<?PHP
/**
* Provides class MD_JAIL.
*/
declare(strict_types = 1);
/**
* A class that, once initialized, forces the programmer to make security instructions implicit.
* If an object of the class has been created, not specifying security instructions
* leads to an error.
* A restriction on basic file operations is not practical in an md context because of
* the way transations are loaded through MDTlLoader.
*/
final class MD_JAIL {
const STATUS_NONE = 0;
const STATUS_STARTED = 1;
const STATUS_SPECIFIED = 2; // Determines that everything is fine.
/** @var integer */
private int $_status = self::STATUS_NONE;
/**
* @var integer
* Maximum execution time in seconds.
*/
public int $max_execution_time;
/**
* @var string[]
* Specifies which paths may be used by this script.
*/
private array $_open_basedir = [];
/**
* @var string
* Specifies the maximum RAM the script may use.
*/
public string $memory_limit;
/**
* Static function providing an advisory on how to harden the php.ini or
* .user.ini.
*
* @param array{shell_access_whitelist: string[], sys_function_whitelist: string[], file_function_whitelist: string[], file_uploads: bool, allow_url_fopen: bool, max_input_vars: integer, max_input_nesting_level: integer, post_max_size: string, curl: bool} $requested_resources Requested resources.
*
* @return string
*/
public static function check_server_setup(array $requested_resources):string {
# ini_set("open_basedir", __DIR__ . "/../../");
$disable_functions = [
"dl", # Loads a PHP extension at runtime
"opcache_get_status", # Gets opcache status
"phpinfo", # For obvious reasons
"parse_ini_file", # For obvious reasons
"show_source", "highlight_file", # Aliases; serve the content of a PHP file
"php_uname", # Returns information about the operating system PHP is running on
"phpcredits", # Credits page of PHP authors
"php_strip_whitespace", # Return PHP source with stripped comments and whitespace
"popen", "pclose", # Similar to fopen, but capable of shell access
"virtual", # Perform an Apache sub-request
];
$disable_aliases = [
"ini_set" => "ini_alter", # Alias of ini_set(), ini_set is preferred
"disk_free_space" => "diskfreespace", # Alias of disk_free_space()
"PHP_SAPI" => "php_sapi_name", # Alias of constant PHP_SAPI
"stream_set_write_buffer" => "set_file_buffer", # Alias of stream_set_write_buffer()
];
$shell_access_functions = array_diff(["exec", "passthru", "proc_close", "proc_get_status", "proc_nice", "proc_open", "proc_terminate", "shell_exec", "system"], $requested_resources['shell_access_whitelist']);
$sys_functions = array_diff(["get_current_user", "getmyuid", "getmygid", "getmypid", "getmyinode", "getlastmod", "getenv", "putenv"], $requested_resources['sys_function_whitelist']);
$file_functions = array_diff(["chgrp", "chgrp", "lchgrp", "lchown", "link", "linkinfo", "symlink"], $requested_resources['file_function_whitelist']);
if ($requested_resources['curl'] === false) {
$disable_functions[] = "curl_init";
$disable_functions[] = "curl_exec";
$disable_functions[] = "curl_multi_init";
$disable_functions[] = "curl_multi_exec";
}
$disabledWOAliases = array_merge($disable_functions, $shell_access_functions, $sys_functions, $file_functions);
$output = '## php.ini' . PHP_EOL . PHP_EOL;
$output .= PHP_EOL . "php_value[disable_functions] = \"" . implode(", ", array_merge($disabledWOAliases, $disable_aliases)) . "\"";
if ($requested_resources['file_uploads'] === false) {
$output .= PHP_EOL . "php_value[file_uploads] = 0";
}
if ($requested_resources['allow_url_fopen'] === false) {
$output .= PHP_EOL . "php_value[allow_url_fopen] = 0";
}
$output .= PHP_EOL . PHP_EOL . '## .user.ini' . PHP_EOL;
if ($requested_resources['file_uploads'] === false) {
$output .= PHP_EOL . "upload_max_filesize = 1";
}
if ($requested_resources['max_input_vars'] != ini_get("max_input_vars")) {
$output .= PHP_EOL . "max_input_vars = " . $requested_resources['max_input_vars'];
}
if ($requested_resources['max_input_nesting_level'] != ini_get("max_input_nesting_level")) {
$output .= PHP_EOL . "max_input_nesting_level = " . $requested_resources['max_input_nesting_level'];
}
if ($requested_resources['post_max_size'] != ini_get("post_max_size")) {
$output .= PHP_EOL . "post_max_size = " . $requested_resources['post_max_size'];
}
$output .= PHP_EOL . PHP_EOL . '## PHPStan Directives' . PHP_EOL . PHP_EOL . " disallowedFunctionCalls:" . PHP_EOL;
foreach ($disable_aliases as $to_keep => $disabled) {
$output .= '
-
function: \'' . $disabled . '()\'
message: \'use ' . $to_keep . ' instead\'';
}
foreach ($disabledWOAliases as $disabled) {
$output .= '
- function: \'' . $disabled . '()\'';
}
return $output;
}
/**
* Registers an additional accessible directory for open_basedir.
