C# Sandboxed App Domains example

This is an example on how to create secure(1) sandboxed app domains in order to execute untrusted code safely(1)

(1): The "secureness"/"safety" of this code is entirely debatable, and not guaranteed. Don't hold me liable.

Granted permissions

The following permissions have been granted to the child domains:

• ReflectionPermissionFlag.MemberAccess
• SecurityPermissionFlag.Execution
• SecurityPermissionFlag.SerializationFormatter
• FileIOPermissionAccess.Read | FileIOPermissionAccess.PathDiscovery, in the directory of the client script
• FileIOPermissionAccess.Read | FileIOPermissionAccess.Write | FileIOPermissionAccess.Append | FileIOPermissionAccess.PathDiscovery, in the subdirectory "Data" from the client script's .dll

More explanation can be found under the CreatePermissionSet() method in ScriptInstance.cs

AppDomainToolkit

This project uses @jduv's AppDomainToolkit. Which makes it significantly easier to set up app domains like this.

Due to an issue discovered in the code, a custom compiled version of this library has been included (with permission) until the NuGet package gets updated. See issue #25.

Sample code

The sample code demonstrates a plugin script (CSharpSandbox.ClientScript) which gets loaded into the host (CSharpSandbox.Host), and there's an exposed API ClientApi.

The plugin script demonstrates a receiving an event, which gets handled in the restricted CSharpSandbox.ClientScript domain, and it calling a method on the API, which gets handled in the CSharpSandbox.Host domain.

This is done over a single object instance of ClientApi. The plugin script only knows about the IClientApi interface, which exposes the event and methods. But the actual instance is declared inside CSharpSandbox.Host.

Also any exceptions thrown while invoking events are caught, to prevent the host from crashing due to a plugin script, as demonstrated below.

.pfx password

In case you need it:

CSharpSandbox