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Q218756: Logon Privileges Required for Anonymous Access

Article: Q218756
Product(s): Internet Information Server
Version(s): 4.0
Operating System(s): 
Keyword(s): 
Last Modified: 02-MAY-2001

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The information in this article applies to:

- Microsoft Internet Information Server 4.0 
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SUMMARY
=======

Prior to IIS version 4.0, the administrator had to make sure the anonymous user
account passwords were the same in both the IIS Administration tool and the
Windows User Manager. Failure to do so lead to logon failures. To solve this
dilemma and make administration easier, Password Synchronization was introduced
in IIS 4.0.

Password synchronization uses a slightly different logon method (explained in a
moment) that has some side effects. By default, this option is enabled.

Not Enabling Password Synchronization

When this option is not enabled, IIS calls the LogonUser() API in Windows to log
the account on. It passes in the user name and password configured by the
administrator. If this matches the user name and password in Windows User
Manager, the account is successfully logged on, the security token is cached by
IIS, and the account is impersonated. This scenario logs the user account on
interactively (logged on locally).

Enabling Password Synchronization

Authentication is performed differently when Password Synchronization is enabled
because IIS has to inform Windows that the password is correct. A
subauthenticator can perform this task. Windows allows subauthenticators
(implemented as subauthentication DLLs) to be used in conjunction with the
normal Windows authentication system. This scenario logs the user account on as
a network logon.

IIS supplies a subauthentication DLL called IISsuba.dll. The function of this DLL
in terms of anonymous authentication is to verify that the password is correct
and then inform Windows that the password is valid and hence log the user on.

The Side Effect of Enabling Password Synchronization

Subauthentication DLLs require a network logon, which can have side effects
compared to a batch or interactive logon. The most notable is, in some cases,
the inability to access resources such as files or Microsoft Access databases on
a remote computer. If you see this problem, turn the Password Synch option off;
this will force IIS to use normal authentication and log the account on locally
(an interactive logon).

MORE INFORMATION
================

For more information about Windows subauthentication, see the Microsoft Platform
SDK and Microsoft Visual Studio 6.0 online product documentation. Visual Studio
6.0 ships with a subauthentication sample called SubAuth.

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

  Q216828 Password Synchronization/Allow IIS to Control Password May Cause
  Problems

Additional query words:

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Keywords          :  
Technology        : kbiisSearch kbiis400
Version           : :4.0
Issue type        : kbhowto

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