[IronPython] Sandboxing using AppDomains

[Leo Carbajal]

Howdy all,

I know this is a topic that comes up again and again but I was hoping I
could get a bit of understanding from someone.

So, like many others, I'm looking to get IPy to work in a relatively safe
environment. My application is a game-server and exposes many entry points
for user created scripts to essentially extend the game's reactions. Because
these scripts are open to the public I need to be sure that it cannot do
nasty things like delete all the script files, my app or anything else on
the server, access my other non-exposed functions, etc.

Anyway, so after reading up a little on AppDomains it sounds like running
IPy through one could be a little prohibitive. I'm not really passing
value-types to work on, I'm allowing the scripts to directly access and
modify the objects themselves. I guess I'm not sure if what I want to do
will even work, and I haven't had a chance to put together a test. The use
of scripting in the application is extensive so I worry that I may have to
scale back - or risk having someone one day using a little reflection to
snoop out my app's API and calling functions that the scriptShell was never
intended to be able to use.

Would using permission.Deny for the permissions I want to disallow be enough
to keep things safe? I.E. something like:

//elsewhere
private static PermissionSet ps = new PermissionSet(PermissionState.None);
        ps.AddPermission(new
SecurityPermission(SecurityPermissionFlag.Execution));
        ps.AddPermission(new
FileIOPermission(FileIOPermissionAccess.PathDiscovery |
FileIOPermissionAccess.Read, Path));

public static void PlayFirstFile(Item caller)
        {
            locals.Add("Artifact", new ScriptableItem(caller));
            string script = (Path + "script.py");
            ps.Deny();
            engine.ExecuteFile(script, engine.DefaultModule, locals);
            locals.Clear();
        }

ScriptableItem, by the way, is a class wrapper to hide private methods in
Item after I found out that passing something as a template doesn't work to
occlude methods\properties I don't want called. =\

I'm a little lost when it comes to all this security stuff, I could really
use a bit of explanation and would really appreciate any help that can come
this way.

I'm using IronPython 1.1.2 as I haven't had the chance to sit down and
really play with 2.0, it seems a bit more convoluted to set-up but thats
entirely a from-the-outside perspective at the moment.

---
LC
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