CVE-2024-24752: Bref's Uploaded Files Not Deleted in Event-Driven Functions

(updated )

When Bref is used with the Event-Driven Function runtime and the handler is a RequestHandlerInterface, then the Lambda event is converted to a PSR7 object. During the conversion process, if the request is a MultiPart, each part is parsed and for each which contains a file, it is extracted and saved in /tmp with a random filename starting with bref_upload_.

The function implementing the logic follows:

private static function parseBodyAndUploadedFiles(HttpRequestEvent $event): array
{
$bodyString = $event->getBody();
$files = [];
$parsedBody = null;
$contentType = $event->getContentType();
if ($contentType !== null && $event->getMethod() === 'POST') {
if (str_starts_with($contentType, 'application/x-www-form-urlencoded')) {
parse_str($bodyString, $parsedBody);
} else {
$document = new Part("Content-type: $contentType\r\n\r\n" . $bodyString);
if ($document->isMultiPart()) {
$parsedBody = [];
foreach ($document->getParts() as $part) {
if ($part->isFile()) {
$tmpPath = tempnam(sys_get_temp_dir(), 'bref_upload_');
if ($tmpPath === false) {
throw new RuntimeException('Unable to create a temporary directory');
}
file_put_contents($tmpPath, $part->getBody());
$file = new UploadedFile($tmpPath, filesize($tmpPath), UPLOAD_ERR_OK, $part->getFileName(), $part->getMimeType());

self::parseKeyAndInsertValueInArray($files, $part->getName(), $file);
} else {
self::parseKeyAndInsertValueInArray($parsedBody, $part->getName(), $part->getBody());
}
}
}
}
}
return [$files, $parsedBody];
}

The flow mimics what plain PHP does but it does not delete the temporary files when the request has been processed.

References

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