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Category:   Application (Security)  >   OpenSSL Vendors:   OpenSSL.org
OpenSSL SSL_OP_MSIE_SSLV2_RSA_PADDING Option May Let Remote Users Rollback the Protocol Version
SecurityTracker Alert ID:  1015032
SecurityTracker URL:  http://securitytracker.com/id/1015032
CVE Reference:   CVE-2005-2969   (Links to External Site)
Updated:  Dec 22 2005
Original Entry Date:  Oct 11 2005
Impact:   Disclosure of authentication information, Disclosure of system information, Disclosure of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): prior to 0.9.7h; 0.9.8.
Description:   A vulnerability was reported in OpenSSL. A remote user may be able to cause a target client and server to rollback to a weaker cryptographic protocol in certain cases.

The SSL_OP_MSIE_SSLV2_RSA_PADDING option (or SSL_OP_ALL option) disables a verification step in the SSL 2.0 server that would otherwise prevent active protocol-version rollback attacks.

A remote user can conduct a "man in the middle" attack to force a client and a server to negotiate the SSL 2.0 protocol instead of SSL 3.0 or TLS 1.0. The SSL 2.0 protocol is a cryptographically weak protocol.

Applications that use the OpenSSL SSL/TLS server implementation may be affected.

Applications that do not use SSL_OP_MSIE_SSLV2_RSA_PADDING and SSL_OP_ALL are not affected. Applications that disable the use of SSL 2.0 are also not affected.

The vendor credits Yutaka Oiwa of the Research Center for Information Security, National Institute of Advanced Industrial Science and Technology (AIST), Japan, with reporting this vulnerability.

Impact:   A remote user with the ability to conduct a man-in-the-middle attack can cause a client and server to use the weaker SSL 2.0 protocol.
Solution:   The vendor has issued fixed versions (0.9.7h and 0.9.8a), available at:

http://www.openssl.org/source/
ftp://ftp.openssl.org/source/

The distribution file names are:

o openssl-0.9.8a.tar.gz
MD5 checksum: 1d16c727c10185e4d694f87f5e424ee1
SHA1 checksum: 2aaba0f728179370fb3e86b43209205bc6c06a3a

o openssl-0.9.7h.tar.gz
MD5 checksum: 8dc90a113eb8925795071fbe52b2932c
SHA1 checksum: 9fe535fce89af967b29c4727dedd25f2b4cc2f0d

The checksums were calculated using the following commands:

openssl md5 openssl-0.9*.tar.gz
openssl sha1 openssl-0.9*.tar.gz

FreeBSD has issued a fix for FreeBSD UNIX:

ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05%3A21.openssl.asc

Sun has described a workaround:

http://sunsolve.sun.com/search/document.do?assetkey=1-26-101974-1

Red Hat has issued a fix for Red Hat Enterprise Linux 2.1, 3, and 4:

https://rhn.redhat.com/errata/RHSA-2005-800.html

Vendor URL:  www.openssl.org/news/secadv_20051011.txt (Links to External Site)
Cause:   Authentication error, State error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   This archive entry has one or more follow-up message(s) listed below.
Oct 11 2005 (FreeBSD Issues Fix) OpenSSL SSL_OP_MSIE_SSLV2_RSA_PADDING Option May Let Remote Users Rollback the Protocol Version
FreeBSD has released a fix.
Dec 22 2005 (Juniper Issues Fix for IVE) OpenSSL SSL_OP_MSIE_SSLV2_RSA_PADDING Option May Let Remote Users Rollback the Protocol Version
Juniper has issued a fix for Netscreen IVE, which is affected by this OpenSSL vulnerability.
May 20 2008 (Red Hat Issues Fix for Red Hat Network Satellite Server) OpenSSL SSL_OP_MSIE_SSLV2_RSA_PADDING Option May Let Remote Users Rollback the Protocol Version
Red Hat has released a fix for Red Hat Network Satellite Server 5.x.



 Source Message Contents

Subject:  [Full-disclosure] OpenSSL SSL 2.0 Rollback (CVE-2005-2969)

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

OpenSSL Security Advisory [11 October 2005]

Potential SSL 2.0 Rollback (CAN-2005-2969)
==========================================

CONTENTS

 - Vulnerability
 - Recommendations
 - Acknowledgement
 - References


Vulnerability
- -------------

A vulnerability has been found in all previously released versions of
OpenSSL (all versions up to 0.9.7h and 0.9.8a).  Versions 0.9.7h and
0.9.8a have been released to address the issue.  The vulnerability
potentially affects applications that use the SSL/TLS server
implementation provided by OpenSSL.

Such applications are affected if they use the option
SSL_OP_MSIE_SSLV2_RSA_PADDING.  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
SSL_OP_MSIE_SSLV2_RSA_PADDING option disables a verification step in
the SSL 2.0 server supposed to prevent active protocol-version
rollback attacks.  With this verification step disabled, 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.

Applications using neither SSL_OP_MSIE_SSLV2_RSA_PADDING nor
SSL_OP_ALL are not affected.  Also, applications that disable
use of SSL 2.0 are not affected.

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2005-2969 to this issue.

Recommendations
- ---------------

There are multiple ways to avoid this vulnerability.  Any one of the
following measures is sufficient.

1.  Disable SSL 2.0 in the OpenSSL-based application.

    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.  Thus, if you have
    disabled SSL 2.0, the vulnerability does not apply to you.
    Generally, it is strongly recommended to disable the SSL 2.0
    protocol because of its known weaknesses.

2.  Upgrade the OpenSSL server software.

    The vulnerability is resolved in the following versions of OpenSSL:

     - in the 0.9.7 branch, version 0.9.7h (or later);
     - in the 0.9.8 branch, version 0.9.8a (or later).

    OpenSSL 0.9.8a and OpenSSL 0.9.7h are available for download via
    HTTP and FTP from the following master locations (you can find the
    various FTP mirrors under http://www.openssl.org/source/mirror.html):

        o http://www.openssl.org/source/
        o ftp://ftp.openssl.org/source/

    The distribution file names are:

        o openssl-0.9.8a.tar.gz
          MD5 checksum: 1d16c727c10185e4d694f87f5e424ee1
          SHA1 checksum: 2aaba0f728179370fb3e86b43209205bc6c06a3a

        o openssl-0.9.7h.tar.gz
          MD5 checksum: 8dc90a113eb8925795071fbe52b2932c
          SHA1 checksum: 9fe535fce89af967b29c4727dedd25f2b4cc2f0d
    
    The checksums were calculated using the following commands:

        openssl md5 openssl-0.9*.tar.gz
        openssl sha1 openssl-0.9*.tar.gz

    If this version upgrade is not an option at the present time,
    alternatively the following patch may be applied to the OpenSSL
    source code to resolve the problem.  The patch is compatible with
    the 0.9.6, 0.9.7, and 0.9.8 branches of OpenSSL.

        o http://www.openssl.org/news/patch-CAN-2005-2969.txt

    Whether you choose to upgrade to a new version or to apply the
    patch, make sure to recompile any applications statically linked
    to OpenSSL libraries if these applications use the OpenSSL
    SSL/TLS server implementation.    


Acknowledgement
- ---------------

The OpenSSL team thank Yutaka Oiwa of the Research Center for
Information Security, National Institute of Advanced Industrial
Science and Technology (AIST), Japan, for alerting us about this
problem.


References
- ----------

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

URL for this Security Advisory:
http://www.openssl.org/news/secadv_20051011.txt
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