Adding support for custom YubiKey validation server

administrator/language/en-GB/en-GB.plg_twofactorauth_yubikey.ini

@@ -5,6 +5,8 @@
 
 PLG_TWOFACTORAUTH_YUBIKEY="Two Factor Authentication - YubiKey"
 
+PLG_TWOFACTORAUTH_YUBIKEY_CUSTOMSERVER_DESC="Enter the full URL of your custom validation server, e.g. <tt>http://www.example.com/mykeyserver/wsapi/2.0/verify</tt>. Custom validation servers can be created by using the Free and Open Source Software published by YubiCo at http://www.yubico.com/develop/open-source-software/validation-server/ Leave this blank if you want to use the public YubiCloud servers (default) or if you are not sure what this option means."
+PLG_TWOFACTORAUTH_YUBIKEY_CUSTOMSERVER_LABEL="Custom validation server"
 PLG_TWOFACTORAUTH_YUBIKEY_ERR_VALIDATIONFAILED="You did not enter a valid YubiKey secret code or the YubiCloud servers are unreachable at this time."
 PLG_TWOFACTORAUTH_YUBIKEY_INTRO="This feature allows you to use a YubiKey secure hardware token for two factor authentication. On top of your username and password you will also need to insert your YubiKey in your computer's USB port, click inside the Secret Key area of the site's login area and touch YubiKey's gold disk. The secret code generated by your YubiKey is unique to your device and changes constantly. This provides extra protection against hackers logging in to your account even if they were able to get hold of your password."
 PLG_TWOFACTORAUTH_YUBIKEY_METHOD_TITLE="YubiKey"

plugins/twofactorauth/yubikey/yubikey.php

@@ -280,12 +280,22 @@ public function onUserTwofactorAuthenticate($credentials, $options)
 	 */
 	public function validateYubikeyOTP($otp)
 	{
-		$server_queue = array(
-			'api.yubico.com', 'api2.yubico.com', 'api3.yubico.com',
-			'api4.yubico.com', 'api5.yubico.com'
-		);
+		$customURL = $this->params->get('customserver', '');
+		$customURL = trim($customURL);
 
-		shuffle($server_queue);
+		if (!empty($customURL))
+		{
+			$server_queue = array($customURL);
+		}
+		else
+		{
+			$server_queue = array(
+				'api.yubico.com', 'api2.yubico.com', 'api3.yubico.com',
+				'api4.yubico.com', 'api5.yubico.com'
+			);
+
+			shuffle($server_queue);
+		}
 
 		$gotResponse = false;
 		$check = false;
@@ -299,7 +309,14 @@ public function validateYubikeyOTP($otp)
 		{
 			$server = array_shift($server_queue);
 
-			$uri = new JUri('https://' . $server . '/wsapi/2.0/verify');
+			if (!empty($customURL))
+			{
+				$uri = new JUri($server);
+			}
+			else
+			{
+				$uri = new JUri('https://' . $server . '/wsapi/2.0/verify');
+			}
 
 			// I don't see where this ID is used?
 			$uri->setVar('id', 1);

plugins/twofactorauth/yubikey/yubikey.xml

@@ -33,6 +33,11 @@
 					<option value="2">PLG_TWOFACTORAUTH_YUBIKEY_SECTION_ADMIN</option>
 					<option value="3">PLG_TWOFACTORAUTH_YUBIKEY_SECTION_BOTH</option>
 				</field>
+
+                <field name="customserver" type="text"
+                       default=""
+                       description="PLG_TWOFACTORAUTH_YUBIKEY_CUSTOMSERVER_DESC"
+                       label="PLG_TWOFACTORAUTH_YUBIKEY_CUSTOMSERVER_LABEL" />
 			</fieldset>
 		</fields>
 	</config>