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Version: v1.4.0

Nginx Bouncer


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A lua bouncer for nginx.

How does it work ?#

This bouncer leverages nginx lua's API, namely access_by_lua_block to check e IP address against the local API.

Supported features:

  • Live mode (query the local API for each request)
  • Stream mode (pull the local API for new/old decisions every X seconds)
  • Ban remediation (can ban an IP address by redirecting him or returning a custom HTML page)
  • reCAPTCHA v2 remediation (can return a captcha)
  • Works with IPv4/IPv6
  • Support IP ranges (can apply a remediation on an IP range)

At the back, this bouncer uses crowdsec lua lib.



Install the following packages:

sudo apt install nginx lua5.1 libnginx-mod-http-lua luarocks gettext-base lua-cjson

Using packages#

First, setup crowdsec repositories.

sudo apt install crowdsec-nginx-bouncer

In stream mode, the bouncer will launch an internal timer to pull the local API at the first request made to the server.

Manual installation#


CrowdSec NGINX Bouncer depends on nginx lua5.1 libnginx-mod-http-lua luarocks gettext-base.

It has been tested only on Debian/Ubuntu based distributions.

Download the latest release here

tar xvzf crowdsec-nginx-bouncer.tgzcd crowdsec-nginx-bouncer-v*/./

Note: Don't run the script with sudo (the script already use sudo to install dependencies).

If you are on a mono-machine setup, the crowdsec-nginx-bouncer install script will register directly to the local crowdsec, so you're good to go !

โš ๏ธ the installation script will take care of dependencies for Debian/Ubuntu

non-debian based dependencies
  • libnginx-mod-http-lua : nginx lua support
  • lua5.1: Lua
  • lua-cjson: JSON parser/encoder for Lua
  • luarocks : Lua package manager
  • gettext-base: for the installation script


From package#

sudo apt-get updatesudo apt-get install crowdsec-nginx-bouncer

Upgrade from v0 to v1 introduce many changes. Pick up the maintainer configuration to avoid anything breaking. Configuration migration might not be trivial.

Manual Upgrade#

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

tar xzvf crowdsec-nginx-bouncer.tgzcd crowdsec-nginx-bouncer-v*/sudo ./upgrade.shsudo systemctl restart nginx


Bouncer configuration#

API_URL=<CROWDSEC_LAPI_URL>API_KEY=<CROWDSEC_LAPI_KEY># bounce for all type of remediation that the bouncer can receive from the local APIBOUNCING_ON_TYPE=all# when the bouncer receive an unknown remediation, fallback to this remediationFALLBACK_REMEDIATION=banMODE=streamREQUEST_TIMEOUT=1000# exclude the bouncing on those locationEXCLUDE_LOCATION=# Cache expiration in live mode, in secondCACHE_EXPIRATION=1# Update frequency in stream mode, in secondUPDATE_FREQUENCY=10#those apply for "ban" action# /!\ REDIRECT_LOCATION and BAN_TEMPLATE_PATH/RET_CODE can't be used together. REDIRECT_LOCATION take priority over RET_CODE AND BAN_TEMPLATE_PATHBAN_TEMPLATE_PATH=/var/lib/crowdsec/lua/templates/ban.htmlREDIRECT_LOCATION=RET_CODE=#those apply for "captcha" action# reCAPTCHA Secret KeySECRET_KEY=# reCAPTCHA Site keySITE_KEY=CAPTCHA_TEMPLATE_PATH=/var/lib/crowdsec/lua/templates/captcha.htmlCAPTCHA_EXPIRATION=3600

NGINX Configuration#

The bouncer NGINX configuration is located in /etc/nginx/conf.d/crowdsec_nginx.conf :

lua_package_path '/usr/lib/crowdsec/lua/?.lua;;';lua_shared_dict crowdsec_cache 50m;resolver ipv6=off;lua_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;init_by_lua_block {        cs = require "crowdsec"        local ok, err = cs.init("/etc/crowdsec/bouncers/crowdsec-nginx-bouncer.conf", "crowdsec-nginx-bouncer/v0.0.7")        if ok == nil then                ngx.log(ngx.ERR, "[Crowdsec] " .. err)                error()        end        ngx.log(ngx.ALERT, "[Crowdsec] Initialisation done")}
access_by_lua_block {        local cs = require "crowdsec"        cs.Allow(ngx.var.remote_addr)        }

The bouncer uses lua_shared_dict to share cache between all workers.

