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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows Registry
If Internet Security and Acceleration (ISA) Server 2000 is chained to an upstream Web proxy server, you may receive incomplete HTML pages and random authentication prompts in the Web browser when you connect to secure HTTPS sites.
These symptoms may occur if the downstream ISA Server computer is configured to require Integrated proxy authentication and if the upstream Web proxy server is either configured to allow anonymous access or require proxy authentication (typically Basic proxy authentication). This problem occurs most frequently if you connect to a secure HTTPS site that uses a combination of HTTP and HTTPS links.
In certain circumstances, Web browsers may try to authenticate a connection with the downstream ISA Server computer that has already been authenticated with Integrated authentication. This may cause the downstream ISA Server computer to pass those credentials to the upstream Web proxy server. Because the credentials are for the downstream ISA Server computer and not for the upstream Web proxy server, the server returns a "407 Proxy authentication required" HTTP response. The downstream ISA Server computer then passes this HTTP response back to the Web browser, causing the authentication prompts on the client computer. Because the client cannot authenticate this request, incomplete HTML pages may result on the Web browser client.
This issue was resolved for outgoing HTTP requests in the following two ISA hotfixes, but not for outgoing HTTPS requests that use SSL tunneling. For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
317822 FIX: Problems with Web Browser if ISA Server 2000 Is Chained to an Upstream Web Proxy Server
297080 Incomplete HTML Pages and Random Authentication Prompts If ISA Server Is Chained to Upstream Proxy
You must install ISA Server Service Pack 1 (SP1) before you install the following hotfix. For additional informationabout how to obtain the latest ISA Server service pack, click the following article number to view the article in the Microsoft Knowledge Base:
313139 How to Obtain the Latest Internet Security and Acceleration Server 2000 Service Pack
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
Date Time Version Size File name ------------------------------------------------------- 02-Apr-2003 17:04 3.0.1200.261 178,448 Mspadmin.exe 02-Apr-2003 17:04 3.0.1200.261 101,136 Msphlpr.dll 02-Apr-2003 17:03 3.0.1200.261 391,440 W3proxy.exe 02-Apr-2003 17:04 3.0.1200.261 298,768 Wspsrv.exe
This fix also applies to the French, German, Spanish, and Japanese versions of ISA Server.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
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 install the fix, run the self-extracting file. You do not have to restart the ISA Server computer. If the computer is part of an ISA Server array, you do not have to shut down the whole array. You can still install this fix on a one-by-one basis.
To implement the functionality in this fix, create one of the following registry keys:
To revert to the original configuration, either remove the
registry value or change its data value to 0 (zero). After you make either change, restart the Web Proxy service.
Note You can only use this method if the upstream Web Proxy server is configured to use Basic proxy authentication and the downstream ISA Server's routing rule is configured to provide Basic authentication credentials to the upstream Web proxy server.