---
title: laurel
section: 8
header: System Administration Utilities
footer: laurel 0.8.1
---

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

<!-- `user` and `directory` are unset by default for debugging -->

## `[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`.

  `-` causes `laurel` to write its log to standard output.

  A string beginning with a pipe (e.g. `| /path/to/program`) causes
  `laurel` to spawn an external program and write its log to that
  program's standard input.

  A string beginning with `unix:` (e.g. `unix:/path/to/socket`)
  causes `laurel` to connect and write its log to a UNIX domain
  socket. On I/O errors, reconnection attempts will be made.
- `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-groups`: 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. Prefix matches are used for strings ending with an asterisk
  (`*`). 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
- `ppid-verbose`: As part of the `SYSCALL.PPID.*` enrichment, the first
  event ID referring to the parent process or its start time is
  logged. If this option is set, the `comm`, `exe`, and `ppid` fields
  are added. Deprecated, see `spawned-by`. Default: false
- `spawned-by`: Add `SYSCALL.SPAWNED_BY.*` enrichments that contains
  information about the process responsible for spawning the current
  process. This is a replacement for the `SYSCALL.PPID` enrichment.
  For a more detailed discussion, see section "Adding Context: Process
  Relationships, Labels" in `laurel-about(7)`. 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 consumed 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
- `exe-hash`: Compute SHA256 hash of the executable (`SYSCALL.exe`)
  and add it as `EXE_HASH` to the SYSCALL record. Default: false
- `exe-hash-size-limit`: Skip hashing executables larger than this size
  (in bytes). Recommended to avoid excessive I/O on large binaries.
  Default: 10_000_000
- `exe-hash-cache-entries`: Maximum number of entries in the exe hash
  LRU cache (keyed by inode + mtime). Set to 0 to disable caching.
  Default: 1024

## `[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-sockaddr`: Filter events that contain SOCKADDR entries
  matching CIDR and/or ports. IPv4 and IPv6 addresses with optional
  bitmask and port numbers or plain port numbers can be specified. Examples:
   - `127.0.0.1`
   - `192.168.0.0/24:22`
   - `::/64`
   - `[2a00:1450:4001:82f::200e]:443`
   - `*:111`
  Default: empty list
- `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.

# SEE ALSO
`auditd(8)`, `auditd-plugins(5)`, `audit.rules(7)`, `laurel-about(7)`, `laurel-audit-rules(7)`

# AUTHORS
- Hilko Bengen <<bengen@hilluzination.de>>
- Sergej Schmidt <<sergej@msgpeek.net>>
