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Firewall

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CrowdSec Remediation Component written in golang for firewalls.

crowdsec-firewall-bouncer will fetch new and old decisions from a CrowdSec API and add them to a blocklist used by supported firewalls.

Supported firewalls:

  • iptables (IPv4 ✔️ / IPv6 ✔️ )
  • nftables (IPv4 ✔️ / IPv6 ✔️ )
  • ipset only (IPv4 ✔️ / IPv6 ✔️ )
  • pf (IPV4 ✔️ / IPV6 ✔️ )

Installation​

Packages for crowdsec-firewall-bouncer are available on our repositories. You need to pick the package according to your firewall system :

IPTables​

sudo apt install crowdsec-firewall-bouncer-iptables

NFTables​

sudo apt install crowdsec-firewall-bouncer-nftables

pf​

sudo pkg install crowdsec-firewall-bouncer

See as well Manual Installation documentation below

Configuration​

There are two primary ways to use the firewall bouncer:

  • managed (default): cs-firewall-bouncer will create ipset/nft sets, insert the associated firewall rules and manage the set contents
  • set only: you already have a (complex) firewall setup, cs-firewall-bouncer will only manage the content of existing specified sets

Managed mode : Iptables/ipset or Nftables​

This is the default behaviour

In "managed" mode (mode nftables or iptables), component creates all the needed elements (rules, sets) and insert the appropriate rules in nftables or iptables.

warning

IPSet (when using iptables mode) does not support a timeout greater than 2147483 seconds (about 596 hours). If crowdsec is configured to take decisions longer than that, the bouncer will cap the duration to 2147482 seconds.

Set Only : Iptables/Ipset table​

In iptables set-only mode (mode ipset), the component only handles the contents of sets that are specified by blacklists_ipv4 and blacklists_ipv6. These sets must be created before starting the component, and it is the user's responsibility to create the associated iptables rules.

warning

IPSet does not support a timeout greater than 2147483 seconds (about 596 hours). If crowdsec is configured to take decisions longer than that, the bouncer will cap the duration to 2147482 seconds.

Set Only : nftables​

In nftables set only mode (mode nftables with nftables.{ipv4,ipv6}.set-only set to true), the component only manages the contents of the sets. It's the user's responsibility to create the associated chains and sets :

/tmp/bouncer.nft
table ip crowdsec {
	set crowdsec-blacklists {
		type ipv4_addr
		flags timeout
	}

	chain crowdsec-chain {
		type filter hook input priority filter; policy accept;
		ip saddr @crowdsec-blacklists drop
	}
}
table ip6 crowdsec6 {
	set crowdsec6-blacklists {
		type ipv6_addr
		flags timeout
	}

	chain crowdsec6-chain {
		type filter hook input priority filter; policy accept;
		ip6 saddr @crowdsec6-blacklists drop
	}
}

Configuration Reference​

You can find a default configuration hosted on the Github Repository this is provided with the installation package.

pid_dir​

Depreacted

Directory to store the pid file

daemonize​

Deprecated

Run the component in the background

warning

This field has now been deprecated and is ignored within the component

mode​

iptables | nftables | ipset | pf

Firewall mode to use

update_frequency​

string (That is parseable by time.ParseDuration)

Frequency to contact the API for new/deleted decisions

scenarios_containing​

[ ]string

Get only IPs banned for triggering scenarios containing either of provided word.

Example
scenarios_containing: ["ssh", "http"]

scenarios_not_containing​

[ ]string

Ignore IPs banned for triggering scenarios containing either of provided word.

Example
scenarios_not_containing: ["ssh", "http"]

scopes​

[ ]string

Decisions will be filtered on the provided scopes.

Example
scopes: ["Ip", "Range"]

origins​

[ ]string

Decisions will be filtered on the provided origins.

Example
origins: ["cscli", "crowdsec"]

log_mode​

file | stdout

Where the log contents are written (With file it will be written to log_dir with the name crowdsec-firewall-bouncer.log)

log_dir​

string

Log directory path, that will contain the log file

log_level​

trace | debug | info | warn | error

Log level

log_compression​

true | false

Compress log files on rotation

log_max_size​

int (in MB)

Max size of log files before rotation

log_max_backups​

int

How many backup log files to keep before deletion (can happen before log_max_age is reached)

log_max_age​

int (in days)

