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FreeBSD-SA-16:11.openssl                                    Security Advisory
                                                          The FreeBSD Project

Topic:          OpenSSL SSLv2 ciphersuite downgrade vulnerability

Category:       contrib
Module:         openssl
Announced:      2016-01-30
Affects:        All supported versions of FreeBSD.
Corrected:      2016-01-28 21:42:10 UTC (stable/10, 10.2-STABLE)
                2016-01-30 06:12:03 UTC (releng/10.2, 10.2-RELEASE-p12)
                2016-01-30 06:12:03 UTC (releng/10.1, 10.1-RELEASE-p29)
                2016-01-30 06:09:38 UTC (stable/9, 9.3-STABLE)
                2016-01-30 06:12:03 UTC (releng/9.3, 9.3-RELEASE-p36)
CVE Name:       CVE-2015-3197

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

FreeBSD includes software from the OpenSSL Project.  The OpenSSL Project is
a collaborative effort to develop a robust, commercial-grade, full-featured
Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3)
and Transport Layer Security (TLS v1) protocols as well as a full-strength
general purpose cryptography library.

II.  Problem Description

A malicious client can negotiate SSLv2 ciphers that have been disabled on
the server and complete SSLv2 handshakes even if all SSLv2 ciphers have
been disabled, provided that the SSLv2 protocol was not also disabled via
SSL_OP_NO_SSLv2.

III. Impact

An active MITM attacker may be able to force a protocol downgrade to SSLv2,
which is a flawed protocol and intercept the communication between client
and server.

IV.  Workaround

No workaround is available, but only applications that do not explicitly
disable SSLv2 are affected.

To determine if a server have SSLv2 enabled, a system administrator can
use the following command:

% openssl s_client -ssl2 -connect <host>:<port> </dev/null 2>&1 | grep DONE

which will print "DONE" if and only if SSLv2 is enabled.  Note that this
check will not work for services that uses STARTTLS or DTLS.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

Restart all deamons using the library, or reboot the system.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Restart all deamons using the library, or reboot the system.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 10.2]
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-10.2.patch
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-10.2.patch.asc
# gpg --verify openssl-10.2.patch.asc

[FreeBSD 10.1]
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-10.1.patch
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-10.1.patch.asc
# gpg --verify openssl-10.1.patch.asc

[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-9.3.patch
# fetch https://security.FreeBSD.org/patches/SA-16:11/openssl-9.3.patch.asc
# gpg --verify openssl-9.3.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart all deamons using the library, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r295060
releng/9.3/                                                       r295061
stable/10/                                                        r295016
releng/10.1/                                                      r295061
releng/10.2/                                                      r295061
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://www.openssl.org/news/secadv/20160128.txt>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-3197>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:11.openssl.asc>
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