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293 lines
12 KiB
293 lines
12 KiB
2 years ago
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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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/**
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* ClamAV antivirus integration.
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*
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* @package antivirus_clamav
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* @copyright 2015 Ruslan Kabalin, Lancaster University.
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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namespace antivirus_clamav;
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defined('MOODLE_INTERNAL') || die();
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/** Default socket timeout */
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define('ANTIVIRUS_CLAMAV_SOCKET_TIMEOUT', 10);
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/** Default socket data stream chunk size */
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define('ANTIVIRUS_CLAMAV_SOCKET_CHUNKSIZE', 1024);
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/**
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* Class implementing ClamAV antivirus.
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* @copyright 2015 Ruslan Kabalin, Lancaster University.
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class scanner extends \core\antivirus\scanner {
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/**
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* Are the necessary antivirus settings configured?
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*
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* @return bool True if all necessary config settings been entered
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*/
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public function is_configured() {
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if ($this->get_config('runningmethod') === 'commandline') {
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return (bool)$this->get_config('pathtoclam');
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} else if ($this->get_config('runningmethod') === 'unixsocket') {
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return (bool)$this->get_config('pathtounixsocket');
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}
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return false;
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}
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/**
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* Scan file.
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*
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* This method is normally called from antivirus manager (\core\antivirus\manager::scan_file).
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*
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* @param string $file Full path to the file.
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* @param string $filename Name of the file (could be different from physical file if temp file is used).
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* @return int Scanning result constant.
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*/
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public function scan_file($file, $filename) {
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if (!is_readable($file)) {
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// This should not happen.
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debugging('File is not readable.');
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return self::SCAN_RESULT_ERROR;
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}
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// Execute the scan using preferable method.
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$method = 'scan_file_execute_' . $this->get_config('runningmethod');
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if (!method_exists($this, $method)) {
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throw new \coding_exception('Attempting to call non-existing method ' . $method);
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}
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$return = $this->$method($file);
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if ($return === self::SCAN_RESULT_ERROR) {
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$this->message_admins($this->get_scanning_notice());
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// If plugin settings require us to act like virus on any error,
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// return SCAN_RESULT_FOUND result.
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if ($this->get_config('clamfailureonupload') === 'actlikevirus') {
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return self::SCAN_RESULT_FOUND;
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}
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}
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return $return;
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}
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/**
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* Scan data.
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*
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* @param string $data The variable containing the data to scan.
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* @return int Scanning result constant.
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*/
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public function scan_data($data) {
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// We can do direct stream scanning if unixsocket running method is in use,
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// if not, use default process.
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if ($this->get_config('runningmethod') === 'unixsocket') {
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$return = $this->scan_data_execute_unixsocket($data);
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if ($return === self::SCAN_RESULT_ERROR) {
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$this->message_admins($this->get_scanning_notice());
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// If plugin settings require us to act like virus on any error,
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// return SCAN_RESULT_FOUND result.
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if ($this->get_config('clamfailureonupload') === 'actlikevirus') {
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return self::SCAN_RESULT_FOUND;
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}
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}
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return $return;
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} else {
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return parent::scan_data($data);
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}
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}
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/**
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* Returns the string equivalent of a numeric clam error code
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*
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* @param int $returncode The numeric error code in question.
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* @return string The definition of the error code
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*/
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private function get_clam_error_code($returncode) {
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$returncodes = array();
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$returncodes[0] = 'No virus found.';
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$returncodes[1] = 'Virus(es) found.';
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$returncodes[2] = ' An error occured'; // Specific to clamdscan.
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// All after here are specific to clamscan.
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$returncodes[40] = 'Unknown option passed.';
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$returncodes[50] = 'Database initialization error.';
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$returncodes[52] = 'Not supported file type.';
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$returncodes[53] = 'Can\'t open directory.';
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$returncodes[54] = 'Can\'t open file. (ofm)';
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$returncodes[55] = 'Error reading file. (ofm)';
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$returncodes[56] = 'Can\'t stat input file / directory.';
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$returncodes[57] = 'Can\'t get absolute path name of current working directory.';
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$returncodes[58] = 'I/O error, please check your filesystem.';
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$returncodes[59] = 'Can\'t get information about current user from /etc/passwd.';
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$returncodes[60] = 'Can\'t get information about user \'clamav\' (default name) from /etc/passwd.';
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$returncodes[61] = 'Can\'t fork.';
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$returncodes[63] = 'Can\'t create temporary files/directories (check permissions).';
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$returncodes[64] = 'Can\'t write to temporary directory (please specify another one).';
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$returncodes[70] = 'Can\'t allocate and clear memory (calloc).';
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$returncodes[71] = 'Can\'t allocate memory (malloc).';
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if (isset($returncodes[$returncode])) {
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return $returncodes[$returncode];
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}
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return get_string('unknownerror', 'antivirus_clamav');
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}
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/**
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* Scan file using command line utility.
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*
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* @param string $file Full path to the file.
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* @return int Scanning result constant.
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*/
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public function scan_file_execute_commandline($file) {
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$pathtoclam = trim($this->get_config('pathtoclam'));
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if (!file_exists($pathtoclam) or !is_executable($pathtoclam)) {
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// Misconfigured clam, notify admins.
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$notice = get_string('invalidpathtoclam', 'antivirus_clamav', $pathtoclam);
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$this->set_scanning_notice($notice);
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return self::SCAN_RESULT_ERROR;
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}
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$clamparam = ' --stdout ';
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// If we are dealing with clamdscan, clamd is likely run as a different user
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// that might not have permissions to access your file.
