VIP Request Block: Add function to allow for blocking by partial User…

… Agent string. (#4001)

* Add function to allow for blocking by partial User Agent string.

* Add test for blocking by partial User Agent string match

* Use strpos() over str_contains for PHP 7.x backwards-compatibility

* Fix linting

* Use late static binding

Co-authored-by: Rebecca Hum <16962021+rebeccahum@users.noreply.github.com>

lib/class-vip-request-block.php

@@ -50,15 +50,15 @@ public static function ip( string $value ) {
 			$hdr = strtolower( $_SERVER['HTTP_TRUE_CLIENT_IP'] );
 			$bin = inet_pton( $hdr );
 			if ( $bin === $ip || $hdr === $value ) {
-				return self::block_and_log( $value, 'true-client-ip' );
+				return static::block_and_log( $value, 'true-client-ip' );
 			}
 		}
 
 		if ( ! empty( $_SERVER['HTTP_X_FORWARDED_FOR'] ) ) {
 			$ips = array_map( fn ( string $s ): string => strtolower( trim( $s ) ), explode( ',', $_SERVER['HTTP_X_FORWARDED_FOR'] ) );
 			$bin = array_map( 'inet_pton', $ips );
 			if ( in_array( $value, $ips, true ) || in_array( $ip, $bin, true ) ) {
-				return self::block_and_log( $value, 'x-forwarded-for' );
+				return static::block_and_log( $value, 'x-forwarded-for' );
 			}
 		}
 
@@ -75,7 +75,22 @@ public static function ip( string $value ) {
 	public static function ua( string $user_agent ) {
 		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotValidated, WordPressVIPMinimum.Variables.RestrictedVariables.cache_constraints___SERVER__HTTP_USER_AGENT__
 		if ( isset( $_SERVER['HTTP_USER_AGENT'] ) && $user_agent === $_SERVER['HTTP_USER_AGENT'] ) {
-			return self::block_and_log( $user_agent, 'user-agent' );
+			return static::block_and_log( $user_agent, 'user-agent' );
+		}
+
+		return false;
+	}
+
+	/**
+	 * Block by partial match of the user agent header
+	 *
+	 * @param string $user_agent_substring target user agent to be blocked.
+	 * @return void|bool
+	 */
+	public static function ua_partial_match( string $user_agent_substring ) {
+		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotValidated, WordPressVIPMinimum.Variables.RestrictedVariables.cache_constraints___SERVER__HTTP_USER_AGENT__, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
+		if ( isset( $_SERVER['HTTP_USER_AGENT'] ) && false !== strpos( $_SERVER['HTTP_USER_AGENT'], $user_agent_substring ) ) {
+			return static::block_and_log( $user_agent_substring, 'user-agent' );
 		}
 
 		return false;
@@ -95,7 +110,7 @@ public static function header( string $header, string $value ) {
 		$key = sprintf( 'HTTP_%s', str_ireplace( 'HTTP_', '', $key ) );
 
 		if ( isset( $_SERVER[ $key ] ) && $value === $_SERVER[ $key ] ) {
-			return self::block_and_log( $value, $header );
+			return static::block_and_log( $value, $header );
 		}
 
 		return false;

tests/lib/test-vip-request-block.php

@@ -11,7 +11,8 @@ class VIP_Request_Block_Test extends WP_UnitTestCase {
 	 */
 
 	public function tearDown(): void {
-		unset( $_SERVER['HTTP_TRUE_CLIENT_IP'], $_SERVER['HTTP_X_FORWARDED_FOR'] );
+		// phpcs:ignore WordPressVIPMinimum.Variables.RestrictedVariables.cache_constraints___SERVER__HTTP_USER_AGENT__
+		unset( $_SERVER['HTTP_TRUE_CLIENT_IP'], $_SERVER['HTTP_X_FORWARDED_FOR'], $_SERVER['HTTP_USER_AGENT'] );
 		parent::tearDown();
 	}
 
@@ -78,4 +79,16 @@ public function data_ipv6_corner_cases(): iterable {
 			[ 'HTTP_X_FORWARDED_FOR', '2001:4860:4860:0:0:0:0:8844', '2001:4860:4860:0000:0000:0000:0000:8844' ],
 		];
 	}
+
+	public function test_ua_partial_match() {
+		// Test that a partial match of the user agent string blocks bad site.
+		$_SERVER['HTTP_USER_AGENT'] = 'WordPress/6.1.1; https://www.BadSite.com'; // phpcs:ignore WordPressVIPMinimum.Variables.RestrictedVariables.cache_constraints___SERVER__HTTP_USER_AGENT__
+		$actual                     = VIP_Request_Block::ua_partial_match( 'https://www.BadSite.com' );
+		self::assertTrue( $actual, 'Expected request to be blocked based on partial User Agent string match.' );
+
+		// Test that allowed user agent string is not blocked.
+		$_SERVER['HTTP_USER_AGENT'] = 'WordPress/6.1.1; https://www.example.com'; // phpcs:ignore WordPressVIPMinimum.Variables.RestrictedVariables.cache_constraints___SERVER__HTTP_USER_AGENT__
+		$actual                     = VIP_Request_Block::ua_partial_match( 'https://www.BadSite.com' );
+		self::assertFalse( $actual, 'Expected request to be allowed.' );
+	}
 }