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                                  CERT-Renater

                       Note d'Information No. 2005/VULN636
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DATE                      : 14/10/2005

HARDWARE PLATFORM(S)      : /

OPERATING SYSTEM(S)       : Sun systems running OpenSSL.

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Sun(sm) Alert Notification
      * Sun Alert ID: 101974
      * Synopsis: OpenSSL (see openssl(5)) May Allow an Agent to Force a
        Rollback to a Cryptographically Weak Protocol Version
      * Category: Security
      * Product: Solaris 10 Operating System
      * BugIDs: 6332476
      * Avoidance: Workaround
      * State: Workaround
      * Date Released: 11-Oct-2005
      * Date Closed:
      * Date Modified:

1. Impact

    A vulnerability in the OpenSSL (see openssl(5)) toolkit may allow
    active protocol-version rollback attacks, where an attacker acting as
    a "man in the middle" can force a client and a server to negotiate the
    SSL 2.0 protocol even if these parties both support SSL 3.0 or TLS
    1.0. The SSL 2.0 protocol is known to have severe cryptographic
    weaknesses and is supported as a fallback only.

    This issue is described in the following OpenSSL Advisory:
    http://www.openssl.org/news/secadv_20051011.txt

    and referenced in CAN-2005-2969
    at: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-2969

2. Contributing Factors

    This issue can occur in the following releases:

    SPARC Platform
      * Solaris 10

    x86 Platform
      * Solaris 10

    Note: Solaris 8 and 9 do not include OpenSSL toolkit, and therefore
    are not vulnerable to this issue.

    Applications that use the option SSL_OP_MSIE_SSLV2_RSA_PADDING (see
    SSL_CTX_set_options(3)) are affected. This option is implied by use of
    SSL_OP_ALL, which is intended to work around various bugs in
    third-party software that might prevent interoperability.

    The vulnerability occurs only if the old protocol version SSL 2.0 is
    enabled both in an OpenSSL server and in any of the clients
    (OpenSSL-based or not) connecting to it.

3. Symptoms

    There are no reliable symptoms that would indicate the described issue
    has been exploited.

4. Relief/Workaround

    To work around the described issue:

    If Apache or Apache2 in Solaris 10 are configured with SSL service on
    port 443 (https), the following command can be used to check if the
    SSL 2.0 protocol is enabled at the server:
     $ /usr/sfw/bin/openssl s_client -ssl2 -connect <hostname>:443 -state -debug

    If the above command produces output, then SSLv2 is enabled and can be
    disabled in the Apache and Apache2 web servers as follows:

    1. As a privileged user, edit the following file:
     Apache: /etc/apache/httpd.conf
     Apache2: /etc/apache2/ssl.conf

    2. Modify the line which begins with:
     SSLCipherSuite

    to change the string '+SSLv2' to '!SSLv2'.

    3. Restart the Apache web server:
     Apache: # /usr/apache/bin/apachectl restart
     Apache2: svcadm restart apache2


5. Resolution

    A final resolution is pending completion.

    This Sun Alert notification is being provided to you on an "AS IS"
    basis. This Sun Alert notification may contain information provided by
    third parties. The issues described in this Sun Alert notification may
    or may not impact your system(s). Sun makes no representations,
    warranties, or guarantees as to the information contained herein. ANY
    AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
    WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
    NON-INFRINGEMENT, ARE HEREBY DISCLAIMED. BY ACCESSING THIS DOCUMENT
    YOU ACKNOWLEDGE THAT SUN SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT,
    INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE
    OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN.
    This Sun Alert notification contains Sun proprietary and confidential
    information. It is being provided to you pursuant to the provisions of
    your agreement to purchase services from Sun, or, if you do not have
    such an agreement, the Sun.com Terms of Use. This Sun Alert
    notification may only be used for the purposes contemplated by these
    agreements.

    Copyright 2000-2005 Sun Microsystems, Inc., 4150 Network Circle, Santa
    Clara, CA 95054 U.S.A. All rights reserved

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