ISA Server 2000, ISA Server 2004, ISA Server 2006, and Threat Management Gateway Server force CERN FTP connections to the root directory

By using a Web browser to connect to an FTP site, a user may unexpectedly be connected to the root directory of the FTP server. Or, the user may not be able to access a directory if a URL path is specified.

This issue may occur if the Web browser is configured to use Microsoft Internet Security and Acceleration (ISA) Server 2000 as a Web proxy for FTP requests -- specifically, when the FTP server requires the user to authenticate, and the server is configured to put the user in a directory that is relative to the root of the FTP server. For authenticated users, the FTP implementation in Microsoft Internet Information Server (IIS) 4.0 and in Microsoft Internet Information Services (IIS) 5.0 tries to change the remote directory to either a directory or a virtual directory that matches the user's name. If such a directory exists, the user is put in this directory, and this directory is relative to the FTP server's root directory. Administrators may use this method to put users in their respective home directories and in this way partly sandbox users.

However, users are not restricted from changing to the root directory of the FTP server in this scenario. A user who uses a Web browser to connect to an FTP server that uses IIS 4.0 and IIS 5.0 functionality may instead end up in the FTP root directory and, for example, see a list of other users' home directories. If virtual directories are used, the user's home directory may not appear in the list unless a matching directory exists in the FTP root.

Note The FTP implementation in IIS 6.0 supports a new feature that is named User Isolation. This feature permits the administrator to fully sandbox users. Users who connect to an FTP server that is running IIS 6.0 (or to a server that supports similar user isolation) will not be affected by the issue that is described in the "Symptoms" section. The reason for this is that IIS 6.0 users are put in their own respective root directories and not in any directory that is relative to the root of their respective FTP servers.

ISA Server issues a CWD /path command immediately after a successful logon, where the path portion of the command is the path portion of the URL. The problem that is described in the "Symptoms" section occurs because ISA Server does not drop the leading slash mark (/) from the path. RFC 1738 Section 3.1 specifies that the slash mark that appears between the host (or the port) and the URL path is not part of the URL path. ISA Server is not compliant with RFC 1738, because it uses the leading slash mark (/) as part of the path. Therefore, ISA Server issues the initial CWD command as �/path/path� instead of as �path/path� as specified in RFC 1738.

Note Most authenticated FTP servers can be expected to use a directory that is relative to a particular user's user name for an authenticated user's FTPRoot directory.

Users may be able to work around this issue by including the relative directory path in the request. For example, a user who wants to connect to an FTP server and be put in the "sub-dir" directory (sub-dir is relative to the user's home directory) must use the following request: If the relative path is different from the user name, the user can use a command-line FTP client such as FTP.EXE to connect to the FTP server and issue a PWD command. The PWD command will return the current directory relative to the FTP server's root.

Hotfix information

Note This fix is already included in ISA Server 2004, ISA Server 2006, and TMG RTM. However, it must be activated by configuring the registry subkey.

For more information about how to obtain the latest ISA Server 2000 service pack , click the following article number to view the article in the Microsoft Knowledge Base: A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problemP1 that P2 described in this article. Apply this hotfix only to systems that are experiencing the problemP1 described in this article. 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 hotfix has the file attributes (or later file attributes) 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 item in Control Panel.Note You must install ISA Server Service Pack 1 (SP1) before you install the following hotfix. This hotfix also applies to the French, the German, the Spanish, and the Japanese versions of ISA Server.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.To install the hotfix, 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 hotfix on a one-by-one basis.

To implement the functionality in this hotfix, create the following registry key:

1. Stop the Web Proxy service.
2. Start Registry Editor.
3. Locate and select the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3Proxy\Parameters
4. Create a new DWORD value that is named
   IgnoreLeadingSlashInFtpPath
   . Give this new value a data value of 1.
5. Restart the Web Proxy service.

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.