ISA Server Forces CERN FTP Connections to the Root Directory (823646)

CAUSE

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.

WORKAROUND

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:

ftp://username:password@host/username/sub-dir/

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.

RESOLUTION

For additional 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:

313139 How to Obtain the Latest Internet Security and Acceleration Server 2000 Service Pack

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Internet Security and Acceleration Server 2000 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The English version of this hotfix 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. 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.

   Date         Time   Version            Size    File name
   -----------------------------------------------------------
   20-Jul-2003  20:57  3.0.1200.283      178,448  Mspadmin.exe     
   20-Jul-2003  20:57  3.0.1200.283      103,184  Msphlpr.dll      
   20-Jul-2003  20:56  3.0.1200.283      392,464  W3proxy.exe      
   20-Jul-2003  20:57  3.0.1200.283      299,280  Wspsrv.exe

MORE INFORMATION

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 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:

IgnoreLeadingSlashInFtpPath

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

To revert to the original configuration, either remove the IgnoreLeadingSlashInFtpPath registry value or change its data value to 0 (zero). After you make either change, restart the Web Proxy service.