reCAPTCHA

As of LiteSpeed Web Server 5.4, reCAPTCHA is available as a method of defense against DDoS attack.

Tip

reCAPTCHA may also be used as a method of WordPress Brute Force Attack Protection. Please see the WP-Protect Guide for more information about that.

Note

reCAPTCHA activation is dependent on the URL being accessed. It does not activate for API urls. reCAPTCHA only activates for URLs accessed by real clients.

Enable Globally at the Server Level

Access the WebAdmin console via https://YOUR_SERVER_IP:7080

Navigate to Configuration > Server > Security > reCAPTCHA Protection

!reCAPTCHA protection

Set Enable reCAPTCHA to Yes. This is the master switch and it is required for both a control panel environment and an LSWS native environment. It will enable the reCAPTCHA feature for all control panel Apache virtual hosts as well as LSWS native virtual hosts globally. It may be overridden at the virtual host level.

For other options, hover over the ? symbol to view detailed information about that option.

For demonstration purposes, we will set Trigger Sensitivity to maximum (100), and reCAPTCHA Type to Checkbox. You may adjust these values according to your needs. Save and restart LSWS. This sensitivity setting will be inherited by all control panel Apache virtual hosts and LSWS native virtual hosts unless overridden at the virtual host level.

!reCAPTCHA configuration

After making the change described above, the appropriate directives will be added to the LiteSpeed configuration file /usr/local/lsws/conf/httpd_config.xml.

Alternatively, you can add them yourself. Edit the file via vi /usr/local/lsws/conf/httpd_config.xml, and place the following code after the <security>...</security> section: <lsrecaptcha> <enabled>1</enabled> <type>1</type> <sensitivity>100</sensitivity> </lsrecaptcha>

You can also enable reCAPTCHA on an individual virtual host that is under attack, while leaving other websites disabled.

Validation expiration time

When a visitor accesses the website, they will need to go though reCAPTCHA validation. This validation protects the server against HTTP Flood and other DDoS attacks.

After passing the reCAPTCHA validation, the visitor is temporarily whitelisted as long as they continue to browse the site. This makes for a better user experience. Once the visitor has been inactive for a specified time, reCAPTCHA is once again enabled for that visitor's next request.

Prior to LSWS v5.4.8 build 4, expiration time was 20 minutes. As of v5.4.8 b4, expiration is one day. If one day doesn't work for you, it will be configurable in the upcoming v6 release.

!reCAPTCHA verification

Override/Disable at the Virtual Host Level

Assuming you have enabled reCAPTCHA at the server level globally, you can override the settings at a virtual host level, but how you do so depends on which environment you are using.

Override/Disable for Apache Virtual Hosts

As of LSWS v5.4RC4, you can configure vhost-level reCAPTCHA via the LsRecaptcha directive in the virtual host include configuration, like so:

<IfModule LiteSpeed>
   LsRecaptcha (0-100)
</IfModule>

The 0-100 value defines or overrides Trigger Sensitivity for the virtual host. When LsRecaptcha is set to 0, it means the reCAPTCHA feature has been disabled for that virtual host.

Note

The LsRecaptcha directive cannot be used in .htaccess files.

Override for LiteSpeed Native Virtual Hosts

Use the LSWS WebAdmin console to override reCAPTCHA in LSWS native mode.

Navigate to Configuration > Virtual Hosts > Security > reCAPTCHA Protection

!Override reCAPTCHA for virtual hosts

Set Trigger Sensitivity

Trigger Sensitivity refers to the automatic reCAPTCHA sensitivity. The higher the value, the more likely reCAPTCHA Protection will be used. A value of 0 is equivalent to “Off” while a value of 100 is equivalent to “Always On”.

Default Values

Server level: 0. Virtual Host level: inherits server-level setting. Syntax: Integer value between 0 and 100.

LiteSpeed calculates Trigger Sensitivity as the percentage of your server capacity used, based on the number of active connections. reCAPTCHA is activated when this formula is true:

Active connections * 100 / Max Connections > (100 - Trigger Sensitivity)

For example:

If Max Connections = 1000, Trigger Sensitivity = 20, and you currently have 900 connections, the formula would be evaluated like so:

900 * 100 / 1000 > 100 - 20

90 > 80

The result is true, so the incoming connection will be given a reCAPTCHA test.

Calculating backwards, you can see that when the number of connections drops to less than 800, reCAPTCHA will not be invoked.

Warning

We've discovered in real world usage that Trigger Sensitivity can be ineffective in some setups.

Here's why: Trigger Sensitivity is based on the number of active connections. But sometimes, sites have a large number of connections that are unrelated to the main page HTML. These extra connections don't result in anything that is visible to the user, but they require a high connection limit. The high connection limit negatively impacts the Trigger Sensitivity calculation, making most values under 100 behave effectively like 0.