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// To make clamdscan work, we use --fdpass parameter that passes the file
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// descriptor permissions to clamd, which allows it to scan given file
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// irrespective of directory and file permissions.
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if (basename($pathtoclam) == 'clamdscan') {
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$clamparam .= '--fdpass ';
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}
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// Execute scan.
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$cmd = escapeshellcmd($pathtoclam).$clamparam.escapeshellarg($file);
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exec($cmd, $output, $return);
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// Return variable will contain execution return code. It will be 0 if no virus is found,
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// 1 if virus is found, and 2 or above for the error. Return codes 0 and 1 correspond to
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// SCAN_RESULT_OK and SCAN_RESULT_FOUND constants, so we return them as it is.
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// If there is an error, it gets stored as scanning notice and function
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// returns SCAN_RESULT_ERROR.
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if ($return > self::SCAN_RESULT_FOUND) {
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$notice = get_string('clamfailed', 'antivirus_clamav', $this->get_clam_error_code($return));
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$notice .= "\n\n". implode("\n", $output);
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$this->set_scanning_notice($notice);
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return self::SCAN_RESULT_ERROR;
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}
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return (int)$return;
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}
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/**
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* Scan file using Unix domain sockets.
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*
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* @param string $file Full path to the file.
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* @return int Scanning result constant.
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*/
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public function scan_file_execute_unixsocket($file) {
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$socket = stream_socket_client('unix://' . $this->get_config('pathtounixsocket'),
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$errno, $errstr, ANTIVIRUS_CLAMAV_SOCKET_TIMEOUT);
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if (!$socket) {
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// Can't open socket for some reason, notify admins.
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$notice = get_string('errorcantopensocket', 'antivirus_clamav', "$errstr ($errno)");
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$this->set_scanning_notice($notice);
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return self::SCAN_RESULT_ERROR;
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} else {
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// Execute scanning. We are running SCAN command and passing file as an argument,
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// it is the fastest option, but clamav user need to be able to access it, so
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// we give group read permissions first and assume 'clamav' user is in web server
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// group (in Debian the default webserver group is 'www-data').
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// Using 'n' as command prefix is forcing clamav to only treat \n as newline delimeter,
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// this is to avoid unexpected newline characters on different systems.
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$perms = fileperms($file);
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chmod($file, 0640);
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fwrite($socket, "nSCAN ".$file."\n");
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$output = stream_get_line($socket, 4096);
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fclose($socket);
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// After scanning we revert permissions to initial ones.
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chmod($file, $perms);
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// Parse the output.
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return $this->parse_unixsocket_response($output);
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}
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}
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/**
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* Scan data using unix socket.
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*
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* We are running INSTREAM command and passing data stream in chunks.
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* The format of the chunk is: <length><data> where <length> is the size of the following
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* data in bytes expressed as a 4 byte unsigned integer in network byte order and <data>
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* is the actual chunk. Streaming is terminated by sending a zero-length chunk.
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* Do not exceed StreamMaxLength as defined in clamd.conf, otherwise clamd will
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* reply with INSTREAM size limit exceeded and close the connection.
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*
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* @param string $data The varaible containing the data to scan.
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* @return int Scanning result constant.
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*/
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public function scan_data_execute_unixsocket($data) {
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$socket = stream_socket_client('unix://' . $this->get_config('pathtounixsocket'), $errno, $errstr, ANTIVIRUS_CLAMAV_SOCKET_TIMEOUT);
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if (!$socket) {
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// Can't open socket for some reason, notify admins.
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$notice = get_string('errorcantopensocket', 'antivirus_clamav', "$errstr ($errno)");
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$this->set_scanning_notice($notice);
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return self::SCAN_RESULT_ERROR;
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} else {
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// Initiate data stream scanning.
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// Using 'n' as command prefix is forcing clamav to only treat \n as newline delimeter,
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// this is to avoid unexpected newline characters on different systems.
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fwrite($socket, "nINSTREAM\n");
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// Send data in chunks of ANTIVIRUS_CLAMAV_SOCKET_CHUNKSIZE size.
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while (strlen($data) > 0) {
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$chunk = substr($data, 0, ANTIVIRUS_CLAMAV_SOCKET_CHUNKSIZE);
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$data = substr($data, ANTIVIRUS_CLAMAV_SOCKET_CHUNKSIZE);
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$size = pack('N', strlen($chunk));
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fwrite($socket, $size);
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fwrite($socket, $chunk);
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}
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// Terminate streaming.
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fwrite($socket, pack('N', 0));
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$output = stream_get_line($socket, 4096);
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fclose($socket);
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// Parse the output.
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return $this->parse_unixsocket_response($output);
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}
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}
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/**
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* Parse unix socket command response.
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*
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* @param string $output The unix socket command response.
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* @return int Scanning result constant.
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*/
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private function parse_unixsocket_response($output) {
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$splitoutput = explode(': ', $output);
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$message = trim($splitoutput[1]);
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if ($message === 'OK') {
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return self::SCAN_RESULT_OK;
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} else {
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$parts = explode(' ', $message);
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$status = array_pop($parts);
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if ($status === 'FOUND') {
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return self::SCAN_RESULT_FOUND;
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} else {
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$notice = get_string('clamfailed', 'antivirus_clamav', $this->get_clam_error_code(2));
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$notice .= "\n\n" . $output;
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$this->set_scanning_notice($notice);
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return self::SCAN_RESULT_ERROR;
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}
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}
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}
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}
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