MS02-070: Flaw in SMB Signing May Permit Group Policy to Be Modified (329170)


The information in this article applies to:

  • Microsoft Windows XP 64-Bit Edition
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
  • Microsoft Windows XP Tablet PC Edition
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server
This article was previously published under Q329170

SYMPTOMS

Support for the Server Message Block (SMB) protocol is included in all versions of Windows. Although SMB is a file-sharing protocol, SMB is also used for other purposes. One of these purposes is disseminating Group Policy settings from domain controllers to computers that log on. Beginning with Windows 2000, it is possible to improve the integrity of SMB sessions by digitally signing all packets in a session. Windows 2000 and Windows XP can be configured to always sign, never sign, or sign only if the other party requires it.

A flaw in the implementation of SMB signing in Windows 2000 and Windows XP can permit an attacker to silently downgrade the SMB signing settings on an affected computer. To do this, an attacker must have access to the session negotiation data as it is exchanged between a client and server, and must be able to modify the data in a way that exploits the flaw. This can cause either or both computers to send unsigned data no matter what signing policy the administrator sets. After the attacker downgrades the signing setting, the attacker can continue to monitor and change data in the session. The lack of signing prevents the communicators from detecting the changes.

Although this vulnerability can be exploited to expose any SMB session to tampering, the most serious case involves changing Group Policy settings as they are disseminated from a Windows 2000-based domain controller to a newly logged-on network client. By doing this, an attacker can take actions such as adding users to the local Administrators group or installing and running code on the computer. Note that Windows XP cannot be used as a domain controller. Therefore, this scenario does not apply to Windows XP. This is the highest-risk scenario that is associated with the vulnerability.

RESOLUTION

Windows XP service pack information

To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

Windows XP hotfix information

Download information

The following files are available for download from the Microsoft Download Center:

32-bit: DownloadDownload the 329170 package now

64-bit: DownloadDownload the 329170 package now

Release Date: December 11, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Restart requirement

You must restart your computer after you apply this update.

Installation information

This update supports the following Setup switches:
  • /? Display the list of installation switches.
  • /u Unattended mode.
  • /f Force other programs to quit when the computer shuts down.
  • /n Do not back up files for removal.
  • /o Overwrite OEM files without prompting.
  • /z Do not restart when installation is complete.
  • /q Quiet mode (no user interaction).
  • /l List installed hotfixes.
  • /x Extracts the files without running Setup.
For example, the following command line installs the update without any user intervention and then does not force the computer to restart:

q329170_wxp_sp2_x86_enu /q /u /z

Warning Your computer is vulnerable until you restart it.

File information

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.

The following files are installed in the %Windir%\System32\Drivers folder. 

Windows XP

   Date        Time  Version      Size    File name
   --------------------------------------------------------------
   31-Oct-2002 19:45 5.1.2600.105 322,304 Srv.sys 

Windows XP SP1, Windows XP Tablet PC Edition 

   Date        Time  Version       Size    File name     
   -------------------------------------------------------------- 
   20-Dec-2002 17:36 5.1.2600.1154 322,048 Srv.sys 

Windows XP 64-Bit Edition 

   Date        Time  Version      Size      File name
   -------------------------------------------------------------- 
   31-Oct-2002 19:45 5.1.2600.105 1,142,016 Srv.sys 

Windows XP 64-Bit Edition SP1 

   Date        Time  Version       Size      File name 
   -------------------------------------------------------------- 
   20-Dec-2002 17:36 5.1.2600.1154 1,140,480 Srv.sys
Note If your network is affected, you must install this fix on all Windows XP-based clients in your network.

Windows 2000 service pack information

To resolve this problem, obtain the latest service pack for Microsoft Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

Windows 2000 hotfix information

Download information

The following files are available for download from the Microsoft Download Center:

All Languages except NEC Japanese: DownloadDownload the 329170 package now

NEC Japanese: DownloadDownload the 329170 package now

Release Date: December 11, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.

Restart requirement

Because of file dependencies, this update requires Windows 2000 Service Pack 2 (SP2) or Service Pack 3 (SP3). For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

Installation Information

You must restart your computer after you apply this update. This update supports the following Setup switches:
  • /? Display the list of installation switches.
  • /u Unattended mode.
  • /f Force other programs to quit when the computer shuts down.
  • /n Do not back up files for removal.
  • /o Overwrite OEM files without prompting.
  • /z Do not restart when installation is complete.
  • /q Quiet mode (no user interaction).
  • /l List installed hotfixes.
  • /x Extracts the files without running Setup.
For example, the following command line installs the update without any user intervention and then does not force the computer to restart:

q329170_w2k_sp4_x86_en /q /u /z

Warning Your computer is vulnerable until you restart it.

File Information

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.

The following files are installed in the %Windir%\System32\ folder: 

   Date          Time    Version         Size      File name
   ------------------------------------------------------------
   01-Nov-2002   16:55   5.0.2195.6090   250,640   Localspl.dll
   01-Nov-2002   16:55   5.0.2195.6023   381,712   Printui.dll
   23-Oct-2002   15:05   5.0.2195.6100   138,752   Sp3res.dll
   01-Nov-2002   16:55   5.0.2195.6047    79,632   Spoolss.dll
   31-Oct-2002   00:45   5.0.2195.6110   237,456   Srv.sys
   01-Nov-2002   16:55   5.0.2195.6110    74,000   Srvsvc.dll
   01-Nov-2002   16:55   5.0.2195.6044    84,752   Win32spl.dll
   01-Nov-2002   16:55   5.0.2195.6032   114,448   Winspool.drv
   01-Nov-2002   16:55   5.0.2195.6103    55,056   Wlnotify.dll

STATUS

Microsoft has confirmed that this problem may cause a degree of security vulnerability in the Microsoft products that are listed in the "Applies to" section.

Windows XP

This problem was first corrected in Microsoft Windows XP Service Pack 2.

Windows 2000

This problem was first corrected in Microsoft Windows 2000 Service Pack 4.

MORE INFORMATION

For more information about this vulnerability, visit the following Microsoft Web site:

http://www.microsoft.com/technet/security/bulletin/MS02-070.mspx

Modification Type:MinorLast Reviewed:9/27/2005
Keywords:kbHotfixServer kbQFE ATdownload kbWinXPsp2fix kbenv kbSecurity kbWin2kSP4fix kbbug kbfix kbWin2000preSP4Fix kbWinXPpreSP2fix KB329170
©2004 Microsoft Corporation. All rights reserved.