": $DATA" Data Stream Name of a File May Return Source

ID: Q188806

The information in this article applies to:

Microsoft Internet Information Server versions 1.0, 2.0, 3.0, 4.0
Microsoft Peer Web Server version 4.0 for Windows NT 4.0
Microsoft Personal Web Server version 4.0 for NT Workstation version 4.0
Microsoft Windows NT Server version 4.0, Terminal Server Edition

SYMPTOMS

The native Windows NT file system, NTFS, supports multiple data streams within a file. The main data stream, that which stores the main content, is called DATA. Accessing this NTFS attribute directly from a browser may display the script code for the file. For example, accessing http://myserver/file.asp::$DATA may yield the contents of the file itself, not the processed results of the file.

CAUSE

The problem is caused by the way Internet Information Server (IIS) parses file names. The fix involves IIS supporting NTFS alternate data streams by asking Windows NT to canonicalize the filename.

NOTE: For the problem to occur, all of the following conditions must exist:

The file must reside on an NTFS partition.

The user must know the name of the file.

The user must have Read access to the file.

WORKAROUND

NOTE: The fix for a bug in the W3 and FTP Performance Monitor ALSO fixes the problem described in this article. If you plan to use the Performance Monitor, please see the following article in the Microsoft Knowledge Base:

Q185349 : Problems Remotely Accessing W3 or FTP Perfmon Counters

If you cannot apply the available fix, you can use the following workarounds to temporarily address this issue.

All IIS versions:

Normally, web users do not need Read access to script files, such as .ASP files. They simply need Execute permissions. Removing Read access to these files for non-administrative users will remove this exposure.

IIS 4.0 only:

Make the following additions to the Application Map in IIS 4.0 (this should be done for all mappings):

Open the Microsoft Management Console (MMC).

Right-click the Virtual Server in question.

Click Properties on the shortcut menu.

On the Home Directory tab, select Configuration.

Now add each of the entries noted below to the list of application mappings. The entries should be entered into the Extension.

Executable Path %System32%\Inetsrv\Asp.dll
```
      .asp::$DATA
      .asa::$DATA
 
```
Executable Path %System32%\Inetsrv\Ssinc.dll
```
      .stm::$DATA
      .shtm::$DATA
      .shtml::$DATA
 
```
Executable Path %System32%\Inetsrv\Httpodbc.dll
```
      .idc::$DATA
 
```
Executable Path %System32%\Webhits.dll
```
      .htw::$DATA
 
```
If you use Index Server, also include the following:

Executable Path %System32%\Idq.dll
```
      .idq::$DATA
      .ida::$DATA
 
```
PERL

If you use PERL, add the following entry, mapped to your PERL script interpreter:
```
      .pl::$DATA
 
```

General Security Practices:

In addition, the following practices can help to further improve security for your IIS servers:

Periodically review the users and groups who have access to the web server. Review the users and groups and their permissions to ensure that only valid users have the appropriate permissions.

Use auditing to detect suspicious activity. Apply auditing controls on sensitive files and review these logs periodically to detect suspicious or unauthorized behavior.

Set Read and Execute permissions appropriately. ASP and other script files do not need to be readable by users that access them through IIS, rather they need to be executable. Thus, it is advisable to remove Read access from these files for normal users.

RESOLUTION

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, please see the following article in the Microsoft Knowledge Base:

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

STATUS

Microsoft has confirmed this to be a problem in Internet Information Server versions 1.0, 2.0, 3.0, and 4.0, Peer Web Server versions 2.0 and 3.0, and Personal Web Server version 4.0 on Windows NT 4.0 Workstation. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

IIS 4.0

On July 17, 1998, Microsoft released an updated version of this hotfix.

This fix has been posted to the following Internet location:

ftp://ftp.microsoft.com/bussys/iis/iis-public/fixes/usa/security/iis4-datafix/

IIS 3.0

This fix has been posted to the following Internet location:

ftp://ftp.microsoft.com/bussys/iis/iis-public/fixes/usa/security/iis3-datafix/

IIS 1.0, 2.0

For all IIS 1.0, 2.0 and Peer Web Server 2.0 platforms, we strongly recommend that you upgrade to a more recent version. If you cannot upgrade to a more recent version, you can use the workarounds listed above to temporarily address this issue.

MORE INFORMATION

For more information on this issue, see the following Microsoft Security Bulletin:

http://www.microsoft.com/security/bulletins/ms98-003.htm 98-003: File Access issue with Internet Information Server

A very similar problem is documented in the following article in the Microsoft Knowledge Base:

Q193793 : ":$DATA" Data Stream Name Returns Source of a Remote File

The problem documented in Q193793 concerns the ":$DATA" data stream, rather than the "::$DATA" data stream described in this article. Also, the problem described in Q193793 only occurs on a remote computer.

For more information on Alternate Data Streams, see the following article in the Microsoft Knowledge Base:

Q105763 : HOWTO: Use NTFS Alternate Data Streams

Additional query words: Peer Web Services filename filenames pws hot fix qfe sp service pack


Keywords          : NT4SP4Fix kbfix4.00.sp4 
Version           : WINDOWS:4.0; winnt:1.0,2.0,3.0,4.0
Platform          : WINDOWS winnt 
Issue type        : kbbug

Last Reviewed: April 26, 1999