Site Server Forms Authentication May Not Work in a Reverse Proxy Environment (242772)

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WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To enable the sending of absolute redirects, use the following steps:

1. Start Registry Editor (Regedt32.exe).
2. Locate the following key in the registry:

   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Site Server\3.0\P&M

3. On the Edit menu, click Add Value, and then add the following registry value:

   Value Name: UseAbsoluteRedirects
   Data Type: REG_DWORD
   Value: 1

4. Quit Registry Editor.

If the above value is not present, the code functions the same as in prior versions. In other words, it will continue using relative redirects.

Site Server Forms Authentication traps any unauthorized requests to pages on a virtual Web server and issues a redirect to the FormsLogin.asp page. The content of this redirect depends on where the FormsLogin.asp file is. By default, this is in _mem_bin in the root of the virtual Web server. This results in a redirect containing a header ref "Location: /_mem_bin/FormsLogin.asp," (a relative redirect) being sent back to the client. In a reverse proxy environment, the proxy server may have a number of mappings configured that parse and rewrite header information. For example, it intercepts any request from a client with a header containing the extranet FQDN and replaces it with the corresponding intranet site name. When you use the same Forms Authentication page for multiple virtual Web servers, a loss of information occurs on the site where the original request came from.