WP fail2ban Manual¶
WP fail2ban is a WordPress plugin to write a myriad of events to syslog for integration with fail2ban.
Introduction¶
History¶
Features¶
CloudFlare and Proxy Servers¶
WPf2b can be configured to work with CloudFlare and other proxy servers. For a brief overview see WP_FAIL2BAN_PROXIES.
Comments¶
WPf2b can log comments. See WP_FAIL2BAN_LOG_COMMENTS.
Pingbacks¶
WPf2b logs failed pingbacks, and can log all pingbacks. For a brief overview see WP_FAIL2BAN_LOG_PINGBACKS.
Spam¶
WPf2b can log comments marked as spam. See WP_FAIL2BAN_LOG_SPAM.
User Enumeration¶
WPf2b can block user enumeration. See WP_FAIL2BAN_BLOCK_USER_ENUMERATION.
Work-Arounds for Broken syslogd¶
WPf2b can be configured to work around most syslogd weirdness. For a brief overview see WP_FAIL2BAN_SYSLOG_SHORT_TAG and WP_FAIL2BAN_HTTP_HOST.
Blocking Users¶
WPf2b can be configured to short-cut the login process when the username matches a regex. For a brief overview see WP_FAIL2BAN_BLOCKED_USERS.
mu-plugins Support¶
WPf2b can easily be configured as a must-use plugin.
Configuration¶
fail2ban¶
Filters¶
- Copy wordpress-hard.conf and wordpress-soft.conf to your fail2ban/filters.d directory
- Edit jail.local to include something like:
[wordpress-hard]
enabled = true
filter = wordpress-hard
logpath = /var/log/auth.log
maxretry = 1
port = http,https
[wordpress-soft]
enabled = true
filter = wordpress-soft
logpath = /var/log/auth.log
maxretry = 3
port = http,https
- Reload or restart fail2ban
wordpress-hard.conf and wordpress-soft.conf¶
There are some things that are almost always malicious, e.g. blocked users and pingbacks with errors. wordpress-hard.conf is designed to catch these so that you can ban the IP immediately.
Other things are relatively benign, like a failed login. You can’t let people try forever, but banning the IP immediately would be wrong too. wordpress-soft.conf is designed to catch these so that you can set a higher retry limit before banning the IP.
For the avoidance of doubt: you should be using both filters.
mu-plugins Support¶
One of the better ways is to install WPf2b as usual and then create a symlink in mu-plugins:
lrwxr-xr-x 1 www www 38 4 Nov 16:24 wp-fail2ban.php -> ../plugins/wp-fail2ban/wp-fail2ban.php
This has the advantage that you can update WPf2b as usual without having to update mu-plugins directly. You don’t need to activate WPf2b, but it won’t hurt if you do.
define() Constants¶
WP_FAIL2BAN_AUTH_LOG¶
New in version 2.2.0.
By default, WPf2b uses LOG_AUTH for logging authentication success or failure. However, some systems use LOG_AUTHPRIV instead, but there’s no good run-time way to tell. If your system uses LOG_AUTHPRIV you should add the following to wp-config.php:
define('WP_FAIL2BAN_AUTH_LOG', LOG_AUTHPRIV);
WP_FAIL2BAN_BLOCK_USER_ENUMERATION¶
New in version 2.1.0.
Brute-forcing WP requires knowing a valid username. Unfortunately, WP makes this all but trivial.
Based on a suggestion from @geeklol and a plugin by @ROIBOT, WPf2b can now block user enumeration attempts. Just add the following to wp-config.php:
define('WP_FAIL2BAN_BLOCK_USER_ENUMERATION', true);
WP_FAIL2BAN_BLOCKED_USERS¶
New in version 2.0.0.
The bots that try to brute-force WordPress logins aren’t that clever (no doubt that will change), but they may only make one request per IP every few hours in an attempt to avoid things like fail2ban. With large botnets this can still create significant load.
Based on a suggestion from @jmadea, WPf2b now allows you to specify a regex that will shortcut the login process if the requested username matches.
For example, putting the following in wp-config.php:
define('WP_FAIL2BAN_BLOCKED_USERS', '^admin$');
will block any attempt to log in as admin before most of the core WordPress code is run. Unless you go crazy with it, a regex is usually cheaper than a call to the database so this should help keep things running during an attack.
WPf2b doesn’t do anything to the regex other than make it case-insensitive.
If you’re running PHP 7, you can now specify an array of users instead:
define('WP_FAIL2BAN_BLOCKED_USERS', ['admin', 'another', 'user']);
WP_FAIL2BAN_HTTP_HOST¶
New in version 3.0.0.
This is for some flavours of Linux where WP_FAIL2BAN_SYSLOG_SHORT_TAG isn’t enough.
If you configure your web server to set an environment variable named WP_FAIL2BAN_SYSLOG_SHORT_TAG on a per-virtual host basis, WPf2b will use that in the syslog tag. This allows you to configure a unique tag per site in a way that makes sense for your configuration, rather than some arbitrary truncation or hashing within the plugin.
Note
This feature has not been tested as extensively as others. While I’m confident it works, FreeBSD doesn’t have this problem so this feature will always be second-tier.
WP_FAIL2BAN_LOG_COMMENTS¶
New in version 3.5.0.
