Remoting: Finding client AppDomain / Assembly from server AppDomain

Question

Hello,

I have an application with a server "AppDomain", which accepts calls from separate AppDomains (which host plugins, developed by other people and not trustworthy).

From the server AppDomain, I need to know which "Plugin" (AppDomain) is actually making the call, so that I can ensure that this plugin has access to the resource.

I could just pass in the credentials to the remoting method call, but I am concerned that in doing so that a crafty programmer of "Plugin A" may change the code so that it appears to be coming from "Plugin B".

I have looked into creating my own "ObjRef" implementation on the Server app, thinking that "ChannelInfo.ChannelData" may hold information on the client plugin making the call, and implemented the following code:

public int DomainId
    {
        get
        {
            int domainId = -1;

            // The type "System.Runtime.Remoting.Channels.CrossAppDomainData" is not Public,
            // so we have to use reflection to get access to it.
            for (int i = 0; i < ChannelInfo.ChannelData.Length; i++)
            {
                object o = ChannelInfo.ChannelData[i];
                if (o.ToString() == "System.Runtime.Remoting.Channels.CrossAppDomainData")
                {
                    System.Reflection.BindingFlags flags =
                        System.Reflection.BindingFlags.GetProperty
                        | System.Reflection.BindingFlags.Instance
                        | System.Reflection.BindingFlags.NonPublic;

                    domainId = (int)o.GetType().GetProperty("DomainID", flags).GetValue(o, null);
                }
            }
            return domainId;
        }
    }

But the DomainId retrieved by this is the same as the Servers AppDomain.CurrentDomain.Id, when I really want the Client (caller) AppDomain Id

It feels like this is too hard :-)

Any ideas?