21. Interacting via Unix Socket

21.1. Introduction

Suricata can listen to a unix socket and accept commands from the user. The exchange protocol is JSON-based and the format of the message is generic.

An example script called suricatasc is provided in the source and installed automatically when installing/updating Suricata.

The unix socket is always enabled by default.

You'll need to have JSON support in Python:

  • python-simplejson - simple, fast, extensible JSON encoder/decoder for Python


apt-get install python-simplejson

The creation of the socket is managed by setting enabled to 'yes' or 'auto' under unix-command in Suricata YAML configuration file:

  enabled: yes
  #filename: custom.socket # use this to specify an alternate file

The filename variable can be used to set an alternate socket filename. The filename is always relative to the local state base directory.

Clients are implemented for some programming languages and can be used as code example to write custom scripts:

21.2. Commands in standard running mode

You may need to install suricatasc if you have not done so, running the following command from python/suricatasc

sudo python setup.py install

The set of existing commands is the following:

  • command-list: list available commands

  • shutdown: shutdown Suricata

  • iface-list: list interfaces where Suricata is sniffing packets

  • iface-stat: list statistics for an interface

  • help: alias of command-list

  • version: display Suricata's version

  • uptime: display Suricata's uptime

  • running-mode: display running mode (workers, autofp, simple)

  • capture-mode: display capture system used

  • conf-get: get configuration item (see example below)

  • dump-counters: dump Suricata's performance counters

  • reopen-log-files: reopen log files (to be run after external log rotation)

  • ruleset-reload-rules: reload ruleset and wait for completion

  • ruleset-reload-nonblocking: reload ruleset and proceed without waiting

  • ruleset-reload-time: return time of last reload

  • ruleset-stats: display the number of rules loaded and failed

  • ruleset-failed-rules: display the list of failed rules

  • memcap-set: update memcap value of the specified item

  • memcap-show: show memcap value of the specified item

  • memcap-list: list all memcap values available

  • reload-rules: alias of ruleset-reload-rules

  • register-tenant-handler: register a tenant handler with the specified mapping

  • unregister-tenant-handler: unregister a tenant handler with the specified mapping

  • register-tenant: register tenant with a particular ID and filename

  • unregister-tenant: unregister tenant with a particular ID

  • reload-tenant: reload a tenant with specified ID and filename

  • add-hostbit: add hostbit on a host IP with a particular bit name and time of expiry

  • remove-hostbit: remove hostbit on a host IP with specified bit name

  • list-hostbit: list hostbit for a particular host IP

You can access these commands with the provided example suricatasc script. A typical session with suricatasc looks like:

# suricatasc
Command list: shutdown, command-list, help, version, uptime, running-mode, capture-mode, conf-get, dump-counters, iface-stat, iface-list, quit
>>> iface-list
Success: {'count': 2, 'ifaces': ['eth0', 'eth1']}
>>> iface-stat eth0
Success: {'pkts': 378, 'drop': 0, 'invalid-checksums': 0}
>>> conf-get unix-command.enabled

21.3. Commands on the cmd prompt

You can use suricatasc directly on the command prompt:

root@debian64:~# suricatasc -c version
{'message': '5.0.3 RELEASE', 'return': 'OK'}
root@debian64:~# suricatasc -c uptime
{'message': 35264, 'return': 'OK'}

NOTE: You need to quote commands with more than one argument:

root@debian64:~# suricatasc -c "iface-stat eth0"
{'message': {'pkts': 5110429, 'drop': 0, 'invalid-checksums': 0}, 'return': 'OK'}

21.4. PCAP processing mode

This mode is one of main motivations behind this code. The idea is to be able to provide different pcap files to Suricata without having to restart Suricata for each file. This saves time since you don't need to wait for the signature engine to initialize.

