Safe Impersonation With Whidbey

OdeToCode Links For March 27

OdeToCode Links — Mon, 28 Mar 2005 04:03:00 GMT

More on First Pass Exception Issues

.Net Security Blog — Thu, 31 Mar 2005 23:43:00 GMT

re: Safe Impersonation With Whidbey

Nicole Calinoiu — Fri, 01 Apr 2005 12:01:00 GMT

While the use of a delegate is certainly convenient for this sort of thing, it's potentially quite dangerous given that there's no guarantee that the caller actually chose the delegate implementation. (See http://blogs.msdn.com/ptorr/archive/2005/01/16/353816.aspx for a discussion by Peter Torr of a somewhat similar problem.) Since it's not possible to place a demand for SecurityPermission\UnmanagedCode on the delegate itself, this is more than a little tricky. Providing a wrapper that enables a demand when setting the delegate could help, but a naive caller would still be creating a security hole if it fails to use the wrapper as intended.

Constraining the delegate actions via use of PermitOnly would also be potentially helpful, but one would need to receive the accepted permission set from the caller in order to allow adequate flexibility, and the same "naive caller" problem rears its ugly head again. In addition, this approach would be completely useless when resources used by a particular implementation of the delegate are not protected by CAS.

Unfortunately, I just can't see any way to make this sort of thing safe for potentially naive callers. Unless there's some wonderful technique I'm missing, it would seem prudent to make this functionality accessible by only one's own code.

re: Safe Impersonation With Whidbey

shawnfa — Thu, 07 Apr 2005 01:04:46 GMT

Well, there's really no good way to ensure that the caller uses the class library as intended. The goal of the code isn't to allow arbitrary delegates to run in the impersonation context, but rather to be a wrapper around the high trust code which ensures that the impersonation is undone when the work completes.

-Shawn

re: Safe Impersonation With Whidbey

Gavin — Tue, 08 Aug 2006 18:05:57 GMT

Hey,

I'm writing an application that requires me to authenticate as windows user account user to perform part of a process before resetting back to it's original context.

Unfortunately I have no choice but to use C# exclusively. Your code uses some language specific classes that and so I am unable to directly translate into C#.

Is there a C# version available?

Many Thanks