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<?php
/**
* Abstraction for checking files with an external virus scanner.
* Supports connections via TCP or socket and is focused on using ClamAV at the moment.
* Derived from https://github.com/nextcloud/files_antivirus
*
* @author Thomas Hackl <hackl@data-quest.de>
* @author Sebastian Biller <s.biller@tu-braunschweig.de>
* @license GPL 2 or later
* @since 5.3
*/
class Virusscanner
{
// Contains the singleton used.
protected static $instance;
// Definitions for possible status.
public const SCANRESULT_UNCHECKED = -1;
public const SCANRESULT_CLEAN = 0;
public const SCANRESULT_INFECTED = 1;
/**
* Scans the given path for viruses.
*
* @param string $path
* @return array Contains the found virus signature, error message or is an empty array on successful scan
*/
public static function scan(string $path): array
{
// Get virus scanner singleton.
if (is_null(static::$instance)) {
static::$instance = new static();
}
$scanner = static::$instance;
try {
// Connect to scanner.
$handle = $scanner->connect();
// Read file.
$file = $scanner->readFile($path);
// ClamAV has a maximum stream length, so we need to track how much data has already been sent.
$bytesWritten = $scanner->sendContent($handle, "nINSTREAM\n");
// Send file chunks via socket or TCP.
while ($chunk = @fread($file, 8192)) {
$chunkLength = pack('N', strlen($chunk));
// Send next chunk.
if ($bytesWritten + strlen($chunk) <= Config::get()->VIRUSSCAN_MAX_STREAMLENGTH) {
$bytesWritten += $scanner->sendContent($handle, $chunkLength . $chunk);
// Stream limit will be reached: abort.
} else {
return [
'error' => _('Die Datei ist zu groß, um vom Virenscanner gelesen zu werden.')
];
}
}
fclose($file);
// All chunks have been sent - signal stream end and get scanner response.
$result = $scanner->finalize($handle);
// Nothing found.
if ($result['status'] == static::SCANRESULT_CLEAN) {
return [];
// Virus found or error.
} else if ($result['status'] == static::SCANRESULT_INFECTED) {
return [
'found' => $result['details']
];
} else {
return [
'error' => $result['details']
];
}
// There has been an error: send error message back.
} catch (Exception $e) {
return [
'error' => $e->getMessage()
];
}
return [];
}
/**
* Finalized constructor so that the instantition in scan() will never fail.
*/
protected final function __construct()
{
}
/**
* Establishes a connection to virus scanner via socket or TCP, depending on Stud.IP configuration.
*
* @return resource|null
*/
protected function connect()
{
$handle = false;
// Use socket connection.
if (Config::get()->VIRUSSCAN_SOCKET) {
$handle = @stream_socket_client('unix://' . Config::get()->VIRUSSCAN_SOCKET, $errno, $errstr, 5);
// use TCP connection.
} else if (Config::get()->VIRUSSCAN_HOST && Config::get()->VIRUSSCAN_PORT) {
$handle = @fsockopen(Config::get()->VIRUSSCAN_HOST, Config::get()->VIRUSSCAN_PORT);
}
if ($handle === false) {
throw new RuntimeException(_('Der Virenscanner ist nicht verfügbar.'));
}
return $handle;
}
/**
* Get contents of the file to scan.
*
* @param string $path
* @return resource
*/
protected function readFile(string $path)
{
$handle = fopen($path, 'r');
if ($handle === false) {
throw new RuntimeException(_('Die Datei kann nicht gelesen werden.'));
}
return $handle;
}
/**
* Send some content to the virus scanner.
*
* @param resource $handle
* @param string $content
* @return int
*/
protected function sendContent($handle, string $content): int
{
$written = @fwrite($handle, $content);
// An error has happened -> throw exception.
if ($written === false) {
throw new RuntimeException(_('Fehler bei der Kommunikation mit dem Virenscanner.'));
// Return written byte count.
} else {
return $written;
}
}
/**
* All file chunks have been sent: we now signal the end of the stream by sending a "0".
* Afterwarda, the response we got from virus scanner is parsed and (in case something was found)
* the name of the virus is returned.
*
* @param resource $handle
* @return array
*/
protected function finalize($handle): array
{
// End stream to socket or TCP endpoint.
$this->sendContent($handle, pack('N', 0));
// Fetch virus scanner response.
$response = fgets($handle);
fclose($handle);
// Parse response.
$matches = [];
// Possible response types.
$rules = [
[
'match' => '/.*: OK$/',
'status' => self::SCANRESULT_CLEAN
],
[
'match' => '/.*: (.*) FOUND$/',
'status' => self::SCANRESULT_INFECTED
],
[
'match' => '/.*: (.*) ERROR$/',
'status' => self::SCANRESULT_UNCHECKED
],
];
$status = static::SCANRESULT_UNCHECKED;
$details = _('Die Antwort des Virenscanners wurde nicht erkannt.');
foreach ($rules as $rule) {
if (preg_match($rule['match'], $response, $matches)) {
$status = (int) $rule['status'];
if ((int) $rule['status'] !== static::SCANRESULT_CLEAN) {
$details = $matches[1] ?? _('unbekannt');
} else {
$details = '';
}
break;
}
}
return [
'status' => $status,
'details' => $details
];
}
}
|
