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FreeBSD Security Advisory FreeBSD-SA-01:31.ntpd


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Date: Thu, 12 Apr 2001 13:58:18 -0700
From: FreeBSD Security Advisories <security-advisories@FreeBSD.org.>
To: [email protected]
Subject: FreeBSD Security Advisory FreeBSD-SA-01:31.ntpd

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FreeBSD-SA-01:31 Security Advisory FreeBSD, Inc. Topic: ntpd contains potential remote compromise Category: core/ports Module: ntpd Announced: 2001-04-06 Credits: Przemyslaw Frasunek <venglin@FREEBSD.LUBLIN.PL.> Affects: FreeBSD 3.x (all releases), FreeBSD 4.x (all releases), FreeBSD 3.5-STABLE and 4.2-STABLE prior to the correction date. Ports collection prior to the correction date. Corrected: 2001-04-06 (FreeBSD 4.2-STABLE, 3.5-STABLE, and ports) Vendor status: Vendor notified. FreeBSD only: NO 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. Older versions of ntpd, such as those in FreeBSD 3.x, were named xntpd. II. Problem Description An overflowable buffer exists in the ntpd daemon related to the building of a response for a query with a large readvar argument. Due to insufficient bounds checking, a remote attacker may be able to cause arbitrary code to be executed as the user running the ntpd daemon, usually root. All versions of FreeBSD prior to the correction date, including FreeBSD 3.5.1 and 4.2, and versions of the ntpd port prior to ntp-4.0.99k_2 contain this problem. The base system and ports collections that will ship with FreeBSD 4.3 do not contain this problem since it was corrected before the release. III. Impact Malicious remote users may be able to execute arbitrary code on an ntpd server as the user running the ntpd daemon, usually root. The ntpd daemon is not enabled by default. If you have not enabled ntpd, your system is not vulnerable. IV. Workaround Disable the ntpd daemon using the following command: # kill -KILL `cat /var/run/ntpd.pid` Additionally, the ntpd daemon should be disabled in the system's startup configuration file /etc/rc.conf, normally accomplished by changing "xntpd_enable=YES" to "xntpd_enable=NO". Since NTP is a stateless UDP-based protocol, source addresses can be spoofed rendering firewalling ineffective for stopping this vulnerability. V. Solution [Base system] One of the following: 1) Upgrade to FreeBSD 4.2-STABLE or 3.5.1-STABLE after the correction date. 2) Download the patch and detached PGP signature from the following location: The following patch applies to FreeBSD 4.x. # fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:31/ntpd-4.x.patch # fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:31/ntpd-4.x.patch.asc The folllowing patch applies to FreeBSD 3.x. # fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:31/ntpd-3.x.patch # fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:31/ntpd-3.x.patch.asc Verify the detached signature using your PGP utility. Issue the following commands as root: [FreeBSD 4.x] # cd /usr/src # patch -p < /path/to/patch # cd /usr/src/usr.sbin/ntp # make all install [FreeBSD 3.x] # cd /usr/src # patch -p < /path/to/patch # cd /usr/src/usr.sbin/xntpd # make all install Finally, if ntpd is already running then kill and restart the ntpd daemon: perform the following command as root: # kill -KILL `cat /var/run/ntpd.pid` && /usr/sbin/ntpd [Ports collection] Use one of the following options to upgrade the ntpd software, then kill and restart the ntpd daemon if it is already running. To kill and restart the ntpd daemon, perform the following command as root: # kill -KILL `cat /var/run/ntpd.pid` && /usr/local/sbin/ntpd 1) Upgrade your entire ports collection and rebuild the ntpd port. 2) Deinstall the old package and install a new package dated after the correction date, obtained from: [i386] ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/net/ntp-4.0.99k_2.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/net/ntp-4.0.99k_2.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/net/ntp-4.0.99k_2.tgz NOTE: It may be several days before updated packages are available. [alpha] Packages are not automatically generated for the alpha architecture at this time due to lack of build resources. 3) download a new port skeleton for the ntpd port from: http://www.freebsd.org/ports/ and use it to rebuild the port. 4) Use the portcheckout utility to automate option (3) above. The portcheckout port is available in /usr/ports/devel/portcheckout or the package can be obtained from: ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/devel/portcheckout-2.0.tgz -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.4 (FreeBSD) Comment: FreeBSD: The Power To Serve iQCVAwUBOs5Oi1UuHi5z0oilAQGb+QP+MqTyEGJBziGnw2gHwAnK3lAaMFyKurBc cgpm61uWpOBsTnJGJ9t5uI3IGPjxsjjmyZR2ONYMIUCRC2b6MA21oEsenD3F8Jeu UphzKdv9IswnSkZFRI5v0PoFtUOKihDU1SLfp2DKjJel8HralhYuDiCOQ/pIpGCj emIKnwcGVu4= =FTKv -----END PGP SIGNATURE-----

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