Auth::onRestCheckAuth

static function onRestCheckAuth(array $query, $scope, &$res)
{
	$authCode = null;
	foreach(static::$authQueryParams as $key)
	{
		if(array_key_exists($key, $query))
		{
			$authCode = $query[$key];
			break;
		}
	}

	if($authCode === null)
	{
		return null;
	}

	define('BX24_REST_SKIP_SEND_HEADERS', true);
	$origin = BitrixMainContext::getCurrent()->getServer()->get('HTTP_ORIGIN');
	if ($origin)
	{
		header('Access-Control-Allow-Origin: ' . $origin);
		header('Access-Control-Allow-Credentials: true');
	}

	global $USER;
	if (!$USER->IsAuthorized())
	{
		$USER->LoginByCookies();
	}

	if ($authCode == self::AUTH_CODE_GUEST)
	{
		if (self::checkQueryMethod(self::METHODS_WITHOUT_AUTH))
		{
			if ($USER->IsAuthorized())
			{
				if ($USER->GetParam('EXTERNAL_AUTH_ID') == User::EXTERNAL_AUTH_ID && mb_substr($USER->GetParam('XML_ID'), 0, mb_strlen(self::AUTH_TYPE)) == self::AUTH_TYPE)
				{
					$customAuthCode = BitrixMainApplication::getInstance()->getContext()->getRequest()->get(self::AUTH_CUSTOM_ID_PARAM);
					if ($customAuthCode && preg_match("/^[a-fA-F0-9]{32}$/i", $customAuthCode))
					{
						$res = self::getSuccessfulResult();
						return true;
					}
					else
					{
						$res = array(
							'error' => 'LIVECHAT_AUTH_WIDGET_USER',
							'error_description' => 'Livechat: you are authorized with a different user [1]',
							'additional' => array('hash' => mb_substr($USER->GetParam('XML_ID'), mb_strlen(self::AUTH_TYPE) + 1))
						);
						return false;
					}
				}
				else
				{
					$res = array(
						'error' => 'LIVECHAT_AUTH_PORTAL_USER',
						'error_description' => 'Livechat: you are authorized with a portal user [1]',
						'additional' => array()
					);
					return false;
				}
			}
			else
			{
				$res = self::getSuccessfulResult();
				return true;
			}
		}
		else
		{
			$res = array(
				'error' => 'LIVECHAT_AUTH_METHOD_ERROR',
				'error_description' => 'Livechat: you don't have access to use this method [1]',
				'additional' => array()
			);
			return false;
		}
	}
	else if (!preg_match("/^[a-fA-F0-9]{32}$/i", $authCode))
	{
		$res = array(
			'error' => 'LIVECHAT_AUTH_FAILED',
			'error_description' => 'LiveChat: user auth failed [code is not correct]',
			'additional' => array()
		);
	}
	else if ($_SESSION['LIVECHAT']['AUTH_ERROR_COUNTER'] > 3)
	{
		$res = array(
			'error' => 'LIVECHAT_AUTH_BLOCKED',
			'error_description' => 'LiveChat: user auth blocked',
			'additional' => array()
		);

		return false;
	}

	if (!self::checkQueryMethod(array_merge(self::METHODS_WITH_AUTH, self::METHODS_WITHOUT_AUTH)))
	{
		$res = array(
			'error' => 'LIVECHAT_AUTH_METHOD_ERROR',
			'error_description' => 'Livechat: you don't have access to use this method [2]',
			'additional' => array()
		);
		return false;
	}

	$xmlId = self::AUTH_TYPE."|".$authCode;

	if ($USER->IsAuthorized())
	{
		if ($USER->GetParam('EXTERNAL_AUTH_ID') == User::EXTERNAL_AUTH_ID)
		{
			if ($USER->GetParam('XML_ID') == $xmlId)
			{
				$res = self::getSuccessfulResult();

				CUser::SetLastActivityDate($USER->GetID(), true);

				return true;
			}
			else
			{
				$res = array(
					'error' => 'LIVECHAT_AUTH_WIDGET_USER',
					'error_description' => 'Livechat: you are authorized with a different user [2]',
					'additional' => array('hash' => mb_substr($USER->GetParam('XML_ID'), mb_strlen(self::AUTH_TYPE) + 1))
				);
				return false;
			}
		}
		else
		{
			$res = array(
				'error' => 'LIVECHAT_AUTH_PORTAL_USER',
				'error_description' => 'Livechat: you are authorized with a portal user [2]',
				'additional' => array()
			);
			return false;
		}
	}

	$userData = BitrixMainUserTable::getList([
		'select' => ['ID', 'EXTERNAL_AUTH_ID'],
		'filter' => ['=XML_ID' => $xmlId]
	])->fetch();

	if($userData && $userData['EXTERNAL_AUTH_ID'] == User::EXTERNAL_AUTH_ID)
	{
		self::authorizeById($userData['ID']);

		$res = self::getSuccessfulResult();

		CUser::SetLastActivityDate($USER->GetID(), true);

		return true;
	}

	$res = array(
		'error' => 'LIVECHAT_AUTH_FAILED',
		'error_description' => 'LiveChat: user auth failed [user not found]',
		'additional' => array()
	);

	if (
		$_SESSION['LIVECHAT']['AUTH_CODE']
		&& $_SESSION['LIVECHAT']['AUTH_CODE'] != $xmlId
	)
	{
		$_SESSION['LIVECHAT']['AUTH_ERROR_COUNTER'] += 1;
	}

	$_SESSION['LIVECHAT']['AUTH_CODE'] = $xmlId;

	return false;
}