In our experience, the headaches caused by trying to use Trigger Sensitivity under these conditions are not worth the benefits. If you have high connection limits set, we recommend two possible courses of action:

  • Go all or nothing: set the sensitivity to 100 (always on) or 0 (always off)
  • Use rewrite rules: Set sensitivity to 0 at the virtual host level, and then selectively enable reCAPTCHA for certain URLs via rewrite rules, like this example, which applies to all URLs in the /admin/ directory: ` <IfModule LiteSpeed> RewriteRule /admin/ - [E=verifycaptcha:deny] </IfModule>

Advanced Configuration

Advanced Configuration: Define reCAPTCHA Actions through Rewrite Rules.

If you want to further define the reCAPTCHA action as deny or drop, you can use one of the following rewrite rule directives:

  • [E=verifycaptcha]
  • [E=verifycaptcha:deny]
  • [E=verifycaptcha:drop]

[E=verifycaptcha] will always redirect to reCAPTCHA until verified. ACTION can be deny to return a 403 or drop to drop the connection when Max Tries is reached. Until Max Tries is reached, the client will be redirected to reCAPTCHA.

Example

RewriteCond SOME-CONDITIONAL-CHECK
RewriteRule .* - [E=verifycaptcha]

(SOME-CONDITIONAL-CHECK would be a suspicious UA, IP address, etc.)

Note

In most cases, rewrite rules will override the default server behavior. However, in cases where trigger sensitivity is high, visitors may be sent directly to reCAPTCHA before the rewrite rules can even be processed.

Enable reCAPTCHA Protection for any URL

You can enable reCAPTCHA for a specific URL. For example, you might want to protect the admin area (/administrator/) for all Joomla sites on the server.

Example

In cPanel, create /etc/apache2/conf.d/userdata/joomlaprotection.conf with the following content:

<IfModule LiteSpeed>
RewriteRule /administrator/ - [E=verifycaptcha:deny]
</IfModule>

Apply to all cPanel virtual hosts and restart LiteSpeed:

/usr/local/cpanel/scripts/rebuildhttpdconf
service lsws restart

Customize the Good Bots List

Google bots are considered good bots because they help index your site. However, they cannot do their job properly without receiving the correct page. The Bot Whitelist configuration may be used to specify bots that you may need for your site.

!reCAPTCHABots

Here, we have configured Edge in the Bot Whitelist text area. Bot Whitelist is a contains match (case sensitive), but regex may be used as well.

After restarting, browsers containing Edge in the user-agent header will bypass reCAPTCHA:

!reCAPTCHATest

The Allowed Bot Hits configuration may be used to limit how many times a good bot (including Googlebot) is allowed to hit a URL before it is redirected to reCAPTCHA as well. This may be useful to prevent bad actors from bypassing reCAPTCHA using a custom user agent.

Customize the reCAPTCHA Page

The default reCAPTCHA page is generic. If you would like to customize the page, you may do so by creating a file at $SERVER_ROOT/lsrecaptcha/_recaptcha_custom.shtml.

There are two script tags that are required and it is strongly recommended to avoid changing the form and the recaptchadiv unless you know what you are doing. There are three echos within the page itself. Those are used by the web server to customize the reCAPTCHA type and keys and specify any query string used.

Beyond those required attributes, everything else is customizable. As noted before, please ensure that you have backups of the default page and your customized page. Note that the .shtml extension is required in order to use the LSWS configured type and keys.

Add Headers to the reCAPTCHA Page

You can customize the headers on the reCAPTCHA page. To do so, add a static context with the url /.lsrecap/, then add the desired response header for that context.

<IfModule LiteSpeed>
    <Location "/.lsrecap/">
        Header set Access-Control-Allow-Origin "*"
    </Location>
</IfModule>

This snippet cannot be added to .htaccess. It must either be added to an Apache config file, or via the WebAdmin Console for an LSWS Native virtual host.

Example

To add a CORS header to the reCAPTCHA page in a WHM/cPanel environment:

  • Add a <Location "/.lsrecap/"> context to a global include file at /etc/apache2/conf.d/userdata/lsrecaptcha.conf to apply the customization to all virtual hosts
  • Add a <Location "/.lsrecap/"> context to a virtual host include at /etc/apache2/conf.d/userdata/ssl/2_4/$USER/yourdomain.com/lsrecapcha.conf to apply the customization only to $USER virtual host

Apply Your Own Site Key

You can apply your own reCAPTCHA key and adjust the configuration as you like from the Google developer reCAPTCHA page. Client verification is completely determined by Google's reCAPTCHA service. The invisible type may display a difficult puzzle.

For server wide protection that needs to cover a lot of domains, make sure Verify the origin of reCAPTCHA solutions is unchecked. Otherwise, you may need to apply a key for each domain. Please refer to the Google doc.

Troubleshooting

reCAPTCHA Returns 403 and Drops Connection

If reCAPTCHA fails a few times, it will return a 403 error and then drop the connection from that IP. It works this way in order to block attacks. If the invisible reCAPTCHA keeps auto-refreshing and then fails, just change the type to one-click.


Last update: June 17, 2021