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Attempt by security transparent method to access security critical method

Last week I was spending some time integrating the Microsoft Enterprise Library Data Access Application Block with the MVC Mini Profiler.

After overriding some methods, I was ready to run my first test. But instead of getting some profiling results all I got was the following error message:

“Attempt by security transparent method 'Microsoft.Practices.EnterpriseLibrary.Data.Database.CreateConnection()' to access security critical method 'MvcMiniProfiler.MiniProfiler.get_Current()' failed.”

So why did I got this error and what does it mean?

Let me first tell you that the Enterprise Library assembly is marked with the AllowPartiallyTrustedCallersAttribute and uses the level 2 security transparency model.  Level 2 transparency causes all methods in AllowPartiallyTrustedCallers assemblies to become security transparent by default.

In .Net4.0 framework, security tranparency rules prevent any security transparent code to call into security critical code. In .Net4.0 default security transpareny of library assemblies is security critical. The Enterprise Library assembly is marked with AllowPartiallyTrustedCallers attribute. This explicitly tells the security framework that this library will accept calls from security transparent callers. But the assembly MvcMiniProfiler do not have AllowPartiallyTrustedCallers attribute on it. This means it will not allow partial trusted or untrusted code to call into it.

I solved the problem by forking the MvcMiniProfiler code and adding the AllowPartiallyTrustedCallers attribute on the assembly. Anyone who knows a better(read=more secure) alternative?

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