<?php
/**
 * @package		solo
 * @copyright	2014 Nicholas K. Dionysopoulos / Akeeba Ltd 
 * @license		GNU GPL version 3 or later
 */

namespace Solo\Application;

use Awf\Application\Application;
use Awf\Download\Download;
use Awf\Uri\Uri;
use Awf\User\Authentication;

class UserAuthenticationYubikey extends Authentication
{
	/**
	 * Is this user authenticated by this object? The $params array contains at least one key, 'password'.
	 *
	 * @param   array   $params    The parameters used in the authentication process
	 *
	 * @return  boolean  True if the user is authenticated (or this plugin doesn't apply), false otherwise
	 */
	public function onAuthentication($params = array())
	{
		$result = true;

		$userParams = $this->user->getParameters();

		if ($userParams->get('tfa.method', 'none') == 'yubikey')
		{
			$result = false;

			$secret = isset($params['secret']) ? $params['secret'] : '';

			if (!empty($secret))
			{
				$result = $this->validateYubikeyOTP($secret);
			}
		}

		return $result;
	}

	public function onTfaSave($tfaParams)
	{
		$tfaMethod = isset($tfaParams['method']) ? $tfaParams['method'] : '';

		if ($tfaMethod == 'yubikey')
		{
			// The YubiKey code set by the user in the form
			$newCode = isset($tfaParams['yubikey']) ? $tfaParams['yubikey'] : '';
			// The YubiKey code in the user object
			$oldCode = $this->user->getParameters()->get('tfa.yubikey', '');
			// What was the old TFA method?
			$oldTfaMethod = $this->user->getParameters()->get('tfa.method');

			if (($oldTfaMethod == 'yubikey') && ($newCode == $oldCode))
			{
				// We had already set up YubiKey and the code is unchanged. No change performed here.
				return true;
			}
			else
			{
				// Safe fallback until we can verify the new yubikey
				$this->user->getParameters()->set('tfa', null);
				$this->user->getParameters()->set('tfa.method', 'none');

				if (!empty($newCode) && $this->validateYubikeyOTP($newCode))
				{
					$this->user->getParameters()->set('tfa.method', 'yubikey');
					$this->user->getParameters()->set('tfa.yubikey', $newCode);
				}
			}
		}

		return true;
	}

	/**
	 * Validates a Yubikey OTP against the Yubikey servers
	 *
	 * @param   string  $otp  The OTP generated by your Yubikey
	 *
	 * @return  boolean  True if it's a valid OTP
	 */
	public function validateYubikeyOTP($otp)
	{
		$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;

		$http = new Download();
		$token = Application::getInstance()->getContainer()->session->getCsrfToken()->getValue();
		$nonce = md5($token . uniqid(rand()));
		$response = '';

		while (!$gotResponse && !empty($server_queue))
		{
			$server = array_shift($server_queue);

			$uri = new Uri('https://' . $server . '/wsapi/2.0/verify');

			// I don't see where this ID is used?
			$uri->setVar('id', 1);

			// The OTP we read from the user
			$uri->setVar('otp', $otp);

			// This prevents a REPLAYED_OTP status of the token doesn't change
			// after a user submits an invalid OTP
			$uri->setVar('nonce', $nonce);

			// Minimum service level required: 50% (at least 50% of the YubiCloud
			// servers must reply positively for the OTP to validate)
			$uri->setVar('sl', 50);

			// Timeou waiting for YubiCloud servers to reply: 5 seconds.
			$uri->setVar('timeout', 5);

			try
			{
				$response = $http->getFromURL($uri->toString());

				if (!empty($response))
				{
					$gotResponse = true;
				}
				else
				{
					continue;
				}
			}
			catch (\Exception $exc)
			{
				// No response, continue with the next server
				continue;
			}
		}

		// No server replied; we can't validate this OTP
		if (!$gotResponse)
		{
			return false;
		}

		// Parse response
		$lines = explode("\n", $response);
		$data = array();

		foreach ($lines as $line)
		{
			$line = trim($line);

			$parts = explode('=', $line, 2);

			if (count($parts) < 2)
			{
				continue;
			}

			$data[$parts[0]] = $parts[1];
		}

		// Validate the response - We need an OK message reply
		if ($data['status'] != 'OK')
		{
			return false;
		}

		// Validate the response - We need a confidence level over 50%
		if ($data['sl'] < 50)
		{
			return false;
		}

		// Validate the response - The OTP must match
		if ($data['otp'] != $otp)
		{
			return false;
		}

		// Validate the response - The token must match
		if ($data['nonce'] != $nonce)
		{
			return false;
		}

		return true;
	}
}