewmm-parser();
};