Permissions

Permissions

EnginePermissions is a flags enum that restricts which system resources a script can access. Pass it when registering the standard library.

Registration

using DScript.Extras;

// Allow everything (default — equivalent to EnginePermissions.All)
new EngineFunctionLoader().RegisterFunctions(engine);

// Deny all privileged operations
new EngineFunctionLoader().RegisterFunctions(engine, EnginePermissions.None);

// Selective access
new EngineFunctionLoader().RegisterFunctions(engine,
    EnginePermissions.FileSystem | EnginePermissions.Network);

Flags

Flag	Guards
FileSystem	All fs.* operations (readFileSync, writeFileSync, mkdirSync, etc.)
Network	fetch(), http.createServer, net.createServer, net.createConnection
ProcessSpawn	child_process.execSync, spawnSync, exec, spawn
ProcessExit	process.exit()
EnvironmentVariables	process.env, process.getenv()
None	No privileged operations allowed
All	All operations allowed (default)

Behaviour on violation

Attempting a denied operation throws PermissionException, which derives from ScriptException and can be caught inside a script's try/catch:

try {
    var data = fs.readFileSync("/etc/passwd");
} catch (e) {
    console.log("denied:", e.message);
}

From C# it is also catchable as a PermissionException:

try
{
    engine.Run(program);
}
catch (PermissionException ex)
{
    Console.Error.WriteLine($"Permission denied: {ex.Message}");
}

Example: sandboxed evaluation

Run arbitrary user code with no system access at all:

var engine = new ScriptEngine();
new EngineFunctionLoader().RegisterFunctions(engine, EnginePermissions.None);
engine.SetTimeout(TimeSpan.FromSeconds(5));
engine.SetInstructionLimit(10_000_000);

try
{
    engine.Run(ScriptEngine.Compile(userCode));
}
catch (ScriptTimeoutException)   { /* killed by limit */ }
catch (PermissionException)       { /* tried to access system */ }
catch (JITException ex)           { /* script runtime error */ }