Max age of backup files before deletion (can happen before log_max_backups is reached)

api_url​

string

URL of the local API EG: http://127.0.0.1:8080

api_key​

string

API key to authenticate with the local API

cert_path​

string

Path to the client certificate for authentication

key_path​

string

Path to the certificate key used with cert_path

ca_cert_path​

string

Path to the CA certificate to trust usually used in conjunction with cert_path and key_path

insecure_skip_verify​

true | false

Skip verification of the API certificate, typical for self-signed certificates

disable_ipv6​

true | false

disable interacting with ipv6 chains/sets, defaults to false

deny_action​

DROP | REJECT

firewall action to apply, defaults to DROP

deny_log​

true | false

if set to true, enables logging of dropped packets (ie. -j LOG)

deny_log_prefix​

string

if logging is true, this sets the log prefix, defaults to "crowdsec: "

Iptables/Ipset specific directives​

iptables_chains​

[]string

specify a list of chains to insert rules

iptables_chains:
  - INPUT
  #- FORWARD
  #- DOCKER-USER
info

If you are using a dockerized application and allow remote connections to the exposed port, you need to add the DOCKER-USER chain to the list of chains.

blacklists_ipv4​

string

name of the ipv4 set

blacklists_ipv6​

name of the ipv6 set

ipset_size​

int

maximum number of entries in the ipset (default: 131072)

ipset_type​

string

type to use for the set (default: nethash)

info

The default value for ipset_size has been raised in v0.0.28 (from 65536) to allow for larger blocklists.

Nftables specific directives​

Nftables mode has its own nftables section, with sub-section of ipv4 and ipv6 :

## nftables
nftables:
  ipv4:
    enabled: true
    set-only: false
    table: crowdsec
    chain: crowdsec-chain
  ipv6:
    enabled: true
    set-only: false
    table: crowdsec6
    chain: crowdsec6-chain

enabled​

true | false

Enable or disable ipv4 or ipv6

set-only​

true | false

If set-only is set to true, the component will only manage the set contents.

table​

string

Name of the nftables table

chain​

string

Name of the nftables chain

Manual installation​

Assisted​

First, download the latest crowdsec-firewall-bouncer release.

$ tar xzvf crowdsec-firewall-bouncer.tgz
$ sudo ./install.sh

From source​

Run the following commands:

git clone https://github.com/crowdsecurity/cs-firewall-bouncer.git
cd cs-firewall-bouncer/
make release
tar xzvf crowdsec-firewall-bouncer.tgz
cd crowdsec-firewall-bouncer-v*/
sudo ./install.sh

Upgrade​

If you already have crowdsec-firewall-bouncer installed, please download the latest release and run the following commands:

tar xzvf crowdsec-firewall-bouncer.tgz
cd crowdsec-firewall-bouncer-v*/
sudo ./upgrade.sh

Configuration for manual installation​

To be functional, the crowdsec-firewall-bouncer service must be able to authenticate with the local API. The install.sh script will take care of it (it will call cscli bouncers add on your behalf). If it was not the case, the default configuration is in /etc/crowdsec/bouncers/crowdsec-firewall-bouncer.yaml.

You can then start the service:

sudo systemctl enable --now crowdsec-firewall-bouncer

If you need to make changes to the configuration file and be sure they will never be modified or reverted by package upgrades, starting from v0.0.25 you can write them in a crowdsec-firewall-bouncer.yaml.local file as described in Overriding values. Package upgrades may have good reasons to modify the configuration, so be careful if you use a .local file.

logs​

logs can be found in /var/log/crowdsec-firewall-bouncer.log

modes​

  • mode nftables relies on github.com/google/nftables to create table, chain and set.
  • mode iptables relies on iptables and ipset commands to insert match-set directives and maintain associated ipsets
  • mode ipset relies on ipset and only manage contents of the sets (they need to exist at startup and will be flushed rather than created)
  • mode pf relies on pfctl command to alter the tables. You are required to create the following tables on your pf.conf configuration:
 # create crowdsec ipv4 table
table <crowdsec-blacklists> persist

# create crowdsec ipv6 table
table <crowdsec6-blacklists> persist

You can refer to the step-by-step instructions of the user tutorial on FreeBSD to setup crowdsec-firewall-bouncer with pf.

ipset​

ipset lists have to exist before crowdsec-firewall-bouncer starts. You can create them and add them to your iptables like this:

ipset create crowdsec-blacklists hash:ip timeout 0 maxelem 150000
ipset create crowdsec6-blacklists hash:ip timeout 0 family inet6 maxelem 150000
iptables -I INPUT 1 -m set --match-set crowdsec-blacklists src -j DROP
ip6tables -I INPUT 1 -m set --match-set crowdsec6-blacklists src -j DROP
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