Symptoms
When you attempt to access any of the following services on any version of the Windows 2003 Server family running Microsoft Internet Information Server (IIS) 6.0:
- Citrix ConfProxy ISAPI (C:\Inetpub\Scripts\ctxconfproxy.dll)
- Citrix STA ISAPI (C:\Inetpub\Scripts\ctxsta.dll)
- Citrix XML ISAPI (C:\Inetpub\Scripts\wpnbr.dll)
- Citrix XML Administration ISAPI (C:\Inetpub\Scripts\ctxadmin\ctxadmin.dll)
you may receive one of the following error messages:
- HTTP Error 404 – File not found
- HTTP Error 404 – File or directory not found
- The page cannot be found
Cause
Microsoft IIS 6.0 introduces new security features which limit the ability to execute code on the server. Web Service Extensions must be configured and/or enabled to serve dynamic content as by default IIS 6.0 will serve only static content (HTML).
Resolution
The following Web Service Extensions are installed, but disabled by default and can be enabled in the Add/Remove Programs dialog box:
- Active Server Pages (ASP)
- ASP.NET
- FrontPage Server Extensions 2002
- Internet Data Connector (IDC)
- Server Side Includes (SSI)
- Web Distributed Authoring and Versioning (WebDAV)
- Active Server Pages is required for Web Interface 2.0 and ASP.NET is required by Web Interface 3.0 and 4.0. The other extensions are not required and should be disabled unless required by other software.
- In addition to the above Web Service Extensions, the following Web Service Extensions can be activated in the IIS Manager console:
- All Unknown ISAPI Extensions (*.DLL)
- All Unknown CGI Extensions (*.EXE)
Other Web Service Extensions (including the Citrix ISAPI extensions listed above) can be manually configured as follows:
- Open the Internet Information Services (IIS) Manager console from the Administrative Tools folder.
- Open the target computer or select Connect… from the Action menu to administer a remote machine.
- Select Web Service Extensions in the left pane.
- Click Add a new Web service extension…
- Type the extension name (for example, Citrix XML ISAPI).
- Click Add… and type in or browse to the required DLL file (for example, C:\Inetpub\Scripts\wpnbr.dll).
- Select Set extension status to Allowed.
- Click OK.
- Repeat for each required Web Service Extension.
Provided you are aware of the potential security implications of doing so, an alternative solution is to enable “All Unknown ISAPI Extensions” (*.DLL):
- Open the Internet Information Services (IIS) Manager console from the Administrative Tools folder.
- Open the target computer or select Connect… from the Action menu to administer a remote machine.
- Select Web Service Extensions in the left pane.
- Select All Unknown ISAPI Extensions in the right pane.
- Click Allow in the right pane.
Status
This behavior is by design.
Issuing a HTTP 404 – File not found error rather than a more informative HTTP 403 – Forbidden or HTTP 500 – Internal Server Error avoids unnecessary information disclosure.
More Information
• "HTTP Error 404 - File or Directory not found" error message when you request dynamic content with IIS 6.0
• How to enable and disable ISAPI extensions and CGI applications in IIS 6.0
• IIS 6.0: Definition of Term Web Service Extension
