CrowdSec

Presentation

CrowdSec is a free and open-source security automation tool leveraging local IP behavior detection and a community-powered IP reputation system.

LL::NG provides two Crowdsec plugins:

  • a Bouncer that can reject CrowdSec banned IP requests or just provide an environment variable that can be used inanother plugin rule. For example, a second factor may be required if user’si IP is CrowdSec banned
  • an Agent that push alerts to Crowdsec server and ban IP addresses if limits are reached:
    • for each authentication failure (Crowdsec scenario: llng/badcredentials)
    • if filters are set, for each filter alert, see Filters (Crowdsec scenario: llng/urlscan)

You can also find CrowdSec agents to parse webserver logs in CrowdSec hub.

Configuration

Important

If you need to whitelist something, you can use a rule in “activation” using $env->{REMOTE_ADDR} for example.

Bouncer

To configure bouncer plugin, go in General Parameters > Advanced Parameters > Security > CrowdSec > Bouncer.

You can then configure:

  • Activation: enable this plugin (default: disabled)
  • Ignore CrowdSec failures: avoid to block user in case of CrowdSec error (default: disabled)
  • Action: reject or warn and set $env->{CROWDSEC_REJECT} = 1
  • Base URL of local API: base URL of CrowdSec local API (default: http://localhost:8080)
  • API key: API key, usually given by cscli bouncers add mylemon

Agent

To configure agent plugin, go in General Parameters > Advanced Parameters > Security > CrowdSec > Agent.

You can then configure:

  • Activation: enable this plugin (default: disabled)
  • Crowdsec agent ID: machine_id registered in Crowdsec local server
  • Password: password
  • Max failures allowed during delay: maximume failures allowed in the delay. If reached, the plugin will send a Crowdsec decision (ban). 0 means that no ban decision will be pushed
  • Check delay: number of seconds to consider failures. Default: 180
  • Filters directory: directory where Crowdsec can find its filters. If not defined or empty, filters are disabled. See Filters
  • Ban response code: code for rejections based on filters (default: 404)
  • Ban response content: override the content of rejection responses

Note that:

  • Agent just push alerts, it never block anything. You must enable Bouncer to do this
  • Base URL of local API has to be configured into Bouncer.

Filters

When this feature is enabled, the CrowdsecAgent plugin parse the directory given in Filters directory to find files. A file must refer to:

The category is the scope of the filter (example: “url”) and the type is the format of the file (example: “txt”). The type is the suffix of the file, there are two ways to define the category: either by setting the category as second suffix in the main directory, either by storing the file into a subdirectory with a name starting by the category. Examples:

  • bad.url.txt is a file formatted as “txt” and owned by category “url”
  • url1/bad.re is a file formatted as “re” and owned by category “url”
Formats
  • txt: list of substring
  • re: list of regular expression

An empty line or a line started by # is ignored.

Examples:

  • txt
  • re
Categories
  • url, if the required URI matches a given expression, then:
    • an alert is sent to local Crowdsec server
    • the portal sends a 404 Not found response