Auditing user identity in .NET - What's a good strategy?

Question

I'm sure it's a requirement many developers have faced before: business needs an audit trail to know who is performing actions in their system.

Regardless of how you choose store the audited information, the core of this problem is how to identify the current user.

I want to write components, ranging from small domain model classes to service components, all which can safely be called from any of the following host applications:

• A Windows desktop application.
• An ASP.NET website hosted in IIS.
• A WCF service hosted in IIS.
• A WCF service hosted in a Windows service.

Given the range of technologies, the various authentication models and having to account for the concept of an "anonymous" user, I'm not clear on a strategy to use to get the identity of whoever invoked my component in a centralised fashion.

Can any of you smart folk suggest an approach to tackle this?

Answer 1

The best approach, using the most current techniques, is probably to use Windows Identity Foundation.

WIF is designed to handle user identity issues across multiple technologies using .NET.

Answer 2

I would generally require that applications set Thread.CurrentPrincipal to a principal whose identity represents the current user. This can be done at application startup (using WindowsIdentity.GetCurrent()) in a client (WinForms or Console) app, from HttpContext.Current.User or Roles.GetCurrentUser() in an ASP.NET or WCF application hosted in IIS, etc.

Then in the lower level components you simply use Thread.CurrentPrincipal.Identity for auditing.

EDIT (In response to comment) - note that Thread.CurrentPrincipal.Identity has nothing to do with the security context of the thread: this is represented by the WindowsIdentity and can be retrieved using WindowsIdentity.GetCurrent and changed using WindowsIdentity.Impersonate.