WPf2b can now log comments. To enable this feature, add the following to wp-config.php:
define('WP_FAIL2BAN_LOG_COMMENTS', true);
By default, WPf2b uses LOG_USER for logging comments. If you’d rather it used a different facility you can change it by adding something like the following to wp-config.php:
define('WP_FAIL2BAN_COMMENT_LOG', LOG_LOCAL3);
WP_FAIL2BAN_LOG_PASSWORD_REQUEST¶
New in version 3.5.0.
WP_FAIL2BAN_LOG_PINGBACKS¶
New in version 2.2.0.
Based on a suggestion from maghe, WPf2b can now log pingbacks. To enable this feature, add the following to wp-config.php:
define('WP_FAIL2BAN_LOG_PINGBACKS', true);
By default, WPf2b uses LOG_USER for logging pingbacks. If you’d rather it used a different facility you can change it by adding something like the following to wp-config.php:
define('WP_FAIL2BAN_PINGBACK_LOG', LOG_LOCAL3);
WP_FAIL2BAN_LOG_SPAM¶
New in version 3.5.0.
WPf2b can now log spam comments. To enable this feature, add the following to wp-config.php:
define('WP_FAIL2BAN_LOG_SPAM', true);
The comment ID and IP will be written to WP_FAIL2BAN_AUTH_LOG and matched by wordpress-hard.conf.
WP_FAIL2BAN_OPENLOG_OPTIONS¶
New in version 3.5.0.
WP_FAIL2BAN_PROXIES¶
New in version 2.0.0.
The idea here is to list the IP addresses of the trusted proxies that will appear as the remote IP for the request. When defined:
- If the remote address appears in the WP_FAIL2BAN_PROXIES list, WPf2b will log the IP address from the X-Forwarded-For header
- If the remote address does not appear in the WP_FAIL2BAN_PROXIES list, WPf2b will return a 403 error
- If there’s no X-Forwarded-For header, WPf2b will behave as if WP_FAIL2BAN_PROXIES isn’t defined
To set WP_FAIL2BAN_PROXIES, add something like the following to wp-config.php:
define('WP_FAIL2BAN_PROXIES','192.168.0.42,192.168.42.0/24');
WPf2b doesn’t do anything clever with the list - beware of typos!
WP_FAIL2BAN_SYSLOG_SHORT_TAG¶
New in version 3.0.0.
Some flavours of Linux come with a syslogd that can’t cope with the normal message format WPf2b uses; basically, they assume that the first part of the message (the tag) won’t exceed some (small) number of characters, and mangle the message if it does. This breaks the regex in the fail2ban filter and so nothing gets blocked.
Adding:
define('WP_FAIL2BAN_SYSLOG_SHORT_TAG', true);
to functions.php will make WPf2b use wp as the syslog tag, rather than the normal wordpress. This buys you 7 characters which may be enough to work around the problem, but if it’s not enough you should look at WP_FAIL2BAN_HTTP_HOST or WP_FAIL2BAN_TRUNCATE_HOST too.
WP_FAIL2BAN_TRUNCATE_HOST¶
New in version 3.5.0.
If you’ve set WP_FAIL2BAN_SYSLOG_SHORT_TAG and defining WP_FAIL2BAN_HTTP_HOST for each virtual host isn’t appropriate, you can set WP_FAIL2BAN_TRUNCATE_HOST to whatever value you need to make syslog happy:
define('WP_FAIL2BAN_TRUNCATE_HOST', 8);
This does exactly what the name suggests: truncates the host name to the length you specify. As a result there’s no guarantee that what’s left will be enough to identify the site.
WP_FAIL2BAN_XMLRPC_LOG¶
New in version 3.6.0.
This is for debugging and future development.
Attackers are doing weird things with XML-RPC, so this logs the raw post data to the file specified:
define('WP_FAIL2BAN_XMLRPC_LOG', '/var/log/xml-rpc.log');
Filters¶
wordpress-hard.conf¶
# Fail2Ban filter for WordPress hard failures
# Auto-generated: 2018-11-04T16:40:53+00:00
#
[INCLUDES]
before = common.conf
[Definition]
_daemon = (?:wordpress|wp)
failregex = ^%(__prefix_line)sBlocked authentication attempt for .* from <HOST>$
^%(__prefix_line)sBlocked user enumeration attempt from <HOST>$
^%(__prefix_line)sSpam comment \d+ from <HOST>$
^%(__prefix_line)sXML-RPC multicall authentication failure from <HOST>$
^%(__prefix_line)sPingback error .* generated from <HOST>$
^%(__prefix_line)sAuthentication attempt for unknown user .* from <HOST>$
^%(__prefix_line)sXML-RPC authentication attempt for unknown user .* from <HOST>$
ignoreregex =
# DEV Notes:
# Requires the 'WP fail2ban' plugin:
# https://github.com/invisnet/wp-fail2ban/
#
# Author: Charles Lecklider
wordpress-soft.conf¶
# Fail2Ban filter for WordPress soft failures
# Auto-generated: 2018-11-04T16:40:53+00:00
#
[INCLUDES]
before = common.conf
[Definition]
_daemon = (?:wordpress|wp)
failregex = ^%(__prefix_line)sAuthentication failure for .* from <HOST>$
^%(__prefix_line)sXML-RPC authentication failure for .* from <HOST>$
ignoreregex =
# DEV Notes:
# Requires the 'WP fail2ban' plugin:
# https://github.com/invisnet/wp-fail2ban/
#
# Author: Charles Lecklider