<?php
/* small API server that acts as a proxy to the dozmod server.
* To reduce the number of requests and connections to dozmod-server, results
* gets cached into a file cache.
*
* Required Configuration:
* CONFIG_DOZMOD_EXPIRE: Expiration time in seconds for the cache
* CONFIG_DOZMOD: URL to the dozmod server
*
**/
require 'modules/locations/inc/location.inc.php';
define('LIST_URL', CONFIG_DOZMOD . '/vmchooser/list');
define('VMX_URL', CONFIG_DOZMOD . '/vmchooser/lecture');
$availableRessources = ['vmx', 'test', 'netrules'];
/* BEGIN: A simple caching mechanism ---------------------------- */
function cache_hash($obj)
{
return md5(serialize($obj));
}
function cache_key_to_filename($key)
{
return "/tmp/bwlp-slxadmin-cache-$key"; // TODO: hash
}
function cache_put($key, $value)
{
$filename = cache_key_to_filename($key);
file_put_contents($filename, $value);
}
function cache_has($key)
{
$filename = cache_key_to_filename($key);
$mtime = filemtime($filename);
if (!$mtime) {
return false; // cache miss
}
if (time() - $mtime > CONFIG_DOZMOD_EXPIRE) {
return false;
} else {
return true;
}
}
function cache_get($key)
{
$filename = cache_key_to_filename($key);
return file_get_contents($filename);
}
/* good for large binary files */
function cache_get_passthru($key)
{
$filename = cache_key_to_filename($key);
$fp = fopen($filename, "r");
if ($fp) {
fpassthru($fp);
} else {
Util::traceError("cannot open file");
}
}
/* END: Cache ---------------------------------------------------- */
/* this script requires 2 (3 with implicit client ip) parameters
*
* resource = vmx,...
* lecture_uuid = client can choose
**/
function println($str) { echo "$str\n"; }
/* return an array of lecutre uuids.
* Parameter: an array with location Ids
* */
function _getLecturesForLocations($locationIds)
{
$ids = implode('%20', $locationIds);
$url = LIST_URL . "?locations=$ids";
$responseXML = Download::asString($url, 60, $code);
$xml = new SimpleXMLElement($responseXML);
$uuids = [];
foreach ($xml->eintrag as $e) {
$uuids[] = strval($e->uuid['param'][0]);
}
return $uuids;
}
/** Caching wrapper around _getLecturesForLocations() */
function getLecturesForLocations($locationIds)
{
$key = 'lectures_' . cache_hash($locationIds);
if (cache_has($key)) {
return unserialize(cache_get($key));
} else {
$value = _getLecturesForLocations($locationIds);
cache_put($key, serialize($value));
return $value;
}
}
function _getVMX($lecture_uuid)
{
$url = VMX_URL . '/' . $lecture_uuid;
$response = Download::asString($url, 60, $code);
return $response;
}
/** Caching wrapper around _getVMX() **/
function getVMX($lecture_uuid)
{
$key = 'vmx_' . $lecture_uuid;
if (cache_has($key)) {
cache_get_passthru($key);
} else {
$value = _getVMX($lecture_uuid);
cache_put($key, $value);
return $value;
}
}
// -----------------------------------------------------------------------------//
$ip = $_SERVER['REMOTE_ADDR'];
if (substr($ip, 0, 7) === '::ffff:') {
$ip = substr($ip, 7);
}
/* request data, don't trust */
$request = ['resource' => filter_var(strtolower(trim($_REQUEST['resource'])), FILTER_SANITIZE_STRING),
'lecture' => filter_var(strtolower(trim($_REQUEST['lecture'])), FILTER_SANITIZE_STRING),
'ip' => $ip];
/* lookup location id(s) */
$location_ids = Location::getFromIP($request['ip']);
/* lookup lecture uuids */
$lectures = getLecturesForLocations(array($location_ids));
/* validate request -------------------------------------------- */
/* check resources */
if (!in_array($request['resource'], $availableRessources)) {
Util::traceError("unknown resource: {$request['resource']}");
}
/* check that the user requests a lecture that he is allowed to have */
if (!in_array($request['lecture'], $lectures)) {
Util::traceError("client is not allowed to access this lecture: ${request['lecture']}");
}
if ($request['resource'] === 'vmx') {
echo getVMX($request['lecture']);
} else if ($request['resource'] === 'test') {
echo "Here's your special test data!";
} else {
echo "I don't know how to give you that resource";
}
