Ubuntu Manpage: laurel(8) – transform, enrich Linux audit logs

NAME

       laurel(8) – transform, enrich Linux audit logs

SYNOPSIS

       laurel  is an auditd(8) plug-in that parses Linux audit events, enriches them with local information, and
       transforms them into a JSON Lines-based output format intended for consumption by log processing and SIEM
       software.

OPTIONS

       -c FILE, --config=FILE
              path to configuration file (default: unset)

       -d, --dry-run
              Only parse configuration and exit

       -h, --help
              Print short help text and exit

       -v, --version
              Print version and exit

DESCRIPTION

       laurel is typically configured to be spawned by  auditd(8)  itself  or  by  audispd(8)  (for  2.x  auditd
       versions).  All audit events are fed to laurel via its standard input channel.

       Sample configuration file /etc/audit/plugins.d/laurel.conf:

              active = yes
              direction = out
              type = always
              format = string
              path = /usr/sbin/laurel
              args = --config /etc/laurel/config.toml

       An  alternative  setup  consists  of an AF_UNIX socket to which auditd(8) writes events.  A connection is
       then established by laurel (see input setting below).  In this case,  the  operator  is  responsible  for
       starting and restarting laurel.

       Example configuration file:

              active = yes
              direction = out
              path = builtin_af_unix
              type = builtin
              args = 0600 /var/run/laurel.sock
              format = string

CONFIGURATION

Configuration of laurel itself is done through a single configuration file in TOML format.

main section
This section contains basic operation parameters.

• user: laurel is started as root by auditd, but it drops to a dedicated user as soon as possible.
Default: unset

• directory: The base directory into which all files are written. Default: . (current directory)

• statusreport-period: How often stats are written to Syslog, in seconds. Default: unset

• input: laurel can consume audit events from standard input or connect to a listening socket specified
as unix:/path/to/socket at start. Defaulkt: stdin

• marker: A string that is written to the log on startup and whenever laurel writes a status report.
Default: none

[auditlog] section
This section describes the main audit log file. laurel performs its own log file rotation, just like
auditd(8).

• file: Filename for the audit log file. Default: audit.log

• size: Size in bytes after which the log file is rotated. Default: 10MiB

• generations: Number of generations to keep after rotation. Default: 5

• read-users: List of users that are granted read access to the log file using POSIX ACLs. Default:
empty

• read-group: List of groups that are granted read access to the log file using POSIX ACLs. Default:
empty

• read-other: Whether all users are granted read access to the log file. Default: false

• line-prefix: A string that is prepended to every line. Default: unset

[filterlog] section
This section describes the log file for filtered-out log events (see below). The file, size,
generations, read-users, line-prefix configuration items work just like for the audit log.

[state] section
This section describes the state file. laurel uses this file on restart to keep track of running
processes. The state file contains snapshots of the user database cache, process list, currently used
events and a list of event ids that have already been processed.

• file: Filename for the state file. Set to empty string to disable keeping state on disk. Default:
state

• generations: Number of generations of the state file to keep for debugging purposes. Default: 0; it
should only be increased for debugging purposes.

• max-age: Number of seconds after which the state file is considered stale. Default: 60

• write-state-period: How often the state file is written to the filesystem, in seconds. Default: unset

[transform] section
• execve-argv: The list of EXECVE.a* fields are transformed to an ARGV list or ARGV_STR string. Set to
array, string (or both). Default: array

• execve-argv-limit-bytes: Arguments are cut out of the middle long argument lists in EXECVE.ARGV or
EXECVE.ARGV_STR so that this limit is not exceeded. Default: unset

[translate] section
Options that can be configured here correspond to what auditd(8) does when configured with
log_format=ENRICHED.

• userdb: Add translations for uid and gid fields. Default: false

• universal: Add translations for everything else: SYSCALL.arch, SYSCALL.syscall, SOCKADDR.saddr

• drop-raw: Drop raw (numeric) syscall, arch, UID, GID values if they are translated. Default: false

[enrich] section
Options that can be configured here actually add information to events

• execve-env: A list of environment variables to dump for exec events. Default: ["LD_PRELOAD",
"LD_LIBRARY_PATH"]

• container: Add container information for processes running within container runtimes as
SYSCALL.PID.container. Default: true

• systemd: Add systemd cgroup information for processes running within systemd services as
SYSCALL.PID.systemd_service. Default: true

• container_info: Add container information as top-level CONTAINER_INFO key. Deprecated; default: false

• pid: Add context information for process IDs. Default: true

• script: If an exec syscall spawns a script (as opposed to a binary), add a SCRIPT entry to the SYSCALL
record. A script is assumed if the first PATH entry does not correspond to file mentioned in
SYSCALL.exe. Default: true

• user-groups: Add groups that the user (“uid”) is a member of. Default: true

• prefix: Add a prefix to enriched fields; this may be useful if logs are onsumed by analysis software
that doesn’t properly understand uppercase and lowercase JSON object fields as identical. This setting
does not affect enriched fields passed in from auditd(8). Default: unset

[label-process] section
Labels can be attached to processes and are added to any event associated with those processes. These
labels can be propagated from parent to child processes.

• label-exe.<regexp> = <label-name>: Regular expressions/label mappings applied to binary executables
(SYSCALL.exe) on execve calls. Default: none

• label-argv.<regexp> = <label-name>: Regular expressions/label mappings applied to the command line
(EXECVE.a*) on execve calls. Default: none

• label-script.<regexp> = <label-name>: Regular expressions/label mappings applied to scripts
(SYSCALL.SCRIPT, see enrich.script description above) on exec calls. Default: none

• label-keys: A list of keys that are applied as a process label, see auditctl(8)’s -k option. Default:
none

• unlabel-exe.<regexp> = <label-name>: Like label-exe, but for removing labels

• unlabel-argv.<regexp> = <label-name>: Like label-argv, but for removing labels

• unlabel-script.<regexp> = <label-name>: Like label-script, but for removing labels

• label-argv-count Number of command line arguments that are considered for label-argv, unlabel-argv.
Default: 32

• label-argv-bytes Number of bytes that are considered for label-argv, unlabel-argv. Default: 4096

• propagate-labels: List of labels that are propagated to child processes. Default: empty

[filter] section
Filters make laurel drop entire events from the log file while still using them for internal processing
such as process tracking.

• filter-keys: A list of strings that are matched against SYSCALL.key to drop the event. Default: empty

• filter-null-keys: Filter events without specified key. Default: false

• filter-labels: A list of strings that are matched against process labels. Default: empty

• filter-raw-lines: A list of regular expression that are matched against individual input lines as
written by auditd(8). Events that contain such lines are then filtered. Default: empty

• filter-action: What to do with filtered events? drop or log to the filterlog defined above.

• keep-first-per-process: Keep the first event observed for any given process even if it would be
filtered otherwise. This should only be turned off if reproducible process tracking or process tree
reconstruction is not required. Default: true

SIGNALS

       SIGHUP  causes  laurel  to  process any buffered input and restart.  It can be used to reconfigure laurel
       without having restarting auditd(8) which would likely lead to lost audit messages.

AUTHORS

       • Hilko Bengen <bengen@hilluzination.de>

       • Sergej Schmidt <sergej@msgpeek.net>

laurel 0.7.1                                                                                           laurel(8)