Validate response (e.g. status code and content type)

[kesselb]

updater/lib/Updater.php

Lines 495 to 509 in e73aa39

	$response = curl_exec($curl);
	if ($response === false) {
	throw new \Exception('Could not do request to updater server: '.curl_error($curl));
	}
	curl_close($curl);
	// Response can be empty when no update is available
	if ($response === '') {
	return [];
	}
	$xml = simplexml_load_string($response);
	if ($xml === false) {
	throw new \Exception('Could not parse updater server XML response');
	}

simplexml_load_string expects a well-formed xml document.
We should use curl_getinfo to check for the status code and the content type before parsing it.

[come-nc]

#591 is about that I think