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PhabricatorRequestOverseer.php
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Mon, Feb 3, 11:39

PhabricatorRequestOverseer.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
final class PhabricatorRequestOverseer {
public function didStartup() {
$this->detectPostMaxSizeTriggered();
}
/**
* Detect if this request has had its POST data stripped by exceeding the
* 'post_max_size' PHP configuration limit.
*
* PHP has a setting called 'post_max_size'. If a POST request arrives with
* a body larger than the limit, PHP doesn't generate $_POST but processes
* the request anyway, and provides no formal way to detect that this
* happened.
*
* We can still read the entire body out of `php://input`. However according
* to the documentation the stream isn't available for "multipart/form-data"
* (on nginx + php-fpm it appears that it is available, though, at least) so
* any attempt to generate $_POST would be fragile.
*/
private function detectPostMaxSizeTriggered() {
// If this wasn't a POST, we're fine.
if ($_SERVER['REQUEST_METHOD'] != 'POST') {
return;
}
// If there's POST data, clearly we're in good shape.
if ($_POST) {
return;
}
// For HTML5 drag-and-drop file uploads, Safari submits the data as
// "application/x-www-form-urlencoded". For most files this generates
// something in POST because most files decode to some nonempty (albeit
// meaningless) value. However, some files (particularly small images)
// don't decode to anything. If we know this is a drag-and-drop upload,
// we can skip this check.
if (isset($_REQUEST['__upload__'])) {
return;
}
// PHP generates $_POST only for two content types. This routing happens
// in `main/php_content_types.c` in PHP. Normally, all forms use one of
// these content types, but some requests may not -- for example, Firefox
// submits files sent over HTML5 XMLHTTPRequest APIs with the Content-Type
// of the file itself. If we don't have a recognized content type, we
// don't need $_POST.
//
// NOTE: We use strncmp() because the actual content type may be something
// like "multipart/form-data; boundary=...".
//
// NOTE: Chrome sometimes omits this header, see some discussion in T1762
// and http://code.google.com/p/chromium/issues/detail?id=6800
$content_type = idx($_SERVER, 'CONTENT_TYPE', '');
$parsed_types = array(
'application/x-www-form-urlencoded',
'multipart/form-data',
);
$is_parsed_type = false;
foreach ($parsed_types as $parsed_type) {
if (strncmp($content_type, $parsed_type, strlen($parsed_type)) === 0) {
$is_parsed_type = true;
break;
}
}
if (!$is_parsed_type) {
return;
}
// Check for 'Content-Length'. If there's no data, we don't expect $_POST
// to exist.
$length = (int)$_SERVER['CONTENT_LENGTH'];
if (!$length) {
return;
}
// Time to fatal: we know this was a POST with data that should have been
// populated into $_POST, but it wasn't.
$config = ini_get('post_max_size');
$this->fatal(
"As received by the server, this request had a nonzero content length ".
"but no POST data.\n\n".
"Normally, this indicates that it exceeds the 'post_max_size' setting ".
"in the PHP configuration on the server. Increase the 'post_max_size' ".
"setting or reduce the size of the request.\n\n".
"Request size according to 'Content-Length' was '{$length}', ".
"'post_max_size' is set to '{$config}'.");
}
/**
* Defined in webroot/index.php.
* TODO: Move here.
*
* @phutil-external-symbol function phabricator_fatal
*/
public function fatal($message) {
phabricator_fatal('FATAL ERROR: '.$message);
}
}

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