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FreeBSD-SA-15:07.ntp Security Advisory
The FreeBSD Project

Topic: Multiple vulnerabilities of ntp

Category: contrib
Module: ntp
Announced: 2015-04-07
Credits: Network Time Foundation
Affects: All supported versions of FreeBSD.
Corrected: 2015-04-07 20:20:24 UTC (stable/10, 10.1-STABLE)
2015-04-07 20:21:01 UTC (releng/10.1, 10.1-RELEASE-p9)
2015-04-07 20:20:44 UTC (stable/9, 9.3-STABLE)
2015-04-07 20:21:23 UTC (releng/9.3, 9.3-RELEASE-p13)
2015-04-07 20:20:44 UTC (stable/8, 8.4-STABLE)
2015-04-07 20:21:23 UTC (releng/8.4, 8.4-RELEASE-p27)
CVE Name: CVE-2014-9297, CVE-2015-1798, CVE-2015-1799

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

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.

II. Problem Description

The vallen packet value is not validated in several code paths in
ntp_crypto.c. [CVE-2014-9297]

When ntpd(8) is configured to use a symmetric key to authenticate a remote
NTP server/peer, it checks if the NTP message authentication code (MAC)
in received packets is valid, but not that there actually is any MAC
included, and packets without a MAC are accepted as if they had a valid
MAC. [CVE-2015-1798]

NTP state variables are updated prior to validating the received packets.
[CVE-2015-1799]

III. Impact

A remote attacker who can send specifically crafted packets may be able
to reveal memory contents of ntpd(8) or cause it to crash, when ntpd(8)
is configured to use autokey. [CVE-2014-9297]

A man-in-the-middle (MITM) attacker can send specially forged packets
that would be accepted by the client/peer without having to know the
symmetric key. [CVE-2015-1798]

An attacker knowing that NTP hosts A and B are peering with each other
(symmetric association) can periodically send a specially crafted or
replayed packet which will break the synchronization between the two
peers due to transmit timestamp mismatch, preventing the two nodes from
synchronizing with each other, even when authentication is enabled.
[CVE-2015-1799]

IV. Workaround

No workaround is available, but systems not running ntpd(8) are not
affected.

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.

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

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.

# fetch https://security.FreeBSD.org/patches/SA-15:07/ntp.patch
# fetch https://security.FreeBSD.org/patches/SA-15:07/ntp.patch.asc
# gpg –verify ntp.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 the applicable daemons, or reboot the system.

VI. Correction details

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

Branch/path Revision
– ————————————————————————-
stable/8/ r281231
releng/8.4/ r281233
stable/9/ r281231
releng/9.3/ r281233
stable/10/ r281230
releng/10.1/ r281232
– ————————————————————————-

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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-9297>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-1798>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-1799>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-15:07.ntp.asc>
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