To use this mode, start Suricata with your preferred configuration YAML file and provide the option --unix-socket as argument:

suricata -c /etc/suricata-full-sigs.yaml --unix-socket

It is also possible to specify the socket filename as an argument:

suricata --unix-socket=custom.socket

In this last case, you will need to provide the complete path to the socket to suricatasc. To do so, you need to pass the filename as first argument of suricatasc:

suricatasc custom.socket

Once Suricata is started, you can use suricatasc to connect to the command socket and provide different pcap files:

root@tiger:~# suricatasc
>>> pcap-file /home/benches/file1.pcap /tmp/file1
Success: Successfully added file to list
>>> pcap-file /home/benches/file2.pcap /tmp/file2
Success: Successfully added file to list
>>> pcap-file-continuous /home/pcaps /tmp/dirout
Success: Successfully added file to list

You can add multiple files without waiting for each to be processed; they will be sequentially processed and the generated log/alert files will be put into the directory specified as second argument of the pcap-file command. You need to provide an absolute path to the files and directory as Suricata doesn't know from where the script has been run. If you pass a directory instead of a file, all files in the directory will be processed. If using pcap-file-continuous and passing in a directory, the directory will be monitored for new files being added until you use pcap-interrupt or delete/move the directory.

To display how many files are waiting to get processed, you can do:

>>> pcap-file-number
Success: 3

To display the list of queued files, do:

>>> pcap-file-list
Success: {'count': 2, 'files': ['/home/benches/file1.pcap', '/home/benches/file2.pcap']}

To display current processed file:

>>> pcap-current

When passing in a directory, you can see last processed time (modified time of last file) in milliseconds since epoch:

>>> pcap-last-processed

To interrupt directory processing which terminates the current state:

>>> pcap-interrupt

21.5. Build your own client

The protocol is documented in the following page https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Unix_Socket#Protocol

The following session show what is sent (SND) and received (RCV) by the server. Initial negotiation is the following:

# suricatasc
SND: {"version": "0.1"}
RCV: {"return": "OK"}

Once this is done, commands can be issued:

>>> iface-list
SND: {"command": "iface-list"}
RCV: {"message": {"count": 1, "ifaces": ["wlan0"]}, "return": "OK"}
Success: {'count': 1, 'ifaces': ['wlan0']}
>>> iface-stat wlan0
SND: {"command": "iface-stat", "arguments": {"iface": "wlan0"}}
RCV: {"message": {"pkts": 41508, "drop": 0, "invalid-checksums": 0}, "return": "OK"}
Success: {'pkts': 41508, 'drop': 0, 'invalid-checksums': 0}

In pcap-file mode, this gives:

>>> pcap-file /home/eric/git/oisf/benches/sandnet.pcap /tmp/bench
SND: {"command": "pcap-file", "arguments": {"output-dir": "/tmp/bench", "filename": "/home/eric/git/oisf/benches/sandnet.pcap"}}
RCV: {"message": "Successfully added file to list", "return": "OK"}
Success: Successfully added file to list
>>> pcap-file-number
SND: {"command": "pcap-file-number"}
RCV: {"message": 1, "return": "OK"}
>>> pcap-file-list
SND: {"command": "pcap-file-list"}
RCV: {"message": {"count": 1, "files": ["/home/eric/git/oisf/benches/sandnet.pcap"]}, "return": "OK"}
Success: {'count': 1, 'files': ['/home/eric/git/oisf/benches/sandnet.pcap']}
>>> pcap-file-continuous /home/eric/git/oisf/benches /tmp/bench 0 true
SND: {"command": "pcap-file", "arguments": {"output-dir": "/tmp/bench", "filename": "/home/eric/git/oisf/benches/sandnet.pcap", "tenant": 0, "delete-when-done": true}}
RCV: {"message": "Successfully added file to list", "return": "OK"}
Success: Successfully added file to list

There is one thing to be careful about: a Suricata message is sent in multiple send operations. This result in possible incomplete read on client side. The worse workaround is to sleep a bit before trying a recv call. An other solution is to use non blocking socket and retry a recv if the previous one has failed.

Pcap-file json format is:

  "command": "pcap-file",
  "arguments": {
    "output-dir": "path to output dir",
    "filename": "path to file or directory to run",
    "tenant": 0,
    "continuous": false,
    "delete-when-done": false

output-dir and filename are required. tenant is optional and should be a number, indicating which tenant the file or directory should run under. continuous is optional and should be true/false, indicating that file or directory should be run until pcap-interrupt is sent or ctrl-c is invoked. delete-when-done is optional and should be true/false, indicating that the file or files under the directory specified by filename should be deleted when processing is complete. delete-when-done defaults to false, indicating files will be kept after processing.