If you want to increase the cache size you need to change this value lua_shared_dict crowdsec_cache 50m;.

โš ๏ธ Do not rename the crowdsec_cache shared dict, else the bouncer will not work anymore.

When using captcha remediation#

To make HTTP request in the bouncer, you need to configure a resolver and ssl certifcates. Here is a our example.

To make secure HTTP request in the bouncer, we need to specify a trusted certificate (lua_ssl_trusted_certificate). You can also change this with a valid one :

  - /etc/ssl/certs/ca-certificates.crt (Debian/Ubuntu/Gentoo)  - /etc/pki/tls/certs/ca-bundle.crt (Fedora/RHEL 6)  - /etc/ssl/ca-bundle.pem (OpenSUSE)  - /etc/pki/tls/cacert.pem (OpenELEC)  - /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem (CentOS/RHEL 7)  - /etc/ssl/cert.pem (OpenBSD, Alpine)

Setup captcha#

Currently, only reCAPTCHA v2 is supported.

If you want to use reCAPTCHA with your Nginx Bouncer, you must provide a reCAPTCHA Site key and Secret key in your bouncer configuration (recaptcha documentation).

Edit etc/crowdsec/bouncers/crowdsec-nginx-bouncer.conf and configure the following options:


Restart Nginx.

You can add a decisions with a type captcha to check if it works correctly:

sudo cscli decisions add -i <IP_TO_TEST> -t captcha


Why aren't decisions applied instantly#

In stream mode, the bouncer will launch an internal timer to pull the local API at the first request. So the cache won't be refreshed until the first request hits the service.

Resolver and certificates#

In order to query for the reCAPTCHA verification, you need to set a resolver and a SSL certificate in your nginx configuration. If you already have a resolver set in nginx configuration, you don't need to add another one. Here is a config example, but you can change values:

resolver ipv6=off;lua_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;

And restart Nginx.




CrowdSec Local API key.

Generated with sudo cscli bouncers add command.



CrowdSec local API URL.



Type of remediation we want to bounce. If you choose ban only and receive a decision with captcha as remediation, the bouncer will skip the decision.



The fallback remediation is applied if the bouncer receives a decision with an unknown remediation.



The default mode is live.

The bouncer mode:

  • stream: The bouncer will pull new/old decisions from the local API every X seconds (UPDATE_FREQUENCY parameter).

Note: The timer that pull the local API will be triggered after the first request.

  • live: The bouncer will query the local API for each requests (if IP is not in cache) and will store the IP in cache for X seconds (CACHE_EXPIRATION parameter).



Timeout in milliseconds for the HTTP requests done by the bouncer to query CrowdSec local API or (for the reCAPTCHA verification).



The locations to exclude while bouncing. It is a list of location, separated by commas.

โš ๏ธ It is not recommended to put EXCLUDE_LOCATION=/.


This option is only for the live mode.


The cache expiration, in second, for IPs that the bouncer store in cache in live mode.


This option is only for the stream mode.


The frequency of update, in second, to pull new/old IPs from the CrowdSec local API.


This option is only for the ban remediation.


The location to redirect the user when there is a ban.

If it is not set, the bouncer will return the page defined in the BAN_TEMPLATE_PATH with the RET_CODE (403 by default).


This option is only for the ban remediation.


The path to a HTML page to return to IPs that trigger ban remediation.

By default, the HTML template is located in /var/lib/crowdsec/lua/templates/ban.html.


This option is only for the ban remediation.


The HTTP code to return for IPs that trigger a ban remediation. If nothing specified, it will return a 403.


This option is only for the captcha remediation.


The reCAPTCHA v2 secret key.


This option is only for the captcha remediation.


The reCAPTCHA v2 site key.


This option is only for the captcha remediation.


The path to a captcha HTML template.

The bouncer will try to replace {{recaptcha_site_key}} in the template with SITE_KEY parameter.

By default, the HTML template is located in /var/lib/crowdsec/lua/templates/captcha.html.


This option is only for the captcha remediation.


The time for which the captcha will be validated. After this duration, if the decision is still present in CrowdSec local API, the IPs address will get a captcha again.