*
* @param string $dir Directory to register.
*
* @return void
*/
public function register_accessible_dir(string $dir):void {
$this->_open_basedir[] = $dir;
}
/**
* Applies the memory limit setting.
*
* @return void
*/
private function _apply_memory_limit():void {
if (!isset($this->memory_limit)) {
throw new MDJailSecurityOptionNotSetException("It has not been specified, which memory limit the script should hold. Set MD_JAIL->memory_limit = string.");
}
if (ini_set("memory_limit", $this->memory_limit) === false) {
throw new Exception('Failed to change memory_limit to ' . $this->memory_limit);
}
}
/**
* Applies the maximum execution time setting.
*
* @return void
*/
private function _apply_time_limit():void {
if (!isset($this->max_execution_time)) {
throw new MDJailSecurityOptionNotSetException("It has not been specified, which maximum execution time the script should hold. Set MD_JAIL->max_execution_time = integer.");
}
if (set_time_limit($this->max_execution_time) === false) {
throw new Exception('Failed to change max_execution_time to ' . $this->max_execution_time);
}
}
/**
* Applies basedir restrictions.
*
* @return void
*/
private function _apply_basedir_restriction():void {
if (empty($this->_open_basedir)) {
throw new MDJailSecurityOptionNotSetException("It has not been specified, which memory limit the script should hold. Set MD_JAIL->open_basedir = string.");
}
if (ini_set("open_basedir", implode(':', $this->_open_basedir)) === false) {
throw new Exception('Failed to set open_basedir restrictions');
}
}
/**
* Enforces security options previously set.
*
* @return void
*/
public function enforce():void {
// Special instructions on CLI, so as to not disturb PHPUnit
if (PHP_SAPI === 'cli') {
if (!isset($this->memory_limit)) {
throw new MDJailSecurityOptionNotSetException("It has not been specified, which memory limit the script should hold. Set MD_JAIL->memory_limit = string.");
}
if (!isset($this->max_execution_time)) {
throw new MDJailSecurityOptionNotSetException("It has not been specified, which maximum execution time the script should hold. Set MD_JAIL->max_execution_time = integer.");
}
$this->_status = self::STATUS_SPECIFIED;
$this->__destruct();
}
$this->_apply_memory_limit();
$this->_apply_time_limit();
// Set accessible file paths
$this->_apply_basedir_restriction();
$this->_status = self::STATUS_SPECIFIED;
$this->__destruct();
}
/**
* Setup function. Registers a shutdown function that throws an error
* if the security specifications have not been made.
*
* @return void
*/
public function __construct() {
$this->_status = self::STATUS_STARTED;
}
public function __destruct() {
if ($this->_status !== self::STATUS_SPECIFIED) {
echo "Security specifications need to be set.";
if (!isset($this->memory_limit)) {
echo "Set memory limit";
}
if (!isset($this->max_execution_time)) {
echo "Set max_execution_time";
}
if (empty($this->_open_basedir)) {
echo "Set open_basedir";
}
throw new MDJailSecurityOptionNotSetException("Security specifications need to be set.");
}
}
}