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AUSCERT External Security Bulletin Redistribution
ESB-2009.0046 -- [FreeBSD]
ntpd cryptographic signature bypass
14 January 2009
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AusCERT Security Bulletin Summary
---------------------------------
Product: ntpd
Publisher: FreeBSD
Operating System: FreeBSD
Impact: Provide Misleading Information
Access: Remote/Unauthenticated
CVE Names: CVE-2009-0021
Ref: ESB-2009.0039
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-09:03.ntpd.asc
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FreeBSD-SA-09:03.ntpd Security Advisory
The FreeBSD Project
Topic: ntpd cryptographic signature bypass
Category: contrib
Module: ntpd
Announced: 2009-01-13
Credits: Google Security Team
Affects: All FreeBSD releases
Corrected: 2009-01-13 21:19:27 UTC (RELENG_7, 7.1-STABLE)
2009-01-13 21:19:27 UTC (RELENG_7_1, 7.1-RELEASE-p2)
2009-01-13 21:19:27 UTC (RELENG_7_0, 7.0-RELEASE-p9)
2009-01-13 21:19:27 UTC (RELENG_6, 6.4-STABLE)
2009-01-13 21:19:27 UTC (RELENG_6_4, 6.4-RELEASE-p3)
2009-01-13 21:19:27 UTC (RELENG_6_3, 6.3-RELEASE-p9)
CVE Name: CVE-2009-0021
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 daemon is an implementation of the Network Time Protocol
(NTP) used to synchronize the time of a computer system to a reference
time source.
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
The EVP_VerifyFinal() function from OpenSSL is used to determine if a
digital signature is valid. When ntpd(8) is set to cryptographically
authenticate NTP data it incorrectly checks the return value from
EVP_VerifyFinal().
III. Impact
An attacker which can send NTP packets to ntpd, which uses
cryptographic authentication of NTP data, may be able to inject
malicious time data causing the system clock to be set incorrectly.
IV. Workaround
Use IP based restrictions in ntpd itself or in IP firewalls to
restrict which systems can send NTP packets to ntpd.
NOTE WELL: If ntpd is not explicitly set to use cryptographic
authentication of NTP data the setup is not vulnerable to the issue
as described in this Security Advisory.
V. Solution
NOTE WELL: Due to an error in building the updates, this fix is not
available via freebsd-update at the time of this advisory. We expect
that this will be fixed within the next 48 hours.
Perform one of the following:
1) Upgrade your vulnerable system to 6-STABLE, or 7-STABLE, or to the
RELENG_7_1, RELENG_7_0, 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,
7.0, and 7.1 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
[FreeBSD 6.4 and 7.1]
# fetch http://security.FreeBSD.org/patches/SA-09:03/ntpd.patch
# fetch http://security.FreeBSD.org/patches/SA-09:03/ntpd.patch.asc
[FreeBSD 6.3 and 7.0]
# fetch http://security.FreeBSD.org/patches/SA-09:03/ntpd63.patch
# fetch http://security.FreeBSD.org/patches/SA-09:03/ntpd63.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
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RELENG_6
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.8.2
RELENG_6_4
src/UPDATING 1.416.2.40.2.6
src/sys/conf/newvers.sh 1.69.2.18.2.9
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.8.1.2.1
RELENG_6_3
src/UPDATING 1.416.2.37.2.14
src/sys/conf/newvers.sh 1.69.2.15.2.13
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.20.1
RELENG_7
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.18.2
RELENG_7_1
src/UPDATING 1.507.2.13.2.5
src/sys/conf/newvers.sh 1.72.2.9.2.6
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.18.1.2.1
RELENG_7_0
src/UPDATING 1.507.2.3.2.13
src/sys/conf/newvers.sh 1.72.2.5.2.13
src/contrib/ntp/ntpd/ntp_crypto.c 1.1.1.3.22.1
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Subversion:
Branch/path Revision
- - -------------------------------------------------------------------------
stable/6/ r187194
releng/6.4/ r187194
releng/6.3/ r187194
stable/7/ r187194
releng/7.1/ r187194
releng/7.0/ r187194
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VII. References
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-0021
http://security.FreeBSD.org/advisories/FreeBSD-SA-09:02.openssl.asc
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-09:03.ntpd.asc
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