ASP.NET Identity Matrix

Overview

Principal objects implement the IPrincipal interface and represent the security context of the user on whose behalf the code is running. The principal object includes the user’s identity (as a contained IIdentity object) and any roles to which the user belongs.

ASP.NET provides the following principal and identity object implementations:

WindowsPrincipal and WindowsIdentity objects represent users who have been authenticated with Windows authentication. With these objects, the role list is automatically obtained from the set of Windows groups to which the Windows user belongs.
GenericPrincipal and GenericIdentity objects represent users who have been authenticated using Forms authentication or other custom authentication mechanisms. With these objects, the role list is obtained in a custom manner, typically from a database.
FormsIdentity and PassportIdentity objects represent users who have been authenticated with Forms and Passport authentication respectively.

The following tables illustrate, for a range of IIS authentication settings, the resultant identity that is obtained from each of the variables that maintain an IPrincipal and/or IIdentity object. The following abbreviations are used in the table:

HttpContext = HttpContext.Current.User, which returns an IPrincipal object that contains security information for the current Web request. This is the authenticated Web client.
WindowsIdentity = WindowsIdentity.GetCurrent(), which returns the identity of the security context of the currently executing Win32 thread.
Thread = Thread.CurrentPrincipal which returns the principal of the currently executing .NET thread which rides on top of the Win32 thread.

Table 1: IIS Anonymous Authentication
Web.config Settings	Variable Location	Resultant Identity
<identity impersonate="true"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	- MACHINE\IUSR_MACHINE -
<identity impersonate="false"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	- MACHINE\ASPNET -
<identity impersonate="true"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user MACHINE\IUSR_MACHINE Name provided by user
<identity impersonate="false"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user MACHINE\ASPNET Name provided by user

Table 2: IIS Basic Authentication
Web.config Settings	Variable Location	Resultant Identity
<identity impersonate="true"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	Domain\UserName Domain\UserName Domain\UserName
<identity impersonate="false"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	Domain\UserName MACHINE\ASPNET Domain\UserName
<identity impersonate="true"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user Domain\UserName Name provided by user
<identity impersonate="false"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user MACHINE\ASPNET Name provided by user

Table 3: IIS Digest Authentication
Web.config Settings	Variable Location	Resultant Identity
<identity impersonate="true"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	Domain\UserName Domain\UserName Domain\UserName
<identity impersonate="false"/> <authentication mode="Windows" />	HttpContext WindowsIdentity Thread	Domain\UserName MACHINE\ASPNET Domain\UserName
<identity impersonate="true"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user Domain\UserName Name provided by user
<identity impersonate="false"/> <authentication mode="Forms" />	HttpContext WindowsIdentity Thread	Name provided by user MACHINE\ASPNET Name provided by user

Table 4: IIS Integrated Windows
Web.config Settings	Variable Location	Resultant Identity
<identity impersonate=”true”/><authentication mode=”Windows” />	HttpContext WindowsIdentity Thread	Domain\UserNameDomain\UserNameDomain\UserName
<identity impersonate=”false”/> <authentication mode=”Windows” />	HttpContext WindowsIdentity Thread	Domain\UserNameMACHINE\ASPNETDomain\UserName
<identity impersonate=”true”/> <authentication mode=”Forms” />	HttpContext WindowsIdentity Thread	Name provided by userDomain\UserNameName provided by user
<identity impersonate=”false”/> <authentication mode=”Forms” />	HttpContext WindowsIdentity Thread	Name provided by user MACHINE\ASPNET Name provided by user