Microsoft Security Bulletin MS02-050

Discussion in 'other security issues & news' started by Marianna, Sep 5, 2002.

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  1. Marianna

    Marianna Spyware Fighter

    Joined:
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    Location:
    B.C. Canada
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    - ----------------------------------------------------------------------
    Title: Certificate Validation Flaw Could Enable Identity
    Spoofing (Q328145)
    Released: September 04, 2002
    Revised: September 05, 2002 (version 2.0)
    Software: Microsoft Windows, Microsoft Office for Mac, Microsoft
    Internet Explorer for Mac, or Microsoft Outlook Express
    for Mac.
    Impact: Identity spoofing.
    Max Risk: Critical

    Bulletin: MS02-050

    Microsoft encourages customers to review the Security Bulletin at:
    http://www.microsoft.com/technet/security/bulletin/MS02-050.asp .
    - ----------------------------------------------------------------------

    Reason for Revision:
    ====================
    Normally, Microsoft releases the patches for all affected products
    simultaneously, in order to provide a complete solution. However,
    exploit code for this issue has already been posted, and we are
    therefore releasing the patches as they become available, in order
    to allow customers to begin protecting their systems as quickly as
    possible.

    The bulletin has been updated to include patch availability for
    Windows 98, Windows 98 Second Edition, and Windows Me.

    Patches are now available for:
    - Windows 98
    - Windows 98 Second Edition
    - Windows Me
    - Windows NT 4.0
    - Windows NT 4.0, Terminal Server Edition
    - Windows XP
    - Windows XP 64 bit Edition

    Patches will be available shortly for:
    - Windows 2000
    - Microsoft Office v.X for Mac
    - Microsoft Office 2001 for Mac
    - Microsoft Office 98 for the Macintosh
    - Microsoft Internet Explorer for Mac (for OS 8.1 to 9.x)
    - Microsoft Internet Explorer for Mac (for OS X)
    - Microsoft Outlook Express 5.0.5 for Mac

    Issue:
    ======
    The IETF Profile of the X.509 certificate standard defines several
    optional fields that can be included in a digital certificate. One
    of these is the Basic Constraints field, which indicates the
    maximum allowable length of the certificate's chain and whether the
    certificate is a Certificate Authority or an end-entity certificate.
    However, the APIs within CryptoAPI that construct and validate
    certificate chains (CertGetCertificateChain(),
    CertVerifyCertificateChainPolicy(), and WinVerifyTrust()) do not
    check the Basic Constraints field. The same flaw, unrelated to
    CryptoAPI, is also present in several Microsoft products for
    Macintosh.

    The vulnerability could enable an attacker who had a valid
    end-entity certificate to issue a subordinate certificate that,
    although bogus, would nevertheless pass validation. Because
    CryptoAPI is used by a wide range of applications, this could
    enable a variety of identity spoofing attacks. These are
    discussed in detail in the bulletin FAQ, but could include:

    - Setting up a web site that poses as a different web site, and
    "proving" its identity by establishing an SSL session as the
    legitimate web site.

    - Sending emails signed using a digital certificate that
    purportedly belongs to a different user.

    - Spoofing certificate-based authentication systems to gain
    entry as a highly privileged user.

    - Digitally signing malware using an Authenticode certificate
    that claims to have been issued to a company users might trust.

    Mitigating Factors:
    ====================
    Overall:

    - The user could always manually check a certificate chain, and
    might notice in the case of a spoofed chain that there was an
    unfamiliar intermediate CA.

    - Unless the attacker's digital certificate were issued by a CA
    in the user's trust list, the certificate would generate a
    warning when validated.

    - The attacker could only spoof certificates of the same type as
    the one he or she possessed. In the case where the attacker
    attempted an attack using a high-value certificate such as
    Authenticode certificates, this would necessitate obtaining
    a legitimate certificate of the same type - which could
    require the attacker to prove his or her identity or
    entitlement to the issuing CA.

    Web Site Spoofing:

    - The vulnerability provides no way for the attacker to cause the
    user to visit the attacker's web site. The attacker would need
    to redirect the user to a site under the attacker's control
    using a method such as DNS poisoning. As discussed in the
    bulletin FAQ, this is extremely difficult to carry out in
    practice.

    - The vulnerability could not be used to extract information from
    the user's computer. The vulnerability could only be used by an
    attacker as a means of convincing a user that he or she has
    reached a trusted site, in the hope of persuading the user to
    voluntarily provide sensitive data.

    Email Signing:

    - The "from" address on the spoofed mail would need to match the
    one specified in the certificate, giving rise to either of two
    scenarios if a recipient replied to the mail. In the case where
    the "from" and "reply-to" fields matched, replies would be sent
    to victim of the attack rather than the attacker. In the case
    where the fields didn't match, replies would obviously be
    addressed to someone other than ostensible sender. Either case
    could be a tip-off that an attack was underway.

    Certificate-based Authentication:

    - In most cases where certificates are used for user
    authentication, additional information contained within the
    certificate is necessary to complete the authentication. The
    type and format of such data typically varies with every
    installation, and as a result significant insider information
    would likely be required for a successful attack.

    Authenticode Spoofing:

    - To the best of Microsoft's knowledge, such an attack could not
    be carried out using any commercial CA's Authenticode
    certificates. These certificates contain policy information
    that causes the Basic Constraints field to be correctly
    evaluated, and none allow end-entity certificates to act as CAs.

    - Even if an attack were successfully carried out using an
    Authenticode certificate that had been issued by a corporate
    PKI, it wouldn't be possible to avoid warning messages, as trust
    in Authenticode is brokered on a per-certificate, not per-name,
    basis.

    Risk Rating:
    ============
    Microsoft Windows platforms:
    - Internet systems: Critical
    - Intranet systems: Critical
    - Client systems: Critical

    Microsoft programs for Mac:
    - Internet systems: None
    - Intranet systems: None
    - Client systems: Moderate

    Patch Availability:
    ===================
    - - Patches are available to fix this vulnerability for Windows 98,
    Windows 98 Second Edition, Windows Me, Windows NT 4.0,
    Windows NT 4.0, Terminal Server Edition, Windows XP, and
    Windows XP 64 bit Edition.
    Patches for Windows 2000, Microsoft Office for Mac, Microsoft
    Internet Explorer for Mac, and Microsoft Outlook Express
    for Mac will be released shortly.
    Please read the Security Bulletin at
    http://www.microsoft.com/technet/security/bulletin/ms02-050.asp
    for information on obtaining this patch.
    - ---------------------------------------------------------------------

    THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
    "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
    WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
    MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
    SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
    DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
    CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN
    IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
    OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
    SO THE FOREGOING LIMITATION MAY NOT APPLY.


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    *******************************************************************
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  2. FanJ

    FanJ Guest

    Thanks Marianna ! :)
     
  3. Mr.Blaze

    Mr.Blaze The Newbie Welcome Wagon

    Joined:
    Feb 3, 2003
    Posts:
    2,842
    Location:
    on the sofa
    im patching right now lol duck tape fix everything
     
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