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Block unwanted requests to a site

The VIP_Request_Block utility class can be used to block unwanted requests to a site such as those from a bot crawling the site or a malicious IP address. A 403 HTTP Response Status Code is returned for requests that are blocked by VIP_Request_Block.

Considerations

  • Code to block a request should be added to vip-config/vip-config.php to ensure that requests that are intended to be blocked are blocked early.
  • Be careful not to block legitimate traffic (e.g., Googlebot, a reverse proxy, or a CDN). Always take time to confirm that an IP address, User-Agent, or HTTP header is suspicious before blocking it.
  • Requests blocked via VIP_Request_Block are blocked at the origin, not the edge (load balancer). If a request is served from the cache at the edge, it does not reach the origin and cannot be blocked by this class.
  • The VIP_Request_Block class is loaded very early via wp-config.php on VIP Platform environments, before WordPress Core is loaded. When developing on a local development environment the load order might differ from the VIP Platform. It is therefore recommended to wrap statements in an if ( class_exists( 'VIP_Request_Block' ) ) check to avoid errors.

Block by IP

Use the VIP_Request_Block::ip() method to block single IP addresses. IP ranges cannot be blocked with this method. If VIP_Request_Block::ip() is called with an invalid IP address, an error will be logged to the application’s Runtime Logs.

The whois terminal command can be used to query an IP address in order to make a more educated decision about which IP addresses are suitable to be blocked.

Use caution to avoid blocking a reverse proxy IP instead of the client’s IP. Blocking a reverse proxy IP will result in legitimate traffic being blocked.

vip-config/vip-config.php
// Example VIP_Request_Block::ip( string $value );
if ( class_exists( 'VIP_Request_Block' ) ) {
   VIP_Request_Block::ip( '13.37.13.37' );
   VIP_Request_Block::ip( '13.37.13.38' );
}

Block by User-Agent

It can be useful to block by user-agent in cases where a tool or bot sends suspicious requests from various IP addresses while retaining the same User-Agent. WordPress VIP provides two User-Agent blocking methods for WordPress applications.

When blocking by User-Agents, take care not to block common browser User-Agents, or User-Agents that look similar. It is a best practice to search recent HTTP Request Logs to validate that full, or partial matching blocking will only impact the intended requests. Blocking requests from common browser User-Agents can result in blocking real user requests.

Block by full User-Agent match

The VIP_Request_Block::ua() method can be used when the full text of an unwanted User-Agent is known and uses case-sensitive matching.

vip-config/vip-config.php
// Example VIP_Request_Block::ua( string $user_agent );
if ( class_exists( 'VIP_Request_Block' ) ) {
   VIP_Request_Block::ua( 'SuspiciousBot/1.1' );
   VIP_Request_Block::ua( 'AnotherBot/2.1' );
}

Block by partial User-Agent match

The VIP_Request_Block::ua_partial_match() method can be used when requests from a user agent which contains a sub-string need to be blocked. This method does not support regular expressions, and the string matching is case-sensitive.

vip-config/vip-config.php
// Example VIP_Request_Block::ua_partial_match( string $user_agent_substring );
// Will match and block for:
// 	- SuspiciousBot/1.1
// 	- SomewhatSuspiciousBot/1.8 - https://example.com/robot-policy
if ( class_exists( 'VIP_Request_Block' ) ) {
   VIP_Request_Block::ua_partial_match( 'SuspiciousBot/' );
}

Block by HTTP header

When blocking by HTTP header, $header is case-insensitive, but $value is case-sensitive.

vip-config/vip-config.php
// Example VIP_Request_Block::header( string $header, string $value );
if ( class_exists( 'VIP_Request_Block' ) ) {
   VIP_Request_Block::header( 'x-my-header', 'my-header-value' );
}

Block by other logic

If the above methods are insufficient, a request can be blocked based on custom logic with the VIP_Request_Block::block_and_log() method. This method blocks a request and logs a message to the error_log. The condition in which a given request will be blocked must be defined using custom logic.

Error output can be retrieved with VIP-CLI Runtime Logs.

The following is an example of blocking a request to a specific URL:

vip-config/vip-config.php
// Example VIP_Request_Block::block_and_log( string $value, string $criteria );
if ( isset( $_SERVER['REQUEST_URI'] ) && '/disallowed-path' === $_SERVER['REQUEST_URI'] ) {
   if ( class_exists( 'VIP_Request_Block' ) ) {
     VIP_Request_Block::block_and_log( '/disallowed-path', 'REQUEST URI' );
   }
}

A request made to /disallowed-path will produce the following message in the error_log:

VIP Request Block: request was blocked based on "REQUEST_URI" with value of "/disallowed-path"

Last updated: January 19, 2023