Operating System:

[Win]

Published:

11 February 2010

Protect yourself against future threats.

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2010.0141
               Vulnerability in TLS/SSL Could Allow Spoofing
                             11 February 2010

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Transport Layer Security (TLS)
                   Secure Sockets Layer (SSL)
Publisher:         Microsoft
Operating System:  Windows Server 2008
                   Windows Server 2003
                   Windows 2000
                   Windows 7
                   Windows Vista
                   Windows XP
Impact/Access:     Provide Misleading Information -- Remote with User Interaction
Resolution:        Mitigation
CVE Names:         CVE-2009-3555  

Reference:         ASB-2009.1150
                   ESB-2010.0036.2

Original Bulletin: 
   http://www.microsoft.com/technet/security/advisory/977377.mspx

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Microsoft Security Advisory (977377)

Vulnerability in TLS/SSL Could Allow Spoofing

Published: February 09, 2010

Version: 1.0

General Information

Executive Summary

  Microsoft is investigating public reports of a vulnerability in the 
  Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. 
  At this time, Microsoft is not aware of any attacks attempting to exploit 
  the reported vulnerability.

  As an issue affecting an Internet standard, we recognize that this issue 
  affects multiple vendors. We are working on a coordinated response with 
  our partners in the Internet Consortium for Advancement of Security on 
  the Internet (ICASI). The TLS and SSL protocols are implemented in 
  several Microsoft products, both client and server, and this 
  advisory will be updated as our investigation continues.

  As part of this security advisory, Microsoft is making available a 
  workaround which enables system administrators to disable TLS and SSL 
  renegotiation functionality. However, as renegotiation is required 
  functionality for some applications, this workaround is not intended 
  for wide implementation and should be tested extensively prior to 
  implementation.

  Upon completion of this investigation, Microsoft will take the 
  appropriate action to protect our customers, which may include providing 
  a solution through our monthly security update release process, 
  depending on customer needs.

Affected Software

  Microsoft Windows 2000 Service Pack 4
  Windows XP Service Pack 2 and Windows XP Service Pack 3
  Windows XP Professional x64 Edition Service Pack 2
  Windows Server 2003 Service Pack 2
  Windows Server 2003 x64 Edition Service Pack 2
  Windows Server 2003 with SP2 for Itanium-based Systems
  Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service 
    Pack 2
  Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and 
    Windows Vista x64 Edition Service Pack 2
  Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit 
    Systems Service Pack 2
  Windows Server 2008 for x64-based Systems and Windows Server 2008 for 
    x64-based Systems Service Pack
  Windows Server 2008 for Itanium-based Systems and Windows Server 2008 
    for Itanium-based Systems Service Pack 2
  Windows 7 for 32-bit Systems
  Windows 7 for x64-based Systems
  Windows Server 2008 R2 for x64-based Systems
  Windows Server 2008 R2 for Itanium-based Systems

What is the scope of the advisory?

  Microsoft is aware of a new report of a vulnerability affecting the 
  Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols. 
  This vulnerability could allow a malicious man-in-the-middle attack to 
  introduce and execute a request in the protected TLS/SSL session between a 
  client and a server.

Workarounds

  Microsoft has tested the following workarounds. Although these workarounds 
  will not correct the underlying vulnerability, they help block known attack 
  vectors. When a workaround reduces functionality, it is identified in the 
  following section.
	
Enable SSLAlwaysNegoClientCert on IIS 6 and above

  Web servers running IIS 6 and later that are affected because they require 
  mutual authentication by requesting a client certificate, can be hardened 
  by enabling the SSLAlwaysNegoClientCert setting. This will cause IIS to 
  prompt the client for a certificate upon the initial connection, and does 
  not require a server-initiated renegotiation.

For IIS 6:

  Run the following command from the "c:\inetpub\adminscripts" folder in an 
  elevated / administrator command prompt:

    adsutil.vbs SET w3svc/<N>/SSLAlwaysNegoClientCert true

  Where <N> represents the number of the web site to be configured 
  (i.e. the 'Default Web Site' is 1, the next web site is 2, etc.). 
  So for example - to protect the 'Default Web Site' created by IIS the 
  following command would be used:

    adsutil.vbs SET w3svc/1/SSLAlwaysNegoClientCert true

For IIS 7:

  Save the following text to a file called 
  "Enable_SSL_Renegotiate_Workaround.js"

    var vdirObj=GetObject("IIS://localhost/W3svc/1"); 
    // replace 1 on this line with the number of the web site you wish 
    to configure 

    WScript.Echo("Value of SSLAlwaysNegoClientCert Before: " + vdirObj.SSLAlwaysNegoClientCert); 
    vdirObj.Put("SSLAlwaysNegoClientCert", true); 
    vdirObj.SetInfo(); 
    WScript.Echo("Value of SSLAlwaysNegoClientCert After: " + vdirObj.SSLAlwaysNegoClientCert);

  Run the following command from an elevated / administrator command 
  prompt:

    cscript.exe enable_ssl_renegotiate_workaround.js

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===========================================================================
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