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<?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: URL to the dozmod server
*
**/
if (!Module::isAvailable('locations')) {
die('require locations module');
}
define('LIST_URL', CONFIG_DOZMOD_URL . '/vmchooser/list');
define('VMX_URL', CONFIG_DOZMOD_URL . '/vmchooser/lecture');
$availableRessources = ['list', 'vmx', 'test', 'netrules'];
/* BEGIN: A simple caching mechanism ---------------------------- */
function cache_hash($obj)
{
return md5(serialize($obj));
}
function cache_key_to_filename($key)
{
return "/tmp/bwlp-slxadmin-cache-$key";
}
function cache_put($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 === false) {
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);
exit;
}
error_log('Cannot passthrough cache file ' . $filename);
}
/* END: Cache ---------------------------------------------------- */
/* this script requires 2 (3 with implicit client ip) parameters
*
* resource = vmx,...
* lecture_uuid = client can choose
**/
/**
* Takes raw lecture list xml, returns array of uuids.
*
* @param string $responseXML XML from dozmod server
* @return array list of UUIDs, false on error
*/
function xmlToLectureIds($responseXML)
{
$xml = new SimpleXMLElement($responseXML);
if (!isset($xml->eintrag))
return [];
$uuids = [];
foreach ($xml->eintrag as $e) {
$uuids[] = strval($e->uuid['param'][0]);
}
return $uuids;
}
/** Caching wrapper around _getLecturesForLocations() */
function getListForLocations($locationIds, $raw)
{
/* if in any of the locations there is an exam active, consider the client
to be in "exam-mode" and only offer him exams (no lectures) */
$key = 'lectures_' . cache_hash($locationIds);
$examMode = false;
if (Module::isAvailable('exams')) {
$examMode = Exams::isInExamMode($locationIds);
if ($examMode) {
$key .= '_exams';
}
}
$rawKey = $key . '_raw';
if ($raw) {
Header('Content-Type: text/xml; charset=utf-8');
if (cache_has($rawKey)) {
cache_get_passthru($rawKey);
}
} elseif (cache_has($key)) {
return unserialize(cache_get($key));
}
// Not in cache
$url = LIST_URL . "?locations=" . implode('%20', $locationIds);
if ($examMode) {
$url .= '&exams';
}
$value = Download::asString($url, 60, $code);
if ($value === false)
return false;
cache_put($rawKey, $value);
$list = xmlToLectureIds($value);
cache_put($key, serialize($list));
if ($raw) {
die($value);
}
return $list;
}
function getLectureUuidsForLocations($locationIds)
{
return getListForLocations($locationIds, false);
}
function outputLectureXmlForLocation($locationIds)
{
return getListForLocations($locationIds, true);
}
function _getVMX($lecture_uuid)
{
$url = VMX_URL . '/' . $lecture_uuid;
$response = Download::asString($url, 60, $code);
return $response;
}
/** Caching wrapper around _getVMX() **/
function outputVMX($lecture_uuid)
{
$key = 'vmx_' . $lecture_uuid;
if (cache_has($key)) {
cache_get_passthru($key);
} else {
$value = _getVMX($lecture_uuid);
if ($value === false)
return false;
cache_put($key, $value);
die($value);
}
}
function fatalDozmodUnreachable()
{
Header('HTTP/1.1 504 Gateway Timeout');
die('Resource not available');
}
function readLectureParam()
{
global $location_ids;
$lecture = Request::get('lecture', false, 'string');
if ($lecture === false) {
Header('HTTP/1.1 400 Bad Request');
die('Missing lecture UUID');
}
$lectures = getLectureUuidsForLocations($location_ids);
if ($lectures === false) {
fatalDozmodUnreachable();
}
/* check that the user requests a lecture that he is allowed to have */
if (!in_array($lecture, $lectures)) {
Header('HTTP/1.1 403 Forbidden');
die("You don't have permission to access this lecture");
}
return $lecture;
}
// -----------------------------------------------------------------------------//
/* request data, don't trust */
$resource = Request::get('resource', false, 'string');
if ($resource === false) {
Util::traceError("you have to specify the 'resource' parameter");
}
if (!in_array($resource, $availableRessources)) {
Util::traceError("unknown resource: $resource");
}
$ip = $_SERVER['REMOTE_ADDR'];
if (substr($ip, 0, 7) === '::ffff:') {
$ip = substr($ip, 7);
}
/* lookup location id(s) */
$location_ids = Location::getFromIp($ip);
$location_ids = Location::getLocationRootChain($location_ids);
if ($resource === 'vmx') {
$lecture = readLectureParam();
outputVMX($lecture);
// outputVMX does not return on success
fatalDozmodUnreachable();
}
if ($resource === 'list') {
outputLectureXmlForLocation($location_ids);
// Won't return on success...
fatalDozmodUnreachable();
}
Header('HTTP/1.1 400 Bad Request');
die("I don't know how to give you that resource");
|
