Feature Request: Implement a restricted mode

I'm interested in using IronPython as a scripting language for my app, as I've done benchmarks on many popular .net scripting solutions and IronPython comes on top - and speed is important for this app. However security is also important. I would like to create a platform where users can share their scripts, but not if I cannot lock down the scripts from being able to make any system changes.

The biggest hurdle I'm up against is that IronPython is completely unrestricted. I have resorted to doing the following to sand box the app, without forking this code base.

• Modified the sys module to provide only a handful of its members
• Created a string list of built in modules to be restricted - based off what I found from IronPython.Modules. Modules like winreg, _thread i have restricted, where modules like time I've kept.
• Created my own import function of which is a copy-paste from source code with modifications to enforce the restricted modules.
• Removed some built-in methods. Such as open

I'm hoping this is enough, but I can't be sure. I'm also hoping that by restricting the builtins, i can use the standard library, and modules from the standard library that use the restricted functionality will just not work.

This issue is a request to implement such a mode in this project.

Start by reviewing the existing sys module, builtins, import, and IronPython.Modules behavior described in the issue, then determine which operations a restricted mode must prevent. Define the security boundary and supported restrictions before implementation; done means user scripts cannot make the specified system changes while permitted standard-library functionality remains usable.