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FreeBSD-SA-09:11.ntpd                                       Security Advisory
                                                          The FreeBSD Project

Topic:          ntpd stack-based buffer-overflow vulnerability

Category:       contrib
Module:         ntpd
Announced:      2009-06-10
Credits:        Chris Ries
Affects:        All supported versions of FreeBSD.
Corrected:      2009-06-10 10:31:11 UTC (RELENG_7, 7.2-STABLE)
                2009-06-10 10:31:11 UTC (RELENG_7_2, 7.2-RELEASE-p1)
                2009-06-10 10:31:11 UTC (RELENG_7_1, 7.1-RELEASE-p6)
                2009-06-10 10:31:11 UTC (RELENG_6, 6.4-STABLE)
                2009-06-10 10:31:11 UTC (RELENG_6_4, 6.4-RELEASE-p5)
                2009-06-10 10:31:11 UTC (RELENG_6_3, 6.3-RELEASE-p11)
CVE Name:       CVE-2009-1252

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

I.   Background

The ntpd(8) daemon is an implementation of the Network Time Protocol (NTP)
used to synchronize the time of a computer system to a reference time
source.

Autokey is a security model for authenticating Network Time Protocol
(NTP) servers to clients, using public key cryptography.

II.  Problem Description

The ntpd(8) daemon is prone to a stack-based buffer-overflow when it is
configured to use the 'autokey' security model.

III. Impact

This issue could be exploited to execute arbitrary code in the context of
the service daemon, or crash the service daemon, causing denial-of-service
conditions.

IV.  Workaround

Use IP based restrictions in ntpd(8) itself or in IP firewalls to
restrict which systems can send NTP packets to ntpd(8).

Note that systems will only be affected if they have the "autokey" option
set in /etc/ntp.conf; FreeBSD does not ship with a default ntp.conf file,
so will not be affected unless this option has been explicitly enabled by
the system administrator.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 6-STABLE, or 7-STABLE, or to the
RELENG_7_2, RELENG_7_1, RELENG_6_4, or RELENG_6_3 security branch
dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 6.3, 6.4,
7.1, and 7.2 systems.

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

[FreeBSD 6.3]
# fetch http://security.FreeBSD.org/patches/SA-09:11/ntpd63.patch
# fetch http://security.FreeBSD.org/patches/SA-09:11/ntpd63.patch.asc

[FreeBSD 6.4 and 7.x]
# fetch http://security.FreeBSD.org/patches/SA-09:11/ntpd.patch
# fetch http://security.FreeBSD.org/patches/SA-09:11/ntpd.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/usr.sbin/ntp/ntpd
# make obj && make depend && make && make install
# /etc/rc.d/ntpd restart

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

CVS:

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_6
  src/contrib/ntp/ntpd/ntp_crypto.c                           1.1.1.3.8.3
RELENG_6_4
  src/UPDATING                                             1.416.2.40.2.9
  src/sys/conf/newvers.sh                                  1.69.2.18.2.11
  src/contrib/ntp/ntpd/ntp_crypto.c                       1.1.1.3.8.1.2.2
RELENG_6_3
  src/UPDATING                                            1.416.2.37.2.16
  src/sys/conf/newvers.sh                                  1.69.2.15.2.15
  src/contrib/ntp/ntpd/ntp_crypto.c                          1.1.1.3.20.2
RELENG_7
  src/contrib/ntp/ntpd/ntp_crypto.c                          1.1.1.3.18.3
RELENG_7_2
  src/UPDATING                                             1.507.2.23.2.4
  src/sys/conf/newvers.sh                                   1.72.2.11.2.5
  src/contrib/ntp/ntpd/ntp_crypto.c                      1.1.1.3.18.2.2.1
RELENG_7_1
  src/UPDATING                                             1.507.2.13.2.9
  src/sys/conf/newvers.sh                                   1.72.2.9.2.10
  src/contrib/ntp/ntpd/ntp_crypto.c                      1.1.1.3.18.1.2.2
- -------------------------------------------------------------------------

Subversion:

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/6/                                                         r193893
releng/6.4/                                                       r193893
releng/6.3/                                                       r193893
stable/7/                                                         r193893
releng/7.2/                                                       r193893
releng/7.1/                                                       r193893
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-1252

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-09:11.ntpd.asc
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