--- name: "laurel" section: "8" platform: "linux" package: "laurel" version: "0.7.1-1+b2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/laurel" --- # laurel(8) transform, enrich Linux audit logs ## NAME [laurel(8)](/laurel/8.md) – 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. = `: Regular expressions/label mappings applied to binary executables (`SYSCALL.exe`) on `execve` calls. Default: none - • `label-argv. = `: Regular expressions/label mappings applied to the command line (`EXECVE.a*`) on `execve` calls. Default: none - • `label-script. = `: 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. = `: Like `label-exe`, but for removing labels - • `unlabel-argv. = `: Like `label-argv`, but for removing labels - • `unlabel-script. = `: 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. ## SEE ALSO `auditd(8)`, `auditd-plugins(5)`, `audit.rules(7)`, `laurel-about(7)`, `laurel-audit-rules(7)` ## AUTHORS - • Hilko Bengen \<⟨bengen@hilluzination.de⟩\\c \> - • Sergej Schmidt \<⟨sergej@msgpeek.net⟩\\c \>